move mount_capable() further out
Call graph of vfs_get_tree():
vfs_fsconfig_locked() # neither kernmount, nor submount
do_new_mount() # neither kernmount, nor submount
fc_mount()
afs_mntpt_do_automount() # submount
mount_one_hugetlbfs() # kernmount
pid_ns_prepare_proc() # kernmount
mq_create_mount() # kernmount
vfs_kern_mount()
simple_pin_fs() # kernmount
vfs_submount() # submount
kern_mount() # kernmount
init_mount_tree()
btrfs_mount()
nfs_do_root_mount()
The first two need the check (unconditionally).
init_mount_tree() is setting rootfs up; any capability
checks make zero sense for that one. And btrfs_mount()/
nfs_do_root_mount() have the checks already done in their
callers.
IOW, we can shift mount_capable() handling into
the two callers - one in the normal case of mount(2),
another - in fsconfig(2) handling of FSCONFIG_CMD_CREATE.
I.e. the syscalls that set a new filesystem up.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/fsopen.c b/fs/fsopen.c
index c2891e9..3901727 100644
--- a/fs/fsopen.c
+++ b/fs/fsopen.c
@@ -230,6 +230,8 @@ static int vfs_fsconfig_locked(struct fs_context *fc, int cmd,
case FSCONFIG_CMD_CREATE:
if (fc->phase != FS_CONTEXT_CREATE_PARAMS)
return -EBUSY;
+ if (!mount_capable(fc))
+ return -EPERM;
fc->phase = FS_CONTEXT_CREATING;
ret = vfs_get_tree(fc);
if (ret)
diff --git a/fs/namespace.c b/fs/namespace.c
index ffb13f0..1141641 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2786,6 +2786,8 @@ static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
err = vfs_parse_fs_string(fc, "source", name, strlen(name));
if (!err)
err = parse_monolithic_mount_data(fc, data);
+ if (!err && !mount_capable(fc))
+ err = -EPERM;
if (!err)
err = vfs_get_tree(fc);
if (!err)
diff --git a/fs/super.c b/fs/super.c
index 2c38541..72b4a5a 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -1415,12 +1415,6 @@ int vfs_get_tree(struct fs_context *fc)
if (fc->root)
return -EBUSY;
- if (!(fc->sb_flags & SB_KERNMOUNT) &&
- fc->purpose != FS_CONTEXT_FOR_SUBMOUNT) {
- if (!mount_capable(fc))
- return -EPERM;
- }
-
/* Get the mountable root in fc->root, with a ref on the root and a ref
* on the superblock.
*/