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/task_work.h>
29 #include <linux/sched/task.h>
30 #include <uapi/linux/mount.h>
31 #include <linux/fs_context.h>
32 #include <linux/shmem_fs.h>
37 /* Maximum number of mounts in a mount namespace */
38 unsigned int sysctl_mount_max __read_mostly
= 100000;
40 static unsigned int m_hash_mask __read_mostly
;
41 static unsigned int m_hash_shift __read_mostly
;
42 static unsigned int mp_hash_mask __read_mostly
;
43 static unsigned int mp_hash_shift __read_mostly
;
45 static __initdata
unsigned long mhash_entries
;
46 static int __init
set_mhash_entries(char *str
)
50 mhash_entries
= simple_strtoul(str
, &str
, 0);
53 __setup("mhash_entries=", set_mhash_entries
);
55 static __initdata
unsigned long mphash_entries
;
56 static int __init
set_mphash_entries(char *str
)
60 mphash_entries
= simple_strtoul(str
, &str
, 0);
63 __setup("mphash_entries=", set_mphash_entries
);
66 static DEFINE_IDA(mnt_id_ida
);
67 static DEFINE_IDA(mnt_group_ida
);
69 static struct hlist_head
*mount_hashtable __read_mostly
;
70 static struct hlist_head
*mountpoint_hashtable __read_mostly
;
71 static struct kmem_cache
*mnt_cache __read_mostly
;
72 static DECLARE_RWSEM(namespace_sem
);
73 static HLIST_HEAD(unmounted
); /* protected by namespace_sem */
74 static LIST_HEAD(ex_mountpoints
); /* protected by namespace_sem */
77 struct kobject
*fs_kobj
;
78 EXPORT_SYMBOL_GPL(fs_kobj
);
81 * vfsmount lock may be taken for read to prevent changes to the
82 * vfsmount hash, ie. during mountpoint lookups or walking back
85 * It should be taken for write in all cases where the vfsmount
86 * tree or hash is modified or when a vfsmount structure is modified.
88 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(mount_lock
);
90 static inline struct hlist_head
*m_hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
92 unsigned long tmp
= ((unsigned long)mnt
/ L1_CACHE_BYTES
);
93 tmp
+= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
94 tmp
= tmp
+ (tmp
>> m_hash_shift
);
95 return &mount_hashtable
[tmp
& m_hash_mask
];
98 static inline struct hlist_head
*mp_hash(struct dentry
*dentry
)
100 unsigned long tmp
= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
101 tmp
= tmp
+ (tmp
>> mp_hash_shift
);
102 return &mountpoint_hashtable
[tmp
& mp_hash_mask
];
105 static int mnt_alloc_id(struct mount
*mnt
)
107 int res
= ida_alloc(&mnt_id_ida
, GFP_KERNEL
);
115 static void mnt_free_id(struct mount
*mnt
)
117 ida_free(&mnt_id_ida
, mnt
->mnt_id
);
121 * Allocate a new peer group ID
123 static int mnt_alloc_group_id(struct mount
*mnt
)
125 int res
= ida_alloc_min(&mnt_group_ida
, 1, GFP_KERNEL
);
129 mnt
->mnt_group_id
= res
;
134 * Release a peer group ID
136 void mnt_release_group_id(struct mount
*mnt
)
138 ida_free(&mnt_group_ida
, mnt
->mnt_group_id
);
139 mnt
->mnt_group_id
= 0;
143 * vfsmount lock must be held for read
145 static inline void mnt_add_count(struct mount
*mnt
, int n
)
148 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, n
);
157 * vfsmount lock must be held for write
159 int mnt_get_count(struct mount
*mnt
)
165 for_each_possible_cpu(cpu
) {
166 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_count
;
171 return mnt
->mnt_count
;
175 static struct mount
*alloc_vfsmnt(const char *name
)
177 struct mount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
181 err
= mnt_alloc_id(mnt
);
186 mnt
->mnt_devname
= kstrdup_const(name
, GFP_KERNEL
);
187 if (!mnt
->mnt_devname
)
192 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
194 goto out_free_devname
;
196 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
199 mnt
->mnt_writers
= 0;
202 INIT_HLIST_NODE(&mnt
->mnt_hash
);
203 INIT_LIST_HEAD(&mnt
->mnt_child
);
204 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
205 INIT_LIST_HEAD(&mnt
->mnt_list
);
206 INIT_LIST_HEAD(&mnt
->mnt_expire
);
207 INIT_LIST_HEAD(&mnt
->mnt_share
);
208 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
209 INIT_LIST_HEAD(&mnt
->mnt_slave
);
210 INIT_HLIST_NODE(&mnt
->mnt_mp_list
);
211 INIT_LIST_HEAD(&mnt
->mnt_umounting
);
212 INIT_HLIST_HEAD(&mnt
->mnt_stuck_children
);
218 kfree_const(mnt
->mnt_devname
);
223 kmem_cache_free(mnt_cache
, mnt
);
228 * Most r/o checks on a fs are for operations that take
229 * discrete amounts of time, like a write() or unlink().
230 * We must keep track of when those operations start
231 * (for permission checks) and when they end, so that
232 * we can determine when writes are able to occur to
236 * __mnt_is_readonly: check whether a mount is read-only
237 * @mnt: the mount to check for its write status
239 * This shouldn't be used directly ouside of the VFS.
240 * It does not guarantee that the filesystem will stay
241 * r/w, just that it is right *now*. This can not and
242 * should not be used in place of IS_RDONLY(inode).
243 * mnt_want/drop_write() will _keep_ the filesystem
246 bool __mnt_is_readonly(struct vfsmount
*mnt
)
248 return (mnt
->mnt_flags
& MNT_READONLY
) || sb_rdonly(mnt
->mnt_sb
);
250 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
252 static inline void mnt_inc_writers(struct mount
*mnt
)
255 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
261 static inline void mnt_dec_writers(struct mount
*mnt
)
264 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
270 static unsigned int mnt_get_writers(struct mount
*mnt
)
273 unsigned int count
= 0;
276 for_each_possible_cpu(cpu
) {
277 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_writers
;
282 return mnt
->mnt_writers
;
286 static int mnt_is_readonly(struct vfsmount
*mnt
)
288 if (mnt
->mnt_sb
->s_readonly_remount
)
290 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
292 return __mnt_is_readonly(mnt
);
296 * Most r/o & frozen checks on a fs are for operations that take discrete
297 * amounts of time, like a write() or unlink(). We must keep track of when
298 * those operations start (for permission checks) and when they end, so that we
299 * can determine when writes are able to occur to a filesystem.
302 * __mnt_want_write - get write access to a mount without freeze protection
303 * @m: the mount on which to take a write
305 * This tells the low-level filesystem that a write is about to be performed to
306 * it, and makes sure that writes are allowed (mnt it read-write) before
307 * returning success. This operation does not protect against filesystem being
308 * frozen. When the write operation is finished, __mnt_drop_write() must be
309 * called. This is effectively a refcount.
311 int __mnt_want_write(struct vfsmount
*m
)
313 struct mount
*mnt
= real_mount(m
);
317 mnt_inc_writers(mnt
);
319 * The store to mnt_inc_writers must be visible before we pass
320 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
321 * incremented count after it has set MNT_WRITE_HOLD.
324 while (READ_ONCE(mnt
->mnt
.mnt_flags
) & MNT_WRITE_HOLD
)
327 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
328 * be set to match its requirements. So we must not load that until
329 * MNT_WRITE_HOLD is cleared.
332 if (mnt_is_readonly(m
)) {
333 mnt_dec_writers(mnt
);
342 * mnt_want_write - get write access to a mount
343 * @m: the mount on which to take a write
345 * This tells the low-level filesystem that a write is about to be performed to
346 * it, and makes sure that writes are allowed (mount is read-write, filesystem
347 * is not frozen) before returning success. When the write operation is
348 * finished, mnt_drop_write() must be called. This is effectively a refcount.
350 int mnt_want_write(struct vfsmount
*m
)
354 sb_start_write(m
->mnt_sb
);
355 ret
= __mnt_want_write(m
);
357 sb_end_write(m
->mnt_sb
);
360 EXPORT_SYMBOL_GPL(mnt_want_write
);
363 * mnt_clone_write - get write access to a mount
364 * @mnt: the mount on which to take a write
366 * This is effectively like mnt_want_write, except
367 * it must only be used to take an extra write reference
368 * on a mountpoint that we already know has a write reference
369 * on it. This allows some optimisation.
371 * After finished, mnt_drop_write must be called as usual to
372 * drop the reference.
374 int mnt_clone_write(struct vfsmount
*mnt
)
376 /* superblock may be r/o */
377 if (__mnt_is_readonly(mnt
))
380 mnt_inc_writers(real_mount(mnt
));
384 EXPORT_SYMBOL_GPL(mnt_clone_write
);
387 * __mnt_want_write_file - get write access to a file's mount
388 * @file: the file who's mount on which to take a write
390 * This is like __mnt_want_write, but it takes a file and can
391 * do some optimisations if the file is open for write already
393 int __mnt_want_write_file(struct file
*file
)
395 if (!(file
->f_mode
& FMODE_WRITER
))
396 return __mnt_want_write(file
->f_path
.mnt
);
398 return mnt_clone_write(file
->f_path
.mnt
);
402 * mnt_want_write_file - get write access to a file's mount
403 * @file: the file who's mount on which to take a write
405 * This is like mnt_want_write, but it takes a file and can
406 * do some optimisations if the file is open for write already
408 int mnt_want_write_file(struct file
*file
)
412 sb_start_write(file_inode(file
)->i_sb
);
413 ret
= __mnt_want_write_file(file
);
415 sb_end_write(file_inode(file
)->i_sb
);
418 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
421 * __mnt_drop_write - give up write access to a mount
422 * @mnt: the mount on which to give up write access
424 * Tells the low-level filesystem that we are done
425 * performing writes to it. Must be matched with
426 * __mnt_want_write() call above.
428 void __mnt_drop_write(struct vfsmount
*mnt
)
431 mnt_dec_writers(real_mount(mnt
));
434 EXPORT_SYMBOL_GPL(__mnt_drop_write
);
437 * mnt_drop_write - give up write access to a mount
438 * @mnt: the mount on which to give up write access
440 * Tells the low-level filesystem that we are done performing writes to it and
441 * also allows filesystem to be frozen again. Must be matched with
442 * mnt_want_write() call above.
444 void mnt_drop_write(struct vfsmount
*mnt
)
446 __mnt_drop_write(mnt
);
447 sb_end_write(mnt
->mnt_sb
);
449 EXPORT_SYMBOL_GPL(mnt_drop_write
);
451 void __mnt_drop_write_file(struct file
*file
)
453 __mnt_drop_write(file
->f_path
.mnt
);
456 void mnt_drop_write_file(struct file
*file
)
458 __mnt_drop_write_file(file
);
459 sb_end_write(file_inode(file
)->i_sb
);
461 EXPORT_SYMBOL(mnt_drop_write_file
);
463 static int mnt_make_readonly(struct mount
*mnt
)
468 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
470 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
471 * should be visible before we do.
476 * With writers on hold, if this value is zero, then there are
477 * definitely no active writers (although held writers may subsequently
478 * increment the count, they'll have to wait, and decrement it after
479 * seeing MNT_READONLY).
481 * It is OK to have counter incremented on one CPU and decremented on
482 * another: the sum will add up correctly. The danger would be when we
483 * sum up each counter, if we read a counter before it is incremented,
484 * but then read another CPU's count which it has been subsequently
485 * decremented from -- we would see more decrements than we should.
486 * MNT_WRITE_HOLD protects against this scenario, because
487 * mnt_want_write first increments count, then smp_mb, then spins on
488 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
489 * we're counting up here.
491 if (mnt_get_writers(mnt
) > 0)
494 mnt
->mnt
.mnt_flags
|= MNT_READONLY
;
496 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
497 * that become unheld will see MNT_READONLY.
500 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
505 static int __mnt_unmake_readonly(struct mount
*mnt
)
508 mnt
->mnt
.mnt_flags
&= ~MNT_READONLY
;
513 int sb_prepare_remount_readonly(struct super_block
*sb
)
518 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
519 if (atomic_long_read(&sb
->s_remove_count
))
523 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
524 if (!(mnt
->mnt
.mnt_flags
& MNT_READONLY
)) {
525 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
527 if (mnt_get_writers(mnt
) > 0) {
533 if (!err
&& atomic_long_read(&sb
->s_remove_count
))
537 sb
->s_readonly_remount
= 1;
540 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
541 if (mnt
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
542 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
549 static void free_vfsmnt(struct mount
*mnt
)
551 kfree_const(mnt
->mnt_devname
);
553 free_percpu(mnt
->mnt_pcp
);
555 kmem_cache_free(mnt_cache
, mnt
);
558 static void delayed_free_vfsmnt(struct rcu_head
*head
)
560 free_vfsmnt(container_of(head
, struct mount
, mnt_rcu
));
563 /* call under rcu_read_lock */
564 int __legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
567 if (read_seqretry(&mount_lock
, seq
))
571 mnt
= real_mount(bastard
);
572 mnt_add_count(mnt
, 1);
573 smp_mb(); // see mntput_no_expire()
574 if (likely(!read_seqretry(&mount_lock
, seq
)))
576 if (bastard
->mnt_flags
& MNT_SYNC_UMOUNT
) {
577 mnt_add_count(mnt
, -1);
581 if (unlikely(bastard
->mnt_flags
& MNT_DOOMED
)) {
582 mnt_add_count(mnt
, -1);
587 /* caller will mntput() */
591 /* call under rcu_read_lock */
592 bool legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
594 int res
= __legitimize_mnt(bastard
, seq
);
597 if (unlikely(res
< 0)) {
606 * find the first mount at @dentry on vfsmount @mnt.
607 * call under rcu_read_lock()
609 struct mount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
611 struct hlist_head
*head
= m_hash(mnt
, dentry
);
614 hlist_for_each_entry_rcu(p
, head
, mnt_hash
)
615 if (&p
->mnt_parent
->mnt
== mnt
&& p
->mnt_mountpoint
== dentry
)
621 * lookup_mnt - Return the first child mount mounted at path
623 * "First" means first mounted chronologically. If you create the
626 * mount /dev/sda1 /mnt
627 * mount /dev/sda2 /mnt
628 * mount /dev/sda3 /mnt
630 * Then lookup_mnt() on the base /mnt dentry in the root mount will
631 * return successively the root dentry and vfsmount of /dev/sda1, then
632 * /dev/sda2, then /dev/sda3, then NULL.
634 * lookup_mnt takes a reference to the found vfsmount.
636 struct vfsmount
*lookup_mnt(const struct path
*path
)
638 struct mount
*child_mnt
;
644 seq
= read_seqbegin(&mount_lock
);
645 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
);
646 m
= child_mnt
? &child_mnt
->mnt
: NULL
;
647 } while (!legitimize_mnt(m
, seq
));
652 static inline void lock_ns_list(struct mnt_namespace
*ns
)
654 spin_lock(&ns
->ns_lock
);
657 static inline void unlock_ns_list(struct mnt_namespace
*ns
)
659 spin_unlock(&ns
->ns_lock
);
662 static inline bool mnt_is_cursor(struct mount
*mnt
)
664 return mnt
->mnt
.mnt_flags
& MNT_CURSOR
;
668 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
669 * current mount namespace.
671 * The common case is dentries are not mountpoints at all and that
672 * test is handled inline. For the slow case when we are actually
673 * dealing with a mountpoint of some kind, walk through all of the
674 * mounts in the current mount namespace and test to see if the dentry
677 * The mount_hashtable is not usable in the context because we
678 * need to identify all mounts that may be in the current mount
679 * namespace not just a mount that happens to have some specified
682 bool __is_local_mountpoint(struct dentry
*dentry
)
684 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
686 bool is_covered
= false;
688 down_read(&namespace_sem
);
690 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
691 if (mnt_is_cursor(mnt
))
693 is_covered
= (mnt
->mnt_mountpoint
== dentry
);
698 up_read(&namespace_sem
);
703 static struct mountpoint
*lookup_mountpoint(struct dentry
*dentry
)
705 struct hlist_head
*chain
= mp_hash(dentry
);
706 struct mountpoint
*mp
;
708 hlist_for_each_entry(mp
, chain
, m_hash
) {
709 if (mp
->m_dentry
== dentry
) {
717 static struct mountpoint
*get_mountpoint(struct dentry
*dentry
)
719 struct mountpoint
*mp
, *new = NULL
;
722 if (d_mountpoint(dentry
)) {
723 /* might be worth a WARN_ON() */
724 if (d_unlinked(dentry
))
725 return ERR_PTR(-ENOENT
);
727 read_seqlock_excl(&mount_lock
);
728 mp
= lookup_mountpoint(dentry
);
729 read_sequnlock_excl(&mount_lock
);
735 new = kmalloc(sizeof(struct mountpoint
), GFP_KERNEL
);
737 return ERR_PTR(-ENOMEM
);
740 /* Exactly one processes may set d_mounted */
741 ret
= d_set_mounted(dentry
);
743 /* Someone else set d_mounted? */
747 /* The dentry is not available as a mountpoint? */
752 /* Add the new mountpoint to the hash table */
753 read_seqlock_excl(&mount_lock
);
754 new->m_dentry
= dget(dentry
);
756 hlist_add_head(&new->m_hash
, mp_hash(dentry
));
757 INIT_HLIST_HEAD(&new->m_list
);
758 read_sequnlock_excl(&mount_lock
);
768 * vfsmount lock must be held. Additionally, the caller is responsible
769 * for serializing calls for given disposal list.
771 static void __put_mountpoint(struct mountpoint
*mp
, struct list_head
*list
)
773 if (!--mp
->m_count
) {
774 struct dentry
*dentry
= mp
->m_dentry
;
775 BUG_ON(!hlist_empty(&mp
->m_list
));
776 spin_lock(&dentry
->d_lock
);
777 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
778 spin_unlock(&dentry
->d_lock
);
779 dput_to_list(dentry
, list
);
780 hlist_del(&mp
->m_hash
);
785 /* called with namespace_lock and vfsmount lock */
786 static void put_mountpoint(struct mountpoint
*mp
)
788 __put_mountpoint(mp
, &ex_mountpoints
);
791 static inline int check_mnt(struct mount
*mnt
)
793 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
796 /* for aufs, CONFIG_AUFS_BR_FUSE */
797 int is_current_mnt_ns(struct vfsmount
*mnt
)
799 return check_mnt(real_mount(mnt
));
801 EXPORT_SYMBOL_GPL(is_current_mnt_ns
);
804 * vfsmount lock must be held for write
806 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
810 wake_up_interruptible(&ns
->poll
);
815 * vfsmount lock must be held for write
817 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
819 if (ns
&& ns
->event
!= event
) {
821 wake_up_interruptible(&ns
->poll
);
826 * vfsmount lock must be held for write
828 static struct mountpoint
*unhash_mnt(struct mount
*mnt
)
830 struct mountpoint
*mp
;
831 mnt
->mnt_parent
= mnt
;
832 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
833 list_del_init(&mnt
->mnt_child
);
834 hlist_del_init_rcu(&mnt
->mnt_hash
);
835 hlist_del_init(&mnt
->mnt_mp_list
);
842 * vfsmount lock must be held for write
844 static void umount_mnt(struct mount
*mnt
)
846 put_mountpoint(unhash_mnt(mnt
));
850 * vfsmount lock must be held for write
852 void mnt_set_mountpoint(struct mount
*mnt
,
853 struct mountpoint
*mp
,
854 struct mount
*child_mnt
)
857 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
858 child_mnt
->mnt_mountpoint
= mp
->m_dentry
;
859 child_mnt
->mnt_parent
= mnt
;
860 child_mnt
->mnt_mp
= mp
;
861 hlist_add_head(&child_mnt
->mnt_mp_list
, &mp
->m_list
);
864 static void __attach_mnt(struct mount
*mnt
, struct mount
*parent
)
866 hlist_add_head_rcu(&mnt
->mnt_hash
,
867 m_hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
868 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
872 * vfsmount lock must be held for write
874 static void attach_mnt(struct mount
*mnt
,
875 struct mount
*parent
,
876 struct mountpoint
*mp
)
878 mnt_set_mountpoint(parent
, mp
, mnt
);
879 __attach_mnt(mnt
, parent
);
882 void mnt_change_mountpoint(struct mount
*parent
, struct mountpoint
*mp
, struct mount
*mnt
)
884 struct mountpoint
*old_mp
= mnt
->mnt_mp
;
885 struct mount
*old_parent
= mnt
->mnt_parent
;
887 list_del_init(&mnt
->mnt_child
);
888 hlist_del_init(&mnt
->mnt_mp_list
);
889 hlist_del_init_rcu(&mnt
->mnt_hash
);
891 attach_mnt(mnt
, parent
, mp
);
893 put_mountpoint(old_mp
);
894 mnt_add_count(old_parent
, -1);
898 * vfsmount lock must be held for write
900 static void commit_tree(struct mount
*mnt
)
902 struct mount
*parent
= mnt
->mnt_parent
;
905 struct mnt_namespace
*n
= parent
->mnt_ns
;
907 BUG_ON(parent
== mnt
);
909 list_add_tail(&head
, &mnt
->mnt_list
);
910 list_for_each_entry(m
, &head
, mnt_list
)
913 list_splice(&head
, n
->list
.prev
);
915 n
->mounts
+= n
->pending_mounts
;
916 n
->pending_mounts
= 0;
918 __attach_mnt(mnt
, parent
);
919 touch_mnt_namespace(n
);
922 static struct mount
*next_mnt(struct mount
*p
, struct mount
*root
)
924 struct list_head
*next
= p
->mnt_mounts
.next
;
925 if (next
== &p
->mnt_mounts
) {
929 next
= p
->mnt_child
.next
;
930 if (next
!= &p
->mnt_parent
->mnt_mounts
)
935 return list_entry(next
, struct mount
, mnt_child
);
938 static struct mount
*skip_mnt_tree(struct mount
*p
)
940 struct list_head
*prev
= p
->mnt_mounts
.prev
;
941 while (prev
!= &p
->mnt_mounts
) {
942 p
= list_entry(prev
, struct mount
, mnt_child
);
943 prev
= p
->mnt_mounts
.prev
;
949 * vfs_create_mount - Create a mount for a configured superblock
950 * @fc: The configuration context with the superblock attached
952 * Create a mount to an already configured superblock. If necessary, the
953 * caller should invoke vfs_get_tree() before calling this.
955 * Note that this does not attach the mount to anything.
957 struct vfsmount
*vfs_create_mount(struct fs_context
*fc
)
962 return ERR_PTR(-EINVAL
);
964 mnt
= alloc_vfsmnt(fc
->source
?: "none");
966 return ERR_PTR(-ENOMEM
);
968 if (fc
->sb_flags
& SB_KERNMOUNT
)
969 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
971 atomic_inc(&fc
->root
->d_sb
->s_active
);
972 mnt
->mnt
.mnt_sb
= fc
->root
->d_sb
;
973 mnt
->mnt
.mnt_root
= dget(fc
->root
);
974 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
975 mnt
->mnt_parent
= mnt
;
978 list_add_tail(&mnt
->mnt_instance
, &mnt
->mnt
.mnt_sb
->s_mounts
);
982 EXPORT_SYMBOL(vfs_create_mount
);
984 struct vfsmount
*fc_mount(struct fs_context
*fc
)
986 int err
= vfs_get_tree(fc
);
988 up_write(&fc
->root
->d_sb
->s_umount
);
989 return vfs_create_mount(fc
);
993 EXPORT_SYMBOL(fc_mount
);
995 struct vfsmount
*vfs_kern_mount(struct file_system_type
*type
,
996 int flags
, const char *name
,
999 struct fs_context
*fc
;
1000 struct vfsmount
*mnt
;
1004 return ERR_PTR(-EINVAL
);
1006 fc
= fs_context_for_mount(type
, flags
);
1008 return ERR_CAST(fc
);
1011 ret
= vfs_parse_fs_string(fc
, "source",
1012 name
, strlen(name
));
1014 ret
= parse_monolithic_mount_data(fc
, data
);
1023 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
1026 vfs_submount(const struct dentry
*mountpoint
, struct file_system_type
*type
,
1027 const char *name
, void *data
)
1029 /* Until it is worked out how to pass the user namespace
1030 * through from the parent mount to the submount don't support
1031 * unprivileged mounts with submounts.
1033 if (mountpoint
->d_sb
->s_user_ns
!= &init_user_ns
)
1034 return ERR_PTR(-EPERM
);
1036 return vfs_kern_mount(type
, SB_SUBMOUNT
, name
, data
);
1038 EXPORT_SYMBOL_GPL(vfs_submount
);
1040 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
1043 struct super_block
*sb
= old
->mnt
.mnt_sb
;
1047 mnt
= alloc_vfsmnt(old
->mnt_devname
);
1049 return ERR_PTR(-ENOMEM
);
1051 if (flag
& (CL_SLAVE
| CL_PRIVATE
| CL_SHARED_TO_SLAVE
))
1052 mnt
->mnt_group_id
= 0; /* not a peer of original */
1054 mnt
->mnt_group_id
= old
->mnt_group_id
;
1056 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
1057 err
= mnt_alloc_group_id(mnt
);
1062 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
;
1063 mnt
->mnt
.mnt_flags
&= ~(MNT_WRITE_HOLD
|MNT_MARKED
|MNT_INTERNAL
);
1065 atomic_inc(&sb
->s_active
);
1066 mnt
->mnt
.mnt_sb
= sb
;
1067 mnt
->mnt
.mnt_root
= dget(root
);
1068 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1069 mnt
->mnt_parent
= mnt
;
1071 list_add_tail(&mnt
->mnt_instance
, &sb
->s_mounts
);
1072 unlock_mount_hash();
1074 if ((flag
& CL_SLAVE
) ||
1075 ((flag
& CL_SHARED_TO_SLAVE
) && IS_MNT_SHARED(old
))) {
1076 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
1077 mnt
->mnt_master
= old
;
1078 CLEAR_MNT_SHARED(mnt
);
1079 } else if (!(flag
& CL_PRIVATE
)) {
1080 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
1081 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
1082 if (IS_MNT_SLAVE(old
))
1083 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
1084 mnt
->mnt_master
= old
->mnt_master
;
1086 CLEAR_MNT_SHARED(mnt
);
1088 if (flag
& CL_MAKE_SHARED
)
1089 set_mnt_shared(mnt
);
1091 /* stick the duplicate mount on the same expiry list
1092 * as the original if that was on one */
1093 if (flag
& CL_EXPIRE
) {
1094 if (!list_empty(&old
->mnt_expire
))
1095 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
1103 return ERR_PTR(err
);
1106 static void cleanup_mnt(struct mount
*mnt
)
1108 struct hlist_node
*p
;
1111 * The warning here probably indicates that somebody messed
1112 * up a mnt_want/drop_write() pair. If this happens, the
1113 * filesystem was probably unable to make r/w->r/o transitions.
1114 * The locking used to deal with mnt_count decrement provides barriers,
1115 * so mnt_get_writers() below is safe.
1117 WARN_ON(mnt_get_writers(mnt
));
1118 if (unlikely(mnt
->mnt_pins
.first
))
1120 hlist_for_each_entry_safe(m
, p
, &mnt
->mnt_stuck_children
, mnt_umount
) {
1121 hlist_del(&m
->mnt_umount
);
1124 fsnotify_vfsmount_delete(&mnt
->mnt
);
1125 dput(mnt
->mnt
.mnt_root
);
1126 deactivate_super(mnt
->mnt
.mnt_sb
);
1128 call_rcu(&mnt
->mnt_rcu
, delayed_free_vfsmnt
);
1131 static void __cleanup_mnt(struct rcu_head
*head
)
1133 cleanup_mnt(container_of(head
, struct mount
, mnt_rcu
));
1136 static LLIST_HEAD(delayed_mntput_list
);
1137 static void delayed_mntput(struct work_struct
*unused
)
1139 struct llist_node
*node
= llist_del_all(&delayed_mntput_list
);
1140 struct mount
*m
, *t
;
1142 llist_for_each_entry_safe(m
, t
, node
, mnt_llist
)
1145 static DECLARE_DELAYED_WORK(delayed_mntput_work
, delayed_mntput
);
1147 static void mntput_no_expire(struct mount
*mnt
)
1153 if (likely(READ_ONCE(mnt
->mnt_ns
))) {
1155 * Since we don't do lock_mount_hash() here,
1156 * ->mnt_ns can change under us. However, if it's
1157 * non-NULL, then there's a reference that won't
1158 * be dropped until after an RCU delay done after
1159 * turning ->mnt_ns NULL. So if we observe it
1160 * non-NULL under rcu_read_lock(), the reference
1161 * we are dropping is not the final one.
1163 mnt_add_count(mnt
, -1);
1169 * make sure that if __legitimize_mnt() has not seen us grab
1170 * mount_lock, we'll see their refcount increment here.
1173 mnt_add_count(mnt
, -1);
1174 count
= mnt_get_count(mnt
);
1178 unlock_mount_hash();
1181 if (unlikely(mnt
->mnt
.mnt_flags
& MNT_DOOMED
)) {
1183 unlock_mount_hash();
1186 mnt
->mnt
.mnt_flags
|= MNT_DOOMED
;
1189 list_del(&mnt
->mnt_instance
);
1191 if (unlikely(!list_empty(&mnt
->mnt_mounts
))) {
1192 struct mount
*p
, *tmp
;
1193 list_for_each_entry_safe(p
, tmp
, &mnt
->mnt_mounts
, mnt_child
) {
1194 __put_mountpoint(unhash_mnt(p
), &list
);
1195 hlist_add_head(&p
->mnt_umount
, &mnt
->mnt_stuck_children
);
1198 unlock_mount_hash();
1199 shrink_dentry_list(&list
);
1201 if (likely(!(mnt
->mnt
.mnt_flags
& MNT_INTERNAL
))) {
1202 struct task_struct
*task
= current
;
1203 if (likely(!(task
->flags
& PF_KTHREAD
))) {
1204 init_task_work(&mnt
->mnt_rcu
, __cleanup_mnt
);
1205 if (!task_work_add(task
, &mnt
->mnt_rcu
, TWA_RESUME
))
1208 if (llist_add(&mnt
->mnt_llist
, &delayed_mntput_list
))
1209 schedule_delayed_work(&delayed_mntput_work
, 1);
1215 void mntput(struct vfsmount
*mnt
)
1218 struct mount
*m
= real_mount(mnt
);
1219 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1220 if (unlikely(m
->mnt_expiry_mark
))
1221 m
->mnt_expiry_mark
= 0;
1222 mntput_no_expire(m
);
1225 EXPORT_SYMBOL(mntput
);
1227 struct vfsmount
*mntget(struct vfsmount
*mnt
)
1230 mnt_add_count(real_mount(mnt
), 1);
1233 EXPORT_SYMBOL(mntget
);
1235 /* path_is_mountpoint() - Check if path is a mount in the current
1238 * d_mountpoint() can only be used reliably to establish if a dentry is
1239 * not mounted in any namespace and that common case is handled inline.
1240 * d_mountpoint() isn't aware of the possibility there may be multiple
1241 * mounts using a given dentry in a different namespace. This function
1242 * checks if the passed in path is a mountpoint rather than the dentry
1245 bool path_is_mountpoint(const struct path
*path
)
1250 if (!d_mountpoint(path
->dentry
))
1255 seq
= read_seqbegin(&mount_lock
);
1256 res
= __path_is_mountpoint(path
);
1257 } while (read_seqretry(&mount_lock
, seq
));
1262 EXPORT_SYMBOL(path_is_mountpoint
);
1264 struct vfsmount
*mnt_clone_internal(const struct path
*path
)
1267 p
= clone_mnt(real_mount(path
->mnt
), path
->dentry
, CL_PRIVATE
);
1270 p
->mnt
.mnt_flags
|= MNT_INTERNAL
;
1274 #ifdef CONFIG_PROC_FS
1275 static struct mount
*mnt_list_next(struct mnt_namespace
*ns
,
1276 struct list_head
*p
)
1278 struct mount
*mnt
, *ret
= NULL
;
1281 list_for_each_continue(p
, &ns
->list
) {
1282 mnt
= list_entry(p
, typeof(*mnt
), mnt_list
);
1283 if (!mnt_is_cursor(mnt
)) {
1293 /* iterator; we want it to have access to namespace_sem, thus here... */
1294 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
1296 struct proc_mounts
*p
= m
->private;
1297 struct list_head
*prev
;
1299 down_read(&namespace_sem
);
1301 prev
= &p
->ns
->list
;
1303 prev
= &p
->cursor
.mnt_list
;
1305 /* Read after we'd reached the end? */
1306 if (list_empty(prev
))
1310 return mnt_list_next(p
->ns
, prev
);
1313 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
1315 struct proc_mounts
*p
= m
->private;
1316 struct mount
*mnt
= v
;
1319 return mnt_list_next(p
->ns
, &mnt
->mnt_list
);
1322 static void m_stop(struct seq_file
*m
, void *v
)
1324 struct proc_mounts
*p
= m
->private;
1325 struct mount
*mnt
= v
;
1327 lock_ns_list(p
->ns
);
1329 list_move_tail(&p
->cursor
.mnt_list
, &mnt
->mnt_list
);
1331 list_del_init(&p
->cursor
.mnt_list
);
1332 unlock_ns_list(p
->ns
);
1333 up_read(&namespace_sem
);
1336 static int m_show(struct seq_file
*m
, void *v
)
1338 struct proc_mounts
*p
= m
->private;
1339 struct mount
*r
= v
;
1340 return p
->show(m
, &r
->mnt
);
1343 const struct seq_operations mounts_op
= {
1350 void mnt_cursor_del(struct mnt_namespace
*ns
, struct mount
*cursor
)
1352 down_read(&namespace_sem
);
1354 list_del(&cursor
->mnt_list
);
1356 up_read(&namespace_sem
);
1358 #endif /* CONFIG_PROC_FS */
1361 * may_umount_tree - check if a mount tree is busy
1362 * @mnt: root of mount tree
1364 * This is called to check if a tree of mounts has any
1365 * open files, pwds, chroots or sub mounts that are
1368 int may_umount_tree(struct vfsmount
*m
)
1370 struct mount
*mnt
= real_mount(m
);
1371 int actual_refs
= 0;
1372 int minimum_refs
= 0;
1376 /* write lock needed for mnt_get_count */
1378 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1379 actual_refs
+= mnt_get_count(p
);
1382 unlock_mount_hash();
1384 if (actual_refs
> minimum_refs
)
1390 EXPORT_SYMBOL(may_umount_tree
);
1393 * may_umount - check if a mount point is busy
1394 * @mnt: root of mount
1396 * This is called to check if a mount point has any
1397 * open files, pwds, chroots or sub mounts. If the
1398 * mount has sub mounts this will return busy
1399 * regardless of whether the sub mounts are busy.
1401 * Doesn't take quota and stuff into account. IOW, in some cases it will
1402 * give false negatives. The main reason why it's here is that we need
1403 * a non-destructive way to look for easily umountable filesystems.
1405 int may_umount(struct vfsmount
*mnt
)
1408 down_read(&namespace_sem
);
1410 if (propagate_mount_busy(real_mount(mnt
), 2))
1412 unlock_mount_hash();
1413 up_read(&namespace_sem
);
1417 EXPORT_SYMBOL(may_umount
);
1419 static void namespace_unlock(void)
1421 struct hlist_head head
;
1422 struct hlist_node
*p
;
1426 hlist_move_list(&unmounted
, &head
);
1427 list_splice_init(&ex_mountpoints
, &list
);
1429 up_write(&namespace_sem
);
1431 shrink_dentry_list(&list
);
1433 if (likely(hlist_empty(&head
)))
1436 synchronize_rcu_expedited();
1438 hlist_for_each_entry_safe(m
, p
, &head
, mnt_umount
) {
1439 hlist_del(&m
->mnt_umount
);
1444 static inline void namespace_lock(void)
1446 down_write(&namespace_sem
);
1449 enum umount_tree_flags
{
1451 UMOUNT_PROPAGATE
= 2,
1452 UMOUNT_CONNECTED
= 4,
1455 static bool disconnect_mount(struct mount
*mnt
, enum umount_tree_flags how
)
1457 /* Leaving mounts connected is only valid for lazy umounts */
1458 if (how
& UMOUNT_SYNC
)
1461 /* A mount without a parent has nothing to be connected to */
1462 if (!mnt_has_parent(mnt
))
1465 /* Because the reference counting rules change when mounts are
1466 * unmounted and connected, umounted mounts may not be
1467 * connected to mounted mounts.
1469 if (!(mnt
->mnt_parent
->mnt
.mnt_flags
& MNT_UMOUNT
))
1472 /* Has it been requested that the mount remain connected? */
1473 if (how
& UMOUNT_CONNECTED
)
1476 /* Is the mount locked such that it needs to remain connected? */
1477 if (IS_MNT_LOCKED(mnt
))
1480 /* By default disconnect the mount */
1485 * mount_lock must be held
1486 * namespace_sem must be held for write
1488 static void umount_tree(struct mount
*mnt
, enum umount_tree_flags how
)
1490 LIST_HEAD(tmp_list
);
1493 if (how
& UMOUNT_PROPAGATE
)
1494 propagate_mount_unlock(mnt
);
1496 /* Gather the mounts to umount */
1497 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1498 p
->mnt
.mnt_flags
|= MNT_UMOUNT
;
1499 list_move(&p
->mnt_list
, &tmp_list
);
1502 /* Hide the mounts from mnt_mounts */
1503 list_for_each_entry(p
, &tmp_list
, mnt_list
) {
1504 list_del_init(&p
->mnt_child
);
1507 /* Add propogated mounts to the tmp_list */
1508 if (how
& UMOUNT_PROPAGATE
)
1509 propagate_umount(&tmp_list
);
1511 while (!list_empty(&tmp_list
)) {
1512 struct mnt_namespace
*ns
;
1514 p
= list_first_entry(&tmp_list
, struct mount
, mnt_list
);
1515 list_del_init(&p
->mnt_expire
);
1516 list_del_init(&p
->mnt_list
);
1520 __touch_mnt_namespace(ns
);
1523 if (how
& UMOUNT_SYNC
)
1524 p
->mnt
.mnt_flags
|= MNT_SYNC_UMOUNT
;
1526 disconnect
= disconnect_mount(p
, how
);
1527 if (mnt_has_parent(p
)) {
1528 mnt_add_count(p
->mnt_parent
, -1);
1530 /* Don't forget about p */
1531 list_add_tail(&p
->mnt_child
, &p
->mnt_parent
->mnt_mounts
);
1536 change_mnt_propagation(p
, MS_PRIVATE
);
1538 hlist_add_head(&p
->mnt_umount
, &unmounted
);
1542 static void shrink_submounts(struct mount
*mnt
);
1544 static int do_umount_root(struct super_block
*sb
)
1548 down_write(&sb
->s_umount
);
1549 if (!sb_rdonly(sb
)) {
1550 struct fs_context
*fc
;
1552 fc
= fs_context_for_reconfigure(sb
->s_root
, SB_RDONLY
,
1557 ret
= parse_monolithic_mount_data(fc
, NULL
);
1559 ret
= reconfigure_super(fc
);
1563 up_write(&sb
->s_umount
);
1567 static int do_umount(struct mount
*mnt
, int flags
)
1569 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1572 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1577 * Allow userspace to request a mountpoint be expired rather than
1578 * unmounting unconditionally. Unmount only happens if:
1579 * (1) the mark is already set (the mark is cleared by mntput())
1580 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1582 if (flags
& MNT_EXPIRE
) {
1583 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1584 flags
& (MNT_FORCE
| MNT_DETACH
))
1588 * probably don't strictly need the lock here if we examined
1589 * all race cases, but it's a slowpath.
1592 if (mnt_get_count(mnt
) != 2) {
1593 unlock_mount_hash();
1596 unlock_mount_hash();
1598 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1603 * If we may have to abort operations to get out of this
1604 * mount, and they will themselves hold resources we must
1605 * allow the fs to do things. In the Unix tradition of
1606 * 'Gee thats tricky lets do it in userspace' the umount_begin
1607 * might fail to complete on the first run through as other tasks
1608 * must return, and the like. Thats for the mount program to worry
1609 * about for the moment.
1612 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1613 sb
->s_op
->umount_begin(sb
);
1617 * No sense to grab the lock for this test, but test itself looks
1618 * somewhat bogus. Suggestions for better replacement?
1619 * Ho-hum... In principle, we might treat that as umount + switch
1620 * to rootfs. GC would eventually take care of the old vfsmount.
1621 * Actually it makes sense, especially if rootfs would contain a
1622 * /reboot - static binary that would close all descriptors and
1623 * call reboot(9). Then init(8) could umount root and exec /reboot.
1625 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1627 * Special case for "unmounting" root ...
1628 * we just try to remount it readonly.
1630 if (!ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
))
1632 return do_umount_root(sb
);
1638 /* Recheck MNT_LOCKED with the locks held */
1640 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
1644 if (flags
& MNT_DETACH
) {
1645 if (!list_empty(&mnt
->mnt_list
))
1646 umount_tree(mnt
, UMOUNT_PROPAGATE
);
1649 shrink_submounts(mnt
);
1651 if (!propagate_mount_busy(mnt
, 2)) {
1652 if (!list_empty(&mnt
->mnt_list
))
1653 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
1658 unlock_mount_hash();
1664 * __detach_mounts - lazily unmount all mounts on the specified dentry
1666 * During unlink, rmdir, and d_drop it is possible to loose the path
1667 * to an existing mountpoint, and wind up leaking the mount.
1668 * detach_mounts allows lazily unmounting those mounts instead of
1671 * The caller may hold dentry->d_inode->i_mutex.
1673 void __detach_mounts(struct dentry
*dentry
)
1675 struct mountpoint
*mp
;
1680 mp
= lookup_mountpoint(dentry
);
1685 while (!hlist_empty(&mp
->m_list
)) {
1686 mnt
= hlist_entry(mp
->m_list
.first
, struct mount
, mnt_mp_list
);
1687 if (mnt
->mnt
.mnt_flags
& MNT_UMOUNT
) {
1689 hlist_add_head(&mnt
->mnt_umount
, &unmounted
);
1691 else umount_tree(mnt
, UMOUNT_CONNECTED
);
1695 unlock_mount_hash();
1700 * Is the caller allowed to modify his namespace?
1702 static inline bool may_mount(void)
1704 return ns_capable(current
->nsproxy
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
);
1707 #ifdef CONFIG_MANDATORY_FILE_LOCKING
1708 static inline bool may_mandlock(void)
1710 return capable(CAP_SYS_ADMIN
);
1713 static inline bool may_mandlock(void)
1715 pr_warn("VFS: \"mand\" mount option not supported");
1720 static int can_umount(const struct path
*path
, int flags
)
1722 struct mount
*mnt
= real_mount(path
->mnt
);
1726 if (path
->dentry
!= path
->mnt
->mnt_root
)
1728 if (!check_mnt(mnt
))
1730 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
) /* Check optimistically */
1732 if (flags
& MNT_FORCE
&& !capable(CAP_SYS_ADMIN
))
1737 // caller is responsible for flags being sane
1738 int path_umount(struct path
*path
, int flags
)
1740 struct mount
*mnt
= real_mount(path
->mnt
);
1743 ret
= can_umount(path
, flags
);
1745 ret
= do_umount(mnt
, flags
);
1747 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1749 mntput_no_expire(mnt
);
1753 static int ksys_umount(char __user
*name
, int flags
)
1755 int lookup_flags
= LOOKUP_MOUNTPOINT
;
1759 // basic validity checks done first
1760 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1763 if (!(flags
& UMOUNT_NOFOLLOW
))
1764 lookup_flags
|= LOOKUP_FOLLOW
;
1765 ret
= user_path_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1768 return path_umount(&path
, flags
);
1771 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1773 return ksys_umount(name
, flags
);
1776 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1779 * The 2.0 compatible umount. No flags.
1781 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1783 return ksys_umount(name
, 0);
1788 static bool is_mnt_ns_file(struct dentry
*dentry
)
1790 /* Is this a proxy for a mount namespace? */
1791 return dentry
->d_op
== &ns_dentry_operations
&&
1792 dentry
->d_fsdata
== &mntns_operations
;
1795 static struct mnt_namespace
*to_mnt_ns(struct ns_common
*ns
)
1797 return container_of(ns
, struct mnt_namespace
, ns
);
1800 struct ns_common
*from_mnt_ns(struct mnt_namespace
*mnt
)
1805 static bool mnt_ns_loop(struct dentry
*dentry
)
1807 /* Could bind mounting the mount namespace inode cause a
1808 * mount namespace loop?
1810 struct mnt_namespace
*mnt_ns
;
1811 if (!is_mnt_ns_file(dentry
))
1814 mnt_ns
= to_mnt_ns(get_proc_ns(dentry
->d_inode
));
1815 return current
->nsproxy
->mnt_ns
->seq
>= mnt_ns
->seq
;
1818 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1821 struct mount
*res
, *p
, *q
, *r
, *parent
;
1823 if (!(flag
& CL_COPY_UNBINDABLE
) && IS_MNT_UNBINDABLE(mnt
))
1824 return ERR_PTR(-EINVAL
);
1826 if (!(flag
& CL_COPY_MNT_NS_FILE
) && is_mnt_ns_file(dentry
))
1827 return ERR_PTR(-EINVAL
);
1829 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1833 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1836 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1838 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1841 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1842 if (!(flag
& CL_COPY_UNBINDABLE
) &&
1843 IS_MNT_UNBINDABLE(s
)) {
1844 if (s
->mnt
.mnt_flags
& MNT_LOCKED
) {
1845 /* Both unbindable and locked. */
1846 q
= ERR_PTR(-EPERM
);
1849 s
= skip_mnt_tree(s
);
1853 if (!(flag
& CL_COPY_MNT_NS_FILE
) &&
1854 is_mnt_ns_file(s
->mnt
.mnt_root
)) {
1855 s
= skip_mnt_tree(s
);
1858 while (p
!= s
->mnt_parent
) {
1864 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
1868 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1869 attach_mnt(q
, parent
, p
->mnt_mp
);
1870 unlock_mount_hash();
1877 umount_tree(res
, UMOUNT_SYNC
);
1878 unlock_mount_hash();
1883 /* Caller should check returned pointer for errors */
1885 struct vfsmount
*collect_mounts(const struct path
*path
)
1889 if (!check_mnt(real_mount(path
->mnt
)))
1890 tree
= ERR_PTR(-EINVAL
);
1892 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
1893 CL_COPY_ALL
| CL_PRIVATE
);
1896 return ERR_CAST(tree
);
1900 static void free_mnt_ns(struct mnt_namespace
*);
1901 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*, bool);
1903 void dissolve_on_fput(struct vfsmount
*mnt
)
1905 struct mnt_namespace
*ns
;
1908 ns
= real_mount(mnt
)->mnt_ns
;
1911 umount_tree(real_mount(mnt
), UMOUNT_CONNECTED
);
1915 unlock_mount_hash();
1921 void drop_collected_mounts(struct vfsmount
*mnt
)
1925 umount_tree(real_mount(mnt
), 0);
1926 unlock_mount_hash();
1931 * clone_private_mount - create a private clone of a path
1933 * This creates a new vfsmount, which will be the clone of @path. The new will
1934 * not be attached anywhere in the namespace and will be private (i.e. changes
1935 * to the originating mount won't be propagated into this).
1937 * Release with mntput().
1939 struct vfsmount
*clone_private_mount(const struct path
*path
)
1941 struct mount
*old_mnt
= real_mount(path
->mnt
);
1942 struct mount
*new_mnt
;
1944 if (IS_MNT_UNBINDABLE(old_mnt
))
1945 return ERR_PTR(-EINVAL
);
1947 new_mnt
= clone_mnt(old_mnt
, path
->dentry
, CL_PRIVATE
);
1948 if (IS_ERR(new_mnt
))
1949 return ERR_CAST(new_mnt
);
1951 /* Longterm mount to be removed by kern_unmount*() */
1952 new_mnt
->mnt_ns
= MNT_NS_INTERNAL
;
1954 return &new_mnt
->mnt
;
1956 EXPORT_SYMBOL_GPL(clone_private_mount
);
1958 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1959 struct vfsmount
*root
)
1962 int res
= f(root
, arg
);
1965 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
1966 res
= f(&mnt
->mnt
, arg
);
1972 EXPORT_SYMBOL_GPL(iterate_mounts
);
1974 static void lock_mnt_tree(struct mount
*mnt
)
1978 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1979 int flags
= p
->mnt
.mnt_flags
;
1980 /* Don't allow unprivileged users to change mount flags */
1981 flags
|= MNT_LOCK_ATIME
;
1983 if (flags
& MNT_READONLY
)
1984 flags
|= MNT_LOCK_READONLY
;
1986 if (flags
& MNT_NODEV
)
1987 flags
|= MNT_LOCK_NODEV
;
1989 if (flags
& MNT_NOSUID
)
1990 flags
|= MNT_LOCK_NOSUID
;
1992 if (flags
& MNT_NOEXEC
)
1993 flags
|= MNT_LOCK_NOEXEC
;
1994 /* Don't allow unprivileged users to reveal what is under a mount */
1995 if (list_empty(&p
->mnt_expire
))
1996 flags
|= MNT_LOCKED
;
1997 p
->mnt
.mnt_flags
= flags
;
2001 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
2005 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
2006 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
2007 mnt_release_group_id(p
);
2011 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
2015 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
2016 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
2017 int err
= mnt_alloc_group_id(p
);
2019 cleanup_group_ids(mnt
, p
);
2028 int count_mounts(struct mnt_namespace
*ns
, struct mount
*mnt
)
2030 unsigned int max
= READ_ONCE(sysctl_mount_max
);
2031 unsigned int mounts
= 0, old
, pending
, sum
;
2034 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
2038 pending
= ns
->pending_mounts
;
2039 sum
= old
+ pending
;
2043 (mounts
> (max
- sum
)))
2046 ns
->pending_mounts
= pending
+ mounts
;
2051 * @source_mnt : mount tree to be attached
2052 * @nd : place the mount tree @source_mnt is attached
2053 * @parent_nd : if non-null, detach the source_mnt from its parent and
2054 * store the parent mount and mountpoint dentry.
2055 * (done when source_mnt is moved)
2057 * NOTE: in the table below explains the semantics when a source mount
2058 * of a given type is attached to a destination mount of a given type.
2059 * ---------------------------------------------------------------------------
2060 * | BIND MOUNT OPERATION |
2061 * |**************************************************************************
2062 * | source-->| shared | private | slave | unbindable |
2066 * |**************************************************************************
2067 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
2069 * |non-shared| shared (+) | private | slave (*) | invalid |
2070 * ***************************************************************************
2071 * A bind operation clones the source mount and mounts the clone on the
2072 * destination mount.
2074 * (++) the cloned mount is propagated to all the mounts in the propagation
2075 * tree of the destination mount and the cloned mount is added to
2076 * the peer group of the source mount.
2077 * (+) the cloned mount is created under the destination mount and is marked
2078 * as shared. The cloned mount is added to the peer group of the source
2080 * (+++) the mount is propagated to all the mounts in the propagation tree
2081 * of the destination mount and the cloned mount is made slave
2082 * of the same master as that of the source mount. The cloned mount
2083 * is marked as 'shared and slave'.
2084 * (*) the cloned mount is made a slave of the same master as that of the
2087 * ---------------------------------------------------------------------------
2088 * | MOVE MOUNT OPERATION |
2089 * |**************************************************************************
2090 * | source-->| shared | private | slave | unbindable |
2094 * |**************************************************************************
2095 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2097 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2098 * ***************************************************************************
2100 * (+) the mount is moved to the destination. And is then propagated to
2101 * all the mounts in the propagation tree of the destination mount.
2102 * (+*) the mount is moved to the destination.
2103 * (+++) the mount is moved to the destination and is then propagated to
2104 * all the mounts belonging to the destination mount's propagation tree.
2105 * the mount is marked as 'shared and slave'.
2106 * (*) the mount continues to be a slave at the new location.
2108 * if the source mount is a tree, the operations explained above is
2109 * applied to each mount in the tree.
2110 * Must be called without spinlocks held, since this function can sleep
2113 static int attach_recursive_mnt(struct mount
*source_mnt
,
2114 struct mount
*dest_mnt
,
2115 struct mountpoint
*dest_mp
,
2118 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2119 HLIST_HEAD(tree_list
);
2120 struct mnt_namespace
*ns
= dest_mnt
->mnt_ns
;
2121 struct mountpoint
*smp
;
2122 struct mount
*child
, *p
;
2123 struct hlist_node
*n
;
2126 /* Preallocate a mountpoint in case the new mounts need
2127 * to be tucked under other mounts.
2129 smp
= get_mountpoint(source_mnt
->mnt
.mnt_root
);
2131 return PTR_ERR(smp
);
2133 /* Is there space to add these mounts to the mount namespace? */
2135 err
= count_mounts(ns
, source_mnt
);
2140 if (IS_MNT_SHARED(dest_mnt
)) {
2141 err
= invent_group_ids(source_mnt
, true);
2144 err
= propagate_mnt(dest_mnt
, dest_mp
, source_mnt
, &tree_list
);
2147 goto out_cleanup_ids
;
2148 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
2154 unhash_mnt(source_mnt
);
2155 attach_mnt(source_mnt
, dest_mnt
, dest_mp
);
2156 touch_mnt_namespace(source_mnt
->mnt_ns
);
2158 if (source_mnt
->mnt_ns
) {
2159 /* move from anon - the caller will destroy */
2160 list_del_init(&source_mnt
->mnt_ns
->list
);
2162 mnt_set_mountpoint(dest_mnt
, dest_mp
, source_mnt
);
2163 commit_tree(source_mnt
);
2166 hlist_for_each_entry_safe(child
, n
, &tree_list
, mnt_hash
) {
2168 hlist_del_init(&child
->mnt_hash
);
2169 q
= __lookup_mnt(&child
->mnt_parent
->mnt
,
2170 child
->mnt_mountpoint
);
2172 mnt_change_mountpoint(child
, smp
, q
);
2173 /* Notice when we are propagating across user namespaces */
2174 if (child
->mnt_parent
->mnt_ns
->user_ns
!= user_ns
)
2175 lock_mnt_tree(child
);
2176 child
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2179 put_mountpoint(smp
);
2180 unlock_mount_hash();
2185 while (!hlist_empty(&tree_list
)) {
2186 child
= hlist_entry(tree_list
.first
, struct mount
, mnt_hash
);
2187 child
->mnt_parent
->mnt_ns
->pending_mounts
= 0;
2188 umount_tree(child
, UMOUNT_SYNC
);
2190 unlock_mount_hash();
2191 cleanup_group_ids(source_mnt
, NULL
);
2193 ns
->pending_mounts
= 0;
2195 read_seqlock_excl(&mount_lock
);
2196 put_mountpoint(smp
);
2197 read_sequnlock_excl(&mount_lock
);
2202 static struct mountpoint
*lock_mount(struct path
*path
)
2204 struct vfsmount
*mnt
;
2205 struct dentry
*dentry
= path
->dentry
;
2207 inode_lock(dentry
->d_inode
);
2208 if (unlikely(cant_mount(dentry
))) {
2209 inode_unlock(dentry
->d_inode
);
2210 return ERR_PTR(-ENOENT
);
2213 mnt
= lookup_mnt(path
);
2215 struct mountpoint
*mp
= get_mountpoint(dentry
);
2218 inode_unlock(dentry
->d_inode
);
2224 inode_unlock(path
->dentry
->d_inode
);
2227 dentry
= path
->dentry
= dget(mnt
->mnt_root
);
2231 static void unlock_mount(struct mountpoint
*where
)
2233 struct dentry
*dentry
= where
->m_dentry
;
2235 read_seqlock_excl(&mount_lock
);
2236 put_mountpoint(where
);
2237 read_sequnlock_excl(&mount_lock
);
2240 inode_unlock(dentry
->d_inode
);
2243 static int graft_tree(struct mount
*mnt
, struct mount
*p
, struct mountpoint
*mp
)
2245 if (mnt
->mnt
.mnt_sb
->s_flags
& SB_NOUSER
)
2248 if (d_is_dir(mp
->m_dentry
) !=
2249 d_is_dir(mnt
->mnt
.mnt_root
))
2252 return attach_recursive_mnt(mnt
, p
, mp
, false);
2256 * Sanity check the flags to change_mnt_propagation.
2259 static int flags_to_propagation_type(int ms_flags
)
2261 int type
= ms_flags
& ~(MS_REC
| MS_SILENT
);
2263 /* Fail if any non-propagation flags are set */
2264 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2266 /* Only one propagation flag should be set */
2267 if (!is_power_of_2(type
))
2273 * recursively change the type of the mountpoint.
2275 static int do_change_type(struct path
*path
, int ms_flags
)
2278 struct mount
*mnt
= real_mount(path
->mnt
);
2279 int recurse
= ms_flags
& MS_REC
;
2283 if (path
->dentry
!= path
->mnt
->mnt_root
)
2286 type
= flags_to_propagation_type(ms_flags
);
2291 if (type
== MS_SHARED
) {
2292 err
= invent_group_ids(mnt
, recurse
);
2298 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
2299 change_mnt_propagation(m
, type
);
2300 unlock_mount_hash();
2307 static bool has_locked_children(struct mount
*mnt
, struct dentry
*dentry
)
2309 struct mount
*child
;
2310 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
2311 if (!is_subdir(child
->mnt_mountpoint
, dentry
))
2314 if (child
->mnt
.mnt_flags
& MNT_LOCKED
)
2320 static struct mount
*__do_loopback(struct path
*old_path
, int recurse
)
2322 struct mount
*mnt
= ERR_PTR(-EINVAL
), *old
= real_mount(old_path
->mnt
);
2324 if (IS_MNT_UNBINDABLE(old
))
2327 if (!check_mnt(old
) && old_path
->dentry
->d_op
!= &ns_dentry_operations
)
2330 if (!recurse
&& has_locked_children(old
, old_path
->dentry
))
2334 mnt
= copy_tree(old
, old_path
->dentry
, CL_COPY_MNT_NS_FILE
);
2336 mnt
= clone_mnt(old
, old_path
->dentry
, 0);
2339 mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2345 * do loopback mount.
2347 static int do_loopback(struct path
*path
, const char *old_name
,
2350 struct path old_path
;
2351 struct mount
*mnt
= NULL
, *parent
;
2352 struct mountpoint
*mp
;
2354 if (!old_name
|| !*old_name
)
2356 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
2361 if (mnt_ns_loop(old_path
.dentry
))
2364 mp
= lock_mount(path
);
2370 parent
= real_mount(path
->mnt
);
2371 if (!check_mnt(parent
))
2374 mnt
= __do_loopback(&old_path
, recurse
);
2380 err
= graft_tree(mnt
, parent
, mp
);
2383 umount_tree(mnt
, UMOUNT_SYNC
);
2384 unlock_mount_hash();
2389 path_put(&old_path
);
2393 static struct file
*open_detached_copy(struct path
*path
, bool recursive
)
2395 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2396 struct mnt_namespace
*ns
= alloc_mnt_ns(user_ns
, true);
2397 struct mount
*mnt
, *p
;
2401 return ERR_CAST(ns
);
2404 mnt
= __do_loopback(path
, recursive
);
2408 return ERR_CAST(mnt
);
2412 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2417 list_add_tail(&ns
->list
, &mnt
->mnt_list
);
2419 unlock_mount_hash();
2423 path
->mnt
= &mnt
->mnt
;
2424 file
= dentry_open(path
, O_PATH
, current_cred());
2426 dissolve_on_fput(path
->mnt
);
2428 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
2432 SYSCALL_DEFINE3(open_tree
, int, dfd
, const char __user
*, filename
, unsigned, flags
)
2436 int lookup_flags
= LOOKUP_AUTOMOUNT
| LOOKUP_FOLLOW
;
2437 bool detached
= flags
& OPEN_TREE_CLONE
;
2441 BUILD_BUG_ON(OPEN_TREE_CLOEXEC
!= O_CLOEXEC
);
2443 if (flags
& ~(AT_EMPTY_PATH
| AT_NO_AUTOMOUNT
| AT_RECURSIVE
|
2444 AT_SYMLINK_NOFOLLOW
| OPEN_TREE_CLONE
|
2448 if ((flags
& (AT_RECURSIVE
| OPEN_TREE_CLONE
)) == AT_RECURSIVE
)
2451 if (flags
& AT_NO_AUTOMOUNT
)
2452 lookup_flags
&= ~LOOKUP_AUTOMOUNT
;
2453 if (flags
& AT_SYMLINK_NOFOLLOW
)
2454 lookup_flags
&= ~LOOKUP_FOLLOW
;
2455 if (flags
& AT_EMPTY_PATH
)
2456 lookup_flags
|= LOOKUP_EMPTY
;
2458 if (detached
&& !may_mount())
2461 fd
= get_unused_fd_flags(flags
& O_CLOEXEC
);
2465 error
= user_path_at(dfd
, filename
, lookup_flags
, &path
);
2466 if (unlikely(error
)) {
2467 file
= ERR_PTR(error
);
2470 file
= open_detached_copy(&path
, flags
& AT_RECURSIVE
);
2472 file
= dentry_open(&path
, O_PATH
, current_cred());
2477 return PTR_ERR(file
);
2479 fd_install(fd
, file
);
2484 * Don't allow locked mount flags to be cleared.
2486 * No locks need to be held here while testing the various MNT_LOCK
2487 * flags because those flags can never be cleared once they are set.
2489 static bool can_change_locked_flags(struct mount
*mnt
, unsigned int mnt_flags
)
2491 unsigned int fl
= mnt
->mnt
.mnt_flags
;
2493 if ((fl
& MNT_LOCK_READONLY
) &&
2494 !(mnt_flags
& MNT_READONLY
))
2497 if ((fl
& MNT_LOCK_NODEV
) &&
2498 !(mnt_flags
& MNT_NODEV
))
2501 if ((fl
& MNT_LOCK_NOSUID
) &&
2502 !(mnt_flags
& MNT_NOSUID
))
2505 if ((fl
& MNT_LOCK_NOEXEC
) &&
2506 !(mnt_flags
& MNT_NOEXEC
))
2509 if ((fl
& MNT_LOCK_ATIME
) &&
2510 ((fl
& MNT_ATIME_MASK
) != (mnt_flags
& MNT_ATIME_MASK
)))
2516 static int change_mount_ro_state(struct mount
*mnt
, unsigned int mnt_flags
)
2518 bool readonly_request
= (mnt_flags
& MNT_READONLY
);
2520 if (readonly_request
== __mnt_is_readonly(&mnt
->mnt
))
2523 if (readonly_request
)
2524 return mnt_make_readonly(mnt
);
2526 return __mnt_unmake_readonly(mnt
);
2530 * Update the user-settable attributes on a mount. The caller must hold
2531 * sb->s_umount for writing.
2533 static void set_mount_attributes(struct mount
*mnt
, unsigned int mnt_flags
)
2536 mnt_flags
|= mnt
->mnt
.mnt_flags
& ~MNT_USER_SETTABLE_MASK
;
2537 mnt
->mnt
.mnt_flags
= mnt_flags
;
2538 touch_mnt_namespace(mnt
->mnt_ns
);
2539 unlock_mount_hash();
2542 static void mnt_warn_timestamp_expiry(struct path
*mountpoint
, struct vfsmount
*mnt
)
2544 struct super_block
*sb
= mnt
->mnt_sb
;
2546 if (!__mnt_is_readonly(mnt
) &&
2547 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX
> sb
->s_time_max
)) {
2548 char *buf
= (char *)__get_free_page(GFP_KERNEL
);
2549 char *mntpath
= buf
? d_path(mountpoint
, buf
, PAGE_SIZE
) : ERR_PTR(-ENOMEM
);
2552 time64_to_tm(sb
->s_time_max
, 0, &tm
);
2554 pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n",
2556 is_mounted(mnt
) ? "remounted" : "mounted",
2558 tm
.tm_year
+1900, (unsigned long long)sb
->s_time_max
);
2560 free_page((unsigned long)buf
);
2565 * Handle reconfiguration of the mountpoint only without alteration of the
2566 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2569 static int do_reconfigure_mnt(struct path
*path
, unsigned int mnt_flags
)
2571 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2572 struct mount
*mnt
= real_mount(path
->mnt
);
2575 if (!check_mnt(mnt
))
2578 if (path
->dentry
!= mnt
->mnt
.mnt_root
)
2581 if (!can_change_locked_flags(mnt
, mnt_flags
))
2584 down_write(&sb
->s_umount
);
2585 ret
= change_mount_ro_state(mnt
, mnt_flags
);
2587 set_mount_attributes(mnt
, mnt_flags
);
2588 up_write(&sb
->s_umount
);
2590 mnt_warn_timestamp_expiry(path
, &mnt
->mnt
);
2596 * change filesystem flags. dir should be a physical root of filesystem.
2597 * If you've mounted a non-root directory somewhere and want to do remount
2598 * on it - tough luck.
2600 static int do_remount(struct path
*path
, int ms_flags
, int sb_flags
,
2601 int mnt_flags
, void *data
)
2604 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2605 struct mount
*mnt
= real_mount(path
->mnt
);
2606 struct fs_context
*fc
;
2608 if (!check_mnt(mnt
))
2611 if (path
->dentry
!= path
->mnt
->mnt_root
)
2614 if (!can_change_locked_flags(mnt
, mnt_flags
))
2617 fc
= fs_context_for_reconfigure(path
->dentry
, sb_flags
, MS_RMT_MASK
);
2622 err
= parse_monolithic_mount_data(fc
, data
);
2624 down_write(&sb
->s_umount
);
2626 if (ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
)) {
2627 err
= reconfigure_super(fc
);
2629 set_mount_attributes(mnt
, mnt_flags
);
2631 up_write(&sb
->s_umount
);
2634 mnt_warn_timestamp_expiry(path
, &mnt
->mnt
);
2640 static inline int tree_contains_unbindable(struct mount
*mnt
)
2643 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2644 if (IS_MNT_UNBINDABLE(p
))
2651 * Check that there aren't references to earlier/same mount namespaces in the
2652 * specified subtree. Such references can act as pins for mount namespaces
2653 * that aren't checked by the mount-cycle checking code, thereby allowing
2654 * cycles to be made.
2656 static bool check_for_nsfs_mounts(struct mount
*subtree
)
2662 for (p
= subtree
; p
; p
= next_mnt(p
, subtree
))
2663 if (mnt_ns_loop(p
->mnt
.mnt_root
))
2668 unlock_mount_hash();
2672 static int do_move_mount(struct path
*old_path
, struct path
*new_path
)
2674 struct mnt_namespace
*ns
;
2677 struct mount
*parent
;
2678 struct mountpoint
*mp
, *old_mp
;
2682 mp
= lock_mount(new_path
);
2686 old
= real_mount(old_path
->mnt
);
2687 p
= real_mount(new_path
->mnt
);
2688 parent
= old
->mnt_parent
;
2689 attached
= mnt_has_parent(old
);
2690 old_mp
= old
->mnt_mp
;
2694 /* The mountpoint must be in our namespace. */
2698 /* The thing moved must be mounted... */
2699 if (!is_mounted(&old
->mnt
))
2702 /* ... and either ours or the root of anon namespace */
2703 if (!(attached
? check_mnt(old
) : is_anon_ns(ns
)))
2706 if (old
->mnt
.mnt_flags
& MNT_LOCKED
)
2709 if (old_path
->dentry
!= old_path
->mnt
->mnt_root
)
2712 if (d_is_dir(new_path
->dentry
) !=
2713 d_is_dir(old_path
->dentry
))
2716 * Don't move a mount residing in a shared parent.
2718 if (attached
&& IS_MNT_SHARED(parent
))
2721 * Don't move a mount tree containing unbindable mounts to a destination
2722 * mount which is shared.
2724 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
2727 if (!check_for_nsfs_mounts(old
))
2729 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
2733 err
= attach_recursive_mnt(old
, real_mount(new_path
->mnt
), mp
,
2738 /* if the mount is moved, it should no longer be expire
2740 list_del_init(&old
->mnt_expire
);
2742 put_mountpoint(old_mp
);
2747 mntput_no_expire(parent
);
2754 static int do_move_mount_old(struct path
*path
, const char *old_name
)
2756 struct path old_path
;
2759 if (!old_name
|| !*old_name
)
2762 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
2766 err
= do_move_mount(&old_path
, path
);
2767 path_put(&old_path
);
2772 * add a mount into a namespace's mount tree
2774 static int do_add_mount(struct mount
*newmnt
, struct mountpoint
*mp
,
2775 struct path
*path
, int mnt_flags
)
2777 struct mount
*parent
= real_mount(path
->mnt
);
2779 mnt_flags
&= ~MNT_INTERNAL_FLAGS
;
2781 if (unlikely(!check_mnt(parent
))) {
2782 /* that's acceptable only for automounts done in private ns */
2783 if (!(mnt_flags
& MNT_SHRINKABLE
))
2785 /* ... and for those we'd better have mountpoint still alive */
2786 if (!parent
->mnt_ns
)
2790 /* Refuse the same filesystem on the same mount point */
2791 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
2792 path
->mnt
->mnt_root
== path
->dentry
)
2795 if (d_is_symlink(newmnt
->mnt
.mnt_root
))
2798 newmnt
->mnt
.mnt_flags
= mnt_flags
;
2799 return graft_tree(newmnt
, parent
, mp
);
2802 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
);
2805 * Create a new mount using a superblock configuration and request it
2806 * be added to the namespace tree.
2808 static int do_new_mount_fc(struct fs_context
*fc
, struct path
*mountpoint
,
2809 unsigned int mnt_flags
)
2811 struct vfsmount
*mnt
;
2812 struct mountpoint
*mp
;
2813 struct super_block
*sb
= fc
->root
->d_sb
;
2816 error
= security_sb_kern_mount(sb
);
2817 if (!error
&& mount_too_revealing(sb
, &mnt_flags
))
2820 if (unlikely(error
)) {
2825 up_write(&sb
->s_umount
);
2827 mnt
= vfs_create_mount(fc
);
2829 return PTR_ERR(mnt
);
2831 mnt_warn_timestamp_expiry(mountpoint
, mnt
);
2833 mp
= lock_mount(mountpoint
);
2838 error
= do_add_mount(real_mount(mnt
), mp
, mountpoint
, mnt_flags
);
2846 * create a new mount for userspace and request it to be added into the
2849 static int do_new_mount(struct path
*path
, const char *fstype
, int sb_flags
,
2850 int mnt_flags
, const char *name
, void *data
)
2852 struct file_system_type
*type
;
2853 struct fs_context
*fc
;
2854 const char *subtype
= NULL
;
2860 type
= get_fs_type(fstype
);
2864 if (type
->fs_flags
& FS_HAS_SUBTYPE
) {
2865 subtype
= strchr(fstype
, '.');
2869 put_filesystem(type
);
2875 fc
= fs_context_for_mount(type
, sb_flags
);
2876 put_filesystem(type
);
2881 err
= vfs_parse_fs_string(fc
, "subtype",
2882 subtype
, strlen(subtype
));
2884 err
= vfs_parse_fs_string(fc
, "source", name
, strlen(name
));
2886 err
= parse_monolithic_mount_data(fc
, data
);
2887 if (!err
&& !mount_capable(fc
))
2890 err
= vfs_get_tree(fc
);
2892 err
= do_new_mount_fc(fc
, path
, mnt_flags
);
2898 int finish_automount(struct vfsmount
*m
, struct path
*path
)
2900 struct dentry
*dentry
= path
->dentry
;
2901 struct mountpoint
*mp
;
2910 mnt
= real_mount(m
);
2911 /* The new mount record should have at least 2 refs to prevent it being
2912 * expired before we get a chance to add it
2914 BUG_ON(mnt_get_count(mnt
) < 2);
2916 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
2917 m
->mnt_root
== dentry
) {
2923 * we don't want to use lock_mount() - in this case finding something
2924 * that overmounts our mountpoint to be means "quitely drop what we've
2925 * got", not "try to mount it on top".
2927 inode_lock(dentry
->d_inode
);
2929 if (unlikely(cant_mount(dentry
))) {
2931 goto discard_locked
;
2934 if (unlikely(__lookup_mnt(path
->mnt
, dentry
))) {
2937 goto discard_locked
;
2940 mp
= get_mountpoint(dentry
);
2943 goto discard_locked
;
2946 err
= do_add_mount(mnt
, mp
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
2955 inode_unlock(dentry
->d_inode
);
2957 /* remove m from any expiration list it may be on */
2958 if (!list_empty(&mnt
->mnt_expire
)) {
2960 list_del_init(&mnt
->mnt_expire
);
2969 * mnt_set_expiry - Put a mount on an expiration list
2970 * @mnt: The mount to list.
2971 * @expiry_list: The list to add the mount to.
2973 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
2977 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
2981 EXPORT_SYMBOL(mnt_set_expiry
);
2984 * process a list of expirable mountpoints with the intent of discarding any
2985 * mountpoints that aren't in use and haven't been touched since last we came
2988 void mark_mounts_for_expiry(struct list_head
*mounts
)
2990 struct mount
*mnt
, *next
;
2991 LIST_HEAD(graveyard
);
2993 if (list_empty(mounts
))
2999 /* extract from the expiration list every vfsmount that matches the
3000 * following criteria:
3001 * - only referenced by its parent vfsmount
3002 * - still marked for expiry (marked on the last call here; marks are
3003 * cleared by mntput())
3005 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
3006 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
3007 propagate_mount_busy(mnt
, 1))
3009 list_move(&mnt
->mnt_expire
, &graveyard
);
3011 while (!list_empty(&graveyard
)) {
3012 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
3013 touch_mnt_namespace(mnt
->mnt_ns
);
3014 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
3016 unlock_mount_hash();
3020 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
3023 * Ripoff of 'select_parent()'
3025 * search the list of submounts for a given mountpoint, and move any
3026 * shrinkable submounts to the 'graveyard' list.
3028 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
3030 struct mount
*this_parent
= parent
;
3031 struct list_head
*next
;
3035 next
= this_parent
->mnt_mounts
.next
;
3037 while (next
!= &this_parent
->mnt_mounts
) {
3038 struct list_head
*tmp
= next
;
3039 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
3042 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
3045 * Descend a level if the d_mounts list is non-empty.
3047 if (!list_empty(&mnt
->mnt_mounts
)) {
3052 if (!propagate_mount_busy(mnt
, 1)) {
3053 list_move_tail(&mnt
->mnt_expire
, graveyard
);
3058 * All done at this level ... ascend and resume the search
3060 if (this_parent
!= parent
) {
3061 next
= this_parent
->mnt_child
.next
;
3062 this_parent
= this_parent
->mnt_parent
;
3069 * process a list of expirable mountpoints with the intent of discarding any
3070 * submounts of a specific parent mountpoint
3072 * mount_lock must be held for write
3074 static void shrink_submounts(struct mount
*mnt
)
3076 LIST_HEAD(graveyard
);
3079 /* extract submounts of 'mountpoint' from the expiration list */
3080 while (select_submounts(mnt
, &graveyard
)) {
3081 while (!list_empty(&graveyard
)) {
3082 m
= list_first_entry(&graveyard
, struct mount
,
3084 touch_mnt_namespace(m
->mnt_ns
);
3085 umount_tree(m
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
3090 static void *copy_mount_options(const void __user
* data
)
3093 unsigned left
, offset
;
3098 copy
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
3100 return ERR_PTR(-ENOMEM
);
3102 left
= copy_from_user(copy
, data
, PAGE_SIZE
);
3105 * Not all architectures have an exact copy_from_user(). Resort to
3108 offset
= PAGE_SIZE
- left
;
3111 if (get_user(c
, (const char __user
*)data
+ offset
))
3118 if (left
== PAGE_SIZE
) {
3120 return ERR_PTR(-EFAULT
);
3126 static char *copy_mount_string(const void __user
*data
)
3128 return data
? strndup_user(data
, PATH_MAX
) : NULL
;
3132 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3133 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3135 * data is a (void *) that can point to any structure up to
3136 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3137 * information (or be NULL).
3139 * Pre-0.97 versions of mount() didn't have a flags word.
3140 * When the flags word was introduced its top half was required
3141 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3142 * Therefore, if this magic number is present, it carries no information
3143 * and must be discarded.
3145 int path_mount(const char *dev_name
, struct path
*path
,
3146 const char *type_page
, unsigned long flags
, void *data_page
)
3148 unsigned int mnt_flags
= 0, sb_flags
;
3152 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
3153 flags
&= ~MS_MGC_MSK
;
3155 /* Basic sanity checks */
3157 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
3159 if (flags
& MS_NOUSER
)
3162 ret
= security_sb_mount(dev_name
, path
, type_page
, flags
, data_page
);
3167 if ((flags
& SB_MANDLOCK
) && !may_mandlock())
3170 /* Default to relatime unless overriden */
3171 if (!(flags
& MS_NOATIME
))
3172 mnt_flags
|= MNT_RELATIME
;
3174 /* Separate the per-mountpoint flags */
3175 if (flags
& MS_NOSUID
)
3176 mnt_flags
|= MNT_NOSUID
;
3177 if (flags
& MS_NODEV
)
3178 mnt_flags
|= MNT_NODEV
;
3179 if (flags
& MS_NOEXEC
)
3180 mnt_flags
|= MNT_NOEXEC
;
3181 if (flags
& MS_NOATIME
)
3182 mnt_flags
|= MNT_NOATIME
;
3183 if (flags
& MS_NODIRATIME
)
3184 mnt_flags
|= MNT_NODIRATIME
;
3185 if (flags
& MS_STRICTATIME
)
3186 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
3187 if (flags
& MS_RDONLY
)
3188 mnt_flags
|= MNT_READONLY
;
3189 if (flags
& MS_NOSYMFOLLOW
)
3190 mnt_flags
|= MNT_NOSYMFOLLOW
;
3192 /* The default atime for remount is preservation */
3193 if ((flags
& MS_REMOUNT
) &&
3194 ((flags
& (MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
|
3195 MS_STRICTATIME
)) == 0)) {
3196 mnt_flags
&= ~MNT_ATIME_MASK
;
3197 mnt_flags
|= path
->mnt
->mnt_flags
& MNT_ATIME_MASK
;
3200 sb_flags
= flags
& (SB_RDONLY
|
3209 if ((flags
& (MS_REMOUNT
| MS_BIND
)) == (MS_REMOUNT
| MS_BIND
))
3210 return do_reconfigure_mnt(path
, mnt_flags
);
3211 if (flags
& MS_REMOUNT
)
3212 return do_remount(path
, flags
, sb_flags
, mnt_flags
, data_page
);
3213 if (flags
& MS_BIND
)
3214 return do_loopback(path
, dev_name
, flags
& MS_REC
);
3215 if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
3216 return do_change_type(path
, flags
);
3217 if (flags
& MS_MOVE
)
3218 return do_move_mount_old(path
, dev_name
);
3220 return do_new_mount(path
, type_page
, sb_flags
, mnt_flags
, dev_name
,
3224 long do_mount(const char *dev_name
, const char __user
*dir_name
,
3225 const char *type_page
, unsigned long flags
, void *data_page
)
3230 ret
= user_path_at(AT_FDCWD
, dir_name
, LOOKUP_FOLLOW
, &path
);
3233 ret
= path_mount(dev_name
, &path
, type_page
, flags
, data_page
);
3238 static struct ucounts
*inc_mnt_namespaces(struct user_namespace
*ns
)
3240 return inc_ucount(ns
, current_euid(), UCOUNT_MNT_NAMESPACES
);
3243 static void dec_mnt_namespaces(struct ucounts
*ucounts
)
3245 dec_ucount(ucounts
, UCOUNT_MNT_NAMESPACES
);
3248 static void free_mnt_ns(struct mnt_namespace
*ns
)
3250 if (!is_anon_ns(ns
))
3251 ns_free_inum(&ns
->ns
);
3252 dec_mnt_namespaces(ns
->ucounts
);
3253 put_user_ns(ns
->user_ns
);
3258 * Assign a sequence number so we can detect when we attempt to bind
3259 * mount a reference to an older mount namespace into the current
3260 * mount namespace, preventing reference counting loops. A 64bit
3261 * number incrementing at 10Ghz will take 12,427 years to wrap which
3262 * is effectively never, so we can ignore the possibility.
3264 static atomic64_t mnt_ns_seq
= ATOMIC64_INIT(1);
3266 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*user_ns
, bool anon
)
3268 struct mnt_namespace
*new_ns
;
3269 struct ucounts
*ucounts
;
3272 ucounts
= inc_mnt_namespaces(user_ns
);
3274 return ERR_PTR(-ENOSPC
);
3276 new_ns
= kzalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
3278 dec_mnt_namespaces(ucounts
);
3279 return ERR_PTR(-ENOMEM
);
3282 ret
= ns_alloc_inum(&new_ns
->ns
);
3285 dec_mnt_namespaces(ucounts
);
3286 return ERR_PTR(ret
);
3289 new_ns
->ns
.ops
= &mntns_operations
;
3291 new_ns
->seq
= atomic64_add_return(1, &mnt_ns_seq
);
3292 refcount_set(&new_ns
->ns
.count
, 1);
3293 INIT_LIST_HEAD(&new_ns
->list
);
3294 init_waitqueue_head(&new_ns
->poll
);
3295 spin_lock_init(&new_ns
->ns_lock
);
3296 new_ns
->user_ns
= get_user_ns(user_ns
);
3297 new_ns
->ucounts
= ucounts
;
3302 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
3303 struct user_namespace
*user_ns
, struct fs_struct
*new_fs
)
3305 struct mnt_namespace
*new_ns
;
3306 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
3307 struct mount
*p
, *q
;
3314 if (likely(!(flags
& CLONE_NEWNS
))) {
3321 new_ns
= alloc_mnt_ns(user_ns
, false);
3326 /* First pass: copy the tree topology */
3327 copy_flags
= CL_COPY_UNBINDABLE
| CL_EXPIRE
;
3328 if (user_ns
!= ns
->user_ns
)
3329 copy_flags
|= CL_SHARED_TO_SLAVE
;
3330 new = copy_tree(old
, old
->mnt
.mnt_root
, copy_flags
);
3333 free_mnt_ns(new_ns
);
3334 return ERR_CAST(new);
3336 if (user_ns
!= ns
->user_ns
) {
3339 unlock_mount_hash();
3342 list_add_tail(&new_ns
->list
, &new->mnt_list
);
3345 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3346 * as belonging to new namespace. We have already acquired a private
3347 * fs_struct, so tsk->fs->lock is not needed.
3355 if (&p
->mnt
== new_fs
->root
.mnt
) {
3356 new_fs
->root
.mnt
= mntget(&q
->mnt
);
3359 if (&p
->mnt
== new_fs
->pwd
.mnt
) {
3360 new_fs
->pwd
.mnt
= mntget(&q
->mnt
);
3364 p
= next_mnt(p
, old
);
3365 q
= next_mnt(q
, new);
3368 while (p
->mnt
.mnt_root
!= q
->mnt
.mnt_root
)
3369 p
= next_mnt(p
, old
);
3381 struct dentry
*mount_subtree(struct vfsmount
*m
, const char *name
)
3383 struct mount
*mnt
= real_mount(m
);
3384 struct mnt_namespace
*ns
;
3385 struct super_block
*s
;
3389 ns
= alloc_mnt_ns(&init_user_ns
, true);
3392 return ERR_CAST(ns
);
3397 list_add(&mnt
->mnt_list
, &ns
->list
);
3399 err
= vfs_path_lookup(m
->mnt_root
, m
,
3400 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
3405 return ERR_PTR(err
);
3407 /* trade a vfsmount reference for active sb one */
3408 s
= path
.mnt
->mnt_sb
;
3409 atomic_inc(&s
->s_active
);
3411 /* lock the sucker */
3412 down_write(&s
->s_umount
);
3413 /* ... and return the root of (sub)tree on it */
3416 EXPORT_SYMBOL(mount_subtree
);
3418 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
3419 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
3426 kernel_type
= copy_mount_string(type
);
3427 ret
= PTR_ERR(kernel_type
);
3428 if (IS_ERR(kernel_type
))
3431 kernel_dev
= copy_mount_string(dev_name
);
3432 ret
= PTR_ERR(kernel_dev
);
3433 if (IS_ERR(kernel_dev
))
3436 options
= copy_mount_options(data
);
3437 ret
= PTR_ERR(options
);
3438 if (IS_ERR(options
))
3441 ret
= do_mount(kernel_dev
, dir_name
, kernel_type
, flags
, options
);
3453 * Create a kernel mount representation for a new, prepared superblock
3454 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3456 SYSCALL_DEFINE3(fsmount
, int, fs_fd
, unsigned int, flags
,
3457 unsigned int, attr_flags
)
3459 struct mnt_namespace
*ns
;
3460 struct fs_context
*fc
;
3462 struct path newmount
;
3465 unsigned int mnt_flags
= 0;
3471 if ((flags
& ~(FSMOUNT_CLOEXEC
)) != 0)
3474 if (attr_flags
& ~(MOUNT_ATTR_RDONLY
|
3479 MOUNT_ATTR_NODIRATIME
))
3482 if (attr_flags
& MOUNT_ATTR_RDONLY
)
3483 mnt_flags
|= MNT_READONLY
;
3484 if (attr_flags
& MOUNT_ATTR_NOSUID
)
3485 mnt_flags
|= MNT_NOSUID
;
3486 if (attr_flags
& MOUNT_ATTR_NODEV
)
3487 mnt_flags
|= MNT_NODEV
;
3488 if (attr_flags
& MOUNT_ATTR_NOEXEC
)
3489 mnt_flags
|= MNT_NOEXEC
;
3490 if (attr_flags
& MOUNT_ATTR_NODIRATIME
)
3491 mnt_flags
|= MNT_NODIRATIME
;
3493 switch (attr_flags
& MOUNT_ATTR__ATIME
) {
3494 case MOUNT_ATTR_STRICTATIME
:
3496 case MOUNT_ATTR_NOATIME
:
3497 mnt_flags
|= MNT_NOATIME
;
3499 case MOUNT_ATTR_RELATIME
:
3500 mnt_flags
|= MNT_RELATIME
;
3511 if (f
.file
->f_op
!= &fscontext_fops
)
3514 fc
= f
.file
->private_data
;
3516 ret
= mutex_lock_interruptible(&fc
->uapi_mutex
);
3520 /* There must be a valid superblock or we can't mount it */
3526 if (mount_too_revealing(fc
->root
->d_sb
, &mnt_flags
)) {
3527 pr_warn("VFS: Mount too revealing\n");
3532 if (fc
->phase
!= FS_CONTEXT_AWAITING_MOUNT
)
3536 if ((fc
->sb_flags
& SB_MANDLOCK
) && !may_mandlock())
3539 newmount
.mnt
= vfs_create_mount(fc
);
3540 if (IS_ERR(newmount
.mnt
)) {
3541 ret
= PTR_ERR(newmount
.mnt
);
3544 newmount
.dentry
= dget(fc
->root
);
3545 newmount
.mnt
->mnt_flags
= mnt_flags
;
3547 /* We've done the mount bit - now move the file context into more or
3548 * less the same state as if we'd done an fspick(). We don't want to
3549 * do any memory allocation or anything like that at this point as we
3550 * don't want to have to handle any errors incurred.
3552 vfs_clean_context(fc
);
3554 ns
= alloc_mnt_ns(current
->nsproxy
->mnt_ns
->user_ns
, true);
3559 mnt
= real_mount(newmount
.mnt
);
3563 list_add(&mnt
->mnt_list
, &ns
->list
);
3564 mntget(newmount
.mnt
);
3566 /* Attach to an apparent O_PATH fd with a note that we need to unmount
3567 * it, not just simply put it.
3569 file
= dentry_open(&newmount
, O_PATH
, fc
->cred
);
3571 dissolve_on_fput(newmount
.mnt
);
3572 ret
= PTR_ERR(file
);
3575 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
3577 ret
= get_unused_fd_flags((flags
& FSMOUNT_CLOEXEC
) ? O_CLOEXEC
: 0);
3579 fd_install(ret
, file
);
3584 path_put(&newmount
);
3586 mutex_unlock(&fc
->uapi_mutex
);
3593 * Move a mount from one place to another. In combination with
3594 * fsopen()/fsmount() this is used to install a new mount and in combination
3595 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
3598 * Note the flags value is a combination of MOVE_MOUNT_* flags.
3600 SYSCALL_DEFINE5(move_mount
,
3601 int, from_dfd
, const char __user
*, from_pathname
,
3602 int, to_dfd
, const char __user
*, to_pathname
,
3603 unsigned int, flags
)
3605 struct path from_path
, to_path
;
3606 unsigned int lflags
;
3612 if (flags
& ~MOVE_MOUNT__MASK
)
3615 /* If someone gives a pathname, they aren't permitted to move
3616 * from an fd that requires unmount as we can't get at the flag
3617 * to clear it afterwards.
3620 if (flags
& MOVE_MOUNT_F_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
3621 if (flags
& MOVE_MOUNT_F_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
3622 if (flags
& MOVE_MOUNT_F_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
3624 ret
= user_path_at(from_dfd
, from_pathname
, lflags
, &from_path
);
3629 if (flags
& MOVE_MOUNT_T_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
3630 if (flags
& MOVE_MOUNT_T_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
3631 if (flags
& MOVE_MOUNT_T_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
3633 ret
= user_path_at(to_dfd
, to_pathname
, lflags
, &to_path
);
3637 ret
= security_move_mount(&from_path
, &to_path
);
3641 ret
= do_move_mount(&from_path
, &to_path
);
3646 path_put(&from_path
);
3651 * Return true if path is reachable from root
3653 * namespace_sem or mount_lock is held
3655 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
3656 const struct path
*root
)
3658 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
3659 dentry
= mnt
->mnt_mountpoint
;
3660 mnt
= mnt
->mnt_parent
;
3662 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
3665 bool path_is_under(const struct path
*path1
, const struct path
*path2
)
3668 read_seqlock_excl(&mount_lock
);
3669 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
3670 read_sequnlock_excl(&mount_lock
);
3673 EXPORT_SYMBOL(path_is_under
);
3676 * pivot_root Semantics:
3677 * Moves the root file system of the current process to the directory put_old,
3678 * makes new_root as the new root file system of the current process, and sets
3679 * root/cwd of all processes which had them on the current root to new_root.
3682 * The new_root and put_old must be directories, and must not be on the
3683 * same file system as the current process root. The put_old must be
3684 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3685 * pointed to by put_old must yield the same directory as new_root. No other
3686 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3688 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3689 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
3690 * in this situation.
3693 * - we don't move root/cwd if they are not at the root (reason: if something
3694 * cared enough to change them, it's probably wrong to force them elsewhere)
3695 * - it's okay to pick a root that isn't the root of a file system, e.g.
3696 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3697 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3700 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
3701 const char __user
*, put_old
)
3703 struct path
new, old
, root
;
3704 struct mount
*new_mnt
, *root_mnt
, *old_mnt
, *root_parent
, *ex_parent
;
3705 struct mountpoint
*old_mp
, *root_mp
;
3711 error
= user_path_at(AT_FDCWD
, new_root
,
3712 LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
, &new);
3716 error
= user_path_at(AT_FDCWD
, put_old
,
3717 LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
, &old
);
3721 error
= security_sb_pivotroot(&old
, &new);
3725 get_fs_root(current
->fs
, &root
);
3726 old_mp
= lock_mount(&old
);
3727 error
= PTR_ERR(old_mp
);
3732 new_mnt
= real_mount(new.mnt
);
3733 root_mnt
= real_mount(root
.mnt
);
3734 old_mnt
= real_mount(old
.mnt
);
3735 ex_parent
= new_mnt
->mnt_parent
;
3736 root_parent
= root_mnt
->mnt_parent
;
3737 if (IS_MNT_SHARED(old_mnt
) ||
3738 IS_MNT_SHARED(ex_parent
) ||
3739 IS_MNT_SHARED(root_parent
))
3741 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
3743 if (new_mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
3746 if (d_unlinked(new.dentry
))
3749 if (new_mnt
== root_mnt
|| old_mnt
== root_mnt
)
3750 goto out4
; /* loop, on the same file system */
3752 if (root
.mnt
->mnt_root
!= root
.dentry
)
3753 goto out4
; /* not a mountpoint */
3754 if (!mnt_has_parent(root_mnt
))
3755 goto out4
; /* not attached */
3756 if (new.mnt
->mnt_root
!= new.dentry
)
3757 goto out4
; /* not a mountpoint */
3758 if (!mnt_has_parent(new_mnt
))
3759 goto out4
; /* not attached */
3760 /* make sure we can reach put_old from new_root */
3761 if (!is_path_reachable(old_mnt
, old
.dentry
, &new))
3763 /* make certain new is below the root */
3764 if (!is_path_reachable(new_mnt
, new.dentry
, &root
))
3767 umount_mnt(new_mnt
);
3768 root_mp
= unhash_mnt(root_mnt
); /* we'll need its mountpoint */
3769 if (root_mnt
->mnt
.mnt_flags
& MNT_LOCKED
) {
3770 new_mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
3771 root_mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
3773 /* mount old root on put_old */
3774 attach_mnt(root_mnt
, old_mnt
, old_mp
);
3775 /* mount new_root on / */
3776 attach_mnt(new_mnt
, root_parent
, root_mp
);
3777 mnt_add_count(root_parent
, -1);
3778 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
3779 /* A moved mount should not expire automatically */
3780 list_del_init(&new_mnt
->mnt_expire
);
3781 put_mountpoint(root_mp
);
3782 unlock_mount_hash();
3783 chroot_fs_refs(&root
, &new);
3786 unlock_mount(old_mp
);
3788 mntput_no_expire(ex_parent
);
3799 static void __init
init_mount_tree(void)
3801 struct vfsmount
*mnt
;
3803 struct mnt_namespace
*ns
;
3806 mnt
= vfs_kern_mount(&rootfs_fs_type
, 0, "rootfs", NULL
);
3808 panic("Can't create rootfs");
3810 ns
= alloc_mnt_ns(&init_user_ns
, false);
3812 panic("Can't allocate initial namespace");
3813 m
= real_mount(mnt
);
3817 list_add(&m
->mnt_list
, &ns
->list
);
3818 init_task
.nsproxy
->mnt_ns
= ns
;
3822 root
.dentry
= mnt
->mnt_root
;
3823 mnt
->mnt_flags
|= MNT_LOCKED
;
3825 set_fs_pwd(current
->fs
, &root
);
3826 set_fs_root(current
->fs
, &root
);
3829 void __init
mnt_init(void)
3833 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
3834 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
3836 mount_hashtable
= alloc_large_system_hash("Mount-cache",
3837 sizeof(struct hlist_head
),
3840 &m_hash_shift
, &m_hash_mask
, 0, 0);
3841 mountpoint_hashtable
= alloc_large_system_hash("Mountpoint-cache",
3842 sizeof(struct hlist_head
),
3845 &mp_hash_shift
, &mp_hash_mask
, 0, 0);
3847 if (!mount_hashtable
|| !mountpoint_hashtable
)
3848 panic("Failed to allocate mount hash table\n");
3854 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
3856 fs_kobj
= kobject_create_and_add("fs", NULL
);
3858 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
3864 void put_mnt_ns(struct mnt_namespace
*ns
)
3866 if (!refcount_dec_and_test(&ns
->ns
.count
))
3868 drop_collected_mounts(&ns
->root
->mnt
);
3872 struct vfsmount
*kern_mount(struct file_system_type
*type
)
3874 struct vfsmount
*mnt
;
3875 mnt
= vfs_kern_mount(type
, SB_KERNMOUNT
, type
->name
, NULL
);
3878 * it is a longterm mount, don't release mnt until
3879 * we unmount before file sys is unregistered
3881 real_mount(mnt
)->mnt_ns
= MNT_NS_INTERNAL
;
3885 EXPORT_SYMBOL_GPL(kern_mount
);
3887 void kern_unmount(struct vfsmount
*mnt
)
3889 /* release long term mount so mount point can be released */
3890 if (!IS_ERR_OR_NULL(mnt
)) {
3891 real_mount(mnt
)->mnt_ns
= NULL
;
3892 synchronize_rcu(); /* yecchhh... */
3896 EXPORT_SYMBOL(kern_unmount
);
3898 void kern_unmount_array(struct vfsmount
*mnt
[], unsigned int num
)
3902 for (i
= 0; i
< num
; i
++)
3904 real_mount(mnt
[i
])->mnt_ns
= NULL
;
3905 synchronize_rcu_expedited();
3906 for (i
= 0; i
< num
; i
++)
3909 EXPORT_SYMBOL(kern_unmount_array
);
3911 bool our_mnt(struct vfsmount
*mnt
)
3913 return check_mnt(real_mount(mnt
));
3916 bool current_chrooted(void)
3918 /* Does the current process have a non-standard root */
3919 struct path ns_root
;
3920 struct path fs_root
;
3923 /* Find the namespace root */
3924 ns_root
.mnt
= ¤t
->nsproxy
->mnt_ns
->root
->mnt
;
3925 ns_root
.dentry
= ns_root
.mnt
->mnt_root
;
3927 while (d_mountpoint(ns_root
.dentry
) && follow_down_one(&ns_root
))
3930 get_fs_root(current
->fs
, &fs_root
);
3932 chrooted
= !path_equal(&fs_root
, &ns_root
);
3940 static bool mnt_already_visible(struct mnt_namespace
*ns
,
3941 const struct super_block
*sb
,
3944 int new_flags
= *new_mnt_flags
;
3946 bool visible
= false;
3948 down_read(&namespace_sem
);
3950 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
3951 struct mount
*child
;
3954 if (mnt_is_cursor(mnt
))
3957 if (mnt
->mnt
.mnt_sb
->s_type
!= sb
->s_type
)
3960 /* This mount is not fully visible if it's root directory
3961 * is not the root directory of the filesystem.
3963 if (mnt
->mnt
.mnt_root
!= mnt
->mnt
.mnt_sb
->s_root
)
3966 /* A local view of the mount flags */
3967 mnt_flags
= mnt
->mnt
.mnt_flags
;
3969 /* Don't miss readonly hidden in the superblock flags */
3970 if (sb_rdonly(mnt
->mnt
.mnt_sb
))
3971 mnt_flags
|= MNT_LOCK_READONLY
;
3973 /* Verify the mount flags are equal to or more permissive
3974 * than the proposed new mount.
3976 if ((mnt_flags
& MNT_LOCK_READONLY
) &&
3977 !(new_flags
& MNT_READONLY
))
3979 if ((mnt_flags
& MNT_LOCK_ATIME
) &&
3980 ((mnt_flags
& MNT_ATIME_MASK
) != (new_flags
& MNT_ATIME_MASK
)))
3983 /* This mount is not fully visible if there are any
3984 * locked child mounts that cover anything except for
3985 * empty directories.
3987 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
3988 struct inode
*inode
= child
->mnt_mountpoint
->d_inode
;
3989 /* Only worry about locked mounts */
3990 if (!(child
->mnt
.mnt_flags
& MNT_LOCKED
))
3992 /* Is the directory permanetly empty? */
3993 if (!is_empty_dir_inode(inode
))
3996 /* Preserve the locked attributes */
3997 *new_mnt_flags
|= mnt_flags
& (MNT_LOCK_READONLY
| \
4005 up_read(&namespace_sem
);
4009 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
)
4011 const unsigned long required_iflags
= SB_I_NOEXEC
| SB_I_NODEV
;
4012 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
4013 unsigned long s_iflags
;
4015 if (ns
->user_ns
== &init_user_ns
)
4018 /* Can this filesystem be too revealing? */
4019 s_iflags
= sb
->s_iflags
;
4020 if (!(s_iflags
& SB_I_USERNS_VISIBLE
))
4023 if ((s_iflags
& required_iflags
) != required_iflags
) {
4024 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
4029 return !mnt_already_visible(ns
, sb
, new_mnt_flags
);
4032 bool mnt_may_suid(struct vfsmount
*mnt
)
4035 * Foreign mounts (accessed via fchdir or through /proc
4036 * symlinks) are always treated as if they are nosuid. This
4037 * prevents namespaces from trusting potentially unsafe
4038 * suid/sgid bits, file caps, or security labels that originate
4039 * in other namespaces.
4041 return !(mnt
->mnt_flags
& MNT_NOSUID
) && check_mnt(real_mount(mnt
)) &&
4042 current_in_userns(mnt
->mnt_sb
->s_user_ns
);
4045 static struct ns_common
*mntns_get(struct task_struct
*task
)
4047 struct ns_common
*ns
= NULL
;
4048 struct nsproxy
*nsproxy
;
4051 nsproxy
= task
->nsproxy
;
4053 ns
= &nsproxy
->mnt_ns
->ns
;
4054 get_mnt_ns(to_mnt_ns(ns
));
4061 static void mntns_put(struct ns_common
*ns
)
4063 put_mnt_ns(to_mnt_ns(ns
));
4066 static int mntns_install(struct nsset
*nsset
, struct ns_common
*ns
)
4068 struct nsproxy
*nsproxy
= nsset
->nsproxy
;
4069 struct fs_struct
*fs
= nsset
->fs
;
4070 struct mnt_namespace
*mnt_ns
= to_mnt_ns(ns
), *old_mnt_ns
;
4071 struct user_namespace
*user_ns
= nsset
->cred
->user_ns
;
4075 if (!ns_capable(mnt_ns
->user_ns
, CAP_SYS_ADMIN
) ||
4076 !ns_capable(user_ns
, CAP_SYS_CHROOT
) ||
4077 !ns_capable(user_ns
, CAP_SYS_ADMIN
))
4080 if (is_anon_ns(mnt_ns
))
4087 old_mnt_ns
= nsproxy
->mnt_ns
;
4088 nsproxy
->mnt_ns
= mnt_ns
;
4091 err
= vfs_path_lookup(mnt_ns
->root
->mnt
.mnt_root
, &mnt_ns
->root
->mnt
,
4092 "/", LOOKUP_DOWN
, &root
);
4094 /* revert to old namespace */
4095 nsproxy
->mnt_ns
= old_mnt_ns
;
4100 put_mnt_ns(old_mnt_ns
);
4102 /* Update the pwd and root */
4103 set_fs_pwd(fs
, &root
);
4104 set_fs_root(fs
, &root
);
4110 static struct user_namespace
*mntns_owner(struct ns_common
*ns
)
4112 return to_mnt_ns(ns
)->user_ns
;
4115 const struct proc_ns_operations mntns_operations
= {
4117 .type
= CLONE_NEWNS
,
4120 .install
= mntns_install
,
4121 .owner
= mntns_owner
,