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 __ro_after_init
;
43 static unsigned int m_hash_shift __ro_after_init
;
44 static unsigned int mp_hash_mask __ro_after_init
;
45 static unsigned int mp_hash_shift __ro_after_init
;
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 __ro_after_init
;
72 static struct hlist_head
*mountpoint_hashtable __ro_after_init
;
73 static struct kmem_cache
*mnt_cache __ro_after_init
;
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
;
85 struct mnt_idmap
*mnt_idmap
;
89 struct kobject
*fs_kobj __ro_after_init
;
90 EXPORT_SYMBOL_GPL(fs_kobj
);
93 * vfsmount lock may be taken for read to prevent changes to the
94 * vfsmount hash, ie. during mountpoint lookups or walking back
97 * It should be taken for write in all cases where the vfsmount
98 * tree or hash is modified or when a vfsmount structure is modified.
100 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(mount_lock
);
102 static inline void lock_mount_hash(void)
104 write_seqlock(&mount_lock
);
107 static inline void unlock_mount_hash(void)
109 write_sequnlock(&mount_lock
);
112 static inline struct hlist_head
*m_hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
114 unsigned long tmp
= ((unsigned long)mnt
/ L1_CACHE_BYTES
);
115 tmp
+= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
116 tmp
= tmp
+ (tmp
>> m_hash_shift
);
117 return &mount_hashtable
[tmp
& m_hash_mask
];
120 static inline struct hlist_head
*mp_hash(struct dentry
*dentry
)
122 unsigned long tmp
= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
123 tmp
= tmp
+ (tmp
>> mp_hash_shift
);
124 return &mountpoint_hashtable
[tmp
& mp_hash_mask
];
127 static int mnt_alloc_id(struct mount
*mnt
)
129 int res
= ida_alloc(&mnt_id_ida
, GFP_KERNEL
);
137 static void mnt_free_id(struct mount
*mnt
)
139 ida_free(&mnt_id_ida
, mnt
->mnt_id
);
143 * Allocate a new peer group ID
145 static int mnt_alloc_group_id(struct mount
*mnt
)
147 int res
= ida_alloc_min(&mnt_group_ida
, 1, GFP_KERNEL
);
151 mnt
->mnt_group_id
= res
;
156 * Release a peer group ID
158 void mnt_release_group_id(struct mount
*mnt
)
160 ida_free(&mnt_group_ida
, mnt
->mnt_group_id
);
161 mnt
->mnt_group_id
= 0;
165 * vfsmount lock must be held for read
167 static inline void mnt_add_count(struct mount
*mnt
, int n
)
170 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, n
);
179 * vfsmount lock must be held for write
181 int mnt_get_count(struct mount
*mnt
)
187 for_each_possible_cpu(cpu
) {
188 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_count
;
193 return mnt
->mnt_count
;
197 static struct mount
*alloc_vfsmnt(const char *name
)
199 struct mount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
203 err
= mnt_alloc_id(mnt
);
208 mnt
->mnt_devname
= kstrdup_const(name
,
210 if (!mnt
->mnt_devname
)
215 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
217 goto out_free_devname
;
219 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
222 mnt
->mnt_writers
= 0;
225 INIT_HLIST_NODE(&mnt
->mnt_hash
);
226 INIT_LIST_HEAD(&mnt
->mnt_child
);
227 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
228 INIT_LIST_HEAD(&mnt
->mnt_list
);
229 INIT_LIST_HEAD(&mnt
->mnt_expire
);
230 INIT_LIST_HEAD(&mnt
->mnt_share
);
231 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
232 INIT_LIST_HEAD(&mnt
->mnt_slave
);
233 INIT_HLIST_NODE(&mnt
->mnt_mp_list
);
234 INIT_LIST_HEAD(&mnt
->mnt_umounting
);
235 INIT_HLIST_HEAD(&mnt
->mnt_stuck_children
);
236 mnt
->mnt
.mnt_idmap
= &nop_mnt_idmap
;
242 kfree_const(mnt
->mnt_devname
);
247 kmem_cache_free(mnt_cache
, mnt
);
252 * Most r/o checks on a fs are for operations that take
253 * discrete amounts of time, like a write() or unlink().
254 * We must keep track of when those operations start
255 * (for permission checks) and when they end, so that
256 * we can determine when writes are able to occur to
260 * __mnt_is_readonly: check whether a mount is read-only
261 * @mnt: the mount to check for its write status
263 * This shouldn't be used directly ouside of the VFS.
264 * It does not guarantee that the filesystem will stay
265 * r/w, just that it is right *now*. This can not and
266 * should not be used in place of IS_RDONLY(inode).
267 * mnt_want/drop_write() will _keep_ the filesystem
270 bool __mnt_is_readonly(struct vfsmount
*mnt
)
272 return (mnt
->mnt_flags
& MNT_READONLY
) || sb_rdonly(mnt
->mnt_sb
);
274 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
276 static inline void mnt_inc_writers(struct mount
*mnt
)
279 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
285 static inline void mnt_dec_writers(struct mount
*mnt
)
288 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
294 static unsigned int mnt_get_writers(struct mount
*mnt
)
297 unsigned int count
= 0;
300 for_each_possible_cpu(cpu
) {
301 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_writers
;
306 return mnt
->mnt_writers
;
310 static int mnt_is_readonly(struct vfsmount
*mnt
)
312 if (READ_ONCE(mnt
->mnt_sb
->s_readonly_remount
))
315 * The barrier pairs with the barrier in sb_start_ro_state_change()
316 * making sure if we don't see s_readonly_remount set yet, we also will
317 * not see any superblock / mount flag changes done by remount.
318 * It also pairs with the barrier in sb_end_ro_state_change()
319 * assuring that if we see s_readonly_remount already cleared, we will
320 * see the values of superblock / mount flags updated by remount.
323 return __mnt_is_readonly(mnt
);
327 * Most r/o & frozen checks on a fs are for operations that take discrete
328 * amounts of time, like a write() or unlink(). We must keep track of when
329 * those operations start (for permission checks) and when they end, so that we
330 * can determine when writes are able to occur to a filesystem.
333 * mnt_get_write_access - get write access to a mount without freeze protection
334 * @m: the mount on which to take a write
336 * This tells the low-level filesystem that a write is about to be performed to
337 * it, and makes sure that writes are allowed (mnt it read-write) before
338 * returning success. This operation does not protect against filesystem being
339 * frozen. When the write operation is finished, mnt_put_write_access() must be
340 * called. This is effectively a refcount.
342 int mnt_get_write_access(struct vfsmount
*m
)
344 struct mount
*mnt
= real_mount(m
);
348 mnt_inc_writers(mnt
);
350 * The store to mnt_inc_writers must be visible before we pass
351 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
352 * incremented count after it has set MNT_WRITE_HOLD.
355 might_lock(&mount_lock
.lock
);
356 while (READ_ONCE(mnt
->mnt
.mnt_flags
) & MNT_WRITE_HOLD
) {
357 if (!IS_ENABLED(CONFIG_PREEMPT_RT
)) {
361 * This prevents priority inversion, if the task
362 * setting MNT_WRITE_HOLD got preempted on a remote
363 * CPU, and it prevents life lock if the task setting
364 * MNT_WRITE_HOLD has a lower priority and is bound to
365 * the same CPU as the task that is spinning here.
374 * The barrier pairs with the barrier sb_start_ro_state_change() making
375 * sure that if we see MNT_WRITE_HOLD cleared, we will also see
376 * s_readonly_remount set (or even SB_RDONLY / MNT_READONLY flags) in
377 * mnt_is_readonly() and bail in case we are racing with remount
381 if (mnt_is_readonly(m
)) {
382 mnt_dec_writers(mnt
);
389 EXPORT_SYMBOL_GPL(mnt_get_write_access
);
392 * mnt_want_write - get write access to a mount
393 * @m: the mount on which to take a write
395 * This tells the low-level filesystem that a write is about to be performed to
396 * it, and makes sure that writes are allowed (mount is read-write, filesystem
397 * is not frozen) before returning success. When the write operation is
398 * finished, mnt_drop_write() must be called. This is effectively a refcount.
400 int mnt_want_write(struct vfsmount
*m
)
404 sb_start_write(m
->mnt_sb
);
405 ret
= mnt_get_write_access(m
);
407 sb_end_write(m
->mnt_sb
);
410 EXPORT_SYMBOL_GPL(mnt_want_write
);
413 * mnt_get_write_access_file - get write access to a file's mount
414 * @file: the file who's mount on which to take a write
416 * This is like mnt_get_write_access, but if @file is already open for write it
417 * skips incrementing mnt_writers (since the open file already has a reference)
418 * and instead only does the check for emergency r/o remounts. This must be
419 * paired with mnt_put_write_access_file.
421 int mnt_get_write_access_file(struct file
*file
)
423 if (file
->f_mode
& FMODE_WRITER
) {
425 * Superblock may have become readonly while there are still
426 * writable fd's, e.g. due to a fs error with errors=remount-ro
428 if (__mnt_is_readonly(file
->f_path
.mnt
))
432 return mnt_get_write_access(file
->f_path
.mnt
);
436 * mnt_want_write_file - get write access to a file's mount
437 * @file: the file who's mount on which to take a write
439 * This is like mnt_want_write, but if the file is already open for writing it
440 * skips incrementing mnt_writers (since the open file already has a reference)
441 * and instead only does the freeze protection and the check for emergency r/o
442 * remounts. This must be paired with mnt_drop_write_file.
444 int mnt_want_write_file(struct file
*file
)
448 sb_start_write(file_inode(file
)->i_sb
);
449 ret
= mnt_get_write_access_file(file
);
451 sb_end_write(file_inode(file
)->i_sb
);
454 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
457 * mnt_put_write_access - give up write access to a mount
458 * @mnt: the mount on which to give up write access
460 * Tells the low-level filesystem that we are done
461 * performing writes to it. Must be matched with
462 * mnt_get_write_access() call above.
464 void mnt_put_write_access(struct vfsmount
*mnt
)
467 mnt_dec_writers(real_mount(mnt
));
470 EXPORT_SYMBOL_GPL(mnt_put_write_access
);
473 * mnt_drop_write - give up write access to a mount
474 * @mnt: the mount on which to give up write access
476 * Tells the low-level filesystem that we are done performing writes to it and
477 * also allows filesystem to be frozen again. Must be matched with
478 * mnt_want_write() call above.
480 void mnt_drop_write(struct vfsmount
*mnt
)
482 mnt_put_write_access(mnt
);
483 sb_end_write(mnt
->mnt_sb
);
485 EXPORT_SYMBOL_GPL(mnt_drop_write
);
487 void mnt_put_write_access_file(struct file
*file
)
489 if (!(file
->f_mode
& FMODE_WRITER
))
490 mnt_put_write_access(file
->f_path
.mnt
);
493 void mnt_drop_write_file(struct file
*file
)
495 mnt_put_write_access_file(file
);
496 sb_end_write(file_inode(file
)->i_sb
);
498 EXPORT_SYMBOL(mnt_drop_write_file
);
501 * mnt_hold_writers - prevent write access to the given mount
502 * @mnt: mnt to prevent write access to
504 * Prevents write access to @mnt if there are no active writers for @mnt.
505 * This function needs to be called and return successfully before changing
506 * properties of @mnt that need to remain stable for callers with write access
509 * After this functions has been called successfully callers must pair it with
510 * a call to mnt_unhold_writers() in order to stop preventing write access to
513 * Context: This function expects lock_mount_hash() to be held serializing
514 * setting MNT_WRITE_HOLD.
515 * Return: On success 0 is returned.
516 * On error, -EBUSY is returned.
518 static inline int mnt_hold_writers(struct mount
*mnt
)
520 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
522 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
523 * should be visible before we do.
528 * With writers on hold, if this value is zero, then there are
529 * definitely no active writers (although held writers may subsequently
530 * increment the count, they'll have to wait, and decrement it after
531 * seeing MNT_READONLY).
533 * It is OK to have counter incremented on one CPU and decremented on
534 * another: the sum will add up correctly. The danger would be when we
535 * sum up each counter, if we read a counter before it is incremented,
536 * but then read another CPU's count which it has been subsequently
537 * decremented from -- we would see more decrements than we should.
538 * MNT_WRITE_HOLD protects against this scenario, because
539 * mnt_want_write first increments count, then smp_mb, then spins on
540 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
541 * we're counting up here.
543 if (mnt_get_writers(mnt
) > 0)
550 * mnt_unhold_writers - stop preventing write access to the given mount
551 * @mnt: mnt to stop preventing write access to
553 * Stop preventing write access to @mnt allowing callers to gain write access
556 * This function can only be called after a successful call to
557 * mnt_hold_writers().
559 * Context: This function expects lock_mount_hash() to be held.
561 static inline void mnt_unhold_writers(struct mount
*mnt
)
564 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
565 * that become unheld will see MNT_READONLY.
568 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
571 static int mnt_make_readonly(struct mount
*mnt
)
575 ret
= mnt_hold_writers(mnt
);
577 mnt
->mnt
.mnt_flags
|= MNT_READONLY
;
578 mnt_unhold_writers(mnt
);
582 int sb_prepare_remount_readonly(struct super_block
*sb
)
587 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
588 if (atomic_long_read(&sb
->s_remove_count
))
592 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
593 if (!(mnt
->mnt
.mnt_flags
& MNT_READONLY
)) {
594 err
= mnt_hold_writers(mnt
);
599 if (!err
&& atomic_long_read(&sb
->s_remove_count
))
603 sb_start_ro_state_change(sb
);
604 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
605 if (mnt
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
606 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
613 static void free_vfsmnt(struct mount
*mnt
)
615 mnt_idmap_put(mnt_idmap(&mnt
->mnt
));
616 kfree_const(mnt
->mnt_devname
);
618 free_percpu(mnt
->mnt_pcp
);
620 kmem_cache_free(mnt_cache
, mnt
);
623 static void delayed_free_vfsmnt(struct rcu_head
*head
)
625 free_vfsmnt(container_of(head
, struct mount
, mnt_rcu
));
628 /* call under rcu_read_lock */
629 int __legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
632 if (read_seqretry(&mount_lock
, seq
))
636 mnt
= real_mount(bastard
);
637 mnt_add_count(mnt
, 1);
638 smp_mb(); // see mntput_no_expire()
639 if (likely(!read_seqretry(&mount_lock
, seq
)))
641 if (bastard
->mnt_flags
& MNT_SYNC_UMOUNT
) {
642 mnt_add_count(mnt
, -1);
646 if (unlikely(bastard
->mnt_flags
& MNT_DOOMED
)) {
647 mnt_add_count(mnt
, -1);
652 /* caller will mntput() */
656 /* call under rcu_read_lock */
657 static bool legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
659 int res
= __legitimize_mnt(bastard
, seq
);
662 if (unlikely(res
< 0)) {
671 * __lookup_mnt - find first child mount
673 * @dentry: mountpoint
675 * If @mnt has a child mount @c mounted @dentry find and return it.
677 * Note that the child mount @c need not be unique. There are cases
678 * where shadow mounts are created. For example, during mount
679 * propagation when a source mount @mnt whose root got overmounted by a
680 * mount @o after path lookup but before @namespace_sem could be
681 * acquired gets copied and propagated. So @mnt gets copied including
682 * @o. When @mnt is propagated to a destination mount @d that already
683 * has another mount @n mounted at the same mountpoint then the source
684 * mount @mnt will be tucked beneath @n, i.e., @n will be mounted on
685 * @mnt and @mnt mounted on @d. Now both @n and @o are mounted at @mnt
688 * Return: The first child of @mnt mounted @dentry or NULL.
690 struct mount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
692 struct hlist_head
*head
= m_hash(mnt
, dentry
);
695 hlist_for_each_entry_rcu(p
, head
, mnt_hash
)
696 if (&p
->mnt_parent
->mnt
== mnt
&& p
->mnt_mountpoint
== dentry
)
702 * lookup_mnt - Return the first child mount mounted at path
704 * "First" means first mounted chronologically. If you create the
707 * mount /dev/sda1 /mnt
708 * mount /dev/sda2 /mnt
709 * mount /dev/sda3 /mnt
711 * Then lookup_mnt() on the base /mnt dentry in the root mount will
712 * return successively the root dentry and vfsmount of /dev/sda1, then
713 * /dev/sda2, then /dev/sda3, then NULL.
715 * lookup_mnt takes a reference to the found vfsmount.
717 struct vfsmount
*lookup_mnt(const struct path
*path
)
719 struct mount
*child_mnt
;
725 seq
= read_seqbegin(&mount_lock
);
726 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
);
727 m
= child_mnt
? &child_mnt
->mnt
: NULL
;
728 } while (!legitimize_mnt(m
, seq
));
733 static inline void lock_ns_list(struct mnt_namespace
*ns
)
735 spin_lock(&ns
->ns_lock
);
738 static inline void unlock_ns_list(struct mnt_namespace
*ns
)
740 spin_unlock(&ns
->ns_lock
);
743 static inline bool mnt_is_cursor(struct mount
*mnt
)
745 return mnt
->mnt
.mnt_flags
& MNT_CURSOR
;
749 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
750 * current mount namespace.
752 * The common case is dentries are not mountpoints at all and that
753 * test is handled inline. For the slow case when we are actually
754 * dealing with a mountpoint of some kind, walk through all of the
755 * mounts in the current mount namespace and test to see if the dentry
758 * The mount_hashtable is not usable in the context because we
759 * need to identify all mounts that may be in the current mount
760 * namespace not just a mount that happens to have some specified
763 bool __is_local_mountpoint(struct dentry
*dentry
)
765 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
767 bool is_covered
= false;
769 down_read(&namespace_sem
);
771 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
772 if (mnt_is_cursor(mnt
))
774 is_covered
= (mnt
->mnt_mountpoint
== dentry
);
779 up_read(&namespace_sem
);
784 static struct mountpoint
*lookup_mountpoint(struct dentry
*dentry
)
786 struct hlist_head
*chain
= mp_hash(dentry
);
787 struct mountpoint
*mp
;
789 hlist_for_each_entry(mp
, chain
, m_hash
) {
790 if (mp
->m_dentry
== dentry
) {
798 static struct mountpoint
*get_mountpoint(struct dentry
*dentry
)
800 struct mountpoint
*mp
, *new = NULL
;
803 if (d_mountpoint(dentry
)) {
804 /* might be worth a WARN_ON() */
805 if (d_unlinked(dentry
))
806 return ERR_PTR(-ENOENT
);
808 read_seqlock_excl(&mount_lock
);
809 mp
= lookup_mountpoint(dentry
);
810 read_sequnlock_excl(&mount_lock
);
816 new = kmalloc(sizeof(struct mountpoint
), GFP_KERNEL
);
818 return ERR_PTR(-ENOMEM
);
821 /* Exactly one processes may set d_mounted */
822 ret
= d_set_mounted(dentry
);
824 /* Someone else set d_mounted? */
828 /* The dentry is not available as a mountpoint? */
833 /* Add the new mountpoint to the hash table */
834 read_seqlock_excl(&mount_lock
);
835 new->m_dentry
= dget(dentry
);
837 hlist_add_head(&new->m_hash
, mp_hash(dentry
));
838 INIT_HLIST_HEAD(&new->m_list
);
839 read_sequnlock_excl(&mount_lock
);
849 * vfsmount lock must be held. Additionally, the caller is responsible
850 * for serializing calls for given disposal list.
852 static void __put_mountpoint(struct mountpoint
*mp
, struct list_head
*list
)
854 if (!--mp
->m_count
) {
855 struct dentry
*dentry
= mp
->m_dentry
;
856 BUG_ON(!hlist_empty(&mp
->m_list
));
857 spin_lock(&dentry
->d_lock
);
858 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
859 spin_unlock(&dentry
->d_lock
);
860 dput_to_list(dentry
, list
);
861 hlist_del(&mp
->m_hash
);
866 /* called with namespace_lock and vfsmount lock */
867 static void put_mountpoint(struct mountpoint
*mp
)
869 __put_mountpoint(mp
, &ex_mountpoints
);
872 static inline int check_mnt(struct mount
*mnt
)
874 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
878 * vfsmount lock must be held for write
880 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
884 wake_up_interruptible(&ns
->poll
);
889 * vfsmount lock must be held for write
891 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
893 if (ns
&& ns
->event
!= event
) {
895 wake_up_interruptible(&ns
->poll
);
900 * vfsmount lock must be held for write
902 static struct mountpoint
*unhash_mnt(struct mount
*mnt
)
904 struct mountpoint
*mp
;
905 mnt
->mnt_parent
= mnt
;
906 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
907 list_del_init(&mnt
->mnt_child
);
908 hlist_del_init_rcu(&mnt
->mnt_hash
);
909 hlist_del_init(&mnt
->mnt_mp_list
);
916 * vfsmount lock must be held for write
918 static void umount_mnt(struct mount
*mnt
)
920 put_mountpoint(unhash_mnt(mnt
));
924 * vfsmount lock must be held for write
926 void mnt_set_mountpoint(struct mount
*mnt
,
927 struct mountpoint
*mp
,
928 struct mount
*child_mnt
)
931 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
932 child_mnt
->mnt_mountpoint
= mp
->m_dentry
;
933 child_mnt
->mnt_parent
= mnt
;
934 child_mnt
->mnt_mp
= mp
;
935 hlist_add_head(&child_mnt
->mnt_mp_list
, &mp
->m_list
);
939 * mnt_set_mountpoint_beneath - mount a mount beneath another one
941 * @new_parent: the source mount
942 * @top_mnt: the mount beneath which @new_parent is mounted
943 * @new_mp: the new mountpoint of @top_mnt on @new_parent
945 * Remove @top_mnt from its current mountpoint @top_mnt->mnt_mp and
946 * parent @top_mnt->mnt_parent and mount it on top of @new_parent at
947 * @new_mp. And mount @new_parent on the old parent and old
948 * mountpoint of @top_mnt.
950 * Context: This function expects namespace_lock() and lock_mount_hash()
951 * to have been acquired in that order.
953 static void mnt_set_mountpoint_beneath(struct mount
*new_parent
,
954 struct mount
*top_mnt
,
955 struct mountpoint
*new_mp
)
957 struct mount
*old_top_parent
= top_mnt
->mnt_parent
;
958 struct mountpoint
*old_top_mp
= top_mnt
->mnt_mp
;
960 mnt_set_mountpoint(old_top_parent
, old_top_mp
, new_parent
);
961 mnt_change_mountpoint(new_parent
, new_mp
, top_mnt
);
965 static void __attach_mnt(struct mount
*mnt
, struct mount
*parent
)
967 hlist_add_head_rcu(&mnt
->mnt_hash
,
968 m_hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
969 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
973 * attach_mnt - mount a mount, attach to @mount_hashtable and parent's
974 * list of child mounts
975 * @parent: the parent
976 * @mnt: the new mount
977 * @mp: the new mountpoint
978 * @beneath: whether to mount @mnt beneath or on top of @parent
980 * If @beneath is false, mount @mnt at @mp on @parent. Then attach @mnt
981 * to @parent's child mount list and to @mount_hashtable.
983 * If @beneath is true, remove @mnt from its current parent and
984 * mountpoint and mount it on @mp on @parent, and mount @parent on the
985 * old parent and old mountpoint of @mnt. Finally, attach @parent to
986 * @mnt_hashtable and @parent->mnt_parent->mnt_mounts.
988 * Note, when __attach_mnt() is called @mnt->mnt_parent already points
989 * to the correct parent.
991 * Context: This function expects namespace_lock() and lock_mount_hash()
992 * to have been acquired in that order.
994 static void attach_mnt(struct mount
*mnt
, struct mount
*parent
,
995 struct mountpoint
*mp
, bool beneath
)
998 mnt_set_mountpoint_beneath(mnt
, parent
, mp
);
1000 mnt_set_mountpoint(parent
, mp
, mnt
);
1002 * Note, @mnt->mnt_parent has to be used. If @mnt was mounted
1003 * beneath @parent then @mnt will need to be attached to
1004 * @parent's old parent, not @parent. IOW, @mnt->mnt_parent
1005 * isn't the same mount as @parent.
1007 __attach_mnt(mnt
, mnt
->mnt_parent
);
1010 void mnt_change_mountpoint(struct mount
*parent
, struct mountpoint
*mp
, struct mount
*mnt
)
1012 struct mountpoint
*old_mp
= mnt
->mnt_mp
;
1013 struct mount
*old_parent
= mnt
->mnt_parent
;
1015 list_del_init(&mnt
->mnt_child
);
1016 hlist_del_init(&mnt
->mnt_mp_list
);
1017 hlist_del_init_rcu(&mnt
->mnt_hash
);
1019 attach_mnt(mnt
, parent
, mp
, false);
1021 put_mountpoint(old_mp
);
1022 mnt_add_count(old_parent
, -1);
1026 * vfsmount lock must be held for write
1028 static void commit_tree(struct mount
*mnt
)
1030 struct mount
*parent
= mnt
->mnt_parent
;
1033 struct mnt_namespace
*n
= parent
->mnt_ns
;
1035 BUG_ON(parent
== mnt
);
1037 list_add_tail(&head
, &mnt
->mnt_list
);
1038 list_for_each_entry(m
, &head
, mnt_list
)
1041 list_splice(&head
, n
->list
.prev
);
1043 n
->mounts
+= n
->pending_mounts
;
1044 n
->pending_mounts
= 0;
1046 __attach_mnt(mnt
, parent
);
1047 touch_mnt_namespace(n
);
1050 static struct mount
*next_mnt(struct mount
*p
, struct mount
*root
)
1052 struct list_head
*next
= p
->mnt_mounts
.next
;
1053 if (next
== &p
->mnt_mounts
) {
1057 next
= p
->mnt_child
.next
;
1058 if (next
!= &p
->mnt_parent
->mnt_mounts
)
1063 return list_entry(next
, struct mount
, mnt_child
);
1066 static struct mount
*skip_mnt_tree(struct mount
*p
)
1068 struct list_head
*prev
= p
->mnt_mounts
.prev
;
1069 while (prev
!= &p
->mnt_mounts
) {
1070 p
= list_entry(prev
, struct mount
, mnt_child
);
1071 prev
= p
->mnt_mounts
.prev
;
1077 * vfs_create_mount - Create a mount for a configured superblock
1078 * @fc: The configuration context with the superblock attached
1080 * Create a mount to an already configured superblock. If necessary, the
1081 * caller should invoke vfs_get_tree() before calling this.
1083 * Note that this does not attach the mount to anything.
1085 struct vfsmount
*vfs_create_mount(struct fs_context
*fc
)
1090 return ERR_PTR(-EINVAL
);
1092 mnt
= alloc_vfsmnt(fc
->source
?: "none");
1094 return ERR_PTR(-ENOMEM
);
1096 if (fc
->sb_flags
& SB_KERNMOUNT
)
1097 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
1099 atomic_inc(&fc
->root
->d_sb
->s_active
);
1100 mnt
->mnt
.mnt_sb
= fc
->root
->d_sb
;
1101 mnt
->mnt
.mnt_root
= dget(fc
->root
);
1102 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1103 mnt
->mnt_parent
= mnt
;
1106 list_add_tail(&mnt
->mnt_instance
, &mnt
->mnt
.mnt_sb
->s_mounts
);
1107 unlock_mount_hash();
1110 EXPORT_SYMBOL(vfs_create_mount
);
1112 struct vfsmount
*fc_mount(struct fs_context
*fc
)
1114 int err
= vfs_get_tree(fc
);
1116 up_write(&fc
->root
->d_sb
->s_umount
);
1117 return vfs_create_mount(fc
);
1119 return ERR_PTR(err
);
1121 EXPORT_SYMBOL(fc_mount
);
1123 struct vfsmount
*vfs_kern_mount(struct file_system_type
*type
,
1124 int flags
, const char *name
,
1127 struct fs_context
*fc
;
1128 struct vfsmount
*mnt
;
1132 return ERR_PTR(-EINVAL
);
1134 fc
= fs_context_for_mount(type
, flags
);
1136 return ERR_CAST(fc
);
1139 ret
= vfs_parse_fs_string(fc
, "source",
1140 name
, strlen(name
));
1142 ret
= parse_monolithic_mount_data(fc
, data
);
1151 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
1154 vfs_submount(const struct dentry
*mountpoint
, struct file_system_type
*type
,
1155 const char *name
, void *data
)
1157 /* Until it is worked out how to pass the user namespace
1158 * through from the parent mount to the submount don't support
1159 * unprivileged mounts with submounts.
1161 if (mountpoint
->d_sb
->s_user_ns
!= &init_user_ns
)
1162 return ERR_PTR(-EPERM
);
1164 return vfs_kern_mount(type
, SB_SUBMOUNT
, name
, data
);
1166 EXPORT_SYMBOL_GPL(vfs_submount
);
1168 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
1171 struct super_block
*sb
= old
->mnt
.mnt_sb
;
1175 mnt
= alloc_vfsmnt(old
->mnt_devname
);
1177 return ERR_PTR(-ENOMEM
);
1179 if (flag
& (CL_SLAVE
| CL_PRIVATE
| CL_SHARED_TO_SLAVE
))
1180 mnt
->mnt_group_id
= 0; /* not a peer of original */
1182 mnt
->mnt_group_id
= old
->mnt_group_id
;
1184 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
1185 err
= mnt_alloc_group_id(mnt
);
1190 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
;
1191 mnt
->mnt
.mnt_flags
&= ~(MNT_WRITE_HOLD
|MNT_MARKED
|MNT_INTERNAL
);
1193 atomic_inc(&sb
->s_active
);
1194 mnt
->mnt
.mnt_idmap
= mnt_idmap_get(mnt_idmap(&old
->mnt
));
1196 mnt
->mnt
.mnt_sb
= sb
;
1197 mnt
->mnt
.mnt_root
= dget(root
);
1198 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1199 mnt
->mnt_parent
= mnt
;
1201 list_add_tail(&mnt
->mnt_instance
, &sb
->s_mounts
);
1202 unlock_mount_hash();
1204 if ((flag
& CL_SLAVE
) ||
1205 ((flag
& CL_SHARED_TO_SLAVE
) && IS_MNT_SHARED(old
))) {
1206 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
1207 mnt
->mnt_master
= old
;
1208 CLEAR_MNT_SHARED(mnt
);
1209 } else if (!(flag
& CL_PRIVATE
)) {
1210 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
1211 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
1212 if (IS_MNT_SLAVE(old
))
1213 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
1214 mnt
->mnt_master
= old
->mnt_master
;
1216 CLEAR_MNT_SHARED(mnt
);
1218 if (flag
& CL_MAKE_SHARED
)
1219 set_mnt_shared(mnt
);
1221 /* stick the duplicate mount on the same expiry list
1222 * as the original if that was on one */
1223 if (flag
& CL_EXPIRE
) {
1224 if (!list_empty(&old
->mnt_expire
))
1225 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
1233 return ERR_PTR(err
);
1236 static void cleanup_mnt(struct mount
*mnt
)
1238 struct hlist_node
*p
;
1241 * The warning here probably indicates that somebody messed
1242 * up a mnt_want/drop_write() pair. If this happens, the
1243 * filesystem was probably unable to make r/w->r/o transitions.
1244 * The locking used to deal with mnt_count decrement provides barriers,
1245 * so mnt_get_writers() below is safe.
1247 WARN_ON(mnt_get_writers(mnt
));
1248 if (unlikely(mnt
->mnt_pins
.first
))
1250 hlist_for_each_entry_safe(m
, p
, &mnt
->mnt_stuck_children
, mnt_umount
) {
1251 hlist_del(&m
->mnt_umount
);
1254 fsnotify_vfsmount_delete(&mnt
->mnt
);
1255 dput(mnt
->mnt
.mnt_root
);
1256 deactivate_super(mnt
->mnt
.mnt_sb
);
1258 call_rcu(&mnt
->mnt_rcu
, delayed_free_vfsmnt
);
1261 static void __cleanup_mnt(struct rcu_head
*head
)
1263 cleanup_mnt(container_of(head
, struct mount
, mnt_rcu
));
1266 static LLIST_HEAD(delayed_mntput_list
);
1267 static void delayed_mntput(struct work_struct
*unused
)
1269 struct llist_node
*node
= llist_del_all(&delayed_mntput_list
);
1270 struct mount
*m
, *t
;
1272 llist_for_each_entry_safe(m
, t
, node
, mnt_llist
)
1275 static DECLARE_DELAYED_WORK(delayed_mntput_work
, delayed_mntput
);
1277 static void mntput_no_expire(struct mount
*mnt
)
1283 if (likely(READ_ONCE(mnt
->mnt_ns
))) {
1285 * Since we don't do lock_mount_hash() here,
1286 * ->mnt_ns can change under us. However, if it's
1287 * non-NULL, then there's a reference that won't
1288 * be dropped until after an RCU delay done after
1289 * turning ->mnt_ns NULL. So if we observe it
1290 * non-NULL under rcu_read_lock(), the reference
1291 * we are dropping is not the final one.
1293 mnt_add_count(mnt
, -1);
1299 * make sure that if __legitimize_mnt() has not seen us grab
1300 * mount_lock, we'll see their refcount increment here.
1303 mnt_add_count(mnt
, -1);
1304 count
= mnt_get_count(mnt
);
1308 unlock_mount_hash();
1311 if (unlikely(mnt
->mnt
.mnt_flags
& MNT_DOOMED
)) {
1313 unlock_mount_hash();
1316 mnt
->mnt
.mnt_flags
|= MNT_DOOMED
;
1319 list_del(&mnt
->mnt_instance
);
1321 if (unlikely(!list_empty(&mnt
->mnt_mounts
))) {
1322 struct mount
*p
, *tmp
;
1323 list_for_each_entry_safe(p
, tmp
, &mnt
->mnt_mounts
, mnt_child
) {
1324 __put_mountpoint(unhash_mnt(p
), &list
);
1325 hlist_add_head(&p
->mnt_umount
, &mnt
->mnt_stuck_children
);
1328 unlock_mount_hash();
1329 shrink_dentry_list(&list
);
1331 if (likely(!(mnt
->mnt
.mnt_flags
& MNT_INTERNAL
))) {
1332 struct task_struct
*task
= current
;
1333 if (likely(!(task
->flags
& PF_KTHREAD
))) {
1334 init_task_work(&mnt
->mnt_rcu
, __cleanup_mnt
);
1335 if (!task_work_add(task
, &mnt
->mnt_rcu
, TWA_RESUME
))
1338 if (llist_add(&mnt
->mnt_llist
, &delayed_mntput_list
))
1339 schedule_delayed_work(&delayed_mntput_work
, 1);
1345 void mntput(struct vfsmount
*mnt
)
1348 struct mount
*m
= real_mount(mnt
);
1349 /* avoid cacheline pingpong */
1350 if (unlikely(m
->mnt_expiry_mark
))
1351 WRITE_ONCE(m
->mnt_expiry_mark
, 0);
1352 mntput_no_expire(m
);
1355 EXPORT_SYMBOL(mntput
);
1357 struct vfsmount
*mntget(struct vfsmount
*mnt
)
1360 mnt_add_count(real_mount(mnt
), 1);
1363 EXPORT_SYMBOL(mntget
);
1366 * Make a mount point inaccessible to new lookups.
1367 * Because there may still be current users, the caller MUST WAIT
1368 * for an RCU grace period before destroying the mount point.
1370 void mnt_make_shortterm(struct vfsmount
*mnt
)
1373 real_mount(mnt
)->mnt_ns
= NULL
;
1377 * path_is_mountpoint() - Check if path is a mount in the current namespace.
1378 * @path: path to check
1380 * d_mountpoint() can only be used reliably to establish if a dentry is
1381 * not mounted in any namespace and that common case is handled inline.
1382 * d_mountpoint() isn't aware of the possibility there may be multiple
1383 * mounts using a given dentry in a different namespace. This function
1384 * checks if the passed in path is a mountpoint rather than the dentry
1387 bool path_is_mountpoint(const struct path
*path
)
1392 if (!d_mountpoint(path
->dentry
))
1397 seq
= read_seqbegin(&mount_lock
);
1398 res
= __path_is_mountpoint(path
);
1399 } while (read_seqretry(&mount_lock
, seq
));
1404 EXPORT_SYMBOL(path_is_mountpoint
);
1406 struct vfsmount
*mnt_clone_internal(const struct path
*path
)
1409 p
= clone_mnt(real_mount(path
->mnt
), path
->dentry
, CL_PRIVATE
);
1412 p
->mnt
.mnt_flags
|= MNT_INTERNAL
;
1416 #ifdef CONFIG_PROC_FS
1417 static struct mount
*mnt_list_next(struct mnt_namespace
*ns
,
1418 struct list_head
*p
)
1420 struct mount
*mnt
, *ret
= NULL
;
1423 list_for_each_continue(p
, &ns
->list
) {
1424 mnt
= list_entry(p
, typeof(*mnt
), mnt_list
);
1425 if (!mnt_is_cursor(mnt
)) {
1435 /* iterator; we want it to have access to namespace_sem, thus here... */
1436 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
1438 struct proc_mounts
*p
= m
->private;
1439 struct list_head
*prev
;
1441 down_read(&namespace_sem
);
1443 prev
= &p
->ns
->list
;
1445 prev
= &p
->cursor
.mnt_list
;
1447 /* Read after we'd reached the end? */
1448 if (list_empty(prev
))
1452 return mnt_list_next(p
->ns
, prev
);
1455 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
1457 struct proc_mounts
*p
= m
->private;
1458 struct mount
*mnt
= v
;
1461 return mnt_list_next(p
->ns
, &mnt
->mnt_list
);
1464 static void m_stop(struct seq_file
*m
, void *v
)
1466 struct proc_mounts
*p
= m
->private;
1467 struct mount
*mnt
= v
;
1469 lock_ns_list(p
->ns
);
1471 list_move_tail(&p
->cursor
.mnt_list
, &mnt
->mnt_list
);
1473 list_del_init(&p
->cursor
.mnt_list
);
1474 unlock_ns_list(p
->ns
);
1475 up_read(&namespace_sem
);
1478 static int m_show(struct seq_file
*m
, void *v
)
1480 struct proc_mounts
*p
= m
->private;
1481 struct mount
*r
= v
;
1482 return p
->show(m
, &r
->mnt
);
1485 const struct seq_operations mounts_op
= {
1492 void mnt_cursor_del(struct mnt_namespace
*ns
, struct mount
*cursor
)
1494 down_read(&namespace_sem
);
1496 list_del(&cursor
->mnt_list
);
1498 up_read(&namespace_sem
);
1500 #endif /* CONFIG_PROC_FS */
1503 * may_umount_tree - check if a mount tree is busy
1504 * @m: root of mount tree
1506 * This is called to check if a tree of mounts has any
1507 * open files, pwds, chroots or sub mounts that are
1510 int may_umount_tree(struct vfsmount
*m
)
1512 struct mount
*mnt
= real_mount(m
);
1513 int actual_refs
= 0;
1514 int minimum_refs
= 0;
1518 /* write lock needed for mnt_get_count */
1520 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1521 actual_refs
+= mnt_get_count(p
);
1524 unlock_mount_hash();
1526 if (actual_refs
> minimum_refs
)
1532 EXPORT_SYMBOL(may_umount_tree
);
1535 * may_umount - check if a mount point is busy
1536 * @mnt: root of mount
1538 * This is called to check if a mount point has any
1539 * open files, pwds, chroots or sub mounts. If the
1540 * mount has sub mounts this will return busy
1541 * regardless of whether the sub mounts are busy.
1543 * Doesn't take quota and stuff into account. IOW, in some cases it will
1544 * give false negatives. The main reason why it's here is that we need
1545 * a non-destructive way to look for easily umountable filesystems.
1547 int may_umount(struct vfsmount
*mnt
)
1550 down_read(&namespace_sem
);
1552 if (propagate_mount_busy(real_mount(mnt
), 2))
1554 unlock_mount_hash();
1555 up_read(&namespace_sem
);
1559 EXPORT_SYMBOL(may_umount
);
1561 static void namespace_unlock(void)
1563 struct hlist_head head
;
1564 struct hlist_node
*p
;
1568 hlist_move_list(&unmounted
, &head
);
1569 list_splice_init(&ex_mountpoints
, &list
);
1571 up_write(&namespace_sem
);
1573 shrink_dentry_list(&list
);
1575 if (likely(hlist_empty(&head
)))
1578 synchronize_rcu_expedited();
1580 hlist_for_each_entry_safe(m
, p
, &head
, mnt_umount
) {
1581 hlist_del(&m
->mnt_umount
);
1586 static inline void namespace_lock(void)
1588 down_write(&namespace_sem
);
1591 enum umount_tree_flags
{
1593 UMOUNT_PROPAGATE
= 2,
1594 UMOUNT_CONNECTED
= 4,
1597 static bool disconnect_mount(struct mount
*mnt
, enum umount_tree_flags how
)
1599 /* Leaving mounts connected is only valid for lazy umounts */
1600 if (how
& UMOUNT_SYNC
)
1603 /* A mount without a parent has nothing to be connected to */
1604 if (!mnt_has_parent(mnt
))
1607 /* Because the reference counting rules change when mounts are
1608 * unmounted and connected, umounted mounts may not be
1609 * connected to mounted mounts.
1611 if (!(mnt
->mnt_parent
->mnt
.mnt_flags
& MNT_UMOUNT
))
1614 /* Has it been requested that the mount remain connected? */
1615 if (how
& UMOUNT_CONNECTED
)
1618 /* Is the mount locked such that it needs to remain connected? */
1619 if (IS_MNT_LOCKED(mnt
))
1622 /* By default disconnect the mount */
1627 * mount_lock must be held
1628 * namespace_sem must be held for write
1630 static void umount_tree(struct mount
*mnt
, enum umount_tree_flags how
)
1632 LIST_HEAD(tmp_list
);
1635 if (how
& UMOUNT_PROPAGATE
)
1636 propagate_mount_unlock(mnt
);
1638 /* Gather the mounts to umount */
1639 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1640 p
->mnt
.mnt_flags
|= MNT_UMOUNT
;
1641 list_move(&p
->mnt_list
, &tmp_list
);
1644 /* Hide the mounts from mnt_mounts */
1645 list_for_each_entry(p
, &tmp_list
, mnt_list
) {
1646 list_del_init(&p
->mnt_child
);
1649 /* Add propogated mounts to the tmp_list */
1650 if (how
& UMOUNT_PROPAGATE
)
1651 propagate_umount(&tmp_list
);
1653 while (!list_empty(&tmp_list
)) {
1654 struct mnt_namespace
*ns
;
1656 p
= list_first_entry(&tmp_list
, struct mount
, mnt_list
);
1657 list_del_init(&p
->mnt_expire
);
1658 list_del_init(&p
->mnt_list
);
1662 __touch_mnt_namespace(ns
);
1665 if (how
& UMOUNT_SYNC
)
1666 p
->mnt
.mnt_flags
|= MNT_SYNC_UMOUNT
;
1668 disconnect
= disconnect_mount(p
, how
);
1669 if (mnt_has_parent(p
)) {
1670 mnt_add_count(p
->mnt_parent
, -1);
1672 /* Don't forget about p */
1673 list_add_tail(&p
->mnt_child
, &p
->mnt_parent
->mnt_mounts
);
1678 change_mnt_propagation(p
, MS_PRIVATE
);
1680 hlist_add_head(&p
->mnt_umount
, &unmounted
);
1684 static void shrink_submounts(struct mount
*mnt
);
1686 static int do_umount_root(struct super_block
*sb
)
1690 down_write(&sb
->s_umount
);
1691 if (!sb_rdonly(sb
)) {
1692 struct fs_context
*fc
;
1694 fc
= fs_context_for_reconfigure(sb
->s_root
, SB_RDONLY
,
1699 ret
= parse_monolithic_mount_data(fc
, NULL
);
1701 ret
= reconfigure_super(fc
);
1705 up_write(&sb
->s_umount
);
1709 static int do_umount(struct mount
*mnt
, int flags
)
1711 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1714 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1719 * Allow userspace to request a mountpoint be expired rather than
1720 * unmounting unconditionally. Unmount only happens if:
1721 * (1) the mark is already set (the mark is cleared by mntput())
1722 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1724 if (flags
& MNT_EXPIRE
) {
1725 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1726 flags
& (MNT_FORCE
| MNT_DETACH
))
1730 * probably don't strictly need the lock here if we examined
1731 * all race cases, but it's a slowpath.
1734 if (mnt_get_count(mnt
) != 2) {
1735 unlock_mount_hash();
1738 unlock_mount_hash();
1740 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1745 * If we may have to abort operations to get out of this
1746 * mount, and they will themselves hold resources we must
1747 * allow the fs to do things. In the Unix tradition of
1748 * 'Gee thats tricky lets do it in userspace' the umount_begin
1749 * might fail to complete on the first run through as other tasks
1750 * must return, and the like. Thats for the mount program to worry
1751 * about for the moment.
1754 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1755 sb
->s_op
->umount_begin(sb
);
1759 * No sense to grab the lock for this test, but test itself looks
1760 * somewhat bogus. Suggestions for better replacement?
1761 * Ho-hum... In principle, we might treat that as umount + switch
1762 * to rootfs. GC would eventually take care of the old vfsmount.
1763 * Actually it makes sense, especially if rootfs would contain a
1764 * /reboot - static binary that would close all descriptors and
1765 * call reboot(9). Then init(8) could umount root and exec /reboot.
1767 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1769 * Special case for "unmounting" root ...
1770 * we just try to remount it readonly.
1772 if (!ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
))
1774 return do_umount_root(sb
);
1780 /* Recheck MNT_LOCKED with the locks held */
1782 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
1786 if (flags
& MNT_DETACH
) {
1787 if (!list_empty(&mnt
->mnt_list
))
1788 umount_tree(mnt
, UMOUNT_PROPAGATE
);
1791 shrink_submounts(mnt
);
1793 if (!propagate_mount_busy(mnt
, 2)) {
1794 if (!list_empty(&mnt
->mnt_list
))
1795 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
1800 unlock_mount_hash();
1806 * __detach_mounts - lazily unmount all mounts on the specified dentry
1808 * During unlink, rmdir, and d_drop it is possible to loose the path
1809 * to an existing mountpoint, and wind up leaking the mount.
1810 * detach_mounts allows lazily unmounting those mounts instead of
1813 * The caller may hold dentry->d_inode->i_mutex.
1815 void __detach_mounts(struct dentry
*dentry
)
1817 struct mountpoint
*mp
;
1822 mp
= lookup_mountpoint(dentry
);
1827 while (!hlist_empty(&mp
->m_list
)) {
1828 mnt
= hlist_entry(mp
->m_list
.first
, struct mount
, mnt_mp_list
);
1829 if (mnt
->mnt
.mnt_flags
& MNT_UMOUNT
) {
1831 hlist_add_head(&mnt
->mnt_umount
, &unmounted
);
1833 else umount_tree(mnt
, UMOUNT_CONNECTED
);
1837 unlock_mount_hash();
1842 * Is the caller allowed to modify his namespace?
1844 bool may_mount(void)
1846 return ns_capable(current
->nsproxy
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
);
1850 * path_mounted - check whether path is mounted
1851 * @path: path to check
1853 * Determine whether @path refers to the root of a mount.
1855 * Return: true if @path is the root of a mount, false if not.
1857 static inline bool path_mounted(const struct path
*path
)
1859 return path
->mnt
->mnt_root
== path
->dentry
;
1862 static void warn_mandlock(void)
1864 pr_warn_once("=======================================================\n"
1865 "WARNING: The mand mount option has been deprecated and\n"
1866 " and is ignored by this kernel. Remove the mand\n"
1867 " option from the mount to silence this warning.\n"
1868 "=======================================================\n");
1871 static int can_umount(const struct path
*path
, int flags
)
1873 struct mount
*mnt
= real_mount(path
->mnt
);
1877 if (!path_mounted(path
))
1879 if (!check_mnt(mnt
))
1881 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
) /* Check optimistically */
1883 if (flags
& MNT_FORCE
&& !capable(CAP_SYS_ADMIN
))
1888 // caller is responsible for flags being sane
1889 int path_umount(struct path
*path
, int flags
)
1891 struct mount
*mnt
= real_mount(path
->mnt
);
1894 ret
= can_umount(path
, flags
);
1896 ret
= do_umount(mnt
, flags
);
1898 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1900 mntput_no_expire(mnt
);
1904 static int ksys_umount(char __user
*name
, int flags
)
1906 int lookup_flags
= LOOKUP_MOUNTPOINT
;
1910 // basic validity checks done first
1911 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1914 if (!(flags
& UMOUNT_NOFOLLOW
))
1915 lookup_flags
|= LOOKUP_FOLLOW
;
1916 ret
= user_path_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1919 return path_umount(&path
, flags
);
1922 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1924 return ksys_umount(name
, flags
);
1927 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1930 * The 2.0 compatible umount. No flags.
1932 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1934 return ksys_umount(name
, 0);
1939 static bool is_mnt_ns_file(struct dentry
*dentry
)
1941 /* Is this a proxy for a mount namespace? */
1942 return dentry
->d_op
== &ns_dentry_operations
&&
1943 dentry
->d_fsdata
== &mntns_operations
;
1946 static struct mnt_namespace
*to_mnt_ns(struct ns_common
*ns
)
1948 return container_of(ns
, struct mnt_namespace
, ns
);
1951 struct ns_common
*from_mnt_ns(struct mnt_namespace
*mnt
)
1956 static bool mnt_ns_loop(struct dentry
*dentry
)
1958 /* Could bind mounting the mount namespace inode cause a
1959 * mount namespace loop?
1961 struct mnt_namespace
*mnt_ns
;
1962 if (!is_mnt_ns_file(dentry
))
1965 mnt_ns
= to_mnt_ns(get_proc_ns(dentry
->d_inode
));
1966 return current
->nsproxy
->mnt_ns
->seq
>= mnt_ns
->seq
;
1969 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1972 struct mount
*res
, *p
, *q
, *r
, *parent
;
1974 if (!(flag
& CL_COPY_UNBINDABLE
) && IS_MNT_UNBINDABLE(mnt
))
1975 return ERR_PTR(-EINVAL
);
1977 if (!(flag
& CL_COPY_MNT_NS_FILE
) && is_mnt_ns_file(dentry
))
1978 return ERR_PTR(-EINVAL
);
1980 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1984 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1987 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1989 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1992 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1993 if (!(flag
& CL_COPY_UNBINDABLE
) &&
1994 IS_MNT_UNBINDABLE(s
)) {
1995 if (s
->mnt
.mnt_flags
& MNT_LOCKED
) {
1996 /* Both unbindable and locked. */
1997 q
= ERR_PTR(-EPERM
);
2000 s
= skip_mnt_tree(s
);
2004 if (!(flag
& CL_COPY_MNT_NS_FILE
) &&
2005 is_mnt_ns_file(s
->mnt
.mnt_root
)) {
2006 s
= skip_mnt_tree(s
);
2009 while (p
!= s
->mnt_parent
) {
2015 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
2019 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
2020 attach_mnt(q
, parent
, p
->mnt_mp
, false);
2021 unlock_mount_hash();
2028 umount_tree(res
, UMOUNT_SYNC
);
2029 unlock_mount_hash();
2034 /* Caller should check returned pointer for errors */
2036 struct vfsmount
*collect_mounts(const struct path
*path
)
2040 if (!check_mnt(real_mount(path
->mnt
)))
2041 tree
= ERR_PTR(-EINVAL
);
2043 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
2044 CL_COPY_ALL
| CL_PRIVATE
);
2047 return ERR_CAST(tree
);
2051 static void free_mnt_ns(struct mnt_namespace
*);
2052 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*, bool);
2054 void dissolve_on_fput(struct vfsmount
*mnt
)
2056 struct mnt_namespace
*ns
;
2059 ns
= real_mount(mnt
)->mnt_ns
;
2062 umount_tree(real_mount(mnt
), UMOUNT_CONNECTED
);
2066 unlock_mount_hash();
2072 void drop_collected_mounts(struct vfsmount
*mnt
)
2076 umount_tree(real_mount(mnt
), 0);
2077 unlock_mount_hash();
2081 static bool has_locked_children(struct mount
*mnt
, struct dentry
*dentry
)
2083 struct mount
*child
;
2085 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
2086 if (!is_subdir(child
->mnt_mountpoint
, dentry
))
2089 if (child
->mnt
.mnt_flags
& MNT_LOCKED
)
2096 * clone_private_mount - create a private clone of a path
2097 * @path: path to clone
2099 * This creates a new vfsmount, which will be the clone of @path. The new mount
2100 * will not be attached anywhere in the namespace and will be private (i.e.
2101 * changes to the originating mount won't be propagated into this).
2103 * Release with mntput().
2105 struct vfsmount
*clone_private_mount(const struct path
*path
)
2107 struct mount
*old_mnt
= real_mount(path
->mnt
);
2108 struct mount
*new_mnt
;
2110 down_read(&namespace_sem
);
2111 if (IS_MNT_UNBINDABLE(old_mnt
))
2114 if (!check_mnt(old_mnt
))
2117 if (has_locked_children(old_mnt
, path
->dentry
))
2120 new_mnt
= clone_mnt(old_mnt
, path
->dentry
, CL_PRIVATE
);
2121 up_read(&namespace_sem
);
2123 if (IS_ERR(new_mnt
))
2124 return ERR_CAST(new_mnt
);
2126 /* Longterm mount to be removed by kern_unmount*() */
2127 new_mnt
->mnt_ns
= MNT_NS_INTERNAL
;
2129 return &new_mnt
->mnt
;
2132 up_read(&namespace_sem
);
2133 return ERR_PTR(-EINVAL
);
2135 EXPORT_SYMBOL_GPL(clone_private_mount
);
2137 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
2138 struct vfsmount
*root
)
2141 int res
= f(root
, arg
);
2144 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
2145 res
= f(&mnt
->mnt
, arg
);
2152 static void lock_mnt_tree(struct mount
*mnt
)
2156 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2157 int flags
= p
->mnt
.mnt_flags
;
2158 /* Don't allow unprivileged users to change mount flags */
2159 flags
|= MNT_LOCK_ATIME
;
2161 if (flags
& MNT_READONLY
)
2162 flags
|= MNT_LOCK_READONLY
;
2164 if (flags
& MNT_NODEV
)
2165 flags
|= MNT_LOCK_NODEV
;
2167 if (flags
& MNT_NOSUID
)
2168 flags
|= MNT_LOCK_NOSUID
;
2170 if (flags
& MNT_NOEXEC
)
2171 flags
|= MNT_LOCK_NOEXEC
;
2172 /* Don't allow unprivileged users to reveal what is under a mount */
2173 if (list_empty(&p
->mnt_expire
))
2174 flags
|= MNT_LOCKED
;
2175 p
->mnt
.mnt_flags
= flags
;
2179 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
2183 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
2184 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
2185 mnt_release_group_id(p
);
2189 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
2193 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
2194 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
2195 int err
= mnt_alloc_group_id(p
);
2197 cleanup_group_ids(mnt
, p
);
2206 int count_mounts(struct mnt_namespace
*ns
, struct mount
*mnt
)
2208 unsigned int max
= READ_ONCE(sysctl_mount_max
);
2209 unsigned int mounts
= 0;
2212 if (ns
->mounts
>= max
)
2215 if (ns
->pending_mounts
>= max
)
2217 max
-= ns
->pending_mounts
;
2219 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
2225 ns
->pending_mounts
+= mounts
;
2229 enum mnt_tree_flags_t
{
2230 MNT_TREE_MOVE
= BIT(0),
2231 MNT_TREE_BENEATH
= BIT(1),
2235 * attach_recursive_mnt - attach a source mount tree
2236 * @source_mnt: mount tree to be attached
2237 * @top_mnt: mount that @source_mnt will be mounted on or mounted beneath
2238 * @dest_mp: the mountpoint @source_mnt will be mounted at
2239 * @flags: modify how @source_mnt is supposed to be attached
2241 * NOTE: in the table below explains the semantics when a source mount
2242 * of a given type is attached to a destination mount of a given type.
2243 * ---------------------------------------------------------------------------
2244 * | BIND MOUNT OPERATION |
2245 * |**************************************************************************
2246 * | source-->| shared | private | slave | unbindable |
2250 * |**************************************************************************
2251 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
2253 * |non-shared| shared (+) | private | slave (*) | invalid |
2254 * ***************************************************************************
2255 * A bind operation clones the source mount and mounts the clone on the
2256 * destination mount.
2258 * (++) the cloned mount is propagated to all the mounts in the propagation
2259 * tree of the destination mount and the cloned mount is added to
2260 * the peer group of the source mount.
2261 * (+) the cloned mount is created under the destination mount and is marked
2262 * as shared. The cloned mount is added to the peer group of the source
2264 * (+++) the mount is propagated to all the mounts in the propagation tree
2265 * of the destination mount and the cloned mount is made slave
2266 * of the same master as that of the source mount. The cloned mount
2267 * is marked as 'shared and slave'.
2268 * (*) the cloned mount is made a slave of the same master as that of the
2271 * ---------------------------------------------------------------------------
2272 * | MOVE MOUNT OPERATION |
2273 * |**************************************************************************
2274 * | source-->| shared | private | slave | unbindable |
2278 * |**************************************************************************
2279 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2281 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2282 * ***************************************************************************
2284 * (+) the mount is moved to the destination. And is then propagated to
2285 * all the mounts in the propagation tree of the destination mount.
2286 * (+*) the mount is moved to the destination.
2287 * (+++) the mount is moved to the destination and is then propagated to
2288 * all the mounts belonging to the destination mount's propagation tree.
2289 * the mount is marked as 'shared and slave'.
2290 * (*) the mount continues to be a slave at the new location.
2292 * if the source mount is a tree, the operations explained above is
2293 * applied to each mount in the tree.
2294 * Must be called without spinlocks held, since this function can sleep
2297 * Context: The function expects namespace_lock() to be held.
2298 * Return: If @source_mnt was successfully attached 0 is returned.
2299 * Otherwise a negative error code is returned.
2301 static int attach_recursive_mnt(struct mount
*source_mnt
,
2302 struct mount
*top_mnt
,
2303 struct mountpoint
*dest_mp
,
2304 enum mnt_tree_flags_t flags
)
2306 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2307 HLIST_HEAD(tree_list
);
2308 struct mnt_namespace
*ns
= top_mnt
->mnt_ns
;
2309 struct mountpoint
*smp
;
2310 struct mount
*child
, *dest_mnt
, *p
;
2311 struct hlist_node
*n
;
2313 bool moving
= flags
& MNT_TREE_MOVE
, beneath
= flags
& MNT_TREE_BENEATH
;
2316 * Preallocate a mountpoint in case the new mounts need to be
2317 * mounted beneath mounts on the same mountpoint.
2319 smp
= get_mountpoint(source_mnt
->mnt
.mnt_root
);
2321 return PTR_ERR(smp
);
2323 /* Is there space to add these mounts to the mount namespace? */
2325 err
= count_mounts(ns
, source_mnt
);
2331 dest_mnt
= top_mnt
->mnt_parent
;
2335 if (IS_MNT_SHARED(dest_mnt
)) {
2336 err
= invent_group_ids(source_mnt
, true);
2339 err
= propagate_mnt(dest_mnt
, dest_mp
, source_mnt
, &tree_list
);
2343 goto out_cleanup_ids
;
2345 if (IS_MNT_SHARED(dest_mnt
)) {
2346 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
2353 unhash_mnt(source_mnt
);
2354 attach_mnt(source_mnt
, top_mnt
, dest_mp
, beneath
);
2355 touch_mnt_namespace(source_mnt
->mnt_ns
);
2357 if (source_mnt
->mnt_ns
) {
2358 /* move from anon - the caller will destroy */
2359 list_del_init(&source_mnt
->mnt_ns
->list
);
2362 mnt_set_mountpoint_beneath(source_mnt
, top_mnt
, smp
);
2364 mnt_set_mountpoint(dest_mnt
, dest_mp
, source_mnt
);
2365 commit_tree(source_mnt
);
2368 hlist_for_each_entry_safe(child
, n
, &tree_list
, mnt_hash
) {
2370 hlist_del_init(&child
->mnt_hash
);
2371 q
= __lookup_mnt(&child
->mnt_parent
->mnt
,
2372 child
->mnt_mountpoint
);
2374 mnt_change_mountpoint(child
, smp
, q
);
2375 /* Notice when we are propagating across user namespaces */
2376 if (child
->mnt_parent
->mnt_ns
->user_ns
!= user_ns
)
2377 lock_mnt_tree(child
);
2378 child
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2381 put_mountpoint(smp
);
2382 unlock_mount_hash();
2387 while (!hlist_empty(&tree_list
)) {
2388 child
= hlist_entry(tree_list
.first
, struct mount
, mnt_hash
);
2389 child
->mnt_parent
->mnt_ns
->pending_mounts
= 0;
2390 umount_tree(child
, UMOUNT_SYNC
);
2392 unlock_mount_hash();
2393 cleanup_group_ids(source_mnt
, NULL
);
2395 ns
->pending_mounts
= 0;
2397 read_seqlock_excl(&mount_lock
);
2398 put_mountpoint(smp
);
2399 read_sequnlock_excl(&mount_lock
);
2405 * do_lock_mount - lock mount and mountpoint
2406 * @path: target path
2407 * @beneath: whether the intention is to mount beneath @path
2409 * Follow the mount stack on @path until the top mount @mnt is found. If
2410 * the initial @path->{mnt,dentry} is a mountpoint lookup the first
2411 * mount stacked on top of it. Then simply follow @{mnt,mnt->mnt_root}
2412 * until nothing is stacked on top of it anymore.
2414 * Acquire the inode_lock() on the top mount's ->mnt_root to protect
2415 * against concurrent removal of the new mountpoint from another mount
2418 * If @beneath is requested, acquire inode_lock() on @mnt's mountpoint
2419 * @mp on @mnt->mnt_parent must be acquired. This protects against a
2420 * concurrent unlink of @mp->mnt_dentry from another mount namespace
2421 * where @mnt doesn't have a child mount mounted @mp. A concurrent
2422 * removal of @mnt->mnt_root doesn't matter as nothing will be mounted
2423 * on top of it for @beneath.
2425 * In addition, @beneath needs to make sure that @mnt hasn't been
2426 * unmounted or moved from its current mountpoint in between dropping
2427 * @mount_lock and acquiring @namespace_sem. For the !@beneath case @mnt
2428 * being unmounted would be detected later by e.g., calling
2429 * check_mnt(mnt) in the function it's called from. For the @beneath
2430 * case however, it's useful to detect it directly in do_lock_mount().
2431 * If @mnt hasn't been unmounted then @mnt->mnt_mountpoint still points
2432 * to @mnt->mnt_mp->m_dentry. But if @mnt has been unmounted it will
2433 * point to @mnt->mnt_root and @mnt->mnt_mp will be NULL.
2435 * Return: Either the target mountpoint on the top mount or the top
2436 * mount's mountpoint.
2438 static struct mountpoint
*do_lock_mount(struct path
*path
, bool beneath
)
2440 struct vfsmount
*mnt
= path
->mnt
;
2441 struct dentry
*dentry
;
2442 struct mountpoint
*mp
= ERR_PTR(-ENOENT
);
2448 m
= real_mount(mnt
);
2449 read_seqlock_excl(&mount_lock
);
2450 dentry
= dget(m
->mnt_mountpoint
);
2451 read_sequnlock_excl(&mount_lock
);
2453 dentry
= path
->dentry
;
2456 inode_lock(dentry
->d_inode
);
2457 if (unlikely(cant_mount(dentry
))) {
2458 inode_unlock(dentry
->d_inode
);
2464 if (beneath
&& (!is_mounted(mnt
) || m
->mnt_mountpoint
!= dentry
)) {
2466 inode_unlock(dentry
->d_inode
);
2470 mnt
= lookup_mnt(path
);
2475 inode_unlock(dentry
->d_inode
);
2480 path
->dentry
= dget(mnt
->mnt_root
);
2483 mp
= get_mountpoint(dentry
);
2486 inode_unlock(dentry
->d_inode
);
2496 static inline struct mountpoint
*lock_mount(struct path
*path
)
2498 return do_lock_mount(path
, false);
2501 static void unlock_mount(struct mountpoint
*where
)
2503 struct dentry
*dentry
= where
->m_dentry
;
2505 read_seqlock_excl(&mount_lock
);
2506 put_mountpoint(where
);
2507 read_sequnlock_excl(&mount_lock
);
2510 inode_unlock(dentry
->d_inode
);
2513 static int graft_tree(struct mount
*mnt
, struct mount
*p
, struct mountpoint
*mp
)
2515 if (mnt
->mnt
.mnt_sb
->s_flags
& SB_NOUSER
)
2518 if (d_is_dir(mp
->m_dentry
) !=
2519 d_is_dir(mnt
->mnt
.mnt_root
))
2522 return attach_recursive_mnt(mnt
, p
, mp
, 0);
2526 * Sanity check the flags to change_mnt_propagation.
2529 static int flags_to_propagation_type(int ms_flags
)
2531 int type
= ms_flags
& ~(MS_REC
| MS_SILENT
);
2533 /* Fail if any non-propagation flags are set */
2534 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2536 /* Only one propagation flag should be set */
2537 if (!is_power_of_2(type
))
2543 * recursively change the type of the mountpoint.
2545 static int do_change_type(struct path
*path
, int ms_flags
)
2548 struct mount
*mnt
= real_mount(path
->mnt
);
2549 int recurse
= ms_flags
& MS_REC
;
2553 if (!path_mounted(path
))
2556 type
= flags_to_propagation_type(ms_flags
);
2561 if (type
== MS_SHARED
) {
2562 err
= invent_group_ids(mnt
, recurse
);
2568 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
2569 change_mnt_propagation(m
, type
);
2570 unlock_mount_hash();
2577 static struct mount
*__do_loopback(struct path
*old_path
, int recurse
)
2579 struct mount
*mnt
= ERR_PTR(-EINVAL
), *old
= real_mount(old_path
->mnt
);
2581 if (IS_MNT_UNBINDABLE(old
))
2584 if (!check_mnt(old
) && old_path
->dentry
->d_op
!= &ns_dentry_operations
)
2587 if (!recurse
&& has_locked_children(old
, old_path
->dentry
))
2591 mnt
= copy_tree(old
, old_path
->dentry
, CL_COPY_MNT_NS_FILE
);
2593 mnt
= clone_mnt(old
, old_path
->dentry
, 0);
2596 mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2602 * do loopback mount.
2604 static int do_loopback(struct path
*path
, const char *old_name
,
2607 struct path old_path
;
2608 struct mount
*mnt
= NULL
, *parent
;
2609 struct mountpoint
*mp
;
2611 if (!old_name
|| !*old_name
)
2613 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
2618 if (mnt_ns_loop(old_path
.dentry
))
2621 mp
= lock_mount(path
);
2627 parent
= real_mount(path
->mnt
);
2628 if (!check_mnt(parent
))
2631 mnt
= __do_loopback(&old_path
, recurse
);
2637 err
= graft_tree(mnt
, parent
, mp
);
2640 umount_tree(mnt
, UMOUNT_SYNC
);
2641 unlock_mount_hash();
2646 path_put(&old_path
);
2650 static struct file
*open_detached_copy(struct path
*path
, bool recursive
)
2652 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2653 struct mnt_namespace
*ns
= alloc_mnt_ns(user_ns
, true);
2654 struct mount
*mnt
, *p
;
2658 return ERR_CAST(ns
);
2661 mnt
= __do_loopback(path
, recursive
);
2665 return ERR_CAST(mnt
);
2669 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2674 list_add_tail(&ns
->list
, &mnt
->mnt_list
);
2676 unlock_mount_hash();
2680 path
->mnt
= &mnt
->mnt
;
2681 file
= dentry_open(path
, O_PATH
, current_cred());
2683 dissolve_on_fput(path
->mnt
);
2685 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
2689 SYSCALL_DEFINE3(open_tree
, int, dfd
, const char __user
*, filename
, unsigned, flags
)
2693 int lookup_flags
= LOOKUP_AUTOMOUNT
| LOOKUP_FOLLOW
;
2694 bool detached
= flags
& OPEN_TREE_CLONE
;
2698 BUILD_BUG_ON(OPEN_TREE_CLOEXEC
!= O_CLOEXEC
);
2700 if (flags
& ~(AT_EMPTY_PATH
| AT_NO_AUTOMOUNT
| AT_RECURSIVE
|
2701 AT_SYMLINK_NOFOLLOW
| OPEN_TREE_CLONE
|
2705 if ((flags
& (AT_RECURSIVE
| OPEN_TREE_CLONE
)) == AT_RECURSIVE
)
2708 if (flags
& AT_NO_AUTOMOUNT
)
2709 lookup_flags
&= ~LOOKUP_AUTOMOUNT
;
2710 if (flags
& AT_SYMLINK_NOFOLLOW
)
2711 lookup_flags
&= ~LOOKUP_FOLLOW
;
2712 if (flags
& AT_EMPTY_PATH
)
2713 lookup_flags
|= LOOKUP_EMPTY
;
2715 if (detached
&& !may_mount())
2718 fd
= get_unused_fd_flags(flags
& O_CLOEXEC
);
2722 error
= user_path_at(dfd
, filename
, lookup_flags
, &path
);
2723 if (unlikely(error
)) {
2724 file
= ERR_PTR(error
);
2727 file
= open_detached_copy(&path
, flags
& AT_RECURSIVE
);
2729 file
= dentry_open(&path
, O_PATH
, current_cred());
2734 return PTR_ERR(file
);
2736 fd_install(fd
, file
);
2741 * Don't allow locked mount flags to be cleared.
2743 * No locks need to be held here while testing the various MNT_LOCK
2744 * flags because those flags can never be cleared once they are set.
2746 static bool can_change_locked_flags(struct mount
*mnt
, unsigned int mnt_flags
)
2748 unsigned int fl
= mnt
->mnt
.mnt_flags
;
2750 if ((fl
& MNT_LOCK_READONLY
) &&
2751 !(mnt_flags
& MNT_READONLY
))
2754 if ((fl
& MNT_LOCK_NODEV
) &&
2755 !(mnt_flags
& MNT_NODEV
))
2758 if ((fl
& MNT_LOCK_NOSUID
) &&
2759 !(mnt_flags
& MNT_NOSUID
))
2762 if ((fl
& MNT_LOCK_NOEXEC
) &&
2763 !(mnt_flags
& MNT_NOEXEC
))
2766 if ((fl
& MNT_LOCK_ATIME
) &&
2767 ((fl
& MNT_ATIME_MASK
) != (mnt_flags
& MNT_ATIME_MASK
)))
2773 static int change_mount_ro_state(struct mount
*mnt
, unsigned int mnt_flags
)
2775 bool readonly_request
= (mnt_flags
& MNT_READONLY
);
2777 if (readonly_request
== __mnt_is_readonly(&mnt
->mnt
))
2780 if (readonly_request
)
2781 return mnt_make_readonly(mnt
);
2783 mnt
->mnt
.mnt_flags
&= ~MNT_READONLY
;
2787 static void set_mount_attributes(struct mount
*mnt
, unsigned int mnt_flags
)
2789 mnt_flags
|= mnt
->mnt
.mnt_flags
& ~MNT_USER_SETTABLE_MASK
;
2790 mnt
->mnt
.mnt_flags
= mnt_flags
;
2791 touch_mnt_namespace(mnt
->mnt_ns
);
2794 static void mnt_warn_timestamp_expiry(struct path
*mountpoint
, struct vfsmount
*mnt
)
2796 struct super_block
*sb
= mnt
->mnt_sb
;
2798 if (!__mnt_is_readonly(mnt
) &&
2799 (!(sb
->s_iflags
& SB_I_TS_EXPIRY_WARNED
)) &&
2800 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX
> sb
->s_time_max
)) {
2801 char *buf
= (char *)__get_free_page(GFP_KERNEL
);
2802 char *mntpath
= buf
? d_path(mountpoint
, buf
, PAGE_SIZE
) : ERR_PTR(-ENOMEM
);
2804 pr_warn("%s filesystem being %s at %s supports timestamps until %ptTd (0x%llx)\n",
2806 is_mounted(mnt
) ? "remounted" : "mounted",
2807 mntpath
, &sb
->s_time_max
,
2808 (unsigned long long)sb
->s_time_max
);
2810 free_page((unsigned long)buf
);
2811 sb
->s_iflags
|= SB_I_TS_EXPIRY_WARNED
;
2816 * Handle reconfiguration of the mountpoint only without alteration of the
2817 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2820 static int do_reconfigure_mnt(struct path
*path
, unsigned int mnt_flags
)
2822 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2823 struct mount
*mnt
= real_mount(path
->mnt
);
2826 if (!check_mnt(mnt
))
2829 if (!path_mounted(path
))
2832 if (!can_change_locked_flags(mnt
, mnt_flags
))
2836 * We're only checking whether the superblock is read-only not
2837 * changing it, so only take down_read(&sb->s_umount).
2839 down_read(&sb
->s_umount
);
2841 ret
= change_mount_ro_state(mnt
, mnt_flags
);
2843 set_mount_attributes(mnt
, mnt_flags
);
2844 unlock_mount_hash();
2845 up_read(&sb
->s_umount
);
2847 mnt_warn_timestamp_expiry(path
, &mnt
->mnt
);
2853 * change filesystem flags. dir should be a physical root of filesystem.
2854 * If you've mounted a non-root directory somewhere and want to do remount
2855 * on it - tough luck.
2857 static int do_remount(struct path
*path
, int ms_flags
, int sb_flags
,
2858 int mnt_flags
, void *data
)
2861 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2862 struct mount
*mnt
= real_mount(path
->mnt
);
2863 struct fs_context
*fc
;
2865 if (!check_mnt(mnt
))
2868 if (!path_mounted(path
))
2871 if (!can_change_locked_flags(mnt
, mnt_flags
))
2874 fc
= fs_context_for_reconfigure(path
->dentry
, sb_flags
, MS_RMT_MASK
);
2879 err
= parse_monolithic_mount_data(fc
, data
);
2881 down_write(&sb
->s_umount
);
2883 if (ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
)) {
2884 err
= reconfigure_super(fc
);
2887 set_mount_attributes(mnt
, mnt_flags
);
2888 unlock_mount_hash();
2891 up_write(&sb
->s_umount
);
2894 mnt_warn_timestamp_expiry(path
, &mnt
->mnt
);
2900 static inline int tree_contains_unbindable(struct mount
*mnt
)
2903 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2904 if (IS_MNT_UNBINDABLE(p
))
2911 * Check that there aren't references to earlier/same mount namespaces in the
2912 * specified subtree. Such references can act as pins for mount namespaces
2913 * that aren't checked by the mount-cycle checking code, thereby allowing
2914 * cycles to be made.
2916 static bool check_for_nsfs_mounts(struct mount
*subtree
)
2922 for (p
= subtree
; p
; p
= next_mnt(p
, subtree
))
2923 if (mnt_ns_loop(p
->mnt
.mnt_root
))
2928 unlock_mount_hash();
2932 static int do_set_group(struct path
*from_path
, struct path
*to_path
)
2934 struct mount
*from
, *to
;
2937 from
= real_mount(from_path
->mnt
);
2938 to
= real_mount(to_path
->mnt
);
2943 /* To and From must be mounted */
2944 if (!is_mounted(&from
->mnt
))
2946 if (!is_mounted(&to
->mnt
))
2950 /* We should be allowed to modify mount namespaces of both mounts */
2951 if (!ns_capable(from
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
))
2953 if (!ns_capable(to
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
))
2957 /* To and From paths should be mount roots */
2958 if (!path_mounted(from_path
))
2960 if (!path_mounted(to_path
))
2963 /* Setting sharing groups is only allowed across same superblock */
2964 if (from
->mnt
.mnt_sb
!= to
->mnt
.mnt_sb
)
2967 /* From mount root should be wider than To mount root */
2968 if (!is_subdir(to
->mnt
.mnt_root
, from
->mnt
.mnt_root
))
2971 /* From mount should not have locked children in place of To's root */
2972 if (has_locked_children(from
, to
->mnt
.mnt_root
))
2975 /* Setting sharing groups is only allowed on private mounts */
2976 if (IS_MNT_SHARED(to
) || IS_MNT_SLAVE(to
))
2979 /* From should not be private */
2980 if (!IS_MNT_SHARED(from
) && !IS_MNT_SLAVE(from
))
2983 if (IS_MNT_SLAVE(from
)) {
2984 struct mount
*m
= from
->mnt_master
;
2986 list_add(&to
->mnt_slave
, &m
->mnt_slave_list
);
2990 if (IS_MNT_SHARED(from
)) {
2991 to
->mnt_group_id
= from
->mnt_group_id
;
2992 list_add(&to
->mnt_share
, &from
->mnt_share
);
2995 unlock_mount_hash();
3005 * path_overmounted - check if path is overmounted
3006 * @path: path to check
3008 * Check if path is overmounted, i.e., if there's a mount on top of
3009 * @path->mnt with @path->dentry as mountpoint.
3011 * Context: This function expects namespace_lock() to be held.
3012 * Return: If path is overmounted true is returned, false if not.
3014 static inline bool path_overmounted(const struct path
*path
)
3017 if (unlikely(__lookup_mnt(path
->mnt
, path
->dentry
))) {
3026 * can_move_mount_beneath - check that we can mount beneath the top mount
3027 * @from: mount to mount beneath
3028 * @to: mount under which to mount
3030 * - Make sure that @to->dentry is actually the root of a mount under
3031 * which we can mount another mount.
3032 * - Make sure that nothing can be mounted beneath the caller's current
3033 * root or the rootfs of the namespace.
3034 * - Make sure that the caller can unmount the topmost mount ensuring
3035 * that the caller could reveal the underlying mountpoint.
3036 * - Ensure that nothing has been mounted on top of @from before we
3037 * grabbed @namespace_sem to avoid creating pointless shadow mounts.
3038 * - Prevent mounting beneath a mount if the propagation relationship
3039 * between the source mount, parent mount, and top mount would lead to
3040 * nonsensical mount trees.
3042 * Context: This function expects namespace_lock() to be held.
3043 * Return: On success 0, and on error a negative error code is returned.
3045 static int can_move_mount_beneath(const struct path
*from
,
3046 const struct path
*to
,
3047 const struct mountpoint
*mp
)
3049 struct mount
*mnt_from
= real_mount(from
->mnt
),
3050 *mnt_to
= real_mount(to
->mnt
),
3051 *parent_mnt_to
= mnt_to
->mnt_parent
;
3053 if (!mnt_has_parent(mnt_to
))
3056 if (!path_mounted(to
))
3059 if (IS_MNT_LOCKED(mnt_to
))
3062 /* Avoid creating shadow mounts during mount propagation. */
3063 if (path_overmounted(from
))
3067 * Mounting beneath the rootfs only makes sense when the
3068 * semantics of pivot_root(".", ".") are used.
3070 if (&mnt_to
->mnt
== current
->fs
->root
.mnt
)
3072 if (parent_mnt_to
== current
->nsproxy
->mnt_ns
->root
)
3075 for (struct mount
*p
= mnt_from
; mnt_has_parent(p
); p
= p
->mnt_parent
)
3080 * If the parent mount propagates to the child mount this would
3081 * mean mounting @mnt_from on @mnt_to->mnt_parent and then
3082 * propagating a copy @c of @mnt_from on top of @mnt_to. This
3083 * defeats the whole purpose of mounting beneath another mount.
3085 if (propagation_would_overmount(parent_mnt_to
, mnt_to
, mp
))
3089 * If @mnt_to->mnt_parent propagates to @mnt_from this would
3090 * mean propagating a copy @c of @mnt_from on top of @mnt_from.
3091 * Afterwards @mnt_from would be mounted on top of
3092 * @mnt_to->mnt_parent and @mnt_to would be unmounted from
3093 * @mnt->mnt_parent and remounted on @mnt_from. But since @c is
3094 * already mounted on @mnt_from, @mnt_to would ultimately be
3095 * remounted on top of @c. Afterwards, @mnt_from would be
3096 * covered by a copy @c of @mnt_from and @c would be covered by
3097 * @mnt_from itself. This defeats the whole purpose of mounting
3098 * @mnt_from beneath @mnt_to.
3100 if (propagation_would_overmount(parent_mnt_to
, mnt_from
, mp
))
3106 static int do_move_mount(struct path
*old_path
, struct path
*new_path
,
3109 struct mnt_namespace
*ns
;
3112 struct mount
*parent
;
3113 struct mountpoint
*mp
, *old_mp
;
3116 enum mnt_tree_flags_t flags
= 0;
3118 mp
= do_lock_mount(new_path
, beneath
);
3122 old
= real_mount(old_path
->mnt
);
3123 p
= real_mount(new_path
->mnt
);
3124 parent
= old
->mnt_parent
;
3125 attached
= mnt_has_parent(old
);
3127 flags
|= MNT_TREE_MOVE
;
3128 old_mp
= old
->mnt_mp
;
3132 /* The mountpoint must be in our namespace. */
3136 /* The thing moved must be mounted... */
3137 if (!is_mounted(&old
->mnt
))
3140 /* ... and either ours or the root of anon namespace */
3141 if (!(attached
? check_mnt(old
) : is_anon_ns(ns
)))
3144 if (old
->mnt
.mnt_flags
& MNT_LOCKED
)
3147 if (!path_mounted(old_path
))
3150 if (d_is_dir(new_path
->dentry
) !=
3151 d_is_dir(old_path
->dentry
))
3154 * Don't move a mount residing in a shared parent.
3156 if (attached
&& IS_MNT_SHARED(parent
))
3160 err
= can_move_mount_beneath(old_path
, new_path
, mp
);
3166 flags
|= MNT_TREE_BENEATH
;
3170 * Don't move a mount tree containing unbindable mounts to a destination
3171 * mount which is shared.
3173 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
3176 if (!check_for_nsfs_mounts(old
))
3178 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
3182 err
= attach_recursive_mnt(old
, real_mount(new_path
->mnt
), mp
, flags
);
3186 /* if the mount is moved, it should no longer be expire
3188 list_del_init(&old
->mnt_expire
);
3190 put_mountpoint(old_mp
);
3195 mntput_no_expire(parent
);
3202 static int do_move_mount_old(struct path
*path
, const char *old_name
)
3204 struct path old_path
;
3207 if (!old_name
|| !*old_name
)
3210 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
3214 err
= do_move_mount(&old_path
, path
, false);
3215 path_put(&old_path
);
3220 * add a mount into a namespace's mount tree
3222 static int do_add_mount(struct mount
*newmnt
, struct mountpoint
*mp
,
3223 const struct path
*path
, int mnt_flags
)
3225 struct mount
*parent
= real_mount(path
->mnt
);
3227 mnt_flags
&= ~MNT_INTERNAL_FLAGS
;
3229 if (unlikely(!check_mnt(parent
))) {
3230 /* that's acceptable only for automounts done in private ns */
3231 if (!(mnt_flags
& MNT_SHRINKABLE
))
3233 /* ... and for those we'd better have mountpoint still alive */
3234 if (!parent
->mnt_ns
)
3238 /* Refuse the same filesystem on the same mount point */
3239 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&& path_mounted(path
))
3242 if (d_is_symlink(newmnt
->mnt
.mnt_root
))
3245 newmnt
->mnt
.mnt_flags
= mnt_flags
;
3246 return graft_tree(newmnt
, parent
, mp
);
3249 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
);
3252 * Create a new mount using a superblock configuration and request it
3253 * be added to the namespace tree.
3255 static int do_new_mount_fc(struct fs_context
*fc
, struct path
*mountpoint
,
3256 unsigned int mnt_flags
)
3258 struct vfsmount
*mnt
;
3259 struct mountpoint
*mp
;
3260 struct super_block
*sb
= fc
->root
->d_sb
;
3263 error
= security_sb_kern_mount(sb
);
3264 if (!error
&& mount_too_revealing(sb
, &mnt_flags
))
3267 if (unlikely(error
)) {
3272 up_write(&sb
->s_umount
);
3274 mnt
= vfs_create_mount(fc
);
3276 return PTR_ERR(mnt
);
3278 mnt_warn_timestamp_expiry(mountpoint
, mnt
);
3280 mp
= lock_mount(mountpoint
);
3285 error
= do_add_mount(real_mount(mnt
), mp
, mountpoint
, mnt_flags
);
3293 * create a new mount for userspace and request it to be added into the
3296 static int do_new_mount(struct path
*path
, const char *fstype
, int sb_flags
,
3297 int mnt_flags
, const char *name
, void *data
)
3299 struct file_system_type
*type
;
3300 struct fs_context
*fc
;
3301 const char *subtype
= NULL
;
3307 type
= get_fs_type(fstype
);
3311 if (type
->fs_flags
& FS_HAS_SUBTYPE
) {
3312 subtype
= strchr(fstype
, '.');
3316 put_filesystem(type
);
3322 fc
= fs_context_for_mount(type
, sb_flags
);
3323 put_filesystem(type
);
3328 err
= vfs_parse_fs_string(fc
, "subtype",
3329 subtype
, strlen(subtype
));
3331 err
= vfs_parse_fs_string(fc
, "source", name
, strlen(name
));
3333 err
= parse_monolithic_mount_data(fc
, data
);
3334 if (!err
&& !mount_capable(fc
))
3337 err
= vfs_get_tree(fc
);
3339 err
= do_new_mount_fc(fc
, path
, mnt_flags
);
3345 int finish_automount(struct vfsmount
*m
, const struct path
*path
)
3347 struct dentry
*dentry
= path
->dentry
;
3348 struct mountpoint
*mp
;
3357 mnt
= real_mount(m
);
3358 /* The new mount record should have at least 2 refs to prevent it being
3359 * expired before we get a chance to add it
3361 BUG_ON(mnt_get_count(mnt
) < 2);
3363 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
3364 m
->mnt_root
== dentry
) {
3370 * we don't want to use lock_mount() - in this case finding something
3371 * that overmounts our mountpoint to be means "quitely drop what we've
3372 * got", not "try to mount it on top".
3374 inode_lock(dentry
->d_inode
);
3376 if (unlikely(cant_mount(dentry
))) {
3378 goto discard_locked
;
3380 if (path_overmounted(path
)) {
3382 goto discard_locked
;
3384 mp
= get_mountpoint(dentry
);
3387 goto discard_locked
;
3390 err
= do_add_mount(mnt
, mp
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
3399 inode_unlock(dentry
->d_inode
);
3401 /* remove m from any expiration list it may be on */
3402 if (!list_empty(&mnt
->mnt_expire
)) {
3404 list_del_init(&mnt
->mnt_expire
);
3413 * mnt_set_expiry - Put a mount on an expiration list
3414 * @mnt: The mount to list.
3415 * @expiry_list: The list to add the mount to.
3417 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
3421 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
3425 EXPORT_SYMBOL(mnt_set_expiry
);
3428 * process a list of expirable mountpoints with the intent of discarding any
3429 * mountpoints that aren't in use and haven't been touched since last we came
3432 void mark_mounts_for_expiry(struct list_head
*mounts
)
3434 struct mount
*mnt
, *next
;
3435 LIST_HEAD(graveyard
);
3437 if (list_empty(mounts
))
3443 /* extract from the expiration list every vfsmount that matches the
3444 * following criteria:
3445 * - only referenced by its parent vfsmount
3446 * - still marked for expiry (marked on the last call here; marks are
3447 * cleared by mntput())
3449 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
3450 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
3451 propagate_mount_busy(mnt
, 1))
3453 list_move(&mnt
->mnt_expire
, &graveyard
);
3455 while (!list_empty(&graveyard
)) {
3456 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
3457 touch_mnt_namespace(mnt
->mnt_ns
);
3458 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
3460 unlock_mount_hash();
3464 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
3467 * Ripoff of 'select_parent()'
3469 * search the list of submounts for a given mountpoint, and move any
3470 * shrinkable submounts to the 'graveyard' list.
3472 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
3474 struct mount
*this_parent
= parent
;
3475 struct list_head
*next
;
3479 next
= this_parent
->mnt_mounts
.next
;
3481 while (next
!= &this_parent
->mnt_mounts
) {
3482 struct list_head
*tmp
= next
;
3483 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
3486 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
3489 * Descend a level if the d_mounts list is non-empty.
3491 if (!list_empty(&mnt
->mnt_mounts
)) {
3496 if (!propagate_mount_busy(mnt
, 1)) {
3497 list_move_tail(&mnt
->mnt_expire
, graveyard
);
3502 * All done at this level ... ascend and resume the search
3504 if (this_parent
!= parent
) {
3505 next
= this_parent
->mnt_child
.next
;
3506 this_parent
= this_parent
->mnt_parent
;
3513 * process a list of expirable mountpoints with the intent of discarding any
3514 * submounts of a specific parent mountpoint
3516 * mount_lock must be held for write
3518 static void shrink_submounts(struct mount
*mnt
)
3520 LIST_HEAD(graveyard
);
3523 /* extract submounts of 'mountpoint' from the expiration list */
3524 while (select_submounts(mnt
, &graveyard
)) {
3525 while (!list_empty(&graveyard
)) {
3526 m
= list_first_entry(&graveyard
, struct mount
,
3528 touch_mnt_namespace(m
->mnt_ns
);
3529 umount_tree(m
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
3534 static void *copy_mount_options(const void __user
* data
)
3537 unsigned left
, offset
;
3542 copy
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
3544 return ERR_PTR(-ENOMEM
);
3546 left
= copy_from_user(copy
, data
, PAGE_SIZE
);
3549 * Not all architectures have an exact copy_from_user(). Resort to
3552 offset
= PAGE_SIZE
- left
;
3555 if (get_user(c
, (const char __user
*)data
+ offset
))
3562 if (left
== PAGE_SIZE
) {
3564 return ERR_PTR(-EFAULT
);
3570 static char *copy_mount_string(const void __user
*data
)
3572 return data
? strndup_user(data
, PATH_MAX
) : NULL
;
3576 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3577 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3579 * data is a (void *) that can point to any structure up to
3580 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3581 * information (or be NULL).
3583 * Pre-0.97 versions of mount() didn't have a flags word.
3584 * When the flags word was introduced its top half was required
3585 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3586 * Therefore, if this magic number is present, it carries no information
3587 * and must be discarded.
3589 int path_mount(const char *dev_name
, struct path
*path
,
3590 const char *type_page
, unsigned long flags
, void *data_page
)
3592 unsigned int mnt_flags
= 0, sb_flags
;
3596 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
3597 flags
&= ~MS_MGC_MSK
;
3599 /* Basic sanity checks */
3601 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
3603 if (flags
& MS_NOUSER
)
3606 ret
= security_sb_mount(dev_name
, path
, type_page
, flags
, data_page
);
3611 if (flags
& SB_MANDLOCK
)
3614 /* Default to relatime unless overriden */
3615 if (!(flags
& MS_NOATIME
))
3616 mnt_flags
|= MNT_RELATIME
;
3618 /* Separate the per-mountpoint flags */
3619 if (flags
& MS_NOSUID
)
3620 mnt_flags
|= MNT_NOSUID
;
3621 if (flags
& MS_NODEV
)
3622 mnt_flags
|= MNT_NODEV
;
3623 if (flags
& MS_NOEXEC
)
3624 mnt_flags
|= MNT_NOEXEC
;
3625 if (flags
& MS_NOATIME
)
3626 mnt_flags
|= MNT_NOATIME
;
3627 if (flags
& MS_NODIRATIME
)
3628 mnt_flags
|= MNT_NODIRATIME
;
3629 if (flags
& MS_STRICTATIME
)
3630 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
3631 if (flags
& MS_RDONLY
)
3632 mnt_flags
|= MNT_READONLY
;
3633 if (flags
& MS_NOSYMFOLLOW
)
3634 mnt_flags
|= MNT_NOSYMFOLLOW
;
3636 /* The default atime for remount is preservation */
3637 if ((flags
& MS_REMOUNT
) &&
3638 ((flags
& (MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
|
3639 MS_STRICTATIME
)) == 0)) {
3640 mnt_flags
&= ~MNT_ATIME_MASK
;
3641 mnt_flags
|= path
->mnt
->mnt_flags
& MNT_ATIME_MASK
;
3644 sb_flags
= flags
& (SB_RDONLY
|
3653 if ((flags
& (MS_REMOUNT
| MS_BIND
)) == (MS_REMOUNT
| MS_BIND
))
3654 return do_reconfigure_mnt(path
, mnt_flags
);
3655 if (flags
& MS_REMOUNT
)
3656 return do_remount(path
, flags
, sb_flags
, mnt_flags
, data_page
);
3657 if (flags
& MS_BIND
)
3658 return do_loopback(path
, dev_name
, flags
& MS_REC
);
3659 if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
3660 return do_change_type(path
, flags
);
3661 if (flags
& MS_MOVE
)
3662 return do_move_mount_old(path
, dev_name
);
3664 return do_new_mount(path
, type_page
, sb_flags
, mnt_flags
, dev_name
,
3668 long do_mount(const char *dev_name
, const char __user
*dir_name
,
3669 const char *type_page
, unsigned long flags
, void *data_page
)
3674 ret
= user_path_at(AT_FDCWD
, dir_name
, LOOKUP_FOLLOW
, &path
);
3677 ret
= path_mount(dev_name
, &path
, type_page
, flags
, data_page
);
3682 static struct ucounts
*inc_mnt_namespaces(struct user_namespace
*ns
)
3684 return inc_ucount(ns
, current_euid(), UCOUNT_MNT_NAMESPACES
);
3687 static void dec_mnt_namespaces(struct ucounts
*ucounts
)
3689 dec_ucount(ucounts
, UCOUNT_MNT_NAMESPACES
);
3692 static void free_mnt_ns(struct mnt_namespace
*ns
)
3694 if (!is_anon_ns(ns
))
3695 ns_free_inum(&ns
->ns
);
3696 dec_mnt_namespaces(ns
->ucounts
);
3697 put_user_ns(ns
->user_ns
);
3702 * Assign a sequence number so we can detect when we attempt to bind
3703 * mount a reference to an older mount namespace into the current
3704 * mount namespace, preventing reference counting loops. A 64bit
3705 * number incrementing at 10Ghz will take 12,427 years to wrap which
3706 * is effectively never, so we can ignore the possibility.
3708 static atomic64_t mnt_ns_seq
= ATOMIC64_INIT(1);
3710 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*user_ns
, bool anon
)
3712 struct mnt_namespace
*new_ns
;
3713 struct ucounts
*ucounts
;
3716 ucounts
= inc_mnt_namespaces(user_ns
);
3718 return ERR_PTR(-ENOSPC
);
3720 new_ns
= kzalloc(sizeof(struct mnt_namespace
), GFP_KERNEL_ACCOUNT
);
3722 dec_mnt_namespaces(ucounts
);
3723 return ERR_PTR(-ENOMEM
);
3726 ret
= ns_alloc_inum(&new_ns
->ns
);
3729 dec_mnt_namespaces(ucounts
);
3730 return ERR_PTR(ret
);
3733 new_ns
->ns
.ops
= &mntns_operations
;
3735 new_ns
->seq
= atomic64_add_return(1, &mnt_ns_seq
);
3736 refcount_set(&new_ns
->ns
.count
, 1);
3737 INIT_LIST_HEAD(&new_ns
->list
);
3738 init_waitqueue_head(&new_ns
->poll
);
3739 spin_lock_init(&new_ns
->ns_lock
);
3740 new_ns
->user_ns
= get_user_ns(user_ns
);
3741 new_ns
->ucounts
= ucounts
;
3746 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
3747 struct user_namespace
*user_ns
, struct fs_struct
*new_fs
)
3749 struct mnt_namespace
*new_ns
;
3750 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
3751 struct mount
*p
, *q
;
3758 if (likely(!(flags
& CLONE_NEWNS
))) {
3765 new_ns
= alloc_mnt_ns(user_ns
, false);
3770 /* First pass: copy the tree topology */
3771 copy_flags
= CL_COPY_UNBINDABLE
| CL_EXPIRE
;
3772 if (user_ns
!= ns
->user_ns
)
3773 copy_flags
|= CL_SHARED_TO_SLAVE
;
3774 new = copy_tree(old
, old
->mnt
.mnt_root
, copy_flags
);
3777 free_mnt_ns(new_ns
);
3778 return ERR_CAST(new);
3780 if (user_ns
!= ns
->user_ns
) {
3783 unlock_mount_hash();
3786 list_add_tail(&new_ns
->list
, &new->mnt_list
);
3789 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3790 * as belonging to new namespace. We have already acquired a private
3791 * fs_struct, so tsk->fs->lock is not needed.
3799 if (&p
->mnt
== new_fs
->root
.mnt
) {
3800 new_fs
->root
.mnt
= mntget(&q
->mnt
);
3803 if (&p
->mnt
== new_fs
->pwd
.mnt
) {
3804 new_fs
->pwd
.mnt
= mntget(&q
->mnt
);
3808 p
= next_mnt(p
, old
);
3809 q
= next_mnt(q
, new);
3812 // an mntns binding we'd skipped?
3813 while (p
->mnt
.mnt_root
!= q
->mnt
.mnt_root
)
3814 p
= next_mnt(skip_mnt_tree(p
), old
);
3826 struct dentry
*mount_subtree(struct vfsmount
*m
, const char *name
)
3828 struct mount
*mnt
= real_mount(m
);
3829 struct mnt_namespace
*ns
;
3830 struct super_block
*s
;
3834 ns
= alloc_mnt_ns(&init_user_ns
, true);
3837 return ERR_CAST(ns
);
3842 list_add(&mnt
->mnt_list
, &ns
->list
);
3844 err
= vfs_path_lookup(m
->mnt_root
, m
,
3845 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
3850 return ERR_PTR(err
);
3852 /* trade a vfsmount reference for active sb one */
3853 s
= path
.mnt
->mnt_sb
;
3854 atomic_inc(&s
->s_active
);
3856 /* lock the sucker */
3857 down_write(&s
->s_umount
);
3858 /* ... and return the root of (sub)tree on it */
3861 EXPORT_SYMBOL(mount_subtree
);
3863 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
3864 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
3871 kernel_type
= copy_mount_string(type
);
3872 ret
= PTR_ERR(kernel_type
);
3873 if (IS_ERR(kernel_type
))
3876 kernel_dev
= copy_mount_string(dev_name
);
3877 ret
= PTR_ERR(kernel_dev
);
3878 if (IS_ERR(kernel_dev
))
3881 options
= copy_mount_options(data
);
3882 ret
= PTR_ERR(options
);
3883 if (IS_ERR(options
))
3886 ret
= do_mount(kernel_dev
, dir_name
, kernel_type
, flags
, options
);
3897 #define FSMOUNT_VALID_FLAGS \
3898 (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
3899 MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \
3900 MOUNT_ATTR_NOSYMFOLLOW)
3902 #define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
3904 #define MOUNT_SETATTR_PROPAGATION_FLAGS \
3905 (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
3907 static unsigned int attr_flags_to_mnt_flags(u64 attr_flags
)
3909 unsigned int mnt_flags
= 0;
3911 if (attr_flags
& MOUNT_ATTR_RDONLY
)
3912 mnt_flags
|= MNT_READONLY
;
3913 if (attr_flags
& MOUNT_ATTR_NOSUID
)
3914 mnt_flags
|= MNT_NOSUID
;
3915 if (attr_flags
& MOUNT_ATTR_NODEV
)
3916 mnt_flags
|= MNT_NODEV
;
3917 if (attr_flags
& MOUNT_ATTR_NOEXEC
)
3918 mnt_flags
|= MNT_NOEXEC
;
3919 if (attr_flags
& MOUNT_ATTR_NODIRATIME
)
3920 mnt_flags
|= MNT_NODIRATIME
;
3921 if (attr_flags
& MOUNT_ATTR_NOSYMFOLLOW
)
3922 mnt_flags
|= MNT_NOSYMFOLLOW
;
3928 * Create a kernel mount representation for a new, prepared superblock
3929 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3931 SYSCALL_DEFINE3(fsmount
, int, fs_fd
, unsigned int, flags
,
3932 unsigned int, attr_flags
)
3934 struct mnt_namespace
*ns
;
3935 struct fs_context
*fc
;
3937 struct path newmount
;
3940 unsigned int mnt_flags
= 0;
3946 if ((flags
& ~(FSMOUNT_CLOEXEC
)) != 0)
3949 if (attr_flags
& ~FSMOUNT_VALID_FLAGS
)
3952 mnt_flags
= attr_flags_to_mnt_flags(attr_flags
);
3954 switch (attr_flags
& MOUNT_ATTR__ATIME
) {
3955 case MOUNT_ATTR_STRICTATIME
:
3957 case MOUNT_ATTR_NOATIME
:
3958 mnt_flags
|= MNT_NOATIME
;
3960 case MOUNT_ATTR_RELATIME
:
3961 mnt_flags
|= MNT_RELATIME
;
3972 if (f
.file
->f_op
!= &fscontext_fops
)
3975 fc
= f
.file
->private_data
;
3977 ret
= mutex_lock_interruptible(&fc
->uapi_mutex
);
3981 /* There must be a valid superblock or we can't mount it */
3987 if (mount_too_revealing(fc
->root
->d_sb
, &mnt_flags
)) {
3988 pr_warn("VFS: Mount too revealing\n");
3993 if (fc
->phase
!= FS_CONTEXT_AWAITING_MOUNT
)
3996 if (fc
->sb_flags
& SB_MANDLOCK
)
3999 newmount
.mnt
= vfs_create_mount(fc
);
4000 if (IS_ERR(newmount
.mnt
)) {
4001 ret
= PTR_ERR(newmount
.mnt
);
4004 newmount
.dentry
= dget(fc
->root
);
4005 newmount
.mnt
->mnt_flags
= mnt_flags
;
4007 /* We've done the mount bit - now move the file context into more or
4008 * less the same state as if we'd done an fspick(). We don't want to
4009 * do any memory allocation or anything like that at this point as we
4010 * don't want to have to handle any errors incurred.
4012 vfs_clean_context(fc
);
4014 ns
= alloc_mnt_ns(current
->nsproxy
->mnt_ns
->user_ns
, true);
4019 mnt
= real_mount(newmount
.mnt
);
4023 list_add(&mnt
->mnt_list
, &ns
->list
);
4024 mntget(newmount
.mnt
);
4026 /* Attach to an apparent O_PATH fd with a note that we need to unmount
4027 * it, not just simply put it.
4029 file
= dentry_open(&newmount
, O_PATH
, fc
->cred
);
4031 dissolve_on_fput(newmount
.mnt
);
4032 ret
= PTR_ERR(file
);
4035 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
4037 ret
= get_unused_fd_flags((flags
& FSMOUNT_CLOEXEC
) ? O_CLOEXEC
: 0);
4039 fd_install(ret
, file
);
4044 path_put(&newmount
);
4046 mutex_unlock(&fc
->uapi_mutex
);
4053 * Move a mount from one place to another. In combination with
4054 * fsopen()/fsmount() this is used to install a new mount and in combination
4055 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
4058 * Note the flags value is a combination of MOVE_MOUNT_* flags.
4060 SYSCALL_DEFINE5(move_mount
,
4061 int, from_dfd
, const char __user
*, from_pathname
,
4062 int, to_dfd
, const char __user
*, to_pathname
,
4063 unsigned int, flags
)
4065 struct path from_path
, to_path
;
4066 unsigned int lflags
;
4072 if (flags
& ~MOVE_MOUNT__MASK
)
4075 if ((flags
& (MOVE_MOUNT_BENEATH
| MOVE_MOUNT_SET_GROUP
)) ==
4076 (MOVE_MOUNT_BENEATH
| MOVE_MOUNT_SET_GROUP
))
4079 /* If someone gives a pathname, they aren't permitted to move
4080 * from an fd that requires unmount as we can't get at the flag
4081 * to clear it afterwards.
4084 if (flags
& MOVE_MOUNT_F_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
4085 if (flags
& MOVE_MOUNT_F_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
4086 if (flags
& MOVE_MOUNT_F_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
4088 ret
= user_path_at(from_dfd
, from_pathname
, lflags
, &from_path
);
4093 if (flags
& MOVE_MOUNT_T_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
4094 if (flags
& MOVE_MOUNT_T_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
4095 if (flags
& MOVE_MOUNT_T_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
4097 ret
= user_path_at(to_dfd
, to_pathname
, lflags
, &to_path
);
4101 ret
= security_move_mount(&from_path
, &to_path
);
4105 if (flags
& MOVE_MOUNT_SET_GROUP
)
4106 ret
= do_set_group(&from_path
, &to_path
);
4108 ret
= do_move_mount(&from_path
, &to_path
,
4109 (flags
& MOVE_MOUNT_BENEATH
));
4114 path_put(&from_path
);
4119 * Return true if path is reachable from root
4121 * namespace_sem or mount_lock is held
4123 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
4124 const struct path
*root
)
4126 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
4127 dentry
= mnt
->mnt_mountpoint
;
4128 mnt
= mnt
->mnt_parent
;
4130 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
4133 bool path_is_under(const struct path
*path1
, const struct path
*path2
)
4136 read_seqlock_excl(&mount_lock
);
4137 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
4138 read_sequnlock_excl(&mount_lock
);
4141 EXPORT_SYMBOL(path_is_under
);
4144 * pivot_root Semantics:
4145 * Moves the root file system of the current process to the directory put_old,
4146 * makes new_root as the new root file system of the current process, and sets
4147 * root/cwd of all processes which had them on the current root to new_root.
4150 * The new_root and put_old must be directories, and must not be on the
4151 * same file system as the current process root. The put_old must be
4152 * underneath new_root, i.e. adding a non-zero number of /.. to the string
4153 * pointed to by put_old must yield the same directory as new_root. No other
4154 * file system may be mounted on put_old. After all, new_root is a mountpoint.
4156 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
4157 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
4158 * in this situation.
4161 * - we don't move root/cwd if they are not at the root (reason: if something
4162 * cared enough to change them, it's probably wrong to force them elsewhere)
4163 * - it's okay to pick a root that isn't the root of a file system, e.g.
4164 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
4165 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
4168 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
4169 const char __user
*, put_old
)
4171 struct path
new, old
, root
;
4172 struct mount
*new_mnt
, *root_mnt
, *old_mnt
, *root_parent
, *ex_parent
;
4173 struct mountpoint
*old_mp
, *root_mp
;
4179 error
= user_path_at(AT_FDCWD
, new_root
,
4180 LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
, &new);
4184 error
= user_path_at(AT_FDCWD
, put_old
,
4185 LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
, &old
);
4189 error
= security_sb_pivotroot(&old
, &new);
4193 get_fs_root(current
->fs
, &root
);
4194 old_mp
= lock_mount(&old
);
4195 error
= PTR_ERR(old_mp
);
4200 new_mnt
= real_mount(new.mnt
);
4201 root_mnt
= real_mount(root
.mnt
);
4202 old_mnt
= real_mount(old
.mnt
);
4203 ex_parent
= new_mnt
->mnt_parent
;
4204 root_parent
= root_mnt
->mnt_parent
;
4205 if (IS_MNT_SHARED(old_mnt
) ||
4206 IS_MNT_SHARED(ex_parent
) ||
4207 IS_MNT_SHARED(root_parent
))
4209 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
4211 if (new_mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
4214 if (d_unlinked(new.dentry
))
4217 if (new_mnt
== root_mnt
|| old_mnt
== root_mnt
)
4218 goto out4
; /* loop, on the same file system */
4220 if (!path_mounted(&root
))
4221 goto out4
; /* not a mountpoint */
4222 if (!mnt_has_parent(root_mnt
))
4223 goto out4
; /* not attached */
4224 if (!path_mounted(&new))
4225 goto out4
; /* not a mountpoint */
4226 if (!mnt_has_parent(new_mnt
))
4227 goto out4
; /* not attached */
4228 /* make sure we can reach put_old from new_root */
4229 if (!is_path_reachable(old_mnt
, old
.dentry
, &new))
4231 /* make certain new is below the root */
4232 if (!is_path_reachable(new_mnt
, new.dentry
, &root
))
4235 umount_mnt(new_mnt
);
4236 root_mp
= unhash_mnt(root_mnt
); /* we'll need its mountpoint */
4237 if (root_mnt
->mnt
.mnt_flags
& MNT_LOCKED
) {
4238 new_mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
4239 root_mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
4241 /* mount old root on put_old */
4242 attach_mnt(root_mnt
, old_mnt
, old_mp
, false);
4243 /* mount new_root on / */
4244 attach_mnt(new_mnt
, root_parent
, root_mp
, false);
4245 mnt_add_count(root_parent
, -1);
4246 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
4247 /* A moved mount should not expire automatically */
4248 list_del_init(&new_mnt
->mnt_expire
);
4249 put_mountpoint(root_mp
);
4250 unlock_mount_hash();
4251 chroot_fs_refs(&root
, &new);
4254 unlock_mount(old_mp
);
4256 mntput_no_expire(ex_parent
);
4267 static unsigned int recalc_flags(struct mount_kattr
*kattr
, struct mount
*mnt
)
4269 unsigned int flags
= mnt
->mnt
.mnt_flags
;
4271 /* flags to clear */
4272 flags
&= ~kattr
->attr_clr
;
4273 /* flags to raise */
4274 flags
|= kattr
->attr_set
;
4279 static int can_idmap_mount(const struct mount_kattr
*kattr
, struct mount
*mnt
)
4281 struct vfsmount
*m
= &mnt
->mnt
;
4282 struct user_namespace
*fs_userns
= m
->mnt_sb
->s_user_ns
;
4284 if (!kattr
->mnt_idmap
)
4288 * Creating an idmapped mount with the filesystem wide idmapping
4289 * doesn't make sense so block that. We don't allow mushy semantics.
4291 if (!check_fsmapping(kattr
->mnt_idmap
, m
->mnt_sb
))
4295 * Once a mount has been idmapped we don't allow it to change its
4296 * mapping. It makes things simpler and callers can just create
4297 * another bind-mount they can idmap if they want to.
4299 if (is_idmapped_mnt(m
))
4302 /* The underlying filesystem doesn't support idmapped mounts yet. */
4303 if (!(m
->mnt_sb
->s_type
->fs_flags
& FS_ALLOW_IDMAP
))
4306 /* We're not controlling the superblock. */
4307 if (!ns_capable(fs_userns
, CAP_SYS_ADMIN
))
4310 /* Mount has already been visible in the filesystem hierarchy. */
4311 if (!is_anon_ns(mnt
->mnt_ns
))
4318 * mnt_allow_writers() - check whether the attribute change allows writers
4319 * @kattr: the new mount attributes
4320 * @mnt: the mount to which @kattr will be applied
4322 * Check whether thew new mount attributes in @kattr allow concurrent writers.
4324 * Return: true if writers need to be held, false if not
4326 static inline bool mnt_allow_writers(const struct mount_kattr
*kattr
,
4327 const struct mount
*mnt
)
4329 return (!(kattr
->attr_set
& MNT_READONLY
) ||
4330 (mnt
->mnt
.mnt_flags
& MNT_READONLY
)) &&
4334 static int mount_setattr_prepare(struct mount_kattr
*kattr
, struct mount
*mnt
)
4339 for (m
= mnt
; m
; m
= next_mnt(m
, mnt
)) {
4340 if (!can_change_locked_flags(m
, recalc_flags(kattr
, m
))) {
4345 err
= can_idmap_mount(kattr
, m
);
4349 if (!mnt_allow_writers(kattr
, m
)) {
4350 err
= mnt_hold_writers(m
);
4355 if (!kattr
->recurse
)
4363 * If we had to call mnt_hold_writers() MNT_WRITE_HOLD will
4364 * be set in @mnt_flags. The loop unsets MNT_WRITE_HOLD for all
4365 * mounts and needs to take care to include the first mount.
4367 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
4368 /* If we had to hold writers unblock them. */
4369 if (p
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
4370 mnt_unhold_writers(p
);
4373 * We're done once the first mount we changed got
4374 * MNT_WRITE_HOLD unset.
4383 static void do_idmap_mount(const struct mount_kattr
*kattr
, struct mount
*mnt
)
4385 if (!kattr
->mnt_idmap
)
4389 * Pairs with smp_load_acquire() in mnt_idmap().
4391 * Since we only allow a mount to change the idmapping once and
4392 * verified this in can_idmap_mount() we know that the mount has
4393 * @nop_mnt_idmap attached to it. So there's no need to drop any
4396 smp_store_release(&mnt
->mnt
.mnt_idmap
, mnt_idmap_get(kattr
->mnt_idmap
));
4399 static void mount_setattr_commit(struct mount_kattr
*kattr
, struct mount
*mnt
)
4403 for (m
= mnt
; m
; m
= next_mnt(m
, mnt
)) {
4406 do_idmap_mount(kattr
, m
);
4407 flags
= recalc_flags(kattr
, m
);
4408 WRITE_ONCE(m
->mnt
.mnt_flags
, flags
);
4410 /* If we had to hold writers unblock them. */
4411 if (m
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
4412 mnt_unhold_writers(m
);
4414 if (kattr
->propagation
)
4415 change_mnt_propagation(m
, kattr
->propagation
);
4416 if (!kattr
->recurse
)
4419 touch_mnt_namespace(mnt
->mnt_ns
);
4422 static int do_mount_setattr(struct path
*path
, struct mount_kattr
*kattr
)
4424 struct mount
*mnt
= real_mount(path
->mnt
);
4427 if (!path_mounted(path
))
4430 if (kattr
->mnt_userns
) {
4431 struct mnt_idmap
*mnt_idmap
;
4433 mnt_idmap
= alloc_mnt_idmap(kattr
->mnt_userns
);
4434 if (IS_ERR(mnt_idmap
))
4435 return PTR_ERR(mnt_idmap
);
4436 kattr
->mnt_idmap
= mnt_idmap
;
4439 if (kattr
->propagation
) {
4441 * Only take namespace_lock() if we're actually changing
4445 if (kattr
->propagation
== MS_SHARED
) {
4446 err
= invent_group_ids(mnt
, kattr
->recurse
);
4457 /* Ensure that this isn't anything purely vfs internal. */
4458 if (!is_mounted(&mnt
->mnt
))
4462 * If this is an attached mount make sure it's located in the callers
4463 * mount namespace. If it's not don't let the caller interact with it.
4464 * If this is a detached mount make sure it has an anonymous mount
4465 * namespace attached to it, i.e. we've created it via OPEN_TREE_CLONE.
4467 if (!(mnt_has_parent(mnt
) ? check_mnt(mnt
) : is_anon_ns(mnt
->mnt_ns
)))
4471 * First, we get the mount tree in a shape where we can change mount
4472 * properties without failure. If we succeeded to do so we commit all
4473 * changes and if we failed we clean up.
4475 err
= mount_setattr_prepare(kattr
, mnt
);
4477 mount_setattr_commit(kattr
, mnt
);
4480 unlock_mount_hash();
4482 if (kattr
->propagation
) {
4484 cleanup_group_ids(mnt
, NULL
);
4491 static int build_mount_idmapped(const struct mount_attr
*attr
, size_t usize
,
4492 struct mount_kattr
*kattr
, unsigned int flags
)
4495 struct ns_common
*ns
;
4496 struct user_namespace
*mnt_userns
;
4499 if (!((attr
->attr_set
| attr
->attr_clr
) & MOUNT_ATTR_IDMAP
))
4503 * We currently do not support clearing an idmapped mount. If this ever
4504 * is a use-case we can revisit this but for now let's keep it simple
4507 if (attr
->attr_clr
& MOUNT_ATTR_IDMAP
)
4510 if (attr
->userns_fd
> INT_MAX
)
4513 f
= fdget(attr
->userns_fd
);
4517 if (!proc_ns_file(f
.file
)) {
4522 ns
= get_proc_ns(file_inode(f
.file
));
4523 if (ns
->ops
->type
!= CLONE_NEWUSER
) {
4529 * The initial idmapping cannot be used to create an idmapped
4530 * mount. We use the initial idmapping as an indicator of a mount
4531 * that is not idmapped. It can simply be passed into helpers that
4532 * are aware of idmapped mounts as a convenient shortcut. A user
4533 * can just create a dedicated identity mapping to achieve the same
4536 mnt_userns
= container_of(ns
, struct user_namespace
, ns
);
4537 if (mnt_userns
== &init_user_ns
) {
4542 /* We're not controlling the target namespace. */
4543 if (!ns_capable(mnt_userns
, CAP_SYS_ADMIN
)) {
4548 kattr
->mnt_userns
= get_user_ns(mnt_userns
);
4555 static int build_mount_kattr(const struct mount_attr
*attr
, size_t usize
,
4556 struct mount_kattr
*kattr
, unsigned int flags
)
4558 unsigned int lookup_flags
= LOOKUP_AUTOMOUNT
| LOOKUP_FOLLOW
;
4560 if (flags
& AT_NO_AUTOMOUNT
)
4561 lookup_flags
&= ~LOOKUP_AUTOMOUNT
;
4562 if (flags
& AT_SYMLINK_NOFOLLOW
)
4563 lookup_flags
&= ~LOOKUP_FOLLOW
;
4564 if (flags
& AT_EMPTY_PATH
)
4565 lookup_flags
|= LOOKUP_EMPTY
;
4567 *kattr
= (struct mount_kattr
) {
4568 .lookup_flags
= lookup_flags
,
4569 .recurse
= !!(flags
& AT_RECURSIVE
),
4572 if (attr
->propagation
& ~MOUNT_SETATTR_PROPAGATION_FLAGS
)
4574 if (hweight32(attr
->propagation
& MOUNT_SETATTR_PROPAGATION_FLAGS
) > 1)
4576 kattr
->propagation
= attr
->propagation
;
4578 if ((attr
->attr_set
| attr
->attr_clr
) & ~MOUNT_SETATTR_VALID_FLAGS
)
4581 kattr
->attr_set
= attr_flags_to_mnt_flags(attr
->attr_set
);
4582 kattr
->attr_clr
= attr_flags_to_mnt_flags(attr
->attr_clr
);
4585 * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
4586 * users wanting to transition to a different atime setting cannot
4587 * simply specify the atime setting in @attr_set, but must also
4588 * specify MOUNT_ATTR__ATIME in the @attr_clr field.
4589 * So ensure that MOUNT_ATTR__ATIME can't be partially set in
4590 * @attr_clr and that @attr_set can't have any atime bits set if
4591 * MOUNT_ATTR__ATIME isn't set in @attr_clr.
4593 if (attr
->attr_clr
& MOUNT_ATTR__ATIME
) {
4594 if ((attr
->attr_clr
& MOUNT_ATTR__ATIME
) != MOUNT_ATTR__ATIME
)
4598 * Clear all previous time settings as they are mutually
4601 kattr
->attr_clr
|= MNT_RELATIME
| MNT_NOATIME
;
4602 switch (attr
->attr_set
& MOUNT_ATTR__ATIME
) {
4603 case MOUNT_ATTR_RELATIME
:
4604 kattr
->attr_set
|= MNT_RELATIME
;
4606 case MOUNT_ATTR_NOATIME
:
4607 kattr
->attr_set
|= MNT_NOATIME
;
4609 case MOUNT_ATTR_STRICTATIME
:
4615 if (attr
->attr_set
& MOUNT_ATTR__ATIME
)
4619 return build_mount_idmapped(attr
, usize
, kattr
, flags
);
4622 static void finish_mount_kattr(struct mount_kattr
*kattr
)
4624 put_user_ns(kattr
->mnt_userns
);
4625 kattr
->mnt_userns
= NULL
;
4627 if (kattr
->mnt_idmap
)
4628 mnt_idmap_put(kattr
->mnt_idmap
);
4631 SYSCALL_DEFINE5(mount_setattr
, int, dfd
, const char __user
*, path
,
4632 unsigned int, flags
, struct mount_attr __user
*, uattr
,
4637 struct mount_attr attr
;
4638 struct mount_kattr kattr
;
4640 BUILD_BUG_ON(sizeof(struct mount_attr
) != MOUNT_ATTR_SIZE_VER0
);
4642 if (flags
& ~(AT_EMPTY_PATH
|
4644 AT_SYMLINK_NOFOLLOW
|
4648 if (unlikely(usize
> PAGE_SIZE
))
4650 if (unlikely(usize
< MOUNT_ATTR_SIZE_VER0
))
4656 err
= copy_struct_from_user(&attr
, sizeof(attr
), uattr
, usize
);
4660 /* Don't bother walking through the mounts if this is a nop. */
4661 if (attr
.attr_set
== 0 &&
4662 attr
.attr_clr
== 0 &&
4663 attr
.propagation
== 0)
4666 err
= build_mount_kattr(&attr
, usize
, &kattr
, flags
);
4670 err
= user_path_at(dfd
, path
, kattr
.lookup_flags
, &target
);
4672 err
= do_mount_setattr(&target
, &kattr
);
4675 finish_mount_kattr(&kattr
);
4679 static void __init
init_mount_tree(void)
4681 struct vfsmount
*mnt
;
4683 struct mnt_namespace
*ns
;
4686 mnt
= vfs_kern_mount(&rootfs_fs_type
, 0, "rootfs", NULL
);
4688 panic("Can't create rootfs");
4690 ns
= alloc_mnt_ns(&init_user_ns
, false);
4692 panic("Can't allocate initial namespace");
4693 m
= real_mount(mnt
);
4697 list_add(&m
->mnt_list
, &ns
->list
);
4698 init_task
.nsproxy
->mnt_ns
= ns
;
4702 root
.dentry
= mnt
->mnt_root
;
4703 mnt
->mnt_flags
|= MNT_LOCKED
;
4705 set_fs_pwd(current
->fs
, &root
);
4706 set_fs_root(current
->fs
, &root
);
4709 void __init
mnt_init(void)
4713 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
4714 0, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_ACCOUNT
, NULL
);
4716 mount_hashtable
= alloc_large_system_hash("Mount-cache",
4717 sizeof(struct hlist_head
),
4720 &m_hash_shift
, &m_hash_mask
, 0, 0);
4721 mountpoint_hashtable
= alloc_large_system_hash("Mountpoint-cache",
4722 sizeof(struct hlist_head
),
4725 &mp_hash_shift
, &mp_hash_mask
, 0, 0);
4727 if (!mount_hashtable
|| !mountpoint_hashtable
)
4728 panic("Failed to allocate mount hash table\n");
4734 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
4736 fs_kobj
= kobject_create_and_add("fs", NULL
);
4738 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
4744 void put_mnt_ns(struct mnt_namespace
*ns
)
4746 if (!refcount_dec_and_test(&ns
->ns
.count
))
4748 drop_collected_mounts(&ns
->root
->mnt
);
4752 struct vfsmount
*kern_mount(struct file_system_type
*type
)
4754 struct vfsmount
*mnt
;
4755 mnt
= vfs_kern_mount(type
, SB_KERNMOUNT
, type
->name
, NULL
);
4758 * it is a longterm mount, don't release mnt until
4759 * we unmount before file sys is unregistered
4761 real_mount(mnt
)->mnt_ns
= MNT_NS_INTERNAL
;
4765 EXPORT_SYMBOL_GPL(kern_mount
);
4767 void kern_unmount(struct vfsmount
*mnt
)
4769 /* release long term mount so mount point can be released */
4771 mnt_make_shortterm(mnt
);
4772 synchronize_rcu(); /* yecchhh... */
4776 EXPORT_SYMBOL(kern_unmount
);
4778 void kern_unmount_array(struct vfsmount
*mnt
[], unsigned int num
)
4782 for (i
= 0; i
< num
; i
++)
4783 mnt_make_shortterm(mnt
[i
]);
4784 synchronize_rcu_expedited();
4785 for (i
= 0; i
< num
; i
++)
4788 EXPORT_SYMBOL(kern_unmount_array
);
4790 bool our_mnt(struct vfsmount
*mnt
)
4792 return check_mnt(real_mount(mnt
));
4795 bool current_chrooted(void)
4797 /* Does the current process have a non-standard root */
4798 struct path ns_root
;
4799 struct path fs_root
;
4802 /* Find the namespace root */
4803 ns_root
.mnt
= ¤t
->nsproxy
->mnt_ns
->root
->mnt
;
4804 ns_root
.dentry
= ns_root
.mnt
->mnt_root
;
4806 while (d_mountpoint(ns_root
.dentry
) && follow_down_one(&ns_root
))
4809 get_fs_root(current
->fs
, &fs_root
);
4811 chrooted
= !path_equal(&fs_root
, &ns_root
);
4819 static bool mnt_already_visible(struct mnt_namespace
*ns
,
4820 const struct super_block
*sb
,
4823 int new_flags
= *new_mnt_flags
;
4825 bool visible
= false;
4827 down_read(&namespace_sem
);
4829 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
4830 struct mount
*child
;
4833 if (mnt_is_cursor(mnt
))
4836 if (mnt
->mnt
.mnt_sb
->s_type
!= sb
->s_type
)
4839 /* This mount is not fully visible if it's root directory
4840 * is not the root directory of the filesystem.
4842 if (mnt
->mnt
.mnt_root
!= mnt
->mnt
.mnt_sb
->s_root
)
4845 /* A local view of the mount flags */
4846 mnt_flags
= mnt
->mnt
.mnt_flags
;
4848 /* Don't miss readonly hidden in the superblock flags */
4849 if (sb_rdonly(mnt
->mnt
.mnt_sb
))
4850 mnt_flags
|= MNT_LOCK_READONLY
;
4852 /* Verify the mount flags are equal to or more permissive
4853 * than the proposed new mount.
4855 if ((mnt_flags
& MNT_LOCK_READONLY
) &&
4856 !(new_flags
& MNT_READONLY
))
4858 if ((mnt_flags
& MNT_LOCK_ATIME
) &&
4859 ((mnt_flags
& MNT_ATIME_MASK
) != (new_flags
& MNT_ATIME_MASK
)))
4862 /* This mount is not fully visible if there are any
4863 * locked child mounts that cover anything except for
4864 * empty directories.
4866 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
4867 struct inode
*inode
= child
->mnt_mountpoint
->d_inode
;
4868 /* Only worry about locked mounts */
4869 if (!(child
->mnt
.mnt_flags
& MNT_LOCKED
))
4871 /* Is the directory permanetly empty? */
4872 if (!is_empty_dir_inode(inode
))
4875 /* Preserve the locked attributes */
4876 *new_mnt_flags
|= mnt_flags
& (MNT_LOCK_READONLY
| \
4884 up_read(&namespace_sem
);
4888 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
)
4890 const unsigned long required_iflags
= SB_I_NOEXEC
| SB_I_NODEV
;
4891 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
4892 unsigned long s_iflags
;
4894 if (ns
->user_ns
== &init_user_ns
)
4897 /* Can this filesystem be too revealing? */
4898 s_iflags
= sb
->s_iflags
;
4899 if (!(s_iflags
& SB_I_USERNS_VISIBLE
))
4902 if ((s_iflags
& required_iflags
) != required_iflags
) {
4903 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
4908 return !mnt_already_visible(ns
, sb
, new_mnt_flags
);
4911 bool mnt_may_suid(struct vfsmount
*mnt
)
4914 * Foreign mounts (accessed via fchdir or through /proc
4915 * symlinks) are always treated as if they are nosuid. This
4916 * prevents namespaces from trusting potentially unsafe
4917 * suid/sgid bits, file caps, or security labels that originate
4918 * in other namespaces.
4920 return !(mnt
->mnt_flags
& MNT_NOSUID
) && check_mnt(real_mount(mnt
)) &&
4921 current_in_userns(mnt
->mnt_sb
->s_user_ns
);
4924 static struct ns_common
*mntns_get(struct task_struct
*task
)
4926 struct ns_common
*ns
= NULL
;
4927 struct nsproxy
*nsproxy
;
4930 nsproxy
= task
->nsproxy
;
4932 ns
= &nsproxy
->mnt_ns
->ns
;
4933 get_mnt_ns(to_mnt_ns(ns
));
4940 static void mntns_put(struct ns_common
*ns
)
4942 put_mnt_ns(to_mnt_ns(ns
));
4945 static int mntns_install(struct nsset
*nsset
, struct ns_common
*ns
)
4947 struct nsproxy
*nsproxy
= nsset
->nsproxy
;
4948 struct fs_struct
*fs
= nsset
->fs
;
4949 struct mnt_namespace
*mnt_ns
= to_mnt_ns(ns
), *old_mnt_ns
;
4950 struct user_namespace
*user_ns
= nsset
->cred
->user_ns
;
4954 if (!ns_capable(mnt_ns
->user_ns
, CAP_SYS_ADMIN
) ||
4955 !ns_capable(user_ns
, CAP_SYS_CHROOT
) ||
4956 !ns_capable(user_ns
, CAP_SYS_ADMIN
))
4959 if (is_anon_ns(mnt_ns
))
4966 old_mnt_ns
= nsproxy
->mnt_ns
;
4967 nsproxy
->mnt_ns
= mnt_ns
;
4970 err
= vfs_path_lookup(mnt_ns
->root
->mnt
.mnt_root
, &mnt_ns
->root
->mnt
,
4971 "/", LOOKUP_DOWN
, &root
);
4973 /* revert to old namespace */
4974 nsproxy
->mnt_ns
= old_mnt_ns
;
4979 put_mnt_ns(old_mnt_ns
);
4981 /* Update the pwd and root */
4982 set_fs_pwd(fs
, &root
);
4983 set_fs_root(fs
, &root
);
4989 static struct user_namespace
*mntns_owner(struct ns_common
*ns
)
4991 return to_mnt_ns(ns
)->user_ns
;
4994 const struct proc_ns_operations mntns_operations
= {
4996 .type
= CLONE_NEWNS
,
4999 .install
= mntns_install
,
5000 .owner
= mntns_owner
,
5003 #ifdef CONFIG_SYSCTL
5004 static struct ctl_table fs_namespace_sysctls
[] = {
5006 .procname
= "mount-max",
5007 .data
= &sysctl_mount_max
,
5008 .maxlen
= sizeof(unsigned int),
5010 .proc_handler
= proc_dointvec_minmax
,
5011 .extra1
= SYSCTL_ONE
,
5016 static int __init
init_fs_namespace_sysctls(void)
5018 register_sysctl_init("fs", fs_namespace_sysctls
);
5021 fs_initcall(init_fs_namespace_sysctls
);
5023 #endif /* CONFIG_SYSCTL */