blob: d2db7dfe232b3ecd299187ed477ad2fd7a0fd1a5 [file] [log] [blame]
Thomas Gleixner59bd9de2019-05-28 10:10:12 -07001// SPDX-License-Identifier: GPL-2.0-only
Linus Torvalds1da177e2005-04-16 15:20:36 -07002/*
3 * linux/fs/namespace.c
4 *
5 * (C) Copyright Al Viro 2000, 2001
Linus Torvalds1da177e2005-04-16 15:20:36 -07006 *
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
8 * Heavily rewritten.
9 */
10
Linus Torvalds1da177e2005-04-16 15:20:36 -070011#include <linux/syscalls.h>
Al Virod10577a2011-12-07 13:06:11 -050012#include <linux/export.h>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080013#include <linux/capability.h>
Kirill Korotaev6b3286e2006-12-08 02:37:56 -080014#include <linux/mnt_namespace.h>
Eric W. Biederman771b1372012-07-26 21:08:32 -070015#include <linux/user_namespace.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070016#include <linux/namei.h>
17#include <linux/security.h>
Ingo Molnar5b825c32017-02-02 17:54:15 +010018#include <linux/cred.h>
Miklos Szeredi73cd49e2008-03-26 22:11:34 +010019#include <linux/idr.h>
Rob Landley57f150a2013-09-11 14:26:10 -070020#include <linux/init.h> /* init_rootfs */
Al Virod10577a2011-12-07 13:06:11 -050021#include <linux/fs_struct.h> /* get_fs_root et.al. */
22#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
Al Viroa07b2002018-11-05 17:40:30 +000023#include <linux/file.h>
Al Virod10577a2011-12-07 13:06:11 -050024#include <linux/uaccess.h>
David Howells0bb80f22013-04-12 01:50:06 +010025#include <linux/proc_ns.h>
Linus Torvalds20b4fb42013-05-01 17:51:54 -070026#include <linux/magic.h>
Mike Rapoport57c8a662018-10-30 15:09:49 -070027#include <linux/memblock.h>
Al Viro9ea459e12014-08-08 13:08:20 -040028#include <linux/task_work.h>
Ingo Molnar9164bb42017-02-04 01:20:53 +010029#include <linux/sched/task.h>
David Howellse262e32d2018-11-01 23:07:23 +000030#include <uapi/linux/mount.h>
David Howells9bc61ab2018-11-04 03:19:03 -050031#include <linux/fs_context.h>
Al Viro037f11b2019-06-01 18:09:44 -040032#include <linux/shmem_fs.h>
Ingo Molnar9164bb42017-02-04 01:20:53 +010033
Ram Pai07b20882005-11-07 17:19:07 -050034#include "pnode.h"
Adrian Bunk948730b2007-07-15 23:41:25 -070035#include "internal.h"
Linus Torvalds1da177e2005-04-16 15:20:36 -070036
Eric W. Biedermand2921682016-09-28 00:27:17 -050037/* Maximum number of mounts in a mount namespace */
38unsigned int sysctl_mount_max __read_mostly = 100000;
39
Al Viro0818bf22014-02-28 13:46:44 -050040static unsigned int m_hash_mask __read_mostly;
41static unsigned int m_hash_shift __read_mostly;
42static unsigned int mp_hash_mask __read_mostly;
43static unsigned int mp_hash_shift __read_mostly;
44
45static __initdata unsigned long mhash_entries;
46static int __init set_mhash_entries(char *str)
47{
48 if (!str)
49 return 0;
50 mhash_entries = simple_strtoul(str, &str, 0);
51 return 1;
52}
53__setup("mhash_entries=", set_mhash_entries);
54
55static __initdata unsigned long mphash_entries;
56static int __init set_mphash_entries(char *str)
57{
58 if (!str)
59 return 0;
60 mphash_entries = simple_strtoul(str, &str, 0);
61 return 1;
62}
63__setup("mphash_entries=", set_mphash_entries);
Eric Dumazet13f14b42008-02-06 01:37:57 -080064
Al Viroc7999c32014-02-27 14:40:10 -050065static u64 event;
Miklos Szeredi73cd49e2008-03-26 22:11:34 +010066static DEFINE_IDA(mnt_id_ida);
Miklos Szeredi719f5d72008-03-27 13:06:23 +010067static DEFINE_IDA(mnt_group_ida);
Linus Torvalds1da177e2005-04-16 15:20:36 -070068
Al Viro38129a12014-03-20 21:10:51 -040069static struct hlist_head *mount_hashtable __read_mostly;
Al Viro0818bf22014-02-28 13:46:44 -050070static struct hlist_head *mountpoint_hashtable __read_mostly;
Christoph Lametere18b8902006-12-06 20:33:20 -080071static struct kmem_cache *mnt_cache __read_mostly;
Al Viro59aa0da2013-09-16 21:34:53 -040072static DECLARE_RWSEM(namespace_sem);
Al Viro4edbe132019-06-30 10:39:08 -040073static HLIST_HEAD(unmounted); /* protected by namespace_sem */
74static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
Linus Torvalds1da177e2005-04-16 15:20:36 -070075
Miklos Szeredif87fd4c2006-01-16 22:14:23 -080076/* /sys/fs */
Greg Kroah-Hartman00d26662007-10-29 14:17:23 -060077struct kobject *fs_kobj;
78EXPORT_SYMBOL_GPL(fs_kobj);
Miklos Szeredif87fd4c2006-01-16 22:14:23 -080079
Nick Piggin99b7db72010-08-18 04:37:39 +100080/*
81 * vfsmount lock may be taken for read to prevent changes to the
82 * vfsmount hash, ie. during mountpoint lookups or walking back
83 * up the tree.
84 *
85 * It should be taken for write in all cases where the vfsmount
86 * tree or hash is modified or when a vfsmount structure is modified.
87 */
Al Viro48a066e2013-09-29 22:06:07 -040088__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
Nick Piggin99b7db72010-08-18 04:37:39 +100089
Al Viro38129a12014-03-20 21:10:51 -040090static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -070091{
Ram Paib58fed82005-11-07 17:16:09 -050092 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
93 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
Al Viro0818bf22014-02-28 13:46:44 -050094 tmp = tmp + (tmp >> m_hash_shift);
95 return &mount_hashtable[tmp & m_hash_mask];
96}
97
98static inline struct hlist_head *mp_hash(struct dentry *dentry)
99{
100 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
101 tmp = tmp + (tmp >> mp_hash_shift);
102 return &mountpoint_hashtable[tmp & mp_hash_mask];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103}
104
Al Virob105e272011-11-24 20:38:33 -0500105static int mnt_alloc_id(struct mount *mnt)
Miklos Szeredi73cd49e2008-03-26 22:11:34 +0100106{
Matthew Wilcox169b4802018-06-11 12:31:36 -0400107 int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
Miklos Szeredi73cd49e2008-03-26 22:11:34 +0100108
Matthew Wilcox169b4802018-06-11 12:31:36 -0400109 if (res < 0)
110 return res;
111 mnt->mnt_id = res;
112 return 0;
Miklos Szeredi73cd49e2008-03-26 22:11:34 +0100113}
114
Al Virob105e272011-11-24 20:38:33 -0500115static void mnt_free_id(struct mount *mnt)
Miklos Szeredi73cd49e2008-03-26 22:11:34 +0100116{
Matthew Wilcox169b4802018-06-11 12:31:36 -0400117 ida_free(&mnt_id_ida, mnt->mnt_id);
Miklos Szeredi73cd49e2008-03-26 22:11:34 +0100118}
119
Miklos Szeredi719f5d72008-03-27 13:06:23 +0100120/*
121 * Allocate a new peer group ID
Miklos Szeredi719f5d72008-03-27 13:06:23 +0100122 */
Al Viro4b8b21f2011-11-24 19:54:23 -0500123static int mnt_alloc_group_id(struct mount *mnt)
Miklos Szeredi719f5d72008-03-27 13:06:23 +0100124{
Matthew Wilcox169b4802018-06-11 12:31:36 -0400125 int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL);
Al Virof21f6222009-06-24 03:12:00 -0400126
Matthew Wilcox169b4802018-06-11 12:31:36 -0400127 if (res < 0)
128 return res;
129 mnt->mnt_group_id = res;
130 return 0;
Miklos Szeredi719f5d72008-03-27 13:06:23 +0100131}
132
133/*
134 * Release a peer group ID
135 */
Al Viro4b8b21f2011-11-24 19:54:23 -0500136void mnt_release_group_id(struct mount *mnt)
Miklos Szeredi719f5d72008-03-27 13:06:23 +0100137{
Matthew Wilcox169b4802018-06-11 12:31:36 -0400138 ida_free(&mnt_group_ida, mnt->mnt_group_id);
Al Viro15169fe2011-11-25 00:50:41 -0500139 mnt->mnt_group_id = 0;
Miklos Szeredi719f5d72008-03-27 13:06:23 +0100140}
141
Nick Pigginb3e19d92011-01-07 17:50:11 +1100142/*
143 * vfsmount lock must be held for read
144 */
Al Viro83adc752011-11-24 22:37:54 -0500145static inline void mnt_add_count(struct mount *mnt, int n)
Nick Pigginb3e19d92011-01-07 17:50:11 +1100146{
147#ifdef CONFIG_SMP
Al Viro68e8a9f2011-11-24 22:53:09 -0500148 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
Nick Pigginb3e19d92011-01-07 17:50:11 +1100149#else
150 preempt_disable();
Al Viro68e8a9f2011-11-24 22:53:09 -0500151 mnt->mnt_count += n;
Nick Pigginb3e19d92011-01-07 17:50:11 +1100152 preempt_enable();
153#endif
154}
155
Nick Pigginb3e19d92011-01-07 17:50:11 +1100156/*
157 * vfsmount lock must be held for write
158 */
Eric Biggersedf7ddb2020-10-31 21:40:21 -0700159int mnt_get_count(struct mount *mnt)
Nick Pigginb3e19d92011-01-07 17:50:11 +1100160{
161#ifdef CONFIG_SMP
Eric Biggersedf7ddb2020-10-31 21:40:21 -0700162 int count = 0;
Nick Pigginb3e19d92011-01-07 17:50:11 +1100163 int cpu;
164
165 for_each_possible_cpu(cpu) {
Al Viro68e8a9f2011-11-24 22:53:09 -0500166 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
Nick Pigginb3e19d92011-01-07 17:50:11 +1100167 }
168
169 return count;
170#else
Al Viro68e8a9f2011-11-24 22:53:09 -0500171 return mnt->mnt_count;
Nick Pigginb3e19d92011-01-07 17:50:11 +1100172#endif
173}
174
Al Virob105e272011-11-24 20:38:33 -0500175static struct mount *alloc_vfsmnt(const char *name)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700176{
Al Viroc63181e2011-11-25 02:35:16 -0500177 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
178 if (mnt) {
Miklos Szeredi73cd49e2008-03-26 22:11:34 +0100179 int err;
180
Al Viroc63181e2011-11-25 02:35:16 -0500181 err = mnt_alloc_id(mnt);
Li Zefan88b38782008-07-21 18:06:36 +0800182 if (err)
183 goto out_free_cache;
184
185 if (name) {
Andrzej Hajdafcc139a2015-02-13 14:36:41 -0800186 mnt->mnt_devname = kstrdup_const(name, GFP_KERNEL);
Al Viroc63181e2011-11-25 02:35:16 -0500187 if (!mnt->mnt_devname)
Li Zefan88b38782008-07-21 18:06:36 +0800188 goto out_free_id;
Miklos Szeredi73cd49e2008-03-26 22:11:34 +0100189 }
190
Nick Pigginb3e19d92011-01-07 17:50:11 +1100191#ifdef CONFIG_SMP
Al Viroc63181e2011-11-25 02:35:16 -0500192 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
193 if (!mnt->mnt_pcp)
Nick Pigginb3e19d92011-01-07 17:50:11 +1100194 goto out_free_devname;
195
Al Viroc63181e2011-11-25 02:35:16 -0500196 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
Nick Pigginb3e19d92011-01-07 17:50:11 +1100197#else
Al Viroc63181e2011-11-25 02:35:16 -0500198 mnt->mnt_count = 1;
199 mnt->mnt_writers = 0;
Nick Pigginb3e19d92011-01-07 17:50:11 +1100200#endif
201
Al Viro38129a12014-03-20 21:10:51 -0400202 INIT_HLIST_NODE(&mnt->mnt_hash);
Al Viroc63181e2011-11-25 02:35:16 -0500203 INIT_LIST_HEAD(&mnt->mnt_child);
204 INIT_LIST_HEAD(&mnt->mnt_mounts);
205 INIT_LIST_HEAD(&mnt->mnt_list);
206 INIT_LIST_HEAD(&mnt->mnt_expire);
207 INIT_LIST_HEAD(&mnt->mnt_share);
208 INIT_LIST_HEAD(&mnt->mnt_slave_list);
209 INIT_LIST_HEAD(&mnt->mnt_slave);
Eric W. Biederman0a5eb7c2013-09-22 19:37:01 -0700210 INIT_HLIST_NODE(&mnt->mnt_mp_list);
Eric W. Biederman99b19d12016-10-24 16:16:13 -0500211 INIT_LIST_HEAD(&mnt->mnt_umounting);
Al Viro56cbb422019-07-04 16:57:51 -0400212 INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213 }
Al Viroc63181e2011-11-25 02:35:16 -0500214 return mnt;
Li Zefan88b38782008-07-21 18:06:36 +0800215
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000216#ifdef CONFIG_SMP
217out_free_devname:
Andrzej Hajdafcc139a2015-02-13 14:36:41 -0800218 kfree_const(mnt->mnt_devname);
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000219#endif
Li Zefan88b38782008-07-21 18:06:36 +0800220out_free_id:
Al Viroc63181e2011-11-25 02:35:16 -0500221 mnt_free_id(mnt);
Li Zefan88b38782008-07-21 18:06:36 +0800222out_free_cache:
Al Viroc63181e2011-11-25 02:35:16 -0500223 kmem_cache_free(mnt_cache, mnt);
Li Zefan88b38782008-07-21 18:06:36 +0800224 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225}
226
Dave Hansen83660252008-02-15 14:37:30 -0800227/*
228 * Most r/o checks on a fs are for operations that take
229 * discrete amounts of time, like a write() or unlink().
230 * We must keep track of when those operations start
231 * (for permission checks) and when they end, so that
232 * we can determine when writes are able to occur to
233 * a filesystem.
234 */
Dave Hansen3d733632008-02-15 14:37:59 -0800235/*
236 * __mnt_is_readonly: check whether a mount is read-only
237 * @mnt: the mount to check for its write status
238 *
239 * This shouldn't be used directly ouside of the VFS.
240 * It does not guarantee that the filesystem will stay
241 * r/w, just that it is right *now*. This can not and
242 * should not be used in place of IS_RDONLY(inode).
243 * mnt_want/drop_write() will _keep_ the filesystem
244 * r/w.
245 */
David Howells43f5e652018-11-01 23:07:25 +0000246bool __mnt_is_readonly(struct vfsmount *mnt)
Dave Hansen3d733632008-02-15 14:37:59 -0800247{
David Howells43f5e652018-11-01 23:07:25 +0000248 return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb);
Dave Hansen3d733632008-02-15 14:37:59 -0800249}
250EXPORT_SYMBOL_GPL(__mnt_is_readonly);
251
Al Viro83adc752011-11-24 22:37:54 -0500252static inline void mnt_inc_writers(struct mount *mnt)
Dave Hansen3d733632008-02-15 14:37:59 -0800253{
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000254#ifdef CONFIG_SMP
Al Viro68e8a9f2011-11-24 22:53:09 -0500255 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000256#else
Al Viro68e8a9f2011-11-24 22:53:09 -0500257 mnt->mnt_writers++;
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000258#endif
Dave Hansen3d733632008-02-15 14:37:59 -0800259}
Dave Hansen3d733632008-02-15 14:37:59 -0800260
Al Viro83adc752011-11-24 22:37:54 -0500261static inline void mnt_dec_writers(struct mount *mnt)
Dave Hansen3d733632008-02-15 14:37:59 -0800262{
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000263#ifdef CONFIG_SMP
Al Viro68e8a9f2011-11-24 22:53:09 -0500264 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000265#else
Al Viro68e8a9f2011-11-24 22:53:09 -0500266 mnt->mnt_writers--;
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000267#endif
268}
269
Al Viro83adc752011-11-24 22:37:54 -0500270static unsigned int mnt_get_writers(struct mount *mnt)
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000271{
272#ifdef CONFIG_SMP
273 unsigned int count = 0;
Dave Hansen3d733632008-02-15 14:37:59 -0800274 int cpu;
Dave Hansen3d733632008-02-15 14:37:59 -0800275
276 for_each_possible_cpu(cpu) {
Al Viro68e8a9f2011-11-24 22:53:09 -0500277 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
Dave Hansen3d733632008-02-15 14:37:59 -0800278 }
Dave Hansen3d733632008-02-15 14:37:59 -0800279
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000280 return count;
281#else
282 return mnt->mnt_writers;
283#endif
Dave Hansen3d733632008-02-15 14:37:59 -0800284}
285
Miklos Szeredi4ed5e82f2011-11-21 12:11:31 +0100286static int mnt_is_readonly(struct vfsmount *mnt)
287{
288 if (mnt->mnt_sb->s_readonly_remount)
289 return 1;
290 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
291 smp_rmb();
292 return __mnt_is_readonly(mnt);
293}
294
Dave Hansen3d733632008-02-15 14:37:59 -0800295/*
Jan Karaeb04c282012-06-12 16:20:35 +0200296 * Most r/o & frozen checks on a fs are for operations that take discrete
297 * amounts of time, like a write() or unlink(). We must keep track of when
298 * those operations start (for permission checks) and when they end, so that we
299 * can determine when writes are able to occur to a filesystem.
Dave Hansen3d733632008-02-15 14:37:59 -0800300 */
Dave Hansen83660252008-02-15 14:37:30 -0800301/**
Jan Karaeb04c282012-06-12 16:20:35 +0200302 * __mnt_want_write - get write access to a mount without freeze protection
Al Viro83adc752011-11-24 22:37:54 -0500303 * @m: the mount on which to take a write
Dave Hansen83660252008-02-15 14:37:30 -0800304 *
Jan Karaeb04c282012-06-12 16:20:35 +0200305 * This tells the low-level filesystem that a write is about to be performed to
306 * it, and makes sure that writes are allowed (mnt it read-write) before
307 * returning success. This operation does not protect against filesystem being
308 * frozen. When the write operation is finished, __mnt_drop_write() must be
309 * called. This is effectively a refcount.
Dave Hansen83660252008-02-15 14:37:30 -0800310 */
Jan Karaeb04c282012-06-12 16:20:35 +0200311int __mnt_want_write(struct vfsmount *m)
Dave Hansen83660252008-02-15 14:37:30 -0800312{
Al Viro83adc752011-11-24 22:37:54 -0500313 struct mount *mnt = real_mount(m);
Dave Hansen3d733632008-02-15 14:37:59 -0800314 int ret = 0;
Dave Hansen3d733632008-02-15 14:37:59 -0800315
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000316 preempt_disable();
Nick Pigginc6653a82011-01-07 17:50:10 +1100317 mnt_inc_writers(mnt);
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000318 /*
Nick Pigginc6653a82011-01-07 17:50:10 +1100319 * The store to mnt_inc_writers must be visible before we pass
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000320 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
321 * incremented count after it has set MNT_WRITE_HOLD.
322 */
323 smp_mb();
Mark Rutland6aa7de02017-10-23 14:07:29 -0700324 while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000325 cpu_relax();
326 /*
327 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
328 * be set to match its requirements. So we must not load that until
329 * MNT_WRITE_HOLD is cleared.
330 */
331 smp_rmb();
Miklos Szeredi4ed5e82f2011-11-21 12:11:31 +0100332 if (mnt_is_readonly(m)) {
Nick Pigginc6653a82011-01-07 17:50:10 +1100333 mnt_dec_writers(mnt);
Dave Hansen3d733632008-02-15 14:37:59 -0800334 ret = -EROFS;
Dave Hansen3d733632008-02-15 14:37:59 -0800335 }
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000336 preempt_enable();
Jan Karaeb04c282012-06-12 16:20:35 +0200337
338 return ret;
339}
340
341/**
342 * mnt_want_write - get write access to a mount
343 * @m: the mount on which to take a write
344 *
345 * This tells the low-level filesystem that a write is about to be performed to
346 * it, and makes sure that writes are allowed (mount is read-write, filesystem
347 * is not frozen) before returning success. When the write operation is
348 * finished, mnt_drop_write() must be called. This is effectively a refcount.
349 */
350int mnt_want_write(struct vfsmount *m)
351{
352 int ret;
353
354 sb_start_write(m->mnt_sb);
355 ret = __mnt_want_write(m);
356 if (ret)
357 sb_end_write(m->mnt_sb);
Dave Hansen3d733632008-02-15 14:37:59 -0800358 return ret;
Dave Hansen83660252008-02-15 14:37:30 -0800359}
360EXPORT_SYMBOL_GPL(mnt_want_write);
361
362/**
npiggin@suse.de96029c42009-04-26 20:25:55 +1000363 * mnt_clone_write - get write access to a mount
364 * @mnt: the mount on which to take a write
365 *
366 * This is effectively like mnt_want_write, except
367 * it must only be used to take an extra write reference
368 * on a mountpoint that we already know has a write reference
369 * on it. This allows some optimisation.
370 *
371 * After finished, mnt_drop_write must be called as usual to
372 * drop the reference.
373 */
374int mnt_clone_write(struct vfsmount *mnt)
375{
376 /* superblock may be r/o */
377 if (__mnt_is_readonly(mnt))
378 return -EROFS;
379 preempt_disable();
Al Viro83adc752011-11-24 22:37:54 -0500380 mnt_inc_writers(real_mount(mnt));
npiggin@suse.de96029c42009-04-26 20:25:55 +1000381 preempt_enable();
382 return 0;
383}
384EXPORT_SYMBOL_GPL(mnt_clone_write);
385
386/**
Jan Karaeb04c282012-06-12 16:20:35 +0200387 * __mnt_want_write_file - get write access to a file's mount
388 * @file: the file who's mount on which to take a write
389 *
390 * This is like __mnt_want_write, but it takes a file and can
391 * do some optimisations if the file is open for write already
392 */
393int __mnt_want_write_file(struct file *file)
394{
Al Viro83f936c2014-03-14 12:02:47 -0400395 if (!(file->f_mode & FMODE_WRITER))
Jan Karaeb04c282012-06-12 16:20:35 +0200396 return __mnt_want_write(file->f_path.mnt);
397 else
398 return mnt_clone_write(file->f_path.mnt);
399}
400
401/**
Miklos Szeredi7c6893e2017-09-05 12:53:12 +0200402 * mnt_want_write_file - get write access to a file's mount
403 * @file: the file who's mount on which to take a write
404 *
405 * This is like mnt_want_write, but it takes a file and can
406 * do some optimisations if the file is open for write already
Miklos Szeredi7c6893e2017-09-05 12:53:12 +0200407 */
408int mnt_want_write_file(struct file *file)
409{
410 int ret;
411
Miklos Szeredia6795a52018-07-18 15:44:43 +0200412 sb_start_write(file_inode(file)->i_sb);
Jan Karaeb04c282012-06-12 16:20:35 +0200413 ret = __mnt_want_write_file(file);
414 if (ret)
Miklos Szeredia6795a52018-07-18 15:44:43 +0200415 sb_end_write(file_inode(file)->i_sb);
Miklos Szeredi7c6893e2017-09-05 12:53:12 +0200416 return ret;
417}
npiggin@suse.de96029c42009-04-26 20:25:55 +1000418EXPORT_SYMBOL_GPL(mnt_want_write_file);
419
420/**
Jan Karaeb04c282012-06-12 16:20:35 +0200421 * __mnt_drop_write - give up write access to a mount
Dave Hansen83660252008-02-15 14:37:30 -0800422 * @mnt: the mount on which to give up write access
423 *
424 * Tells the low-level filesystem that we are done
425 * performing writes to it. Must be matched with
Jan Karaeb04c282012-06-12 16:20:35 +0200426 * __mnt_want_write() call above.
Dave Hansen83660252008-02-15 14:37:30 -0800427 */
Jan Karaeb04c282012-06-12 16:20:35 +0200428void __mnt_drop_write(struct vfsmount *mnt)
Dave Hansen83660252008-02-15 14:37:30 -0800429{
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000430 preempt_disable();
Al Viro83adc752011-11-24 22:37:54 -0500431 mnt_dec_writers(real_mount(mnt));
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000432 preempt_enable();
Dave Hansen83660252008-02-15 14:37:30 -0800433}
Jan Karaeb04c282012-06-12 16:20:35 +0200434
435/**
436 * mnt_drop_write - give up write access to a mount
437 * @mnt: the mount on which to give up write access
438 *
439 * Tells the low-level filesystem that we are done performing writes to it and
440 * also allows filesystem to be frozen again. Must be matched with
441 * mnt_want_write() call above.
442 */
443void mnt_drop_write(struct vfsmount *mnt)
444{
445 __mnt_drop_write(mnt);
446 sb_end_write(mnt->mnt_sb);
447}
Dave Hansen83660252008-02-15 14:37:30 -0800448EXPORT_SYMBOL_GPL(mnt_drop_write);
449
Jan Karaeb04c282012-06-12 16:20:35 +0200450void __mnt_drop_write_file(struct file *file)
451{
452 __mnt_drop_write(file->f_path.mnt);
453}
454
Miklos Szeredi7c6893e2017-09-05 12:53:12 +0200455void mnt_drop_write_file(struct file *file)
456{
Miklos Szeredia6795a52018-07-18 15:44:43 +0200457 __mnt_drop_write_file(file);
Miklos Szeredi7c6893e2017-09-05 12:53:12 +0200458 sb_end_write(file_inode(file)->i_sb);
459}
Al Viro2a79f172011-12-09 08:06:57 -0500460EXPORT_SYMBOL(mnt_drop_write_file);
461
Al Viro83adc752011-11-24 22:37:54 -0500462static int mnt_make_readonly(struct mount *mnt)
Dave Hansen83660252008-02-15 14:37:30 -0800463{
Dave Hansen3d733632008-02-15 14:37:59 -0800464 int ret = 0;
465
Al Viro719ea2f2013-09-29 11:24:49 -0400466 lock_mount_hash();
Al Viro83adc752011-11-24 22:37:54 -0500467 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000468 /*
469 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
470 * should be visible before we do.
471 */
472 smp_mb();
473
474 /*
475 * With writers on hold, if this value is zero, then there are
476 * definitely no active writers (although held writers may subsequently
477 * increment the count, they'll have to wait, and decrement it after
478 * seeing MNT_READONLY).
479 *
480 * It is OK to have counter incremented on one CPU and decremented on
481 * another: the sum will add up correctly. The danger would be when we
482 * sum up each counter, if we read a counter before it is incremented,
483 * but then read another CPU's count which it has been subsequently
484 * decremented from -- we would see more decrements than we should.
485 * MNT_WRITE_HOLD protects against this scenario, because
486 * mnt_want_write first increments count, then smp_mb, then spins on
487 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
488 * we're counting up here.
489 */
Nick Pigginc6653a82011-01-07 17:50:10 +1100490 if (mnt_get_writers(mnt) > 0)
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000491 ret = -EBUSY;
492 else
Al Viro83adc752011-11-24 22:37:54 -0500493 mnt->mnt.mnt_flags |= MNT_READONLY;
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000494 /*
495 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
496 * that become unheld will see MNT_READONLY.
497 */
498 smp_wmb();
Al Viro83adc752011-11-24 22:37:54 -0500499 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
Al Viro719ea2f2013-09-29 11:24:49 -0400500 unlock_mount_hash();
Dave Hansen3d733632008-02-15 14:37:59 -0800501 return ret;
Dave Hansen83660252008-02-15 14:37:30 -0800502}
Dave Hansen83660252008-02-15 14:37:30 -0800503
David Howells43f5e652018-11-01 23:07:25 +0000504static int __mnt_unmake_readonly(struct mount *mnt)
Dave Hansen2e4b7fc2008-02-15 14:38:00 -0800505{
Al Viro719ea2f2013-09-29 11:24:49 -0400506 lock_mount_hash();
Al Viro83adc752011-11-24 22:37:54 -0500507 mnt->mnt.mnt_flags &= ~MNT_READONLY;
Al Viro719ea2f2013-09-29 11:24:49 -0400508 unlock_mount_hash();
David Howells43f5e652018-11-01 23:07:25 +0000509 return 0;
Dave Hansen2e4b7fc2008-02-15 14:38:00 -0800510}
511
Miklos Szeredi4ed5e82f2011-11-21 12:11:31 +0100512int sb_prepare_remount_readonly(struct super_block *sb)
513{
514 struct mount *mnt;
515 int err = 0;
516
Miklos Szeredi8e8b8792011-11-21 12:11:33 +0100517 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
518 if (atomic_long_read(&sb->s_remove_count))
519 return -EBUSY;
520
Al Viro719ea2f2013-09-29 11:24:49 -0400521 lock_mount_hash();
Miklos Szeredi4ed5e82f2011-11-21 12:11:31 +0100522 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
523 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
524 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
525 smp_mb();
526 if (mnt_get_writers(mnt) > 0) {
527 err = -EBUSY;
528 break;
529 }
530 }
531 }
Miklos Szeredi8e8b8792011-11-21 12:11:33 +0100532 if (!err && atomic_long_read(&sb->s_remove_count))
533 err = -EBUSY;
534
Miklos Szeredi4ed5e82f2011-11-21 12:11:31 +0100535 if (!err) {
536 sb->s_readonly_remount = 1;
537 smp_wmb();
538 }
539 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
540 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
541 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
542 }
Al Viro719ea2f2013-09-29 11:24:49 -0400543 unlock_mount_hash();
Miklos Szeredi4ed5e82f2011-11-21 12:11:31 +0100544
545 return err;
546}
547
Al Virob105e272011-11-24 20:38:33 -0500548static void free_vfsmnt(struct mount *mnt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700549{
Andrzej Hajdafcc139a2015-02-13 14:36:41 -0800550 kfree_const(mnt->mnt_devname);
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000551#ifdef CONFIG_SMP
Al Viro68e8a9f2011-11-24 22:53:09 -0500552 free_percpu(mnt->mnt_pcp);
npiggin@suse.ded3ef3d72009-04-26 20:25:54 +1000553#endif
Al Virob105e272011-11-24 20:38:33 -0500554 kmem_cache_free(mnt_cache, mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555}
556
David Howells8ffcb322014-01-24 12:17:54 +0000557static void delayed_free_vfsmnt(struct rcu_head *head)
558{
559 free_vfsmnt(container_of(head, struct mount, mnt_rcu));
560}
561
Al Viro48a066e2013-09-29 22:06:07 -0400562/* call under rcu_read_lock */
Al Viro294d71f2015-05-08 11:43:53 -0400563int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
Al Viro48a066e2013-09-29 22:06:07 -0400564{
565 struct mount *mnt;
566 if (read_seqretry(&mount_lock, seq))
Al Viro294d71f2015-05-08 11:43:53 -0400567 return 1;
Al Viro48a066e2013-09-29 22:06:07 -0400568 if (bastard == NULL)
Al Viro294d71f2015-05-08 11:43:53 -0400569 return 0;
Al Viro48a066e2013-09-29 22:06:07 -0400570 mnt = real_mount(bastard);
571 mnt_add_count(mnt, 1);
Al Viro119e1ef2018-08-09 17:51:32 -0400572 smp_mb(); // see mntput_no_expire()
Al Viro48a066e2013-09-29 22:06:07 -0400573 if (likely(!read_seqretry(&mount_lock, seq)))
Al Viro294d71f2015-05-08 11:43:53 -0400574 return 0;
Al Viro48a066e2013-09-29 22:06:07 -0400575 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
576 mnt_add_count(mnt, -1);
Al Viro294d71f2015-05-08 11:43:53 -0400577 return 1;
Al Viro48a066e2013-09-29 22:06:07 -0400578 }
Al Viro119e1ef2018-08-09 17:51:32 -0400579 lock_mount_hash();
580 if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
581 mnt_add_count(mnt, -1);
582 unlock_mount_hash();
583 return 1;
584 }
585 unlock_mount_hash();
586 /* caller will mntput() */
Al Viro294d71f2015-05-08 11:43:53 -0400587 return -1;
588}
589
590/* call under rcu_read_lock */
591bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
592{
593 int res = __legitimize_mnt(bastard, seq);
594 if (likely(!res))
595 return true;
596 if (unlikely(res < 0)) {
597 rcu_read_unlock();
598 mntput(bastard);
599 rcu_read_lock();
600 }
Al Viro48a066e2013-09-29 22:06:07 -0400601 return false;
602}
603
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604/*
Al Viro474279d2013-10-01 16:11:26 -0400605 * find the first mount at @dentry on vfsmount @mnt.
Al Viro48a066e2013-09-29 22:06:07 -0400606 * call under rcu_read_lock()
Linus Torvalds1da177e2005-04-16 15:20:36 -0700607 */
Al Viro474279d2013-10-01 16:11:26 -0400608struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700609{
Al Viro38129a12014-03-20 21:10:51 -0400610 struct hlist_head *head = m_hash(mnt, dentry);
Al Viro474279d2013-10-01 16:11:26 -0400611 struct mount *p;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700612
Al Viro38129a12014-03-20 21:10:51 -0400613 hlist_for_each_entry_rcu(p, head, mnt_hash)
Al Viro474279d2013-10-01 16:11:26 -0400614 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
615 return p;
616 return NULL;
617}
618
619/*
David Howellsf015f1262012-06-25 12:55:28 +0100620 * lookup_mnt - Return the first child mount mounted at path
621 *
622 * "First" means first mounted chronologically. If you create the
623 * following mounts:
624 *
625 * mount /dev/sda1 /mnt
626 * mount /dev/sda2 /mnt
627 * mount /dev/sda3 /mnt
628 *
629 * Then lookup_mnt() on the base /mnt dentry in the root mount will
630 * return successively the root dentry and vfsmount of /dev/sda1, then
631 * /dev/sda2, then /dev/sda3, then NULL.
632 *
633 * lookup_mnt takes a reference to the found vfsmount.
Ram Paia05964f2005-11-07 17:20:17 -0500634 */
Al Viroca71cf72016-11-20 19:45:28 -0500635struct vfsmount *lookup_mnt(const struct path *path)
Ram Paia05964f2005-11-07 17:20:17 -0500636{
Al Viroc7105362011-11-24 18:22:03 -0500637 struct mount *child_mnt;
Al Viro48a066e2013-09-29 22:06:07 -0400638 struct vfsmount *m;
639 unsigned seq;
Nick Piggin99b7db72010-08-18 04:37:39 +1000640
Al Viro48a066e2013-09-29 22:06:07 -0400641 rcu_read_lock();
642 do {
643 seq = read_seqbegin(&mount_lock);
644 child_mnt = __lookup_mnt(path->mnt, path->dentry);
645 m = child_mnt ? &child_mnt->mnt : NULL;
646 } while (!legitimize_mnt(m, seq));
647 rcu_read_unlock();
648 return m;
Ram Paia05964f2005-11-07 17:20:17 -0500649}
650
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +0200651static inline void lock_ns_list(struct mnt_namespace *ns)
652{
653 spin_lock(&ns->ns_lock);
654}
655
656static inline void unlock_ns_list(struct mnt_namespace *ns)
657{
658 spin_unlock(&ns->ns_lock);
659}
660
661static inline bool mnt_is_cursor(struct mount *mnt)
662{
663 return mnt->mnt.mnt_flags & MNT_CURSOR;
664}
665
Eric W. Biederman7af13642013-10-04 19:15:13 -0700666/*
667 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
668 * current mount namespace.
669 *
670 * The common case is dentries are not mountpoints at all and that
671 * test is handled inline. For the slow case when we are actually
672 * dealing with a mountpoint of some kind, walk through all of the
673 * mounts in the current mount namespace and test to see if the dentry
674 * is a mountpoint.
675 *
676 * The mount_hashtable is not usable in the context because we
677 * need to identify all mounts that may be in the current mount
678 * namespace not just a mount that happens to have some specified
679 * parent mount.
680 */
681bool __is_local_mountpoint(struct dentry *dentry)
682{
683 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
684 struct mount *mnt;
685 bool is_covered = false;
686
Eric W. Biederman7af13642013-10-04 19:15:13 -0700687 down_read(&namespace_sem);
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +0200688 lock_ns_list(ns);
Eric W. Biederman7af13642013-10-04 19:15:13 -0700689 list_for_each_entry(mnt, &ns->list, mnt_list) {
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +0200690 if (mnt_is_cursor(mnt))
691 continue;
Eric W. Biederman7af13642013-10-04 19:15:13 -0700692 is_covered = (mnt->mnt_mountpoint == dentry);
693 if (is_covered)
694 break;
695 }
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +0200696 unlock_ns_list(ns);
Eric W. Biederman7af13642013-10-04 19:15:13 -0700697 up_read(&namespace_sem);
Nikolay Borisov5ad05cc2020-03-04 18:12:45 +0200698
Eric W. Biederman7af13642013-10-04 19:15:13 -0700699 return is_covered;
700}
701
Eric W. Biedermane2dfa932014-02-24 17:32:34 -0800702static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
Al Viro84d17192013-03-15 10:53:28 -0400703{
Al Viro0818bf22014-02-28 13:46:44 -0500704 struct hlist_head *chain = mp_hash(dentry);
Al Viro84d17192013-03-15 10:53:28 -0400705 struct mountpoint *mp;
706
Al Viro0818bf22014-02-28 13:46:44 -0500707 hlist_for_each_entry(mp, chain, m_hash) {
Al Viro84d17192013-03-15 10:53:28 -0400708 if (mp->m_dentry == dentry) {
Al Viro84d17192013-03-15 10:53:28 -0400709 mp->m_count++;
710 return mp;
711 }
712 }
Eric W. Biedermane2dfa932014-02-24 17:32:34 -0800713 return NULL;
714}
715
Eric W. Biederman3895dbf2017-01-03 14:18:43 +1300716static struct mountpoint *get_mountpoint(struct dentry *dentry)
Eric W. Biedermane2dfa932014-02-24 17:32:34 -0800717{
Eric W. Biederman3895dbf2017-01-03 14:18:43 +1300718 struct mountpoint *mp, *new = NULL;
Eric W. Biedermane2dfa932014-02-24 17:32:34 -0800719 int ret;
Al Viro84d17192013-03-15 10:53:28 -0400720
Eric W. Biederman3895dbf2017-01-03 14:18:43 +1300721 if (d_mountpoint(dentry)) {
Benjamin Coddington1e9c75f2018-10-03 10:18:33 -0400722 /* might be worth a WARN_ON() */
723 if (d_unlinked(dentry))
724 return ERR_PTR(-ENOENT);
Eric W. Biederman3895dbf2017-01-03 14:18:43 +1300725mountpoint:
726 read_seqlock_excl(&mount_lock);
727 mp = lookup_mountpoint(dentry);
728 read_sequnlock_excl(&mount_lock);
729 if (mp)
730 goto done;
Al Viro84d17192013-03-15 10:53:28 -0400731 }
Miklos Szeredieed81002013-09-05 14:39:11 +0200732
Eric W. Biederman3895dbf2017-01-03 14:18:43 +1300733 if (!new)
734 new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
735 if (!new)
736 return ERR_PTR(-ENOMEM);
737
738
739 /* Exactly one processes may set d_mounted */
740 ret = d_set_mounted(dentry);
741
742 /* Someone else set d_mounted? */
743 if (ret == -EBUSY)
744 goto mountpoint;
745
746 /* The dentry is not available as a mountpoint? */
747 mp = ERR_PTR(ret);
748 if (ret)
749 goto done;
750
751 /* Add the new mountpoint to the hash table */
752 read_seqlock_excl(&mount_lock);
Al Viro4edbe132019-06-30 10:39:08 -0400753 new->m_dentry = dget(dentry);
Eric W. Biederman3895dbf2017-01-03 14:18:43 +1300754 new->m_count = 1;
755 hlist_add_head(&new->m_hash, mp_hash(dentry));
756 INIT_HLIST_HEAD(&new->m_list);
757 read_sequnlock_excl(&mount_lock);
758
759 mp = new;
760 new = NULL;
761done:
762 kfree(new);
Al Viro84d17192013-03-15 10:53:28 -0400763 return mp;
764}
765
Al Viro4edbe132019-06-30 10:39:08 -0400766/*
767 * vfsmount lock must be held. Additionally, the caller is responsible
768 * for serializing calls for given disposal list.
769 */
770static void __put_mountpoint(struct mountpoint *mp, struct list_head *list)
Al Viro84d17192013-03-15 10:53:28 -0400771{
772 if (!--mp->m_count) {
773 struct dentry *dentry = mp->m_dentry;
Eric W. Biederman0a5eb7c2013-09-22 19:37:01 -0700774 BUG_ON(!hlist_empty(&mp->m_list));
Al Viro84d17192013-03-15 10:53:28 -0400775 spin_lock(&dentry->d_lock);
776 dentry->d_flags &= ~DCACHE_MOUNTED;
777 spin_unlock(&dentry->d_lock);
Al Viro4edbe132019-06-30 10:39:08 -0400778 dput_to_list(dentry, list);
Al Viro0818bf22014-02-28 13:46:44 -0500779 hlist_del(&mp->m_hash);
Al Viro84d17192013-03-15 10:53:28 -0400780 kfree(mp);
781 }
782}
783
Al Viro4edbe132019-06-30 10:39:08 -0400784/* called with namespace_lock and vfsmount lock */
785static void put_mountpoint(struct mountpoint *mp)
786{
787 __put_mountpoint(mp, &ex_mountpoints);
788}
789
Al Viro143c8c92011-11-25 00:46:35 -0500790static inline int check_mnt(struct mount *mnt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700791{
Kirill Korotaev6b3286e2006-12-08 02:37:56 -0800792 return mnt->mnt_ns == current->nsproxy->mnt_ns;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700793}
794
Nick Piggin99b7db72010-08-18 04:37:39 +1000795/*
796 * vfsmount lock must be held for write
797 */
Kirill Korotaev6b3286e2006-12-08 02:37:56 -0800798static void touch_mnt_namespace(struct mnt_namespace *ns)
Al Viro5addc5d2005-11-07 17:15:49 -0500799{
800 if (ns) {
801 ns->event = ++event;
802 wake_up_interruptible(&ns->poll);
803 }
804}
805
Nick Piggin99b7db72010-08-18 04:37:39 +1000806/*
807 * vfsmount lock must be held for write
808 */
Kirill Korotaev6b3286e2006-12-08 02:37:56 -0800809static void __touch_mnt_namespace(struct mnt_namespace *ns)
Al Viro5addc5d2005-11-07 17:15:49 -0500810{
811 if (ns && ns->event != event) {
812 ns->event = event;
813 wake_up_interruptible(&ns->poll);
814 }
815}
816
Nick Piggin99b7db72010-08-18 04:37:39 +1000817/*
818 * vfsmount lock must be held for write
819 */
Al Viroe4e59902019-06-29 12:58:42 -0400820static struct mountpoint *unhash_mnt(struct mount *mnt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821{
Al Viroe4e59902019-06-29 12:58:42 -0400822 struct mountpoint *mp;
Al Viro0714a532011-11-24 22:19:58 -0500823 mnt->mnt_parent = mnt;
Al Viroa73324d2011-11-24 22:25:07 -0500824 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
Al Viro6b41d532011-11-24 23:24:33 -0500825 list_del_init(&mnt->mnt_child);
Al Viro38129a12014-03-20 21:10:51 -0400826 hlist_del_init_rcu(&mnt->mnt_hash);
Eric W. Biederman0a5eb7c2013-09-22 19:37:01 -0700827 hlist_del_init(&mnt->mnt_mp_list);
Al Viroe4e59902019-06-29 12:58:42 -0400828 mp = mnt->mnt_mp;
Al Viro84d17192013-03-15 10:53:28 -0400829 mnt->mnt_mp = NULL;
Al Viroe4e59902019-06-29 12:58:42 -0400830 return mp;
Eric W. Biederman7bdb11de2014-12-29 13:03:41 -0600831}
832
833/*
834 * vfsmount lock must be held for write
835 */
Eric W. Biederman6a46c572015-01-15 22:58:33 -0600836static void umount_mnt(struct mount *mnt)
837{
Al Viroe4e59902019-06-29 12:58:42 -0400838 put_mountpoint(unhash_mnt(mnt));
Eric W. Biederman6a46c572015-01-15 22:58:33 -0600839}
840
841/*
842 * vfsmount lock must be held for write
843 */
Al Viro84d17192013-03-15 10:53:28 -0400844void mnt_set_mountpoint(struct mount *mnt,
845 struct mountpoint *mp,
Al Viro44d964d62011-11-24 21:28:22 -0500846 struct mount *child_mnt)
Ram Paib90fa9a2005-11-07 17:19:50 -0500847{
Al Viro84d17192013-03-15 10:53:28 -0400848 mp->m_count++;
Al Viro3a2393d2011-11-25 03:19:09 -0500849 mnt_add_count(mnt, 1); /* essentially, that's mntget */
Al Viro4edbe132019-06-30 10:39:08 -0400850 child_mnt->mnt_mountpoint = mp->m_dentry;
Al Viro3a2393d2011-11-25 03:19:09 -0500851 child_mnt->mnt_parent = mnt;
Al Viro84d17192013-03-15 10:53:28 -0400852 child_mnt->mnt_mp = mp;
Eric W. Biederman0a5eb7c2013-09-22 19:37:01 -0700853 hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
Ram Paib90fa9a2005-11-07 17:19:50 -0500854}
855
Eric W. Biederman1064f872017-01-20 18:28:35 +1300856static void __attach_mnt(struct mount *mnt, struct mount *parent)
857{
858 hlist_add_head_rcu(&mnt->mnt_hash,
859 m_hash(&parent->mnt, mnt->mnt_mountpoint));
860 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
861}
862
Nick Piggin99b7db72010-08-18 04:37:39 +1000863/*
864 * vfsmount lock must be held for write
865 */
Al Viro84d17192013-03-15 10:53:28 -0400866static void attach_mnt(struct mount *mnt,
867 struct mount *parent,
868 struct mountpoint *mp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700869{
Al Viro84d17192013-03-15 10:53:28 -0400870 mnt_set_mountpoint(parent, mp, mnt);
Eric W. Biederman1064f872017-01-20 18:28:35 +1300871 __attach_mnt(mnt, parent);
Ram Paib90fa9a2005-11-07 17:19:50 -0500872}
873
Eric W. Biederman1064f872017-01-20 18:28:35 +1300874void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
Al Viro12a5b522014-08-10 03:44:55 -0400875{
Eric W. Biederman1064f872017-01-20 18:28:35 +1300876 struct mountpoint *old_mp = mnt->mnt_mp;
Eric W. Biederman1064f872017-01-20 18:28:35 +1300877 struct mount *old_parent = mnt->mnt_parent;
878
879 list_del_init(&mnt->mnt_child);
880 hlist_del_init(&mnt->mnt_mp_list);
881 hlist_del_init_rcu(&mnt->mnt_hash);
882
883 attach_mnt(mnt, parent, mp);
884
885 put_mountpoint(old_mp);
Eric W. Biederman1064f872017-01-20 18:28:35 +1300886 mnt_add_count(old_parent, -1);
Al Viro12a5b522014-08-10 03:44:55 -0400887}
888
Ram Paib90fa9a2005-11-07 17:19:50 -0500889/*
Nick Piggin99b7db72010-08-18 04:37:39 +1000890 * vfsmount lock must be held for write
Ram Paib90fa9a2005-11-07 17:19:50 -0500891 */
Eric W. Biederman1064f872017-01-20 18:28:35 +1300892static void commit_tree(struct mount *mnt)
Ram Paib90fa9a2005-11-07 17:19:50 -0500893{
Al Viro0714a532011-11-24 22:19:58 -0500894 struct mount *parent = mnt->mnt_parent;
Al Viro83adc752011-11-24 22:37:54 -0500895 struct mount *m;
Ram Paib90fa9a2005-11-07 17:19:50 -0500896 LIST_HEAD(head);
Al Viro143c8c92011-11-25 00:46:35 -0500897 struct mnt_namespace *n = parent->mnt_ns;
Ram Paib90fa9a2005-11-07 17:19:50 -0500898
Al Viro0714a532011-11-24 22:19:58 -0500899 BUG_ON(parent == mnt);
Ram Paib90fa9a2005-11-07 17:19:50 -0500900
Al Viro1a4eeaf2011-11-25 02:19:55 -0500901 list_add_tail(&head, &mnt->mnt_list);
Al Virof7a99c52012-06-09 00:59:08 -0400902 list_for_each_entry(m, &head, mnt_list)
Al Viro143c8c92011-11-25 00:46:35 -0500903 m->mnt_ns = n;
Al Virof03c6592011-01-14 22:30:21 -0500904
Ram Paib90fa9a2005-11-07 17:19:50 -0500905 list_splice(&head, n->list.prev);
906
Eric W. Biedermand2921682016-09-28 00:27:17 -0500907 n->mounts += n->pending_mounts;
908 n->pending_mounts = 0;
909
Eric W. Biederman1064f872017-01-20 18:28:35 +1300910 __attach_mnt(mnt, parent);
Kirill Korotaev6b3286e2006-12-08 02:37:56 -0800911 touch_mnt_namespace(n);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700912}
913
Al Viro909b0a82011-11-25 03:06:56 -0500914static struct mount *next_mnt(struct mount *p, struct mount *root)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700915{
Al Viro6b41d532011-11-24 23:24:33 -0500916 struct list_head *next = p->mnt_mounts.next;
917 if (next == &p->mnt_mounts) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700918 while (1) {
Al Viro909b0a82011-11-25 03:06:56 -0500919 if (p == root)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700920 return NULL;
Al Viro6b41d532011-11-24 23:24:33 -0500921 next = p->mnt_child.next;
922 if (next != &p->mnt_parent->mnt_mounts)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700923 break;
Al Viro0714a532011-11-24 22:19:58 -0500924 p = p->mnt_parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700925 }
926 }
Al Viro6b41d532011-11-24 23:24:33 -0500927 return list_entry(next, struct mount, mnt_child);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700928}
929
Al Viro315fc832011-11-24 18:57:30 -0500930static struct mount *skip_mnt_tree(struct mount *p)
Ram Pai9676f0c2005-11-07 17:21:20 -0500931{
Al Viro6b41d532011-11-24 23:24:33 -0500932 struct list_head *prev = p->mnt_mounts.prev;
933 while (prev != &p->mnt_mounts) {
934 p = list_entry(prev, struct mount, mnt_child);
935 prev = p->mnt_mounts.prev;
Ram Pai9676f0c2005-11-07 17:21:20 -0500936 }
937 return p;
938}
939
Al Viro8f2918892018-11-04 06:48:34 -0500940/**
941 * vfs_create_mount - Create a mount for a configured superblock
942 * @fc: The configuration context with the superblock attached
943 *
944 * Create a mount to an already configured superblock. If necessary, the
945 * caller should invoke vfs_get_tree() before calling this.
946 *
947 * Note that this does not attach the mount to anything.
948 */
949struct vfsmount *vfs_create_mount(struct fs_context *fc)
Al Viro9d412a42011-03-17 22:08:28 -0400950{
Al Virob105e272011-11-24 20:38:33 -0500951 struct mount *mnt;
Al Viro9d412a42011-03-17 22:08:28 -0400952
Al Viro8f2918892018-11-04 06:48:34 -0500953 if (!fc->root)
954 return ERR_PTR(-EINVAL);
Al Viro9d412a42011-03-17 22:08:28 -0400955
Al Viro8f2918892018-11-04 06:48:34 -0500956 mnt = alloc_vfsmnt(fc->source ?: "none");
Al Viro9d412a42011-03-17 22:08:28 -0400957 if (!mnt)
958 return ERR_PTR(-ENOMEM);
959
Al Viro8f2918892018-11-04 06:48:34 -0500960 if (fc->sb_flags & SB_KERNMOUNT)
Al Virob105e272011-11-24 20:38:33 -0500961 mnt->mnt.mnt_flags = MNT_INTERNAL;
Al Viro9d412a42011-03-17 22:08:28 -0400962
Al Viro8f2918892018-11-04 06:48:34 -0500963 atomic_inc(&fc->root->d_sb->s_active);
964 mnt->mnt.mnt_sb = fc->root->d_sb;
965 mnt->mnt.mnt_root = dget(fc->root);
966 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
967 mnt->mnt_parent = mnt;
Al Viro9d412a42011-03-17 22:08:28 -0400968
Al Viro719ea2f2013-09-29 11:24:49 -0400969 lock_mount_hash();
Al Viro8f2918892018-11-04 06:48:34 -0500970 list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
Al Viro719ea2f2013-09-29 11:24:49 -0400971 unlock_mount_hash();
Al Virob105e272011-11-24 20:38:33 -0500972 return &mnt->mnt;
Al Viro9d412a42011-03-17 22:08:28 -0400973}
Al Viro8f2918892018-11-04 06:48:34 -0500974EXPORT_SYMBOL(vfs_create_mount);
975
976struct vfsmount *fc_mount(struct fs_context *fc)
977{
978 int err = vfs_get_tree(fc);
979 if (!err) {
980 up_write(&fc->root->d_sb->s_umount);
981 return vfs_create_mount(fc);
982 }
983 return ERR_PTR(err);
984}
985EXPORT_SYMBOL(fc_mount);
986
David Howells9bc61ab2018-11-04 03:19:03 -0500987struct vfsmount *vfs_kern_mount(struct file_system_type *type,
988 int flags, const char *name,
989 void *data)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700990{
David Howells9bc61ab2018-11-04 03:19:03 -0500991 struct fs_context *fc;
Al Viro8f2918892018-11-04 06:48:34 -0500992 struct vfsmount *mnt;
David Howells9bc61ab2018-11-04 03:19:03 -0500993 int ret = 0;
Al Viro9d412a42011-03-17 22:08:28 -0400994
995 if (!type)
David Howells3e1aeb02018-11-01 23:07:25 +0000996 return ERR_PTR(-EINVAL);
Al Viro9d412a42011-03-17 22:08:28 -0400997
David Howells9bc61ab2018-11-04 03:19:03 -0500998 fc = fs_context_for_mount(type, flags);
999 if (IS_ERR(fc))
1000 return ERR_CAST(fc);
1001
David Howells3e1aeb02018-11-01 23:07:25 +00001002 if (name)
1003 ret = vfs_parse_fs_string(fc, "source",
1004 name, strlen(name));
David Howells9bc61ab2018-11-04 03:19:03 -05001005 if (!ret)
1006 ret = parse_monolithic_mount_data(fc, data);
1007 if (!ret)
Al Viro8f2918892018-11-04 06:48:34 -05001008 mnt = fc_mount(fc);
1009 else
1010 mnt = ERR_PTR(ret);
Al Viro9d412a42011-03-17 22:08:28 -04001011
David Howells9bc61ab2018-11-04 03:19:03 -05001012 put_fs_context(fc);
Al Viro8f2918892018-11-04 06:48:34 -05001013 return mnt;
Al Viro9d412a42011-03-17 22:08:28 -04001014}
1015EXPORT_SYMBOL_GPL(vfs_kern_mount);
1016
Eric W. Biederman93faccbb2017-02-01 06:06:16 +13001017struct vfsmount *
1018vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
1019 const char *name, void *data)
1020{
1021 /* Until it is worked out how to pass the user namespace
1022 * through from the parent mount to the submount don't support
1023 * unprivileged mounts with submounts.
1024 */
1025 if (mountpoint->d_sb->s_user_ns != &init_user_ns)
1026 return ERR_PTR(-EPERM);
1027
David Howellse462ec52017-07-17 08:45:35 +01001028 return vfs_kern_mount(type, SB_SUBMOUNT, name, data);
Eric W. Biederman93faccbb2017-02-01 06:06:16 +13001029}
1030EXPORT_SYMBOL_GPL(vfs_submount);
1031
Al Viro87129cc2011-11-24 21:24:27 -05001032static struct mount *clone_mnt(struct mount *old, struct dentry *root,
Ram Pai36341f62005-11-07 17:17:22 -05001033 int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001034{
Al Viro87129cc2011-11-24 21:24:27 -05001035 struct super_block *sb = old->mnt.mnt_sb;
David Howellsbe34d1a2012-06-25 12:55:18 +01001036 struct mount *mnt;
1037 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038
David Howellsbe34d1a2012-06-25 12:55:18 +01001039 mnt = alloc_vfsmnt(old->mnt_devname);
1040 if (!mnt)
1041 return ERR_PTR(-ENOMEM);
Miklos Szeredi719f5d72008-03-27 13:06:23 +01001042
Eric W. Biederman7a472ef2012-07-31 13:13:04 -07001043 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
David Howellsbe34d1a2012-06-25 12:55:18 +01001044 mnt->mnt_group_id = 0; /* not a peer of original */
1045 else
1046 mnt->mnt_group_id = old->mnt_group_id;
Miklos Szeredi719f5d72008-03-27 13:06:23 +01001047
David Howellsbe34d1a2012-06-25 12:55:18 +01001048 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
1049 err = mnt_alloc_group_id(mnt);
1050 if (err)
1051 goto out_free;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052 }
David Howellsbe34d1a2012-06-25 12:55:18 +01001053
Al Viro16a34ad2018-04-19 22:03:08 -04001054 mnt->mnt.mnt_flags = old->mnt.mnt_flags;
1055 mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL);
Eric W. Biederman5ff9d8a2013-03-29 21:04:39 -07001056
David Howellsbe34d1a2012-06-25 12:55:18 +01001057 atomic_inc(&sb->s_active);
1058 mnt->mnt.mnt_sb = sb;
1059 mnt->mnt.mnt_root = dget(root);
1060 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1061 mnt->mnt_parent = mnt;
Al Viro719ea2f2013-09-29 11:24:49 -04001062 lock_mount_hash();
David Howellsbe34d1a2012-06-25 12:55:18 +01001063 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
Al Viro719ea2f2013-09-29 11:24:49 -04001064 unlock_mount_hash();
David Howellsbe34d1a2012-06-25 12:55:18 +01001065
Eric W. Biederman7a472ef2012-07-31 13:13:04 -07001066 if ((flag & CL_SLAVE) ||
1067 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
David Howellsbe34d1a2012-06-25 12:55:18 +01001068 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
1069 mnt->mnt_master = old;
1070 CLEAR_MNT_SHARED(mnt);
1071 } else if (!(flag & CL_PRIVATE)) {
1072 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
1073 list_add(&mnt->mnt_share, &old->mnt_share);
1074 if (IS_MNT_SLAVE(old))
1075 list_add(&mnt->mnt_slave, &old->mnt_slave);
1076 mnt->mnt_master = old->mnt_master;
Al Viro5235d442016-11-20 19:33:09 -05001077 } else {
1078 CLEAR_MNT_SHARED(mnt);
David Howellsbe34d1a2012-06-25 12:55:18 +01001079 }
1080 if (flag & CL_MAKE_SHARED)
1081 set_mnt_shared(mnt);
1082
1083 /* stick the duplicate mount on the same expiry list
1084 * as the original if that was on one */
1085 if (flag & CL_EXPIRE) {
1086 if (!list_empty(&old->mnt_expire))
1087 list_add(&mnt->mnt_expire, &old->mnt_expire);
1088 }
1089
Al Virocb338d02011-11-24 20:55:08 -05001090 return mnt;
Miklos Szeredi719f5d72008-03-27 13:06:23 +01001091
1092 out_free:
David Howells8ffcb322014-01-24 12:17:54 +00001093 mnt_free_id(mnt);
Miklos Szeredi719f5d72008-03-27 13:06:23 +01001094 free_vfsmnt(mnt);
David Howellsbe34d1a2012-06-25 12:55:18 +01001095 return ERR_PTR(err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096}
1097
Al Viro9ea459e12014-08-08 13:08:20 -04001098static void cleanup_mnt(struct mount *mnt)
1099{
Al Viro56cbb422019-07-04 16:57:51 -04001100 struct hlist_node *p;
1101 struct mount *m;
Al Viro9ea459e12014-08-08 13:08:20 -04001102 /*
Al Viro56cbb422019-07-04 16:57:51 -04001103 * The warning here probably indicates that somebody messed
1104 * up a mnt_want/drop_write() pair. If this happens, the
1105 * filesystem was probably unable to make r/w->r/o transitions.
Al Viro9ea459e12014-08-08 13:08:20 -04001106 * The locking used to deal with mnt_count decrement provides barriers,
1107 * so mnt_get_writers() below is safe.
1108 */
1109 WARN_ON(mnt_get_writers(mnt));
1110 if (unlikely(mnt->mnt_pins.first))
1111 mnt_pin_kill(mnt);
Al Viro56cbb422019-07-04 16:57:51 -04001112 hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) {
1113 hlist_del(&m->mnt_umount);
1114 mntput(&m->mnt);
1115 }
Al Viro9ea459e12014-08-08 13:08:20 -04001116 fsnotify_vfsmount_delete(&mnt->mnt);
1117 dput(mnt->mnt.mnt_root);
1118 deactivate_super(mnt->mnt.mnt_sb);
1119 mnt_free_id(mnt);
1120 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
1121}
1122
1123static void __cleanup_mnt(struct rcu_head *head)
1124{
1125 cleanup_mnt(container_of(head, struct mount, mnt_rcu));
1126}
1127
1128static LLIST_HEAD(delayed_mntput_list);
1129static void delayed_mntput(struct work_struct *unused)
1130{
1131 struct llist_node *node = llist_del_all(&delayed_mntput_list);
Byungchul Park29785732017-08-07 17:44:45 +09001132 struct mount *m, *t;
Al Viro9ea459e12014-08-08 13:08:20 -04001133
Byungchul Park29785732017-08-07 17:44:45 +09001134 llist_for_each_entry_safe(m, t, node, mnt_llist)
1135 cleanup_mnt(m);
Al Viro9ea459e12014-08-08 13:08:20 -04001136}
1137static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
1138
Al Viro900148d2011-11-25 00:33:11 -05001139static void mntput_no_expire(struct mount *mnt)
Al Viro7b7b1ac2005-11-07 17:13:39 -05001140{
Al Viro4edbe132019-06-30 10:39:08 -04001141 LIST_HEAD(list);
Eric Biggersedf7ddb2020-10-31 21:40:21 -07001142 int count;
Al Viro4edbe132019-06-30 10:39:08 -04001143
Al Viro48a066e2013-09-29 22:06:07 -04001144 rcu_read_lock();
Al Viro9ea0a462018-08-09 17:21:17 -04001145 if (likely(READ_ONCE(mnt->mnt_ns))) {
1146 /*
1147 * Since we don't do lock_mount_hash() here,
1148 * ->mnt_ns can change under us. However, if it's
1149 * non-NULL, then there's a reference that won't
1150 * be dropped until after an RCU delay done after
1151 * turning ->mnt_ns NULL. So if we observe it
1152 * non-NULL under rcu_read_lock(), the reference
1153 * we are dropping is not the final one.
1154 */
1155 mnt_add_count(mnt, -1);
Al Viro48a066e2013-09-29 22:06:07 -04001156 rcu_read_unlock();
Al Virof03c6592011-01-14 22:30:21 -05001157 return;
Nick Pigginb3e19d92011-01-07 17:50:11 +11001158 }
Al Viro719ea2f2013-09-29 11:24:49 -04001159 lock_mount_hash();
Al Viro119e1ef2018-08-09 17:51:32 -04001160 /*
1161 * make sure that if __legitimize_mnt() has not seen us grab
1162 * mount_lock, we'll see their refcount increment here.
1163 */
1164 smp_mb();
Al Viro9ea0a462018-08-09 17:21:17 -04001165 mnt_add_count(mnt, -1);
Eric Biggersedf7ddb2020-10-31 21:40:21 -07001166 count = mnt_get_count(mnt);
1167 if (count != 0) {
1168 WARN_ON(count < 0);
Al Viro48a066e2013-09-29 22:06:07 -04001169 rcu_read_unlock();
Al Viro719ea2f2013-09-29 11:24:49 -04001170 unlock_mount_hash();
Nick Pigginb3e19d92011-01-07 17:50:11 +11001171 return;
1172 }
Al Viro48a066e2013-09-29 22:06:07 -04001173 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
1174 rcu_read_unlock();
1175 unlock_mount_hash();
1176 return;
1177 }
1178 mnt->mnt.mnt_flags |= MNT_DOOMED;
1179 rcu_read_unlock();
Andi Kleen962830d2012-05-08 13:32:02 +09301180
Miklos Szeredi39f7c4d2011-11-21 12:11:30 +01001181 list_del(&mnt->mnt_instance);
Eric W. Biedermance07d892014-12-23 21:37:03 -06001182
1183 if (unlikely(!list_empty(&mnt->mnt_mounts))) {
1184 struct mount *p, *tmp;
1185 list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) {
Al Viro4edbe132019-06-30 10:39:08 -04001186 __put_mountpoint(unhash_mnt(p), &list);
Al Viro56cbb422019-07-04 16:57:51 -04001187 hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children);
Eric W. Biedermance07d892014-12-23 21:37:03 -06001188 }
1189 }
Al Viro719ea2f2013-09-29 11:24:49 -04001190 unlock_mount_hash();
Al Viro4edbe132019-06-30 10:39:08 -04001191 shrink_dentry_list(&list);
Al Viro649a7952013-09-28 12:41:25 -04001192
Al Viro9ea459e12014-08-08 13:08:20 -04001193 if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
1194 struct task_struct *task = current;
1195 if (likely(!(task->flags & PF_KTHREAD))) {
1196 init_task_work(&mnt->mnt_rcu, __cleanup_mnt);
Jens Axboe91989c72020-10-16 09:02:26 -06001197 if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME))
Al Viro9ea459e12014-08-08 13:08:20 -04001198 return;
1199 }
1200 if (llist_add(&mnt->mnt_llist, &delayed_mntput_list))
1201 schedule_delayed_work(&delayed_mntput_work, 1);
1202 return;
1203 }
1204 cleanup_mnt(mnt);
Al Viro7b7b1ac2005-11-07 17:13:39 -05001205}
Nick Pigginb3e19d92011-01-07 17:50:11 +11001206
1207void mntput(struct vfsmount *mnt)
1208{
1209 if (mnt) {
Al Viro863d6842011-11-25 00:57:42 -05001210 struct mount *m = real_mount(mnt);
Nick Pigginb3e19d92011-01-07 17:50:11 +11001211 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
Al Viro863d6842011-11-25 00:57:42 -05001212 if (unlikely(m->mnt_expiry_mark))
1213 m->mnt_expiry_mark = 0;
1214 mntput_no_expire(m);
Nick Pigginb3e19d92011-01-07 17:50:11 +11001215 }
1216}
1217EXPORT_SYMBOL(mntput);
1218
1219struct vfsmount *mntget(struct vfsmount *mnt)
1220{
1221 if (mnt)
Al Viro83adc752011-11-24 22:37:54 -05001222 mnt_add_count(real_mount(mnt), 1);
Nick Pigginb3e19d92011-01-07 17:50:11 +11001223 return mnt;
1224}
1225EXPORT_SYMBOL(mntget);
1226
Ian Kentc6609c02016-11-24 08:03:41 +11001227/* path_is_mountpoint() - Check if path is a mount in the current
1228 * namespace.
1229 *
1230 * d_mountpoint() can only be used reliably to establish if a dentry is
1231 * not mounted in any namespace and that common case is handled inline.
1232 * d_mountpoint() isn't aware of the possibility there may be multiple
1233 * mounts using a given dentry in a different namespace. This function
1234 * checks if the passed in path is a mountpoint rather than the dentry
1235 * alone.
1236 */
1237bool path_is_mountpoint(const struct path *path)
1238{
1239 unsigned seq;
1240 bool res;
1241
1242 if (!d_mountpoint(path->dentry))
1243 return false;
1244
1245 rcu_read_lock();
1246 do {
1247 seq = read_seqbegin(&mount_lock);
1248 res = __path_is_mountpoint(path);
1249 } while (read_seqretry(&mount_lock, seq));
1250 rcu_read_unlock();
1251
1252 return res;
1253}
1254EXPORT_SYMBOL(path_is_mountpoint);
1255
Al Viroca71cf72016-11-20 19:45:28 -05001256struct vfsmount *mnt_clone_internal(const struct path *path)
Al Viro7b7b1ac2005-11-07 17:13:39 -05001257{
Al Viro3064c352014-08-07 09:12:31 -04001258 struct mount *p;
1259 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
1260 if (IS_ERR(p))
1261 return ERR_CAST(p);
1262 p->mnt.mnt_flags |= MNT_INTERNAL;
1263 return &p->mnt;
Al Viro7b7b1ac2005-11-07 17:13:39 -05001264}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265
Miklos Szeredia1a2c402008-03-27 13:06:24 +01001266#ifdef CONFIG_PROC_FS
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02001267static struct mount *mnt_list_next(struct mnt_namespace *ns,
1268 struct list_head *p)
1269{
1270 struct mount *mnt, *ret = NULL;
1271
1272 lock_ns_list(ns);
1273 list_for_each_continue(p, &ns->list) {
1274 mnt = list_entry(p, typeof(*mnt), mnt_list);
1275 if (!mnt_is_cursor(mnt)) {
1276 ret = mnt;
1277 break;
1278 }
1279 }
1280 unlock_ns_list(ns);
1281
1282 return ret;
1283}
1284
Al Viro0226f492011-12-06 12:21:54 -05001285/* iterator; we want it to have access to namespace_sem, thus here... */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286static void *m_start(struct seq_file *m, loff_t *pos)
1287{
Yann Droneaudede1bf02015-06-30 14:57:30 -07001288 struct proc_mounts *p = m->private;
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02001289 struct list_head *prev;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001290
Ram Pai390c6842005-11-07 17:17:51 -05001291 down_read(&namespace_sem);
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02001292 if (!*pos) {
1293 prev = &p->ns->list;
1294 } else {
1295 prev = &p->cursor.mnt_list;
1296
1297 /* Read after we'd reached the end? */
1298 if (list_empty(prev))
1299 return NULL;
Al Viroc7999c32014-02-27 14:40:10 -05001300 }
1301
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02001302 return mnt_list_next(p->ns, prev);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001303}
1304
1305static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1306{
Yann Droneaudede1bf02015-06-30 14:57:30 -07001307 struct proc_mounts *p = m->private;
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02001308 struct mount *mnt = v;
Pavel Emelianovb0765fb2007-07-15 23:39:55 -07001309
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02001310 ++*pos;
1311 return mnt_list_next(p->ns, &mnt->mnt_list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001312}
1313
1314static void m_stop(struct seq_file *m, void *v)
1315{
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02001316 struct proc_mounts *p = m->private;
1317 struct mount *mnt = v;
1318
1319 lock_ns_list(p->ns);
1320 if (mnt)
1321 list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list);
1322 else
1323 list_del_init(&p->cursor.mnt_list);
1324 unlock_ns_list(p->ns);
Ram Pai390c6842005-11-07 17:17:51 -05001325 up_read(&namespace_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001326}
1327
Al Viro0226f492011-12-06 12:21:54 -05001328static int m_show(struct seq_file *m, void *v)
Al Viro9f5596a2010-02-05 00:40:25 -05001329{
Yann Droneaudede1bf02015-06-30 14:57:30 -07001330 struct proc_mounts *p = m->private;
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02001331 struct mount *r = v;
Al Viro0226f492011-12-06 12:21:54 -05001332 return p->show(m, &r->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333}
1334
Miklos Szeredia1a2c402008-03-27 13:06:24 +01001335const struct seq_operations mounts_op = {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336 .start = m_start,
1337 .next = m_next,
1338 .stop = m_stop,
Al Viro0226f492011-12-06 12:21:54 -05001339 .show = m_show,
Chuck Leverb4629fe2006-03-20 13:44:12 -05001340};
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02001341
1342void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor)
1343{
1344 down_read(&namespace_sem);
1345 lock_ns_list(ns);
1346 list_del(&cursor->mnt_list);
1347 unlock_ns_list(ns);
1348 up_read(&namespace_sem);
1349}
Miklos Szeredia1a2c402008-03-27 13:06:24 +01001350#endif /* CONFIG_PROC_FS */
Chuck Leverb4629fe2006-03-20 13:44:12 -05001351
Linus Torvalds1da177e2005-04-16 15:20:36 -07001352/**
1353 * may_umount_tree - check if a mount tree is busy
1354 * @mnt: root of mount tree
1355 *
1356 * This is called to check if a tree of mounts has any
1357 * open files, pwds, chroots or sub mounts that are
1358 * busy.
1359 */
Al Viro909b0a82011-11-25 03:06:56 -05001360int may_umount_tree(struct vfsmount *m)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001361{
Al Viro909b0a82011-11-25 03:06:56 -05001362 struct mount *mnt = real_mount(m);
Ram Pai36341f62005-11-07 17:17:22 -05001363 int actual_refs = 0;
1364 int minimum_refs = 0;
Al Viro315fc832011-11-24 18:57:30 -05001365 struct mount *p;
Al Viro909b0a82011-11-25 03:06:56 -05001366 BUG_ON(!m);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367
Nick Pigginb3e19d92011-01-07 17:50:11 +11001368 /* write lock needed for mnt_get_count */
Al Viro719ea2f2013-09-29 11:24:49 -04001369 lock_mount_hash();
Al Viro909b0a82011-11-25 03:06:56 -05001370 for (p = mnt; p; p = next_mnt(p, mnt)) {
Al Viro83adc752011-11-24 22:37:54 -05001371 actual_refs += mnt_get_count(p);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001372 minimum_refs += 2;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001373 }
Al Viro719ea2f2013-09-29 11:24:49 -04001374 unlock_mount_hash();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001375
1376 if (actual_refs > minimum_refs)
Ian Kente3474a82006-03-27 01:14:51 -08001377 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001378
Ian Kente3474a82006-03-27 01:14:51 -08001379 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001380}
1381
1382EXPORT_SYMBOL(may_umount_tree);
1383
1384/**
1385 * may_umount - check if a mount point is busy
1386 * @mnt: root of mount
1387 *
1388 * This is called to check if a mount point has any
1389 * open files, pwds, chroots or sub mounts. If the
1390 * mount has sub mounts this will return busy
1391 * regardless of whether the sub mounts are busy.
1392 *
1393 * Doesn't take quota and stuff into account. IOW, in some cases it will
1394 * give false negatives. The main reason why it's here is that we need
1395 * a non-destructive way to look for easily umountable filesystems.
1396 */
1397int may_umount(struct vfsmount *mnt)
1398{
Ian Kente3474a82006-03-27 01:14:51 -08001399 int ret = 1;
Al Viro8ad08d82010-01-16 12:56:08 -05001400 down_read(&namespace_sem);
Al Viro719ea2f2013-09-29 11:24:49 -04001401 lock_mount_hash();
Al Viro1ab59732011-11-24 21:35:16 -05001402 if (propagate_mount_busy(real_mount(mnt), 2))
Ian Kente3474a82006-03-27 01:14:51 -08001403 ret = 0;
Al Viro719ea2f2013-09-29 11:24:49 -04001404 unlock_mount_hash();
Al Viro8ad08d82010-01-16 12:56:08 -05001405 up_read(&namespace_sem);
Ram Paia05964f2005-11-07 17:20:17 -05001406 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407}
1408
1409EXPORT_SYMBOL(may_umount);
1410
Al Viro97216be2013-03-16 15:12:40 -04001411static void namespace_unlock(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001412{
Eric W. Biedermana3b3c562015-04-02 20:33:53 -05001413 struct hlist_head head;
Al Viro56cbb422019-07-04 16:57:51 -04001414 struct hlist_node *p;
1415 struct mount *m;
Al Viro4edbe132019-06-30 10:39:08 -04001416 LIST_HEAD(list);
Al Viro97216be2013-03-16 15:12:40 -04001417
Eric W. Biedermana3b3c562015-04-02 20:33:53 -05001418 hlist_move_list(&unmounted, &head);
Al Viro4edbe132019-06-30 10:39:08 -04001419 list_splice_init(&ex_mountpoints, &list);
Al Viro97216be2013-03-16 15:12:40 -04001420
Al Viro97216be2013-03-16 15:12:40 -04001421 up_write(&namespace_sem);
1422
Al Viro4edbe132019-06-30 10:39:08 -04001423 shrink_dentry_list(&list);
1424
Eric W. Biedermana3b3c562015-04-02 20:33:53 -05001425 if (likely(hlist_empty(&head)))
1426 return;
1427
NeilBrown22cb7402018-11-30 10:33:18 +11001428 synchronize_rcu_expedited();
Al Viro48a066e2013-09-29 22:06:07 -04001429
Al Viro56cbb422019-07-04 16:57:51 -04001430 hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
1431 hlist_del(&m->mnt_umount);
1432 mntput(&m->mnt);
1433 }
Ram Pai70fbcdf2005-11-07 17:17:04 -05001434}
1435
Al Viro97216be2013-03-16 15:12:40 -04001436static inline void namespace_lock(void)
Al Viroe3197d82013-03-16 14:35:16 -04001437{
Al Viro97216be2013-03-16 15:12:40 -04001438 down_write(&namespace_sem);
Al Viroe3197d82013-03-16 14:35:16 -04001439}
1440
Eric W. Biedermane819f152014-12-24 07:20:01 -06001441enum umount_tree_flags {
1442 UMOUNT_SYNC = 1,
1443 UMOUNT_PROPAGATE = 2,
Eric W. Biedermane0c9c0a2015-04-01 18:30:06 -05001444 UMOUNT_CONNECTED = 4,
Eric W. Biedermane819f152014-12-24 07:20:01 -06001445};
Eric W. Biedermanf2d0a122015-07-17 14:15:30 -05001446
1447static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
1448{
1449 /* Leaving mounts connected is only valid for lazy umounts */
1450 if (how & UMOUNT_SYNC)
1451 return true;
1452
1453 /* A mount without a parent has nothing to be connected to */
1454 if (!mnt_has_parent(mnt))
1455 return true;
1456
1457 /* Because the reference counting rules change when mounts are
1458 * unmounted and connected, umounted mounts may not be
1459 * connected to mounted mounts.
1460 */
1461 if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
1462 return true;
1463
1464 /* Has it been requested that the mount remain connected? */
1465 if (how & UMOUNT_CONNECTED)
1466 return false;
1467
1468 /* Is the mount locked such that it needs to remain connected? */
1469 if (IS_MNT_LOCKED(mnt))
1470 return false;
1471
1472 /* By default disconnect the mount */
1473 return true;
1474}
1475
Nick Piggin99b7db72010-08-18 04:37:39 +10001476/*
Al Viro48a066e2013-09-29 22:06:07 -04001477 * mount_lock must be held
Nick Piggin99b7db72010-08-18 04:37:39 +10001478 * namespace_sem must be held for write
1479 */
Eric W. Biedermane819f152014-12-24 07:20:01 -06001480static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
Ram Pai70fbcdf2005-11-07 17:17:04 -05001481{
Eric W. Biedermanc003b262014-12-18 13:10:48 -06001482 LIST_HEAD(tmp_list);
Al Viro315fc832011-11-24 18:57:30 -05001483 struct mount *p;
Ram Pai70fbcdf2005-11-07 17:17:04 -05001484
Eric W. Biederman5d884572015-01-03 05:39:35 -06001485 if (how & UMOUNT_PROPAGATE)
1486 propagate_mount_unlock(mnt);
1487
Eric W. Biedermanc003b262014-12-18 13:10:48 -06001488 /* Gather the mounts to umount */
Eric W. Biederman590ce4bc2014-12-22 18:30:08 -06001489 for (p = mnt; p; p = next_mnt(p, mnt)) {
1490 p->mnt.mnt_flags |= MNT_UMOUNT;
Eric W. Biedermanc003b262014-12-18 13:10:48 -06001491 list_move(&p->mnt_list, &tmp_list);
Eric W. Biederman590ce4bc2014-12-22 18:30:08 -06001492 }
Eric W. Biedermanc003b262014-12-18 13:10:48 -06001493
Eric W. Biederman411a9382014-12-22 19:12:07 -06001494 /* Hide the mounts from mnt_mounts */
Eric W. Biedermanc003b262014-12-18 13:10:48 -06001495 list_for_each_entry(p, &tmp_list, mnt_list) {
Eric W. Biedermanc003b262014-12-18 13:10:48 -06001496 list_del_init(&p->mnt_child);
Al Viro38129a12014-03-20 21:10:51 -04001497 }
Ram Pai70fbcdf2005-11-07 17:17:04 -05001498
Eric W. Biedermanc003b262014-12-18 13:10:48 -06001499 /* Add propogated mounts to the tmp_list */
Eric W. Biedermane819f152014-12-24 07:20:01 -06001500 if (how & UMOUNT_PROPAGATE)
Al Viro7b8a53f2011-01-15 20:08:44 -05001501 propagate_umount(&tmp_list);
Ram Paia05964f2005-11-07 17:20:17 -05001502
Eric W. Biedermanc003b262014-12-18 13:10:48 -06001503 while (!list_empty(&tmp_list)) {
Eric W. Biedermand2921682016-09-28 00:27:17 -05001504 struct mnt_namespace *ns;
Eric W. Biedermance07d892014-12-23 21:37:03 -06001505 bool disconnect;
Eric W. Biedermanc003b262014-12-18 13:10:48 -06001506 p = list_first_entry(&tmp_list, struct mount, mnt_list);
Al Viro6776db3d2011-11-25 00:22:05 -05001507 list_del_init(&p->mnt_expire);
Al Viro1a4eeaf2011-11-25 02:19:55 -05001508 list_del_init(&p->mnt_list);
Eric W. Biedermand2921682016-09-28 00:27:17 -05001509 ns = p->mnt_ns;
1510 if (ns) {
1511 ns->mounts--;
1512 __touch_mnt_namespace(ns);
1513 }
Al Viro143c8c92011-11-25 00:46:35 -05001514 p->mnt_ns = NULL;
Eric W. Biedermane819f152014-12-24 07:20:01 -06001515 if (how & UMOUNT_SYNC)
Al Viro48a066e2013-09-29 22:06:07 -04001516 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
Al Viro87b95ce2015-01-10 19:01:08 -05001517
Eric W. Biedermanf2d0a122015-07-17 14:15:30 -05001518 disconnect = disconnect_mount(p, how);
Al Viro676da582011-11-24 21:47:05 -05001519 if (mnt_has_parent(p)) {
Al Viro81b6b062014-08-30 18:32:05 -04001520 mnt_add_count(p->mnt_parent, -1);
Eric W. Biedermance07d892014-12-23 21:37:03 -06001521 if (!disconnect) {
1522 /* Don't forget about p */
1523 list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
1524 } else {
1525 umount_mnt(p);
1526 }
Al Viro7c4b93d2008-03-21 23:59:49 -04001527 }
Al Viro0f0afb12011-11-24 20:43:10 -05001528 change_mnt_propagation(p, MS_PRIVATE);
Al Viro19a1c402019-07-24 12:45:46 -04001529 if (disconnect)
1530 hlist_add_head(&p->mnt_umount, &unmounted);
Al Viro38129a12014-03-20 21:10:51 -04001531 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001532}
1533
Al Virob54b9be2013-03-16 14:39:34 -04001534static void shrink_submounts(struct mount *mnt);
Al Viroc35038b2008-03-22 00:46:23 -04001535
David Howells8d0347f2018-11-04 09:28:36 -05001536static int do_umount_root(struct super_block *sb)
1537{
1538 int ret = 0;
1539
1540 down_write(&sb->s_umount);
1541 if (!sb_rdonly(sb)) {
1542 struct fs_context *fc;
1543
1544 fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY,
1545 SB_RDONLY);
1546 if (IS_ERR(fc)) {
1547 ret = PTR_ERR(fc);
1548 } else {
1549 ret = parse_monolithic_mount_data(fc, NULL);
1550 if (!ret)
1551 ret = reconfigure_super(fc);
1552 put_fs_context(fc);
1553 }
1554 }
1555 up_write(&sb->s_umount);
1556 return ret;
1557}
1558
Al Viro1ab59732011-11-24 21:35:16 -05001559static int do_umount(struct mount *mnt, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001560{
Al Viro1ab59732011-11-24 21:35:16 -05001561 struct super_block *sb = mnt->mnt.mnt_sb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001562 int retval;
1563
Al Viro1ab59732011-11-24 21:35:16 -05001564 retval = security_sb_umount(&mnt->mnt, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001565 if (retval)
1566 return retval;
1567
1568 /*
1569 * Allow userspace to request a mountpoint be expired rather than
1570 * unmounting unconditionally. Unmount only happens if:
1571 * (1) the mark is already set (the mark is cleared by mntput())
1572 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1573 */
1574 if (flags & MNT_EXPIRE) {
Al Viro1ab59732011-11-24 21:35:16 -05001575 if (&mnt->mnt == current->fs->root.mnt ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576 flags & (MNT_FORCE | MNT_DETACH))
1577 return -EINVAL;
1578
Nick Pigginb3e19d92011-01-07 17:50:11 +11001579 /*
1580 * probably don't strictly need the lock here if we examined
1581 * all race cases, but it's a slowpath.
1582 */
Al Viro719ea2f2013-09-29 11:24:49 -04001583 lock_mount_hash();
Al Viro83adc752011-11-24 22:37:54 -05001584 if (mnt_get_count(mnt) != 2) {
Al Viro719ea2f2013-09-29 11:24:49 -04001585 unlock_mount_hash();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001586 return -EBUSY;
Nick Pigginb3e19d92011-01-07 17:50:11 +11001587 }
Al Viro719ea2f2013-09-29 11:24:49 -04001588 unlock_mount_hash();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001589
Al Viro863d6842011-11-25 00:57:42 -05001590 if (!xchg(&mnt->mnt_expiry_mark, 1))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001591 return -EAGAIN;
1592 }
1593
1594 /*
1595 * If we may have to abort operations to get out of this
1596 * mount, and they will themselves hold resources we must
1597 * allow the fs to do things. In the Unix tradition of
1598 * 'Gee thats tricky lets do it in userspace' the umount_begin
1599 * might fail to complete on the first run through as other tasks
1600 * must return, and the like. Thats for the mount program to worry
1601 * about for the moment.
1602 */
1603
Al Viro42faad92008-04-24 07:21:56 -04001604 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
Al Viro42faad92008-04-24 07:21:56 -04001605 sb->s_op->umount_begin(sb);
Al Viro42faad92008-04-24 07:21:56 -04001606 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001607
1608 /*
1609 * No sense to grab the lock for this test, but test itself looks
1610 * somewhat bogus. Suggestions for better replacement?
1611 * Ho-hum... In principle, we might treat that as umount + switch
1612 * to rootfs. GC would eventually take care of the old vfsmount.
1613 * Actually it makes sense, especially if rootfs would contain a
1614 * /reboot - static binary that would close all descriptors and
1615 * call reboot(9). Then init(8) could umount root and exec /reboot.
1616 */
Al Viro1ab59732011-11-24 21:35:16 -05001617 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001618 /*
1619 * Special case for "unmounting" root ...
1620 * we just try to remount it readonly.
1621 */
Eric W. Biedermanbc6155d2017-09-18 17:58:08 -05001622 if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
Andy Lutomirskia1480dc2014-10-08 12:32:47 -07001623 return -EPERM;
David Howells8d0347f2018-11-04 09:28:36 -05001624 return do_umount_root(sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001625 }
1626
Al Viro97216be2013-03-16 15:12:40 -04001627 namespace_lock();
Al Viro719ea2f2013-09-29 11:24:49 -04001628 lock_mount_hash();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001629
Eric W. Biederman25d202e2018-10-22 10:21:38 -05001630 /* Recheck MNT_LOCKED with the locks held */
1631 retval = -EINVAL;
1632 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1633 goto out;
1634
1635 event++;
Al Viro48a066e2013-09-29 22:06:07 -04001636 if (flags & MNT_DETACH) {
Al Viro1a4eeaf2011-11-25 02:19:55 -05001637 if (!list_empty(&mnt->mnt_list))
Eric W. Biedermane819f152014-12-24 07:20:01 -06001638 umount_tree(mnt, UMOUNT_PROPAGATE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001639 retval = 0;
Al Viro48a066e2013-09-29 22:06:07 -04001640 } else {
1641 shrink_submounts(mnt);
1642 retval = -EBUSY;
1643 if (!propagate_mount_busy(mnt, 2)) {
1644 if (!list_empty(&mnt->mnt_list))
Eric W. Biedermane819f152014-12-24 07:20:01 -06001645 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
Al Viro48a066e2013-09-29 22:06:07 -04001646 retval = 0;
1647 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001648 }
Eric W. Biederman25d202e2018-10-22 10:21:38 -05001649out:
Al Viro719ea2f2013-09-29 11:24:49 -04001650 unlock_mount_hash();
Al Viroe3197d82013-03-16 14:35:16 -04001651 namespace_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001652 return retval;
1653}
1654
Eric W. Biederman80b5dce2013-10-03 01:31:18 -07001655/*
1656 * __detach_mounts - lazily unmount all mounts on the specified dentry
1657 *
1658 * During unlink, rmdir, and d_drop it is possible to loose the path
1659 * to an existing mountpoint, and wind up leaking the mount.
1660 * detach_mounts allows lazily unmounting those mounts instead of
1661 * leaking them.
1662 *
1663 * The caller may hold dentry->d_inode->i_mutex.
1664 */
1665void __detach_mounts(struct dentry *dentry)
1666{
1667 struct mountpoint *mp;
1668 struct mount *mnt;
1669
1670 namespace_lock();
Eric W. Biederman3895dbf2017-01-03 14:18:43 +13001671 lock_mount_hash();
Eric W. Biederman80b5dce2013-10-03 01:31:18 -07001672 mp = lookup_mountpoint(dentry);
Al Viroadc9b5c2019-06-29 12:06:51 -04001673 if (!mp)
Eric W. Biederman80b5dce2013-10-03 01:31:18 -07001674 goto out_unlock;
1675
Andrey Ulanove06b9332016-04-15 14:24:41 -07001676 event++;
Eric W. Biederman80b5dce2013-10-03 01:31:18 -07001677 while (!hlist_empty(&mp->m_list)) {
1678 mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
Eric W. Biedermance07d892014-12-23 21:37:03 -06001679 if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
Eric W. Biedermanfe78fcc2015-07-17 14:54:27 -05001680 umount_mnt(mnt);
Al Viro56cbb422019-07-04 16:57:51 -04001681 hlist_add_head(&mnt->mnt_umount, &unmounted);
Eric W. Biedermance07d892014-12-23 21:37:03 -06001682 }
Eric W. Biedermane0c9c0a2015-04-01 18:30:06 -05001683 else umount_tree(mnt, UMOUNT_CONNECTED);
Eric W. Biederman80b5dce2013-10-03 01:31:18 -07001684 }
Eric W. Biederman80b5dce2013-10-03 01:31:18 -07001685 put_mountpoint(mp);
1686out_unlock:
Eric W. Biederman3895dbf2017-01-03 14:18:43 +13001687 unlock_mount_hash();
Eric W. Biederman80b5dce2013-10-03 01:31:18 -07001688 namespace_unlock();
1689}
1690
David Howellsdd111b32017-07-04 17:25:09 +01001691/*
Al Viro9b40bc92013-02-22 22:45:42 -05001692 * Is the caller allowed to modify his namespace?
1693 */
1694static inline bool may_mount(void)
1695{
1696 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1697}
1698
Jeff Laytondf2474a2019-08-15 15:21:17 -04001699#ifdef CONFIG_MANDATORY_FILE_LOCKING
Jeff Layton9e8925b2015-11-16 09:49:34 -05001700static inline bool may_mandlock(void)
1701{
Eric W. Biederman95ace752015-11-11 17:22:33 -06001702 return capable(CAP_SYS_ADMIN);
Jeff Layton9e8925b2015-11-16 09:49:34 -05001703}
Jeff Laytondf2474a2019-08-15 15:21:17 -04001704#else
1705static inline bool may_mandlock(void)
1706{
1707 pr_warn("VFS: \"mand\" mount option not supported");
1708 return false;
1709}
1710#endif
Jeff Layton9e8925b2015-11-16 09:49:34 -05001711
Christoph Hellwig25ccd24f2020-08-06 16:07:10 +02001712static int can_umount(const struct path *path, int flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001713{
Christoph Hellwig25ccd24f2020-08-06 16:07:10 +02001714 struct mount *mnt = real_mount(path->mnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001715
Miklos Szeredidb1f05b2010-02-10 12:15:53 +01001716 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1717 return -EINVAL;
Al Viro9b40bc92013-02-22 22:45:42 -05001718 if (!may_mount())
1719 return -EPERM;
Christoph Hellwig41525f52020-07-21 10:54:34 +02001720 if (path->dentry != path->mnt->mnt_root)
Christoph Hellwig25ccd24f2020-08-06 16:07:10 +02001721 return -EINVAL;
Al Viro143c8c92011-11-25 00:46:35 -05001722 if (!check_mnt(mnt))
Christoph Hellwig25ccd24f2020-08-06 16:07:10 +02001723 return -EINVAL;
Eric W. Biederman25d202e2018-10-22 10:21:38 -05001724 if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
Christoph Hellwig25ccd24f2020-08-06 16:07:10 +02001725 return -EINVAL;
Eric W. Biedermanb2f5d4d2014-10-04 14:44:03 -07001726 if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
Christoph Hellwig25ccd24f2020-08-06 16:07:10 +02001727 return -EPERM;
1728 return 0;
1729}
Linus Torvalds1da177e2005-04-16 15:20:36 -07001730
Christoph Hellwig25ccd24f2020-08-06 16:07:10 +02001731int path_umount(struct path *path, int flags)
1732{
1733 struct mount *mnt = real_mount(path->mnt);
1734 int ret;
1735
1736 ret = can_umount(path, flags);
1737 if (!ret)
1738 ret = do_umount(mnt, flags);
1739
Jan Blunck429731b2008-02-14 19:34:31 -08001740 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
Christoph Hellwig41525f52020-07-21 10:54:34 +02001741 dput(path->dentry);
Al Viro900148d2011-11-25 00:33:11 -05001742 mntput_no_expire(mnt);
Christoph Hellwig25ccd24f2020-08-06 16:07:10 +02001743 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001744}
1745
Christoph Hellwig09267de2020-07-23 08:23:08 +02001746static int ksys_umount(char __user *name, int flags)
Christoph Hellwig41525f52020-07-21 10:54:34 +02001747{
1748 int lookup_flags = LOOKUP_MOUNTPOINT;
1749 struct path path;
1750 int ret;
1751
1752 if (!(flags & UMOUNT_NOFOLLOW))
1753 lookup_flags |= LOOKUP_FOLLOW;
1754 ret = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1755 if (ret)
1756 return ret;
1757 return path_umount(&path, flags);
1758}
1759
Dominik Brodowski3a18ef52018-03-11 11:34:40 +01001760SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1761{
1762 return ksys_umount(name, flags);
1763}
1764
Linus Torvalds1da177e2005-04-16 15:20:36 -07001765#ifdef __ARCH_WANT_SYS_OLDUMOUNT
1766
1767/*
Ram Paib58fed82005-11-07 17:16:09 -05001768 * The 2.0 compatible umount. No flags.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001769 */
Heiko Carstensbdc480e2009-01-14 14:14:12 +01001770SYSCALL_DEFINE1(oldumount, char __user *, name)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001771{
Dominik Brodowski3a18ef52018-03-11 11:34:40 +01001772 return ksys_umount(name, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001773}
1774
1775#endif
1776
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07001777static bool is_mnt_ns_file(struct dentry *dentry)
Eric W. Biederman8823c072010-03-07 18:49:36 -08001778{
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07001779 /* Is this a proxy for a mount namespace? */
Al Viroe149ed22014-11-01 10:57:28 -04001780 return dentry->d_op == &ns_dentry_operations &&
1781 dentry->d_fsdata == &mntns_operations;
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07001782}
1783
Eric Biggers213921f2020-01-04 12:59:55 -08001784static struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
Al Viro58be28252014-11-01 00:00:23 -04001785{
1786 return container_of(ns, struct mnt_namespace, ns);
1787}
1788
Christian Brauner303cc572020-05-05 16:04:31 +02001789struct ns_common *from_mnt_ns(struct mnt_namespace *mnt)
1790{
1791 return &mnt->ns;
1792}
1793
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07001794static bool mnt_ns_loop(struct dentry *dentry)
1795{
1796 /* Could bind mounting the mount namespace inode cause a
1797 * mount namespace loop?
1798 */
1799 struct mnt_namespace *mnt_ns;
1800 if (!is_mnt_ns_file(dentry))
1801 return false;
1802
Al Virof77c8012014-11-01 03:13:17 -04001803 mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
Eric W. Biederman8823c072010-03-07 18:49:36 -08001804 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1805}
1806
Al Viro87129cc2011-11-24 21:24:27 -05001807struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
Ram Pai36341f62005-11-07 17:17:22 -05001808 int flag)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001809{
Al Viro84d17192013-03-15 10:53:28 -04001810 struct mount *res, *p, *q, *r, *parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07001812 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1813 return ERR_PTR(-EINVAL);
1814
1815 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
David Howellsbe34d1a2012-06-25 12:55:18 +01001816 return ERR_PTR(-EINVAL);
Ram Pai9676f0c2005-11-07 17:21:20 -05001817
Ram Pai36341f62005-11-07 17:17:22 -05001818 res = q = clone_mnt(mnt, dentry, flag);
David Howellsbe34d1a2012-06-25 12:55:18 +01001819 if (IS_ERR(q))
1820 return q;
1821
Al Viroa73324d2011-11-24 22:25:07 -05001822 q->mnt_mountpoint = mnt->mnt_mountpoint;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001823
1824 p = mnt;
Al Viro6b41d532011-11-24 23:24:33 -05001825 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
Al Viro315fc832011-11-24 18:57:30 -05001826 struct mount *s;
Jan Blunck7ec02ef2008-04-29 00:59:40 -07001827 if (!is_subdir(r->mnt_mountpoint, dentry))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828 continue;
1829
Al Viro909b0a82011-11-25 03:06:56 -05001830 for (s = r; s; s = next_mnt(s, r)) {
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07001831 if (!(flag & CL_COPY_UNBINDABLE) &&
1832 IS_MNT_UNBINDABLE(s)) {
Eric W. Biedermandf7342b2018-10-25 09:04:18 -05001833 if (s->mnt.mnt_flags & MNT_LOCKED) {
1834 /* Both unbindable and locked. */
1835 q = ERR_PTR(-EPERM);
1836 goto out;
1837 } else {
1838 s = skip_mnt_tree(s);
1839 continue;
1840 }
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07001841 }
1842 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1843 is_mnt_ns_file(s->mnt.mnt_root)) {
Ram Pai9676f0c2005-11-07 17:21:20 -05001844 s = skip_mnt_tree(s);
1845 continue;
1846 }
Al Viro0714a532011-11-24 22:19:58 -05001847 while (p != s->mnt_parent) {
1848 p = p->mnt_parent;
1849 q = q->mnt_parent;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001850 }
Al Viro87129cc2011-11-24 21:24:27 -05001851 p = s;
Al Viro84d17192013-03-15 10:53:28 -04001852 parent = q;
Al Viro87129cc2011-11-24 21:24:27 -05001853 q = clone_mnt(p, p->mnt.mnt_root, flag);
David Howellsbe34d1a2012-06-25 12:55:18 +01001854 if (IS_ERR(q))
1855 goto out;
Al Viro719ea2f2013-09-29 11:24:49 -04001856 lock_mount_hash();
Al Viro1a4eeaf2011-11-25 02:19:55 -05001857 list_add_tail(&q->mnt_list, &res->mnt_list);
Eric W. Biederman1064f872017-01-20 18:28:35 +13001858 attach_mnt(q, parent, p->mnt_mp);
Al Viro719ea2f2013-09-29 11:24:49 -04001859 unlock_mount_hash();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860 }
1861 }
1862 return res;
David Howellsbe34d1a2012-06-25 12:55:18 +01001863out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001864 if (res) {
Al Viro719ea2f2013-09-29 11:24:49 -04001865 lock_mount_hash();
Eric W. Biedermane819f152014-12-24 07:20:01 -06001866 umount_tree(res, UMOUNT_SYNC);
Al Viro719ea2f2013-09-29 11:24:49 -04001867 unlock_mount_hash();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868 }
David Howellsbe34d1a2012-06-25 12:55:18 +01001869 return q;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001870}
1871
David Howellsbe34d1a2012-06-25 12:55:18 +01001872/* Caller should check returned pointer for errors */
1873
Al Viroca71cf72016-11-20 19:45:28 -05001874struct vfsmount *collect_mounts(const struct path *path)
Al Viro8aec0802007-06-07 12:20:32 -04001875{
Al Virocb338d02011-11-24 20:55:08 -05001876 struct mount *tree;
Al Viro97216be2013-03-16 15:12:40 -04001877 namespace_lock();
Eric W. Biedermancd4a4012015-01-07 14:28:26 -06001878 if (!check_mnt(real_mount(path->mnt)))
1879 tree = ERR_PTR(-EINVAL);
1880 else
1881 tree = copy_tree(real_mount(path->mnt), path->dentry,
1882 CL_COPY_ALL | CL_PRIVATE);
Al Viro328e6d92013-03-16 14:49:45 -04001883 namespace_unlock();
David Howellsbe34d1a2012-06-25 12:55:18 +01001884 if (IS_ERR(tree))
Dan Carpenter52e220d2013-08-14 12:44:39 +03001885 return ERR_CAST(tree);
David Howellsbe34d1a2012-06-25 12:55:18 +01001886 return &tree->mnt;
Al Viro8aec0802007-06-07 12:20:32 -04001887}
1888
Al Viroa07b2002018-11-05 17:40:30 +00001889static void free_mnt_ns(struct mnt_namespace *);
1890static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool);
1891
1892void dissolve_on_fput(struct vfsmount *mnt)
1893{
1894 struct mnt_namespace *ns;
1895 namespace_lock();
1896 lock_mount_hash();
1897 ns = real_mount(mnt)->mnt_ns;
David Howells44dfd842018-11-05 17:40:31 +00001898 if (ns) {
1899 if (is_anon_ns(ns))
1900 umount_tree(real_mount(mnt), UMOUNT_CONNECTED);
1901 else
1902 ns = NULL;
1903 }
Al Viroa07b2002018-11-05 17:40:30 +00001904 unlock_mount_hash();
1905 namespace_unlock();
David Howells44dfd842018-11-05 17:40:31 +00001906 if (ns)
1907 free_mnt_ns(ns);
Al Viroa07b2002018-11-05 17:40:30 +00001908}
1909
Al Viro8aec0802007-06-07 12:20:32 -04001910void drop_collected_mounts(struct vfsmount *mnt)
1911{
Al Viro97216be2013-03-16 15:12:40 -04001912 namespace_lock();
Al Viro719ea2f2013-09-29 11:24:49 -04001913 lock_mount_hash();
Eric W. Biederman9c8e0a12018-10-25 12:05:11 -05001914 umount_tree(real_mount(mnt), 0);
Al Viro719ea2f2013-09-29 11:24:49 -04001915 unlock_mount_hash();
Al Viro3ab6abe2013-03-16 14:42:19 -04001916 namespace_unlock();
Al Viro8aec0802007-06-07 12:20:32 -04001917}
1918
Miklos Szeredic771d682014-10-24 00:14:36 +02001919/**
1920 * clone_private_mount - create a private clone of a path
1921 *
1922 * This creates a new vfsmount, which will be the clone of @path. The new will
1923 * not be attached anywhere in the namespace and will be private (i.e. changes
1924 * to the originating mount won't be propagated into this).
1925 *
1926 * Release with mntput().
1927 */
Al Viroca71cf72016-11-20 19:45:28 -05001928struct vfsmount *clone_private_mount(const struct path *path)
Miklos Szeredic771d682014-10-24 00:14:36 +02001929{
1930 struct mount *old_mnt = real_mount(path->mnt);
1931 struct mount *new_mnt;
1932
1933 if (IS_MNT_UNBINDABLE(old_mnt))
1934 return ERR_PTR(-EINVAL);
1935
Miklos Szeredic771d682014-10-24 00:14:36 +02001936 new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
Miklos Szeredic771d682014-10-24 00:14:36 +02001937 if (IS_ERR(new_mnt))
1938 return ERR_CAST(new_mnt);
1939
Miklos Szeredidf820f82020-06-04 10:48:19 +02001940 /* Longterm mount to be removed by kern_unmount*() */
1941 new_mnt->mnt_ns = MNT_NS_INTERNAL;
1942
Miklos Szeredic771d682014-10-24 00:14:36 +02001943 return &new_mnt->mnt;
1944}
1945EXPORT_SYMBOL_GPL(clone_private_mount);
1946
Al Viro1f707132010-01-30 22:51:25 -05001947int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1948 struct vfsmount *root)
1949{
Al Viro1a4eeaf2011-11-25 02:19:55 -05001950 struct mount *mnt;
Al Viro1f707132010-01-30 22:51:25 -05001951 int res = f(root, arg);
1952 if (res)
1953 return res;
Al Viro1a4eeaf2011-11-25 02:19:55 -05001954 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1955 res = f(&mnt->mnt, arg);
Al Viro1f707132010-01-30 22:51:25 -05001956 if (res)
1957 return res;
1958 }
1959 return 0;
1960}
1961
Al Viro3bd045c2019-01-30 13:15:45 -05001962static void lock_mnt_tree(struct mount *mnt)
1963{
1964 struct mount *p;
1965
1966 for (p = mnt; p; p = next_mnt(p, mnt)) {
1967 int flags = p->mnt.mnt_flags;
1968 /* Don't allow unprivileged users to change mount flags */
1969 flags |= MNT_LOCK_ATIME;
1970
1971 if (flags & MNT_READONLY)
1972 flags |= MNT_LOCK_READONLY;
1973
1974 if (flags & MNT_NODEV)
1975 flags |= MNT_LOCK_NODEV;
1976
1977 if (flags & MNT_NOSUID)
1978 flags |= MNT_LOCK_NOSUID;
1979
1980 if (flags & MNT_NOEXEC)
1981 flags |= MNT_LOCK_NOEXEC;
1982 /* Don't allow unprivileged users to reveal what is under a mount */
1983 if (list_empty(&p->mnt_expire))
1984 flags |= MNT_LOCKED;
1985 p->mnt.mnt_flags = flags;
1986 }
1987}
1988
Al Viro4b8b21f2011-11-24 19:54:23 -05001989static void cleanup_group_ids(struct mount *mnt, struct mount *end)
Miklos Szeredi719f5d72008-03-27 13:06:23 +01001990{
Al Viro315fc832011-11-24 18:57:30 -05001991 struct mount *p;
Miklos Szeredi719f5d72008-03-27 13:06:23 +01001992
Al Viro909b0a82011-11-25 03:06:56 -05001993 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
Al Virofc7be132011-11-25 01:05:37 -05001994 if (p->mnt_group_id && !IS_MNT_SHARED(p))
Al Viro4b8b21f2011-11-24 19:54:23 -05001995 mnt_release_group_id(p);
Miklos Szeredi719f5d72008-03-27 13:06:23 +01001996 }
1997}
1998
Al Viro4b8b21f2011-11-24 19:54:23 -05001999static int invent_group_ids(struct mount *mnt, bool recurse)
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002000{
Al Viro315fc832011-11-24 18:57:30 -05002001 struct mount *p;
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002002
Al Viro909b0a82011-11-25 03:06:56 -05002003 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
Al Virofc7be132011-11-25 01:05:37 -05002004 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
Al Viro4b8b21f2011-11-24 19:54:23 -05002005 int err = mnt_alloc_group_id(p);
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002006 if (err) {
Al Viro4b8b21f2011-11-24 19:54:23 -05002007 cleanup_group_ids(mnt, p);
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002008 return err;
2009 }
2010 }
2011 }
2012
2013 return 0;
2014}
2015
Eric W. Biedermand2921682016-09-28 00:27:17 -05002016int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
2017{
2018 unsigned int max = READ_ONCE(sysctl_mount_max);
2019 unsigned int mounts = 0, old, pending, sum;
2020 struct mount *p;
2021
2022 for (p = mnt; p; p = next_mnt(p, mnt))
2023 mounts++;
2024
2025 old = ns->mounts;
2026 pending = ns->pending_mounts;
2027 sum = old + pending;
2028 if ((old > sum) ||
2029 (pending > sum) ||
2030 (max < sum) ||
2031 (mounts > (max - sum)))
2032 return -ENOSPC;
2033
2034 ns->pending_mounts = pending + mounts;
2035 return 0;
2036}
2037
Ram Paib90fa9a2005-11-07 17:19:50 -05002038/*
2039 * @source_mnt : mount tree to be attached
Ram Pai21444402005-11-07 17:20:03 -05002040 * @nd : place the mount tree @source_mnt is attached
2041 * @parent_nd : if non-null, detach the source_mnt from its parent and
2042 * store the parent mount and mountpoint dentry.
2043 * (done when source_mnt is moved)
Ram Paib90fa9a2005-11-07 17:19:50 -05002044 *
2045 * NOTE: in the table below explains the semantics when a source mount
2046 * of a given type is attached to a destination mount of a given type.
Ram Pai9676f0c2005-11-07 17:21:20 -05002047 * ---------------------------------------------------------------------------
2048 * | BIND MOUNT OPERATION |
2049 * |**************************************************************************
2050 * | source-->| shared | private | slave | unbindable |
2051 * | dest | | | | |
2052 * | | | | | | |
2053 * | v | | | | |
2054 * |**************************************************************************
2055 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
2056 * | | | | | |
2057 * |non-shared| shared (+) | private | slave (*) | invalid |
2058 * ***************************************************************************
Ram Paib90fa9a2005-11-07 17:19:50 -05002059 * A bind operation clones the source mount and mounts the clone on the
2060 * destination mount.
2061 *
2062 * (++) the cloned mount is propagated to all the mounts in the propagation
2063 * tree of the destination mount and the cloned mount is added to
2064 * the peer group of the source mount.
2065 * (+) the cloned mount is created under the destination mount and is marked
2066 * as shared. The cloned mount is added to the peer group of the source
2067 * mount.
Ram Pai5afe0022005-11-07 17:21:01 -05002068 * (+++) the mount is propagated to all the mounts in the propagation tree
2069 * of the destination mount and the cloned mount is made slave
2070 * of the same master as that of the source mount. The cloned mount
2071 * is marked as 'shared and slave'.
2072 * (*) the cloned mount is made a slave of the same master as that of the
2073 * source mount.
2074 *
Ram Pai9676f0c2005-11-07 17:21:20 -05002075 * ---------------------------------------------------------------------------
2076 * | MOVE MOUNT OPERATION |
2077 * |**************************************************************************
2078 * | source-->| shared | private | slave | unbindable |
2079 * | dest | | | | |
2080 * | | | | | | |
2081 * | v | | | | |
2082 * |**************************************************************************
2083 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2084 * | | | | | |
2085 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2086 * ***************************************************************************
Ram Pai5afe0022005-11-07 17:21:01 -05002087 *
2088 * (+) the mount is moved to the destination. And is then propagated to
2089 * all the mounts in the propagation tree of the destination mount.
Ram Pai21444402005-11-07 17:20:03 -05002090 * (+*) the mount is moved to the destination.
Ram Pai5afe0022005-11-07 17:21:01 -05002091 * (+++) the mount is moved to the destination and is then propagated to
2092 * all the mounts belonging to the destination mount's propagation tree.
2093 * the mount is marked as 'shared and slave'.
2094 * (*) the mount continues to be a slave at the new location.
Ram Paib90fa9a2005-11-07 17:19:50 -05002095 *
2096 * if the source mount is a tree, the operations explained above is
2097 * applied to each mount in the tree.
2098 * Must be called without spinlocks held, since this function can sleep
2099 * in allocations.
2100 */
Al Viro0fb54e52011-11-24 19:59:16 -05002101static int attach_recursive_mnt(struct mount *source_mnt,
Al Viro84d17192013-03-15 10:53:28 -04002102 struct mount *dest_mnt,
2103 struct mountpoint *dest_mp,
Al Viro2763d112019-06-30 19:18:53 -04002104 bool moving)
Ram Paib90fa9a2005-11-07 17:19:50 -05002105{
Al Viro3bd045c2019-01-30 13:15:45 -05002106 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
Al Viro38129a12014-03-20 21:10:51 -04002107 HLIST_HEAD(tree_list);
Eric W. Biedermand2921682016-09-28 00:27:17 -05002108 struct mnt_namespace *ns = dest_mnt->mnt_ns;
Eric W. Biederman1064f872017-01-20 18:28:35 +13002109 struct mountpoint *smp;
Al Viro315fc832011-11-24 18:57:30 -05002110 struct mount *child, *p;
Al Viro38129a12014-03-20 21:10:51 -04002111 struct hlist_node *n;
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002112 int err;
Ram Paib90fa9a2005-11-07 17:19:50 -05002113
Eric W. Biederman1064f872017-01-20 18:28:35 +13002114 /* Preallocate a mountpoint in case the new mounts need
2115 * to be tucked under other mounts.
2116 */
2117 smp = get_mountpoint(source_mnt->mnt.mnt_root);
2118 if (IS_ERR(smp))
2119 return PTR_ERR(smp);
2120
Eric W. Biedermand2921682016-09-28 00:27:17 -05002121 /* Is there space to add these mounts to the mount namespace? */
Al Viro2763d112019-06-30 19:18:53 -04002122 if (!moving) {
Eric W. Biedermand2921682016-09-28 00:27:17 -05002123 err = count_mounts(ns, source_mnt);
2124 if (err)
2125 goto out;
2126 }
2127
Al Virofc7be132011-11-25 01:05:37 -05002128 if (IS_MNT_SHARED(dest_mnt)) {
Al Viro0fb54e52011-11-24 19:59:16 -05002129 err = invent_group_ids(source_mnt, true);
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002130 if (err)
2131 goto out;
Al Viro0b1b9012014-03-21 10:14:08 -04002132 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
Al Virof2ebb3a2014-02-27 09:35:45 -05002133 lock_mount_hash();
Al Viro0b1b9012014-03-21 10:14:08 -04002134 if (err)
2135 goto out_cleanup_ids;
Al Viro909b0a82011-11-25 03:06:56 -05002136 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
Al Viro0f0afb12011-11-24 20:43:10 -05002137 set_mnt_shared(p);
Al Viro0b1b9012014-03-21 10:14:08 -04002138 } else {
2139 lock_mount_hash();
Ram Paib90fa9a2005-11-07 17:19:50 -05002140 }
Al Viro2763d112019-06-30 19:18:53 -04002141 if (moving) {
2142 unhash_mnt(source_mnt);
Al Viro84d17192013-03-15 10:53:28 -04002143 attach_mnt(source_mnt, dest_mnt, dest_mp);
Al Viro143c8c92011-11-25 00:46:35 -05002144 touch_mnt_namespace(source_mnt->mnt_ns);
Ram Pai21444402005-11-07 17:20:03 -05002145 } else {
David Howells44dfd842018-11-05 17:40:31 +00002146 if (source_mnt->mnt_ns) {
2147 /* move from anon - the caller will destroy */
2148 list_del_init(&source_mnt->mnt_ns->list);
2149 }
Al Viro84d17192013-03-15 10:53:28 -04002150 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
Eric W. Biederman1064f872017-01-20 18:28:35 +13002151 commit_tree(source_mnt);
Ram Pai21444402005-11-07 17:20:03 -05002152 }
Ram Paib90fa9a2005-11-07 17:19:50 -05002153
Al Viro38129a12014-03-20 21:10:51 -04002154 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
Al Viro1d6a32a2014-03-20 20:34:43 -04002155 struct mount *q;
Al Viro38129a12014-03-20 21:10:51 -04002156 hlist_del_init(&child->mnt_hash);
Eric W. Biederman1064f872017-01-20 18:28:35 +13002157 q = __lookup_mnt(&child->mnt_parent->mnt,
2158 child->mnt_mountpoint);
2159 if (q)
2160 mnt_change_mountpoint(child, smp, q);
Al Viro3bd045c2019-01-30 13:15:45 -05002161 /* Notice when we are propagating across user namespaces */
2162 if (child->mnt_parent->mnt_ns->user_ns != user_ns)
2163 lock_mnt_tree(child);
Christian Braunerd728cf72019-06-17 23:22:14 +02002164 child->mnt.mnt_flags &= ~MNT_LOCKED;
Eric W. Biederman1064f872017-01-20 18:28:35 +13002165 commit_tree(child);
Ram Paib90fa9a2005-11-07 17:19:50 -05002166 }
Eric W. Biederman1064f872017-01-20 18:28:35 +13002167 put_mountpoint(smp);
Al Viro719ea2f2013-09-29 11:24:49 -04002168 unlock_mount_hash();
Nick Piggin99b7db72010-08-18 04:37:39 +10002169
Ram Paib90fa9a2005-11-07 17:19:50 -05002170 return 0;
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002171
2172 out_cleanup_ids:
Al Virof2ebb3a2014-02-27 09:35:45 -05002173 while (!hlist_empty(&tree_list)) {
2174 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
Eric W. Biedermand2921682016-09-28 00:27:17 -05002175 child->mnt_parent->mnt_ns->pending_mounts = 0;
Eric W. Biedermane819f152014-12-24 07:20:01 -06002176 umount_tree(child, UMOUNT_SYNC);
Al Virof2ebb3a2014-02-27 09:35:45 -05002177 }
2178 unlock_mount_hash();
Al Viro0b1b9012014-03-21 10:14:08 -04002179 cleanup_group_ids(source_mnt, NULL);
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002180 out:
Eric W. Biedermand2921682016-09-28 00:27:17 -05002181 ns->pending_mounts = 0;
Eric W. Biederman1064f872017-01-20 18:28:35 +13002182
2183 read_seqlock_excl(&mount_lock);
2184 put_mountpoint(smp);
2185 read_sequnlock_excl(&mount_lock);
2186
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002187 return err;
Ram Paib90fa9a2005-11-07 17:19:50 -05002188}
2189
Al Viro84d17192013-03-15 10:53:28 -04002190static struct mountpoint *lock_mount(struct path *path)
Al Virob12cea92011-03-18 08:55:38 -04002191{
2192 struct vfsmount *mnt;
Al Viro84d17192013-03-15 10:53:28 -04002193 struct dentry *dentry = path->dentry;
Al Virob12cea92011-03-18 08:55:38 -04002194retry:
Al Viro59551022016-01-22 15:40:57 -05002195 inode_lock(dentry->d_inode);
Al Viro84d17192013-03-15 10:53:28 -04002196 if (unlikely(cant_mount(dentry))) {
Al Viro59551022016-01-22 15:40:57 -05002197 inode_unlock(dentry->d_inode);
Al Viro84d17192013-03-15 10:53:28 -04002198 return ERR_PTR(-ENOENT);
Al Virob12cea92011-03-18 08:55:38 -04002199 }
Al Viro97216be2013-03-16 15:12:40 -04002200 namespace_lock();
Al Virob12cea92011-03-18 08:55:38 -04002201 mnt = lookup_mnt(path);
Al Viro84d17192013-03-15 10:53:28 -04002202 if (likely(!mnt)) {
Eric W. Biederman3895dbf2017-01-03 14:18:43 +13002203 struct mountpoint *mp = get_mountpoint(dentry);
Al Viro84d17192013-03-15 10:53:28 -04002204 if (IS_ERR(mp)) {
Al Viro97216be2013-03-16 15:12:40 -04002205 namespace_unlock();
Al Viro59551022016-01-22 15:40:57 -05002206 inode_unlock(dentry->d_inode);
Al Viro84d17192013-03-15 10:53:28 -04002207 return mp;
2208 }
2209 return mp;
2210 }
Al Viro97216be2013-03-16 15:12:40 -04002211 namespace_unlock();
Al Viro59551022016-01-22 15:40:57 -05002212 inode_unlock(path->dentry->d_inode);
Al Virob12cea92011-03-18 08:55:38 -04002213 path_put(path);
2214 path->mnt = mnt;
Al Viro84d17192013-03-15 10:53:28 -04002215 dentry = path->dentry = dget(mnt->mnt_root);
Al Virob12cea92011-03-18 08:55:38 -04002216 goto retry;
2217}
2218
Al Viro84d17192013-03-15 10:53:28 -04002219static void unlock_mount(struct mountpoint *where)
Al Virob12cea92011-03-18 08:55:38 -04002220{
Al Viro84d17192013-03-15 10:53:28 -04002221 struct dentry *dentry = where->m_dentry;
Eric W. Biederman3895dbf2017-01-03 14:18:43 +13002222
2223 read_seqlock_excl(&mount_lock);
Al Viro84d17192013-03-15 10:53:28 -04002224 put_mountpoint(where);
Eric W. Biederman3895dbf2017-01-03 14:18:43 +13002225 read_sequnlock_excl(&mount_lock);
2226
Al Viro328e6d92013-03-16 14:49:45 -04002227 namespace_unlock();
Al Viro59551022016-01-22 15:40:57 -05002228 inode_unlock(dentry->d_inode);
Al Virob12cea92011-03-18 08:55:38 -04002229}
2230
Al Viro84d17192013-03-15 10:53:28 -04002231static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002232{
David Howellse462ec52017-07-17 08:45:35 +01002233 if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002234 return -EINVAL;
2235
David Howellse36cb0b2015-01-29 12:02:35 +00002236 if (d_is_dir(mp->m_dentry) !=
2237 d_is_dir(mnt->mnt.mnt_root))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002238 return -ENOTDIR;
2239
Al Viro2763d112019-06-30 19:18:53 -04002240 return attach_recursive_mnt(mnt, p, mp, false);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002241}
2242
2243/*
Valerie Aurora7a2e8a82010-08-26 11:07:22 -07002244 * Sanity check the flags to change_mnt_propagation.
2245 */
2246
David Howellse462ec52017-07-17 08:45:35 +01002247static int flags_to_propagation_type(int ms_flags)
Valerie Aurora7a2e8a82010-08-26 11:07:22 -07002248{
David Howellse462ec52017-07-17 08:45:35 +01002249 int type = ms_flags & ~(MS_REC | MS_SILENT);
Valerie Aurora7a2e8a82010-08-26 11:07:22 -07002250
2251 /* Fail if any non-propagation flags are set */
2252 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2253 return 0;
2254 /* Only one propagation flag should be set */
2255 if (!is_power_of_2(type))
2256 return 0;
2257 return type;
2258}
2259
2260/*
Ram Pai07b20882005-11-07 17:19:07 -05002261 * recursively change the type of the mountpoint.
2262 */
David Howellse462ec52017-07-17 08:45:35 +01002263static int do_change_type(struct path *path, int ms_flags)
Ram Pai07b20882005-11-07 17:19:07 -05002264{
Al Viro315fc832011-11-24 18:57:30 -05002265 struct mount *m;
Al Viro4b8b21f2011-11-24 19:54:23 -05002266 struct mount *mnt = real_mount(path->mnt);
David Howellse462ec52017-07-17 08:45:35 +01002267 int recurse = ms_flags & MS_REC;
Valerie Aurora7a2e8a82010-08-26 11:07:22 -07002268 int type;
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002269 int err = 0;
Ram Pai07b20882005-11-07 17:19:07 -05002270
Al Viro2d92ab32008-08-02 00:51:11 -04002271 if (path->dentry != path->mnt->mnt_root)
Ram Pai07b20882005-11-07 17:19:07 -05002272 return -EINVAL;
2273
David Howellse462ec52017-07-17 08:45:35 +01002274 type = flags_to_propagation_type(ms_flags);
Valerie Aurora7a2e8a82010-08-26 11:07:22 -07002275 if (!type)
2276 return -EINVAL;
2277
Al Viro97216be2013-03-16 15:12:40 -04002278 namespace_lock();
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002279 if (type == MS_SHARED) {
2280 err = invent_group_ids(mnt, recurse);
2281 if (err)
2282 goto out_unlock;
2283 }
2284
Al Viro719ea2f2013-09-29 11:24:49 -04002285 lock_mount_hash();
Al Viro909b0a82011-11-25 03:06:56 -05002286 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
Al Viro0f0afb12011-11-24 20:43:10 -05002287 change_mnt_propagation(m, type);
Al Viro719ea2f2013-09-29 11:24:49 -04002288 unlock_mount_hash();
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002289
2290 out_unlock:
Al Viro97216be2013-03-16 15:12:40 -04002291 namespace_unlock();
Miklos Szeredi719f5d72008-03-27 13:06:23 +01002292 return err;
Ram Pai07b20882005-11-07 17:19:07 -05002293}
2294
Eric W. Biederman5ff9d8a2013-03-29 21:04:39 -07002295static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
2296{
2297 struct mount *child;
2298 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2299 if (!is_subdir(child->mnt_mountpoint, dentry))
2300 continue;
2301
2302 if (child->mnt.mnt_flags & MNT_LOCKED)
2303 return true;
2304 }
2305 return false;
2306}
2307
Al Viroa07b2002018-11-05 17:40:30 +00002308static struct mount *__do_loopback(struct path *old_path, int recurse)
2309{
2310 struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt);
2311
2312 if (IS_MNT_UNBINDABLE(old))
2313 return mnt;
2314
2315 if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations)
2316 return mnt;
2317
2318 if (!recurse && has_locked_children(old, old_path->dentry))
2319 return mnt;
2320
2321 if (recurse)
2322 mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE);
2323 else
2324 mnt = clone_mnt(old, old_path->dentry, 0);
2325
2326 if (!IS_ERR(mnt))
2327 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2328
2329 return mnt;
2330}
2331
Ram Pai07b20882005-11-07 17:19:07 -05002332/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002333 * do loopback mount.
2334 */
Al Viro808d4e32012-10-11 11:42:01 -04002335static int do_loopback(struct path *path, const char *old_name,
Eric Sandeen2dafe1c2008-02-08 04:22:12 -08002336 int recurse)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002337{
Al Viro2d92ab32008-08-02 00:51:11 -04002338 struct path old_path;
Al Viroa07b2002018-11-05 17:40:30 +00002339 struct mount *mnt = NULL, *parent;
Al Viro84d17192013-03-15 10:53:28 -04002340 struct mountpoint *mp;
Al Viro57eccb82013-02-22 22:49:10 -05002341 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002342 if (!old_name || !*old_name)
2343 return -EINVAL;
Trond Myklebust815d4052011-09-26 20:36:09 -04002344 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002345 if (err)
2346 return err;
2347
Eric W. Biederman8823c072010-03-07 18:49:36 -08002348 err = -EINVAL;
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07002349 if (mnt_ns_loop(old_path.dentry))
David Howellsdd111b32017-07-04 17:25:09 +01002350 goto out;
Eric W. Biederman8823c072010-03-07 18:49:36 -08002351
Al Viro84d17192013-03-15 10:53:28 -04002352 mp = lock_mount(path);
Al Viroa07b2002018-11-05 17:40:30 +00002353 if (IS_ERR(mp)) {
2354 err = PTR_ERR(mp);
Jan Blunck4ac91372008-02-14 19:34:32 -08002355 goto out;
Al Viroa07b2002018-11-05 17:40:30 +00002356 }
Ram Pai9676f0c2005-11-07 17:21:20 -05002357
Al Viro84d17192013-03-15 10:53:28 -04002358 parent = real_mount(path->mnt);
Al Viroe149ed22014-11-01 10:57:28 -04002359 if (!check_mnt(parent))
2360 goto out2;
2361
Al Viroa07b2002018-11-05 17:40:30 +00002362 mnt = __do_loopback(&old_path, recurse);
David Howellsbe34d1a2012-06-25 12:55:18 +01002363 if (IS_ERR(mnt)) {
2364 err = PTR_ERR(mnt);
Andrey Vagine9c5d8a2013-04-09 17:33:29 +04002365 goto out2;
David Howellsbe34d1a2012-06-25 12:55:18 +01002366 }
Al Viroccd48bc2005-11-07 17:15:04 -05002367
Al Viro84d17192013-03-15 10:53:28 -04002368 err = graft_tree(mnt, parent, mp);
Al Viroccd48bc2005-11-07 17:15:04 -05002369 if (err) {
Al Viro719ea2f2013-09-29 11:24:49 -04002370 lock_mount_hash();
Eric W. Biedermane819f152014-12-24 07:20:01 -06002371 umount_tree(mnt, UMOUNT_SYNC);
Al Viro719ea2f2013-09-29 11:24:49 -04002372 unlock_mount_hash();
Ram Pai5b83d2c5c2005-11-07 17:16:29 -05002373 }
Al Virob12cea92011-03-18 08:55:38 -04002374out2:
Al Viro84d17192013-03-15 10:53:28 -04002375 unlock_mount(mp);
Al Viroccd48bc2005-11-07 17:15:04 -05002376out:
Al Viro2d92ab32008-08-02 00:51:11 -04002377 path_put(&old_path);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002378 return err;
2379}
2380
Al Viroa07b2002018-11-05 17:40:30 +00002381static struct file *open_detached_copy(struct path *path, bool recursive)
2382{
2383 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2384 struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true);
2385 struct mount *mnt, *p;
2386 struct file *file;
2387
2388 if (IS_ERR(ns))
2389 return ERR_CAST(ns);
2390
2391 namespace_lock();
2392 mnt = __do_loopback(path, recursive);
2393 if (IS_ERR(mnt)) {
2394 namespace_unlock();
2395 free_mnt_ns(ns);
2396 return ERR_CAST(mnt);
2397 }
2398
2399 lock_mount_hash();
2400 for (p = mnt; p; p = next_mnt(p, mnt)) {
2401 p->mnt_ns = ns;
2402 ns->mounts++;
2403 }
2404 ns->root = mnt;
2405 list_add_tail(&ns->list, &mnt->mnt_list);
2406 mntget(&mnt->mnt);
2407 unlock_mount_hash();
2408 namespace_unlock();
2409
2410 mntput(path->mnt);
2411 path->mnt = &mnt->mnt;
2412 file = dentry_open(path, O_PATH, current_cred());
2413 if (IS_ERR(file))
2414 dissolve_on_fput(path->mnt);
2415 else
2416 file->f_mode |= FMODE_NEED_UNMOUNT;
2417 return file;
2418}
2419
Ben Dooks2658ce02019-10-15 11:35:02 +01002420SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags)
Al Viroa07b2002018-11-05 17:40:30 +00002421{
2422 struct file *file;
2423 struct path path;
2424 int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
2425 bool detached = flags & OPEN_TREE_CLONE;
2426 int error;
2427 int fd;
2428
2429 BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC);
2430
2431 if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE |
2432 AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE |
2433 OPEN_TREE_CLOEXEC))
2434 return -EINVAL;
2435
2436 if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE)
2437 return -EINVAL;
2438
2439 if (flags & AT_NO_AUTOMOUNT)
2440 lookup_flags &= ~LOOKUP_AUTOMOUNT;
2441 if (flags & AT_SYMLINK_NOFOLLOW)
2442 lookup_flags &= ~LOOKUP_FOLLOW;
2443 if (flags & AT_EMPTY_PATH)
2444 lookup_flags |= LOOKUP_EMPTY;
2445
2446 if (detached && !may_mount())
2447 return -EPERM;
2448
2449 fd = get_unused_fd_flags(flags & O_CLOEXEC);
2450 if (fd < 0)
2451 return fd;
2452
2453 error = user_path_at(dfd, filename, lookup_flags, &path);
2454 if (unlikely(error)) {
2455 file = ERR_PTR(error);
2456 } else {
2457 if (detached)
2458 file = open_detached_copy(&path, flags & AT_RECURSIVE);
2459 else
2460 file = dentry_open(&path, O_PATH, current_cred());
2461 path_put(&path);
2462 }
2463 if (IS_ERR(file)) {
2464 put_unused_fd(fd);
2465 return PTR_ERR(file);
2466 }
2467 fd_install(fd, file);
2468 return fd;
2469}
2470
David Howells43f5e652018-11-01 23:07:25 +00002471/*
2472 * Don't allow locked mount flags to be cleared.
2473 *
2474 * No locks need to be held here while testing the various MNT_LOCK
2475 * flags because those flags can never be cleared once they are set.
2476 */
2477static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags)
Dave Hansen2e4b7fc2008-02-15 14:38:00 -08002478{
David Howells43f5e652018-11-01 23:07:25 +00002479 unsigned int fl = mnt->mnt.mnt_flags;
Dave Hansen2e4b7fc2008-02-15 14:38:00 -08002480
David Howells43f5e652018-11-01 23:07:25 +00002481 if ((fl & MNT_LOCK_READONLY) &&
2482 !(mnt_flags & MNT_READONLY))
2483 return false;
2484
2485 if ((fl & MNT_LOCK_NODEV) &&
2486 !(mnt_flags & MNT_NODEV))
2487 return false;
2488
2489 if ((fl & MNT_LOCK_NOSUID) &&
2490 !(mnt_flags & MNT_NOSUID))
2491 return false;
2492
2493 if ((fl & MNT_LOCK_NOEXEC) &&
2494 !(mnt_flags & MNT_NOEXEC))
2495 return false;
2496
2497 if ((fl & MNT_LOCK_ATIME) &&
2498 ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK)))
2499 return false;
2500
2501 return true;
2502}
2503
2504static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags)
2505{
2506 bool readonly_request = (mnt_flags & MNT_READONLY);
2507
2508 if (readonly_request == __mnt_is_readonly(&mnt->mnt))
Dave Hansen2e4b7fc2008-02-15 14:38:00 -08002509 return 0;
2510
2511 if (readonly_request)
David Howells43f5e652018-11-01 23:07:25 +00002512 return mnt_make_readonly(mnt);
2513
2514 return __mnt_unmake_readonly(mnt);
2515}
2516
2517/*
2518 * Update the user-settable attributes on a mount. The caller must hold
2519 * sb->s_umount for writing.
2520 */
2521static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags)
2522{
2523 lock_mount_hash();
2524 mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
2525 mnt->mnt.mnt_flags = mnt_flags;
2526 touch_mnt_namespace(mnt->mnt_ns);
2527 unlock_mount_hash();
2528}
2529
Deepa Dinamanif8b92ba2019-04-15 14:17:12 -07002530static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt)
2531{
2532 struct super_block *sb = mnt->mnt_sb;
2533
2534 if (!__mnt_is_readonly(mnt) &&
2535 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
2536 char *buf = (char *)__get_free_page(GFP_KERNEL);
2537 char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM);
2538 struct tm tm;
2539
2540 time64_to_tm(sb->s_time_max, 0, &tm);
2541
Eric Biggers0ecee662019-10-16 19:48:14 -07002542 pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n",
2543 sb->s_type->name,
2544 is_mounted(mnt) ? "remounted" : "mounted",
2545 mntpath,
Deepa Dinamanif8b92ba2019-04-15 14:17:12 -07002546 tm.tm_year+1900, (unsigned long long)sb->s_time_max);
2547
2548 free_page((unsigned long)buf);
2549 }
2550}
2551
David Howells43f5e652018-11-01 23:07:25 +00002552/*
2553 * Handle reconfiguration of the mountpoint only without alteration of the
2554 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2555 * to mount(2).
2556 */
2557static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags)
2558{
2559 struct super_block *sb = path->mnt->mnt_sb;
2560 struct mount *mnt = real_mount(path->mnt);
2561 int ret;
2562
2563 if (!check_mnt(mnt))
2564 return -EINVAL;
2565
2566 if (path->dentry != mnt->mnt.mnt_root)
2567 return -EINVAL;
2568
2569 if (!can_change_locked_flags(mnt, mnt_flags))
2570 return -EPERM;
2571
2572 down_write(&sb->s_umount);
2573 ret = change_mount_ro_state(mnt, mnt_flags);
2574 if (ret == 0)
2575 set_mount_attributes(mnt, mnt_flags);
2576 up_write(&sb->s_umount);
Deepa Dinamanif8b92ba2019-04-15 14:17:12 -07002577
2578 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2579
David Howells43f5e652018-11-01 23:07:25 +00002580 return ret;
Dave Hansen2e4b7fc2008-02-15 14:38:00 -08002581}
2582
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583/*
2584 * change filesystem flags. dir should be a physical root of filesystem.
2585 * If you've mounted a non-root directory somewhere and want to do remount
2586 * on it - tough luck.
2587 */
David Howellse462ec52017-07-17 08:45:35 +01002588static int do_remount(struct path *path, int ms_flags, int sb_flags,
2589 int mnt_flags, void *data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002590{
2591 int err;
Al Viro2d92ab32008-08-02 00:51:11 -04002592 struct super_block *sb = path->mnt->mnt_sb;
Al Viro143c8c92011-11-25 00:46:35 -05002593 struct mount *mnt = real_mount(path->mnt);
David Howells8d0347f2018-11-04 09:28:36 -05002594 struct fs_context *fc;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002595
Al Viro143c8c92011-11-25 00:46:35 -05002596 if (!check_mnt(mnt))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002597 return -EINVAL;
2598
Al Viro2d92ab32008-08-02 00:51:11 -04002599 if (path->dentry != path->mnt->mnt_root)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002600 return -EINVAL;
2601
David Howells43f5e652018-11-01 23:07:25 +00002602 if (!can_change_locked_flags(mnt, mnt_flags))
Eric W. Biederman07b64552014-07-28 17:10:56 -07002603 return -EPERM;
Eric W. Biederman9566d672014-07-28 17:26:07 -07002604
David Howells8d0347f2018-11-04 09:28:36 -05002605 fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK);
2606 if (IS_ERR(fc))
2607 return PTR_ERR(fc);
Eric Parisff36fe22011-03-03 16:09:14 -05002608
Miklos Szeredib3309662020-07-14 14:45:41 +02002609 fc->oldapi = true;
David Howells8d0347f2018-11-04 09:28:36 -05002610 err = parse_monolithic_mount_data(fc, data);
2611 if (!err) {
2612 down_write(&sb->s_umount);
2613 err = -EPERM;
2614 if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
2615 err = reconfigure_super(fc);
2616 if (!err)
2617 set_mount_attributes(mnt, mnt_flags);
2618 }
2619 up_write(&sb->s_umount);
Dan Williams0e55a7c2008-09-26 19:01:20 -07002620 }
Deepa Dinamanif8b92ba2019-04-15 14:17:12 -07002621
2622 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2623
David Howells8d0347f2018-11-04 09:28:36 -05002624 put_fs_context(fc);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002625 return err;
2626}
2627
Al Virocbbe3622011-11-24 20:01:19 -05002628static inline int tree_contains_unbindable(struct mount *mnt)
Ram Pai9676f0c2005-11-07 17:21:20 -05002629{
Al Viro315fc832011-11-24 18:57:30 -05002630 struct mount *p;
Al Viro909b0a82011-11-25 03:06:56 -05002631 for (p = mnt; p; p = next_mnt(p, mnt)) {
Al Virofc7be132011-11-25 01:05:37 -05002632 if (IS_MNT_UNBINDABLE(p))
Ram Pai9676f0c2005-11-07 17:21:20 -05002633 return 1;
2634 }
2635 return 0;
2636}
2637
David Howells44dfd842018-11-05 17:40:31 +00002638/*
2639 * Check that there aren't references to earlier/same mount namespaces in the
2640 * specified subtree. Such references can act as pins for mount namespaces
2641 * that aren't checked by the mount-cycle checking code, thereby allowing
2642 * cycles to be made.
2643 */
2644static bool check_for_nsfs_mounts(struct mount *subtree)
2645{
2646 struct mount *p;
2647 bool ret = false;
2648
2649 lock_mount_hash();
2650 for (p = subtree; p; p = next_mnt(p, subtree))
2651 if (mnt_ns_loop(p->mnt.mnt_root))
2652 goto out;
2653
2654 ret = true;
2655out:
2656 unlock_mount_hash();
2657 return ret;
2658}
2659
David Howells2db154b2018-11-05 17:40:30 +00002660static int do_move_mount(struct path *old_path, struct path *new_path)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002661{
David Howells44dfd842018-11-05 17:40:31 +00002662 struct mnt_namespace *ns;
Al Viro676da582011-11-24 21:47:05 -05002663 struct mount *p;
Al Viro0fb54e52011-11-24 19:59:16 -05002664 struct mount *old;
Al Viro2763d112019-06-30 19:18:53 -04002665 struct mount *parent;
2666 struct mountpoint *mp, *old_mp;
Al Viro57eccb82013-02-22 22:49:10 -05002667 int err;
David Howells44dfd842018-11-05 17:40:31 +00002668 bool attached;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002669
David Howells2db154b2018-11-05 17:40:30 +00002670 mp = lock_mount(new_path);
Al Viro84d17192013-03-15 10:53:28 -04002671 if (IS_ERR(mp))
David Howells2db154b2018-11-05 17:40:30 +00002672 return PTR_ERR(mp);
David Howellscc53ce52011-01-14 18:45:26 +00002673
David Howells2db154b2018-11-05 17:40:30 +00002674 old = real_mount(old_path->mnt);
2675 p = real_mount(new_path->mnt);
Al Viro2763d112019-06-30 19:18:53 -04002676 parent = old->mnt_parent;
David Howells44dfd842018-11-05 17:40:31 +00002677 attached = mnt_has_parent(old);
Al Viro2763d112019-06-30 19:18:53 -04002678 old_mp = old->mnt_mp;
David Howells44dfd842018-11-05 17:40:31 +00002679 ns = old->mnt_ns;
Al Viro143c8c92011-11-25 00:46:35 -05002680
Linus Torvalds1da177e2005-04-16 15:20:36 -07002681 err = -EINVAL;
David Howells44dfd842018-11-05 17:40:31 +00002682 /* The mountpoint must be in our namespace. */
2683 if (!check_mnt(p))
David Howells2db154b2018-11-05 17:40:30 +00002684 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002685
Eric Biggers570d7a92019-06-29 13:27:44 -07002686 /* The thing moved must be mounted... */
2687 if (!is_mounted(&old->mnt))
David Howells44dfd842018-11-05 17:40:31 +00002688 goto out;
2689
Eric Biggers570d7a92019-06-29 13:27:44 -07002690 /* ... and either ours or the root of anon namespace */
2691 if (!(attached ? check_mnt(old) : is_anon_ns(ns)))
David Howells2db154b2018-11-05 17:40:30 +00002692 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002693
David Howells2db154b2018-11-05 17:40:30 +00002694 if (old->mnt.mnt_flags & MNT_LOCKED)
2695 goto out;
2696
2697 if (old_path->dentry != old_path->mnt->mnt_root)
2698 goto out;
2699
2700 if (d_is_dir(new_path->dentry) !=
2701 d_is_dir(old_path->dentry))
2702 goto out;
Ram Pai21444402005-11-07 17:20:03 -05002703 /*
2704 * Don't move a mount residing in a shared parent.
2705 */
Al Viro2763d112019-06-30 19:18:53 -04002706 if (attached && IS_MNT_SHARED(parent))
David Howells2db154b2018-11-05 17:40:30 +00002707 goto out;
Ram Pai9676f0c2005-11-07 17:21:20 -05002708 /*
2709 * Don't move a mount tree containing unbindable mounts to a destination
2710 * mount which is shared.
2711 */
Al Virofc7be132011-11-25 01:05:37 -05002712 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
David Howells2db154b2018-11-05 17:40:30 +00002713 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002714 err = -ELOOP;
David Howells44dfd842018-11-05 17:40:31 +00002715 if (!check_for_nsfs_mounts(old))
2716 goto out;
Al Virofc7be132011-11-25 01:05:37 -05002717 for (; mnt_has_parent(p); p = p->mnt_parent)
Al Viro676da582011-11-24 21:47:05 -05002718 if (p == old)
David Howells2db154b2018-11-05 17:40:30 +00002719 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720
David Howells2db154b2018-11-05 17:40:30 +00002721 err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp,
Al Viro2763d112019-06-30 19:18:53 -04002722 attached);
Jan Blunck4ac91372008-02-14 19:34:32 -08002723 if (err)
David Howells2db154b2018-11-05 17:40:30 +00002724 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002725
2726 /* if the mount is moved, it should no longer be expire
2727 * automatically */
Al Viro6776db3d2011-11-25 00:22:05 -05002728 list_del_init(&old->mnt_expire);
Al Viro2763d112019-06-30 19:18:53 -04002729 if (attached)
2730 put_mountpoint(old_mp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002731out:
David Howells2db154b2018-11-05 17:40:30 +00002732 unlock_mount(mp);
David Howells44dfd842018-11-05 17:40:31 +00002733 if (!err) {
Al Viro2763d112019-06-30 19:18:53 -04002734 if (attached)
2735 mntput_no_expire(parent);
2736 else
David Howells44dfd842018-11-05 17:40:31 +00002737 free_mnt_ns(ns);
2738 }
David Howells2db154b2018-11-05 17:40:30 +00002739 return err;
2740}
2741
2742static int do_move_mount_old(struct path *path, const char *old_name)
2743{
2744 struct path old_path;
2745 int err;
2746
2747 if (!old_name || !*old_name)
2748 return -EINVAL;
2749
2750 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
2751 if (err)
2752 return err;
2753
2754 err = do_move_mount(&old_path, path);
Al Viro2d92ab32008-08-02 00:51:11 -04002755 path_put(&old_path);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002756 return err;
2757}
2758
Al Viro9d412a42011-03-17 22:08:28 -04002759/*
2760 * add a mount into a namespace's mount tree
2761 */
Al Viro8f115382020-01-11 10:14:09 -05002762static int do_add_mount(struct mount *newmnt, struct mountpoint *mp,
2763 struct path *path, int mnt_flags)
Al Viro9d412a42011-03-17 22:08:28 -04002764{
Al Viro8f115382020-01-11 10:14:09 -05002765 struct mount *parent = real_mount(path->mnt);
Al Viro9d412a42011-03-17 22:08:28 -04002766
Al Virof2ebb3a2014-02-27 09:35:45 -05002767 mnt_flags &= ~MNT_INTERNAL_FLAGS;
Al Viro9d412a42011-03-17 22:08:28 -04002768
Al Viro84d17192013-03-15 10:53:28 -04002769 if (unlikely(!check_mnt(parent))) {
Al Viro156cacb2012-09-21 08:19:02 -04002770 /* that's acceptable only for automounts done in private ns */
2771 if (!(mnt_flags & MNT_SHRINKABLE))
Al Viro8f115382020-01-11 10:14:09 -05002772 return -EINVAL;
Al Viro156cacb2012-09-21 08:19:02 -04002773 /* ... and for those we'd better have mountpoint still alive */
Al Viro84d17192013-03-15 10:53:28 -04002774 if (!parent->mnt_ns)
Al Viro8f115382020-01-11 10:14:09 -05002775 return -EINVAL;
Al Viro156cacb2012-09-21 08:19:02 -04002776 }
Al Viro9d412a42011-03-17 22:08:28 -04002777
2778 /* Refuse the same filesystem on the same mount point */
Al Viro95bc5f22011-11-25 00:30:56 -05002779 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
Al Viro9d412a42011-03-17 22:08:28 -04002780 path->mnt->mnt_root == path->dentry)
Al Viro8f115382020-01-11 10:14:09 -05002781 return -EBUSY;
Al Viro9d412a42011-03-17 22:08:28 -04002782
David Howellse36cb0b2015-01-29 12:02:35 +00002783 if (d_is_symlink(newmnt->mnt.mnt_root))
Al Viro8f115382020-01-11 10:14:09 -05002784 return -EINVAL;
Al Viro9d412a42011-03-17 22:08:28 -04002785
Al Viro95bc5f22011-11-25 00:30:56 -05002786 newmnt->mnt.mnt_flags = mnt_flags;
Al Viro8f115382020-01-11 10:14:09 -05002787 return graft_tree(newmnt, parent, mp);
Al Viro9d412a42011-03-17 22:08:28 -04002788}
Al Virob1e75df2011-01-17 01:47:59 -05002789
David Howells132e4602018-11-04 07:43:08 -05002790static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
2791
2792/*
2793 * Create a new mount using a superblock configuration and request it
2794 * be added to the namespace tree.
2795 */
2796static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
2797 unsigned int mnt_flags)
2798{
2799 struct vfsmount *mnt;
Al Viro8f115382020-01-11 10:14:09 -05002800 struct mountpoint *mp;
David Howells132e4602018-11-04 07:43:08 -05002801 struct super_block *sb = fc->root->d_sb;
2802 int error;
2803
Al Viroc9ce29e2018-12-20 15:04:50 -05002804 error = security_sb_kern_mount(sb);
2805 if (!error && mount_too_revealing(sb, &mnt_flags))
2806 error = -EPERM;
2807
2808 if (unlikely(error)) {
2809 fc_drop_locked(fc);
2810 return error;
David Howells132e4602018-11-04 07:43:08 -05002811 }
2812
2813 up_write(&sb->s_umount);
2814
2815 mnt = vfs_create_mount(fc);
2816 if (IS_ERR(mnt))
2817 return PTR_ERR(mnt);
2818
Deepa Dinamanif8b92ba2019-04-15 14:17:12 -07002819 mnt_warn_timestamp_expiry(mountpoint, mnt);
2820
Al Viro8f115382020-01-11 10:14:09 -05002821 mp = lock_mount(mountpoint);
2822 if (IS_ERR(mp)) {
2823 mntput(mnt);
2824 return PTR_ERR(mp);
2825 }
2826 error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags);
2827 unlock_mount(mp);
Eric Biggers0ecee662019-10-16 19:48:14 -07002828 if (error < 0)
2829 mntput(mnt);
David Howells132e4602018-11-04 07:43:08 -05002830 return error;
2831}
Eric W. Biederman1b852bc2015-05-08 23:22:29 -05002832
Linus Torvalds1da177e2005-04-16 15:20:36 -07002833/*
2834 * create a new mount for userspace and request it to be added into the
2835 * namespace's tree
2836 */
David Howellse462ec52017-07-17 08:45:35 +01002837static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
Al Viro808d4e32012-10-11 11:42:01 -04002838 int mnt_flags, const char *name, void *data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002839{
Eric W. Biederman0c55cfc2012-07-26 21:42:03 -07002840 struct file_system_type *type;
Al Viroa0c9a8b2018-11-04 07:18:51 -05002841 struct fs_context *fc;
2842 const char *subtype = NULL;
2843 int err = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002844
Eric W. Biederman0c55cfc2012-07-26 21:42:03 -07002845 if (!fstype)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002846 return -EINVAL;
2847
Eric W. Biederman0c55cfc2012-07-26 21:42:03 -07002848 type = get_fs_type(fstype);
2849 if (!type)
2850 return -ENODEV;
2851
Al Viroa0c9a8b2018-11-04 07:18:51 -05002852 if (type->fs_flags & FS_HAS_SUBTYPE) {
2853 subtype = strchr(fstype, '.');
2854 if (subtype) {
2855 subtype++;
2856 if (!*subtype) {
2857 put_filesystem(type);
2858 return -EINVAL;
2859 }
Al Viroa0c9a8b2018-11-04 07:18:51 -05002860 }
Eric W. Biederman8654df42016-06-09 16:06:06 -05002861 }
2862
Al Viroa0c9a8b2018-11-04 07:18:51 -05002863 fc = fs_context_for_mount(type, sb_flags);
Eric W. Biederman0c55cfc2012-07-26 21:42:03 -07002864 put_filesystem(type);
Al Viroa0c9a8b2018-11-04 07:18:51 -05002865 if (IS_ERR(fc))
2866 return PTR_ERR(fc);
2867
David Howells3e1aeb02018-11-01 23:07:25 +00002868 if (subtype)
2869 err = vfs_parse_fs_string(fc, "subtype",
2870 subtype, strlen(subtype));
2871 if (!err && name)
2872 err = vfs_parse_fs_string(fc, "source", name, strlen(name));
Al Viroa0c9a8b2018-11-04 07:18:51 -05002873 if (!err)
2874 err = parse_monolithic_mount_data(fc, data);
Al Viroc3aabf02019-05-13 12:57:22 -04002875 if (!err && !mount_capable(fc))
2876 err = -EPERM;
Al Viroa0c9a8b2018-11-04 07:18:51 -05002877 if (!err)
2878 err = vfs_get_tree(fc);
David Howells132e4602018-11-04 07:43:08 -05002879 if (!err)
2880 err = do_new_mount_fc(fc, path, mnt_flags);
Al Viroa0c9a8b2018-11-04 07:18:51 -05002881
Al Viroa0c9a8b2018-11-04 07:18:51 -05002882 put_fs_context(fc);
Al Viro15f9a3f2011-01-17 01:41:58 -05002883 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002884}
2885
Al Viro19a167a2011-01-17 01:35:23 -05002886int finish_automount(struct vfsmount *m, struct path *path)
2887{
Al Viro26df6032020-01-11 10:44:29 -05002888 struct dentry *dentry = path->dentry;
Al Viro8f115382020-01-11 10:14:09 -05002889 struct mountpoint *mp;
Al Viro25e195a2020-01-11 11:27:46 -05002890 struct mount *mnt;
Al Viro19a167a2011-01-17 01:35:23 -05002891 int err;
Al Viro25e195a2020-01-11 11:27:46 -05002892
2893 if (!m)
2894 return 0;
2895 if (IS_ERR(m))
2896 return PTR_ERR(m);
2897
2898 mnt = real_mount(m);
Al Viro19a167a2011-01-17 01:35:23 -05002899 /* The new mount record should have at least 2 refs to prevent it being
2900 * expired before we get a chance to add it
2901 */
Al Viro6776db3d2011-11-25 00:22:05 -05002902 BUG_ON(mnt_get_count(mnt) < 2);
Al Viro19a167a2011-01-17 01:35:23 -05002903
2904 if (m->mnt_sb == path->mnt->mnt_sb &&
Al Viro26df6032020-01-11 10:44:29 -05002905 m->mnt_root == dentry) {
Al Virob1e75df2011-01-17 01:47:59 -05002906 err = -ELOOP;
Al Viro26df6032020-01-11 10:44:29 -05002907 goto discard;
Al Viro19a167a2011-01-17 01:35:23 -05002908 }
2909
Al Viro26df6032020-01-11 10:44:29 -05002910 /*
2911 * we don't want to use lock_mount() - in this case finding something
2912 * that overmounts our mountpoint to be means "quitely drop what we've
2913 * got", not "try to mount it on top".
2914 */
2915 inode_lock(dentry->d_inode);
2916 namespace_lock();
2917 if (unlikely(cant_mount(dentry))) {
2918 err = -ENOENT;
2919 goto discard_locked;
2920 }
2921 rcu_read_lock();
2922 if (unlikely(__lookup_mnt(path->mnt, dentry))) {
2923 rcu_read_unlock();
2924 err = 0;
2925 goto discard_locked;
2926 }
2927 rcu_read_unlock();
2928 mp = get_mountpoint(dentry);
Al Viro8f115382020-01-11 10:14:09 -05002929 if (IS_ERR(mp)) {
2930 err = PTR_ERR(mp);
Al Viro26df6032020-01-11 10:44:29 -05002931 goto discard_locked;
Al Viro8f115382020-01-11 10:14:09 -05002932 }
Al Viro26df6032020-01-11 10:44:29 -05002933
Al Viro8f115382020-01-11 10:14:09 -05002934 err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2935 unlock_mount(mp);
Al Viro26df6032020-01-11 10:44:29 -05002936 if (unlikely(err))
2937 goto discard;
2938 mntput(m);
2939 return 0;
2940
2941discard_locked:
2942 namespace_unlock();
2943 inode_unlock(dentry->d_inode);
2944discard:
Al Virob1e75df2011-01-17 01:47:59 -05002945 /* remove m from any expiration list it may be on */
Al Viro6776db3d2011-11-25 00:22:05 -05002946 if (!list_empty(&mnt->mnt_expire)) {
Al Viro97216be2013-03-16 15:12:40 -04002947 namespace_lock();
Al Viro6776db3d2011-11-25 00:22:05 -05002948 list_del_init(&mnt->mnt_expire);
Al Viro97216be2013-03-16 15:12:40 -04002949 namespace_unlock();
Al Viro19a167a2011-01-17 01:35:23 -05002950 }
Al Virob1e75df2011-01-17 01:47:59 -05002951 mntput(m);
2952 mntput(m);
Al Viro19a167a2011-01-17 01:35:23 -05002953 return err;
2954}
2955
David Howellsea5b7782011-01-14 19:10:03 +00002956/**
2957 * mnt_set_expiry - Put a mount on an expiration list
2958 * @mnt: The mount to list.
2959 * @expiry_list: The list to add the mount to.
2960 */
2961void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2962{
Al Viro97216be2013-03-16 15:12:40 -04002963 namespace_lock();
David Howellsea5b7782011-01-14 19:10:03 +00002964
Al Viro6776db3d2011-11-25 00:22:05 -05002965 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
David Howellsea5b7782011-01-14 19:10:03 +00002966
Al Viro97216be2013-03-16 15:12:40 -04002967 namespace_unlock();
David Howellsea5b7782011-01-14 19:10:03 +00002968}
2969EXPORT_SYMBOL(mnt_set_expiry);
2970
2971/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002972 * process a list of expirable mountpoints with the intent of discarding any
2973 * mountpoints that aren't in use and haven't been touched since last we came
2974 * here
2975 */
2976void mark_mounts_for_expiry(struct list_head *mounts)
2977{
Al Viro761d5c32011-11-24 21:07:43 -05002978 struct mount *mnt, *next;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002979 LIST_HEAD(graveyard);
2980
2981 if (list_empty(mounts))
2982 return;
2983
Al Viro97216be2013-03-16 15:12:40 -04002984 namespace_lock();
Al Viro719ea2f2013-09-29 11:24:49 -04002985 lock_mount_hash();
Linus Torvalds1da177e2005-04-16 15:20:36 -07002986
2987 /* extract from the expiration list every vfsmount that matches the
2988 * following criteria:
2989 * - only referenced by its parent vfsmount
2990 * - still marked for expiry (marked on the last call here; marks are
2991 * cleared by mntput())
2992 */
Al Viro6776db3d2011-11-25 00:22:05 -05002993 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
Al Viro863d6842011-11-25 00:57:42 -05002994 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
Al Viro1ab59732011-11-24 21:35:16 -05002995 propagate_mount_busy(mnt, 1))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002996 continue;
Al Viro6776db3d2011-11-25 00:22:05 -05002997 list_move(&mnt->mnt_expire, &graveyard);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002998 }
Al Virobcc5c7d2008-03-22 00:21:53 -04002999 while (!list_empty(&graveyard)) {
Al Viro6776db3d2011-11-25 00:22:05 -05003000 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
Al Viro143c8c92011-11-25 00:46:35 -05003001 touch_mnt_namespace(mnt->mnt_ns);
Eric W. Biedermane819f152014-12-24 07:20:01 -06003002 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
Al Virobcc5c7d2008-03-22 00:21:53 -04003003 }
Al Viro719ea2f2013-09-29 11:24:49 -04003004 unlock_mount_hash();
Al Viro3ab6abe2013-03-16 14:42:19 -04003005 namespace_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003006}
3007
3008EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
3009
3010/*
Trond Myklebust5528f9112006-06-09 09:34:17 -04003011 * Ripoff of 'select_parent()'
3012 *
3013 * search the list of submounts for a given mountpoint, and move any
3014 * shrinkable submounts to the 'graveyard' list.
3015 */
Al Viro692afc32011-11-24 21:15:14 -05003016static int select_submounts(struct mount *parent, struct list_head *graveyard)
Trond Myklebust5528f9112006-06-09 09:34:17 -04003017{
Al Viro692afc32011-11-24 21:15:14 -05003018 struct mount *this_parent = parent;
Trond Myklebust5528f9112006-06-09 09:34:17 -04003019 struct list_head *next;
3020 int found = 0;
3021
3022repeat:
Al Viro6b41d532011-11-24 23:24:33 -05003023 next = this_parent->mnt_mounts.next;
Trond Myklebust5528f9112006-06-09 09:34:17 -04003024resume:
Al Viro6b41d532011-11-24 23:24:33 -05003025 while (next != &this_parent->mnt_mounts) {
Trond Myklebust5528f9112006-06-09 09:34:17 -04003026 struct list_head *tmp = next;
Al Viro6b41d532011-11-24 23:24:33 -05003027 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
Trond Myklebust5528f9112006-06-09 09:34:17 -04003028
3029 next = tmp->next;
Al Viro692afc32011-11-24 21:15:14 -05003030 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
Trond Myklebust5528f9112006-06-09 09:34:17 -04003031 continue;
3032 /*
3033 * Descend a level if the d_mounts list is non-empty.
3034 */
Al Viro6b41d532011-11-24 23:24:33 -05003035 if (!list_empty(&mnt->mnt_mounts)) {
Trond Myklebust5528f9112006-06-09 09:34:17 -04003036 this_parent = mnt;
3037 goto repeat;
3038 }
3039
Al Viro1ab59732011-11-24 21:35:16 -05003040 if (!propagate_mount_busy(mnt, 1)) {
Al Viro6776db3d2011-11-25 00:22:05 -05003041 list_move_tail(&mnt->mnt_expire, graveyard);
Trond Myklebust5528f9112006-06-09 09:34:17 -04003042 found++;
3043 }
3044 }
3045 /*
3046 * All done at this level ... ascend and resume the search
3047 */
3048 if (this_parent != parent) {
Al Viro6b41d532011-11-24 23:24:33 -05003049 next = this_parent->mnt_child.next;
Al Viro0714a532011-11-24 22:19:58 -05003050 this_parent = this_parent->mnt_parent;
Trond Myklebust5528f9112006-06-09 09:34:17 -04003051 goto resume;
3052 }
3053 return found;
3054}
3055
3056/*
3057 * process a list of expirable mountpoints with the intent of discarding any
3058 * submounts of a specific parent mountpoint
Nick Piggin99b7db72010-08-18 04:37:39 +10003059 *
Al Viro48a066e2013-09-29 22:06:07 -04003060 * mount_lock must be held for write
Trond Myklebust5528f9112006-06-09 09:34:17 -04003061 */
Al Virob54b9be2013-03-16 14:39:34 -04003062static void shrink_submounts(struct mount *mnt)
Trond Myklebust5528f9112006-06-09 09:34:17 -04003063{
3064 LIST_HEAD(graveyard);
Al Viro761d5c32011-11-24 21:07:43 -05003065 struct mount *m;
Trond Myklebust5528f9112006-06-09 09:34:17 -04003066
Trond Myklebust5528f9112006-06-09 09:34:17 -04003067 /* extract submounts of 'mountpoint' from the expiration list */
Al Viroc35038b2008-03-22 00:46:23 -04003068 while (select_submounts(mnt, &graveyard)) {
Al Virobcc5c7d2008-03-22 00:21:53 -04003069 while (!list_empty(&graveyard)) {
Al Viro761d5c32011-11-24 21:07:43 -05003070 m = list_first_entry(&graveyard, struct mount,
Al Viro6776db3d2011-11-25 00:22:05 -05003071 mnt_expire);
Al Viro143c8c92011-11-25 00:46:35 -05003072 touch_mnt_namespace(m->mnt_ns);
Eric W. Biedermane819f152014-12-24 07:20:01 -06003073 umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);
Al Virobcc5c7d2008-03-22 00:21:53 -04003074 }
3075 }
Trond Myklebust5528f9112006-06-09 09:34:17 -04003076}
3077
Christoph Hellwig028abd92020-09-17 10:22:34 +02003078static void *copy_mount_options(const void __user * data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003079{
Al Virob40ef862015-12-14 18:44:44 -05003080 char *copy;
Catalin Marinasd563d672020-07-01 17:46:06 +01003081 unsigned left, offset;
Ram Paib58fed82005-11-07 17:16:09 -05003082
Linus Torvalds1da177e2005-04-16 15:20:36 -07003083 if (!data)
Al Virob40ef862015-12-14 18:44:44 -05003084 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003085
Al Virob40ef862015-12-14 18:44:44 -05003086 copy = kmalloc(PAGE_SIZE, GFP_KERNEL);
3087 if (!copy)
3088 return ERR_PTR(-ENOMEM);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003089
Catalin Marinasd563d672020-07-01 17:46:06 +01003090 left = copy_from_user(copy, data, PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003091
Catalin Marinasd563d672020-07-01 17:46:06 +01003092 /*
3093 * Not all architectures have an exact copy_from_user(). Resort to
3094 * byte at a time.
3095 */
3096 offset = PAGE_SIZE - left;
3097 while (left) {
3098 char c;
3099 if (get_user(c, (const char __user *)data + offset))
3100 break;
3101 copy[offset] = c;
3102 left--;
3103 offset++;
3104 }
3105
3106 if (left == PAGE_SIZE) {
Al Virob40ef862015-12-14 18:44:44 -05003107 kfree(copy);
3108 return ERR_PTR(-EFAULT);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003109 }
Catalin Marinasd563d672020-07-01 17:46:06 +01003110
Al Virob40ef862015-12-14 18:44:44 -05003111 return copy;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003112}
3113
Christoph Hellwig028abd92020-09-17 10:22:34 +02003114static char *copy_mount_string(const void __user *data)
Vegard Nossumeca6f532009-09-18 13:05:45 -07003115{
Chandan Rajendrafbdb4402019-01-22 12:21:52 +05303116 return data ? strndup_user(data, PATH_MAX) : NULL;
Vegard Nossumeca6f532009-09-18 13:05:45 -07003117}
3118
Linus Torvalds1da177e2005-04-16 15:20:36 -07003119/*
3120 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3121 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3122 *
3123 * data is a (void *) that can point to any structure up to
3124 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3125 * information (or be NULL).
3126 *
3127 * Pre-0.97 versions of mount() didn't have a flags word.
3128 * When the flags word was introduced its top half was required
3129 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3130 * Therefore, if this magic number is present, it carries no information
3131 * and must be discarded.
3132 */
Christoph Hellwigc60166f2020-07-21 11:12:08 +02003133int path_mount(const char *dev_name, struct path *path,
Al Viro808d4e32012-10-11 11:42:01 -04003134 const char *type_page, unsigned long flags, void *data_page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003135{
David Howellse462ec52017-07-17 08:45:35 +01003136 unsigned int mnt_flags = 0, sb_flags;
Christoph Hellwiga1e6aaa2020-06-04 09:41:08 +02003137 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003138
3139 /* Discard magic */
3140 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
3141 flags &= ~MS_MGC_MSK;
3142
3143 /* Basic sanity checks */
Linus Torvalds1da177e2005-04-16 15:20:36 -07003144 if (data_page)
3145 ((char *)data_page)[PAGE_SIZE - 1] = 0;
3146
David Howellse462ec52017-07-17 08:45:35 +01003147 if (flags & MS_NOUSER)
3148 return -EINVAL;
3149
Christoph Hellwiga1e6aaa2020-06-04 09:41:08 +02003150 ret = security_sb_mount(dev_name, path, type_page, flags, data_page);
3151 if (ret)
3152 return ret;
3153 if (!may_mount())
3154 return -EPERM;
3155 if ((flags & SB_MANDLOCK) && !may_mandlock())
3156 return -EPERM;
Tetsuo Handaa27ab9f22009-10-04 21:49:49 +09003157
Andi Kleen613cbe32009-04-19 18:40:43 +02003158 /* Default to relatime unless overriden */
3159 if (!(flags & MS_NOATIME))
3160 mnt_flags |= MNT_RELATIME;
Matthew Garrett0a1c01c2009-03-26 17:53:14 +00003161
Linus Torvalds1da177e2005-04-16 15:20:36 -07003162 /* Separate the per-mountpoint flags */
3163 if (flags & MS_NOSUID)
3164 mnt_flags |= MNT_NOSUID;
3165 if (flags & MS_NODEV)
3166 mnt_flags |= MNT_NODEV;
3167 if (flags & MS_NOEXEC)
3168 mnt_flags |= MNT_NOEXEC;
Christoph Hellwigfc33a7b2006-01-09 20:52:17 -08003169 if (flags & MS_NOATIME)
3170 mnt_flags |= MNT_NOATIME;
3171 if (flags & MS_NODIRATIME)
3172 mnt_flags |= MNT_NODIRATIME;
Matthew Garrettd0adde52009-03-26 17:49:56 +00003173 if (flags & MS_STRICTATIME)
3174 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
David Howellsa9e5b732018-04-20 13:35:02 +01003175 if (flags & MS_RDONLY)
Dave Hansen2e4b7fc2008-02-15 14:38:00 -08003176 mnt_flags |= MNT_READONLY;
Mattias Nisslerdab741e02020-08-27 11:09:46 -06003177 if (flags & MS_NOSYMFOLLOW)
3178 mnt_flags |= MNT_NOSYMFOLLOW;
Christoph Hellwigfc33a7b2006-01-09 20:52:17 -08003179
Eric W. Biedermanffbc6f02014-07-28 17:36:04 -07003180 /* The default atime for remount is preservation */
3181 if ((flags & MS_REMOUNT) &&
3182 ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
3183 MS_STRICTATIME)) == 0)) {
3184 mnt_flags &= ~MNT_ATIME_MASK;
Christoph Hellwiga1e6aaa2020-06-04 09:41:08 +02003185 mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK;
Eric W. Biedermanffbc6f02014-07-28 17:36:04 -07003186 }
3187
David Howellse462ec52017-07-17 08:45:35 +01003188 sb_flags = flags & (SB_RDONLY |
3189 SB_SYNCHRONOUS |
3190 SB_MANDLOCK |
3191 SB_DIRSYNC |
3192 SB_SILENT |
Mimi Zohar917086f2017-10-08 00:28:21 -04003193 SB_POSIXACL |
Markus Trippelsdorfd7ee9462017-10-11 07:01:31 +02003194 SB_LAZYTIME |
Mimi Zohar917086f2017-10-08 00:28:21 -04003195 SB_I_VERSION);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003196
David Howells43f5e652018-11-01 23:07:25 +00003197 if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND))
Christoph Hellwiga1e6aaa2020-06-04 09:41:08 +02003198 return do_reconfigure_mnt(path, mnt_flags);
3199 if (flags & MS_REMOUNT)
3200 return do_remount(path, flags, sb_flags, mnt_flags, data_page);
3201 if (flags & MS_BIND)
3202 return do_loopback(path, dev_name, flags & MS_REC);
3203 if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
3204 return do_change_type(path, flags);
3205 if (flags & MS_MOVE)
3206 return do_move_mount_old(path, dev_name);
3207
3208 return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name,
3209 data_page);
3210}
3211
3212long do_mount(const char *dev_name, const char __user *dir_name,
3213 const char *type_page, unsigned long flags, void *data_page)
3214{
3215 struct path path;
3216 int ret;
3217
3218 ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path);
3219 if (ret)
3220 return ret;
3221 ret = path_mount(dev_name, &path, type_page, flags, data_page);
Al Viro2d92ab32008-08-02 00:51:11 -04003222 path_put(&path);
Christoph Hellwiga1e6aaa2020-06-04 09:41:08 +02003223 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003224}
3225
Eric W. Biederman537f7cc2016-08-08 14:37:37 -05003226static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
3227{
3228 return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES);
3229}
3230
3231static void dec_mnt_namespaces(struct ucounts *ucounts)
3232{
3233 dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES);
3234}
3235
Eric W. Biederman771b1372012-07-26 21:08:32 -07003236static void free_mnt_ns(struct mnt_namespace *ns)
3237{
Al Viro74e83122019-01-30 13:30:21 -05003238 if (!is_anon_ns(ns))
3239 ns_free_inum(&ns->ns);
Eric W. Biederman537f7cc2016-08-08 14:37:37 -05003240 dec_mnt_namespaces(ns->ucounts);
Eric W. Biederman771b1372012-07-26 21:08:32 -07003241 put_user_ns(ns->user_ns);
3242 kfree(ns);
3243}
3244
Eric W. Biederman8823c072010-03-07 18:49:36 -08003245/*
3246 * Assign a sequence number so we can detect when we attempt to bind
3247 * mount a reference to an older mount namespace into the current
3248 * mount namespace, preventing reference counting loops. A 64bit
3249 * number incrementing at 10Ghz will take 12,427 years to wrap which
3250 * is effectively never, so we can ignore the possibility.
3251 */
3252static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
3253
Al Viro74e83122019-01-30 13:30:21 -05003254static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon)
Trond Myklebustcf8d2c12009-06-22 15:09:13 -04003255{
3256 struct mnt_namespace *new_ns;
Eric W. Biederman537f7cc2016-08-08 14:37:37 -05003257 struct ucounts *ucounts;
Eric W. Biederman98f842e2011-06-15 10:21:48 -07003258 int ret;
Trond Myklebustcf8d2c12009-06-22 15:09:13 -04003259
Eric W. Biederman537f7cc2016-08-08 14:37:37 -05003260 ucounts = inc_mnt_namespaces(user_ns);
3261 if (!ucounts)
Eric W. Biedermandf75e772016-09-22 13:08:36 -05003262 return ERR_PTR(-ENOSPC);
Eric W. Biederman537f7cc2016-08-08 14:37:37 -05003263
Al Viro74e83122019-01-30 13:30:21 -05003264 new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
Eric W. Biederman537f7cc2016-08-08 14:37:37 -05003265 if (!new_ns) {
3266 dec_mnt_namespaces(ucounts);
Trond Myklebustcf8d2c12009-06-22 15:09:13 -04003267 return ERR_PTR(-ENOMEM);
Eric W. Biederman537f7cc2016-08-08 14:37:37 -05003268 }
Al Viro74e83122019-01-30 13:30:21 -05003269 if (!anon) {
3270 ret = ns_alloc_inum(&new_ns->ns);
3271 if (ret) {
3272 kfree(new_ns);
3273 dec_mnt_namespaces(ucounts);
3274 return ERR_PTR(ret);
3275 }
Eric W. Biederman98f842e2011-06-15 10:21:48 -07003276 }
Al Viro33c42942014-11-01 02:32:53 -04003277 new_ns->ns.ops = &mntns_operations;
Al Viro74e83122019-01-30 13:30:21 -05003278 if (!anon)
3279 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
Kirill Tkhai1a7b89692020-08-03 13:16:42 +03003280 refcount_set(&new_ns->ns.count, 1);
Trond Myklebustcf8d2c12009-06-22 15:09:13 -04003281 INIT_LIST_HEAD(&new_ns->list);
3282 init_waitqueue_head(&new_ns->poll);
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02003283 spin_lock_init(&new_ns->ns_lock);
Eric W. Biederman771b1372012-07-26 21:08:32 -07003284 new_ns->user_ns = get_user_ns(user_ns);
Eric W. Biederman537f7cc2016-08-08 14:37:37 -05003285 new_ns->ucounts = ucounts;
Trond Myklebustcf8d2c12009-06-22 15:09:13 -04003286 return new_ns;
3287}
3288
Emese Revfy0766f782016-06-20 20:42:34 +02003289__latent_entropy
Al Viro9559f682013-09-28 20:47:57 -04003290struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
3291 struct user_namespace *user_ns, struct fs_struct *new_fs)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003292{
Kirill Korotaev6b3286e2006-12-08 02:37:56 -08003293 struct mnt_namespace *new_ns;
Al Viro7f2da1e2008-05-10 20:44:54 -04003294 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
Al Viro315fc832011-11-24 18:57:30 -05003295 struct mount *p, *q;
Al Viro9559f682013-09-28 20:47:57 -04003296 struct mount *old;
Al Virocb338d02011-11-24 20:55:08 -05003297 struct mount *new;
Eric W. Biederman7a472ef2012-07-31 13:13:04 -07003298 int copy_flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003299
Al Viro9559f682013-09-28 20:47:57 -04003300 BUG_ON(!ns);
3301
3302 if (likely(!(flags & CLONE_NEWNS))) {
3303 get_mnt_ns(ns);
3304 return ns;
3305 }
3306
3307 old = ns->root;
3308
Al Viro74e83122019-01-30 13:30:21 -05003309 new_ns = alloc_mnt_ns(user_ns, false);
Trond Myklebustcf8d2c12009-06-22 15:09:13 -04003310 if (IS_ERR(new_ns))
3311 return new_ns;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003312
Al Viro97216be2013-03-16 15:12:40 -04003313 namespace_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003314 /* First pass: copy the tree topology */
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07003315 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
Al Viro9559f682013-09-28 20:47:57 -04003316 if (user_ns != ns->user_ns)
Al Viro3bd045c2019-01-30 13:15:45 -05003317 copy_flags |= CL_SHARED_TO_SLAVE;
Eric W. Biederman7a472ef2012-07-31 13:13:04 -07003318 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
David Howellsbe34d1a2012-06-25 12:55:18 +01003319 if (IS_ERR(new)) {
Al Viro328e6d92013-03-16 14:49:45 -04003320 namespace_unlock();
Eric W. Biederman771b1372012-07-26 21:08:32 -07003321 free_mnt_ns(new_ns);
David Howellsbe34d1a2012-06-25 12:55:18 +01003322 return ERR_CAST(new);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003323 }
Al Viro3bd045c2019-01-30 13:15:45 -05003324 if (user_ns != ns->user_ns) {
3325 lock_mount_hash();
3326 lock_mnt_tree(new);
3327 unlock_mount_hash();
3328 }
Al Virobe08d6d2011-12-06 13:32:36 -05003329 new_ns->root = new;
Al Viro1a4eeaf2011-11-25 02:19:55 -05003330 list_add_tail(&new_ns->list, &new->mnt_list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003331
3332 /*
3333 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3334 * as belonging to new namespace. We have already acquired a private
3335 * fs_struct, so tsk->fs->lock is not needed.
3336 */
Al Viro909b0a82011-11-25 03:06:56 -05003337 p = old;
Al Virocb338d02011-11-24 20:55:08 -05003338 q = new;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003339 while (p) {
Al Viro143c8c92011-11-25 00:46:35 -05003340 q->mnt_ns = new_ns;
Eric W. Biedermand2921682016-09-28 00:27:17 -05003341 new_ns->mounts++;
Al Viro9559f682013-09-28 20:47:57 -04003342 if (new_fs) {
3343 if (&p->mnt == new_fs->root.mnt) {
3344 new_fs->root.mnt = mntget(&q->mnt);
Al Viro315fc832011-11-24 18:57:30 -05003345 rootmnt = &p->mnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003346 }
Al Viro9559f682013-09-28 20:47:57 -04003347 if (&p->mnt == new_fs->pwd.mnt) {
3348 new_fs->pwd.mnt = mntget(&q->mnt);
Al Viro315fc832011-11-24 18:57:30 -05003349 pwdmnt = &p->mnt;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003350 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003351 }
Al Viro909b0a82011-11-25 03:06:56 -05003352 p = next_mnt(p, old);
3353 q = next_mnt(q, new);
Eric W. Biederman4ce5d2b2013-03-30 01:35:18 -07003354 if (!q)
3355 break;
3356 while (p->mnt.mnt_root != q->mnt.mnt_root)
3357 p = next_mnt(p, old);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003358 }
Al Viro328e6d92013-03-16 14:49:45 -04003359 namespace_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003360
Linus Torvalds1da177e2005-04-16 15:20:36 -07003361 if (rootmnt)
Al Virof03c6592011-01-14 22:30:21 -05003362 mntput(rootmnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003363 if (pwdmnt)
Al Virof03c6592011-01-14 22:30:21 -05003364 mntput(pwdmnt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003365
JANAK DESAI741a2952006-02-07 12:59:00 -08003366 return new_ns;
3367}
3368
Al Viro74e83122019-01-30 13:30:21 -05003369struct dentry *mount_subtree(struct vfsmount *m, const char *name)
Trond Myklebustcf8d2c12009-06-22 15:09:13 -04003370{
Al Viro74e83122019-01-30 13:30:21 -05003371 struct mount *mnt = real_mount(m);
Al Viroea441d12011-11-16 21:43:59 -05003372 struct mnt_namespace *ns;
Al Virod31da0f2011-11-22 12:31:21 -05003373 struct super_block *s;
Al Viroea441d12011-11-16 21:43:59 -05003374 struct path path;
3375 int err;
3376
Al Viro74e83122019-01-30 13:30:21 -05003377 ns = alloc_mnt_ns(&init_user_ns, true);
3378 if (IS_ERR(ns)) {
3379 mntput(m);
Al Viroea441d12011-11-16 21:43:59 -05003380 return ERR_CAST(ns);
Al Viro74e83122019-01-30 13:30:21 -05003381 }
3382 mnt->mnt_ns = ns;
3383 ns->root = mnt;
3384 ns->mounts++;
3385 list_add(&mnt->mnt_list, &ns->list);
Al Viroea441d12011-11-16 21:43:59 -05003386
Al Viro74e83122019-01-30 13:30:21 -05003387 err = vfs_path_lookup(m->mnt_root, m,
Al Viroea441d12011-11-16 21:43:59 -05003388 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
3389
3390 put_mnt_ns(ns);
3391
3392 if (err)
3393 return ERR_PTR(err);
3394
3395 /* trade a vfsmount reference for active sb one */
Al Virod31da0f2011-11-22 12:31:21 -05003396 s = path.mnt->mnt_sb;
3397 atomic_inc(&s->s_active);
Al Viroea441d12011-11-16 21:43:59 -05003398 mntput(path.mnt);
3399 /* lock the sucker */
Al Virod31da0f2011-11-22 12:31:21 -05003400 down_write(&s->s_umount);
Al Viroea441d12011-11-16 21:43:59 -05003401 /* ... and return the root of (sub)tree on it */
3402 return path.dentry;
3403}
3404EXPORT_SYMBOL(mount_subtree);
3405
Dominik Brodowskicccaa5e2018-10-23 22:41:09 +02003406SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
3407 char __user *, type, unsigned long, flags, void __user *, data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003408{
Vegard Nossumeca6f532009-09-18 13:05:45 -07003409 int ret;
3410 char *kernel_type;
Vegard Nossumeca6f532009-09-18 13:05:45 -07003411 char *kernel_dev;
Al Virob40ef862015-12-14 18:44:44 -05003412 void *options;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003413
Tim Gardnerb8850d12014-08-28 11:26:03 -06003414 kernel_type = copy_mount_string(type);
3415 ret = PTR_ERR(kernel_type);
3416 if (IS_ERR(kernel_type))
Vegard Nossumeca6f532009-09-18 13:05:45 -07003417 goto out_type;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003418
Tim Gardnerb8850d12014-08-28 11:26:03 -06003419 kernel_dev = copy_mount_string(dev_name);
3420 ret = PTR_ERR(kernel_dev);
3421 if (IS_ERR(kernel_dev))
Vegard Nossumeca6f532009-09-18 13:05:45 -07003422 goto out_dev;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003423
Al Virob40ef862015-12-14 18:44:44 -05003424 options = copy_mount_options(data);
3425 ret = PTR_ERR(options);
3426 if (IS_ERR(options))
Vegard Nossumeca6f532009-09-18 13:05:45 -07003427 goto out_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003428
Al Virob40ef862015-12-14 18:44:44 -05003429 ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options);
Vegard Nossumeca6f532009-09-18 13:05:45 -07003430
Al Virob40ef862015-12-14 18:44:44 -05003431 kfree(options);
Vegard Nossumeca6f532009-09-18 13:05:45 -07003432out_data:
3433 kfree(kernel_dev);
3434out_dev:
Vegard Nossumeca6f532009-09-18 13:05:45 -07003435 kfree(kernel_type);
3436out_type:
3437 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003438}
3439
3440/*
David Howells93766fb2018-11-01 23:36:14 +00003441 * Create a kernel mount representation for a new, prepared superblock
3442 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3443 */
3444SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
3445 unsigned int, attr_flags)
3446{
3447 struct mnt_namespace *ns;
3448 struct fs_context *fc;
3449 struct file *file;
3450 struct path newmount;
3451 struct mount *mnt;
3452 struct fd f;
3453 unsigned int mnt_flags = 0;
3454 long ret;
3455
3456 if (!may_mount())
3457 return -EPERM;
3458
3459 if ((flags & ~(FSMOUNT_CLOEXEC)) != 0)
3460 return -EINVAL;
3461
3462 if (attr_flags & ~(MOUNT_ATTR_RDONLY |
3463 MOUNT_ATTR_NOSUID |
3464 MOUNT_ATTR_NODEV |
3465 MOUNT_ATTR_NOEXEC |
3466 MOUNT_ATTR__ATIME |
3467 MOUNT_ATTR_NODIRATIME))
3468 return -EINVAL;
3469
3470 if (attr_flags & MOUNT_ATTR_RDONLY)
3471 mnt_flags |= MNT_READONLY;
3472 if (attr_flags & MOUNT_ATTR_NOSUID)
3473 mnt_flags |= MNT_NOSUID;
3474 if (attr_flags & MOUNT_ATTR_NODEV)
3475 mnt_flags |= MNT_NODEV;
3476 if (attr_flags & MOUNT_ATTR_NOEXEC)
3477 mnt_flags |= MNT_NOEXEC;
3478 if (attr_flags & MOUNT_ATTR_NODIRATIME)
3479 mnt_flags |= MNT_NODIRATIME;
3480
3481 switch (attr_flags & MOUNT_ATTR__ATIME) {
3482 case MOUNT_ATTR_STRICTATIME:
3483 break;
3484 case MOUNT_ATTR_NOATIME:
3485 mnt_flags |= MNT_NOATIME;
3486 break;
3487 case MOUNT_ATTR_RELATIME:
3488 mnt_flags |= MNT_RELATIME;
3489 break;
3490 default:
3491 return -EINVAL;
3492 }
3493
3494 f = fdget(fs_fd);
3495 if (!f.file)
3496 return -EBADF;
3497
3498 ret = -EINVAL;
3499 if (f.file->f_op != &fscontext_fops)
3500 goto err_fsfd;
3501
3502 fc = f.file->private_data;
3503
3504 ret = mutex_lock_interruptible(&fc->uapi_mutex);
3505 if (ret < 0)
3506 goto err_fsfd;
3507
3508 /* There must be a valid superblock or we can't mount it */
3509 ret = -EINVAL;
3510 if (!fc->root)
3511 goto err_unlock;
3512
3513 ret = -EPERM;
3514 if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
3515 pr_warn("VFS: Mount too revealing\n");
3516 goto err_unlock;
3517 }
3518
3519 ret = -EBUSY;
3520 if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
3521 goto err_unlock;
3522
3523 ret = -EPERM;
3524 if ((fc->sb_flags & SB_MANDLOCK) && !may_mandlock())
3525 goto err_unlock;
3526
3527 newmount.mnt = vfs_create_mount(fc);
3528 if (IS_ERR(newmount.mnt)) {
3529 ret = PTR_ERR(newmount.mnt);
3530 goto err_unlock;
3531 }
3532 newmount.dentry = dget(fc->root);
3533 newmount.mnt->mnt_flags = mnt_flags;
3534
3535 /* We've done the mount bit - now move the file context into more or
3536 * less the same state as if we'd done an fspick(). We don't want to
3537 * do any memory allocation or anything like that at this point as we
3538 * don't want to have to handle any errors incurred.
3539 */
3540 vfs_clean_context(fc);
3541
3542 ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true);
3543 if (IS_ERR(ns)) {
3544 ret = PTR_ERR(ns);
3545 goto err_path;
3546 }
3547 mnt = real_mount(newmount.mnt);
3548 mnt->mnt_ns = ns;
3549 ns->root = mnt;
3550 ns->mounts = 1;
3551 list_add(&mnt->mnt_list, &ns->list);
Eric Biggers1b0b9cc2019-06-12 11:43:13 -07003552 mntget(newmount.mnt);
David Howells93766fb2018-11-01 23:36:14 +00003553
3554 /* Attach to an apparent O_PATH fd with a note that we need to unmount
3555 * it, not just simply put it.
3556 */
3557 file = dentry_open(&newmount, O_PATH, fc->cred);
3558 if (IS_ERR(file)) {
3559 dissolve_on_fput(newmount.mnt);
3560 ret = PTR_ERR(file);
3561 goto err_path;
3562 }
3563 file->f_mode |= FMODE_NEED_UNMOUNT;
3564
3565 ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
3566 if (ret >= 0)
3567 fd_install(ret, file);
3568 else
3569 fput(file);
3570
3571err_path:
3572 path_put(&newmount);
3573err_unlock:
3574 mutex_unlock(&fc->uapi_mutex);
3575err_fsfd:
3576 fdput(f);
3577 return ret;
3578}
3579
3580/*
3581 * Move a mount from one place to another. In combination with
3582 * fsopen()/fsmount() this is used to install a new mount and in combination
3583 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
3584 * a mount subtree.
David Howells2db154b2018-11-05 17:40:30 +00003585 *
3586 * Note the flags value is a combination of MOVE_MOUNT_* flags.
3587 */
3588SYSCALL_DEFINE5(move_mount,
Ben Dooks2658ce02019-10-15 11:35:02 +01003589 int, from_dfd, const char __user *, from_pathname,
3590 int, to_dfd, const char __user *, to_pathname,
David Howells2db154b2018-11-05 17:40:30 +00003591 unsigned int, flags)
3592{
3593 struct path from_path, to_path;
3594 unsigned int lflags;
3595 int ret = 0;
3596
3597 if (!may_mount())
3598 return -EPERM;
3599
3600 if (flags & ~MOVE_MOUNT__MASK)
3601 return -EINVAL;
3602
3603 /* If someone gives a pathname, they aren't permitted to move
3604 * from an fd that requires unmount as we can't get at the flag
3605 * to clear it afterwards.
3606 */
3607 lflags = 0;
3608 if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3609 if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3610 if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3611
3612 ret = user_path_at(from_dfd, from_pathname, lflags, &from_path);
3613 if (ret < 0)
3614 return ret;
3615
3616 lflags = 0;
3617 if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3618 if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3619 if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3620
3621 ret = user_path_at(to_dfd, to_pathname, lflags, &to_path);
3622 if (ret < 0)
3623 goto out_from;
3624
3625 ret = security_move_mount(&from_path, &to_path);
3626 if (ret < 0)
3627 goto out_to;
3628
3629 ret = do_move_mount(&from_path, &to_path);
3630
3631out_to:
3632 path_put(&to_path);
3633out_from:
3634 path_put(&from_path);
3635 return ret;
3636}
3637
3638/*
Al Viroafac7cb2011-11-23 19:34:49 -05003639 * Return true if path is reachable from root
3640 *
Al Viro48a066e2013-09-29 22:06:07 -04003641 * namespace_sem or mount_lock is held
Al Viroafac7cb2011-11-23 19:34:49 -05003642 */
Al Viro643822b2011-11-24 22:00:28 -05003643bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
Al Viroafac7cb2011-11-23 19:34:49 -05003644 const struct path *root)
3645{
Al Viro643822b2011-11-24 22:00:28 -05003646 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
Al Viroa73324d2011-11-24 22:25:07 -05003647 dentry = mnt->mnt_mountpoint;
Al Viro0714a532011-11-24 22:19:58 -05003648 mnt = mnt->mnt_parent;
Al Viroafac7cb2011-11-23 19:34:49 -05003649 }
Al Viro643822b2011-11-24 22:00:28 -05003650 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
Al Viroafac7cb2011-11-23 19:34:49 -05003651}
3652
Mickaël Salaün640eb7e2016-11-14 22:14:35 +01003653bool path_is_under(const struct path *path1, const struct path *path2)
Al Viroafac7cb2011-11-23 19:34:49 -05003654{
Yaowei Bai25ab4c92015-11-17 14:40:10 +08003655 bool res;
Al Viro48a066e2013-09-29 22:06:07 -04003656 read_seqlock_excl(&mount_lock);
Al Viro643822b2011-11-24 22:00:28 -05003657 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
Al Viro48a066e2013-09-29 22:06:07 -04003658 read_sequnlock_excl(&mount_lock);
Al Viroafac7cb2011-11-23 19:34:49 -05003659 return res;
3660}
3661EXPORT_SYMBOL(path_is_under);
3662
3663/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07003664 * pivot_root Semantics:
3665 * Moves the root file system of the current process to the directory put_old,
3666 * makes new_root as the new root file system of the current process, and sets
3667 * root/cwd of all processes which had them on the current root to new_root.
3668 *
3669 * Restrictions:
3670 * The new_root and put_old must be directories, and must not be on the
3671 * same file system as the current process root. The put_old must be
3672 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3673 * pointed to by put_old must yield the same directory as new_root. No other
3674 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3675 *
Neil Brown4a0d11f2006-01-08 01:03:18 -08003676 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
Mauro Carvalho Chehab0c1bc6b2020-04-14 18:48:37 +02003677 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
Neil Brown4a0d11f2006-01-08 01:03:18 -08003678 * in this situation.
3679 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07003680 * Notes:
3681 * - we don't move root/cwd if they are not at the root (reason: if something
3682 * cared enough to change them, it's probably wrong to force them elsewhere)
3683 * - it's okay to pick a root that isn't the root of a file system, e.g.
3684 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3685 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3686 * first.
3687 */
Heiko Carstens3480b252009-01-14 14:14:16 +01003688SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
3689 const char __user *, put_old)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003690{
Al Viro2763d112019-06-30 19:18:53 -04003691 struct path new, old, root;
3692 struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent;
Al Viro84d17192013-03-15 10:53:28 -04003693 struct mountpoint *old_mp, *root_mp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003694 int error;
3695
Al Viro9b40bc92013-02-22 22:45:42 -05003696 if (!may_mount())
Linus Torvalds1da177e2005-04-16 15:20:36 -07003697 return -EPERM;
3698
Al Viroce6595a2019-07-14 16:42:44 -04003699 error = user_path_at(AT_FDCWD, new_root,
3700 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003701 if (error)
3702 goto out0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003703
Al Viroce6595a2019-07-14 16:42:44 -04003704 error = user_path_at(AT_FDCWD, put_old,
3705 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003706 if (error)
3707 goto out1;
3708
Al Viro2d8f3032008-07-22 09:59:21 -04003709 error = security_sb_pivotroot(&old, &new);
Al Virob12cea92011-03-18 08:55:38 -04003710 if (error)
3711 goto out2;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003712
Miklos Szeredif7ad3c62010-08-10 11:41:36 +02003713 get_fs_root(current->fs, &root);
Al Viro84d17192013-03-15 10:53:28 -04003714 old_mp = lock_mount(&old);
3715 error = PTR_ERR(old_mp);
3716 if (IS_ERR(old_mp))
Al Virob12cea92011-03-18 08:55:38 -04003717 goto out3;
3718
Linus Torvalds1da177e2005-04-16 15:20:36 -07003719 error = -EINVAL;
Al Viro419148d2011-11-24 19:41:16 -05003720 new_mnt = real_mount(new.mnt);
3721 root_mnt = real_mount(root.mnt);
Al Viro84d17192013-03-15 10:53:28 -04003722 old_mnt = real_mount(old.mnt);
Al Viro2763d112019-06-30 19:18:53 -04003723 ex_parent = new_mnt->mnt_parent;
3724 root_parent = root_mnt->mnt_parent;
Al Viro84d17192013-03-15 10:53:28 -04003725 if (IS_MNT_SHARED(old_mnt) ||
Al Viro2763d112019-06-30 19:18:53 -04003726 IS_MNT_SHARED(ex_parent) ||
3727 IS_MNT_SHARED(root_parent))
Al Virob12cea92011-03-18 08:55:38 -04003728 goto out4;
Al Viro143c8c92011-11-25 00:46:35 -05003729 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
Al Virob12cea92011-03-18 08:55:38 -04003730 goto out4;
Eric W. Biederman5ff9d8a2013-03-29 21:04:39 -07003731 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
3732 goto out4;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003733 error = -ENOENT;
Alexey Dobriyanf3da3922009-05-04 03:32:03 +04003734 if (d_unlinked(new.dentry))
Al Virob12cea92011-03-18 08:55:38 -04003735 goto out4;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003736 error = -EBUSY;
Al Viro84d17192013-03-15 10:53:28 -04003737 if (new_mnt == root_mnt || old_mnt == root_mnt)
Al Virob12cea92011-03-18 08:55:38 -04003738 goto out4; /* loop, on the same file system */
Linus Torvalds1da177e2005-04-16 15:20:36 -07003739 error = -EINVAL;
Al Viro8c3ee422008-03-22 18:00:39 -04003740 if (root.mnt->mnt_root != root.dentry)
Al Virob12cea92011-03-18 08:55:38 -04003741 goto out4; /* not a mountpoint */
Al Viro676da582011-11-24 21:47:05 -05003742 if (!mnt_has_parent(root_mnt))
Al Virob12cea92011-03-18 08:55:38 -04003743 goto out4; /* not attached */
Al Viro2d8f3032008-07-22 09:59:21 -04003744 if (new.mnt->mnt_root != new.dentry)
Al Virob12cea92011-03-18 08:55:38 -04003745 goto out4; /* not a mountpoint */
Al Viro676da582011-11-24 21:47:05 -05003746 if (!mnt_has_parent(new_mnt))
Al Virob12cea92011-03-18 08:55:38 -04003747 goto out4; /* not attached */
Jan Blunck4ac91372008-02-14 19:34:32 -08003748 /* make sure we can reach put_old from new_root */
Al Viro84d17192013-03-15 10:53:28 -04003749 if (!is_path_reachable(old_mnt, old.dentry, &new))
Al Virob12cea92011-03-18 08:55:38 -04003750 goto out4;
Eric W. Biederman0d082602014-10-08 10:42:27 -07003751 /* make certain new is below the root */
3752 if (!is_path_reachable(new_mnt, new.dentry, &root))
3753 goto out4;
Al Viro719ea2f2013-09-29 11:24:49 -04003754 lock_mount_hash();
Al Viro2763d112019-06-30 19:18:53 -04003755 umount_mnt(new_mnt);
3756 root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */
Eric W. Biederman5ff9d8a2013-03-29 21:04:39 -07003757 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
3758 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
3759 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
3760 }
Jan Blunck4ac91372008-02-14 19:34:32 -08003761 /* mount old root on put_old */
Al Viro84d17192013-03-15 10:53:28 -04003762 attach_mnt(root_mnt, old_mnt, old_mp);
Jan Blunck4ac91372008-02-14 19:34:32 -08003763 /* mount new_root on / */
Al Viro2763d112019-06-30 19:18:53 -04003764 attach_mnt(new_mnt, root_parent, root_mp);
3765 mnt_add_count(root_parent, -1);
Kirill Korotaev6b3286e2006-12-08 02:37:56 -08003766 touch_mnt_namespace(current->nsproxy->mnt_ns);
Eric W. Biederman4fed6552014-10-08 10:42:57 -07003767 /* A moved mount should not expire automatically */
3768 list_del_init(&new_mnt->mnt_expire);
Eric W. Biederman3895dbf2017-01-03 14:18:43 +13003769 put_mountpoint(root_mp);
Al Viro719ea2f2013-09-29 11:24:49 -04003770 unlock_mount_hash();
Al Viro2d8f3032008-07-22 09:59:21 -04003771 chroot_fs_refs(&root, &new);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003772 error = 0;
Al Virob12cea92011-03-18 08:55:38 -04003773out4:
Al Viro84d17192013-03-15 10:53:28 -04003774 unlock_mount(old_mp);
Al Viro2763d112019-06-30 19:18:53 -04003775 if (!error)
3776 mntput_no_expire(ex_parent);
Al Virob12cea92011-03-18 08:55:38 -04003777out3:
Al Viro8c3ee422008-03-22 18:00:39 -04003778 path_put(&root);
Al Virob12cea92011-03-18 08:55:38 -04003779out2:
Al Viro2d8f3032008-07-22 09:59:21 -04003780 path_put(&old);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003781out1:
Al Viro2d8f3032008-07-22 09:59:21 -04003782 path_put(&new);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003783out0:
Linus Torvalds1da177e2005-04-16 15:20:36 -07003784 return error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003785}
3786
3787static void __init init_mount_tree(void)
3788{
3789 struct vfsmount *mnt;
Al Viro74e83122019-01-30 13:30:21 -05003790 struct mount *m;
Kirill Korotaev6b3286e2006-12-08 02:37:56 -08003791 struct mnt_namespace *ns;
Jan Blunckac748a02008-02-14 19:34:39 -08003792 struct path root;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003793
Al Virofd3e0072019-05-30 17:48:35 -04003794 mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003795 if (IS_ERR(mnt))
3796 panic("Can't create rootfs");
Nick Pigginb3e19d92011-01-07 17:50:11 +11003797
Al Viro74e83122019-01-30 13:30:21 -05003798 ns = alloc_mnt_ns(&init_user_ns, false);
Trond Myklebust3b22edc2009-06-23 17:29:49 -04003799 if (IS_ERR(ns))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003800 panic("Can't allocate initial namespace");
Al Viro74e83122019-01-30 13:30:21 -05003801 m = real_mount(mnt);
3802 m->mnt_ns = ns;
3803 ns->root = m;
3804 ns->mounts = 1;
3805 list_add(&m->mnt_list, &ns->list);
Kirill Korotaev6b3286e2006-12-08 02:37:56 -08003806 init_task.nsproxy->mnt_ns = ns;
3807 get_mnt_ns(ns);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003808
Al Virobe08d6d2011-12-06 13:32:36 -05003809 root.mnt = mnt;
3810 root.dentry = mnt->mnt_root;
Eric W. Biedermanda362b02014-10-07 12:19:53 -07003811 mnt->mnt_flags |= MNT_LOCKED;
Jan Blunckac748a02008-02-14 19:34:39 -08003812
3813 set_fs_pwd(current->fs, &root);
3814 set_fs_root(current->fs, &root);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003815}
3816
Denis Cheng74bf17c2007-10-16 23:26:30 -07003817void __init mnt_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003818{
Randy Dunlap15a67dd2006-09-29 01:58:57 -07003819 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003820
Al Viro7d6fec42011-11-23 12:14:10 -05003821 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
Paul Mundt20c2df82007-07-20 10:11:58 +09003822 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003823
Al Viro0818bf22014-02-28 13:46:44 -05003824 mount_hashtable = alloc_large_system_hash("Mount-cache",
Al Viro38129a12014-03-20 21:10:51 -04003825 sizeof(struct hlist_head),
Al Viro0818bf22014-02-28 13:46:44 -05003826 mhash_entries, 19,
Pavel Tatashin3d375d72017-07-06 15:39:11 -07003827 HASH_ZERO,
Al Viro0818bf22014-02-28 13:46:44 -05003828 &m_hash_shift, &m_hash_mask, 0, 0);
3829 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
3830 sizeof(struct hlist_head),
3831 mphash_entries, 19,
Pavel Tatashin3d375d72017-07-06 15:39:11 -07003832 HASH_ZERO,
Al Viro0818bf22014-02-28 13:46:44 -05003833 &mp_hash_shift, &mp_hash_mask, 0, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003834
Al Viro84d17192013-03-15 10:53:28 -04003835 if (!mount_hashtable || !mountpoint_hashtable)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003836 panic("Failed to allocate mount hash table\n");
3837
Tejun Heo4b93dc92013-11-28 14:54:43 -05003838 kernfs_init();
3839
Randy Dunlap15a67dd2006-09-29 01:58:57 -07003840 err = sysfs_init();
3841 if (err)
3842 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -07003843 __func__, err);
Greg Kroah-Hartman00d26662007-10-29 14:17:23 -06003844 fs_kobj = kobject_create_and_add("fs", NULL);
3845 if (!fs_kobj)
Harvey Harrison8e24eea2008-04-30 00:55:09 -07003846 printk(KERN_WARNING "%s: kobj create error\n", __func__);
Al Viro037f11b2019-06-01 18:09:44 -04003847 shmem_init();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003848 init_rootfs();
3849 init_mount_tree();
3850}
3851
Trond Myklebust616511d2009-06-22 15:09:13 -04003852void put_mnt_ns(struct mnt_namespace *ns)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003853{
Kirill Tkhai1a7b89692020-08-03 13:16:42 +03003854 if (!refcount_dec_and_test(&ns->ns.count))
Trond Myklebust616511d2009-06-22 15:09:13 -04003855 return;
Al Viro7b00ed62013-09-16 21:19:20 -04003856 drop_collected_mounts(&ns->root->mnt);
Eric W. Biederman771b1372012-07-26 21:08:32 -07003857 free_mnt_ns(ns);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003858}
Al Viro9d412a42011-03-17 22:08:28 -04003859
David Howellsd911b452018-11-01 23:07:26 +00003860struct vfsmount *kern_mount(struct file_system_type *type)
Al Viro9d412a42011-03-17 22:08:28 -04003861{
Tim Chen423e0ab2011-07-19 09:32:38 -07003862 struct vfsmount *mnt;
David Howellsd911b452018-11-01 23:07:26 +00003863 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
Tim Chen423e0ab2011-07-19 09:32:38 -07003864 if (!IS_ERR(mnt)) {
3865 /*
3866 * it is a longterm mount, don't release mnt until
3867 * we unmount before file sys is unregistered
3868 */
Al Virof7a99c52012-06-09 00:59:08 -04003869 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
Tim Chen423e0ab2011-07-19 09:32:38 -07003870 }
3871 return mnt;
Al Viro9d412a42011-03-17 22:08:28 -04003872}
David Howellsd911b452018-11-01 23:07:26 +00003873EXPORT_SYMBOL_GPL(kern_mount);
Tim Chen423e0ab2011-07-19 09:32:38 -07003874
3875void kern_unmount(struct vfsmount *mnt)
3876{
3877 /* release long term mount so mount point can be released */
3878 if (!IS_ERR_OR_NULL(mnt)) {
Al Virof7a99c52012-06-09 00:59:08 -04003879 real_mount(mnt)->mnt_ns = NULL;
Al Viro48a066e2013-09-29 22:06:07 -04003880 synchronize_rcu(); /* yecchhh... */
Tim Chen423e0ab2011-07-19 09:32:38 -07003881 mntput(mnt);
3882 }
3883}
3884EXPORT_SYMBOL(kern_unmount);
Al Viro02125a82011-12-05 08:43:34 -05003885
Miklos Szeredidf820f82020-06-04 10:48:19 +02003886void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
3887{
3888 unsigned int i;
3889
3890 for (i = 0; i < num; i++)
3891 if (mnt[i])
3892 real_mount(mnt[i])->mnt_ns = NULL;
3893 synchronize_rcu_expedited();
3894 for (i = 0; i < num; i++)
3895 mntput(mnt[i]);
3896}
3897EXPORT_SYMBOL(kern_unmount_array);
3898
Al Viro02125a82011-12-05 08:43:34 -05003899bool our_mnt(struct vfsmount *mnt)
3900{
Al Viro143c8c92011-11-25 00:46:35 -05003901 return check_mnt(real_mount(mnt));
Al Viro02125a82011-12-05 08:43:34 -05003902}
Eric W. Biederman8823c072010-03-07 18:49:36 -08003903
Eric W. Biederman31515272013-03-15 01:45:51 -07003904bool current_chrooted(void)
3905{
3906 /* Does the current process have a non-standard root */
3907 struct path ns_root;
3908 struct path fs_root;
3909 bool chrooted;
3910
3911 /* Find the namespace root */
3912 ns_root.mnt = &current->nsproxy->mnt_ns->root->mnt;
3913 ns_root.dentry = ns_root.mnt->mnt_root;
3914 path_get(&ns_root);
3915 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
3916 ;
3917
3918 get_fs_root(current->fs, &fs_root);
3919
3920 chrooted = !path_equal(&fs_root, &ns_root);
3921
3922 path_put(&fs_root);
3923 path_put(&ns_root);
3924
3925 return chrooted;
3926}
3927
David Howells132e4602018-11-04 07:43:08 -05003928static bool mnt_already_visible(struct mnt_namespace *ns,
3929 const struct super_block *sb,
Eric W. Biederman8654df42016-06-09 16:06:06 -05003930 int *new_mnt_flags)
Eric W. Biederman87a8ebd2013-03-24 14:28:27 -07003931{
Eric W. Biederman8c6cf9c2015-05-08 23:49:47 -05003932 int new_flags = *new_mnt_flags;
Eric W. Biederman87a8ebd2013-03-24 14:28:27 -07003933 struct mount *mnt;
Eric W. Biedermane51db732013-03-30 19:57:41 -07003934 bool visible = false;
Eric W. Biederman87a8ebd2013-03-24 14:28:27 -07003935
Al Viro44bb4382013-09-16 21:37:36 -04003936 down_read(&namespace_sem);
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02003937 lock_ns_list(ns);
Eric W. Biederman87a8ebd2013-03-24 14:28:27 -07003938 list_for_each_entry(mnt, &ns->list, mnt_list) {
Eric W. Biedermane51db732013-03-30 19:57:41 -07003939 struct mount *child;
Eric W. Biederman77b1a972015-06-04 09:43:11 -05003940 int mnt_flags;
3941
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02003942 if (mnt_is_cursor(mnt))
3943 continue;
3944
David Howells132e4602018-11-04 07:43:08 -05003945 if (mnt->mnt.mnt_sb->s_type != sb->s_type)
Eric W. Biedermane51db732013-03-30 19:57:41 -07003946 continue;
3947
Eric W. Biederman7e96c1b2015-05-08 16:36:50 -05003948 /* This mount is not fully visible if it's root directory
3949 * is not the root directory of the filesystem.
3950 */
3951 if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
3952 continue;
3953
Eric W. Biedermana1935c12016-06-15 06:59:49 -05003954 /* A local view of the mount flags */
Eric W. Biederman77b1a972015-06-04 09:43:11 -05003955 mnt_flags = mnt->mnt.mnt_flags;
Eric W. Biederman77b1a972015-06-04 09:43:11 -05003956
Eric W. Biederman695e9df2016-06-10 12:21:40 -05003957 /* Don't miss readonly hidden in the superblock flags */
David Howellsbc98a422017-07-17 08:45:34 +01003958 if (sb_rdonly(mnt->mnt.mnt_sb))
Eric W. Biederman695e9df2016-06-10 12:21:40 -05003959 mnt_flags |= MNT_LOCK_READONLY;
3960
Eric W. Biederman8c6cf9c2015-05-08 23:49:47 -05003961 /* Verify the mount flags are equal to or more permissive
3962 * than the proposed new mount.
3963 */
Eric W. Biederman77b1a972015-06-04 09:43:11 -05003964 if ((mnt_flags & MNT_LOCK_READONLY) &&
Eric W. Biederman8c6cf9c2015-05-08 23:49:47 -05003965 !(new_flags & MNT_READONLY))
3966 continue;
Eric W. Biederman77b1a972015-06-04 09:43:11 -05003967 if ((mnt_flags & MNT_LOCK_ATIME) &&
3968 ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
Eric W. Biederman8c6cf9c2015-05-08 23:49:47 -05003969 continue;
3970
Eric W. Biedermanceeb0e52015-01-07 08:10:09 -06003971 /* This mount is not fully visible if there are any
3972 * locked child mounts that cover anything except for
3973 * empty directories.
Eric W. Biedermane51db732013-03-30 19:57:41 -07003974 */
3975 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
3976 struct inode *inode = child->mnt_mountpoint->d_inode;
Eric W. Biedermanceeb0e52015-01-07 08:10:09 -06003977 /* Only worry about locked mounts */
Eric W. Biedermand71ed6c2016-05-27 14:50:05 -05003978 if (!(child->mnt.mnt_flags & MNT_LOCKED))
Eric W. Biedermanceeb0e52015-01-07 08:10:09 -06003979 continue;
Eric W. Biederman7236c852015-05-13 20:51:09 -05003980 /* Is the directory permanetly empty? */
3981 if (!is_empty_dir_inode(inode))
Eric W. Biedermane51db732013-03-30 19:57:41 -07003982 goto next;
Eric W. Biederman87a8ebd2013-03-24 14:28:27 -07003983 }
Eric W. Biederman8c6cf9c2015-05-08 23:49:47 -05003984 /* Preserve the locked attributes */
Eric W. Biederman77b1a972015-06-04 09:43:11 -05003985 *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
Eric W. Biederman77b1a972015-06-04 09:43:11 -05003986 MNT_LOCK_ATIME);
Eric W. Biedermane51db732013-03-30 19:57:41 -07003987 visible = true;
3988 goto found;
3989 next: ;
Eric W. Biederman87a8ebd2013-03-24 14:28:27 -07003990 }
Eric W. Biedermane51db732013-03-30 19:57:41 -07003991found:
Miklos Szeredi9f6c61f2020-05-14 16:44:24 +02003992 unlock_ns_list(ns);
Al Viro44bb4382013-09-16 21:37:36 -04003993 up_read(&namespace_sem);
Eric W. Biedermane51db732013-03-30 19:57:41 -07003994 return visible;
Eric W. Biederman87a8ebd2013-03-24 14:28:27 -07003995}
3996
David Howells132e4602018-11-04 07:43:08 -05003997static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
Eric W. Biederman8654df42016-06-09 16:06:06 -05003998{
Eric W. Biedermana1935c12016-06-15 06:59:49 -05003999 const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
Eric W. Biederman8654df42016-06-09 16:06:06 -05004000 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
4001 unsigned long s_iflags;
4002
4003 if (ns->user_ns == &init_user_ns)
4004 return false;
4005
4006 /* Can this filesystem be too revealing? */
David Howells132e4602018-11-04 07:43:08 -05004007 s_iflags = sb->s_iflags;
Eric W. Biederman8654df42016-06-09 16:06:06 -05004008 if (!(s_iflags & SB_I_USERNS_VISIBLE))
4009 return false;
4010
Eric W. Biedermana1935c12016-06-15 06:59:49 -05004011 if ((s_iflags & required_iflags) != required_iflags) {
4012 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
4013 required_iflags);
4014 return true;
4015 }
4016
David Howells132e4602018-11-04 07:43:08 -05004017 return !mnt_already_visible(ns, sb, new_mnt_flags);
Eric W. Biederman8654df42016-06-09 16:06:06 -05004018}
4019
Andy Lutomirski380cf5b2016-06-23 16:41:05 -05004020bool mnt_may_suid(struct vfsmount *mnt)
4021{
4022 /*
4023 * Foreign mounts (accessed via fchdir or through /proc
4024 * symlinks) are always treated as if they are nosuid. This
4025 * prevents namespaces from trusting potentially unsafe
4026 * suid/sgid bits, file caps, or security labels that originate
4027 * in other namespaces.
4028 */
4029 return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
4030 current_in_userns(mnt->mnt_sb->s_user_ns);
4031}
4032
Al Viro64964522014-11-01 00:37:32 -04004033static struct ns_common *mntns_get(struct task_struct *task)
Eric W. Biederman8823c072010-03-07 18:49:36 -08004034{
Al Viro58be28252014-11-01 00:00:23 -04004035 struct ns_common *ns = NULL;
Eric W. Biederman8823c072010-03-07 18:49:36 -08004036 struct nsproxy *nsproxy;
4037
Eric W. Biederman728dba32014-02-03 19:13:49 -08004038 task_lock(task);
4039 nsproxy = task->nsproxy;
Eric W. Biederman8823c072010-03-07 18:49:36 -08004040 if (nsproxy) {
Al Viro58be28252014-11-01 00:00:23 -04004041 ns = &nsproxy->mnt_ns->ns;
4042 get_mnt_ns(to_mnt_ns(ns));
Eric W. Biederman8823c072010-03-07 18:49:36 -08004043 }
Eric W. Biederman728dba32014-02-03 19:13:49 -08004044 task_unlock(task);
Eric W. Biederman8823c072010-03-07 18:49:36 -08004045
4046 return ns;
4047}
4048
Al Viro64964522014-11-01 00:37:32 -04004049static void mntns_put(struct ns_common *ns)
Eric W. Biederman8823c072010-03-07 18:49:36 -08004050{
Al Viro58be28252014-11-01 00:00:23 -04004051 put_mnt_ns(to_mnt_ns(ns));
Eric W. Biederman8823c072010-03-07 18:49:36 -08004052}
4053
Christian Braunerf2a8d522020-05-05 16:04:30 +02004054static int mntns_install(struct nsset *nsset, struct ns_common *ns)
Eric W. Biederman8823c072010-03-07 18:49:36 -08004055{
Christian Braunerf2a8d522020-05-05 16:04:30 +02004056 struct nsproxy *nsproxy = nsset->nsproxy;
4057 struct fs_struct *fs = nsset->fs;
Al Viro4f757f32017-04-15 17:31:22 -04004058 struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
Christian Braunerf2a8d522020-05-05 16:04:30 +02004059 struct user_namespace *user_ns = nsset->cred->user_ns;
Eric W. Biederman8823c072010-03-07 18:49:36 -08004060 struct path root;
Al Viro4f757f32017-04-15 17:31:22 -04004061 int err;
Eric W. Biederman8823c072010-03-07 18:49:36 -08004062
Eric W. Biederman0c55cfc2012-07-26 21:42:03 -07004063 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
Christian Braunerf2a8d522020-05-05 16:04:30 +02004064 !ns_capable(user_ns, CAP_SYS_CHROOT) ||
4065 !ns_capable(user_ns, CAP_SYS_ADMIN))
Zhao Hongjiangae11e0f2012-09-13 16:38:03 +08004066 return -EPERM;
Eric W. Biederman8823c072010-03-07 18:49:36 -08004067
Al Viro74e83122019-01-30 13:30:21 -05004068 if (is_anon_ns(mnt_ns))
4069 return -EINVAL;
4070
Eric W. Biederman8823c072010-03-07 18:49:36 -08004071 if (fs->users != 1)
4072 return -EINVAL;
4073
4074 get_mnt_ns(mnt_ns);
Al Viro4f757f32017-04-15 17:31:22 -04004075 old_mnt_ns = nsproxy->mnt_ns;
Eric W. Biederman8823c072010-03-07 18:49:36 -08004076 nsproxy->mnt_ns = mnt_ns;
4077
4078 /* Find the root */
Al Viro4f757f32017-04-15 17:31:22 -04004079 err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
4080 "/", LOOKUP_DOWN, &root);
4081 if (err) {
4082 /* revert to old namespace */
4083 nsproxy->mnt_ns = old_mnt_ns;
4084 put_mnt_ns(mnt_ns);
4085 return err;
4086 }
Eric W. Biederman8823c072010-03-07 18:49:36 -08004087
Andrei Vagin40683672017-06-08 17:32:29 -07004088 put_mnt_ns(old_mnt_ns);
4089
Eric W. Biederman8823c072010-03-07 18:49:36 -08004090 /* Update the pwd and root */
4091 set_fs_pwd(fs, &root);
4092 set_fs_root(fs, &root);
4093
4094 path_put(&root);
4095 return 0;
4096}
4097
Andrey Vaginbcac25a2016-09-06 00:47:13 -07004098static struct user_namespace *mntns_owner(struct ns_common *ns)
4099{
4100 return to_mnt_ns(ns)->user_ns;
4101}
4102
Eric W. Biederman8823c072010-03-07 18:49:36 -08004103const struct proc_ns_operations mntns_operations = {
4104 .name = "mnt",
4105 .type = CLONE_NEWNS,
4106 .get = mntns_get,
4107 .put = mntns_put,
4108 .install = mntns_install,
Andrey Vaginbcac25a2016-09-06 00:47:13 -07004109 .owner = mntns_owner,
Eric W. Biederman8823c072010-03-07 18:49:36 -08004110};