1 // SPDX-License-Identifier: GPL-2.0-only
5 * (C) Copyright Al Viro 2000, 2001
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
11 #include <linux/syscalls.h>
12 #include <linux/export.h>
13 #include <linux/capability.h>
14 #include <linux/mnt_namespace.h>
15 #include <linux/user_namespace.h>
16 #include <linux/namei.h>
17 #include <linux/security.h>
18 #include <linux/cred.h>
19 #include <linux/idr.h>
20 #include <linux/init.h> /* init_rootfs */
21 #include <linux/fs_struct.h> /* get_fs_root et.al. */
22 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
23 #include <linux/file.h>
24 #include <linux/uaccess.h>
25 #include <linux/proc_ns.h>
26 #include <linux/magic.h>
27 #include <linux/memblock.h>
28 #include <linux/proc_fs.h>
29 #include <linux/task_work.h>
30 #include <linux/sched/task.h>
31 #include <uapi/linux/mount.h>
32 #include <linux/fs_context.h>
33 #include <linux/shmem_fs.h>
34 #include <linux/mnt_idmapping.h>
39 /* Maximum number of mounts in a mount namespace */
40 static unsigned int sysctl_mount_max __read_mostly
= 100000;
42 static unsigned int m_hash_mask __read_mostly
;
43 static unsigned int m_hash_shift __read_mostly
;
44 static unsigned int mp_hash_mask __read_mostly
;
45 static unsigned int mp_hash_shift __read_mostly
;
47 static __initdata
unsigned long mhash_entries
;
48 static int __init
set_mhash_entries(char *str
)
52 mhash_entries
= simple_strtoul(str
, &str
, 0);
55 __setup("mhash_entries=", set_mhash_entries
);
57 static __initdata
unsigned long mphash_entries
;
58 static int __init
set_mphash_entries(char *str
)
62 mphash_entries
= simple_strtoul(str
, &str
, 0);
65 __setup("mphash_entries=", set_mphash_entries
);
68 static DEFINE_IDA(mnt_id_ida
);
69 static DEFINE_IDA(mnt_group_ida
);
71 static struct hlist_head
*mount_hashtable __read_mostly
;
72 static struct hlist_head
*mountpoint_hashtable __read_mostly
;
73 static struct kmem_cache
*mnt_cache __read_mostly
;
74 static DECLARE_RWSEM(namespace_sem
);
75 static HLIST_HEAD(unmounted
); /* protected by namespace_sem */
76 static LIST_HEAD(ex_mountpoints
); /* protected by namespace_sem */
79 unsigned int attr_set
;
80 unsigned int attr_clr
;
81 unsigned int propagation
;
82 unsigned int lookup_flags
;
84 struct user_namespace
*mnt_userns
;
88 struct kobject
*fs_kobj
;
89 EXPORT_SYMBOL_GPL(fs_kobj
);
92 * vfsmount lock may be taken for read to prevent changes to the
93 * vfsmount hash, ie. during mountpoint lookups or walking back
96 * It should be taken for write in all cases where the vfsmount
97 * tree or hash is modified or when a vfsmount structure is modified.
99 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(mount_lock
);
101 static inline void lock_mount_hash(void)
103 write_seqlock(&mount_lock
);
106 static inline void unlock_mount_hash(void)
108 write_sequnlock(&mount_lock
);
111 static inline struct hlist_head
*m_hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
113 unsigned long tmp
= ((unsigned long)mnt
/ L1_CACHE_BYTES
);
114 tmp
+= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
115 tmp
= tmp
+ (tmp
>> m_hash_shift
);
116 return &mount_hashtable
[tmp
& m_hash_mask
];
119 static inline struct hlist_head
*mp_hash(struct dentry
*dentry
)
121 unsigned long tmp
= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
122 tmp
= tmp
+ (tmp
>> mp_hash_shift
);
123 return &mountpoint_hashtable
[tmp
& mp_hash_mask
];
126 static int mnt_alloc_id(struct mount
*mnt
)
128 int res
= ida_alloc(&mnt_id_ida
, GFP_KERNEL
);
136 static void mnt_free_id(struct mount
*mnt
)
138 ida_free(&mnt_id_ida
, mnt
->mnt_id
);
142 * Allocate a new peer group ID
144 static int mnt_alloc_group_id(struct mount
*mnt
)
146 int res
= ida_alloc_min(&mnt_group_ida
, 1, GFP_KERNEL
);
150 mnt
->mnt_group_id
= res
;
155 * Release a peer group ID
157 void mnt_release_group_id(struct mount
*mnt
)
159 ida_free(&mnt_group_ida
, mnt
->mnt_group_id
);
160 mnt
->mnt_group_id
= 0;
164 * vfsmount lock must be held for read
166 static inline void mnt_add_count(struct mount
*mnt
, int n
)
169 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, n
);
178 * vfsmount lock must be held for write
180 int mnt_get_count(struct mount
*mnt
)
186 for_each_possible_cpu(cpu
) {
187 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_count
;
192 return mnt
->mnt_count
;
196 static struct mount
*alloc_vfsmnt(const char *name
)
198 struct mount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
202 err
= mnt_alloc_id(mnt
);
207 mnt
->mnt_devname
= kstrdup_const(name
,
209 if (!mnt
->mnt_devname
)
214 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
216 goto out_free_devname
;
218 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
221 mnt
->mnt_writers
= 0;
224 INIT_HLIST_NODE(&mnt
->mnt_hash
);
225 INIT_LIST_HEAD(&mnt
->mnt_child
);
226 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
227 INIT_LIST_HEAD(&mnt
->mnt_list
);
228 INIT_LIST_HEAD(&mnt
->mnt_expire
);
229 INIT_LIST_HEAD(&mnt
->mnt_share
);
230 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
231 INIT_LIST_HEAD(&mnt
->mnt_slave
);
232 INIT_HLIST_NODE(&mnt
->mnt_mp_list
);
233 INIT_LIST_HEAD(&mnt
->mnt_umounting
);
234 INIT_HLIST_HEAD(&mnt
->mnt_stuck_children
);
235 mnt
->mnt
.mnt_userns
= &init_user_ns
;
241 kfree_const(mnt
->mnt_devname
);
246 kmem_cache_free(mnt_cache
, mnt
);
251 * Most r/o checks on a fs are for operations that take
252 * discrete amounts of time, like a write() or unlink().
253 * We must keep track of when those operations start
254 * (for permission checks) and when they end, so that
255 * we can determine when writes are able to occur to
259 * __mnt_is_readonly: check whether a mount is read-only
260 * @mnt: the mount to check for its write status
262 * This shouldn't be used directly ouside of the VFS.
263 * It does not guarantee that the filesystem will stay
264 * r/w, just that it is right *now*. This can not and
265 * should not be used in place of IS_RDONLY(inode).
266 * mnt_want/drop_write() will _keep_ the filesystem
269 bool __mnt_is_readonly(struct vfsmount
*mnt
)
271 return (mnt
->mnt_flags
& MNT_READONLY
) || sb_rdonly(mnt
->mnt_sb
);
273 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
275 static inline void mnt_inc_writers(struct mount
*mnt
)
278 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
284 static inline void mnt_dec_writers(struct mount
*mnt
)
287 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
293 static unsigned int mnt_get_writers(struct mount
*mnt
)
296 unsigned int count
= 0;
299 for_each_possible_cpu(cpu
) {
300 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_writers
;
305 return mnt
->mnt_writers
;
309 static int mnt_is_readonly(struct vfsmount
*mnt
)
311 if (mnt
->mnt_sb
->s_readonly_remount
)
313 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
315 return __mnt_is_readonly(mnt
);
319 * Most r/o & frozen checks on a fs are for operations that take discrete
320 * amounts of time, like a write() or unlink(). We must keep track of when
321 * those operations start (for permission checks) and when they end, so that we
322 * can determine when writes are able to occur to a filesystem.
325 * __mnt_want_write - get write access to a mount without freeze protection
326 * @m: the mount on which to take a write
328 * This tells the low-level filesystem that a write is about to be performed to
329 * it, and makes sure that writes are allowed (mnt it read-write) before
330 * returning success. This operation does not protect against filesystem being
331 * frozen. When the write operation is finished, __mnt_drop_write() must be
332 * called. This is effectively a refcount.
334 int __mnt_want_write(struct vfsmount
*m
)
336 struct mount
*mnt
= real_mount(m
);
340 mnt_inc_writers(mnt
);
342 * The store to mnt_inc_writers must be visible before we pass
343 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
344 * incremented count after it has set MNT_WRITE_HOLD.
347 might_lock(&mount_lock
.lock
);
348 while (READ_ONCE(mnt
->mnt
.mnt_flags
) & MNT_WRITE_HOLD
) {
349 if (!IS_ENABLED(CONFIG_PREEMPT_RT
)) {
353 * This prevents priority inversion, if the task
354 * setting MNT_WRITE_HOLD got preempted on a remote
355 * CPU, and it prevents life lock if the task setting
356 * MNT_WRITE_HOLD has a lower priority and is bound to
357 * the same CPU as the task that is spinning here.
366 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
367 * be set to match its requirements. So we must not load that until
368 * MNT_WRITE_HOLD is cleared.
371 if (mnt_is_readonly(m
)) {
372 mnt_dec_writers(mnt
);
381 * mnt_want_write - get write access to a mount
382 * @m: the mount on which to take a write
384 * This tells the low-level filesystem that a write is about to be performed to
385 * it, and makes sure that writes are allowed (mount is read-write, filesystem
386 * is not frozen) before returning success. When the write operation is
387 * finished, mnt_drop_write() must be called. This is effectively a refcount.
389 int mnt_want_write(struct vfsmount
*m
)
393 sb_start_write(m
->mnt_sb
);
394 ret
= __mnt_want_write(m
);
396 sb_end_write(m
->mnt_sb
);
399 EXPORT_SYMBOL_GPL(mnt_want_write
);
402 * __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
405 * This is like __mnt_want_write, but if the file is already open for writing it
406 * skips incrementing mnt_writers (since the open file already has a reference)
407 * and instead only does the check for emergency r/o remounts. This must be
408 * paired with __mnt_drop_write_file.
410 int __mnt_want_write_file(struct file
*file
)
412 if (file
->f_mode
& FMODE_WRITER
) {
414 * Superblock may have become readonly while there are still
415 * writable fd's, e.g. due to a fs error with errors=remount-ro
417 if (__mnt_is_readonly(file
->f_path
.mnt
))
421 return __mnt_want_write(file
->f_path
.mnt
);
425 * mnt_want_write_file - get write access to a file's mount
426 * @file: the file who's mount on which to take a write
428 * This is like mnt_want_write, but if the file is already open for writing it
429 * skips incrementing mnt_writers (since the open file already has a reference)
430 * and instead only does the freeze protection and the check for emergency r/o
431 * remounts. This must be paired with mnt_drop_write_file.
433 int mnt_want_write_file(struct file
*file
)
437 sb_start_write(file_inode(file
)->i_sb
);
438 ret
= __mnt_want_write_file(file
);
440 sb_end_write(file_inode(file
)->i_sb
);
443 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
446 * __mnt_drop_write - give up write access to a mount
447 * @mnt: the mount on which to give up write access
449 * Tells the low-level filesystem that we are done
450 * performing writes to it. Must be matched with
451 * __mnt_want_write() call above.
453 void __mnt_drop_write(struct vfsmount
*mnt
)
456 mnt_dec_writers(real_mount(mnt
));
461 * mnt_drop_write - give up write access to a mount
462 * @mnt: the mount on which to give up write access
464 * Tells the low-level filesystem that we are done performing writes to it and
465 * also allows filesystem to be frozen again. Must be matched with
466 * mnt_want_write() call above.
468 void mnt_drop_write(struct vfsmount
*mnt
)
470 __mnt_drop_write(mnt
);
471 sb_end_write(mnt
->mnt_sb
);
473 EXPORT_SYMBOL_GPL(mnt_drop_write
);
475 void __mnt_drop_write_file(struct file
*file
)
477 if (!(file
->f_mode
& FMODE_WRITER
))
478 __mnt_drop_write(file
->f_path
.mnt
);
481 void mnt_drop_write_file(struct file
*file
)
483 __mnt_drop_write_file(file
);
484 sb_end_write(file_inode(file
)->i_sb
);
486 EXPORT_SYMBOL(mnt_drop_write_file
);
489 * mnt_hold_writers - prevent write access to the given mount
490 * @mnt: mnt to prevent write access to
492 * Prevents write access to @mnt if there are no active writers for @mnt.
493 * This function needs to be called and return successfully before changing
494 * properties of @mnt that need to remain stable for callers with write access
497 * After this functions has been called successfully callers must pair it with
498 * a call to mnt_unhold_writers() in order to stop preventing write access to
501 * Context: This function expects lock_mount_hash() to be held serializing
502 * setting MNT_WRITE_HOLD.
503 * Return: On success 0 is returned.
504 * On error, -EBUSY is returned.
506 static inline int mnt_hold_writers(struct mount
*mnt
)
508 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
510 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
511 * should be visible before we do.
516 * With writers on hold, if this value is zero, then there are
517 * definitely no active writers (although held writers may subsequently
518 * increment the count, they'll have to wait, and decrement it after
519 * seeing MNT_READONLY).
521 * It is OK to have counter incremented on one CPU and decremented on
522 * another: the sum will add up correctly. The danger would be when we
523 * sum up each counter, if we read a counter before it is incremented,
524 * but then read another CPU's count which it has been subsequently
525 * decremented from -- we would see more decrements than we should.
526 * MNT_WRITE_HOLD protects against this scenario, because
527 * mnt_want_write first increments count, then smp_mb, then spins on
528 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
529 * we're counting up here.
531 if (mnt_get_writers(mnt
) > 0)
538 * mnt_unhold_writers - stop preventing write access to the given mount
539 * @mnt: mnt to stop preventing write access to
541 * Stop preventing write access to @mnt allowing callers to gain write access
544 * This function can only be called after a successful call to
545 * mnt_hold_writers().
547 * Context: This function expects lock_mount_hash() to be held.
549 static inline void mnt_unhold_writers(struct mount
*mnt
)
552 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
553 * that become unheld will see MNT_READONLY.
556 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
559 static int mnt_make_readonly(struct mount
*mnt
)
563 ret
= mnt_hold_writers(mnt
);
565 mnt
->mnt
.mnt_flags
|= MNT_READONLY
;
566 mnt_unhold_writers(mnt
);
570 int sb_prepare_remount_readonly(struct super_block
*sb
)
575 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
576 if (atomic_long_read(&sb
->s_remove_count
))
580 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
581 if (!(mnt
->mnt
.mnt_flags
& MNT_READONLY
)) {
582 err
= mnt_hold_writers(mnt
);
587 if (!err
&& atomic_long_read(&sb
->s_remove_count
))
591 sb
->s_readonly_remount
= 1;
594 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
595 if (mnt
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
596 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
603 static void free_vfsmnt(struct mount
*mnt
)
605 struct user_namespace
*mnt_userns
;
607 mnt_userns
= mnt_user_ns(&mnt
->mnt
);
608 if (!initial_idmapping(mnt_userns
))
609 put_user_ns(mnt_userns
);
610 kfree_const(mnt
->mnt_devname
);
612 free_percpu(mnt
->mnt_pcp
);
614 kmem_cache_free(mnt_cache
, mnt
);
617 static void delayed_free_vfsmnt(struct rcu_head
*head
)
619 free_vfsmnt(container_of(head
, struct mount
, mnt_rcu
));
622 /* call under rcu_read_lock */
623 int __legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
626 if (read_seqretry(&mount_lock
, seq
))
630 mnt
= real_mount(bastard
);
631 mnt_add_count(mnt
, 1);
632 smp_mb(); // see mntput_no_expire()
633 if (likely(!read_seqretry(&mount_lock
, seq
)))
635 if (bastard
->mnt_flags
& MNT_SYNC_UMOUNT
) {
636 mnt_add_count(mnt
, -1);
640 if (unlikely(bastard
->mnt_flags
& MNT_DOOMED
)) {
641 mnt_add_count(mnt
, -1);
646 /* caller will mntput() */
650 /* call under rcu_read_lock */
651 bool legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
653 int res
= __legitimize_mnt(bastard
, seq
);
656 if (unlikely(res
< 0)) {
665 * find the first mount at @dentry on vfsmount @mnt.
666 * call under rcu_read_lock()
668 struct mount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
670 struct hlist_head
*head
= m_hash(mnt
, dentry
);
673 hlist_for_each_entry_rcu(p
, head
, mnt_hash
)
674 if (&p
->mnt_parent
->mnt
== mnt
&& p
->mnt_mountpoint
== dentry
)
680 * lookup_mnt - Return the first child mount mounted at path
682 * "First" means first mounted chronologically. If you create the
685 * mount /dev/sda1 /mnt
686 * mount /dev/sda2 /mnt
687 * mount /dev/sda3 /mnt
689 * Then lookup_mnt() on the base /mnt dentry in the root mount will
690 * return successively the root dentry and vfsmount of /dev/sda1, then
691 * /dev/sda2, then /dev/sda3, then NULL.
693 * lookup_mnt takes a reference to the found vfsmount.
695 struct vfsmount
*lookup_mnt(const struct path
*path
)
697 struct mount
*child_mnt
;
703 seq
= read_seqbegin(&mount_lock
);
704 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
);
705 m
= child_mnt
? &child_mnt
->mnt
: NULL
;
706 } while (!legitimize_mnt(m
, seq
));
711 static inline void lock_ns_list(struct mnt_namespace
*ns
)
713 spin_lock(&ns
->ns_lock
);
716 static inline void unlock_ns_list(struct mnt_namespace
*ns
)
718 spin_unlock(&ns
->ns_lock
);
721 static inline bool mnt_is_cursor(struct mount
*mnt
)
723 return mnt
->mnt
.mnt_flags
& MNT_CURSOR
;
727 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
728 * current mount namespace.
730 * The common case is dentries are not mountpoints at all and that
731 * test is handled inline. For the slow case when we are actually
732 * dealing with a mountpoint of some kind, walk through all of the
733 * mounts in the current mount namespace and test to see if the dentry
736 * The mount_hashtable is not usable in the context because we
737 * need to identify all mounts that may be in the current mount
738 * namespace not just a mount that happens to have some specified
741 bool __is_local_mountpoint(struct dentry
*dentry
)
743 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
745 bool is_covered
= false;
747 down_read(&namespace_sem
);
749 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
750 if (mnt_is_cursor(mnt
))
752 is_covered
= (mnt
->mnt_mountpoint
== dentry
);
757 up_read(&namespace_sem
);
762 static struct mountpoint
*lookup_mountpoint(struct dentry
*dentry
)
764 struct hlist_head
*chain
= mp_hash(dentry
);
765 struct mountpoint
*mp
;
767 hlist_for_each_entry(mp
, chain
, m_hash
) {
768 if (mp
->m_dentry
== dentry
) {
776 static struct mountpoint
*get_mountpoint(struct dentry
*dentry
)
778 struct mountpoint
*mp
, *new = NULL
;
781 if (d_mountpoint(dentry
)) {
782 /* might be worth a WARN_ON() */
783 if (d_unlinked(dentry
))
784 return ERR_PTR(-ENOENT
);
786 read_seqlock_excl(&mount_lock
);
787 mp
= lookup_mountpoint(dentry
);
788 read_sequnlock_excl(&mount_lock
);
794 new = kmalloc(sizeof(struct mountpoint
), GFP_KERNEL
);
796 return ERR_PTR(-ENOMEM
);
799 /* Exactly one processes may set d_mounted */
800 ret
= d_set_mounted(dentry
);
802 /* Someone else set d_mounted? */
806 /* The dentry is not available as a mountpoint? */
811 /* Add the new mountpoint to the hash table */
812 read_seqlock_excl(&mount_lock
);
813 new->m_dentry
= dget(dentry
);
815 hlist_add_head(&new->m_hash
, mp_hash(dentry
));
816 INIT_HLIST_HEAD(&new->m_list
);
817 read_sequnlock_excl(&mount_lock
);
827 * vfsmount lock must be held. Additionally, the caller is responsible
828 * for serializing calls for given disposal list.
830 static void __put_mountpoint(struct mountpoint
*mp
, struct list_head
*list
)
832 if (!--mp
->m_count
) {
833 struct dentry
*dentry
= mp
->m_dentry
;
834 BUG_ON(!hlist_empty(&mp
->m_list
));
835 spin_lock(&dentry
->d_lock
);
836 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
837 spin_unlock(&dentry
->d_lock
);
838 dput_to_list(dentry
, list
);
839 hlist_del(&mp
->m_hash
);
844 /* called with namespace_lock and vfsmount lock */
845 static void put_mountpoint(struct mountpoint
*mp
)
847 __put_mountpoint(mp
, &ex_mountpoints
);
850 static inline int check_mnt(struct mount
*mnt
)
852 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
856 * vfsmount lock must be held for write
858 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
862 wake_up_interruptible(&ns
->poll
);
867 * vfsmount lock must be held for write
869 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
871 if (ns
&& ns
->event
!= event
) {
873 wake_up_interruptible(&ns
->poll
);
878 * vfsmount lock must be held for write
880 static struct mountpoint
*unhash_mnt(struct mount
*mnt
)
882 struct mountpoint
*mp
;
883 mnt
->mnt_parent
= mnt
;
884 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
885 list_del_init(&mnt
->mnt_child
);
886 hlist_del_init_rcu(&mnt
->mnt_hash
);
887 hlist_del_init(&mnt
->mnt_mp_list
);
894 * vfsmount lock must be held for write
896 static void umount_mnt(struct mount
*mnt
)
898 put_mountpoint(unhash_mnt(mnt
));
902 * vfsmount lock must be held for write
904 void mnt_set_mountpoint(struct mount
*mnt
,
905 struct mountpoint
*mp
,
906 struct mount
*child_mnt
)
909 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
910 child_mnt
->mnt_mountpoint
= mp
->m_dentry
;
911 child_mnt
->mnt_parent
= mnt
;
912 child_mnt
->mnt_mp
= mp
;
913 hlist_add_head(&child_mnt
->mnt_mp_list
, &mp
->m_list
);
916 static void __attach_mnt(struct mount
*mnt
, struct mount
*parent
)
918 hlist_add_head_rcu(&mnt
->mnt_hash
,
919 m_hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
920 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
924 * vfsmount lock must be held for write
926 static void attach_mnt(struct mount
*mnt
,
927 struct mount
*parent
,
928 struct mountpoint
*mp
)
930 mnt_set_mountpoint(parent
, mp
, mnt
);
931 __attach_mnt(mnt
, parent
);
934 void mnt_change_mountpoint(struct mount
*parent
, struct mountpoint
*mp
, struct mount
*mnt
)
936 struct mountpoint
*old_mp
= mnt
->mnt_mp
;
937 struct mount
*old_parent
= mnt
->mnt_parent
;
939 list_del_init(&mnt
->mnt_child
);
940 hlist_del_init(&mnt
->mnt_mp_list
);
941 hlist_del_init_rcu(&mnt
->mnt_hash
);
943 attach_mnt(mnt
, parent
, mp
);
945 put_mountpoint(old_mp
);
946 mnt_add_count(old_parent
, -1);
950 * vfsmount lock must be held for write
952 static void commit_tree(struct mount
*mnt
)
954 struct mount
*parent
= mnt
->mnt_parent
;
957 struct mnt_namespace
*n
= parent
->mnt_ns
;
959 BUG_ON(parent
== mnt
);
961 list_add_tail(&head
, &mnt
->mnt_list
);
962 list_for_each_entry(m
, &head
, mnt_list
)
965 list_splice(&head
, n
->list
.prev
);
967 n
->mounts
+= n
->pending_mounts
;
968 n
->pending_mounts
= 0;
970 __attach_mnt(mnt
, parent
);
971 touch_mnt_namespace(n
);
974 static struct mount
*next_mnt(struct mount
*p
, struct mount
*root
)
976 struct list_head
*next
= p
->mnt_mounts
.next
;
977 if (next
== &p
->mnt_mounts
) {
981 next
= p
->mnt_child
.next
;
982 if (next
!= &p
->mnt_parent
->mnt_mounts
)
987 return list_entry(next
, struct mount
, mnt_child
);
990 static struct mount
*skip_mnt_tree(struct mount
*p
)
992 struct list_head
*prev
= p
->mnt_mounts
.prev
;
993 while (prev
!= &p
->mnt_mounts
) {
994 p
= list_entry(prev
, struct mount
, mnt_child
);
995 prev
= p
->mnt_mounts
.prev
;
1001 * vfs_create_mount - Create a mount for a configured superblock
1002 * @fc: The configuration context with the superblock attached
1004 * Create a mount to an already configured superblock. If necessary, the
1005 * caller should invoke vfs_get_tree() before calling this.
1007 * Note that this does not attach the mount to anything.
1009 struct vfsmount
*vfs_create_mount(struct fs_context
*fc
)
1012 struct user_namespace
*fs_userns
;
1015 return ERR_PTR(-EINVAL
);
1017 mnt
= alloc_vfsmnt(fc
->source
?: "none");
1019 return ERR_PTR(-ENOMEM
);
1021 if (fc
->sb_flags
& SB_KERNMOUNT
)
1022 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
1024 atomic_inc(&fc
->root
->d_sb
->s_active
);
1025 mnt
->mnt
.mnt_sb
= fc
->root
->d_sb
;
1026 mnt
->mnt
.mnt_root
= dget(fc
->root
);
1027 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1028 mnt
->mnt_parent
= mnt
;
1030 fs_userns
= mnt
->mnt
.mnt_sb
->s_user_ns
;
1031 if (!initial_idmapping(fs_userns
))
1032 mnt
->mnt
.mnt_userns
= get_user_ns(fs_userns
);
1035 list_add_tail(&mnt
->mnt_instance
, &mnt
->mnt
.mnt_sb
->s_mounts
);
1036 unlock_mount_hash();
1039 EXPORT_SYMBOL(vfs_create_mount
);
1041 struct vfsmount
*fc_mount(struct fs_context
*fc
)
1043 int err
= vfs_get_tree(fc
);
1045 up_write(&fc
->root
->d_sb
->s_umount
);
1046 return vfs_create_mount(fc
);
1048 return ERR_PTR(err
);
1050 EXPORT_SYMBOL(fc_mount
);
1052 struct vfsmount
*vfs_kern_mount(struct file_system_type
*type
,
1053 int flags
, const char *name
,
1056 struct fs_context
*fc
;
1057 struct vfsmount
*mnt
;
1061 return ERR_PTR(-EINVAL
);
1063 fc
= fs_context_for_mount(type
, flags
);
1065 return ERR_CAST(fc
);
1068 ret
= vfs_parse_fs_string(fc
, "source",
1069 name
, strlen(name
));
1071 ret
= parse_monolithic_mount_data(fc
, data
);
1080 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
1083 vfs_submount(const struct dentry
*mountpoint
, struct file_system_type
*type
,
1084 const char *name
, void *data
)
1086 /* Until it is worked out how to pass the user namespace
1087 * through from the parent mount to the submount don't support
1088 * unprivileged mounts with submounts.
1090 if (mountpoint
->d_sb
->s_user_ns
!= &init_user_ns
)
1091 return ERR_PTR(-EPERM
);
1093 return vfs_kern_mount(type
, SB_SUBMOUNT
, name
, data
);
1095 EXPORT_SYMBOL_GPL(vfs_submount
);
1097 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
1100 struct super_block
*sb
= old
->mnt
.mnt_sb
;
1104 mnt
= alloc_vfsmnt(old
->mnt_devname
);
1106 return ERR_PTR(-ENOMEM
);
1108 if (flag
& (CL_SLAVE
| CL_PRIVATE
| CL_SHARED_TO_SLAVE
))
1109 mnt
->mnt_group_id
= 0; /* not a peer of original */
1111 mnt
->mnt_group_id
= old
->mnt_group_id
;
1113 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
1114 err
= mnt_alloc_group_id(mnt
);
1119 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
;
1120 mnt
->mnt
.mnt_flags
&= ~(MNT_WRITE_HOLD
|MNT_MARKED
|MNT_INTERNAL
);
1122 atomic_inc(&sb
->s_active
);
1123 mnt
->mnt
.mnt_userns
= mnt_user_ns(&old
->mnt
);
1124 if (!initial_idmapping(mnt
->mnt
.mnt_userns
))
1125 mnt
->mnt
.mnt_userns
= get_user_ns(mnt
->mnt
.mnt_userns
);
1126 mnt
->mnt
.mnt_sb
= sb
;
1127 mnt
->mnt
.mnt_root
= dget(root
);
1128 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1129 mnt
->mnt_parent
= mnt
;
1131 list_add_tail(&mnt
->mnt_instance
, &sb
->s_mounts
);
1132 unlock_mount_hash();
1134 if ((flag
& CL_SLAVE
) ||
1135 ((flag
& CL_SHARED_TO_SLAVE
) && IS_MNT_SHARED(old
))) {
1136 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
1137 mnt
->mnt_master
= old
;
1138 CLEAR_MNT_SHARED(mnt
);
1139 } else if (!(flag
& CL_PRIVATE
)) {
1140 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
1141 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
1142 if (IS_MNT_SLAVE(old
))
1143 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
1144 mnt
->mnt_master
= old
->mnt_master
;
1146 CLEAR_MNT_SHARED(mnt
);
1148 if (flag
& CL_MAKE_SHARED
)
1149 set_mnt_shared(mnt
);
1151 /* stick the duplicate mount on the same expiry list
1152 * as the original if that was on one */
1153 if (flag
& CL_EXPIRE
) {
1154 if (!list_empty(&old
->mnt_expire
))
1155 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
1163 return ERR_PTR(err
);
1166 static void cleanup_mnt(struct mount
*mnt
)
1168 struct hlist_node
*p
;
1171 * The warning here probably indicates that somebody messed
1172 * up a mnt_want/drop_write() pair. If this happens, the
1173 * filesystem was probably unable to make r/w->r/o transitions.
1174 * The locking used to deal with mnt_count decrement provides barriers,
1175 * so mnt_get_writers() below is safe.
1177 WARN_ON(mnt_get_writers(mnt
));
1178 if (unlikely(mnt
->mnt_pins
.first
))
1180 hlist_for_each_entry_safe(m
, p
, &mnt
->mnt_stuck_children
, mnt_umount
) {
1181 hlist_del(&m
->mnt_umount
);
1184 fsnotify_vfsmount_delete(&mnt
->mnt
);
1185 dput(mnt
->mnt
.mnt_root
);
1186 deactivate_super(mnt
->mnt
.mnt_sb
);
1188 call_rcu(&mnt
->mnt_rcu
, delayed_free_vfsmnt
);
1191 static void __cleanup_mnt(struct rcu_head
*head
)
1193 cleanup_mnt(container_of(head
, struct mount
, mnt_rcu
));
1196 static LLIST_HEAD(delayed_mntput_list
);
1197 static void delayed_mntput(struct work_struct
*unused
)
1199 struct llist_node
*node
= llist_del_all(&delayed_mntput_list
);
1200 struct mount
*m
, *t
;
1202 llist_for_each_entry_safe(m
, t
, node
, mnt_llist
)
1205 static DECLARE_DELAYED_WORK(delayed_mntput_work
, delayed_mntput
);
1207 static void mntput_no_expire(struct mount
*mnt
)
1213 if (likely(READ_ONCE(mnt
->mnt_ns
))) {
1215 * Since we don't do lock_mount_hash() here,
1216 * ->mnt_ns can change under us. However, if it's
1217 * non-NULL, then there's a reference that won't
1218 * be dropped until after an RCU delay done after
1219 * turning ->mnt_ns NULL. So if we observe it
1220 * non-NULL under rcu_read_lock(), the reference
1221 * we are dropping is not the final one.
1223 mnt_add_count(mnt
, -1);
1229 * make sure that if __legitimize_mnt() has not seen us grab
1230 * mount_lock, we'll see their refcount increment here.
1233 mnt_add_count(mnt
, -1);
1234 count
= mnt_get_count(mnt
);
1238 unlock_mount_hash();
1241 if (unlikely(mnt
->mnt
.mnt_flags
& MNT_DOOMED
)) {
1243 unlock_mount_hash();
1246 mnt
->mnt
.mnt_flags
|= MNT_DOOMED
;
1249 list_del(&mnt
->mnt_instance
);
1251 if (unlikely(!list_empty(&mnt
->mnt_mounts
))) {
1252 struct mount
*p
, *tmp
;
1253 list_for_each_entry_safe(p
, tmp
, &mnt
->mnt_mounts
, mnt_child
) {
1254 __put_mountpoint(unhash_mnt(p
), &list
);
1255 hlist_add_head(&p
->mnt_umount
, &mnt
->mnt_stuck_children
);
1258 unlock_mount_hash();
1259 shrink_dentry_list(&list
);
1261 if (likely(!(mnt
->mnt
.mnt_flags
& MNT_INTERNAL
))) {
1262 struct task_struct
*task
= current
;
1263 if (likely(!(task
->flags
& PF_KTHREAD
))) {
1264 init_task_work(&mnt
->mnt_rcu
, __cleanup_mnt
);
1265 if (!task_work_add(task
, &mnt
->mnt_rcu
, TWA_RESUME
))
1268 if (llist_add(&mnt
->mnt_llist
, &delayed_mntput_list
))
1269 schedule_delayed_work(&delayed_mntput_work
, 1);
1275 void mntput(struct vfsmount
*mnt
)
1278 struct mount
*m
= real_mount(mnt
);
1279 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1280 if (unlikely(m
->mnt_expiry_mark
))
1281 m
->mnt_expiry_mark
= 0;
1282 mntput_no_expire(m
);
1285 EXPORT_SYMBOL(mntput
);
1287 struct vfsmount
*mntget(struct vfsmount
*mnt
)
1290 mnt_add_count(real_mount(mnt
), 1);
1293 EXPORT_SYMBOL(mntget
);
1296 * path_is_mountpoint() - Check if path is a mount in the current namespace.
1297 * @path: path to check
1299 * d_mountpoint() can only be used reliably to establish if a dentry is
1300 * not mounted in any namespace and that common case is handled inline.
1301 * d_mountpoint() isn't aware of the possibility there may be multiple
1302 * mounts using a given dentry in a different namespace. This function
1303 * checks if the passed in path is a mountpoint rather than the dentry
1306 bool path_is_mountpoint(const struct path
*path
)
1311 if (!d_mountpoint(path
->dentry
))
1316 seq
= read_seqbegin(&mount_lock
);
1317 res
= __path_is_mountpoint(path
);
1318 } while (read_seqretry(&mount_lock
, seq
));
1323 EXPORT_SYMBOL(path_is_mountpoint
);
1325 struct vfsmount
*mnt_clone_internal(const struct path
*path
)
1328 p
= clone_mnt(real_mount(path
->mnt
), path
->dentry
, CL_PRIVATE
);
1331 p
->mnt
.mnt_flags
|= MNT_INTERNAL
;
1335 #ifdef CONFIG_PROC_FS
1336 static struct mount
*mnt_list_next(struct mnt_namespace
*ns
,
1337 struct list_head
*p
)
1339 struct mount
*mnt
, *ret
= NULL
;
1342 list_for_each_continue(p
, &ns
->list
) {
1343 mnt
= list_entry(p
, typeof(*mnt
), mnt_list
);
1344 if (!mnt_is_cursor(mnt
)) {
1354 /* iterator; we want it to have access to namespace_sem, thus here... */
1355 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
1357 struct proc_mounts
*p
= m
->private;
1358 struct list_head
*prev
;
1360 down_read(&namespace_sem
);
1362 prev
= &p
->ns
->list
;
1364 prev
= &p
->cursor
.mnt_list
;
1366 /* Read after we'd reached the end? */
1367 if (list_empty(prev
))
1371 return mnt_list_next(p
->ns
, prev
);
1374 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
1376 struct proc_mounts
*p
= m
->private;
1377 struct mount
*mnt
= v
;
1380 return mnt_list_next(p
->ns
, &mnt
->mnt_list
);
1383 static void m_stop(struct seq_file
*m
, void *v
)
1385 struct proc_mounts
*p
= m
->private;
1386 struct mount
*mnt
= v
;
1388 lock_ns_list(p
->ns
);
1390 list_move_tail(&p
->cursor
.mnt_list
, &mnt
->mnt_list
);
1392 list_del_init(&p
->cursor
.mnt_list
);
1393 unlock_ns_list(p
->ns
);
1394 up_read(&namespace_sem
);
1397 static int m_show(struct seq_file
*m
, void *v
)
1399 struct proc_mounts
*p
= m
->private;
1400 struct mount
*r
= v
;
1401 return p
->show(m
, &r
->mnt
);
1404 const struct seq_operations mounts_op
= {
1411 void mnt_cursor_del(struct mnt_namespace
*ns
, struct mount
*cursor
)
1413 down_read(&namespace_sem
);
1415 list_del(&cursor
->mnt_list
);
1417 up_read(&namespace_sem
);
1419 #endif /* CONFIG_PROC_FS */
1422 * may_umount_tree - check if a mount tree is busy
1423 * @m: root of mount tree
1425 * This is called to check if a tree of mounts has any
1426 * open files, pwds, chroots or sub mounts that are
1429 int may_umount_tree(struct vfsmount
*m
)
1431 struct mount
*mnt
= real_mount(m
);
1432 int actual_refs
= 0;
1433 int minimum_refs
= 0;
1437 /* write lock needed for mnt_get_count */
1439 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1440 actual_refs
+= mnt_get_count(p
);
1443 unlock_mount_hash();
1445 if (actual_refs
> minimum_refs
)
1451 EXPORT_SYMBOL(may_umount_tree
);
1454 * may_umount - check if a mount point is busy
1455 * @mnt: root of mount
1457 * This is called to check if a mount point has any
1458 * open files, pwds, chroots or sub mounts. If the
1459 * mount has sub mounts this will return busy
1460 * regardless of whether the sub mounts are busy.
1462 * Doesn't take quota and stuff into account. IOW, in some cases it will
1463 * give false negatives. The main reason why it's here is that we need
1464 * a non-destructive way to look for easily umountable filesystems.
1466 int may_umount(struct vfsmount
*mnt
)
1469 down_read(&namespace_sem
);
1471 if (propagate_mount_busy(real_mount(mnt
), 2))
1473 unlock_mount_hash();
1474 up_read(&namespace_sem
);
1478 EXPORT_SYMBOL(may_umount
);
1480 static void namespace_unlock(void)
1482 struct hlist_head head
;
1483 struct hlist_node
*p
;
1487 hlist_move_list(&unmounted
, &head
);
1488 list_splice_init(&ex_mountpoints
, &list
);
1490 up_write(&namespace_sem
);
1492 shrink_dentry_list(&list
);
1494 if (likely(hlist_empty(&head
)))
1497 synchronize_rcu_expedited();
1499 hlist_for_each_entry_safe(m
, p
, &head
, mnt_umount
) {
1500 hlist_del(&m
->mnt_umount
);
1505 static inline void namespace_lock(void)
1507 down_write(&namespace_sem
);
1510 enum umount_tree_flags
{
1512 UMOUNT_PROPAGATE
= 2,
1513 UMOUNT_CONNECTED
= 4,
1516 static bool disconnect_mount(struct mount
*mnt
, enum umount_tree_flags how
)
1518 /* Leaving mounts connected is only valid for lazy umounts */
1519 if (how
& UMOUNT_SYNC
)
1522 /* A mount without a parent has nothing to be connected to */
1523 if (!mnt_has_parent(mnt
))
1526 /* Because the reference counting rules change when mounts are
1527 * unmounted and connected, umounted mounts may not be
1528 * connected to mounted mounts.
1530 if (!(mnt
->mnt_parent
->mnt
.mnt_flags
& MNT_UMOUNT
))
1533 /* Has it been requested that the mount remain connected? */
1534 if (how
& UMOUNT_CONNECTED
)
1537 /* Is the mount locked such that it needs to remain connected? */
1538 if (IS_MNT_LOCKED(mnt
))
1541 /* By default disconnect the mount */
1546 * mount_lock must be held
1547 * namespace_sem must be held for write
1549 static void umount_tree(struct mount
*mnt
, enum umount_tree_flags how
)
1551 LIST_HEAD(tmp_list
);
1554 if (how
& UMOUNT_PROPAGATE
)
1555 propagate_mount_unlock(mnt
);
1557 /* Gather the mounts to umount */
1558 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1559 p
->mnt
.mnt_flags
|= MNT_UMOUNT
;
1560 list_move(&p
->mnt_list
, &tmp_list
);
1563 /* Hide the mounts from mnt_mounts */
1564 list_for_each_entry(p
, &tmp_list
, mnt_list
) {
1565 list_del_init(&p
->mnt_child
);
1568 /* Add propogated mounts to the tmp_list */
1569 if (how
& UMOUNT_PROPAGATE
)
1570 propagate_umount(&tmp_list
);
1572 while (!list_empty(&tmp_list
)) {
1573 struct mnt_namespace
*ns
;
1575 p
= list_first_entry(&tmp_list
, struct mount
, mnt_list
);
1576 list_del_init(&p
->mnt_expire
);
1577 list_del_init(&p
->mnt_list
);
1581 __touch_mnt_namespace(ns
);
1584 if (how
& UMOUNT_SYNC
)
1585 p
->mnt
.mnt_flags
|= MNT_SYNC_UMOUNT
;
1587 disconnect
= disconnect_mount(p
, how
);
1588 if (mnt_has_parent(p
)) {
1589 mnt_add_count(p
->mnt_parent
, -1);
1591 /* Don't forget about p */
1592 list_add_tail(&p
->mnt_child
, &p
->mnt_parent
->mnt_mounts
);
1597 change_mnt_propagation(p
, MS_PRIVATE
);
1599 hlist_add_head(&p
->mnt_umount
, &unmounted
);
1603 static void shrink_submounts(struct mount
*mnt
);
1605 static int do_umount_root(struct super_block
*sb
)
1609 down_write(&sb
->s_umount
);
1610 if (!sb_rdonly(sb
)) {
1611 struct fs_context
*fc
;
1613 fc
= fs_context_for_reconfigure(sb
->s_root
, SB_RDONLY
,
1618 ret
= parse_monolithic_mount_data(fc
, NULL
);
1620 ret
= reconfigure_super(fc
);
1624 up_write(&sb
->s_umount
);
1628 static int do_umount(struct mount
*mnt
, int flags
)
1630 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1633 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1638 * Allow userspace to request a mountpoint be expired rather than
1639 * unmounting unconditionally. Unmount only happens if:
1640 * (1) the mark is already set (the mark is cleared by mntput())
1641 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1643 if (flags
& MNT_EXPIRE
) {
1644 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1645 flags
& (MNT_FORCE
| MNT_DETACH
))
1649 * probably don't strictly need the lock here if we examined
1650 * all race cases, but it's a slowpath.
1653 if (mnt_get_count(mnt
) != 2) {
1654 unlock_mount_hash();
1657 unlock_mount_hash();
1659 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1664 * If we may have to abort operations to get out of this
1665 * mount, and they will themselves hold resources we must
1666 * allow the fs to do things. In the Unix tradition of
1667 * 'Gee thats tricky lets do it in userspace' the umount_begin
1668 * might fail to complete on the first run through as other tasks
1669 * must return, and the like. Thats for the mount program to worry
1670 * about for the moment.
1673 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1674 sb
->s_op
->umount_begin(sb
);
1678 * No sense to grab the lock for this test, but test itself looks
1679 * somewhat bogus. Suggestions for better replacement?
1680 * Ho-hum... In principle, we might treat that as umount + switch
1681 * to rootfs. GC would eventually take care of the old vfsmount.
1682 * Actually it makes sense, especially if rootfs would contain a
1683 * /reboot - static binary that would close all descriptors and
1684 * call reboot(9). Then init(8) could umount root and exec /reboot.
1686 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1688 * Special case for "unmounting" root ...
1689 * we just try to remount it readonly.
1691 if (!ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
))
1693 return do_umount_root(sb
);
1699 /* Recheck MNT_LOCKED with the locks held */
1701 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
1705 if (flags
& MNT_DETACH
) {
1706 if (!list_empty(&mnt
->mnt_list
))
1707 umount_tree(mnt
, UMOUNT_PROPAGATE
);
1710 shrink_submounts(mnt
);
1712 if (!propagate_mount_busy(mnt
, 2)) {
1713 if (!list_empty(&mnt
->mnt_list
))
1714 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
1719 unlock_mount_hash();
1725 * __detach_mounts - lazily unmount all mounts on the specified dentry
1727 * During unlink, rmdir, and d_drop it is possible to loose the path
1728 * to an existing mountpoint, and wind up leaking the mount.
1729 * detach_mounts allows lazily unmounting those mounts instead of
1732 * The caller may hold dentry->d_inode->i_mutex.
1734 void __detach_mounts(struct dentry
*dentry
)
1736 struct mountpoint
*mp
;
1741 mp
= lookup_mountpoint(dentry
);
1746 while (!hlist_empty(&mp
->m_list
)) {
1747 mnt
= hlist_entry(mp
->m_list
.first
, struct mount
, mnt_mp_list
);
1748 if (mnt
->mnt
.mnt_flags
& MNT_UMOUNT
) {
1750 hlist_add_head(&mnt
->mnt_umount
, &unmounted
);
1752 else umount_tree(mnt
, UMOUNT_CONNECTED
);
1756 unlock_mount_hash();
1761 * Is the caller allowed to modify his namespace?
1763 bool may_mount(void)
1765 return ns_capable(current
->nsproxy
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
);
1768 static void warn_mandlock(void)
1770 pr_warn_once("=======================================================\n"
1771 "WARNING: The mand mount option has been deprecated and\n"
1772 " and is ignored by this kernel. Remove the mand\n"
1773 " option from the mount to silence this warning.\n"
1774 "=======================================================\n");
1777 static int can_umount(const struct path
*path
, int flags
)
1779 struct mount
*mnt
= real_mount(path
->mnt
);
1783 if (path
->dentry
!= path
->mnt
->mnt_root
)
1785 if (!check_mnt(mnt
))
1787 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
) /* Check optimistically */
1789 if (flags
& MNT_FORCE
&& !capable(CAP_SYS_ADMIN
))
1794 // caller is responsible for flags being sane
1795 int path_umount(struct path
*path
, int flags
)
1797 struct mount
*mnt
= real_mount(path
->mnt
);
1800 ret
= can_umount(path
, flags
);
1802 ret
= do_umount(mnt
, flags
);
1804 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1806 mntput_no_expire(mnt
);
1810 static int ksys_umount(char __user
*name
, int flags
)
1812 int lookup_flags
= LOOKUP_MOUNTPOINT
;
1816 // basic validity checks done first
1817 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1820 if (!(flags
& UMOUNT_NOFOLLOW
))
1821 lookup_flags
|= LOOKUP_FOLLOW
;
1822 ret
= user_path_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1825 return path_umount(&path
, flags
);
1828 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1830 return ksys_umount(name
, flags
);
1833 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1836 * The 2.0 compatible umount. No flags.
1838 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1840 return ksys_umount(name
, 0);
1845 static bool is_mnt_ns_file(struct dentry
*dentry
)
1847 /* Is this a proxy for a mount namespace? */
1848 return dentry
->d_op
== &ns_dentry_operations
&&
1849 dentry
->d_fsdata
== &mntns_operations
;
1852 static struct mnt_namespace
*to_mnt_ns(struct ns_common
*ns
)
1854 return container_of(ns
, struct mnt_namespace
, ns
);
1857 struct ns_common
*from_mnt_ns(struct mnt_namespace
*mnt
)
1862 static bool mnt_ns_loop(struct dentry
*dentry
)
1864 /* Could bind mounting the mount namespace inode cause a
1865 * mount namespace loop?
1867 struct mnt_namespace
*mnt_ns
;
1868 if (!is_mnt_ns_file(dentry
))
1871 mnt_ns
= to_mnt_ns(get_proc_ns(dentry
->d_inode
));
1872 return current
->nsproxy
->mnt_ns
->seq
>= mnt_ns
->seq
;
1875 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1878 struct mount
*res
, *p
, *q
, *r
, *parent
;
1880 if (!(flag
& CL_COPY_UNBINDABLE
) && IS_MNT_UNBINDABLE(mnt
))
1881 return ERR_PTR(-EINVAL
);
1883 if (!(flag
& CL_COPY_MNT_NS_FILE
) && is_mnt_ns_file(dentry
))
1884 return ERR_PTR(-EINVAL
);
1886 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1890 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1893 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1895 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1898 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1899 if (!(flag
& CL_COPY_UNBINDABLE
) &&
1900 IS_MNT_UNBINDABLE(s
)) {
1901 if (s
->mnt
.mnt_flags
& MNT_LOCKED
) {
1902 /* Both unbindable and locked. */
1903 q
= ERR_PTR(-EPERM
);
1906 s
= skip_mnt_tree(s
);
1910 if (!(flag
& CL_COPY_MNT_NS_FILE
) &&
1911 is_mnt_ns_file(s
->mnt
.mnt_root
)) {
1912 s
= skip_mnt_tree(s
);
1915 while (p
!= s
->mnt_parent
) {
1921 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
1925 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1926 attach_mnt(q
, parent
, p
->mnt_mp
);
1927 unlock_mount_hash();
1934 umount_tree(res
, UMOUNT_SYNC
);
1935 unlock_mount_hash();
1940 /* Caller should check returned pointer for errors */
1942 struct vfsmount
*collect_mounts(const struct path
*path
)
1946 if (!check_mnt(real_mount(path
->mnt
)))
1947 tree
= ERR_PTR(-EINVAL
);
1949 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
1950 CL_COPY_ALL
| CL_PRIVATE
);
1953 return ERR_CAST(tree
);
1957 static void free_mnt_ns(struct mnt_namespace
*);
1958 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*, bool);
1960 void dissolve_on_fput(struct vfsmount
*mnt
)
1962 struct mnt_namespace
*ns
;
1965 ns
= real_mount(mnt
)->mnt_ns
;
1968 umount_tree(real_mount(mnt
), UMOUNT_CONNECTED
);
1972 unlock_mount_hash();
1978 void drop_collected_mounts(struct vfsmount
*mnt
)
1982 umount_tree(real_mount(mnt
), 0);
1983 unlock_mount_hash();
1987 static bool has_locked_children(struct mount
*mnt
, struct dentry
*dentry
)
1989 struct mount
*child
;
1991 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
1992 if (!is_subdir(child
->mnt_mountpoint
, dentry
))
1995 if (child
->mnt
.mnt_flags
& MNT_LOCKED
)
2002 * clone_private_mount - create a private clone of a path
2003 * @path: path to clone
2005 * This creates a new vfsmount, which will be the clone of @path. The new mount
2006 * will not be attached anywhere in the namespace and will be private (i.e.
2007 * changes to the originating mount won't be propagated into this).
2009 * Release with mntput().
2011 struct vfsmount
*clone_private_mount(const struct path
*path
)
2013 struct mount
*old_mnt
= real_mount(path
->mnt
);
2014 struct mount
*new_mnt
;
2016 down_read(&namespace_sem
);
2017 if (IS_MNT_UNBINDABLE(old_mnt
))
2020 if (!check_mnt(old_mnt
))
2023 if (has_locked_children(old_mnt
, path
->dentry
))
2026 new_mnt
= clone_mnt(old_mnt
, path
->dentry
, CL_PRIVATE
);
2027 up_read(&namespace_sem
);
2029 if (IS_ERR(new_mnt
))
2030 return ERR_CAST(new_mnt
);
2032 /* Longterm mount to be removed by kern_unmount*() */
2033 new_mnt
->mnt_ns
= MNT_NS_INTERNAL
;
2035 return &new_mnt
->mnt
;
2038 up_read(&namespace_sem
);
2039 return ERR_PTR(-EINVAL
);
2041 EXPORT_SYMBOL_GPL(clone_private_mount
);
2043 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
2044 struct vfsmount
*root
)
2047 int res
= f(root
, arg
);
2050 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
2051 res
= f(&mnt
->mnt
, arg
);
2058 static void lock_mnt_tree(struct mount
*mnt
)
2062 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2063 int flags
= p
->mnt
.mnt_flags
;
2064 /* Don't allow unprivileged users to change mount flags */
2065 flags
|= MNT_LOCK_ATIME
;
2067 if (flags
& MNT_READONLY
)
2068 flags
|= MNT_LOCK_READONLY
;
2070 if (flags
& MNT_NODEV
)
2071 flags
|= MNT_LOCK_NODEV
;
2073 if (flags
& MNT_NOSUID
)
2074 flags
|= MNT_LOCK_NOSUID
;
2076 if (flags
& MNT_NOEXEC
)
2077 flags
|= MNT_LOCK_NOEXEC
;
2078 /* Don't allow unprivileged users to reveal what is under a mount */
2079 if (list_empty(&p
->mnt_expire
))
2080 flags
|= MNT_LOCKED
;
2081 p
->mnt
.mnt_flags
= flags
;
2085 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
2089 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
2090 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
2091 mnt_release_group_id(p
);
2095 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
2099 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
2100 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
2101 int err
= mnt_alloc_group_id(p
);
2103 cleanup_group_ids(mnt
, p
);
2112 int count_mounts(struct mnt_namespace
*ns
, struct mount
*mnt
)
2114 unsigned int max
= READ_ONCE(sysctl_mount_max
);
2115 unsigned int mounts
= 0;
2118 if (ns
->mounts
>= max
)
2121 if (ns
->pending_mounts
>= max
)
2123 max
-= ns
->pending_mounts
;
2125 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
2131 ns
->pending_mounts
+= mounts
;
2136 * @source_mnt : mount tree to be attached
2137 * @nd : place the mount tree @source_mnt is attached
2138 * @parent_nd : if non-null, detach the source_mnt from its parent and
2139 * store the parent mount and mountpoint dentry.
2140 * (done when source_mnt is moved)
2142 * NOTE: in the table below explains the semantics when a source mount
2143 * of a given type is attached to a destination mount of a given type.
2144 * ---------------------------------------------------------------------------
2145 * | BIND MOUNT OPERATION |
2146 * |**************************************************************************
2147 * | source-->| shared | private | slave | unbindable |
2151 * |**************************************************************************
2152 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
2154 * |non-shared| shared (+) | private | slave (*) | invalid |
2155 * ***************************************************************************
2156 * A bind operation clones the source mount and mounts the clone on the
2157 * destination mount.
2159 * (++) the cloned mount is propagated to all the mounts in the propagation
2160 * tree of the destination mount and the cloned mount is added to
2161 * the peer group of the source mount.
2162 * (+) the cloned mount is created under the destination mount and is marked
2163 * as shared. The cloned mount is added to the peer group of the source
2165 * (+++) the mount is propagated to all the mounts in the propagation tree
2166 * of the destination mount and the cloned mount is made slave
2167 * of the same master as that of the source mount. The cloned mount
2168 * is marked as 'shared and slave'.
2169 * (*) the cloned mount is made a slave of the same master as that of the
2172 * ---------------------------------------------------------------------------
2173 * | MOVE MOUNT OPERATION |
2174 * |**************************************************************************
2175 * | source-->| shared | private | slave | unbindable |
2179 * |**************************************************************************
2180 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2182 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2183 * ***************************************************************************
2185 * (+) the mount is moved to the destination. And is then propagated to
2186 * all the mounts in the propagation tree of the destination mount.
2187 * (+*) the mount is moved to the destination.
2188 * (+++) the mount is moved to the destination and is then propagated to
2189 * all the mounts belonging to the destination mount's propagation tree.
2190 * the mount is marked as 'shared and slave'.
2191 * (*) the mount continues to be a slave at the new location.
2193 * if the source mount is a tree, the operations explained above is
2194 * applied to each mount in the tree.
2195 * Must be called without spinlocks held, since this function can sleep
2198 static int attach_recursive_mnt(struct mount
*source_mnt
,
2199 struct mount
*dest_mnt
,
2200 struct mountpoint
*dest_mp
,
2203 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2204 HLIST_HEAD(tree_list
);
2205 struct mnt_namespace
*ns
= dest_mnt
->mnt_ns
;
2206 struct mountpoint
*smp
;
2207 struct mount
*child
, *p
;
2208 struct hlist_node
*n
;
2211 /* Preallocate a mountpoint in case the new mounts need
2212 * to be tucked under other mounts.
2214 smp
= get_mountpoint(source_mnt
->mnt
.mnt_root
);
2216 return PTR_ERR(smp
);
2218 /* Is there space to add these mounts to the mount namespace? */
2220 err
= count_mounts(ns
, source_mnt
);
2225 if (IS_MNT_SHARED(dest_mnt
)) {
2226 err
= invent_group_ids(source_mnt
, true);
2229 err
= propagate_mnt(dest_mnt
, dest_mp
, source_mnt
, &tree_list
);
2232 goto out_cleanup_ids
;
2233 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
2239 unhash_mnt(source_mnt
);
2240 attach_mnt(source_mnt
, dest_mnt
, dest_mp
);
2241 touch_mnt_namespace(source_mnt
->mnt_ns
);
2243 if (source_mnt
->mnt_ns
) {
2244 /* move from anon - the caller will destroy */
2245 list_del_init(&source_mnt
->mnt_ns
->list
);
2247 mnt_set_mountpoint(dest_mnt
, dest_mp
, source_mnt
);
2248 commit_tree(source_mnt
);
2251 hlist_for_each_entry_safe(child
, n
, &tree_list
, mnt_hash
) {
2253 hlist_del_init(&child
->mnt_hash
);
2254 q
= __lookup_mnt(&child
->mnt_parent
->mnt
,
2255 child
->mnt_mountpoint
);
2257 mnt_change_mountpoint(child
, smp
, q
);
2258 /* Notice when we are propagating across user namespaces */
2259 if (child
->mnt_parent
->mnt_ns
->user_ns
!= user_ns
)
2260 lock_mnt_tree(child
);
2261 child
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2264 put_mountpoint(smp
);
2265 unlock_mount_hash();
2270 while (!hlist_empty(&tree_list
)) {
2271 child
= hlist_entry(tree_list
.first
, struct mount
, mnt_hash
);
2272 child
->mnt_parent
->mnt_ns
->pending_mounts
= 0;
2273 umount_tree(child
, UMOUNT_SYNC
);
2275 unlock_mount_hash();
2276 cleanup_group_ids(source_mnt
, NULL
);
2278 ns
->pending_mounts
= 0;
2280 read_seqlock_excl(&mount_lock
);
2281 put_mountpoint(smp
);
2282 read_sequnlock_excl(&mount_lock
);
2287 static struct mountpoint
*lock_mount(struct path
*path
)
2289 struct vfsmount
*mnt
;
2290 struct dentry
*dentry
= path
->dentry
;
2292 inode_lock(dentry
->d_inode
);
2293 if (unlikely(cant_mount(dentry
))) {
2294 inode_unlock(dentry
->d_inode
);
2295 return ERR_PTR(-ENOENT
);
2298 mnt
= lookup_mnt(path
);
2300 struct mountpoint
*mp
= get_mountpoint(dentry
);
2303 inode_unlock(dentry
->d_inode
);
2309 inode_unlock(path
->dentry
->d_inode
);
2312 dentry
= path
->dentry
= dget(mnt
->mnt_root
);
2316 static void unlock_mount(struct mountpoint
*where
)
2318 struct dentry
*dentry
= where
->m_dentry
;
2320 read_seqlock_excl(&mount_lock
);
2321 put_mountpoint(where
);
2322 read_sequnlock_excl(&mount_lock
);
2325 inode_unlock(dentry
->d_inode
);
2328 static int graft_tree(struct mount
*mnt
, struct mount
*p
, struct mountpoint
*mp
)
2330 if (mnt
->mnt
.mnt_sb
->s_flags
& SB_NOUSER
)
2333 if (d_is_dir(mp
->m_dentry
) !=
2334 d_is_dir(mnt
->mnt
.mnt_root
))
2337 return attach_recursive_mnt(mnt
, p
, mp
, false);
2341 * Sanity check the flags to change_mnt_propagation.
2344 static int flags_to_propagation_type(int ms_flags
)
2346 int type
= ms_flags
& ~(MS_REC
| MS_SILENT
);
2348 /* Fail if any non-propagation flags are set */
2349 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2351 /* Only one propagation flag should be set */
2352 if (!is_power_of_2(type
))
2358 * recursively change the type of the mountpoint.
2360 static int do_change_type(struct path
*path
, int ms_flags
)
2363 struct mount
*mnt
= real_mount(path
->mnt
);
2364 int recurse
= ms_flags
& MS_REC
;
2368 if (path
->dentry
!= path
->mnt
->mnt_root
)
2371 type
= flags_to_propagation_type(ms_flags
);
2376 if (type
== MS_SHARED
) {
2377 err
= invent_group_ids(mnt
, recurse
);
2383 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
2384 change_mnt_propagation(m
, type
);
2385 unlock_mount_hash();
2392 static struct mount
*__do_loopback(struct path
*old_path
, int recurse
)
2394 struct mount
*mnt
= ERR_PTR(-EINVAL
), *old
= real_mount(old_path
->mnt
);
2396 if (IS_MNT_UNBINDABLE(old
))
2399 if (!check_mnt(old
) && old_path
->dentry
->d_op
!= &ns_dentry_operations
)
2402 if (!recurse
&& has_locked_children(old
, old_path
->dentry
))
2406 mnt
= copy_tree(old
, old_path
->dentry
, CL_COPY_MNT_NS_FILE
);
2408 mnt
= clone_mnt(old
, old_path
->dentry
, 0);
2411 mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2417 * do loopback mount.
2419 static int do_loopback(struct path
*path
, const char *old_name
,
2422 struct path old_path
;
2423 struct mount
*mnt
= NULL
, *parent
;
2424 struct mountpoint
*mp
;
2426 if (!old_name
|| !*old_name
)
2428 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
2433 if (mnt_ns_loop(old_path
.dentry
))
2436 mp
= lock_mount(path
);
2442 parent
= real_mount(path
->mnt
);
2443 if (!check_mnt(parent
))
2446 mnt
= __do_loopback(&old_path
, recurse
);
2452 err
= graft_tree(mnt
, parent
, mp
);
2455 umount_tree(mnt
, UMOUNT_SYNC
);
2456 unlock_mount_hash();
2461 path_put(&old_path
);
2465 static struct file
*open_detached_copy(struct path
*path
, bool recursive
)
2467 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2468 struct mnt_namespace
*ns
= alloc_mnt_ns(user_ns
, true);
2469 struct mount
*mnt
, *p
;
2473 return ERR_CAST(ns
);
2476 mnt
= __do_loopback(path
, recursive
);
2480 return ERR_CAST(mnt
);
2484 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2489 list_add_tail(&ns
->list
, &mnt
->mnt_list
);
2491 unlock_mount_hash();
2495 path
->mnt
= &mnt
->mnt
;
2496 file
= dentry_open(path
, O_PATH
, current_cred());
2498 dissolve_on_fput(path
->mnt
);
2500 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
2504 SYSCALL_DEFINE3(open_tree
, int, dfd
, const char __user
*, filename
, unsigned, flags
)
2508 int lookup_flags
= LOOKUP_AUTOMOUNT
| LOOKUP_FOLLOW
;
2509 bool detached
= flags
& OPEN_TREE_CLONE
;
2513 BUILD_BUG_ON(OPEN_TREE_CLOEXEC
!= O_CLOEXEC
);
2515 if (flags
& ~(AT_EMPTY_PATH
| AT_NO_AUTOMOUNT
| AT_RECURSIVE
|
2516 AT_SYMLINK_NOFOLLOW
| OPEN_TREE_CLONE
|
2520 if ((flags
& (AT_RECURSIVE
| OPEN_TREE_CLONE
)) == AT_RECURSIVE
)
2523 if (flags
& AT_NO_AUTOMOUNT
)
2524 lookup_flags
&= ~LOOKUP_AUTOMOUNT
;
2525 if (flags
& AT_SYMLINK_NOFOLLOW
)
2526 lookup_flags
&= ~LOOKUP_FOLLOW
;
2527 if (flags
& AT_EMPTY_PATH
)
2528 lookup_flags
|= LOOKUP_EMPTY
;
2530 if (detached
&& !may_mount())
2533 fd
= get_unused_fd_flags(flags
& O_CLOEXEC
);
2537 error
= user_path_at(dfd
, filename
, lookup_flags
, &path
);
2538 if (unlikely(error
)) {
2539 file
= ERR_PTR(error
);
2542 file
= open_detached_copy(&path
, flags
& AT_RECURSIVE
);
2544 file
= dentry_open(&path
, O_PATH
, current_cred());
2549 return PTR_ERR(file
);
2551 fd_install(fd
, file
);
2556 * Don't allow locked mount flags to be cleared.
2558 * No locks need to be held here while testing the various MNT_LOCK
2559 * flags because those flags can never be cleared once they are set.
2561 static bool can_change_locked_flags(struct mount
*mnt
, unsigned int mnt_flags
)
2563 unsigned int fl
= mnt
->mnt
.mnt_flags
;
2565 if ((fl
& MNT_LOCK_READONLY
) &&
2566 !(mnt_flags
& MNT_READONLY
))
2569 if ((fl
& MNT_LOCK_NODEV
) &&
2570 !(mnt_flags
& MNT_NODEV
))
2573 if ((fl
& MNT_LOCK_NOSUID
) &&
2574 !(mnt_flags
& MNT_NOSUID
))
2577 if ((fl
& MNT_LOCK_NOEXEC
) &&
2578 !(mnt_flags
& MNT_NOEXEC
))
2581 if ((fl
& MNT_LOCK_ATIME
) &&
2582 ((fl
& MNT_ATIME_MASK
) != (mnt_flags
& MNT_ATIME_MASK
)))
2588 static int change_mount_ro_state(struct mount
*mnt
, unsigned int mnt_flags
)
2590 bool readonly_request
= (mnt_flags
& MNT_READONLY
);
2592 if (readonly_request
== __mnt_is_readonly(&mnt
->mnt
))
2595 if (readonly_request
)
2596 return mnt_make_readonly(mnt
);
2598 mnt
->mnt
.mnt_flags
&= ~MNT_READONLY
;
2602 static void set_mount_attributes(struct mount
*mnt
, unsigned int mnt_flags
)
2604 mnt_flags
|= mnt
->mnt
.mnt_flags
& ~MNT_USER_SETTABLE_MASK
;
2605 mnt
->mnt
.mnt_flags
= mnt_flags
;
2606 touch_mnt_namespace(mnt
->mnt_ns
);
2609 static void mnt_warn_timestamp_expiry(struct path
*mountpoint
, struct vfsmount
*mnt
)
2611 struct super_block
*sb
= mnt
->mnt_sb
;
2613 if (!__mnt_is_readonly(mnt
) &&
2614 (!(sb
->s_iflags
& SB_I_TS_EXPIRY_WARNED
)) &&
2615 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX
> sb
->s_time_max
)) {
2616 char *buf
= (char *)__get_free_page(GFP_KERNEL
);
2617 char *mntpath
= buf
? d_path(mountpoint
, buf
, PAGE_SIZE
) : ERR_PTR(-ENOMEM
);
2620 time64_to_tm(sb
->s_time_max
, 0, &tm
);
2622 pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n",
2624 is_mounted(mnt
) ? "remounted" : "mounted",
2626 tm
.tm_year
+1900, (unsigned long long)sb
->s_time_max
);
2628 free_page((unsigned long)buf
);
2629 sb
->s_iflags
|= SB_I_TS_EXPIRY_WARNED
;
2634 * Handle reconfiguration of the mountpoint only without alteration of the
2635 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2638 static int do_reconfigure_mnt(struct path
*path
, unsigned int mnt_flags
)
2640 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2641 struct mount
*mnt
= real_mount(path
->mnt
);
2644 if (!check_mnt(mnt
))
2647 if (path
->dentry
!= mnt
->mnt
.mnt_root
)
2650 if (!can_change_locked_flags(mnt
, mnt_flags
))
2654 * We're only checking whether the superblock is read-only not
2655 * changing it, so only take down_read(&sb->s_umount).
2657 down_read(&sb
->s_umount
);
2659 ret
= change_mount_ro_state(mnt
, mnt_flags
);
2661 set_mount_attributes(mnt
, mnt_flags
);
2662 unlock_mount_hash();
2663 up_read(&sb
->s_umount
);
2665 mnt_warn_timestamp_expiry(path
, &mnt
->mnt
);
2671 * change filesystem flags. dir should be a physical root of filesystem.
2672 * If you've mounted a non-root directory somewhere and want to do remount
2673 * on it - tough luck.
2675 static int do_remount(struct path
*path
, int ms_flags
, int sb_flags
,
2676 int mnt_flags
, void *data
)
2679 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2680 struct mount
*mnt
= real_mount(path
->mnt
);
2681 struct fs_context
*fc
;
2683 if (!check_mnt(mnt
))
2686 if (path
->dentry
!= path
->mnt
->mnt_root
)
2689 if (!can_change_locked_flags(mnt
, mnt_flags
))
2692 fc
= fs_context_for_reconfigure(path
->dentry
, sb_flags
, MS_RMT_MASK
);
2697 err
= parse_monolithic_mount_data(fc
, data
);
2699 down_write(&sb
->s_umount
);
2701 if (ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
)) {
2702 err
= reconfigure_super(fc
);
2705 set_mount_attributes(mnt
, mnt_flags
);
2706 unlock_mount_hash();
2709 up_write(&sb
->s_umount
);
2712 mnt_warn_timestamp_expiry(path
, &mnt
->mnt
);
2718 static inline int tree_contains_unbindable(struct mount
*mnt
)
2721 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2722 if (IS_MNT_UNBINDABLE(p
))
2729 * Check that there aren't references to earlier/same mount namespaces in the
2730 * specified subtree. Such references can act as pins for mount namespaces
2731 * that aren't checked by the mount-cycle checking code, thereby allowing
2732 * cycles to be made.
2734 static bool check_for_nsfs_mounts(struct mount
*subtree
)
2740 for (p
= subtree
; p
; p
= next_mnt(p
, subtree
))
2741 if (mnt_ns_loop(p
->mnt
.mnt_root
))
2746 unlock_mount_hash();
2750 static int do_set_group(struct path
*from_path
, struct path
*to_path
)
2752 struct mount
*from
, *to
;
2755 from
= real_mount(from_path
->mnt
);
2756 to
= real_mount(to_path
->mnt
);
2761 /* To and From must be mounted */
2762 if (!is_mounted(&from
->mnt
))
2764 if (!is_mounted(&to
->mnt
))
2768 /* We should be allowed to modify mount namespaces of both mounts */
2769 if (!ns_capable(from
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
))
2771 if (!ns_capable(to
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
))
2775 /* To and From paths should be mount roots */
2776 if (from_path
->dentry
!= from_path
->mnt
->mnt_root
)
2778 if (to_path
->dentry
!= to_path
->mnt
->mnt_root
)
2781 /* Setting sharing groups is only allowed across same superblock */
2782 if (from
->mnt
.mnt_sb
!= to
->mnt
.mnt_sb
)
2785 /* From mount root should be wider than To mount root */
2786 if (!is_subdir(to
->mnt
.mnt_root
, from
->mnt
.mnt_root
))
2789 /* From mount should not have locked children in place of To's root */
2790 if (has_locked_children(from
, to
->mnt
.mnt_root
))
2793 /* Setting sharing groups is only allowed on private mounts */
2794 if (IS_MNT_SHARED(to
) || IS_MNT_SLAVE(to
))
2797 /* From should not be private */
2798 if (!IS_MNT_SHARED(from
) && !IS_MNT_SLAVE(from
))
2801 if (IS_MNT_SLAVE(from
)) {
2802 struct mount
*m
= from
->mnt_master
;
2804 list_add(&to
->mnt_slave
, &m
->mnt_slave_list
);
2808 if (IS_MNT_SHARED(from
)) {
2809 to
->mnt_group_id
= from
->mnt_group_id
;
2810 list_add(&to
->mnt_share
, &from
->mnt_share
);
2813 unlock_mount_hash();
2822 static int do_move_mount(struct path
*old_path
, struct path
*new_path
)
2824 struct mnt_namespace
*ns
;
2827 struct mount
*parent
;
2828 struct mountpoint
*mp
, *old_mp
;
2832 mp
= lock_mount(new_path
);
2836 old
= real_mount(old_path
->mnt
);
2837 p
= real_mount(new_path
->mnt
);
2838 parent
= old
->mnt_parent
;
2839 attached
= mnt_has_parent(old
);
2840 old_mp
= old
->mnt_mp
;
2844 /* The mountpoint must be in our namespace. */
2848 /* The thing moved must be mounted... */
2849 if (!is_mounted(&old
->mnt
))
2852 /* ... and either ours or the root of anon namespace */
2853 if (!(attached
? check_mnt(old
) : is_anon_ns(ns
)))
2856 if (old
->mnt
.mnt_flags
& MNT_LOCKED
)
2859 if (old_path
->dentry
!= old_path
->mnt
->mnt_root
)
2862 if (d_is_dir(new_path
->dentry
) !=
2863 d_is_dir(old_path
->dentry
))
2866 * Don't move a mount residing in a shared parent.
2868 if (attached
&& IS_MNT_SHARED(parent
))
2871 * Don't move a mount tree containing unbindable mounts to a destination
2872 * mount which is shared.
2874 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
2877 if (!check_for_nsfs_mounts(old
))
2879 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
2883 err
= attach_recursive_mnt(old
, real_mount(new_path
->mnt
), mp
,
2888 /* if the mount is moved, it should no longer be expire
2890 list_del_init(&old
->mnt_expire
);
2892 put_mountpoint(old_mp
);
2897 mntput_no_expire(parent
);
2904 static int do_move_mount_old(struct path
*path
, const char *old_name
)
2906 struct path old_path
;
2909 if (!old_name
|| !*old_name
)
2912 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
2916 err
= do_move_mount(&old_path
, path
);
2917 path_put(&old_path
);
2922 * add a mount into a namespace's mount tree
2924 static int do_add_mount(struct mount
*newmnt
, struct mountpoint
*mp
,
2925 const struct path
*path
, int mnt_flags
)
2927 struct mount
*parent
= real_mount(path
->mnt
);
2929 mnt_flags
&= ~MNT_INTERNAL_FLAGS
;
2931 if (unlikely(!check_mnt(parent
))) {
2932 /* that's acceptable only for automounts done in private ns */
2933 if (!(mnt_flags
& MNT_SHRINKABLE
))
2935 /* ... and for those we'd better have mountpoint still alive */
2936 if (!parent
->mnt_ns
)
2940 /* Refuse the same filesystem on the same mount point */
2941 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
2942 path
->mnt
->mnt_root
== path
->dentry
)
2945 if (d_is_symlink(newmnt
->mnt
.mnt_root
))
2948 newmnt
->mnt
.mnt_flags
= mnt_flags
;
2949 return graft_tree(newmnt
, parent
, mp
);
2952 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
);
2955 * Create a new mount using a superblock configuration and request it
2956 * be added to the namespace tree.
2958 static int do_new_mount_fc(struct fs_context
*fc
, struct path
*mountpoint
,
2959 unsigned int mnt_flags
)
2961 struct vfsmount
*mnt
;
2962 struct mountpoint
*mp
;
2963 struct super_block
*sb
= fc
->root
->d_sb
;
2966 error
= security_sb_kern_mount(sb
);
2967 if (!error
&& mount_too_revealing(sb
, &mnt_flags
))
2970 if (unlikely(error
)) {
2975 up_write(&sb
->s_umount
);
2977 mnt
= vfs_create_mount(fc
);
2979 return PTR_ERR(mnt
);
2981 mnt_warn_timestamp_expiry(mountpoint
, mnt
);
2983 mp
= lock_mount(mountpoint
);
2988 error
= do_add_mount(real_mount(mnt
), mp
, mountpoint
, mnt_flags
);
2996 * create a new mount for userspace and request it to be added into the
2999 static int do_new_mount(struct path
*path
, const char *fstype
, int sb_flags
,
3000 int mnt_flags
, const char *name
, void *data
)
3002 struct file_system_type
*type
;
3003 struct fs_context
*fc
;
3004 const char *subtype
= NULL
;
3010 type
= get_fs_type(fstype
);
3014 if (type
->fs_flags
& FS_HAS_SUBTYPE
) {
3015 subtype
= strchr(fstype
, '.');
3019 put_filesystem(type
);
3025 fc
= fs_context_for_mount(type
, sb_flags
);
3026 put_filesystem(type
);
3031 err
= vfs_parse_fs_string(fc
, "subtype",
3032 subtype
, strlen(subtype
));
3034 err
= vfs_parse_fs_string(fc
, "source", name
, strlen(name
));
3036 err
= parse_monolithic_mount_data(fc
, data
);
3037 if (!err
&& !mount_capable(fc
))
3040 err
= vfs_get_tree(fc
);
3042 err
= do_new_mount_fc(fc
, path
, mnt_flags
);
3048 int finish_automount(struct vfsmount
*m
, const struct path
*path
)
3050 struct dentry
*dentry
= path
->dentry
;
3051 struct mountpoint
*mp
;
3060 mnt
= real_mount(m
);
3061 /* The new mount record should have at least 2 refs to prevent it being
3062 * expired before we get a chance to add it
3064 BUG_ON(mnt_get_count(mnt
) < 2);
3066 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
3067 m
->mnt_root
== dentry
) {
3073 * we don't want to use lock_mount() - in this case finding something
3074 * that overmounts our mountpoint to be means "quitely drop what we've
3075 * got", not "try to mount it on top".
3077 inode_lock(dentry
->d_inode
);
3079 if (unlikely(cant_mount(dentry
))) {
3081 goto discard_locked
;
3084 if (unlikely(__lookup_mnt(path
->mnt
, dentry
))) {
3087 goto discard_locked
;
3090 mp
= get_mountpoint(dentry
);
3093 goto discard_locked
;
3096 err
= do_add_mount(mnt
, mp
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
3105 inode_unlock(dentry
->d_inode
);
3107 /* remove m from any expiration list it may be on */
3108 if (!list_empty(&mnt
->mnt_expire
)) {
3110 list_del_init(&mnt
->mnt_expire
);
3119 * mnt_set_expiry - Put a mount on an expiration list
3120 * @mnt: The mount to list.
3121 * @expiry_list: The list to add the mount to.
3123 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
3127 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
3131 EXPORT_SYMBOL(mnt_set_expiry
);
3134 * process a list of expirable mountpoints with the intent of discarding any
3135 * mountpoints that aren't in use and haven't been touched since last we came
3138 void mark_mounts_for_expiry(struct list_head
*mounts
)
3140 struct mount
*mnt
, *next
;
3141 LIST_HEAD(graveyard
);
3143 if (list_empty(mounts
))
3149 /* extract from the expiration list every vfsmount that matches the
3150 * following criteria:
3151 * - only referenced by its parent vfsmount
3152 * - still marked for expiry (marked on the last call here; marks are
3153 * cleared by mntput())
3155 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
3156 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
3157 propagate_mount_busy(mnt
, 1))
3159 list_move(&mnt
->mnt_expire
, &graveyard
);
3161 while (!list_empty(&graveyard
)) {
3162 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
3163 touch_mnt_namespace(mnt
->mnt_ns
);
3164 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
3166 unlock_mount_hash();
3170 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
3173 * Ripoff of 'select_parent()'
3175 * search the list of submounts for a given mountpoint, and move any
3176 * shrinkable submounts to the 'graveyard' list.
3178 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
3180 struct mount
*this_parent
= parent
;
3181 struct list_head
*next
;
3185 next
= this_parent
->mnt_mounts
.next
;
3187 while (next
!= &this_parent
->mnt_mounts
) {
3188 struct list_head
*tmp
= next
;
3189 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
3192 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
3195 * Descend a level if the d_mounts list is non-empty.
3197 if (!list_empty(&mnt
->mnt_mounts
)) {
3202 if (!propagate_mount_busy(mnt
, 1)) {
3203 list_move_tail(&mnt
->mnt_expire
, graveyard
);
3208 * All done at this level ... ascend and resume the search
3210 if (this_parent
!= parent
) {
3211 next
= this_parent
->mnt_child
.next
;
3212 this_parent
= this_parent
->mnt_parent
;
3219 * process a list of expirable mountpoints with the intent of discarding any
3220 * submounts of a specific parent mountpoint
3222 * mount_lock must be held for write
3224 static void shrink_submounts(struct mount
*mnt
)
3226 LIST_HEAD(graveyard
);
3229 /* extract submounts of 'mountpoint' from the expiration list */
3230 while (select_submounts(mnt
, &graveyard
)) {
3231 while (!list_empty(&graveyard
)) {
3232 m
= list_first_entry(&graveyard
, struct mount
,
3234 touch_mnt_namespace(m
->mnt_ns
);
3235 umount_tree(m
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
3240 static void *copy_mount_options(const void __user
* data
)
3243 unsigned left
, offset
;
3248 copy
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
3250 return ERR_PTR(-ENOMEM
);
3252 left
= copy_from_user(copy
, data
, PAGE_SIZE
);
3255 * Not all architectures have an exact copy_from_user(). Resort to
3258 offset
= PAGE_SIZE
- left
;
3261 if (get_user(c
, (const char __user
*)data
+ offset
))
3268 if (left
== PAGE_SIZE
) {
3270 return ERR_PTR(-EFAULT
);
3276 static char *copy_mount_string(const void __user
*data
)
3278 return data
? strndup_user(data
, PATH_MAX
) : NULL
;
3282 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3283 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3285 * data is a (void *) that can point to any structure up to
3286 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3287 * information (or be NULL).
3289 * Pre-0.97 versions of mount() didn't have a flags word.
3290 * When the flags word was introduced its top half was required
3291 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3292 * Therefore, if this magic number is present, it carries no information
3293 * and must be discarded.
3295 int path_mount(const char *dev_name
, struct path
*path
,
3296 const char *type_page
, unsigned long flags
, void *data_page
)
3298 unsigned int mnt_flags
= 0, sb_flags
;
3302 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
3303 flags
&= ~MS_MGC_MSK
;
3305 /* Basic sanity checks */
3307 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
3309 if (flags
& MS_NOUSER
)
3312 ret
= security_sb_mount(dev_name
, path
, type_page
, flags
, data_page
);
3317 if (flags
& SB_MANDLOCK
)
3320 /* Default to relatime unless overriden */
3321 if (!(flags
& MS_NOATIME
))
3322 mnt_flags
|= MNT_RELATIME
;
3324 /* Separate the per-mountpoint flags */
3325 if (flags
& MS_NOSUID
)
3326 mnt_flags
|= MNT_NOSUID
;
3327 if (flags
& MS_NODEV
)
3328 mnt_flags
|= MNT_NODEV
;
3329 if (flags
& MS_NOEXEC
)
3330 mnt_flags
|= MNT_NOEXEC
;
3331 if (flags
& MS_NOATIME
)
3332 mnt_flags
|= MNT_NOATIME
;
3333 if (flags
& MS_NODIRATIME
)
3334 mnt_flags
|= MNT_NODIRATIME
;
3335 if (flags
& MS_STRICTATIME
)
3336 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
3337 if (flags
& MS_RDONLY
)
3338 mnt_flags
|= MNT_READONLY
;
3339 if (flags
& MS_NOSYMFOLLOW
)
3340 mnt_flags
|= MNT_NOSYMFOLLOW
;
3342 /* The default atime for remount is preservation */
3343 if ((flags
& MS_REMOUNT
) &&
3344 ((flags
& (MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
|
3345 MS_STRICTATIME
)) == 0)) {
3346 mnt_flags
&= ~MNT_ATIME_MASK
;
3347 mnt_flags
|= path
->mnt
->mnt_flags
& MNT_ATIME_MASK
;
3350 sb_flags
= flags
& (SB_RDONLY
|
3359 if ((flags
& (MS_REMOUNT
| MS_BIND
)) == (MS_REMOUNT
| MS_BIND
))
3360 return do_reconfigure_mnt(path
, mnt_flags
);
3361 if (flags
& MS_REMOUNT
)
3362 return do_remount(path
, flags
, sb_flags
, mnt_flags
, data_page
);
3363 if (flags
& MS_BIND
)
3364 return do_loopback(path
, dev_name
, flags
& MS_REC
);
3365 if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
3366 return do_change_type(path
, flags
);
3367 if (flags
& MS_MOVE
)
3368 return do_move_mount_old(path
, dev_name
);
3370 return do_new_mount(path
, type_page
, sb_flags
, mnt_flags
, dev_name
,
3374 long do_mount(const char *dev_name
, const char __user
*dir_name
,
3375 const char *type_page
, unsigned long flags
, void *data_page
)
3380 ret
= user_path_at(AT_FDCWD
, dir_name
, LOOKUP_FOLLOW
, &path
);
3383 ret
= path_mount(dev_name
, &path
, type_page
, flags
, data_page
);
3388 static struct ucounts
*inc_mnt_namespaces(struct user_namespace
*ns
)
3390 return inc_ucount(ns
, current_euid(), UCOUNT_MNT_NAMESPACES
);
3393 static void dec_mnt_namespaces(struct ucounts
*ucounts
)
3395 dec_ucount(ucounts
, UCOUNT_MNT_NAMESPACES
);
3398 static void free_mnt_ns(struct mnt_namespace
*ns
)
3400 if (!is_anon_ns(ns
))
3401 ns_free_inum(&ns
->ns
);
3402 dec_mnt_namespaces(ns
->ucounts
);
3403 put_user_ns(ns
->user_ns
);
3408 * Assign a sequence number so we can detect when we attempt to bind
3409 * mount a reference to an older mount namespace into the current
3410 * mount namespace, preventing reference counting loops. A 64bit
3411 * number incrementing at 10Ghz will take 12,427 years to wrap which
3412 * is effectively never, so we can ignore the possibility.
3414 static atomic64_t mnt_ns_seq
= ATOMIC64_INIT(1);
3416 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*user_ns
, bool anon
)
3418 struct mnt_namespace
*new_ns
;
3419 struct ucounts
*ucounts
;
3422 ucounts
= inc_mnt_namespaces(user_ns
);
3424 return ERR_PTR(-ENOSPC
);
3426 new_ns
= kzalloc(sizeof(struct mnt_namespace
), GFP_KERNEL_ACCOUNT
);
3428 dec_mnt_namespaces(ucounts
);
3429 return ERR_PTR(-ENOMEM
);
3432 ret
= ns_alloc_inum(&new_ns
->ns
);
3435 dec_mnt_namespaces(ucounts
);
3436 return ERR_PTR(ret
);
3439 new_ns
->ns
.ops
= &mntns_operations
;
3441 new_ns
->seq
= atomic64_add_return(1, &mnt_ns_seq
);
3442 refcount_set(&new_ns
->ns
.count
, 1);
3443 INIT_LIST_HEAD(&new_ns
->list
);
3444 init_waitqueue_head(&new_ns
->poll
);
3445 spin_lock_init(&new_ns
->ns_lock
);
3446 new_ns
->user_ns
= get_user_ns(user_ns
);
3447 new_ns
->ucounts
= ucounts
;
3452 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
3453 struct user_namespace
*user_ns
, struct fs_struct
*new_fs
)
3455 struct mnt_namespace
*new_ns
;
3456 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
3457 struct mount
*p
, *q
;
3464 if (likely(!(flags
& CLONE_NEWNS
))) {
3471 new_ns
= alloc_mnt_ns(user_ns
, false);
3476 /* First pass: copy the tree topology */
3477 copy_flags
= CL_COPY_UNBINDABLE
| CL_EXPIRE
;
3478 if (user_ns
!= ns
->user_ns
)
3479 copy_flags
|= CL_SHARED_TO_SLAVE
;
3480 new = copy_tree(old
, old
->mnt
.mnt_root
, copy_flags
);
3483 free_mnt_ns(new_ns
);
3484 return ERR_CAST(new);
3486 if (user_ns
!= ns
->user_ns
) {
3489 unlock_mount_hash();
3492 list_add_tail(&new_ns
->list
, &new->mnt_list
);
3495 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3496 * as belonging to new namespace. We have already acquired a private
3497 * fs_struct, so tsk->fs->lock is not needed.
3505 if (&p
->mnt
== new_fs
->root
.mnt
) {
3506 new_fs
->root
.mnt
= mntget(&q
->mnt
);
3509 if (&p
->mnt
== new_fs
->pwd
.mnt
) {
3510 new_fs
->pwd
.mnt
= mntget(&q
->mnt
);
3514 p
= next_mnt(p
, old
);
3515 q
= next_mnt(q
, new);
3518 while (p
->mnt
.mnt_root
!= q
->mnt
.mnt_root
)
3519 p
= next_mnt(p
, old
);
3531 struct dentry
*mount_subtree(struct vfsmount
*m
, const char *name
)
3533 struct mount
*mnt
= real_mount(m
);
3534 struct mnt_namespace
*ns
;
3535 struct super_block
*s
;
3539 ns
= alloc_mnt_ns(&init_user_ns
, true);
3542 return ERR_CAST(ns
);
3547 list_add(&mnt
->mnt_list
, &ns
->list
);
3549 err
= vfs_path_lookup(m
->mnt_root
, m
,
3550 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
3555 return ERR_PTR(err
);
3557 /* trade a vfsmount reference for active sb one */
3558 s
= path
.mnt
->mnt_sb
;
3559 atomic_inc(&s
->s_active
);
3561 /* lock the sucker */
3562 down_write(&s
->s_umount
);
3563 /* ... and return the root of (sub)tree on it */
3566 EXPORT_SYMBOL(mount_subtree
);
3568 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
3569 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
3576 kernel_type
= copy_mount_string(type
);
3577 ret
= PTR_ERR(kernel_type
);
3578 if (IS_ERR(kernel_type
))
3581 kernel_dev
= copy_mount_string(dev_name
);
3582 ret
= PTR_ERR(kernel_dev
);
3583 if (IS_ERR(kernel_dev
))
3586 options
= copy_mount_options(data
);
3587 ret
= PTR_ERR(options
);
3588 if (IS_ERR(options
))
3591 ret
= do_mount(kernel_dev
, dir_name
, kernel_type
, flags
, options
);
3602 #define FSMOUNT_VALID_FLAGS \
3603 (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
3604 MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \
3605 MOUNT_ATTR_NOSYMFOLLOW)
3607 #define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
3609 #define MOUNT_SETATTR_PROPAGATION_FLAGS \
3610 (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
3612 static unsigned int attr_flags_to_mnt_flags(u64 attr_flags
)
3614 unsigned int mnt_flags
= 0;
3616 if (attr_flags
& MOUNT_ATTR_RDONLY
)
3617 mnt_flags
|= MNT_READONLY
;
3618 if (attr_flags
& MOUNT_ATTR_NOSUID
)
3619 mnt_flags
|= MNT_NOSUID
;
3620 if (attr_flags
& MOUNT_ATTR_NODEV
)
3621 mnt_flags
|= MNT_NODEV
;
3622 if (attr_flags
& MOUNT_ATTR_NOEXEC
)
3623 mnt_flags
|= MNT_NOEXEC
;
3624 if (attr_flags
& MOUNT_ATTR_NODIRATIME
)
3625 mnt_flags
|= MNT_NODIRATIME
;
3626 if (attr_flags
& MOUNT_ATTR_NOSYMFOLLOW
)
3627 mnt_flags
|= MNT_NOSYMFOLLOW
;
3633 * Create a kernel mount representation for a new, prepared superblock
3634 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3636 SYSCALL_DEFINE3(fsmount
, int, fs_fd
, unsigned int, flags
,
3637 unsigned int, attr_flags
)
3639 struct mnt_namespace
*ns
;
3640 struct fs_context
*fc
;
3642 struct path newmount
;
3645 unsigned int mnt_flags
= 0;
3651 if ((flags
& ~(FSMOUNT_CLOEXEC
)) != 0)
3654 if (attr_flags
& ~FSMOUNT_VALID_FLAGS
)
3657 mnt_flags
= attr_flags_to_mnt_flags(attr_flags
);
3659 switch (attr_flags
& MOUNT_ATTR__ATIME
) {
3660 case MOUNT_ATTR_STRICTATIME
:
3662 case MOUNT_ATTR_NOATIME
:
3663 mnt_flags
|= MNT_NOATIME
;
3665 case MOUNT_ATTR_RELATIME
:
3666 mnt_flags
|= MNT_RELATIME
;
3677 if (f
.file
->f_op
!= &fscontext_fops
)
3680 fc
= f
.file
->private_data
;
3682 ret
= mutex_lock_interruptible(&fc
->uapi_mutex
);
3686 /* There must be a valid superblock or we can't mount it */
3692 if (mount_too_revealing(fc
->root
->d_sb
, &mnt_flags
)) {
3693 pr_warn("VFS: Mount too revealing\n");
3698 if (fc
->phase
!= FS_CONTEXT_AWAITING_MOUNT
)
3701 if (fc
->sb_flags
& SB_MANDLOCK
)
3704 newmount
.mnt
= vfs_create_mount(fc
);
3705 if (IS_ERR(newmount
.mnt
)) {
3706 ret
= PTR_ERR(newmount
.mnt
);
3709 newmount
.dentry
= dget(fc
->root
);
3710 newmount
.mnt
->mnt_flags
= mnt_flags
;
3712 /* We've done the mount bit - now move the file context into more or
3713 * less the same state as if we'd done an fspick(). We don't want to
3714 * do any memory allocation or anything like that at this point as we
3715 * don't want to have to handle any errors incurred.
3717 vfs_clean_context(fc
);
3719 ns
= alloc_mnt_ns(current
->nsproxy
->mnt_ns
->user_ns
, true);
3724 mnt
= real_mount(newmount
.mnt
);
3728 list_add(&mnt
->mnt_list
, &ns
->list
);
3729 mntget(newmount
.mnt
);
3731 /* Attach to an apparent O_PATH fd with a note that we need to unmount
3732 * it, not just simply put it.
3734 file
= dentry_open(&newmount
, O_PATH
, fc
->cred
);
3736 dissolve_on_fput(newmount
.mnt
);
3737 ret
= PTR_ERR(file
);
3740 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
3742 ret
= get_unused_fd_flags((flags
& FSMOUNT_CLOEXEC
) ? O_CLOEXEC
: 0);
3744 fd_install(ret
, file
);
3749 path_put(&newmount
);
3751 mutex_unlock(&fc
->uapi_mutex
);
3758 * Move a mount from one place to another. In combination with
3759 * fsopen()/fsmount() this is used to install a new mount and in combination
3760 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
3763 * Note the flags value is a combination of MOVE_MOUNT_* flags.
3765 SYSCALL_DEFINE5(move_mount
,
3766 int, from_dfd
, const char __user
*, from_pathname
,
3767 int, to_dfd
, const char __user
*, to_pathname
,
3768 unsigned int, flags
)
3770 struct path from_path
, to_path
;
3771 unsigned int lflags
;
3777 if (flags
& ~MOVE_MOUNT__MASK
)
3780 /* If someone gives a pathname, they aren't permitted to move
3781 * from an fd that requires unmount as we can't get at the flag
3782 * to clear it afterwards.
3785 if (flags
& MOVE_MOUNT_F_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
3786 if (flags
& MOVE_MOUNT_F_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
3787 if (flags
& MOVE_MOUNT_F_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
3789 ret
= user_path_at(from_dfd
, from_pathname
, lflags
, &from_path
);
3794 if (flags
& MOVE_MOUNT_T_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
3795 if (flags
& MOVE_MOUNT_T_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
3796 if (flags
& MOVE_MOUNT_T_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
3798 ret
= user_path_at(to_dfd
, to_pathname
, lflags
, &to_path
);
3802 ret
= security_move_mount(&from_path
, &to_path
);
3806 if (flags
& MOVE_MOUNT_SET_GROUP
)
3807 ret
= do_set_group(&from_path
, &to_path
);
3809 ret
= do_move_mount(&from_path
, &to_path
);
3814 path_put(&from_path
);
3819 * Return true if path is reachable from root
3821 * namespace_sem or mount_lock is held
3823 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
3824 const struct path
*root
)
3826 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
3827 dentry
= mnt
->mnt_mountpoint
;
3828 mnt
= mnt
->mnt_parent
;
3830 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
3833 bool path_is_under(const struct path
*path1
, const struct path
*path2
)
3836 read_seqlock_excl(&mount_lock
);
3837 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
3838 read_sequnlock_excl(&mount_lock
);
3841 EXPORT_SYMBOL(path_is_under
);
3844 * pivot_root Semantics:
3845 * Moves the root file system of the current process to the directory put_old,
3846 * makes new_root as the new root file system of the current process, and sets
3847 * root/cwd of all processes which had them on the current root to new_root.
3850 * The new_root and put_old must be directories, and must not be on the
3851 * same file system as the current process root. The put_old must be
3852 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3853 * pointed to by put_old must yield the same directory as new_root. No other
3854 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3856 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3857 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
3858 * in this situation.
3861 * - we don't move root/cwd if they are not at the root (reason: if something
3862 * cared enough to change them, it's probably wrong to force them elsewhere)
3863 * - it's okay to pick a root that isn't the root of a file system, e.g.
3864 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3865 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3868 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
3869 const char __user
*, put_old
)
3871 struct path
new, old
, root
;
3872 struct mount
*new_mnt
, *root_mnt
, *old_mnt
, *root_parent
, *ex_parent
;
3873 struct mountpoint
*old_mp
, *root_mp
;
3879 error
= user_path_at(AT_FDCWD
, new_root
,
3880 LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
, &new);
3884 error
= user_path_at(AT_FDCWD
, put_old
,
3885 LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
, &old
);
3889 error
= security_sb_pivotroot(&old
, &new);
3893 get_fs_root(current
->fs
, &root
);
3894 old_mp
= lock_mount(&old
);
3895 error
= PTR_ERR(old_mp
);
3900 new_mnt
= real_mount(new.mnt
);
3901 root_mnt
= real_mount(root
.mnt
);
3902 old_mnt
= real_mount(old
.mnt
);
3903 ex_parent
= new_mnt
->mnt_parent
;
3904 root_parent
= root_mnt
->mnt_parent
;
3905 if (IS_MNT_SHARED(old_mnt
) ||
3906 IS_MNT_SHARED(ex_parent
) ||
3907 IS_MNT_SHARED(root_parent
))
3909 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
3911 if (new_mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
3914 if (d_unlinked(new.dentry
))
3917 if (new_mnt
== root_mnt
|| old_mnt
== root_mnt
)
3918 goto out4
; /* loop, on the same file system */
3920 if (root
.mnt
->mnt_root
!= root
.dentry
)
3921 goto out4
; /* not a mountpoint */
3922 if (!mnt_has_parent(root_mnt
))
3923 goto out4
; /* not attached */
3924 if (new.mnt
->mnt_root
!= new.dentry
)
3925 goto out4
; /* not a mountpoint */
3926 if (!mnt_has_parent(new_mnt
))
3927 goto out4
; /* not attached */
3928 /* make sure we can reach put_old from new_root */
3929 if (!is_path_reachable(old_mnt
, old
.dentry
, &new))
3931 /* make certain new is below the root */
3932 if (!is_path_reachable(new_mnt
, new.dentry
, &root
))
3935 umount_mnt(new_mnt
);
3936 root_mp
= unhash_mnt(root_mnt
); /* we'll need its mountpoint */
3937 if (root_mnt
->mnt
.mnt_flags
& MNT_LOCKED
) {
3938 new_mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
3939 root_mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
3941 /* mount old root on put_old */
3942 attach_mnt(root_mnt
, old_mnt
, old_mp
);
3943 /* mount new_root on / */
3944 attach_mnt(new_mnt
, root_parent
, root_mp
);
3945 mnt_add_count(root_parent
, -1);
3946 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
3947 /* A moved mount should not expire automatically */
3948 list_del_init(&new_mnt
->mnt_expire
);
3949 put_mountpoint(root_mp
);
3950 unlock_mount_hash();
3951 chroot_fs_refs(&root
, &new);
3954 unlock_mount(old_mp
);
3956 mntput_no_expire(ex_parent
);
3967 static unsigned int recalc_flags(struct mount_kattr
*kattr
, struct mount
*mnt
)
3969 unsigned int flags
= mnt
->mnt
.mnt_flags
;
3971 /* flags to clear */
3972 flags
&= ~kattr
->attr_clr
;
3973 /* flags to raise */
3974 flags
|= kattr
->attr_set
;
3979 static int can_idmap_mount(const struct mount_kattr
*kattr
, struct mount
*mnt
)
3981 struct vfsmount
*m
= &mnt
->mnt
;
3982 struct user_namespace
*fs_userns
= m
->mnt_sb
->s_user_ns
;
3984 if (!kattr
->mnt_userns
)
3988 * Creating an idmapped mount with the filesystem wide idmapping
3989 * doesn't make sense so block that. We don't allow mushy semantics.
3991 if (kattr
->mnt_userns
== fs_userns
)
3995 * Once a mount has been idmapped we don't allow it to change its
3996 * mapping. It makes things simpler and callers can just create
3997 * another bind-mount they can idmap if they want to.
3999 if (is_idmapped_mnt(m
))
4002 /* The underlying filesystem doesn't support idmapped mounts yet. */
4003 if (!(m
->mnt_sb
->s_type
->fs_flags
& FS_ALLOW_IDMAP
))
4006 /* We're not controlling the superblock. */
4007 if (!ns_capable(fs_userns
, CAP_SYS_ADMIN
))
4010 /* Mount has already been visible in the filesystem hierarchy. */
4011 if (!is_anon_ns(mnt
->mnt_ns
))
4018 * mnt_allow_writers() - check whether the attribute change allows writers
4019 * @kattr: the new mount attributes
4020 * @mnt: the mount to which @kattr will be applied
4022 * Check whether thew new mount attributes in @kattr allow concurrent writers.
4024 * Return: true if writers need to be held, false if not
4026 static inline bool mnt_allow_writers(const struct mount_kattr
*kattr
,
4027 const struct mount
*mnt
)
4029 return (!(kattr
->attr_set
& MNT_READONLY
) ||
4030 (mnt
->mnt
.mnt_flags
& MNT_READONLY
)) &&
4034 static int mount_setattr_prepare(struct mount_kattr
*kattr
, struct mount
*mnt
)
4039 for (m
= mnt
; m
; m
= next_mnt(m
, mnt
)) {
4040 if (!can_change_locked_flags(m
, recalc_flags(kattr
, m
))) {
4045 err
= can_idmap_mount(kattr
, m
);
4049 if (!mnt_allow_writers(kattr
, m
)) {
4050 err
= mnt_hold_writers(m
);
4055 if (!kattr
->recurse
)
4063 * If we had to call mnt_hold_writers() MNT_WRITE_HOLD will
4064 * be set in @mnt_flags. The loop unsets MNT_WRITE_HOLD for all
4065 * mounts and needs to take care to include the first mount.
4067 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
4068 /* If we had to hold writers unblock them. */
4069 if (p
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
4070 mnt_unhold_writers(p
);
4073 * We're done once the first mount we changed got
4074 * MNT_WRITE_HOLD unset.
4083 static void do_idmap_mount(const struct mount_kattr
*kattr
, struct mount
*mnt
)
4085 struct user_namespace
*mnt_userns
, *old_mnt_userns
;
4087 if (!kattr
->mnt_userns
)
4091 * We're the only ones able to change the mount's idmapping. So
4092 * mnt->mnt.mnt_userns is stable and we can retrieve it directly.
4094 old_mnt_userns
= mnt
->mnt
.mnt_userns
;
4096 mnt_userns
= get_user_ns(kattr
->mnt_userns
);
4097 /* Pairs with smp_load_acquire() in mnt_user_ns(). */
4098 smp_store_release(&mnt
->mnt
.mnt_userns
, mnt_userns
);
4101 * If this is an idmapped filesystem drop the reference we've taken
4102 * in vfs_create_mount() before.
4104 if (!initial_idmapping(old_mnt_userns
))
4105 put_user_ns(old_mnt_userns
);
4108 static void mount_setattr_commit(struct mount_kattr
*kattr
, struct mount
*mnt
)
4112 for (m
= mnt
; m
; m
= next_mnt(m
, mnt
)) {
4115 do_idmap_mount(kattr
, m
);
4116 flags
= recalc_flags(kattr
, m
);
4117 WRITE_ONCE(m
->mnt
.mnt_flags
, flags
);
4119 /* If we had to hold writers unblock them. */
4120 if (m
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
4121 mnt_unhold_writers(m
);
4123 if (kattr
->propagation
)
4124 change_mnt_propagation(m
, kattr
->propagation
);
4125 if (!kattr
->recurse
)
4128 touch_mnt_namespace(mnt
->mnt_ns
);
4131 static int do_mount_setattr(struct path
*path
, struct mount_kattr
*kattr
)
4133 struct mount
*mnt
= real_mount(path
->mnt
);
4136 if (path
->dentry
!= mnt
->mnt
.mnt_root
)
4139 if (kattr
->propagation
) {
4141 * Only take namespace_lock() if we're actually changing
4145 if (kattr
->propagation
== MS_SHARED
) {
4146 err
= invent_group_ids(mnt
, kattr
->recurse
);
4157 /* Ensure that this isn't anything purely vfs internal. */
4158 if (!is_mounted(&mnt
->mnt
))
4162 * If this is an attached mount make sure it's located in the callers
4163 * mount namespace. If it's not don't let the caller interact with it.
4164 * If this is a detached mount make sure it has an anonymous mount
4165 * namespace attached to it, i.e. we've created it via OPEN_TREE_CLONE.
4167 if (!(mnt_has_parent(mnt
) ? check_mnt(mnt
) : is_anon_ns(mnt
->mnt_ns
)))
4171 * First, we get the mount tree in a shape where we can change mount
4172 * properties without failure. If we succeeded to do so we commit all
4173 * changes and if we failed we clean up.
4175 err
= mount_setattr_prepare(kattr
, mnt
);
4177 mount_setattr_commit(kattr
, mnt
);
4180 unlock_mount_hash();
4182 if (kattr
->propagation
) {
4185 cleanup_group_ids(mnt
, NULL
);
4191 static int build_mount_idmapped(const struct mount_attr
*attr
, size_t usize
,
4192 struct mount_kattr
*kattr
, unsigned int flags
)
4195 struct ns_common
*ns
;
4196 struct user_namespace
*mnt_userns
;
4199 if (!((attr
->attr_set
| attr
->attr_clr
) & MOUNT_ATTR_IDMAP
))
4203 * We currently do not support clearing an idmapped mount. If this ever
4204 * is a use-case we can revisit this but for now let's keep it simple
4207 if (attr
->attr_clr
& MOUNT_ATTR_IDMAP
)
4210 if (attr
->userns_fd
> INT_MAX
)
4213 file
= fget(attr
->userns_fd
);
4217 if (!proc_ns_file(file
)) {
4222 ns
= get_proc_ns(file_inode(file
));
4223 if (ns
->ops
->type
!= CLONE_NEWUSER
) {
4229 * The initial idmapping cannot be used to create an idmapped
4230 * mount. We use the initial idmapping as an indicator of a mount
4231 * that is not idmapped. It can simply be passed into helpers that
4232 * are aware of idmapped mounts as a convenient shortcut. A user
4233 * can just create a dedicated identity mapping to achieve the same
4236 mnt_userns
= container_of(ns
, struct user_namespace
, ns
);
4237 if (initial_idmapping(mnt_userns
)) {
4241 kattr
->mnt_userns
= get_user_ns(mnt_userns
);
4248 static int build_mount_kattr(const struct mount_attr
*attr
, size_t usize
,
4249 struct mount_kattr
*kattr
, unsigned int flags
)
4251 unsigned int lookup_flags
= LOOKUP_AUTOMOUNT
| LOOKUP_FOLLOW
;
4253 if (flags
& AT_NO_AUTOMOUNT
)
4254 lookup_flags
&= ~LOOKUP_AUTOMOUNT
;
4255 if (flags
& AT_SYMLINK_NOFOLLOW
)
4256 lookup_flags
&= ~LOOKUP_FOLLOW
;
4257 if (flags
& AT_EMPTY_PATH
)
4258 lookup_flags
|= LOOKUP_EMPTY
;
4260 *kattr
= (struct mount_kattr
) {
4261 .lookup_flags
= lookup_flags
,
4262 .recurse
= !!(flags
& AT_RECURSIVE
),
4265 if (attr
->propagation
& ~MOUNT_SETATTR_PROPAGATION_FLAGS
)
4267 if (hweight32(attr
->propagation
& MOUNT_SETATTR_PROPAGATION_FLAGS
) > 1)
4269 kattr
->propagation
= attr
->propagation
;
4271 if ((attr
->attr_set
| attr
->attr_clr
) & ~MOUNT_SETATTR_VALID_FLAGS
)
4274 kattr
->attr_set
= attr_flags_to_mnt_flags(attr
->attr_set
);
4275 kattr
->attr_clr
= attr_flags_to_mnt_flags(attr
->attr_clr
);
4278 * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
4279 * users wanting to transition to a different atime setting cannot
4280 * simply specify the atime setting in @attr_set, but must also
4281 * specify MOUNT_ATTR__ATIME in the @attr_clr field.
4282 * So ensure that MOUNT_ATTR__ATIME can't be partially set in
4283 * @attr_clr and that @attr_set can't have any atime bits set if
4284 * MOUNT_ATTR__ATIME isn't set in @attr_clr.
4286 if (attr
->attr_clr
& MOUNT_ATTR__ATIME
) {
4287 if ((attr
->attr_clr
& MOUNT_ATTR__ATIME
) != MOUNT_ATTR__ATIME
)
4291 * Clear all previous time settings as they are mutually
4294 kattr
->attr_clr
|= MNT_RELATIME
| MNT_NOATIME
;
4295 switch (attr
->attr_set
& MOUNT_ATTR__ATIME
) {
4296 case MOUNT_ATTR_RELATIME
:
4297 kattr
->attr_set
|= MNT_RELATIME
;
4299 case MOUNT_ATTR_NOATIME
:
4300 kattr
->attr_set
|= MNT_NOATIME
;
4302 case MOUNT_ATTR_STRICTATIME
:
4308 if (attr
->attr_set
& MOUNT_ATTR__ATIME
)
4312 return build_mount_idmapped(attr
, usize
, kattr
, flags
);
4315 static void finish_mount_kattr(struct mount_kattr
*kattr
)
4317 put_user_ns(kattr
->mnt_userns
);
4318 kattr
->mnt_userns
= NULL
;
4321 SYSCALL_DEFINE5(mount_setattr
, int, dfd
, const char __user
*, path
,
4322 unsigned int, flags
, struct mount_attr __user
*, uattr
,
4327 struct mount_attr attr
;
4328 struct mount_kattr kattr
;
4330 BUILD_BUG_ON(sizeof(struct mount_attr
) != MOUNT_ATTR_SIZE_VER0
);
4332 if (flags
& ~(AT_EMPTY_PATH
|
4334 AT_SYMLINK_NOFOLLOW
|
4338 if (unlikely(usize
> PAGE_SIZE
))
4340 if (unlikely(usize
< MOUNT_ATTR_SIZE_VER0
))
4346 err
= copy_struct_from_user(&attr
, sizeof(attr
), uattr
, usize
);
4350 /* Don't bother walking through the mounts if this is a nop. */
4351 if (attr
.attr_set
== 0 &&
4352 attr
.attr_clr
== 0 &&
4353 attr
.propagation
== 0)
4356 err
= build_mount_kattr(&attr
, usize
, &kattr
, flags
);
4360 err
= user_path_at(dfd
, path
, kattr
.lookup_flags
, &target
);
4362 err
= do_mount_setattr(&target
, &kattr
);
4365 finish_mount_kattr(&kattr
);
4369 static void __init
init_mount_tree(void)
4371 struct vfsmount
*mnt
;
4373 struct mnt_namespace
*ns
;
4376 mnt
= vfs_kern_mount(&rootfs_fs_type
, 0, "rootfs", NULL
);
4378 panic("Can't create rootfs");
4380 ns
= alloc_mnt_ns(&init_user_ns
, false);
4382 panic("Can't allocate initial namespace");
4383 m
= real_mount(mnt
);
4387 list_add(&m
->mnt_list
, &ns
->list
);
4388 init_task
.nsproxy
->mnt_ns
= ns
;
4392 root
.dentry
= mnt
->mnt_root
;
4393 mnt
->mnt_flags
|= MNT_LOCKED
;
4395 set_fs_pwd(current
->fs
, &root
);
4396 set_fs_root(current
->fs
, &root
);
4399 void __init
mnt_init(void)
4403 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
4404 0, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_ACCOUNT
, NULL
);
4406 mount_hashtable
= alloc_large_system_hash("Mount-cache",
4407 sizeof(struct hlist_head
),
4410 &m_hash_shift
, &m_hash_mask
, 0, 0);
4411 mountpoint_hashtable
= alloc_large_system_hash("Mountpoint-cache",
4412 sizeof(struct hlist_head
),
4415 &mp_hash_shift
, &mp_hash_mask
, 0, 0);
4417 if (!mount_hashtable
|| !mountpoint_hashtable
)
4418 panic("Failed to allocate mount hash table\n");
4424 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
4426 fs_kobj
= kobject_create_and_add("fs", NULL
);
4428 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
4434 void put_mnt_ns(struct mnt_namespace
*ns
)
4436 if (!refcount_dec_and_test(&ns
->ns
.count
))
4438 drop_collected_mounts(&ns
->root
->mnt
);
4442 struct vfsmount
*kern_mount(struct file_system_type
*type
)
4444 struct vfsmount
*mnt
;
4445 mnt
= vfs_kern_mount(type
, SB_KERNMOUNT
, type
->name
, NULL
);
4448 * it is a longterm mount, don't release mnt until
4449 * we unmount before file sys is unregistered
4451 real_mount(mnt
)->mnt_ns
= MNT_NS_INTERNAL
;
4455 EXPORT_SYMBOL_GPL(kern_mount
);
4457 void kern_unmount(struct vfsmount
*mnt
)
4459 /* release long term mount so mount point can be released */
4460 if (!IS_ERR_OR_NULL(mnt
)) {
4461 real_mount(mnt
)->mnt_ns
= NULL
;
4462 synchronize_rcu(); /* yecchhh... */
4466 EXPORT_SYMBOL(kern_unmount
);
4468 void kern_unmount_array(struct vfsmount
*mnt
[], unsigned int num
)
4472 for (i
= 0; i
< num
; i
++)
4474 real_mount(mnt
[i
])->mnt_ns
= NULL
;
4475 synchronize_rcu_expedited();
4476 for (i
= 0; i
< num
; i
++)
4479 EXPORT_SYMBOL(kern_unmount_array
);
4481 bool our_mnt(struct vfsmount
*mnt
)
4483 return check_mnt(real_mount(mnt
));
4486 bool current_chrooted(void)
4488 /* Does the current process have a non-standard root */
4489 struct path ns_root
;
4490 struct path fs_root
;
4493 /* Find the namespace root */
4494 ns_root
.mnt
= ¤t
->nsproxy
->mnt_ns
->root
->mnt
;
4495 ns_root
.dentry
= ns_root
.mnt
->mnt_root
;
4497 while (d_mountpoint(ns_root
.dentry
) && follow_down_one(&ns_root
))
4500 get_fs_root(current
->fs
, &fs_root
);
4502 chrooted
= !path_equal(&fs_root
, &ns_root
);
4510 static bool mnt_already_visible(struct mnt_namespace
*ns
,
4511 const struct super_block
*sb
,
4514 int new_flags
= *new_mnt_flags
;
4516 bool visible
= false;
4518 down_read(&namespace_sem
);
4520 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
4521 struct mount
*child
;
4524 if (mnt_is_cursor(mnt
))
4527 if (mnt
->mnt
.mnt_sb
->s_type
!= sb
->s_type
)
4530 /* This mount is not fully visible if it's root directory
4531 * is not the root directory of the filesystem.
4533 if (mnt
->mnt
.mnt_root
!= mnt
->mnt
.mnt_sb
->s_root
)
4536 /* A local view of the mount flags */
4537 mnt_flags
= mnt
->mnt
.mnt_flags
;
4539 /* Don't miss readonly hidden in the superblock flags */
4540 if (sb_rdonly(mnt
->mnt
.mnt_sb
))
4541 mnt_flags
|= MNT_LOCK_READONLY
;
4543 /* Verify the mount flags are equal to or more permissive
4544 * than the proposed new mount.
4546 if ((mnt_flags
& MNT_LOCK_READONLY
) &&
4547 !(new_flags
& MNT_READONLY
))
4549 if ((mnt_flags
& MNT_LOCK_ATIME
) &&
4550 ((mnt_flags
& MNT_ATIME_MASK
) != (new_flags
& MNT_ATIME_MASK
)))
4553 /* This mount is not fully visible if there are any
4554 * locked child mounts that cover anything except for
4555 * empty directories.
4557 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
4558 struct inode
*inode
= child
->mnt_mountpoint
->d_inode
;
4559 /* Only worry about locked mounts */
4560 if (!(child
->mnt
.mnt_flags
& MNT_LOCKED
))
4562 /* Is the directory permanetly empty? */
4563 if (!is_empty_dir_inode(inode
))
4566 /* Preserve the locked attributes */
4567 *new_mnt_flags
|= mnt_flags
& (MNT_LOCK_READONLY
| \
4575 up_read(&namespace_sem
);
4579 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
)
4581 const unsigned long required_iflags
= SB_I_NOEXEC
| SB_I_NODEV
;
4582 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
4583 unsigned long s_iflags
;
4585 if (ns
->user_ns
== &init_user_ns
)
4588 /* Can this filesystem be too revealing? */
4589 s_iflags
= sb
->s_iflags
;
4590 if (!(s_iflags
& SB_I_USERNS_VISIBLE
))
4593 if ((s_iflags
& required_iflags
) != required_iflags
) {
4594 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
4599 return !mnt_already_visible(ns
, sb
, new_mnt_flags
);
4602 bool mnt_may_suid(struct vfsmount
*mnt
)
4605 * Foreign mounts (accessed via fchdir or through /proc
4606 * symlinks) are always treated as if they are nosuid. This
4607 * prevents namespaces from trusting potentially unsafe
4608 * suid/sgid bits, file caps, or security labels that originate
4609 * in other namespaces.
4611 return !(mnt
->mnt_flags
& MNT_NOSUID
) && check_mnt(real_mount(mnt
)) &&
4612 current_in_userns(mnt
->mnt_sb
->s_user_ns
);
4615 static struct ns_common
*mntns_get(struct task_struct
*task
)
4617 struct ns_common
*ns
= NULL
;
4618 struct nsproxy
*nsproxy
;
4621 nsproxy
= task
->nsproxy
;
4623 ns
= &nsproxy
->mnt_ns
->ns
;
4624 get_mnt_ns(to_mnt_ns(ns
));
4631 static void mntns_put(struct ns_common
*ns
)
4633 put_mnt_ns(to_mnt_ns(ns
));
4636 static int mntns_install(struct nsset
*nsset
, struct ns_common
*ns
)
4638 struct nsproxy
*nsproxy
= nsset
->nsproxy
;
4639 struct fs_struct
*fs
= nsset
->fs
;
4640 struct mnt_namespace
*mnt_ns
= to_mnt_ns(ns
), *old_mnt_ns
;
4641 struct user_namespace
*user_ns
= nsset
->cred
->user_ns
;
4645 if (!ns_capable(mnt_ns
->user_ns
, CAP_SYS_ADMIN
) ||
4646 !ns_capable(user_ns
, CAP_SYS_CHROOT
) ||
4647 !ns_capable(user_ns
, CAP_SYS_ADMIN
))
4650 if (is_anon_ns(mnt_ns
))
4657 old_mnt_ns
= nsproxy
->mnt_ns
;
4658 nsproxy
->mnt_ns
= mnt_ns
;
4661 err
= vfs_path_lookup(mnt_ns
->root
->mnt
.mnt_root
, &mnt_ns
->root
->mnt
,
4662 "/", LOOKUP_DOWN
, &root
);
4664 /* revert to old namespace */
4665 nsproxy
->mnt_ns
= old_mnt_ns
;
4670 put_mnt_ns(old_mnt_ns
);
4672 /* Update the pwd and root */
4673 set_fs_pwd(fs
, &root
);
4674 set_fs_root(fs
, &root
);
4680 static struct user_namespace
*mntns_owner(struct ns_common
*ns
)
4682 return to_mnt_ns(ns
)->user_ns
;
4685 const struct proc_ns_operations mntns_operations
= {
4687 .type
= CLONE_NEWNS
,
4690 .install
= mntns_install
,
4691 .owner
= mntns_owner
,
4694 #ifdef CONFIG_SYSCTL
4695 static struct ctl_table fs_namespace_sysctls
[] = {
4697 .procname
= "mount-max",
4698 .data
= &sysctl_mount_max
,
4699 .maxlen
= sizeof(unsigned int),
4701 .proc_handler
= proc_dointvec_minmax
,
4702 .extra1
= SYSCTL_ONE
,
4707 static int __init
init_fs_namespace_sysctls(void)
4709 register_sysctl_init("fs", fs_namespace_sysctls
);
4712 fs_initcall(init_fs_namespace_sysctls
);
4714 #endif /* CONFIG_SYSCTL */