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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * The "user cache".
3 *
4 * (C) Copyright 1991-2000 Linus Torvalds
5 *
6 * We have a per-user structure to keep track of how many
7 * processes, files etc the user has claimed, in order to be
8 * able to have per-user limits for system resources.
9 */
10
11#include <linux/init.h>
12#include <linux/sched.h>
13#include <linux/slab.h>
14#include <linux/bitops.h>
15#include <linux/key.h>
Ingo Molnar8703e8a2017-02-08 18:51:30 +010016#include <linux/sched/user.h>
Ingo Molnar4021cb22006-01-25 15:23:07 +010017#include <linux/interrupt.h>
Paul Gortmaker9984de12011-05-23 14:51:41 -040018#include <linux/export.h>
Cedric Le Goateracce2922007-07-15 23:40:59 -070019#include <linux/user_namespace.h>
David Howells0bb80f22013-04-12 01:50:06 +010020#include <linux/proc_ns.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070021
Serge E. Hallyn59607db2011-03-23 16:43:16 -070022/*
23 * userns count is 1 for root user, 1 for init_uts_ns,
24 * and 1 for... ?
25 */
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080026struct user_namespace init_user_ns = {
Eric W. Biederman22d917d2011-11-17 00:11:58 -080027 .uid_map = {
28 .nr_extents = 1,
Christian Brauneraa4bf442017-10-25 00:04:40 +020029 {
30 .extent[0] = {
31 .first = 0,
32 .lower_first = 0,
33 .count = 4294967295U,
34 },
Eric W. Biederman22d917d2011-11-17 00:11:58 -080035 },
36 },
37 .gid_map = {
38 .nr_extents = 1,
Christian Brauneraa4bf442017-10-25 00:04:40 +020039 {
40 .extent[0] = {
41 .first = 0,
42 .lower_first = 0,
43 .count = 4294967295U,
44 },
Eric W. Biederman22d917d2011-11-17 00:11:58 -080045 },
46 },
Eric W. Biedermanf76d2072012-08-30 01:24:05 -070047 .projid_map = {
48 .nr_extents = 1,
Christian Brauneraa4bf442017-10-25 00:04:40 +020049 {
50 .extent[0] = {
51 .first = 0,
52 .lower_first = 0,
53 .count = 4294967295U,
54 },
Eric W. Biedermanf76d2072012-08-30 01:24:05 -070055 },
56 },
Eric W. Biedermanc61a2812012-12-28 18:58:39 -080057 .count = ATOMIC_INIT(3),
Eric W. Biederman783291e2011-11-17 01:32:59 -080058 .owner = GLOBAL_ROOT_UID,
59 .group = GLOBAL_ROOT_GID,
Al Viro435d5f42014-10-31 22:56:04 -040060 .ns.inum = PROC_USER_INIT_INO,
Al Viro33c42942014-11-01 02:32:53 -040061#ifdef CONFIG_USER_NS
62 .ns.ops = &userns_operations,
63#endif
Eric W. Biederman9cc46512014-12-02 12:27:26 -060064 .flags = USERNS_INIT_FLAGS,
David Howellsb206f282019-06-26 21:02:32 +010065#ifdef CONFIG_KEYS
66 .keyring_name_list = LIST_HEAD_INIT(init_user_ns.keyring_name_list),
67#endif
Xiao Guangrong6bd364d2013-12-13 15:00:32 +080068#ifdef CONFIG_PERSISTENT_KEYRINGS
69 .persistent_keyring_register_sem =
70 __RWSEM_INITIALIZER(init_user_ns.persistent_keyring_register_sem),
David Howellsf36f8c72013-09-24 10:35:19 +010071#endif
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -080072};
73EXPORT_SYMBOL_GPL(init_user_ns);
74
Linus Torvalds1da177e2005-04-16 15:20:36 -070075/*
76 * UID task count cache, to get fast user lookup in "alloc_uid"
77 * when changing user ID's (ie setuid() and friends).
78 */
79
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080080#define UIDHASH_BITS (CONFIG_BASE_SMALL ? 3 : 7)
81#define UIDHASH_SZ (1 << UIDHASH_BITS)
Linus Torvalds1da177e2005-04-16 15:20:36 -070082#define UIDHASH_MASK (UIDHASH_SZ - 1)
83#define __uidhashfn(uid) (((uid >> UIDHASH_BITS) + uid) & UIDHASH_MASK)
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080084#define uidhashentry(uid) (uidhash_table + __uidhashfn((__kuid_val(uid))))
Linus Torvalds1da177e2005-04-16 15:20:36 -070085
Christoph Lametere18b8902006-12-06 20:33:20 -080086static struct kmem_cache *uid_cachep;
Eric W. Biederman7b44ab92011-11-16 23:20:58 -080087struct hlist_head uidhash_table[UIDHASH_SZ];
Ingo Molnar4021cb22006-01-25 15:23:07 +010088
89/*
90 * The uidhash_lock is mostly taken from process context, but it is
91 * occasionally also taken from softirq/tasklet context, when
92 * task-structs get RCU-freed. Hence all locking must be softirq-safe.
Andrew Morton3fa97c92006-01-31 16:34:26 -080093 * But free_uid() is also called with local interrupts disabled, and running
94 * local_bh_enable() with local interrupts disabled is an error - we'll run
95 * softirq callbacks, and they can unconditionally enable interrupts, and
96 * the caller of free_uid() didn't expect that..
Ingo Molnar4021cb22006-01-25 15:23:07 +010097 */
Linus Torvalds1da177e2005-04-16 15:20:36 -070098static DEFINE_SPINLOCK(uidhash_lock);
99
Eric W. Biederman783291e2011-11-17 01:32:59 -0800100/* root_user.__count is 1, for init task cred */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101struct user_struct root_user = {
Sebastian Andrzej Siewiorfc371912018-08-21 21:55:38 -0700102 .__count = REFCOUNT_INIT(1),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 .processes = ATOMIC_INIT(1),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104 .sigpending = ATOMIC_INIT(0),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700105 .locked_shm = 0,
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800106 .uid = GLOBAL_ROOT_UID,
Luck, Tonybef3efb2018-02-22 09:15:06 -0800107 .ratelimit = RATELIMIT_STATE_INIT(root_user.ratelimit, 0, 0),
Linus Torvalds1da177e2005-04-16 15:20:36 -0700108};
109
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200110/*
111 * These routines must be called with the uidhash spinlock held!
112 */
Alexey Dobriyan40aeb402007-10-16 23:30:09 -0700113static void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200114{
115 hlist_add_head(&up->uidhash_node, hashent);
116}
117
Alexey Dobriyan40aeb402007-10-16 23:30:09 -0700118static void uid_hash_remove(struct user_struct *up)
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200119{
120 hlist_del_init(&up->uidhash_node);
121}
122
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800123static struct user_struct *uid_hash_find(kuid_t uid, struct hlist_head *hashent)
Kay Sievers39592142009-03-24 15:43:30 +0100124{
125 struct user_struct *user;
Kay Sievers39592142009-03-24 15:43:30 +0100126
Sasha Levinb67bfe02013-02-27 17:06:00 -0800127 hlist_for_each_entry(user, hashent, uidhash_node) {
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800128 if (uid_eq(user->uid, uid)) {
Sebastian Andrzej Siewiorfc371912018-08-21 21:55:38 -0700129 refcount_inc(&user->__count);
Kay Sievers39592142009-03-24 15:43:30 +0100130 return user;
131 }
132 }
133
134 return NULL;
135}
136
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200137/* IRQs are disabled and uidhash_lock is held upon function entry.
138 * IRQ state (as stored in flags) is restored and uidhash_lock released
139 * upon function exit.
140 */
Serge Hallyn18b6e042008-10-15 16:38:45 -0500141static void free_user(struct user_struct *up, unsigned long flags)
Namhyung Kim571428b2010-10-26 14:22:43 -0700142 __releases(&uidhash_lock)
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200143{
144 uid_hash_remove(up);
145 spin_unlock_irqrestore(&uidhash_lock, flags);
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200146 key_put(up->uid_keyring);
147 key_put(up->session_keyring);
148 kmem_cache_free(uid_cachep, up);
149}
Srivatsa Vaddagiri24e377a2007-10-15 17:00:09 +0200150
Linus Torvalds1da177e2005-04-16 15:20:36 -0700151/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152 * Locate the user_struct for the passed UID. If found, take a ref on it. The
153 * caller must undo that ref with free_uid().
154 *
155 * If the user_struct could not be found, return NULL.
156 */
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800157struct user_struct *find_user(kuid_t uid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158{
159 struct user_struct *ret;
Andrew Morton3fa97c92006-01-31 16:34:26 -0800160 unsigned long flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161
Andrew Morton3fa97c92006-01-31 16:34:26 -0800162 spin_lock_irqsave(&uidhash_lock, flags);
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800163 ret = uid_hash_find(uid, uidhashentry(uid));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800164 spin_unlock_irqrestore(&uidhash_lock, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700165 return ret;
166}
167
168void free_uid(struct user_struct *up)
169{
Andrew Morton3fa97c92006-01-31 16:34:26 -0800170 unsigned long flags;
171
Andrew Morton36f57412006-03-24 03:15:47 -0800172 if (!up)
173 return;
174
Anna-Maria Gleixnerce0a5682018-08-21 21:55:42 -0700175 if (refcount_dec_and_lock_irqsave(&up->__count, &uidhash_lock, &flags))
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200176 free_user(up, flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177}
178
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800179struct user_struct *alloc_uid(kuid_t uid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700180{
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800181 struct hlist_head *hashent = uidhashentry(uid);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100182 struct user_struct *up, *new;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183
Andrew Morton3fa97c92006-01-31 16:34:26 -0800184 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185 up = uid_hash_find(uid, hashent);
Andrew Morton3fa97c92006-01-31 16:34:26 -0800186 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700187
188 if (!up) {
Andrew Morton354a1f42008-04-30 00:54:54 -0700189 new = kmem_cache_zalloc(uid_cachep, GFP_KERNEL);
Pavel Emelyanov8eb703e2008-01-25 21:08:26 +0100190 if (!new)
Rasmus Villemoes6c4e1212019-05-14 15:42:37 -0700191 return NULL;
Pavel Emelyanov5e8869b2007-11-26 21:21:49 +0100192
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 new->uid = uid;
Sebastian Andrzej Siewiorfc371912018-08-21 21:55:38 -0700194 refcount_set(&new->__count, 1);
Luck, Tonybef3efb2018-02-22 09:15:06 -0800195 ratelimit_state_init(&new->ratelimit, HZ, 100);
196 ratelimit_set_flags(&new->ratelimit, RATELIMIT_MSG_ON_RELEASE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197
198 /*
199 * Before adding this, check whether we raced
200 * on adding the same user already..
201 */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800202 spin_lock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203 up = uid_hash_find(uid, hashent);
204 if (up) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205 kmem_cache_free(uid_cachep, new);
206 } else {
207 uid_hash_insert(new, hashent);
208 up = new;
209 }
Andrew Morton3fa97c92006-01-31 16:34:26 -0800210 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211 }
Dhaval Giani5cb350b2007-10-15 17:00:14 +0200212
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213 return up;
214}
215
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216static int __init uid_cache_init(void)
217{
218 int n;
219
220 uid_cachep = kmem_cache_create("uid_cache", sizeof(struct user_struct),
Paul Mundt20c2df82007-07-20 10:11:58 +0900221 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222
223 for(n = 0; n < UIDHASH_SZ; ++n)
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800224 INIT_HLIST_HEAD(uidhash_table + n);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225
226 /* Insert the root user immediately (init already runs as root) */
Andrew Morton3fa97c92006-01-31 16:34:26 -0800227 spin_lock_irq(&uidhash_lock);
Eric W. Biederman7b44ab92011-11-16 23:20:58 -0800228 uid_hash_insert(&root_user, uidhashentry(GLOBAL_ROOT_UID));
Andrew Morton3fa97c92006-01-31 16:34:26 -0800229 spin_unlock_irq(&uidhash_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700230
231 return 0;
232}
Paul Gortmakerc96d6662014-04-03 14:48:35 -0700233subsys_initcall(uid_cache_init);