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 unsigned int mnt_get_count(struct mount
*mnt
)
162 unsigned int count
= 0;
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
));
436 * mnt_drop_write - give up write access to a mount
437 * @mnt: the mount on which to give up write access
439 * Tells the low-level filesystem that we are done performing writes to it and
440 * also allows filesystem to be frozen again. Must be matched with
441 * mnt_want_write() call above.
443 void mnt_drop_write(struct vfsmount
*mnt
)
445 __mnt_drop_write(mnt
);
446 sb_end_write(mnt
->mnt_sb
);
448 EXPORT_SYMBOL_GPL(mnt_drop_write
);
450 void __mnt_drop_write_file(struct file
*file
)
452 __mnt_drop_write(file
->f_path
.mnt
);
455 void mnt_drop_write_file(struct file
*file
)
457 __mnt_drop_write_file(file
);
458 sb_end_write(file_inode(file
)->i_sb
);
460 EXPORT_SYMBOL(mnt_drop_write_file
);
462 static int mnt_make_readonly(struct mount
*mnt
)
467 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
469 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
470 * should be visible before we do.
475 * With writers on hold, if this value is zero, then there are
476 * definitely no active writers (although held writers may subsequently
477 * increment the count, they'll have to wait, and decrement it after
478 * seeing MNT_READONLY).
480 * It is OK to have counter incremented on one CPU and decremented on
481 * another: the sum will add up correctly. The danger would be when we
482 * sum up each counter, if we read a counter before it is incremented,
483 * but then read another CPU's count which it has been subsequently
484 * decremented from -- we would see more decrements than we should.
485 * MNT_WRITE_HOLD protects against this scenario, because
486 * mnt_want_write first increments count, then smp_mb, then spins on
487 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
488 * we're counting up here.
490 if (mnt_get_writers(mnt
) > 0)
493 mnt
->mnt
.mnt_flags
|= MNT_READONLY
;
495 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
496 * that become unheld will see MNT_READONLY.
499 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
504 static int __mnt_unmake_readonly(struct mount
*mnt
)
507 mnt
->mnt
.mnt_flags
&= ~MNT_READONLY
;
512 int sb_prepare_remount_readonly(struct super_block
*sb
)
517 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
518 if (atomic_long_read(&sb
->s_remove_count
))
522 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
523 if (!(mnt
->mnt
.mnt_flags
& MNT_READONLY
)) {
524 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
526 if (mnt_get_writers(mnt
) > 0) {
532 if (!err
&& atomic_long_read(&sb
->s_remove_count
))
536 sb
->s_readonly_remount
= 1;
539 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
540 if (mnt
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
541 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
548 static void free_vfsmnt(struct mount
*mnt
)
550 kfree_const(mnt
->mnt_devname
);
552 free_percpu(mnt
->mnt_pcp
);
554 kmem_cache_free(mnt_cache
, mnt
);
557 static void delayed_free_vfsmnt(struct rcu_head
*head
)
559 free_vfsmnt(container_of(head
, struct mount
, mnt_rcu
));
562 /* call under rcu_read_lock */
563 int __legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
566 if (read_seqretry(&mount_lock
, seq
))
570 mnt
= real_mount(bastard
);
571 mnt_add_count(mnt
, 1);
572 smp_mb(); // see mntput_no_expire()
573 if (likely(!read_seqretry(&mount_lock
, seq
)))
575 if (bastard
->mnt_flags
& MNT_SYNC_UMOUNT
) {
576 mnt_add_count(mnt
, -1);
580 if (unlikely(bastard
->mnt_flags
& MNT_DOOMED
)) {
581 mnt_add_count(mnt
, -1);
586 /* caller will mntput() */
590 /* call under rcu_read_lock */
591 bool legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
593 int res
= __legitimize_mnt(bastard
, seq
);
596 if (unlikely(res
< 0)) {
605 * find the first mount at @dentry on vfsmount @mnt.
606 * call under rcu_read_lock()
608 struct mount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
610 struct hlist_head
*head
= m_hash(mnt
, dentry
);
613 hlist_for_each_entry_rcu(p
, head
, mnt_hash
)
614 if (&p
->mnt_parent
->mnt
== mnt
&& p
->mnt_mountpoint
== dentry
)
620 * lookup_mnt - Return the first child mount mounted at path
622 * "First" means first mounted chronologically. If you create the
625 * mount /dev/sda1 /mnt
626 * mount /dev/sda2 /mnt
627 * mount /dev/sda3 /mnt
629 * Then lookup_mnt() on the base /mnt dentry in the root mount will
630 * return successively the root dentry and vfsmount of /dev/sda1, then
631 * /dev/sda2, then /dev/sda3, then NULL.
633 * lookup_mnt takes a reference to the found vfsmount.
635 struct vfsmount
*lookup_mnt(const struct path
*path
)
637 struct mount
*child_mnt
;
643 seq
= read_seqbegin(&mount_lock
);
644 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
);
645 m
= child_mnt
? &child_mnt
->mnt
: NULL
;
646 } while (!legitimize_mnt(m
, seq
));
652 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
653 * current mount namespace.
655 * The common case is dentries are not mountpoints at all and that
656 * test is handled inline. For the slow case when we are actually
657 * dealing with a mountpoint of some kind, walk through all of the
658 * mounts in the current mount namespace and test to see if the dentry
661 * The mount_hashtable is not usable in the context because we
662 * need to identify all mounts that may be in the current mount
663 * namespace not just a mount that happens to have some specified
666 bool __is_local_mountpoint(struct dentry
*dentry
)
668 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
670 bool is_covered
= false;
672 if (!d_mountpoint(dentry
))
675 down_read(&namespace_sem
);
676 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
677 is_covered
= (mnt
->mnt_mountpoint
== dentry
);
681 up_read(&namespace_sem
);
686 static struct mountpoint
*lookup_mountpoint(struct dentry
*dentry
)
688 struct hlist_head
*chain
= mp_hash(dentry
);
689 struct mountpoint
*mp
;
691 hlist_for_each_entry(mp
, chain
, m_hash
) {
692 if (mp
->m_dentry
== dentry
) {
700 static struct mountpoint
*get_mountpoint(struct dentry
*dentry
)
702 struct mountpoint
*mp
, *new = NULL
;
705 if (d_mountpoint(dentry
)) {
706 /* might be worth a WARN_ON() */
707 if (d_unlinked(dentry
))
708 return ERR_PTR(-ENOENT
);
710 read_seqlock_excl(&mount_lock
);
711 mp
= lookup_mountpoint(dentry
);
712 read_sequnlock_excl(&mount_lock
);
718 new = kmalloc(sizeof(struct mountpoint
), GFP_KERNEL
);
720 return ERR_PTR(-ENOMEM
);
723 /* Exactly one processes may set d_mounted */
724 ret
= d_set_mounted(dentry
);
726 /* Someone else set d_mounted? */
730 /* The dentry is not available as a mountpoint? */
735 /* Add the new mountpoint to the hash table */
736 read_seqlock_excl(&mount_lock
);
737 new->m_dentry
= dget(dentry
);
739 hlist_add_head(&new->m_hash
, mp_hash(dentry
));
740 INIT_HLIST_HEAD(&new->m_list
);
741 read_sequnlock_excl(&mount_lock
);
751 * vfsmount lock must be held. Additionally, the caller is responsible
752 * for serializing calls for given disposal list.
754 static void __put_mountpoint(struct mountpoint
*mp
, struct list_head
*list
)
756 if (!--mp
->m_count
) {
757 struct dentry
*dentry
= mp
->m_dentry
;
758 BUG_ON(!hlist_empty(&mp
->m_list
));
759 spin_lock(&dentry
->d_lock
);
760 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
761 spin_unlock(&dentry
->d_lock
);
762 dput_to_list(dentry
, list
);
763 hlist_del(&mp
->m_hash
);
768 /* called with namespace_lock and vfsmount lock */
769 static void put_mountpoint(struct mountpoint
*mp
)
771 __put_mountpoint(mp
, &ex_mountpoints
);
774 static inline int check_mnt(struct mount
*mnt
)
776 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
780 * vfsmount lock must be held for write
782 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
786 wake_up_interruptible(&ns
->poll
);
791 * vfsmount lock must be held for write
793 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
795 if (ns
&& ns
->event
!= event
) {
797 wake_up_interruptible(&ns
->poll
);
802 * vfsmount lock must be held for write
804 static struct mountpoint
*unhash_mnt(struct mount
*mnt
)
806 struct mountpoint
*mp
;
807 mnt
->mnt_parent
= mnt
;
808 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
809 list_del_init(&mnt
->mnt_child
);
810 hlist_del_init_rcu(&mnt
->mnt_hash
);
811 hlist_del_init(&mnt
->mnt_mp_list
);
818 * vfsmount lock must be held for write
820 static void umount_mnt(struct mount
*mnt
)
822 put_mountpoint(unhash_mnt(mnt
));
826 * vfsmount lock must be held for write
828 void mnt_set_mountpoint(struct mount
*mnt
,
829 struct mountpoint
*mp
,
830 struct mount
*child_mnt
)
833 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
834 child_mnt
->mnt_mountpoint
= mp
->m_dentry
;
835 child_mnt
->mnt_parent
= mnt
;
836 child_mnt
->mnt_mp
= mp
;
837 hlist_add_head(&child_mnt
->mnt_mp_list
, &mp
->m_list
);
840 static void __attach_mnt(struct mount
*mnt
, struct mount
*parent
)
842 hlist_add_head_rcu(&mnt
->mnt_hash
,
843 m_hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
844 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
848 * vfsmount lock must be held for write
850 static void attach_mnt(struct mount
*mnt
,
851 struct mount
*parent
,
852 struct mountpoint
*mp
)
854 mnt_set_mountpoint(parent
, mp
, mnt
);
855 __attach_mnt(mnt
, parent
);
858 void mnt_change_mountpoint(struct mount
*parent
, struct mountpoint
*mp
, struct mount
*mnt
)
860 struct mountpoint
*old_mp
= mnt
->mnt_mp
;
861 struct mount
*old_parent
= mnt
->mnt_parent
;
863 list_del_init(&mnt
->mnt_child
);
864 hlist_del_init(&mnt
->mnt_mp_list
);
865 hlist_del_init_rcu(&mnt
->mnt_hash
);
867 attach_mnt(mnt
, parent
, mp
);
869 put_mountpoint(old_mp
);
870 mnt_add_count(old_parent
, -1);
874 * vfsmount lock must be held for write
876 static void commit_tree(struct mount
*mnt
)
878 struct mount
*parent
= mnt
->mnt_parent
;
881 struct mnt_namespace
*n
= parent
->mnt_ns
;
883 BUG_ON(parent
== mnt
);
885 list_add_tail(&head
, &mnt
->mnt_list
);
886 list_for_each_entry(m
, &head
, mnt_list
)
889 list_splice(&head
, n
->list
.prev
);
891 n
->mounts
+= n
->pending_mounts
;
892 n
->pending_mounts
= 0;
894 __attach_mnt(mnt
, parent
);
895 touch_mnt_namespace(n
);
898 static struct mount
*next_mnt(struct mount
*p
, struct mount
*root
)
900 struct list_head
*next
= p
->mnt_mounts
.next
;
901 if (next
== &p
->mnt_mounts
) {
905 next
= p
->mnt_child
.next
;
906 if (next
!= &p
->mnt_parent
->mnt_mounts
)
911 return list_entry(next
, struct mount
, mnt_child
);
914 static struct mount
*skip_mnt_tree(struct mount
*p
)
916 struct list_head
*prev
= p
->mnt_mounts
.prev
;
917 while (prev
!= &p
->mnt_mounts
) {
918 p
= list_entry(prev
, struct mount
, mnt_child
);
919 prev
= p
->mnt_mounts
.prev
;
925 * vfs_create_mount - Create a mount for a configured superblock
926 * @fc: The configuration context with the superblock attached
928 * Create a mount to an already configured superblock. If necessary, the
929 * caller should invoke vfs_get_tree() before calling this.
931 * Note that this does not attach the mount to anything.
933 struct vfsmount
*vfs_create_mount(struct fs_context
*fc
)
938 return ERR_PTR(-EINVAL
);
940 mnt
= alloc_vfsmnt(fc
->source
?: "none");
942 return ERR_PTR(-ENOMEM
);
944 if (fc
->sb_flags
& SB_KERNMOUNT
)
945 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
947 atomic_inc(&fc
->root
->d_sb
->s_active
);
948 mnt
->mnt
.mnt_sb
= fc
->root
->d_sb
;
949 mnt
->mnt
.mnt_root
= dget(fc
->root
);
950 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
951 mnt
->mnt_parent
= mnt
;
954 list_add_tail(&mnt
->mnt_instance
, &mnt
->mnt
.mnt_sb
->s_mounts
);
958 EXPORT_SYMBOL(vfs_create_mount
);
960 struct vfsmount
*fc_mount(struct fs_context
*fc
)
962 int err
= vfs_get_tree(fc
);
964 up_write(&fc
->root
->d_sb
->s_umount
);
965 return vfs_create_mount(fc
);
969 EXPORT_SYMBOL(fc_mount
);
971 struct vfsmount
*vfs_kern_mount(struct file_system_type
*type
,
972 int flags
, const char *name
,
975 struct fs_context
*fc
;
976 struct vfsmount
*mnt
;
980 return ERR_PTR(-EINVAL
);
982 fc
= fs_context_for_mount(type
, flags
);
987 ret
= vfs_parse_fs_string(fc
, "source",
990 ret
= parse_monolithic_mount_data(fc
, data
);
999 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
1002 vfs_submount(const struct dentry
*mountpoint
, struct file_system_type
*type
,
1003 const char *name
, void *data
)
1005 /* Until it is worked out how to pass the user namespace
1006 * through from the parent mount to the submount don't support
1007 * unprivileged mounts with submounts.
1009 if (mountpoint
->d_sb
->s_user_ns
!= &init_user_ns
)
1010 return ERR_PTR(-EPERM
);
1012 return vfs_kern_mount(type
, SB_SUBMOUNT
, name
, data
);
1014 EXPORT_SYMBOL_GPL(vfs_submount
);
1016 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
1019 struct super_block
*sb
= old
->mnt
.mnt_sb
;
1023 mnt
= alloc_vfsmnt(old
->mnt_devname
);
1025 return ERR_PTR(-ENOMEM
);
1027 if (flag
& (CL_SLAVE
| CL_PRIVATE
| CL_SHARED_TO_SLAVE
))
1028 mnt
->mnt_group_id
= 0; /* not a peer of original */
1030 mnt
->mnt_group_id
= old
->mnt_group_id
;
1032 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
1033 err
= mnt_alloc_group_id(mnt
);
1038 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
;
1039 mnt
->mnt
.mnt_flags
&= ~(MNT_WRITE_HOLD
|MNT_MARKED
|MNT_INTERNAL
);
1041 atomic_inc(&sb
->s_active
);
1042 mnt
->mnt
.mnt_sb
= sb
;
1043 mnt
->mnt
.mnt_root
= dget(root
);
1044 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1045 mnt
->mnt_parent
= mnt
;
1047 list_add_tail(&mnt
->mnt_instance
, &sb
->s_mounts
);
1048 unlock_mount_hash();
1050 if ((flag
& CL_SLAVE
) ||
1051 ((flag
& CL_SHARED_TO_SLAVE
) && IS_MNT_SHARED(old
))) {
1052 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
1053 mnt
->mnt_master
= old
;
1054 CLEAR_MNT_SHARED(mnt
);
1055 } else if (!(flag
& CL_PRIVATE
)) {
1056 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
1057 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
1058 if (IS_MNT_SLAVE(old
))
1059 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
1060 mnt
->mnt_master
= old
->mnt_master
;
1062 CLEAR_MNT_SHARED(mnt
);
1064 if (flag
& CL_MAKE_SHARED
)
1065 set_mnt_shared(mnt
);
1067 /* stick the duplicate mount on the same expiry list
1068 * as the original if that was on one */
1069 if (flag
& CL_EXPIRE
) {
1070 if (!list_empty(&old
->mnt_expire
))
1071 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
1079 return ERR_PTR(err
);
1082 static void cleanup_mnt(struct mount
*mnt
)
1084 struct hlist_node
*p
;
1087 * The warning here probably indicates that somebody messed
1088 * up a mnt_want/drop_write() pair. If this happens, the
1089 * filesystem was probably unable to make r/w->r/o transitions.
1090 * The locking used to deal with mnt_count decrement provides barriers,
1091 * so mnt_get_writers() below is safe.
1093 WARN_ON(mnt_get_writers(mnt
));
1094 if (unlikely(mnt
->mnt_pins
.first
))
1096 hlist_for_each_entry_safe(m
, p
, &mnt
->mnt_stuck_children
, mnt_umount
) {
1097 hlist_del(&m
->mnt_umount
);
1100 fsnotify_vfsmount_delete(&mnt
->mnt
);
1101 dput(mnt
->mnt
.mnt_root
);
1102 deactivate_super(mnt
->mnt
.mnt_sb
);
1104 call_rcu(&mnt
->mnt_rcu
, delayed_free_vfsmnt
);
1107 static void __cleanup_mnt(struct rcu_head
*head
)
1109 cleanup_mnt(container_of(head
, struct mount
, mnt_rcu
));
1112 static LLIST_HEAD(delayed_mntput_list
);
1113 static void delayed_mntput(struct work_struct
*unused
)
1115 struct llist_node
*node
= llist_del_all(&delayed_mntput_list
);
1116 struct mount
*m
, *t
;
1118 llist_for_each_entry_safe(m
, t
, node
, mnt_llist
)
1121 static DECLARE_DELAYED_WORK(delayed_mntput_work
, delayed_mntput
);
1123 static void mntput_no_expire(struct mount
*mnt
)
1128 if (likely(READ_ONCE(mnt
->mnt_ns
))) {
1130 * Since we don't do lock_mount_hash() here,
1131 * ->mnt_ns can change under us. However, if it's
1132 * non-NULL, then there's a reference that won't
1133 * be dropped until after an RCU delay done after
1134 * turning ->mnt_ns NULL. So if we observe it
1135 * non-NULL under rcu_read_lock(), the reference
1136 * we are dropping is not the final one.
1138 mnt_add_count(mnt
, -1);
1144 * make sure that if __legitimize_mnt() has not seen us grab
1145 * mount_lock, we'll see their refcount increment here.
1148 mnt_add_count(mnt
, -1);
1149 if (mnt_get_count(mnt
)) {
1151 unlock_mount_hash();
1154 if (unlikely(mnt
->mnt
.mnt_flags
& MNT_DOOMED
)) {
1156 unlock_mount_hash();
1159 mnt
->mnt
.mnt_flags
|= MNT_DOOMED
;
1162 list_del(&mnt
->mnt_instance
);
1164 if (unlikely(!list_empty(&mnt
->mnt_mounts
))) {
1165 struct mount
*p
, *tmp
;
1166 list_for_each_entry_safe(p
, tmp
, &mnt
->mnt_mounts
, mnt_child
) {
1167 __put_mountpoint(unhash_mnt(p
), &list
);
1168 hlist_add_head(&p
->mnt_umount
, &mnt
->mnt_stuck_children
);
1171 unlock_mount_hash();
1172 shrink_dentry_list(&list
);
1174 if (likely(!(mnt
->mnt
.mnt_flags
& MNT_INTERNAL
))) {
1175 struct task_struct
*task
= current
;
1176 if (likely(!(task
->flags
& PF_KTHREAD
))) {
1177 init_task_work(&mnt
->mnt_rcu
, __cleanup_mnt
);
1178 if (!task_work_add(task
, &mnt
->mnt_rcu
, true))
1181 if (llist_add(&mnt
->mnt_llist
, &delayed_mntput_list
))
1182 schedule_delayed_work(&delayed_mntput_work
, 1);
1188 void mntput(struct vfsmount
*mnt
)
1191 struct mount
*m
= real_mount(mnt
);
1192 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1193 if (unlikely(m
->mnt_expiry_mark
))
1194 m
->mnt_expiry_mark
= 0;
1195 mntput_no_expire(m
);
1198 EXPORT_SYMBOL(mntput
);
1200 struct vfsmount
*mntget(struct vfsmount
*mnt
)
1203 mnt_add_count(real_mount(mnt
), 1);
1206 EXPORT_SYMBOL(mntget
);
1208 /* path_is_mountpoint() - Check if path is a mount in the current
1211 * d_mountpoint() can only be used reliably to establish if a dentry is
1212 * not mounted in any namespace and that common case is handled inline.
1213 * d_mountpoint() isn't aware of the possibility there may be multiple
1214 * mounts using a given dentry in a different namespace. This function
1215 * checks if the passed in path is a mountpoint rather than the dentry
1218 bool path_is_mountpoint(const struct path
*path
)
1223 if (!d_mountpoint(path
->dentry
))
1228 seq
= read_seqbegin(&mount_lock
);
1229 res
= __path_is_mountpoint(path
);
1230 } while (read_seqretry(&mount_lock
, seq
));
1235 EXPORT_SYMBOL(path_is_mountpoint
);
1237 struct vfsmount
*mnt_clone_internal(const struct path
*path
)
1240 p
= clone_mnt(real_mount(path
->mnt
), path
->dentry
, CL_PRIVATE
);
1243 p
->mnt
.mnt_flags
|= MNT_INTERNAL
;
1247 #ifdef CONFIG_PROC_FS
1248 /* iterator; we want it to have access to namespace_sem, thus here... */
1249 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
1251 struct proc_mounts
*p
= m
->private;
1253 down_read(&namespace_sem
);
1254 if (p
->cached_event
== p
->ns
->event
) {
1255 void *v
= p
->cached_mount
;
1256 if (*pos
== p
->cached_index
)
1258 if (*pos
== p
->cached_index
+ 1) {
1259 v
= seq_list_next(v
, &p
->ns
->list
, &p
->cached_index
);
1260 return p
->cached_mount
= v
;
1264 p
->cached_event
= p
->ns
->event
;
1265 p
->cached_mount
= seq_list_start(&p
->ns
->list
, *pos
);
1266 p
->cached_index
= *pos
;
1267 return p
->cached_mount
;
1270 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
1272 struct proc_mounts
*p
= m
->private;
1274 p
->cached_mount
= seq_list_next(v
, &p
->ns
->list
, pos
);
1275 p
->cached_index
= *pos
;
1276 return p
->cached_mount
;
1279 static void m_stop(struct seq_file
*m
, void *v
)
1281 up_read(&namespace_sem
);
1284 static int m_show(struct seq_file
*m
, void *v
)
1286 struct proc_mounts
*p
= m
->private;
1287 struct mount
*r
= list_entry(v
, struct mount
, mnt_list
);
1288 return p
->show(m
, &r
->mnt
);
1291 const struct seq_operations mounts_op
= {
1297 #endif /* CONFIG_PROC_FS */
1300 * may_umount_tree - check if a mount tree is busy
1301 * @mnt: root of mount tree
1303 * This is called to check if a tree of mounts has any
1304 * open files, pwds, chroots or sub mounts that are
1307 int may_umount_tree(struct vfsmount
*m
)
1309 struct mount
*mnt
= real_mount(m
);
1310 int actual_refs
= 0;
1311 int minimum_refs
= 0;
1315 /* write lock needed for mnt_get_count */
1317 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1318 actual_refs
+= mnt_get_count(p
);
1321 unlock_mount_hash();
1323 if (actual_refs
> minimum_refs
)
1329 EXPORT_SYMBOL(may_umount_tree
);
1332 * may_umount - check if a mount point is busy
1333 * @mnt: root of mount
1335 * This is called to check if a mount point has any
1336 * open files, pwds, chroots or sub mounts. If the
1337 * mount has sub mounts this will return busy
1338 * regardless of whether the sub mounts are busy.
1340 * Doesn't take quota and stuff into account. IOW, in some cases it will
1341 * give false negatives. The main reason why it's here is that we need
1342 * a non-destructive way to look for easily umountable filesystems.
1344 int may_umount(struct vfsmount
*mnt
)
1347 down_read(&namespace_sem
);
1349 if (propagate_mount_busy(real_mount(mnt
), 2))
1351 unlock_mount_hash();
1352 up_read(&namespace_sem
);
1356 EXPORT_SYMBOL(may_umount
);
1358 static void namespace_unlock(void)
1360 struct hlist_head head
;
1361 struct hlist_node
*p
;
1365 hlist_move_list(&unmounted
, &head
);
1366 list_splice_init(&ex_mountpoints
, &list
);
1368 up_write(&namespace_sem
);
1370 shrink_dentry_list(&list
);
1372 if (likely(hlist_empty(&head
)))
1375 synchronize_rcu_expedited();
1377 hlist_for_each_entry_safe(m
, p
, &head
, mnt_umount
) {
1378 hlist_del(&m
->mnt_umount
);
1383 static inline void namespace_lock(void)
1385 down_write(&namespace_sem
);
1388 enum umount_tree_flags
{
1390 UMOUNT_PROPAGATE
= 2,
1391 UMOUNT_CONNECTED
= 4,
1394 static bool disconnect_mount(struct mount
*mnt
, enum umount_tree_flags how
)
1396 /* Leaving mounts connected is only valid for lazy umounts */
1397 if (how
& UMOUNT_SYNC
)
1400 /* A mount without a parent has nothing to be connected to */
1401 if (!mnt_has_parent(mnt
))
1404 /* Because the reference counting rules change when mounts are
1405 * unmounted and connected, umounted mounts may not be
1406 * connected to mounted mounts.
1408 if (!(mnt
->mnt_parent
->mnt
.mnt_flags
& MNT_UMOUNT
))
1411 /* Has it been requested that the mount remain connected? */
1412 if (how
& UMOUNT_CONNECTED
)
1415 /* Is the mount locked such that it needs to remain connected? */
1416 if (IS_MNT_LOCKED(mnt
))
1419 /* By default disconnect the mount */
1424 * mount_lock must be held
1425 * namespace_sem must be held for write
1427 static void umount_tree(struct mount
*mnt
, enum umount_tree_flags how
)
1429 LIST_HEAD(tmp_list
);
1432 if (how
& UMOUNT_PROPAGATE
)
1433 propagate_mount_unlock(mnt
);
1435 /* Gather the mounts to umount */
1436 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1437 p
->mnt
.mnt_flags
|= MNT_UMOUNT
;
1438 list_move(&p
->mnt_list
, &tmp_list
);
1441 /* Hide the mounts from mnt_mounts */
1442 list_for_each_entry(p
, &tmp_list
, mnt_list
) {
1443 list_del_init(&p
->mnt_child
);
1446 /* Add propogated mounts to the tmp_list */
1447 if (how
& UMOUNT_PROPAGATE
)
1448 propagate_umount(&tmp_list
);
1450 while (!list_empty(&tmp_list
)) {
1451 struct mnt_namespace
*ns
;
1453 p
= list_first_entry(&tmp_list
, struct mount
, mnt_list
);
1454 list_del_init(&p
->mnt_expire
);
1455 list_del_init(&p
->mnt_list
);
1459 __touch_mnt_namespace(ns
);
1462 if (how
& UMOUNT_SYNC
)
1463 p
->mnt
.mnt_flags
|= MNT_SYNC_UMOUNT
;
1465 disconnect
= disconnect_mount(p
, how
);
1466 if (mnt_has_parent(p
)) {
1467 mnt_add_count(p
->mnt_parent
, -1);
1469 /* Don't forget about p */
1470 list_add_tail(&p
->mnt_child
, &p
->mnt_parent
->mnt_mounts
);
1475 change_mnt_propagation(p
, MS_PRIVATE
);
1477 hlist_add_head(&p
->mnt_umount
, &unmounted
);
1481 static void shrink_submounts(struct mount
*mnt
);
1483 static int do_umount_root(struct super_block
*sb
)
1487 down_write(&sb
->s_umount
);
1488 if (!sb_rdonly(sb
)) {
1489 struct fs_context
*fc
;
1491 fc
= fs_context_for_reconfigure(sb
->s_root
, SB_RDONLY
,
1496 ret
= parse_monolithic_mount_data(fc
, NULL
);
1498 ret
= reconfigure_super(fc
);
1502 up_write(&sb
->s_umount
);
1506 static int do_umount(struct mount
*mnt
, int flags
)
1508 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1511 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1516 * Allow userspace to request a mountpoint be expired rather than
1517 * unmounting unconditionally. Unmount only happens if:
1518 * (1) the mark is already set (the mark is cleared by mntput())
1519 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1521 if (flags
& MNT_EXPIRE
) {
1522 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1523 flags
& (MNT_FORCE
| MNT_DETACH
))
1527 * probably don't strictly need the lock here if we examined
1528 * all race cases, but it's a slowpath.
1531 if (mnt_get_count(mnt
) != 2) {
1532 unlock_mount_hash();
1535 unlock_mount_hash();
1537 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1542 * If we may have to abort operations to get out of this
1543 * mount, and they will themselves hold resources we must
1544 * allow the fs to do things. In the Unix tradition of
1545 * 'Gee thats tricky lets do it in userspace' the umount_begin
1546 * might fail to complete on the first run through as other tasks
1547 * must return, and the like. Thats for the mount program to worry
1548 * about for the moment.
1551 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1552 sb
->s_op
->umount_begin(sb
);
1556 * No sense to grab the lock for this test, but test itself looks
1557 * somewhat bogus. Suggestions for better replacement?
1558 * Ho-hum... In principle, we might treat that as umount + switch
1559 * to rootfs. GC would eventually take care of the old vfsmount.
1560 * Actually it makes sense, especially if rootfs would contain a
1561 * /reboot - static binary that would close all descriptors and
1562 * call reboot(9). Then init(8) could umount root and exec /reboot.
1564 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1566 * Special case for "unmounting" root ...
1567 * we just try to remount it readonly.
1569 if (!ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
))
1571 return do_umount_root(sb
);
1577 /* Recheck MNT_LOCKED with the locks held */
1579 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
1583 if (flags
& MNT_DETACH
) {
1584 if (!list_empty(&mnt
->mnt_list
))
1585 umount_tree(mnt
, UMOUNT_PROPAGATE
);
1588 shrink_submounts(mnt
);
1590 if (!propagate_mount_busy(mnt
, 2)) {
1591 if (!list_empty(&mnt
->mnt_list
))
1592 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
1597 unlock_mount_hash();
1603 * __detach_mounts - lazily unmount all mounts on the specified dentry
1605 * During unlink, rmdir, and d_drop it is possible to loose the path
1606 * to an existing mountpoint, and wind up leaking the mount.
1607 * detach_mounts allows lazily unmounting those mounts instead of
1610 * The caller may hold dentry->d_inode->i_mutex.
1612 void __detach_mounts(struct dentry
*dentry
)
1614 struct mountpoint
*mp
;
1619 mp
= lookup_mountpoint(dentry
);
1624 while (!hlist_empty(&mp
->m_list
)) {
1625 mnt
= hlist_entry(mp
->m_list
.first
, struct mount
, mnt_mp_list
);
1626 if (mnt
->mnt
.mnt_flags
& MNT_UMOUNT
) {
1628 hlist_add_head(&mnt
->mnt_umount
, &unmounted
);
1630 else umount_tree(mnt
, UMOUNT_CONNECTED
);
1634 unlock_mount_hash();
1639 * Is the caller allowed to modify his namespace?
1641 static inline bool may_mount(void)
1643 return ns_capable(current
->nsproxy
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
);
1646 static inline bool may_mandlock(void)
1648 #ifndef CONFIG_MANDATORY_FILE_LOCKING
1651 return capable(CAP_SYS_ADMIN
);
1655 * Now umount can handle mount points as well as block devices.
1656 * This is important for filesystems which use unnamed block devices.
1658 * We now support a flag for forced unmount like the other 'big iron'
1659 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1662 int ksys_umount(char __user
*name
, int flags
)
1667 int lookup_flags
= 0;
1669 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1675 if (!(flags
& UMOUNT_NOFOLLOW
))
1676 lookup_flags
|= LOOKUP_FOLLOW
;
1678 lookup_flags
|= LOOKUP_NO_EVAL
;
1680 retval
= user_path_mountpoint_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1683 mnt
= real_mount(path
.mnt
);
1685 if (path
.dentry
!= path
.mnt
->mnt_root
)
1687 if (!check_mnt(mnt
))
1689 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
) /* Check optimistically */
1692 if (flags
& MNT_FORCE
&& !capable(CAP_SYS_ADMIN
))
1695 retval
= do_umount(mnt
, flags
);
1697 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1699 mntput_no_expire(mnt
);
1704 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1706 return ksys_umount(name
, flags
);
1709 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1712 * The 2.0 compatible umount. No flags.
1714 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1716 return ksys_umount(name
, 0);
1721 static bool is_mnt_ns_file(struct dentry
*dentry
)
1723 /* Is this a proxy for a mount namespace? */
1724 return dentry
->d_op
== &ns_dentry_operations
&&
1725 dentry
->d_fsdata
== &mntns_operations
;
1728 struct mnt_namespace
*to_mnt_ns(struct ns_common
*ns
)
1730 return container_of(ns
, struct mnt_namespace
, ns
);
1733 static bool mnt_ns_loop(struct dentry
*dentry
)
1735 /* Could bind mounting the mount namespace inode cause a
1736 * mount namespace loop?
1738 struct mnt_namespace
*mnt_ns
;
1739 if (!is_mnt_ns_file(dentry
))
1742 mnt_ns
= to_mnt_ns(get_proc_ns(dentry
->d_inode
));
1743 return current
->nsproxy
->mnt_ns
->seq
>= mnt_ns
->seq
;
1746 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1749 struct mount
*res
, *p
, *q
, *r
, *parent
;
1751 if (!(flag
& CL_COPY_UNBINDABLE
) && IS_MNT_UNBINDABLE(mnt
))
1752 return ERR_PTR(-EINVAL
);
1754 if (!(flag
& CL_COPY_MNT_NS_FILE
) && is_mnt_ns_file(dentry
))
1755 return ERR_PTR(-EINVAL
);
1757 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1761 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1764 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1766 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1769 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1770 if (!(flag
& CL_COPY_UNBINDABLE
) &&
1771 IS_MNT_UNBINDABLE(s
)) {
1772 if (s
->mnt
.mnt_flags
& MNT_LOCKED
) {
1773 /* Both unbindable and locked. */
1774 q
= ERR_PTR(-EPERM
);
1777 s
= skip_mnt_tree(s
);
1781 if (!(flag
& CL_COPY_MNT_NS_FILE
) &&
1782 is_mnt_ns_file(s
->mnt
.mnt_root
)) {
1783 s
= skip_mnt_tree(s
);
1786 while (p
!= s
->mnt_parent
) {
1792 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
1796 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1797 attach_mnt(q
, parent
, p
->mnt_mp
);
1798 unlock_mount_hash();
1805 umount_tree(res
, UMOUNT_SYNC
);
1806 unlock_mount_hash();
1811 /* Caller should check returned pointer for errors */
1813 struct vfsmount
*collect_mounts(const struct path
*path
)
1817 if (!check_mnt(real_mount(path
->mnt
)))
1818 tree
= ERR_PTR(-EINVAL
);
1820 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
1821 CL_COPY_ALL
| CL_PRIVATE
);
1824 return ERR_CAST(tree
);
1828 static void free_mnt_ns(struct mnt_namespace
*);
1829 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*, bool);
1831 void dissolve_on_fput(struct vfsmount
*mnt
)
1833 struct mnt_namespace
*ns
;
1836 ns
= real_mount(mnt
)->mnt_ns
;
1839 umount_tree(real_mount(mnt
), UMOUNT_CONNECTED
);
1843 unlock_mount_hash();
1849 void drop_collected_mounts(struct vfsmount
*mnt
)
1853 umount_tree(real_mount(mnt
), 0);
1854 unlock_mount_hash();
1859 * clone_private_mount - create a private clone of a path
1861 * This creates a new vfsmount, which will be the clone of @path. The new will
1862 * not be attached anywhere in the namespace and will be private (i.e. changes
1863 * to the originating mount won't be propagated into this).
1865 * Release with mntput().
1867 struct vfsmount
*clone_private_mount(const struct path
*path
)
1869 struct mount
*old_mnt
= real_mount(path
->mnt
);
1870 struct mount
*new_mnt
;
1872 if (IS_MNT_UNBINDABLE(old_mnt
))
1873 return ERR_PTR(-EINVAL
);
1875 new_mnt
= clone_mnt(old_mnt
, path
->dentry
, CL_PRIVATE
);
1876 if (IS_ERR(new_mnt
))
1877 return ERR_CAST(new_mnt
);
1879 return &new_mnt
->mnt
;
1881 EXPORT_SYMBOL_GPL(clone_private_mount
);
1883 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1884 struct vfsmount
*root
)
1887 int res
= f(root
, arg
);
1890 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
1891 res
= f(&mnt
->mnt
, arg
);
1898 static void lock_mnt_tree(struct mount
*mnt
)
1902 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1903 int flags
= p
->mnt
.mnt_flags
;
1904 /* Don't allow unprivileged users to change mount flags */
1905 flags
|= MNT_LOCK_ATIME
;
1907 if (flags
& MNT_READONLY
)
1908 flags
|= MNT_LOCK_READONLY
;
1910 if (flags
& MNT_NODEV
)
1911 flags
|= MNT_LOCK_NODEV
;
1913 if (flags
& MNT_NOSUID
)
1914 flags
|= MNT_LOCK_NOSUID
;
1916 if (flags
& MNT_NOEXEC
)
1917 flags
|= MNT_LOCK_NOEXEC
;
1918 /* Don't allow unprivileged users to reveal what is under a mount */
1919 if (list_empty(&p
->mnt_expire
))
1920 flags
|= MNT_LOCKED
;
1921 p
->mnt
.mnt_flags
= flags
;
1925 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
1929 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
1930 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
1931 mnt_release_group_id(p
);
1935 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
1939 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
1940 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
1941 int err
= mnt_alloc_group_id(p
);
1943 cleanup_group_ids(mnt
, p
);
1952 int count_mounts(struct mnt_namespace
*ns
, struct mount
*mnt
)
1954 unsigned int max
= READ_ONCE(sysctl_mount_max
);
1955 unsigned int mounts
= 0, old
, pending
, sum
;
1958 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
1962 pending
= ns
->pending_mounts
;
1963 sum
= old
+ pending
;
1967 (mounts
> (max
- sum
)))
1970 ns
->pending_mounts
= pending
+ mounts
;
1975 * @source_mnt : mount tree to be attached
1976 * @nd : place the mount tree @source_mnt is attached
1977 * @parent_nd : if non-null, detach the source_mnt from its parent and
1978 * store the parent mount and mountpoint dentry.
1979 * (done when source_mnt is moved)
1981 * NOTE: in the table below explains the semantics when a source mount
1982 * of a given type is attached to a destination mount of a given type.
1983 * ---------------------------------------------------------------------------
1984 * | BIND MOUNT OPERATION |
1985 * |**************************************************************************
1986 * | source-->| shared | private | slave | unbindable |
1990 * |**************************************************************************
1991 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1993 * |non-shared| shared (+) | private | slave (*) | invalid |
1994 * ***************************************************************************
1995 * A bind operation clones the source mount and mounts the clone on the
1996 * destination mount.
1998 * (++) the cloned mount is propagated to all the mounts in the propagation
1999 * tree of the destination mount and the cloned mount is added to
2000 * the peer group of the source mount.
2001 * (+) the cloned mount is created under the destination mount and is marked
2002 * as shared. The cloned mount is added to the peer group of the source
2004 * (+++) the mount is propagated to all the mounts in the propagation tree
2005 * of the destination mount and the cloned mount is made slave
2006 * of the same master as that of the source mount. The cloned mount
2007 * is marked as 'shared and slave'.
2008 * (*) the cloned mount is made a slave of the same master as that of the
2011 * ---------------------------------------------------------------------------
2012 * | MOVE MOUNT OPERATION |
2013 * |**************************************************************************
2014 * | source-->| shared | private | slave | unbindable |
2018 * |**************************************************************************
2019 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2021 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2022 * ***************************************************************************
2024 * (+) the mount is moved to the destination. And is then propagated to
2025 * all the mounts in the propagation tree of the destination mount.
2026 * (+*) the mount is moved to the destination.
2027 * (+++) the mount is moved to the destination and is then propagated to
2028 * all the mounts belonging to the destination mount's propagation tree.
2029 * the mount is marked as 'shared and slave'.
2030 * (*) the mount continues to be a slave at the new location.
2032 * if the source mount is a tree, the operations explained above is
2033 * applied to each mount in the tree.
2034 * Must be called without spinlocks held, since this function can sleep
2037 static int attach_recursive_mnt(struct mount
*source_mnt
,
2038 struct mount
*dest_mnt
,
2039 struct mountpoint
*dest_mp
,
2042 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2043 HLIST_HEAD(tree_list
);
2044 struct mnt_namespace
*ns
= dest_mnt
->mnt_ns
;
2045 struct mountpoint
*smp
;
2046 struct mount
*child
, *p
;
2047 struct hlist_node
*n
;
2050 /* Preallocate a mountpoint in case the new mounts need
2051 * to be tucked under other mounts.
2053 smp
= get_mountpoint(source_mnt
->mnt
.mnt_root
);
2055 return PTR_ERR(smp
);
2057 /* Is there space to add these mounts to the mount namespace? */
2059 err
= count_mounts(ns
, source_mnt
);
2064 if (IS_MNT_SHARED(dest_mnt
)) {
2065 err
= invent_group_ids(source_mnt
, true);
2068 err
= propagate_mnt(dest_mnt
, dest_mp
, source_mnt
, &tree_list
);
2071 goto out_cleanup_ids
;
2072 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
2078 unhash_mnt(source_mnt
);
2079 attach_mnt(source_mnt
, dest_mnt
, dest_mp
);
2080 touch_mnt_namespace(source_mnt
->mnt_ns
);
2082 if (source_mnt
->mnt_ns
) {
2083 /* move from anon - the caller will destroy */
2084 list_del_init(&source_mnt
->mnt_ns
->list
);
2086 mnt_set_mountpoint(dest_mnt
, dest_mp
, source_mnt
);
2087 commit_tree(source_mnt
);
2090 hlist_for_each_entry_safe(child
, n
, &tree_list
, mnt_hash
) {
2092 hlist_del_init(&child
->mnt_hash
);
2093 q
= __lookup_mnt(&child
->mnt_parent
->mnt
,
2094 child
->mnt_mountpoint
);
2096 mnt_change_mountpoint(child
, smp
, q
);
2097 /* Notice when we are propagating across user namespaces */
2098 if (child
->mnt_parent
->mnt_ns
->user_ns
!= user_ns
)
2099 lock_mnt_tree(child
);
2100 child
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2103 put_mountpoint(smp
);
2104 unlock_mount_hash();
2109 while (!hlist_empty(&tree_list
)) {
2110 child
= hlist_entry(tree_list
.first
, struct mount
, mnt_hash
);
2111 child
->mnt_parent
->mnt_ns
->pending_mounts
= 0;
2112 umount_tree(child
, UMOUNT_SYNC
);
2114 unlock_mount_hash();
2115 cleanup_group_ids(source_mnt
, NULL
);
2117 ns
->pending_mounts
= 0;
2119 read_seqlock_excl(&mount_lock
);
2120 put_mountpoint(smp
);
2121 read_sequnlock_excl(&mount_lock
);
2126 static struct mountpoint
*lock_mount(struct path
*path
)
2128 struct vfsmount
*mnt
;
2129 struct dentry
*dentry
= path
->dentry
;
2131 inode_lock(dentry
->d_inode
);
2132 if (unlikely(cant_mount(dentry
))) {
2133 inode_unlock(dentry
->d_inode
);
2134 return ERR_PTR(-ENOENT
);
2137 mnt
= lookup_mnt(path
);
2139 struct mountpoint
*mp
= get_mountpoint(dentry
);
2142 inode_unlock(dentry
->d_inode
);
2148 inode_unlock(path
->dentry
->d_inode
);
2151 dentry
= path
->dentry
= dget(mnt
->mnt_root
);
2155 static void unlock_mount(struct mountpoint
*where
)
2157 struct dentry
*dentry
= where
->m_dentry
;
2159 read_seqlock_excl(&mount_lock
);
2160 put_mountpoint(where
);
2161 read_sequnlock_excl(&mount_lock
);
2164 inode_unlock(dentry
->d_inode
);
2167 static int graft_tree(struct mount
*mnt
, struct mount
*p
, struct mountpoint
*mp
)
2169 if (mnt
->mnt
.mnt_sb
->s_flags
& SB_NOUSER
)
2172 if (d_is_dir(mp
->m_dentry
) !=
2173 d_is_dir(mnt
->mnt
.mnt_root
))
2176 return attach_recursive_mnt(mnt
, p
, mp
, false);
2180 * Sanity check the flags to change_mnt_propagation.
2183 static int flags_to_propagation_type(int ms_flags
)
2185 int type
= ms_flags
& ~(MS_REC
| MS_SILENT
);
2187 /* Fail if any non-propagation flags are set */
2188 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2190 /* Only one propagation flag should be set */
2191 if (!is_power_of_2(type
))
2197 * recursively change the type of the mountpoint.
2199 static int do_change_type(struct path
*path
, int ms_flags
)
2202 struct mount
*mnt
= real_mount(path
->mnt
);
2203 int recurse
= ms_flags
& MS_REC
;
2207 if (path
->dentry
!= path
->mnt
->mnt_root
)
2210 type
= flags_to_propagation_type(ms_flags
);
2215 if (type
== MS_SHARED
) {
2216 err
= invent_group_ids(mnt
, recurse
);
2222 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
2223 change_mnt_propagation(m
, type
);
2224 unlock_mount_hash();
2231 static bool has_locked_children(struct mount
*mnt
, struct dentry
*dentry
)
2233 struct mount
*child
;
2234 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
2235 if (!is_subdir(child
->mnt_mountpoint
, dentry
))
2238 if (child
->mnt
.mnt_flags
& MNT_LOCKED
)
2244 static struct mount
*__do_loopback(struct path
*old_path
, int recurse
)
2246 struct mount
*mnt
= ERR_PTR(-EINVAL
), *old
= real_mount(old_path
->mnt
);
2248 if (IS_MNT_UNBINDABLE(old
))
2251 if (!check_mnt(old
) && old_path
->dentry
->d_op
!= &ns_dentry_operations
)
2254 if (!recurse
&& has_locked_children(old
, old_path
->dentry
))
2258 mnt
= copy_tree(old
, old_path
->dentry
, CL_COPY_MNT_NS_FILE
);
2260 mnt
= clone_mnt(old
, old_path
->dentry
, 0);
2263 mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2269 * do loopback mount.
2271 static int do_loopback(struct path
*path
, const char *old_name
,
2274 struct path old_path
;
2275 struct mount
*mnt
= NULL
, *parent
;
2276 struct mountpoint
*mp
;
2278 if (!old_name
|| !*old_name
)
2280 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
2285 if (mnt_ns_loop(old_path
.dentry
))
2288 mp
= lock_mount(path
);
2294 parent
= real_mount(path
->mnt
);
2295 if (!check_mnt(parent
))
2298 mnt
= __do_loopback(&old_path
, recurse
);
2304 err
= graft_tree(mnt
, parent
, mp
);
2307 umount_tree(mnt
, UMOUNT_SYNC
);
2308 unlock_mount_hash();
2313 path_put(&old_path
);
2317 static struct file
*open_detached_copy(struct path
*path
, bool recursive
)
2319 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2320 struct mnt_namespace
*ns
= alloc_mnt_ns(user_ns
, true);
2321 struct mount
*mnt
, *p
;
2325 return ERR_CAST(ns
);
2328 mnt
= __do_loopback(path
, recursive
);
2332 return ERR_CAST(mnt
);
2336 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2341 list_add_tail(&ns
->list
, &mnt
->mnt_list
);
2343 unlock_mount_hash();
2347 path
->mnt
= &mnt
->mnt
;
2348 file
= dentry_open(path
, O_PATH
, current_cred());
2350 dissolve_on_fput(path
->mnt
);
2352 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
2356 SYSCALL_DEFINE3(open_tree
, int, dfd
, const char *, filename
, unsigned, flags
)
2360 int lookup_flags
= LOOKUP_AUTOMOUNT
| LOOKUP_FOLLOW
;
2361 bool detached
= flags
& OPEN_TREE_CLONE
;
2365 BUILD_BUG_ON(OPEN_TREE_CLOEXEC
!= O_CLOEXEC
);
2367 if (flags
& ~(AT_EMPTY_PATH
| AT_NO_AUTOMOUNT
| AT_RECURSIVE
|
2368 AT_SYMLINK_NOFOLLOW
| OPEN_TREE_CLONE
|
2372 if ((flags
& (AT_RECURSIVE
| OPEN_TREE_CLONE
)) == AT_RECURSIVE
)
2375 if (flags
& AT_NO_AUTOMOUNT
)
2376 lookup_flags
&= ~LOOKUP_AUTOMOUNT
;
2377 if (flags
& AT_SYMLINK_NOFOLLOW
)
2378 lookup_flags
&= ~LOOKUP_FOLLOW
;
2379 if (flags
& AT_EMPTY_PATH
)
2380 lookup_flags
|= LOOKUP_EMPTY
;
2382 if (detached
&& !may_mount())
2385 fd
= get_unused_fd_flags(flags
& O_CLOEXEC
);
2389 error
= user_path_at(dfd
, filename
, lookup_flags
, &path
);
2390 if (unlikely(error
)) {
2391 file
= ERR_PTR(error
);
2394 file
= open_detached_copy(&path
, flags
& AT_RECURSIVE
);
2396 file
= dentry_open(&path
, O_PATH
, current_cred());
2401 return PTR_ERR(file
);
2403 fd_install(fd
, file
);
2408 * Don't allow locked mount flags to be cleared.
2410 * No locks need to be held here while testing the various MNT_LOCK
2411 * flags because those flags can never be cleared once they are set.
2413 static bool can_change_locked_flags(struct mount
*mnt
, unsigned int mnt_flags
)
2415 unsigned int fl
= mnt
->mnt
.mnt_flags
;
2417 if ((fl
& MNT_LOCK_READONLY
) &&
2418 !(mnt_flags
& MNT_READONLY
))
2421 if ((fl
& MNT_LOCK_NODEV
) &&
2422 !(mnt_flags
& MNT_NODEV
))
2425 if ((fl
& MNT_LOCK_NOSUID
) &&
2426 !(mnt_flags
& MNT_NOSUID
))
2429 if ((fl
& MNT_LOCK_NOEXEC
) &&
2430 !(mnt_flags
& MNT_NOEXEC
))
2433 if ((fl
& MNT_LOCK_ATIME
) &&
2434 ((fl
& MNT_ATIME_MASK
) != (mnt_flags
& MNT_ATIME_MASK
)))
2440 static int change_mount_ro_state(struct mount
*mnt
, unsigned int mnt_flags
)
2442 bool readonly_request
= (mnt_flags
& MNT_READONLY
);
2444 if (readonly_request
== __mnt_is_readonly(&mnt
->mnt
))
2447 if (readonly_request
)
2448 return mnt_make_readonly(mnt
);
2450 return __mnt_unmake_readonly(mnt
);
2454 * Update the user-settable attributes on a mount. The caller must hold
2455 * sb->s_umount for writing.
2457 static void set_mount_attributes(struct mount
*mnt
, unsigned int mnt_flags
)
2460 mnt_flags
|= mnt
->mnt
.mnt_flags
& ~MNT_USER_SETTABLE_MASK
;
2461 mnt
->mnt
.mnt_flags
= mnt_flags
;
2462 touch_mnt_namespace(mnt
->mnt_ns
);
2463 unlock_mount_hash();
2467 * Handle reconfiguration of the mountpoint only without alteration of the
2468 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2471 static int do_reconfigure_mnt(struct path
*path
, unsigned int mnt_flags
)
2473 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2474 struct mount
*mnt
= real_mount(path
->mnt
);
2477 if (!check_mnt(mnt
))
2480 if (path
->dentry
!= mnt
->mnt
.mnt_root
)
2483 if (!can_change_locked_flags(mnt
, mnt_flags
))
2486 down_write(&sb
->s_umount
);
2487 ret
= change_mount_ro_state(mnt
, mnt_flags
);
2489 set_mount_attributes(mnt
, mnt_flags
);
2490 up_write(&sb
->s_umount
);
2495 * change filesystem flags. dir should be a physical root of filesystem.
2496 * If you've mounted a non-root directory somewhere and want to do remount
2497 * on it - tough luck.
2499 static int do_remount(struct path
*path
, int ms_flags
, int sb_flags
,
2500 int mnt_flags
, void *data
)
2503 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2504 struct mount
*mnt
= real_mount(path
->mnt
);
2505 struct fs_context
*fc
;
2507 if (!check_mnt(mnt
))
2510 if (path
->dentry
!= path
->mnt
->mnt_root
)
2513 if (!can_change_locked_flags(mnt
, mnt_flags
))
2516 fc
= fs_context_for_reconfigure(path
->dentry
, sb_flags
, MS_RMT_MASK
);
2520 err
= parse_monolithic_mount_data(fc
, data
);
2522 down_write(&sb
->s_umount
);
2524 if (ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
)) {
2525 err
= reconfigure_super(fc
);
2527 set_mount_attributes(mnt
, mnt_flags
);
2529 up_write(&sb
->s_umount
);
2535 static inline int tree_contains_unbindable(struct mount
*mnt
)
2538 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2539 if (IS_MNT_UNBINDABLE(p
))
2546 * Check that there aren't references to earlier/same mount namespaces in the
2547 * specified subtree. Such references can act as pins for mount namespaces
2548 * that aren't checked by the mount-cycle checking code, thereby allowing
2549 * cycles to be made.
2551 static bool check_for_nsfs_mounts(struct mount
*subtree
)
2557 for (p
= subtree
; p
; p
= next_mnt(p
, subtree
))
2558 if (mnt_ns_loop(p
->mnt
.mnt_root
))
2563 unlock_mount_hash();
2567 static int do_move_mount(struct path
*old_path
, struct path
*new_path
)
2569 struct mnt_namespace
*ns
;
2572 struct mount
*parent
;
2573 struct mountpoint
*mp
, *old_mp
;
2577 mp
= lock_mount(new_path
);
2581 old
= real_mount(old_path
->mnt
);
2582 p
= real_mount(new_path
->mnt
);
2583 parent
= old
->mnt_parent
;
2584 attached
= mnt_has_parent(old
);
2585 old_mp
= old
->mnt_mp
;
2589 /* The mountpoint must be in our namespace. */
2593 /* The thing moved must be mounted... */
2594 if (!is_mounted(&old
->mnt
))
2597 /* ... and either ours or the root of anon namespace */
2598 if (!(attached
? check_mnt(old
) : is_anon_ns(ns
)))
2601 if (old
->mnt
.mnt_flags
& MNT_LOCKED
)
2604 if (old_path
->dentry
!= old_path
->mnt
->mnt_root
)
2607 if (d_is_dir(new_path
->dentry
) !=
2608 d_is_dir(old_path
->dentry
))
2611 * Don't move a mount residing in a shared parent.
2613 if (attached
&& IS_MNT_SHARED(parent
))
2616 * Don't move a mount tree containing unbindable mounts to a destination
2617 * mount which is shared.
2619 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
2622 if (!check_for_nsfs_mounts(old
))
2624 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
2628 err
= attach_recursive_mnt(old
, real_mount(new_path
->mnt
), mp
,
2633 /* if the mount is moved, it should no longer be expire
2635 list_del_init(&old
->mnt_expire
);
2637 put_mountpoint(old_mp
);
2642 mntput_no_expire(parent
);
2649 static int do_move_mount_old(struct path
*path
, const char *old_name
)
2651 struct path old_path
;
2654 if (!old_name
|| !*old_name
)
2657 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
2661 err
= do_move_mount(&old_path
, path
);
2662 path_put(&old_path
);
2667 * add a mount into a namespace's mount tree
2669 static int do_add_mount(struct mount
*newmnt
, struct path
*path
, int mnt_flags
)
2671 struct mountpoint
*mp
;
2672 struct mount
*parent
;
2675 mnt_flags
&= ~MNT_INTERNAL_FLAGS
;
2677 mp
= lock_mount(path
);
2681 parent
= real_mount(path
->mnt
);
2683 if (unlikely(!check_mnt(parent
))) {
2684 /* that's acceptable only for automounts done in private ns */
2685 if (!(mnt_flags
& MNT_SHRINKABLE
))
2687 /* ... and for those we'd better have mountpoint still alive */
2688 if (!parent
->mnt_ns
)
2692 /* Refuse the same filesystem on the same mount point */
2694 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
2695 path
->mnt
->mnt_root
== path
->dentry
)
2699 if (d_is_symlink(newmnt
->mnt
.mnt_root
))
2702 newmnt
->mnt
.mnt_flags
= mnt_flags
;
2703 err
= graft_tree(newmnt
, parent
, mp
);
2710 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
);
2713 * Create a new mount using a superblock configuration and request it
2714 * be added to the namespace tree.
2716 static int do_new_mount_fc(struct fs_context
*fc
, struct path
*mountpoint
,
2717 unsigned int mnt_flags
)
2719 struct vfsmount
*mnt
;
2720 struct super_block
*sb
= fc
->root
->d_sb
;
2723 error
= security_sb_kern_mount(sb
);
2724 if (!error
&& mount_too_revealing(sb
, &mnt_flags
))
2727 if (unlikely(error
)) {
2732 up_write(&sb
->s_umount
);
2734 mnt
= vfs_create_mount(fc
);
2736 return PTR_ERR(mnt
);
2738 error
= do_add_mount(real_mount(mnt
), mountpoint
, mnt_flags
);
2745 * create a new mount for userspace and request it to be added into the
2748 static int do_new_mount(struct path
*path
, const char *fstype
, int sb_flags
,
2749 int mnt_flags
, const char *name
, void *data
)
2751 struct file_system_type
*type
;
2752 struct fs_context
*fc
;
2753 const char *subtype
= NULL
;
2759 type
= get_fs_type(fstype
);
2763 if (type
->fs_flags
& FS_HAS_SUBTYPE
) {
2764 subtype
= strchr(fstype
, '.');
2768 put_filesystem(type
);
2776 fc
= fs_context_for_mount(type
, sb_flags
);
2777 put_filesystem(type
);
2782 err
= vfs_parse_fs_string(fc
, "subtype",
2783 subtype
, strlen(subtype
));
2785 err
= vfs_parse_fs_string(fc
, "source", name
, strlen(name
));
2787 err
= parse_monolithic_mount_data(fc
, data
);
2788 if (!err
&& !mount_capable(fc
))
2791 err
= vfs_get_tree(fc
);
2793 err
= do_new_mount_fc(fc
, path
, mnt_flags
);
2799 int finish_automount(struct vfsmount
*m
, struct path
*path
)
2801 struct mount
*mnt
= real_mount(m
);
2803 /* The new mount record should have at least 2 refs to prevent it being
2804 * expired before we get a chance to add it
2806 BUG_ON(mnt_get_count(mnt
) < 2);
2808 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
2809 m
->mnt_root
== path
->dentry
) {
2814 err
= do_add_mount(mnt
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
2818 /* remove m from any expiration list it may be on */
2819 if (!list_empty(&mnt
->mnt_expire
)) {
2821 list_del_init(&mnt
->mnt_expire
);
2830 * mnt_set_expiry - Put a mount on an expiration list
2831 * @mnt: The mount to list.
2832 * @expiry_list: The list to add the mount to.
2834 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
2838 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
2842 EXPORT_SYMBOL(mnt_set_expiry
);
2845 * process a list of expirable mountpoints with the intent of discarding any
2846 * mountpoints that aren't in use and haven't been touched since last we came
2849 void mark_mounts_for_expiry(struct list_head
*mounts
)
2851 struct mount
*mnt
, *next
;
2852 LIST_HEAD(graveyard
);
2854 if (list_empty(mounts
))
2860 /* extract from the expiration list every vfsmount that matches the
2861 * following criteria:
2862 * - only referenced by its parent vfsmount
2863 * - still marked for expiry (marked on the last call here; marks are
2864 * cleared by mntput())
2866 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
2867 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
2868 propagate_mount_busy(mnt
, 1))
2870 list_move(&mnt
->mnt_expire
, &graveyard
);
2872 while (!list_empty(&graveyard
)) {
2873 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
2874 touch_mnt_namespace(mnt
->mnt_ns
);
2875 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
2877 unlock_mount_hash();
2881 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
2884 * Ripoff of 'select_parent()'
2886 * search the list of submounts for a given mountpoint, and move any
2887 * shrinkable submounts to the 'graveyard' list.
2889 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
2891 struct mount
*this_parent
= parent
;
2892 struct list_head
*next
;
2896 next
= this_parent
->mnt_mounts
.next
;
2898 while (next
!= &this_parent
->mnt_mounts
) {
2899 struct list_head
*tmp
= next
;
2900 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
2903 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
2906 * Descend a level if the d_mounts list is non-empty.
2908 if (!list_empty(&mnt
->mnt_mounts
)) {
2913 if (!propagate_mount_busy(mnt
, 1)) {
2914 list_move_tail(&mnt
->mnt_expire
, graveyard
);
2919 * All done at this level ... ascend and resume the search
2921 if (this_parent
!= parent
) {
2922 next
= this_parent
->mnt_child
.next
;
2923 this_parent
= this_parent
->mnt_parent
;
2930 * process a list of expirable mountpoints with the intent of discarding any
2931 * submounts of a specific parent mountpoint
2933 * mount_lock must be held for write
2935 static void shrink_submounts(struct mount
*mnt
)
2937 LIST_HEAD(graveyard
);
2940 /* extract submounts of 'mountpoint' from the expiration list */
2941 while (select_submounts(mnt
, &graveyard
)) {
2942 while (!list_empty(&graveyard
)) {
2943 m
= list_first_entry(&graveyard
, struct mount
,
2945 touch_mnt_namespace(m
->mnt_ns
);
2946 umount_tree(m
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
2952 * Some copy_from_user() implementations do not return the exact number of
2953 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2954 * Note that this function differs from copy_from_user() in that it will oops
2955 * on bad values of `to', rather than returning a short copy.
2957 static long exact_copy_from_user(void *to
, const void __user
* from
,
2961 const char __user
*f
= from
;
2964 if (!access_ok(from
, n
))
2968 if (__get_user(c
, f
)) {
2979 void *copy_mount_options(const void __user
* data
)
2988 copy
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
2990 return ERR_PTR(-ENOMEM
);
2992 /* We only care that *some* data at the address the user
2993 * gave us is valid. Just in case, we'll zero
2994 * the remainder of the page.
2996 /* copy_from_user cannot cross TASK_SIZE ! */
2997 size
= TASK_SIZE
- (unsigned long)data
;
2998 if (size
> PAGE_SIZE
)
3001 i
= size
- exact_copy_from_user(copy
, data
, size
);
3004 return ERR_PTR(-EFAULT
);
3007 memset(copy
+ i
, 0, PAGE_SIZE
- i
);
3011 char *copy_mount_string(const void __user
*data
)
3013 return data
? strndup_user(data
, PATH_MAX
) : NULL
;
3017 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3018 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3020 * data is a (void *) that can point to any structure up to
3021 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3022 * information (or be NULL).
3024 * Pre-0.97 versions of mount() didn't have a flags word.
3025 * When the flags word was introduced its top half was required
3026 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3027 * Therefore, if this magic number is present, it carries no information
3028 * and must be discarded.
3030 long do_mount(const char *dev_name
, const char __user
*dir_name
,
3031 const char *type_page
, unsigned long flags
, void *data_page
)
3034 unsigned int mnt_flags
= 0, sb_flags
;
3038 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
3039 flags
&= ~MS_MGC_MSK
;
3041 /* Basic sanity checks */
3043 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
3045 if (flags
& MS_NOUSER
)
3048 /* ... and get the mountpoint */
3049 retval
= user_path(dir_name
, &path
);
3053 retval
= security_sb_mount(dev_name
, &path
,
3054 type_page
, flags
, data_page
);
3055 if (!retval
&& !may_mount())
3057 if (!retval
&& (flags
& SB_MANDLOCK
) && !may_mandlock())
3062 /* Default to relatime unless overriden */
3063 if (!(flags
& MS_NOATIME
))
3064 mnt_flags
|= MNT_RELATIME
;
3066 /* Separate the per-mountpoint flags */
3067 if (flags
& MS_NOSUID
)
3068 mnt_flags
|= MNT_NOSUID
;
3069 if (flags
& MS_NODEV
)
3070 mnt_flags
|= MNT_NODEV
;
3071 if (flags
& MS_NOEXEC
)
3072 mnt_flags
|= MNT_NOEXEC
;
3073 if (flags
& MS_NOATIME
)
3074 mnt_flags
|= MNT_NOATIME
;
3075 if (flags
& MS_NODIRATIME
)
3076 mnt_flags
|= MNT_NODIRATIME
;
3077 if (flags
& MS_STRICTATIME
)
3078 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
3079 if (flags
& MS_RDONLY
)
3080 mnt_flags
|= MNT_READONLY
;
3082 /* The default atime for remount is preservation */
3083 if ((flags
& MS_REMOUNT
) &&
3084 ((flags
& (MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
|
3085 MS_STRICTATIME
)) == 0)) {
3086 mnt_flags
&= ~MNT_ATIME_MASK
;
3087 mnt_flags
|= path
.mnt
->mnt_flags
& MNT_ATIME_MASK
;
3090 sb_flags
= flags
& (SB_RDONLY
|
3099 if ((flags
& (MS_REMOUNT
| MS_BIND
)) == (MS_REMOUNT
| MS_BIND
))
3100 retval
= do_reconfigure_mnt(&path
, mnt_flags
);
3101 else if (flags
& MS_REMOUNT
)
3102 retval
= do_remount(&path
, flags
, sb_flags
, mnt_flags
,
3104 else if (flags
& MS_BIND
)
3105 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
3106 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
3107 retval
= do_change_type(&path
, flags
);
3108 else if (flags
& MS_MOVE
)
3109 retval
= do_move_mount_old(&path
, dev_name
);
3111 retval
= do_new_mount(&path
, type_page
, sb_flags
, mnt_flags
,
3112 dev_name
, data_page
);
3118 static struct ucounts
*inc_mnt_namespaces(struct user_namespace
*ns
)
3120 return inc_ucount(ns
, current_euid(), UCOUNT_MNT_NAMESPACES
);
3123 static void dec_mnt_namespaces(struct ucounts
*ucounts
)
3125 dec_ucount(ucounts
, UCOUNT_MNT_NAMESPACES
);
3128 static void free_mnt_ns(struct mnt_namespace
*ns
)
3130 if (!is_anon_ns(ns
))
3131 ns_free_inum(&ns
->ns
);
3132 dec_mnt_namespaces(ns
->ucounts
);
3133 put_user_ns(ns
->user_ns
);
3138 * Assign a sequence number so we can detect when we attempt to bind
3139 * mount a reference to an older mount namespace into the current
3140 * mount namespace, preventing reference counting loops. A 64bit
3141 * number incrementing at 10Ghz will take 12,427 years to wrap which
3142 * is effectively never, so we can ignore the possibility.
3144 static atomic64_t mnt_ns_seq
= ATOMIC64_INIT(1);
3146 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*user_ns
, bool anon
)
3148 struct mnt_namespace
*new_ns
;
3149 struct ucounts
*ucounts
;
3152 ucounts
= inc_mnt_namespaces(user_ns
);
3154 return ERR_PTR(-ENOSPC
);
3156 new_ns
= kzalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
3158 dec_mnt_namespaces(ucounts
);
3159 return ERR_PTR(-ENOMEM
);
3162 ret
= ns_alloc_inum(&new_ns
->ns
);
3165 dec_mnt_namespaces(ucounts
);
3166 return ERR_PTR(ret
);
3169 new_ns
->ns
.ops
= &mntns_operations
;
3171 new_ns
->seq
= atomic64_add_return(1, &mnt_ns_seq
);
3172 atomic_set(&new_ns
->count
, 1);
3173 INIT_LIST_HEAD(&new_ns
->list
);
3174 init_waitqueue_head(&new_ns
->poll
);
3175 new_ns
->user_ns
= get_user_ns(user_ns
);
3176 new_ns
->ucounts
= ucounts
;
3181 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
3182 struct user_namespace
*user_ns
, struct fs_struct
*new_fs
)
3184 struct mnt_namespace
*new_ns
;
3185 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
3186 struct mount
*p
, *q
;
3193 if (likely(!(flags
& CLONE_NEWNS
))) {
3200 new_ns
= alloc_mnt_ns(user_ns
, false);
3205 /* First pass: copy the tree topology */
3206 copy_flags
= CL_COPY_UNBINDABLE
| CL_EXPIRE
;
3207 if (user_ns
!= ns
->user_ns
)
3208 copy_flags
|= CL_SHARED_TO_SLAVE
;
3209 new = copy_tree(old
, old
->mnt
.mnt_root
, copy_flags
);
3212 free_mnt_ns(new_ns
);
3213 return ERR_CAST(new);
3215 if (user_ns
!= ns
->user_ns
) {
3218 unlock_mount_hash();
3221 list_add_tail(&new_ns
->list
, &new->mnt_list
);
3224 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3225 * as belonging to new namespace. We have already acquired a private
3226 * fs_struct, so tsk->fs->lock is not needed.
3234 if (&p
->mnt
== new_fs
->root
.mnt
) {
3235 new_fs
->root
.mnt
= mntget(&q
->mnt
);
3238 if (&p
->mnt
== new_fs
->pwd
.mnt
) {
3239 new_fs
->pwd
.mnt
= mntget(&q
->mnt
);
3243 p
= next_mnt(p
, old
);
3244 q
= next_mnt(q
, new);
3247 while (p
->mnt
.mnt_root
!= q
->mnt
.mnt_root
)
3248 p
= next_mnt(p
, old
);
3260 struct dentry
*mount_subtree(struct vfsmount
*m
, const char *name
)
3262 struct mount
*mnt
= real_mount(m
);
3263 struct mnt_namespace
*ns
;
3264 struct super_block
*s
;
3268 ns
= alloc_mnt_ns(&init_user_ns
, true);
3271 return ERR_CAST(ns
);
3276 list_add(&mnt
->mnt_list
, &ns
->list
);
3278 err
= vfs_path_lookup(m
->mnt_root
, m
,
3279 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
3284 return ERR_PTR(err
);
3286 /* trade a vfsmount reference for active sb one */
3287 s
= path
.mnt
->mnt_sb
;
3288 atomic_inc(&s
->s_active
);
3290 /* lock the sucker */
3291 down_write(&s
->s_umount
);
3292 /* ... and return the root of (sub)tree on it */
3295 EXPORT_SYMBOL(mount_subtree
);
3297 int ksys_mount(const char __user
*dev_name
, const char __user
*dir_name
,
3298 const char __user
*type
, unsigned long flags
, void __user
*data
)
3305 kernel_type
= copy_mount_string(type
);
3306 ret
= PTR_ERR(kernel_type
);
3307 if (IS_ERR(kernel_type
))
3310 kernel_dev
= copy_mount_string(dev_name
);
3311 ret
= PTR_ERR(kernel_dev
);
3312 if (IS_ERR(kernel_dev
))
3315 options
= copy_mount_options(data
);
3316 ret
= PTR_ERR(options
);
3317 if (IS_ERR(options
))
3320 ret
= do_mount(kernel_dev
, dir_name
, kernel_type
, flags
, options
);
3331 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
3332 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
3334 return ksys_mount(dev_name
, dir_name
, type
, flags
, data
);
3338 * Create a kernel mount representation for a new, prepared superblock
3339 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3341 SYSCALL_DEFINE3(fsmount
, int, fs_fd
, unsigned int, flags
,
3342 unsigned int, attr_flags
)
3344 struct mnt_namespace
*ns
;
3345 struct fs_context
*fc
;
3347 struct path newmount
;
3350 unsigned int mnt_flags
= 0;
3356 if ((flags
& ~(FSMOUNT_CLOEXEC
)) != 0)
3359 if (attr_flags
& ~(MOUNT_ATTR_RDONLY
|
3364 MOUNT_ATTR_NODIRATIME
))
3367 if (attr_flags
& MOUNT_ATTR_RDONLY
)
3368 mnt_flags
|= MNT_READONLY
;
3369 if (attr_flags
& MOUNT_ATTR_NOSUID
)
3370 mnt_flags
|= MNT_NOSUID
;
3371 if (attr_flags
& MOUNT_ATTR_NODEV
)
3372 mnt_flags
|= MNT_NODEV
;
3373 if (attr_flags
& MOUNT_ATTR_NOEXEC
)
3374 mnt_flags
|= MNT_NOEXEC
;
3375 if (attr_flags
& MOUNT_ATTR_NODIRATIME
)
3376 mnt_flags
|= MNT_NODIRATIME
;
3378 switch (attr_flags
& MOUNT_ATTR__ATIME
) {
3379 case MOUNT_ATTR_STRICTATIME
:
3381 case MOUNT_ATTR_NOATIME
:
3382 mnt_flags
|= MNT_NOATIME
;
3384 case MOUNT_ATTR_RELATIME
:
3385 mnt_flags
|= MNT_RELATIME
;
3396 if (f
.file
->f_op
!= &fscontext_fops
)
3399 fc
= f
.file
->private_data
;
3401 ret
= mutex_lock_interruptible(&fc
->uapi_mutex
);
3405 /* There must be a valid superblock or we can't mount it */
3411 if (mount_too_revealing(fc
->root
->d_sb
, &mnt_flags
)) {
3412 pr_warn("VFS: Mount too revealing\n");
3417 if (fc
->phase
!= FS_CONTEXT_AWAITING_MOUNT
)
3421 if ((fc
->sb_flags
& SB_MANDLOCK
) && !may_mandlock())
3424 newmount
.mnt
= vfs_create_mount(fc
);
3425 if (IS_ERR(newmount
.mnt
)) {
3426 ret
= PTR_ERR(newmount
.mnt
);
3429 newmount
.dentry
= dget(fc
->root
);
3430 newmount
.mnt
->mnt_flags
= mnt_flags
;
3432 /* We've done the mount bit - now move the file context into more or
3433 * less the same state as if we'd done an fspick(). We don't want to
3434 * do any memory allocation or anything like that at this point as we
3435 * don't want to have to handle any errors incurred.
3437 vfs_clean_context(fc
);
3439 ns
= alloc_mnt_ns(current
->nsproxy
->mnt_ns
->user_ns
, true);
3444 mnt
= real_mount(newmount
.mnt
);
3448 list_add(&mnt
->mnt_list
, &ns
->list
);
3449 mntget(newmount
.mnt
);
3451 /* Attach to an apparent O_PATH fd with a note that we need to unmount
3452 * it, not just simply put it.
3454 file
= dentry_open(&newmount
, O_PATH
, fc
->cred
);
3456 dissolve_on_fput(newmount
.mnt
);
3457 ret
= PTR_ERR(file
);
3460 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
3462 ret
= get_unused_fd_flags((flags
& FSMOUNT_CLOEXEC
) ? O_CLOEXEC
: 0);
3464 fd_install(ret
, file
);
3469 path_put(&newmount
);
3471 mutex_unlock(&fc
->uapi_mutex
);
3478 * Move a mount from one place to another. In combination with
3479 * fsopen()/fsmount() this is used to install a new mount and in combination
3480 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
3483 * Note the flags value is a combination of MOVE_MOUNT_* flags.
3485 SYSCALL_DEFINE5(move_mount
,
3486 int, from_dfd
, const char *, from_pathname
,
3487 int, to_dfd
, const char *, to_pathname
,
3488 unsigned int, flags
)
3490 struct path from_path
, to_path
;
3491 unsigned int lflags
;
3497 if (flags
& ~MOVE_MOUNT__MASK
)
3500 /* If someone gives a pathname, they aren't permitted to move
3501 * from an fd that requires unmount as we can't get at the flag
3502 * to clear it afterwards.
3505 if (flags
& MOVE_MOUNT_F_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
3506 if (flags
& MOVE_MOUNT_F_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
3507 if (flags
& MOVE_MOUNT_F_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
3509 ret
= user_path_at(from_dfd
, from_pathname
, lflags
, &from_path
);
3514 if (flags
& MOVE_MOUNT_T_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
3515 if (flags
& MOVE_MOUNT_T_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
3516 if (flags
& MOVE_MOUNT_T_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
3518 ret
= user_path_at(to_dfd
, to_pathname
, lflags
, &to_path
);
3522 ret
= security_move_mount(&from_path
, &to_path
);
3526 ret
= do_move_mount(&from_path
, &to_path
);
3531 path_put(&from_path
);
3536 * Return true if path is reachable from root
3538 * namespace_sem or mount_lock is held
3540 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
3541 const struct path
*root
)
3543 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
3544 dentry
= mnt
->mnt_mountpoint
;
3545 mnt
= mnt
->mnt_parent
;
3547 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
3550 bool path_is_under(const struct path
*path1
, const struct path
*path2
)
3553 read_seqlock_excl(&mount_lock
);
3554 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
3555 read_sequnlock_excl(&mount_lock
);
3558 EXPORT_SYMBOL(path_is_under
);
3561 * pivot_root Semantics:
3562 * Moves the root file system of the current process to the directory put_old,
3563 * makes new_root as the new root file system of the current process, and sets
3564 * root/cwd of all processes which had them on the current root to new_root.
3567 * The new_root and put_old must be directories, and must not be on the
3568 * same file system as the current process root. The put_old must be
3569 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3570 * pointed to by put_old must yield the same directory as new_root. No other
3571 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3573 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3574 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
3575 * in this situation.
3578 * - we don't move root/cwd if they are not at the root (reason: if something
3579 * cared enough to change them, it's probably wrong to force them elsewhere)
3580 * - it's okay to pick a root that isn't the root of a file system, e.g.
3581 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3582 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3585 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
3586 const char __user
*, put_old
)
3588 struct path
new, old
, root
;
3589 struct mount
*new_mnt
, *root_mnt
, *old_mnt
, *root_parent
, *ex_parent
;
3590 struct mountpoint
*old_mp
, *root_mp
;
3596 error
= user_path_dir(new_root
, &new);
3600 error
= user_path_dir(put_old
, &old
);
3604 error
= security_sb_pivotroot(&old
, &new);
3608 get_fs_root(current
->fs
, &root
);
3609 old_mp
= lock_mount(&old
);
3610 error
= PTR_ERR(old_mp
);
3615 new_mnt
= real_mount(new.mnt
);
3616 root_mnt
= real_mount(root
.mnt
);
3617 old_mnt
= real_mount(old
.mnt
);
3618 ex_parent
= new_mnt
->mnt_parent
;
3619 root_parent
= root_mnt
->mnt_parent
;
3620 if (IS_MNT_SHARED(old_mnt
) ||
3621 IS_MNT_SHARED(ex_parent
) ||
3622 IS_MNT_SHARED(root_parent
))
3624 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
3626 if (new_mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
3629 if (d_unlinked(new.dentry
))
3632 if (new_mnt
== root_mnt
|| old_mnt
== root_mnt
)
3633 goto out4
; /* loop, on the same file system */
3635 if (root
.mnt
->mnt_root
!= root
.dentry
)
3636 goto out4
; /* not a mountpoint */
3637 if (!mnt_has_parent(root_mnt
))
3638 goto out4
; /* not attached */
3639 if (new.mnt
->mnt_root
!= new.dentry
)
3640 goto out4
; /* not a mountpoint */
3641 if (!mnt_has_parent(new_mnt
))
3642 goto out4
; /* not attached */
3643 /* make sure we can reach put_old from new_root */
3644 if (!is_path_reachable(old_mnt
, old
.dentry
, &new))
3646 /* make certain new is below the root */
3647 if (!is_path_reachable(new_mnt
, new.dentry
, &root
))
3650 umount_mnt(new_mnt
);
3651 root_mp
= unhash_mnt(root_mnt
); /* we'll need its mountpoint */
3652 if (root_mnt
->mnt
.mnt_flags
& MNT_LOCKED
) {
3653 new_mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
3654 root_mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
3656 /* mount old root on put_old */
3657 attach_mnt(root_mnt
, old_mnt
, old_mp
);
3658 /* mount new_root on / */
3659 attach_mnt(new_mnt
, root_parent
, root_mp
);
3660 mnt_add_count(root_parent
, -1);
3661 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
3662 /* A moved mount should not expire automatically */
3663 list_del_init(&new_mnt
->mnt_expire
);
3664 put_mountpoint(root_mp
);
3665 unlock_mount_hash();
3666 chroot_fs_refs(&root
, &new);
3669 unlock_mount(old_mp
);
3671 mntput_no_expire(ex_parent
);
3682 static void __init
init_mount_tree(void)
3684 struct vfsmount
*mnt
;
3686 struct mnt_namespace
*ns
;
3689 mnt
= vfs_kern_mount(&rootfs_fs_type
, 0, "rootfs", NULL
);
3691 panic("Can't create rootfs");
3693 ns
= alloc_mnt_ns(&init_user_ns
, false);
3695 panic("Can't allocate initial namespace");
3696 m
= real_mount(mnt
);
3700 list_add(&m
->mnt_list
, &ns
->list
);
3701 init_task
.nsproxy
->mnt_ns
= ns
;
3705 root
.dentry
= mnt
->mnt_root
;
3706 mnt
->mnt_flags
|= MNT_LOCKED
;
3708 set_fs_pwd(current
->fs
, &root
);
3709 set_fs_root(current
->fs
, &root
);
3712 void __init
mnt_init(void)
3716 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
3717 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
3719 mount_hashtable
= alloc_large_system_hash("Mount-cache",
3720 sizeof(struct hlist_head
),
3723 &m_hash_shift
, &m_hash_mask
, 0, 0);
3724 mountpoint_hashtable
= alloc_large_system_hash("Mountpoint-cache",
3725 sizeof(struct hlist_head
),
3728 &mp_hash_shift
, &mp_hash_mask
, 0, 0);
3730 if (!mount_hashtable
|| !mountpoint_hashtable
)
3731 panic("Failed to allocate mount hash table\n");
3737 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
3739 fs_kobj
= kobject_create_and_add("fs", NULL
);
3741 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
3747 void put_mnt_ns(struct mnt_namespace
*ns
)
3749 if (!atomic_dec_and_test(&ns
->count
))
3751 drop_collected_mounts(&ns
->root
->mnt
);
3755 struct vfsmount
*kern_mount(struct file_system_type
*type
)
3757 struct vfsmount
*mnt
;
3758 mnt
= vfs_kern_mount(type
, SB_KERNMOUNT
, type
->name
, NULL
);
3761 * it is a longterm mount, don't release mnt until
3762 * we unmount before file sys is unregistered
3764 real_mount(mnt
)->mnt_ns
= MNT_NS_INTERNAL
;
3768 EXPORT_SYMBOL_GPL(kern_mount
);
3770 void kern_unmount(struct vfsmount
*mnt
)
3772 /* release long term mount so mount point can be released */
3773 if (!IS_ERR_OR_NULL(mnt
)) {
3774 real_mount(mnt
)->mnt_ns
= NULL
;
3775 synchronize_rcu(); /* yecchhh... */
3779 EXPORT_SYMBOL(kern_unmount
);
3781 bool our_mnt(struct vfsmount
*mnt
)
3783 return check_mnt(real_mount(mnt
));
3786 bool current_chrooted(void)
3788 /* Does the current process have a non-standard root */
3789 struct path ns_root
;
3790 struct path fs_root
;
3793 /* Find the namespace root */
3794 ns_root
.mnt
= ¤t
->nsproxy
->mnt_ns
->root
->mnt
;
3795 ns_root
.dentry
= ns_root
.mnt
->mnt_root
;
3797 while (d_mountpoint(ns_root
.dentry
) && follow_down_one(&ns_root
))
3800 get_fs_root(current
->fs
, &fs_root
);
3802 chrooted
= !path_equal(&fs_root
, &ns_root
);
3810 static bool mnt_already_visible(struct mnt_namespace
*ns
,
3811 const struct super_block
*sb
,
3814 int new_flags
= *new_mnt_flags
;
3816 bool visible
= false;
3818 down_read(&namespace_sem
);
3819 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
3820 struct mount
*child
;
3823 if (mnt
->mnt
.mnt_sb
->s_type
!= sb
->s_type
)
3826 /* This mount is not fully visible if it's root directory
3827 * is not the root directory of the filesystem.
3829 if (mnt
->mnt
.mnt_root
!= mnt
->mnt
.mnt_sb
->s_root
)
3832 /* A local view of the mount flags */
3833 mnt_flags
= mnt
->mnt
.mnt_flags
;
3835 /* Don't miss readonly hidden in the superblock flags */
3836 if (sb_rdonly(mnt
->mnt
.mnt_sb
))
3837 mnt_flags
|= MNT_LOCK_READONLY
;
3839 /* Verify the mount flags are equal to or more permissive
3840 * than the proposed new mount.
3842 if ((mnt_flags
& MNT_LOCK_READONLY
) &&
3843 !(new_flags
& MNT_READONLY
))
3845 if ((mnt_flags
& MNT_LOCK_ATIME
) &&
3846 ((mnt_flags
& MNT_ATIME_MASK
) != (new_flags
& MNT_ATIME_MASK
)))
3849 /* This mount is not fully visible if there are any
3850 * locked child mounts that cover anything except for
3851 * empty directories.
3853 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
3854 struct inode
*inode
= child
->mnt_mountpoint
->d_inode
;
3855 /* Only worry about locked mounts */
3856 if (!(child
->mnt
.mnt_flags
& MNT_LOCKED
))
3858 /* Is the directory permanetly empty? */
3859 if (!is_empty_dir_inode(inode
))
3862 /* Preserve the locked attributes */
3863 *new_mnt_flags
|= mnt_flags
& (MNT_LOCK_READONLY
| \
3870 up_read(&namespace_sem
);
3874 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
)
3876 const unsigned long required_iflags
= SB_I_NOEXEC
| SB_I_NODEV
;
3877 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
3878 unsigned long s_iflags
;
3880 if (ns
->user_ns
== &init_user_ns
)
3883 /* Can this filesystem be too revealing? */
3884 s_iflags
= sb
->s_iflags
;
3885 if (!(s_iflags
& SB_I_USERNS_VISIBLE
))
3888 if ((s_iflags
& required_iflags
) != required_iflags
) {
3889 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
3894 return !mnt_already_visible(ns
, sb
, new_mnt_flags
);
3897 bool mnt_may_suid(struct vfsmount
*mnt
)
3900 * Foreign mounts (accessed via fchdir or through /proc
3901 * symlinks) are always treated as if they are nosuid. This
3902 * prevents namespaces from trusting potentially unsafe
3903 * suid/sgid bits, file caps, or security labels that originate
3904 * in other namespaces.
3906 return !(mnt
->mnt_flags
& MNT_NOSUID
) && check_mnt(real_mount(mnt
)) &&
3907 current_in_userns(mnt
->mnt_sb
->s_user_ns
);
3910 static struct ns_common
*mntns_get(struct task_struct
*task
)
3912 struct ns_common
*ns
= NULL
;
3913 struct nsproxy
*nsproxy
;
3916 nsproxy
= task
->nsproxy
;
3918 ns
= &nsproxy
->mnt_ns
->ns
;
3919 get_mnt_ns(to_mnt_ns(ns
));
3926 static void mntns_put(struct ns_common
*ns
)
3928 put_mnt_ns(to_mnt_ns(ns
));
3931 static int mntns_install(struct nsproxy
*nsproxy
, struct ns_common
*ns
)
3933 struct fs_struct
*fs
= current
->fs
;
3934 struct mnt_namespace
*mnt_ns
= to_mnt_ns(ns
), *old_mnt_ns
;
3938 if (!ns_capable(mnt_ns
->user_ns
, CAP_SYS_ADMIN
) ||
3939 !ns_capable(current_user_ns(), CAP_SYS_CHROOT
) ||
3940 !ns_capable(current_user_ns(), CAP_SYS_ADMIN
))
3943 if (is_anon_ns(mnt_ns
))
3950 old_mnt_ns
= nsproxy
->mnt_ns
;
3951 nsproxy
->mnt_ns
= mnt_ns
;
3954 err
= vfs_path_lookup(mnt_ns
->root
->mnt
.mnt_root
, &mnt_ns
->root
->mnt
,
3955 "/", LOOKUP_DOWN
, &root
);
3957 /* revert to old namespace */
3958 nsproxy
->mnt_ns
= old_mnt_ns
;
3963 put_mnt_ns(old_mnt_ns
);
3965 /* Update the pwd and root */
3966 set_fs_pwd(fs
, &root
);
3967 set_fs_root(fs
, &root
);
3973 static struct user_namespace
*mntns_owner(struct ns_common
*ns
)
3975 return to_mnt_ns(ns
)->user_ns
;
3978 const struct proc_ns_operations mntns_operations
= {
3980 .type
= CLONE_NEWNS
,
3983 .install
= mntns_install
,
3984 .owner
= mntns_owner
,