4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
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/idr.h>
19 #include <linux/init.h> /* init_rootfs */
20 #include <linux/fs_struct.h> /* get_fs_root et.al. */
21 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
22 #include <linux/uaccess.h>
23 #include <linux/proc_ns.h>
24 #include <linux/magic.h>
25 #include <linux/bootmem.h>
26 #include <linux/task_work.h>
30 /* Maximum number of mounts in a mount namespace */
31 unsigned int sysctl_mount_max __read_mostly
= 100000;
33 static unsigned int m_hash_mask __read_mostly
;
34 static unsigned int m_hash_shift __read_mostly
;
35 static unsigned int mp_hash_mask __read_mostly
;
36 static unsigned int mp_hash_shift __read_mostly
;
38 static __initdata
unsigned long mhash_entries
;
39 static int __init
set_mhash_entries(char *str
)
43 mhash_entries
= simple_strtoul(str
, &str
, 0);
46 __setup("mhash_entries=", set_mhash_entries
);
48 static __initdata
unsigned long mphash_entries
;
49 static int __init
set_mphash_entries(char *str
)
53 mphash_entries
= simple_strtoul(str
, &str
, 0);
56 __setup("mphash_entries=", set_mphash_entries
);
59 static DEFINE_IDA(mnt_id_ida
);
60 static DEFINE_IDA(mnt_group_ida
);
61 static DEFINE_SPINLOCK(mnt_id_lock
);
62 static int mnt_id_start
= 0;
63 static int mnt_group_start
= 1;
65 static struct hlist_head
*mount_hashtable __read_mostly
;
66 static struct hlist_head
*mountpoint_hashtable __read_mostly
;
67 static struct kmem_cache
*mnt_cache __read_mostly
;
68 static DECLARE_RWSEM(namespace_sem
);
71 struct kobject
*fs_kobj
;
72 EXPORT_SYMBOL_GPL(fs_kobj
);
75 * vfsmount lock may be taken for read to prevent changes to the
76 * vfsmount hash, ie. during mountpoint lookups or walking back
79 * It should be taken for write in all cases where the vfsmount
80 * tree or hash is modified or when a vfsmount structure is modified.
82 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(mount_lock
);
84 static inline struct hlist_head
*m_hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
86 unsigned long tmp
= ((unsigned long)mnt
/ L1_CACHE_BYTES
);
87 tmp
+= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
88 tmp
= tmp
+ (tmp
>> m_hash_shift
);
89 return &mount_hashtable
[tmp
& m_hash_mask
];
92 static inline struct hlist_head
*mp_hash(struct dentry
*dentry
)
94 unsigned long tmp
= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
95 tmp
= tmp
+ (tmp
>> mp_hash_shift
);
96 return &mountpoint_hashtable
[tmp
& mp_hash_mask
];
99 static int mnt_alloc_id(struct mount
*mnt
)
104 ida_pre_get(&mnt_id_ida
, GFP_KERNEL
);
105 spin_lock(&mnt_id_lock
);
106 res
= ida_get_new_above(&mnt_id_ida
, mnt_id_start
, &mnt
->mnt_id
);
108 mnt_id_start
= mnt
->mnt_id
+ 1;
109 spin_unlock(&mnt_id_lock
);
116 static void mnt_free_id(struct mount
*mnt
)
118 int id
= mnt
->mnt_id
;
119 spin_lock(&mnt_id_lock
);
120 ida_remove(&mnt_id_ida
, id
);
121 if (mnt_id_start
> id
)
123 spin_unlock(&mnt_id_lock
);
127 * Allocate a new peer group ID
129 * mnt_group_ida is protected by namespace_sem
131 static int mnt_alloc_group_id(struct mount
*mnt
)
135 if (!ida_pre_get(&mnt_group_ida
, GFP_KERNEL
))
138 res
= ida_get_new_above(&mnt_group_ida
,
142 mnt_group_start
= mnt
->mnt_group_id
+ 1;
148 * Release a peer group ID
150 void mnt_release_group_id(struct mount
*mnt
)
152 int id
= mnt
->mnt_group_id
;
153 ida_remove(&mnt_group_ida
, id
);
154 if (mnt_group_start
> id
)
155 mnt_group_start
= id
;
156 mnt
->mnt_group_id
= 0;
160 * vfsmount lock must be held for read
162 static inline void mnt_add_count(struct mount
*mnt
, int n
)
165 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, n
);
174 * vfsmount lock must be held for write
176 unsigned int mnt_get_count(struct mount
*mnt
)
179 unsigned int count
= 0;
182 for_each_possible_cpu(cpu
) {
183 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_count
;
188 return mnt
->mnt_count
;
192 static void drop_mountpoint(struct fs_pin
*p
)
194 struct mount
*m
= container_of(p
, struct mount
, mnt_umount
);
195 dput(m
->mnt_ex_mountpoint
);
200 static struct mount
*alloc_vfsmnt(const char *name
)
202 struct mount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
206 err
= mnt_alloc_id(mnt
);
211 mnt
->mnt_devname
= kstrdup_const(name
, GFP_KERNEL
);
212 if (!mnt
->mnt_devname
)
217 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
219 goto out_free_devname
;
221 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
224 mnt
->mnt_writers
= 0;
227 INIT_HLIST_NODE(&mnt
->mnt_hash
);
228 INIT_LIST_HEAD(&mnt
->mnt_child
);
229 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
230 INIT_LIST_HEAD(&mnt
->mnt_list
);
231 INIT_LIST_HEAD(&mnt
->mnt_expire
);
232 INIT_LIST_HEAD(&mnt
->mnt_share
);
233 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
234 INIT_LIST_HEAD(&mnt
->mnt_slave
);
235 INIT_HLIST_NODE(&mnt
->mnt_mp_list
);
236 #ifdef CONFIG_FSNOTIFY
237 INIT_HLIST_HEAD(&mnt
->mnt_fsnotify_marks
);
239 init_fs_pin(&mnt
->mnt_umount
, drop_mountpoint
);
245 kfree_const(mnt
->mnt_devname
);
250 kmem_cache_free(mnt_cache
, mnt
);
255 * Most r/o checks on a fs are for operations that take
256 * discrete amounts of time, like a write() or unlink().
257 * We must keep track of when those operations start
258 * (for permission checks) and when they end, so that
259 * we can determine when writes are able to occur to
263 * __mnt_is_readonly: check whether a mount is read-only
264 * @mnt: the mount to check for its write status
266 * This shouldn't be used directly ouside of the VFS.
267 * It does not guarantee that the filesystem will stay
268 * r/w, just that it is right *now*. This can not and
269 * should not be used in place of IS_RDONLY(inode).
270 * mnt_want/drop_write() will _keep_ the filesystem
273 int __mnt_is_readonly(struct vfsmount
*mnt
)
275 if (mnt
->mnt_flags
& MNT_READONLY
)
277 if (mnt
->mnt_sb
->s_flags
& MS_RDONLY
)
281 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
283 static inline void mnt_inc_writers(struct mount
*mnt
)
286 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
292 static inline void mnt_dec_writers(struct mount
*mnt
)
295 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
301 static unsigned int mnt_get_writers(struct mount
*mnt
)
304 unsigned int count
= 0;
307 for_each_possible_cpu(cpu
) {
308 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_writers
;
313 return mnt
->mnt_writers
;
317 static int mnt_is_readonly(struct vfsmount
*mnt
)
319 if (mnt
->mnt_sb
->s_readonly_remount
)
321 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
323 return __mnt_is_readonly(mnt
);
327 * Most r/o & frozen checks on a fs are for operations that take discrete
328 * amounts of time, like a write() or unlink(). We must keep track of when
329 * those operations start (for permission checks) and when they end, so that we
330 * can determine when writes are able to occur to a filesystem.
333 * __mnt_want_write - get write access to a mount without freeze protection
334 * @m: the mount on which to take a write
336 * This tells the low-level filesystem that a write is about to be performed to
337 * it, and makes sure that writes are allowed (mnt it read-write) before
338 * returning success. This operation does not protect against filesystem being
339 * frozen. When the write operation is finished, __mnt_drop_write() must be
340 * called. This is effectively a refcount.
342 int __mnt_want_write(struct vfsmount
*m
)
344 struct mount
*mnt
= real_mount(m
);
348 mnt_inc_writers(mnt
);
350 * The store to mnt_inc_writers must be visible before we pass
351 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
352 * incremented count after it has set MNT_WRITE_HOLD.
355 while (ACCESS_ONCE(mnt
->mnt
.mnt_flags
) & MNT_WRITE_HOLD
)
358 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
359 * be set to match its requirements. So we must not load that until
360 * MNT_WRITE_HOLD is cleared.
363 if (mnt_is_readonly(m
)) {
364 mnt_dec_writers(mnt
);
373 * mnt_want_write - get write access to a mount
374 * @m: the mount on which to take a write
376 * This tells the low-level filesystem that a write is about to be performed to
377 * it, and makes sure that writes are allowed (mount is read-write, filesystem
378 * is not frozen) before returning success. When the write operation is
379 * finished, mnt_drop_write() must be called. This is effectively a refcount.
381 int mnt_want_write(struct vfsmount
*m
)
385 sb_start_write(m
->mnt_sb
);
386 ret
= __mnt_want_write(m
);
388 sb_end_write(m
->mnt_sb
);
391 EXPORT_SYMBOL_GPL(mnt_want_write
);
394 * mnt_clone_write - get write access to a mount
395 * @mnt: the mount on which to take a write
397 * This is effectively like mnt_want_write, except
398 * it must only be used to take an extra write reference
399 * on a mountpoint that we already know has a write reference
400 * on it. This allows some optimisation.
402 * After finished, mnt_drop_write must be called as usual to
403 * drop the reference.
405 int mnt_clone_write(struct vfsmount
*mnt
)
407 /* superblock may be r/o */
408 if (__mnt_is_readonly(mnt
))
411 mnt_inc_writers(real_mount(mnt
));
415 EXPORT_SYMBOL_GPL(mnt_clone_write
);
418 * __mnt_want_write_file - get write access to a file's mount
419 * @file: the file who's mount on which to take a write
421 * This is like __mnt_want_write, but it takes a file and can
422 * do some optimisations if the file is open for write already
424 int __mnt_want_write_file(struct file
*file
)
426 if (!(file
->f_mode
& FMODE_WRITER
))
427 return __mnt_want_write(file
->f_path
.mnt
);
429 return mnt_clone_write(file
->f_path
.mnt
);
433 * mnt_want_write_file - get write access to a file's mount
434 * @file: the file who's mount on which to take a write
436 * This is like mnt_want_write, but it takes a file and can
437 * do some optimisations if the file is open for write already
439 int mnt_want_write_file(struct file
*file
)
443 sb_start_write(file
->f_path
.mnt
->mnt_sb
);
444 ret
= __mnt_want_write_file(file
);
446 sb_end_write(file
->f_path
.mnt
->mnt_sb
);
449 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
452 * __mnt_drop_write - give up write access to a mount
453 * @mnt: the mount on which to give up write access
455 * Tells the low-level filesystem that we are done
456 * performing writes to it. Must be matched with
457 * __mnt_want_write() call above.
459 void __mnt_drop_write(struct vfsmount
*mnt
)
462 mnt_dec_writers(real_mount(mnt
));
465 EXPORT_SYMBOL_GPL(__mnt_drop_write
);
468 * mnt_drop_write - give up write access to a mount
469 * @mnt: the mount on which to give up write access
471 * Tells the low-level filesystem that we are done performing writes to it and
472 * also allows filesystem to be frozen again. Must be matched with
473 * mnt_want_write() call above.
475 void mnt_drop_write(struct vfsmount
*mnt
)
477 __mnt_drop_write(mnt
);
478 sb_end_write(mnt
->mnt_sb
);
480 EXPORT_SYMBOL_GPL(mnt_drop_write
);
482 void __mnt_drop_write_file(struct file
*file
)
484 __mnt_drop_write(file
->f_path
.mnt
);
487 void mnt_drop_write_file(struct file
*file
)
489 mnt_drop_write(file
->f_path
.mnt
);
491 EXPORT_SYMBOL(mnt_drop_write_file
);
493 static int mnt_make_readonly(struct mount
*mnt
)
498 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
500 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
501 * should be visible before we do.
506 * With writers on hold, if this value is zero, then there are
507 * definitely no active writers (although held writers may subsequently
508 * increment the count, they'll have to wait, and decrement it after
509 * seeing MNT_READONLY).
511 * It is OK to have counter incremented on one CPU and decremented on
512 * another: the sum will add up correctly. The danger would be when we
513 * sum up each counter, if we read a counter before it is incremented,
514 * but then read another CPU's count which it has been subsequently
515 * decremented from -- we would see more decrements than we should.
516 * MNT_WRITE_HOLD protects against this scenario, because
517 * mnt_want_write first increments count, then smp_mb, then spins on
518 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
519 * we're counting up here.
521 if (mnt_get_writers(mnt
) > 0)
524 mnt
->mnt
.mnt_flags
|= MNT_READONLY
;
526 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
527 * that become unheld will see MNT_READONLY.
530 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
535 static void __mnt_unmake_readonly(struct mount
*mnt
)
538 mnt
->mnt
.mnt_flags
&= ~MNT_READONLY
;
542 int sb_prepare_remount_readonly(struct super_block
*sb
)
547 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
548 if (atomic_long_read(&sb
->s_remove_count
))
552 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
553 if (!(mnt
->mnt
.mnt_flags
& MNT_READONLY
)) {
554 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
556 if (mnt_get_writers(mnt
) > 0) {
562 if (!err
&& atomic_long_read(&sb
->s_remove_count
))
566 sb
->s_readonly_remount
= 1;
569 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
570 if (mnt
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
571 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
578 static void free_vfsmnt(struct mount
*mnt
)
580 kfree_const(mnt
->mnt_devname
);
582 free_percpu(mnt
->mnt_pcp
);
584 kmem_cache_free(mnt_cache
, mnt
);
587 static void delayed_free_vfsmnt(struct rcu_head
*head
)
589 free_vfsmnt(container_of(head
, struct mount
, mnt_rcu
));
592 /* call under rcu_read_lock */
593 int __legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
596 if (read_seqretry(&mount_lock
, seq
))
600 mnt
= real_mount(bastard
);
601 mnt_add_count(mnt
, 1);
602 if (likely(!read_seqretry(&mount_lock
, seq
)))
604 if (bastard
->mnt_flags
& MNT_SYNC_UMOUNT
) {
605 mnt_add_count(mnt
, -1);
611 /* call under rcu_read_lock */
612 bool legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
614 int res
= __legitimize_mnt(bastard
, seq
);
617 if (unlikely(res
< 0)) {
626 * find the first mount at @dentry on vfsmount @mnt.
627 * call under rcu_read_lock()
629 struct mount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
631 struct hlist_head
*head
= m_hash(mnt
, dentry
);
634 hlist_for_each_entry_rcu(p
, head
, mnt_hash
)
635 if (&p
->mnt_parent
->mnt
== mnt
&& p
->mnt_mountpoint
== dentry
)
641 * find the last mount at @dentry on vfsmount @mnt.
642 * mount_lock must be held.
644 struct mount
*__lookup_mnt_last(struct vfsmount
*mnt
, struct dentry
*dentry
)
646 struct mount
*p
, *res
= NULL
;
647 p
= __lookup_mnt(mnt
, dentry
);
650 if (!(p
->mnt
.mnt_flags
& MNT_UMOUNT
))
652 hlist_for_each_entry_continue(p
, mnt_hash
) {
653 if (&p
->mnt_parent
->mnt
!= mnt
|| p
->mnt_mountpoint
!= dentry
)
655 if (!(p
->mnt
.mnt_flags
& MNT_UMOUNT
))
663 * lookup_mnt - Return the first child mount mounted at path
665 * "First" means first mounted chronologically. If you create the
668 * mount /dev/sda1 /mnt
669 * mount /dev/sda2 /mnt
670 * mount /dev/sda3 /mnt
672 * Then lookup_mnt() on the base /mnt dentry in the root mount will
673 * return successively the root dentry and vfsmount of /dev/sda1, then
674 * /dev/sda2, then /dev/sda3, then NULL.
676 * lookup_mnt takes a reference to the found vfsmount.
678 struct vfsmount
*lookup_mnt(const struct path
*path
)
680 struct mount
*child_mnt
;
686 seq
= read_seqbegin(&mount_lock
);
687 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
);
688 m
= child_mnt
? &child_mnt
->mnt
: NULL
;
689 } while (!legitimize_mnt(m
, seq
));
695 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
696 * current mount namespace.
698 * The common case is dentries are not mountpoints at all and that
699 * test is handled inline. For the slow case when we are actually
700 * dealing with a mountpoint of some kind, walk through all of the
701 * mounts in the current mount namespace and test to see if the dentry
704 * The mount_hashtable is not usable in the context because we
705 * need to identify all mounts that may be in the current mount
706 * namespace not just a mount that happens to have some specified
709 bool __is_local_mountpoint(struct dentry
*dentry
)
711 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
713 bool is_covered
= false;
715 if (!d_mountpoint(dentry
))
718 down_read(&namespace_sem
);
719 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
720 is_covered
= (mnt
->mnt_mountpoint
== dentry
);
724 up_read(&namespace_sem
);
729 static struct mountpoint
*lookup_mountpoint(struct dentry
*dentry
)
731 struct hlist_head
*chain
= mp_hash(dentry
);
732 struct mountpoint
*mp
;
734 hlist_for_each_entry(mp
, chain
, m_hash
) {
735 if (mp
->m_dentry
== dentry
) {
736 /* might be worth a WARN_ON() */
737 if (d_unlinked(dentry
))
738 return ERR_PTR(-ENOENT
);
746 static struct mountpoint
*get_mountpoint(struct dentry
*dentry
)
748 struct mountpoint
*mp
, *new = NULL
;
751 if (d_mountpoint(dentry
)) {
753 read_seqlock_excl(&mount_lock
);
754 mp
= lookup_mountpoint(dentry
);
755 read_sequnlock_excl(&mount_lock
);
761 new = kmalloc(sizeof(struct mountpoint
), GFP_KERNEL
);
763 return ERR_PTR(-ENOMEM
);
766 /* Exactly one processes may set d_mounted */
767 ret
= d_set_mounted(dentry
);
769 /* Someone else set d_mounted? */
773 /* The dentry is not available as a mountpoint? */
778 /* Add the new mountpoint to the hash table */
779 read_seqlock_excl(&mount_lock
);
780 new->m_dentry
= dentry
;
782 hlist_add_head(&new->m_hash
, mp_hash(dentry
));
783 INIT_HLIST_HEAD(&new->m_list
);
784 read_sequnlock_excl(&mount_lock
);
793 static void put_mountpoint(struct mountpoint
*mp
)
795 if (!--mp
->m_count
) {
796 struct dentry
*dentry
= mp
->m_dentry
;
797 BUG_ON(!hlist_empty(&mp
->m_list
));
798 spin_lock(&dentry
->d_lock
);
799 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
800 spin_unlock(&dentry
->d_lock
);
801 hlist_del(&mp
->m_hash
);
806 static inline int check_mnt(struct mount
*mnt
)
808 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
812 * vfsmount lock must be held for write
814 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
818 wake_up_interruptible(&ns
->poll
);
823 * vfsmount lock must be held for write
825 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
827 if (ns
&& ns
->event
!= event
) {
829 wake_up_interruptible(&ns
->poll
);
834 * vfsmount lock must be held for write
836 static void unhash_mnt(struct mount
*mnt
)
838 mnt
->mnt_parent
= mnt
;
839 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
840 list_del_init(&mnt
->mnt_child
);
841 hlist_del_init_rcu(&mnt
->mnt_hash
);
842 hlist_del_init(&mnt
->mnt_mp_list
);
843 put_mountpoint(mnt
->mnt_mp
);
848 * vfsmount lock must be held for write
850 static void detach_mnt(struct mount
*mnt
, struct path
*old_path
)
852 old_path
->dentry
= mnt
->mnt_mountpoint
;
853 old_path
->mnt
= &mnt
->mnt_parent
->mnt
;
858 * vfsmount lock must be held for write
860 static void umount_mnt(struct mount
*mnt
)
862 /* old mountpoint will be dropped when we can do that */
863 mnt
->mnt_ex_mountpoint
= mnt
->mnt_mountpoint
;
868 * vfsmount lock must be held for write
870 void mnt_set_mountpoint(struct mount
*mnt
,
871 struct mountpoint
*mp
,
872 struct mount
*child_mnt
)
875 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
876 child_mnt
->mnt_mountpoint
= dget(mp
->m_dentry
);
877 child_mnt
->mnt_parent
= mnt
;
878 child_mnt
->mnt_mp
= mp
;
879 hlist_add_head(&child_mnt
->mnt_mp_list
, &mp
->m_list
);
883 * vfsmount lock must be held for write
885 static void attach_mnt(struct mount
*mnt
,
886 struct mount
*parent
,
887 struct mountpoint
*mp
)
889 mnt_set_mountpoint(parent
, mp
, mnt
);
890 hlist_add_head_rcu(&mnt
->mnt_hash
, m_hash(&parent
->mnt
, mp
->m_dentry
));
891 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
894 static void attach_shadowed(struct mount
*mnt
,
895 struct mount
*parent
,
896 struct mount
*shadows
)
899 hlist_add_behind_rcu(&mnt
->mnt_hash
, &shadows
->mnt_hash
);
900 list_add(&mnt
->mnt_child
, &shadows
->mnt_child
);
902 hlist_add_head_rcu(&mnt
->mnt_hash
,
903 m_hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
904 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
909 * vfsmount lock must be held for write
911 static void commit_tree(struct mount
*mnt
, struct mount
*shadows
)
913 struct mount
*parent
= mnt
->mnt_parent
;
916 struct mnt_namespace
*n
= parent
->mnt_ns
;
918 BUG_ON(parent
== mnt
);
920 list_add_tail(&head
, &mnt
->mnt_list
);
921 list_for_each_entry(m
, &head
, mnt_list
)
924 list_splice(&head
, n
->list
.prev
);
926 n
->mounts
+= n
->pending_mounts
;
927 n
->pending_mounts
= 0;
929 attach_shadowed(mnt
, parent
, shadows
);
930 touch_mnt_namespace(n
);
933 static struct mount
*next_mnt(struct mount
*p
, struct mount
*root
)
935 struct list_head
*next
= p
->mnt_mounts
.next
;
936 if (next
== &p
->mnt_mounts
) {
940 next
= p
->mnt_child
.next
;
941 if (next
!= &p
->mnt_parent
->mnt_mounts
)
946 return list_entry(next
, struct mount
, mnt_child
);
949 static struct mount
*skip_mnt_tree(struct mount
*p
)
951 struct list_head
*prev
= p
->mnt_mounts
.prev
;
952 while (prev
!= &p
->mnt_mounts
) {
953 p
= list_entry(prev
, struct mount
, mnt_child
);
954 prev
= p
->mnt_mounts
.prev
;
960 vfs_kern_mount(struct file_system_type
*type
, int flags
, const char *name
, void *data
)
966 return ERR_PTR(-ENODEV
);
968 mnt
= alloc_vfsmnt(name
);
970 return ERR_PTR(-ENOMEM
);
972 if (flags
& MS_KERNMOUNT
)
973 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
975 root
= mount_fs(type
, flags
, name
, data
);
979 return ERR_CAST(root
);
982 mnt
->mnt
.mnt_root
= root
;
983 mnt
->mnt
.mnt_sb
= root
->d_sb
;
984 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
985 mnt
->mnt_parent
= mnt
;
987 list_add_tail(&mnt
->mnt_instance
, &root
->d_sb
->s_mounts
);
991 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
994 vfs_submount(const struct dentry
*mountpoint
, struct file_system_type
*type
,
995 const char *name
, void *data
)
997 /* Until it is worked out how to pass the user namespace
998 * through from the parent mount to the submount don't support
999 * unprivileged mounts with submounts.
1001 if (mountpoint
->d_sb
->s_user_ns
!= &init_user_ns
)
1002 return ERR_PTR(-EPERM
);
1004 return vfs_kern_mount(type
, MS_SUBMOUNT
, name
, data
);
1006 EXPORT_SYMBOL_GPL(vfs_submount
);
1008 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
1011 struct super_block
*sb
= old
->mnt
.mnt_sb
;
1015 mnt
= alloc_vfsmnt(old
->mnt_devname
);
1017 return ERR_PTR(-ENOMEM
);
1019 if (flag
& (CL_SLAVE
| CL_PRIVATE
| CL_SHARED_TO_SLAVE
))
1020 mnt
->mnt_group_id
= 0; /* not a peer of original */
1022 mnt
->mnt_group_id
= old
->mnt_group_id
;
1024 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
1025 err
= mnt_alloc_group_id(mnt
);
1030 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
& ~(MNT_WRITE_HOLD
|MNT_MARKED
);
1031 /* Don't allow unprivileged users to change mount flags */
1032 if (flag
& CL_UNPRIVILEGED
) {
1033 mnt
->mnt
.mnt_flags
|= MNT_LOCK_ATIME
;
1035 if (mnt
->mnt
.mnt_flags
& MNT_READONLY
)
1036 mnt
->mnt
.mnt_flags
|= MNT_LOCK_READONLY
;
1038 if (mnt
->mnt
.mnt_flags
& MNT_NODEV
)
1039 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NODEV
;
1041 if (mnt
->mnt
.mnt_flags
& MNT_NOSUID
)
1042 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NOSUID
;
1044 if (mnt
->mnt
.mnt_flags
& MNT_NOEXEC
)
1045 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NOEXEC
;
1048 /* Don't allow unprivileged users to reveal what is under a mount */
1049 if ((flag
& CL_UNPRIVILEGED
) &&
1050 (!(flag
& CL_EXPIRE
) || list_empty(&old
->mnt_expire
)))
1051 mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
1053 atomic_inc(&sb
->s_active
);
1054 mnt
->mnt
.mnt_sb
= sb
;
1055 mnt
->mnt
.mnt_root
= dget(root
);
1056 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1057 mnt
->mnt_parent
= mnt
;
1059 list_add_tail(&mnt
->mnt_instance
, &sb
->s_mounts
);
1060 unlock_mount_hash();
1062 if ((flag
& CL_SLAVE
) ||
1063 ((flag
& CL_SHARED_TO_SLAVE
) && IS_MNT_SHARED(old
))) {
1064 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
1065 mnt
->mnt_master
= old
;
1066 CLEAR_MNT_SHARED(mnt
);
1067 } else if (!(flag
& CL_PRIVATE
)) {
1068 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
1069 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
1070 if (IS_MNT_SLAVE(old
))
1071 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
1072 mnt
->mnt_master
= old
->mnt_master
;
1074 CLEAR_MNT_SHARED(mnt
);
1076 if (flag
& CL_MAKE_SHARED
)
1077 set_mnt_shared(mnt
);
1079 /* stick the duplicate mount on the same expiry list
1080 * as the original if that was on one */
1081 if (flag
& CL_EXPIRE
) {
1082 if (!list_empty(&old
->mnt_expire
))
1083 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
1091 return ERR_PTR(err
);
1094 static void cleanup_mnt(struct mount
*mnt
)
1097 * This probably indicates that somebody messed
1098 * up a mnt_want/drop_write() pair. If this
1099 * happens, the filesystem was probably unable
1100 * to make r/w->r/o transitions.
1103 * The locking used to deal with mnt_count decrement provides barriers,
1104 * so mnt_get_writers() below is safe.
1106 WARN_ON(mnt_get_writers(mnt
));
1107 if (unlikely(mnt
->mnt_pins
.first
))
1109 fsnotify_vfsmount_delete(&mnt
->mnt
);
1110 dput(mnt
->mnt
.mnt_root
);
1111 deactivate_super(mnt
->mnt
.mnt_sb
);
1113 call_rcu(&mnt
->mnt_rcu
, delayed_free_vfsmnt
);
1116 static void __cleanup_mnt(struct rcu_head
*head
)
1118 cleanup_mnt(container_of(head
, struct mount
, mnt_rcu
));
1121 static LLIST_HEAD(delayed_mntput_list
);
1122 static void delayed_mntput(struct work_struct
*unused
)
1124 struct llist_node
*node
= llist_del_all(&delayed_mntput_list
);
1125 struct llist_node
*next
;
1127 for (; node
; node
= next
) {
1128 next
= llist_next(node
);
1129 cleanup_mnt(llist_entry(node
, struct mount
, mnt_llist
));
1132 static DECLARE_DELAYED_WORK(delayed_mntput_work
, delayed_mntput
);
1134 static void mntput_no_expire(struct mount
*mnt
)
1137 mnt_add_count(mnt
, -1);
1138 if (likely(mnt
->mnt_ns
)) { /* shouldn't be the last one */
1143 if (mnt_get_count(mnt
)) {
1145 unlock_mount_hash();
1148 if (unlikely(mnt
->mnt
.mnt_flags
& MNT_DOOMED
)) {
1150 unlock_mount_hash();
1153 mnt
->mnt
.mnt_flags
|= MNT_DOOMED
;
1156 list_del(&mnt
->mnt_instance
);
1158 if (unlikely(!list_empty(&mnt
->mnt_mounts
))) {
1159 struct mount
*p
, *tmp
;
1160 list_for_each_entry_safe(p
, tmp
, &mnt
->mnt_mounts
, mnt_child
) {
1164 unlock_mount_hash();
1166 if (likely(!(mnt
->mnt
.mnt_flags
& MNT_INTERNAL
))) {
1167 struct task_struct
*task
= current
;
1168 if (likely(!(task
->flags
& PF_KTHREAD
))) {
1169 init_task_work(&mnt
->mnt_rcu
, __cleanup_mnt
);
1170 if (!task_work_add(task
, &mnt
->mnt_rcu
, true))
1173 if (llist_add(&mnt
->mnt_llist
, &delayed_mntput_list
))
1174 schedule_delayed_work(&delayed_mntput_work
, 1);
1180 void mntput(struct vfsmount
*mnt
)
1183 struct mount
*m
= real_mount(mnt
);
1184 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1185 if (unlikely(m
->mnt_expiry_mark
))
1186 m
->mnt_expiry_mark
= 0;
1187 mntput_no_expire(m
);
1190 EXPORT_SYMBOL(mntput
);
1192 struct vfsmount
*mntget(struct vfsmount
*mnt
)
1195 mnt_add_count(real_mount(mnt
), 1);
1198 EXPORT_SYMBOL(mntget
);
1200 /* path_is_mountpoint() - Check if path is a mount in the current
1203 * d_mountpoint() can only be used reliably to establish if a dentry is
1204 * not mounted in any namespace and that common case is handled inline.
1205 * d_mountpoint() isn't aware of the possibility there may be multiple
1206 * mounts using a given dentry in a different namespace. This function
1207 * checks if the passed in path is a mountpoint rather than the dentry
1210 bool path_is_mountpoint(const struct path
*path
)
1215 if (!d_mountpoint(path
->dentry
))
1220 seq
= read_seqbegin(&mount_lock
);
1221 res
= __path_is_mountpoint(path
);
1222 } while (read_seqretry(&mount_lock
, seq
));
1227 EXPORT_SYMBOL(path_is_mountpoint
);
1229 struct vfsmount
*mnt_clone_internal(const struct path
*path
)
1232 p
= clone_mnt(real_mount(path
->mnt
), path
->dentry
, CL_PRIVATE
);
1235 p
->mnt
.mnt_flags
|= MNT_INTERNAL
;
1239 static inline void mangle(struct seq_file
*m
, const char *s
)
1241 seq_escape(m
, s
, " \t\n\\");
1245 * Simple .show_options callback for filesystems which don't want to
1246 * implement more complex mount option showing.
1248 * See also save_mount_options().
1250 int generic_show_options(struct seq_file
*m
, struct dentry
*root
)
1252 const char *options
;
1255 options
= rcu_dereference(root
->d_sb
->s_options
);
1257 if (options
!= NULL
&& options
[0]) {
1265 EXPORT_SYMBOL(generic_show_options
);
1268 * If filesystem uses generic_show_options(), this function should be
1269 * called from the fill_super() callback.
1271 * The .remount_fs callback usually needs to be handled in a special
1272 * way, to make sure, that previous options are not overwritten if the
1275 * Also note, that if the filesystem's .remount_fs function doesn't
1276 * reset all options to their default value, but changes only newly
1277 * given options, then the displayed options will not reflect reality
1280 void save_mount_options(struct super_block
*sb
, char *options
)
1282 BUG_ON(sb
->s_options
);
1283 rcu_assign_pointer(sb
->s_options
, kstrdup(options
, GFP_KERNEL
));
1285 EXPORT_SYMBOL(save_mount_options
);
1287 void replace_mount_options(struct super_block
*sb
, char *options
)
1289 char *old
= sb
->s_options
;
1290 rcu_assign_pointer(sb
->s_options
, options
);
1296 EXPORT_SYMBOL(replace_mount_options
);
1298 #ifdef CONFIG_PROC_FS
1299 /* iterator; we want it to have access to namespace_sem, thus here... */
1300 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
1302 struct proc_mounts
*p
= m
->private;
1304 down_read(&namespace_sem
);
1305 if (p
->cached_event
== p
->ns
->event
) {
1306 void *v
= p
->cached_mount
;
1307 if (*pos
== p
->cached_index
)
1309 if (*pos
== p
->cached_index
+ 1) {
1310 v
= seq_list_next(v
, &p
->ns
->list
, &p
->cached_index
);
1311 return p
->cached_mount
= v
;
1315 p
->cached_event
= p
->ns
->event
;
1316 p
->cached_mount
= seq_list_start(&p
->ns
->list
, *pos
);
1317 p
->cached_index
= *pos
;
1318 return p
->cached_mount
;
1321 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
1323 struct proc_mounts
*p
= m
->private;
1325 p
->cached_mount
= seq_list_next(v
, &p
->ns
->list
, pos
);
1326 p
->cached_index
= *pos
;
1327 return p
->cached_mount
;
1330 static void m_stop(struct seq_file
*m
, void *v
)
1332 up_read(&namespace_sem
);
1335 static int m_show(struct seq_file
*m
, void *v
)
1337 struct proc_mounts
*p
= m
->private;
1338 struct mount
*r
= list_entry(v
, struct mount
, mnt_list
);
1339 return p
->show(m
, &r
->mnt
);
1342 const struct seq_operations mounts_op
= {
1348 #endif /* CONFIG_PROC_FS */
1351 * may_umount_tree - check if a mount tree is busy
1352 * @mnt: root of mount tree
1354 * This is called to check if a tree of mounts has any
1355 * open files, pwds, chroots or sub mounts that are
1358 int may_umount_tree(struct vfsmount
*m
)
1360 struct mount
*mnt
= real_mount(m
);
1361 int actual_refs
= 0;
1362 int minimum_refs
= 0;
1366 /* write lock needed for mnt_get_count */
1368 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1369 actual_refs
+= mnt_get_count(p
);
1372 unlock_mount_hash();
1374 if (actual_refs
> minimum_refs
)
1380 EXPORT_SYMBOL(may_umount_tree
);
1383 * may_umount - check if a mount point is busy
1384 * @mnt: root of mount
1386 * This is called to check if a mount point has any
1387 * open files, pwds, chroots or sub mounts. If the
1388 * mount has sub mounts this will return busy
1389 * regardless of whether the sub mounts are busy.
1391 * Doesn't take quota and stuff into account. IOW, in some cases it will
1392 * give false negatives. The main reason why it's here is that we need
1393 * a non-destructive way to look for easily umountable filesystems.
1395 int may_umount(struct vfsmount
*mnt
)
1398 down_read(&namespace_sem
);
1400 if (propagate_mount_busy(real_mount(mnt
), 2))
1402 unlock_mount_hash();
1403 up_read(&namespace_sem
);
1407 EXPORT_SYMBOL(may_umount
);
1409 static HLIST_HEAD(unmounted
); /* protected by namespace_sem */
1411 static void namespace_unlock(void)
1413 struct hlist_head head
;
1415 hlist_move_list(&unmounted
, &head
);
1417 up_write(&namespace_sem
);
1419 if (likely(hlist_empty(&head
)))
1424 group_pin_kill(&head
);
1427 static inline void namespace_lock(void)
1429 down_write(&namespace_sem
);
1432 enum umount_tree_flags
{
1434 UMOUNT_PROPAGATE
= 2,
1435 UMOUNT_CONNECTED
= 4,
1438 static bool disconnect_mount(struct mount
*mnt
, enum umount_tree_flags how
)
1440 /* Leaving mounts connected is only valid for lazy umounts */
1441 if (how
& UMOUNT_SYNC
)
1444 /* A mount without a parent has nothing to be connected to */
1445 if (!mnt_has_parent(mnt
))
1448 /* Because the reference counting rules change when mounts are
1449 * unmounted and connected, umounted mounts may not be
1450 * connected to mounted mounts.
1452 if (!(mnt
->mnt_parent
->mnt
.mnt_flags
& MNT_UMOUNT
))
1455 /* Has it been requested that the mount remain connected? */
1456 if (how
& UMOUNT_CONNECTED
)
1459 /* Is the mount locked such that it needs to remain connected? */
1460 if (IS_MNT_LOCKED(mnt
))
1463 /* By default disconnect the mount */
1468 * mount_lock must be held
1469 * namespace_sem must be held for write
1471 static void umount_tree(struct mount
*mnt
, enum umount_tree_flags how
)
1473 LIST_HEAD(tmp_list
);
1476 if (how
& UMOUNT_PROPAGATE
)
1477 propagate_mount_unlock(mnt
);
1479 /* Gather the mounts to umount */
1480 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1481 p
->mnt
.mnt_flags
|= MNT_UMOUNT
;
1482 list_move(&p
->mnt_list
, &tmp_list
);
1485 /* Hide the mounts from mnt_mounts */
1486 list_for_each_entry(p
, &tmp_list
, mnt_list
) {
1487 list_del_init(&p
->mnt_child
);
1490 /* Add propogated mounts to the tmp_list */
1491 if (how
& UMOUNT_PROPAGATE
)
1492 propagate_umount(&tmp_list
);
1494 while (!list_empty(&tmp_list
)) {
1495 struct mnt_namespace
*ns
;
1497 p
= list_first_entry(&tmp_list
, struct mount
, mnt_list
);
1498 list_del_init(&p
->mnt_expire
);
1499 list_del_init(&p
->mnt_list
);
1503 __touch_mnt_namespace(ns
);
1506 if (how
& UMOUNT_SYNC
)
1507 p
->mnt
.mnt_flags
|= MNT_SYNC_UMOUNT
;
1509 disconnect
= disconnect_mount(p
, how
);
1511 pin_insert_group(&p
->mnt_umount
, &p
->mnt_parent
->mnt
,
1512 disconnect
? &unmounted
: NULL
);
1513 if (mnt_has_parent(p
)) {
1514 mnt_add_count(p
->mnt_parent
, -1);
1516 /* Don't forget about p */
1517 list_add_tail(&p
->mnt_child
, &p
->mnt_parent
->mnt_mounts
);
1522 change_mnt_propagation(p
, MS_PRIVATE
);
1526 static void shrink_submounts(struct mount
*mnt
);
1528 static int do_umount(struct mount
*mnt
, int flags
)
1530 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1533 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1538 * Allow userspace to request a mountpoint be expired rather than
1539 * unmounting unconditionally. Unmount only happens if:
1540 * (1) the mark is already set (the mark is cleared by mntput())
1541 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1543 if (flags
& MNT_EXPIRE
) {
1544 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1545 flags
& (MNT_FORCE
| MNT_DETACH
))
1549 * probably don't strictly need the lock here if we examined
1550 * all race cases, but it's a slowpath.
1553 if (mnt_get_count(mnt
) != 2) {
1554 unlock_mount_hash();
1557 unlock_mount_hash();
1559 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1564 * If we may have to abort operations to get out of this
1565 * mount, and they will themselves hold resources we must
1566 * allow the fs to do things. In the Unix tradition of
1567 * 'Gee thats tricky lets do it in userspace' the umount_begin
1568 * might fail to complete on the first run through as other tasks
1569 * must return, and the like. Thats for the mount program to worry
1570 * about for the moment.
1573 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1574 sb
->s_op
->umount_begin(sb
);
1578 * No sense to grab the lock for this test, but test itself looks
1579 * somewhat bogus. Suggestions for better replacement?
1580 * Ho-hum... In principle, we might treat that as umount + switch
1581 * to rootfs. GC would eventually take care of the old vfsmount.
1582 * Actually it makes sense, especially if rootfs would contain a
1583 * /reboot - static binary that would close all descriptors and
1584 * call reboot(9). Then init(8) could umount root and exec /reboot.
1586 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1588 * Special case for "unmounting" root ...
1589 * we just try to remount it readonly.
1591 if (!ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
))
1593 down_write(&sb
->s_umount
);
1594 if (!(sb
->s_flags
& MS_RDONLY
))
1595 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
1596 up_write(&sb
->s_umount
);
1604 if (flags
& MNT_DETACH
) {
1605 if (!list_empty(&mnt
->mnt_list
))
1606 umount_tree(mnt
, UMOUNT_PROPAGATE
);
1609 shrink_submounts(mnt
);
1611 if (!propagate_mount_busy(mnt
, 2)) {
1612 if (!list_empty(&mnt
->mnt_list
))
1613 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
1617 unlock_mount_hash();
1623 * __detach_mounts - lazily unmount all mounts on the specified dentry
1625 * During unlink, rmdir, and d_drop it is possible to loose the path
1626 * to an existing mountpoint, and wind up leaking the mount.
1627 * detach_mounts allows lazily unmounting those mounts instead of
1630 * The caller may hold dentry->d_inode->i_mutex.
1632 void __detach_mounts(struct dentry
*dentry
)
1634 struct mountpoint
*mp
;
1639 mp
= lookup_mountpoint(dentry
);
1640 if (IS_ERR_OR_NULL(mp
))
1644 while (!hlist_empty(&mp
->m_list
)) {
1645 mnt
= hlist_entry(mp
->m_list
.first
, struct mount
, mnt_mp_list
);
1646 if (mnt
->mnt
.mnt_flags
& MNT_UMOUNT
) {
1647 hlist_add_head(&mnt
->mnt_umount
.s_list
, &unmounted
);
1650 else umount_tree(mnt
, UMOUNT_CONNECTED
);
1654 unlock_mount_hash();
1659 * Is the caller allowed to modify his namespace?
1661 static inline bool may_mount(void)
1663 return ns_capable(current
->nsproxy
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
);
1666 static inline bool may_mandlock(void)
1668 #ifndef CONFIG_MANDATORY_FILE_LOCKING
1671 return capable(CAP_SYS_ADMIN
);
1675 * Now umount can handle mount points as well as block devices.
1676 * This is important for filesystems which use unnamed block devices.
1678 * We now support a flag for forced unmount like the other 'big iron'
1679 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1682 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1687 int lookup_flags
= 0;
1689 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1695 if (!(flags
& UMOUNT_NOFOLLOW
))
1696 lookup_flags
|= LOOKUP_FOLLOW
;
1698 retval
= user_path_mountpoint_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1701 mnt
= real_mount(path
.mnt
);
1703 if (path
.dentry
!= path
.mnt
->mnt_root
)
1705 if (!check_mnt(mnt
))
1707 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
1710 if (flags
& MNT_FORCE
&& !capable(CAP_SYS_ADMIN
))
1713 retval
= do_umount(mnt
, flags
);
1715 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1717 mntput_no_expire(mnt
);
1722 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1725 * The 2.0 compatible umount. No flags.
1727 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1729 return sys_umount(name
, 0);
1734 static bool is_mnt_ns_file(struct dentry
*dentry
)
1736 /* Is this a proxy for a mount namespace? */
1737 return dentry
->d_op
== &ns_dentry_operations
&&
1738 dentry
->d_fsdata
== &mntns_operations
;
1741 struct mnt_namespace
*to_mnt_ns(struct ns_common
*ns
)
1743 return container_of(ns
, struct mnt_namespace
, ns
);
1746 static bool mnt_ns_loop(struct dentry
*dentry
)
1748 /* Could bind mounting the mount namespace inode cause a
1749 * mount namespace loop?
1751 struct mnt_namespace
*mnt_ns
;
1752 if (!is_mnt_ns_file(dentry
))
1755 mnt_ns
= to_mnt_ns(get_proc_ns(dentry
->d_inode
));
1756 return current
->nsproxy
->mnt_ns
->seq
>= mnt_ns
->seq
;
1759 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1762 struct mount
*res
, *p
, *q
, *r
, *parent
;
1764 if (!(flag
& CL_COPY_UNBINDABLE
) && IS_MNT_UNBINDABLE(mnt
))
1765 return ERR_PTR(-EINVAL
);
1767 if (!(flag
& CL_COPY_MNT_NS_FILE
) && is_mnt_ns_file(dentry
))
1768 return ERR_PTR(-EINVAL
);
1770 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1774 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1777 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1779 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1782 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1783 struct mount
*t
= NULL
;
1784 if (!(flag
& CL_COPY_UNBINDABLE
) &&
1785 IS_MNT_UNBINDABLE(s
)) {
1786 s
= skip_mnt_tree(s
);
1789 if (!(flag
& CL_COPY_MNT_NS_FILE
) &&
1790 is_mnt_ns_file(s
->mnt
.mnt_root
)) {
1791 s
= skip_mnt_tree(s
);
1794 while (p
!= s
->mnt_parent
) {
1800 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
1804 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1805 mnt_set_mountpoint(parent
, p
->mnt_mp
, q
);
1806 if (!list_empty(&parent
->mnt_mounts
)) {
1807 t
= list_last_entry(&parent
->mnt_mounts
,
1808 struct mount
, mnt_child
);
1809 if (t
->mnt_mp
!= p
->mnt_mp
)
1812 attach_shadowed(q
, parent
, t
);
1813 unlock_mount_hash();
1820 umount_tree(res
, UMOUNT_SYNC
);
1821 unlock_mount_hash();
1826 /* Caller should check returned pointer for errors */
1828 struct vfsmount
*collect_mounts(const struct path
*path
)
1832 if (!check_mnt(real_mount(path
->mnt
)))
1833 tree
= ERR_PTR(-EINVAL
);
1835 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
1836 CL_COPY_ALL
| CL_PRIVATE
);
1839 return ERR_CAST(tree
);
1843 void drop_collected_mounts(struct vfsmount
*mnt
)
1847 umount_tree(real_mount(mnt
), UMOUNT_SYNC
);
1848 unlock_mount_hash();
1853 * clone_private_mount - create a private clone of a path
1855 * This creates a new vfsmount, which will be the clone of @path. The new will
1856 * not be attached anywhere in the namespace and will be private (i.e. changes
1857 * to the originating mount won't be propagated into this).
1859 * Release with mntput().
1861 struct vfsmount
*clone_private_mount(const struct path
*path
)
1863 struct mount
*old_mnt
= real_mount(path
->mnt
);
1864 struct mount
*new_mnt
;
1866 if (IS_MNT_UNBINDABLE(old_mnt
))
1867 return ERR_PTR(-EINVAL
);
1869 new_mnt
= clone_mnt(old_mnt
, path
->dentry
, CL_PRIVATE
);
1870 if (IS_ERR(new_mnt
))
1871 return ERR_CAST(new_mnt
);
1873 return &new_mnt
->mnt
;
1875 EXPORT_SYMBOL_GPL(clone_private_mount
);
1877 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1878 struct vfsmount
*root
)
1881 int res
= f(root
, arg
);
1884 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
1885 res
= f(&mnt
->mnt
, arg
);
1891 EXPORT_SYMBOL_GPL(iterate_mounts
);
1893 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
1897 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
1898 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
1899 mnt_release_group_id(p
);
1903 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
1907 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
1908 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
1909 int err
= mnt_alloc_group_id(p
);
1911 cleanup_group_ids(mnt
, p
);
1920 int count_mounts(struct mnt_namespace
*ns
, struct mount
*mnt
)
1922 unsigned int max
= READ_ONCE(sysctl_mount_max
);
1923 unsigned int mounts
= 0, old
, pending
, sum
;
1926 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
1930 pending
= ns
->pending_mounts
;
1931 sum
= old
+ pending
;
1935 (mounts
> (max
- sum
)))
1938 ns
->pending_mounts
= pending
+ mounts
;
1943 * @source_mnt : mount tree to be attached
1944 * @nd : place the mount tree @source_mnt is attached
1945 * @parent_nd : if non-null, detach the source_mnt from its parent and
1946 * store the parent mount and mountpoint dentry.
1947 * (done when source_mnt is moved)
1949 * NOTE: in the table below explains the semantics when a source mount
1950 * of a given type is attached to a destination mount of a given type.
1951 * ---------------------------------------------------------------------------
1952 * | BIND MOUNT OPERATION |
1953 * |**************************************************************************
1954 * | source-->| shared | private | slave | unbindable |
1958 * |**************************************************************************
1959 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1961 * |non-shared| shared (+) | private | slave (*) | invalid |
1962 * ***************************************************************************
1963 * A bind operation clones the source mount and mounts the clone on the
1964 * destination mount.
1966 * (++) the cloned mount is propagated to all the mounts in the propagation
1967 * tree of the destination mount and the cloned mount is added to
1968 * the peer group of the source mount.
1969 * (+) the cloned mount is created under the destination mount and is marked
1970 * as shared. The cloned mount is added to the peer group of the source
1972 * (+++) the mount is propagated to all the mounts in the propagation tree
1973 * of the destination mount and the cloned mount is made slave
1974 * of the same master as that of the source mount. The cloned mount
1975 * is marked as 'shared and slave'.
1976 * (*) the cloned mount is made a slave of the same master as that of the
1979 * ---------------------------------------------------------------------------
1980 * | MOVE MOUNT OPERATION |
1981 * |**************************************************************************
1982 * | source-->| shared | private | slave | unbindable |
1986 * |**************************************************************************
1987 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1989 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1990 * ***************************************************************************
1992 * (+) the mount is moved to the destination. And is then propagated to
1993 * all the mounts in the propagation tree of the destination mount.
1994 * (+*) the mount is moved to the destination.
1995 * (+++) the mount is moved to the destination and is then propagated to
1996 * all the mounts belonging to the destination mount's propagation tree.
1997 * the mount is marked as 'shared and slave'.
1998 * (*) the mount continues to be a slave at the new location.
2000 * if the source mount is a tree, the operations explained above is
2001 * applied to each mount in the tree.
2002 * Must be called without spinlocks held, since this function can sleep
2005 static int attach_recursive_mnt(struct mount
*source_mnt
,
2006 struct mount
*dest_mnt
,
2007 struct mountpoint
*dest_mp
,
2008 struct path
*parent_path
)
2010 HLIST_HEAD(tree_list
);
2011 struct mnt_namespace
*ns
= dest_mnt
->mnt_ns
;
2012 struct mount
*child
, *p
;
2013 struct hlist_node
*n
;
2016 /* Is there space to add these mounts to the mount namespace? */
2018 err
= count_mounts(ns
, source_mnt
);
2023 if (IS_MNT_SHARED(dest_mnt
)) {
2024 err
= invent_group_ids(source_mnt
, true);
2027 err
= propagate_mnt(dest_mnt
, dest_mp
, source_mnt
, &tree_list
);
2030 goto out_cleanup_ids
;
2031 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
2037 detach_mnt(source_mnt
, parent_path
);
2038 attach_mnt(source_mnt
, dest_mnt
, dest_mp
);
2039 touch_mnt_namespace(source_mnt
->mnt_ns
);
2041 mnt_set_mountpoint(dest_mnt
, dest_mp
, source_mnt
);
2042 commit_tree(source_mnt
, NULL
);
2045 hlist_for_each_entry_safe(child
, n
, &tree_list
, mnt_hash
) {
2047 hlist_del_init(&child
->mnt_hash
);
2048 q
= __lookup_mnt_last(&child
->mnt_parent
->mnt
,
2049 child
->mnt_mountpoint
);
2050 commit_tree(child
, q
);
2052 unlock_mount_hash();
2057 while (!hlist_empty(&tree_list
)) {
2058 child
= hlist_entry(tree_list
.first
, struct mount
, mnt_hash
);
2059 child
->mnt_parent
->mnt_ns
->pending_mounts
= 0;
2060 umount_tree(child
, UMOUNT_SYNC
);
2062 unlock_mount_hash();
2063 cleanup_group_ids(source_mnt
, NULL
);
2065 ns
->pending_mounts
= 0;
2069 static struct mountpoint
*lock_mount(struct path
*path
)
2071 struct vfsmount
*mnt
;
2072 struct dentry
*dentry
= path
->dentry
;
2074 inode_lock(dentry
->d_inode
);
2075 if (unlikely(cant_mount(dentry
))) {
2076 inode_unlock(dentry
->d_inode
);
2077 return ERR_PTR(-ENOENT
);
2080 mnt
= lookup_mnt(path
);
2082 struct mountpoint
*mp
= get_mountpoint(dentry
);
2085 inode_unlock(dentry
->d_inode
);
2091 inode_unlock(path
->dentry
->d_inode
);
2094 dentry
= path
->dentry
= dget(mnt
->mnt_root
);
2098 static void unlock_mount(struct mountpoint
*where
)
2100 struct dentry
*dentry
= where
->m_dentry
;
2102 read_seqlock_excl(&mount_lock
);
2103 put_mountpoint(where
);
2104 read_sequnlock_excl(&mount_lock
);
2107 inode_unlock(dentry
->d_inode
);
2110 static int graft_tree(struct mount
*mnt
, struct mount
*p
, struct mountpoint
*mp
)
2112 if (mnt
->mnt
.mnt_sb
->s_flags
& MS_NOUSER
)
2115 if (d_is_dir(mp
->m_dentry
) !=
2116 d_is_dir(mnt
->mnt
.mnt_root
))
2119 return attach_recursive_mnt(mnt
, p
, mp
, NULL
);
2123 * Sanity check the flags to change_mnt_propagation.
2126 static int flags_to_propagation_type(int flags
)
2128 int type
= flags
& ~(MS_REC
| MS_SILENT
);
2130 /* Fail if any non-propagation flags are set */
2131 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2133 /* Only one propagation flag should be set */
2134 if (!is_power_of_2(type
))
2140 * recursively change the type of the mountpoint.
2142 static int do_change_type(struct path
*path
, int flag
)
2145 struct mount
*mnt
= real_mount(path
->mnt
);
2146 int recurse
= flag
& MS_REC
;
2150 if (path
->dentry
!= path
->mnt
->mnt_root
)
2153 type
= flags_to_propagation_type(flag
);
2158 if (type
== MS_SHARED
) {
2159 err
= invent_group_ids(mnt
, recurse
);
2165 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
2166 change_mnt_propagation(m
, type
);
2167 unlock_mount_hash();
2174 static bool has_locked_children(struct mount
*mnt
, struct dentry
*dentry
)
2176 struct mount
*child
;
2177 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
2178 if (!is_subdir(child
->mnt_mountpoint
, dentry
))
2181 if (child
->mnt
.mnt_flags
& MNT_LOCKED
)
2188 * do loopback mount.
2190 static int do_loopback(struct path
*path
, const char *old_name
,
2193 struct path old_path
;
2194 struct mount
*mnt
= NULL
, *old
, *parent
;
2195 struct mountpoint
*mp
;
2197 if (!old_name
|| !*old_name
)
2199 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
2204 if (mnt_ns_loop(old_path
.dentry
))
2207 mp
= lock_mount(path
);
2212 old
= real_mount(old_path
.mnt
);
2213 parent
= real_mount(path
->mnt
);
2216 if (IS_MNT_UNBINDABLE(old
))
2219 if (!check_mnt(parent
))
2222 if (!check_mnt(old
) && old_path
.dentry
->d_op
!= &ns_dentry_operations
)
2225 if (!recurse
&& has_locked_children(old
, old_path
.dentry
))
2229 mnt
= copy_tree(old
, old_path
.dentry
, CL_COPY_MNT_NS_FILE
);
2231 mnt
= clone_mnt(old
, old_path
.dentry
, 0);
2238 mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2240 err
= graft_tree(mnt
, parent
, mp
);
2243 umount_tree(mnt
, UMOUNT_SYNC
);
2244 unlock_mount_hash();
2249 path_put(&old_path
);
2253 static int change_mount_flags(struct vfsmount
*mnt
, int ms_flags
)
2256 int readonly_request
= 0;
2258 if (ms_flags
& MS_RDONLY
)
2259 readonly_request
= 1;
2260 if (readonly_request
== __mnt_is_readonly(mnt
))
2263 if (readonly_request
)
2264 error
= mnt_make_readonly(real_mount(mnt
));
2266 __mnt_unmake_readonly(real_mount(mnt
));
2271 * change filesystem flags. dir should be a physical root of filesystem.
2272 * If you've mounted a non-root directory somewhere and want to do remount
2273 * on it - tough luck.
2275 static int do_remount(struct path
*path
, int flags
, int mnt_flags
,
2279 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2280 struct mount
*mnt
= real_mount(path
->mnt
);
2282 if (!check_mnt(mnt
))
2285 if (path
->dentry
!= path
->mnt
->mnt_root
)
2288 /* Don't allow changing of locked mnt flags.
2290 * No locks need to be held here while testing the various
2291 * MNT_LOCK flags because those flags can never be cleared
2292 * once they are set.
2294 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_READONLY
) &&
2295 !(mnt_flags
& MNT_READONLY
)) {
2298 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NODEV
) &&
2299 !(mnt_flags
& MNT_NODEV
)) {
2302 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NOSUID
) &&
2303 !(mnt_flags
& MNT_NOSUID
)) {
2306 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NOEXEC
) &&
2307 !(mnt_flags
& MNT_NOEXEC
)) {
2310 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_ATIME
) &&
2311 ((mnt
->mnt
.mnt_flags
& MNT_ATIME_MASK
) != (mnt_flags
& MNT_ATIME_MASK
))) {
2315 err
= security_sb_remount(sb
, data
);
2319 down_write(&sb
->s_umount
);
2320 if (flags
& MS_BIND
)
2321 err
= change_mount_flags(path
->mnt
, flags
);
2322 else if (!ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
))
2325 err
= do_remount_sb(sb
, flags
, data
, 0);
2328 mnt_flags
|= mnt
->mnt
.mnt_flags
& ~MNT_USER_SETTABLE_MASK
;
2329 mnt
->mnt
.mnt_flags
= mnt_flags
;
2330 touch_mnt_namespace(mnt
->mnt_ns
);
2331 unlock_mount_hash();
2333 up_write(&sb
->s_umount
);
2337 static inline int tree_contains_unbindable(struct mount
*mnt
)
2340 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2341 if (IS_MNT_UNBINDABLE(p
))
2347 static int do_move_mount(struct path
*path
, const char *old_name
)
2349 struct path old_path
, parent_path
;
2352 struct mountpoint
*mp
;
2354 if (!old_name
|| !*old_name
)
2356 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
2360 mp
= lock_mount(path
);
2365 old
= real_mount(old_path
.mnt
);
2366 p
= real_mount(path
->mnt
);
2369 if (!check_mnt(p
) || !check_mnt(old
))
2372 if (old
->mnt
.mnt_flags
& MNT_LOCKED
)
2376 if (old_path
.dentry
!= old_path
.mnt
->mnt_root
)
2379 if (!mnt_has_parent(old
))
2382 if (d_is_dir(path
->dentry
) !=
2383 d_is_dir(old_path
.dentry
))
2386 * Don't move a mount residing in a shared parent.
2388 if (IS_MNT_SHARED(old
->mnt_parent
))
2391 * Don't move a mount tree containing unbindable mounts to a destination
2392 * mount which is shared.
2394 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
2397 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
2401 err
= attach_recursive_mnt(old
, real_mount(path
->mnt
), mp
, &parent_path
);
2405 /* if the mount is moved, it should no longer be expire
2407 list_del_init(&old
->mnt_expire
);
2412 path_put(&parent_path
);
2413 path_put(&old_path
);
2417 static struct vfsmount
*fs_set_subtype(struct vfsmount
*mnt
, const char *fstype
)
2420 const char *subtype
= strchr(fstype
, '.');
2429 mnt
->mnt_sb
->s_subtype
= kstrdup(subtype
, GFP_KERNEL
);
2431 if (!mnt
->mnt_sb
->s_subtype
)
2437 return ERR_PTR(err
);
2441 * add a mount into a namespace's mount tree
2443 static int do_add_mount(struct mount
*newmnt
, struct path
*path
, int mnt_flags
)
2445 struct mountpoint
*mp
;
2446 struct mount
*parent
;
2449 mnt_flags
&= ~MNT_INTERNAL_FLAGS
;
2451 mp
= lock_mount(path
);
2455 parent
= real_mount(path
->mnt
);
2457 if (unlikely(!check_mnt(parent
))) {
2458 /* that's acceptable only for automounts done in private ns */
2459 if (!(mnt_flags
& MNT_SHRINKABLE
))
2461 /* ... and for those we'd better have mountpoint still alive */
2462 if (!parent
->mnt_ns
)
2466 /* Refuse the same filesystem on the same mount point */
2468 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
2469 path
->mnt
->mnt_root
== path
->dentry
)
2473 if (d_is_symlink(newmnt
->mnt
.mnt_root
))
2476 newmnt
->mnt
.mnt_flags
= mnt_flags
;
2477 err
= graft_tree(newmnt
, parent
, mp
);
2484 static bool mount_too_revealing(struct vfsmount
*mnt
, int *new_mnt_flags
);
2487 * create a new mount for userspace and request it to be added into the
2490 static int do_new_mount(struct path
*path
, const char *fstype
, int flags
,
2491 int mnt_flags
, const char *name
, void *data
)
2493 struct file_system_type
*type
;
2494 struct vfsmount
*mnt
;
2500 type
= get_fs_type(fstype
);
2504 mnt
= vfs_kern_mount(type
, flags
, name
, data
);
2505 if (!IS_ERR(mnt
) && (type
->fs_flags
& FS_HAS_SUBTYPE
) &&
2506 !mnt
->mnt_sb
->s_subtype
)
2507 mnt
= fs_set_subtype(mnt
, fstype
);
2509 put_filesystem(type
);
2511 return PTR_ERR(mnt
);
2513 if (mount_too_revealing(mnt
, &mnt_flags
)) {
2518 err
= do_add_mount(real_mount(mnt
), path
, mnt_flags
);
2524 int finish_automount(struct vfsmount
*m
, struct path
*path
)
2526 struct mount
*mnt
= real_mount(m
);
2528 /* The new mount record should have at least 2 refs to prevent it being
2529 * expired before we get a chance to add it
2531 BUG_ON(mnt_get_count(mnt
) < 2);
2533 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
2534 m
->mnt_root
== path
->dentry
) {
2539 err
= do_add_mount(mnt
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
2543 /* remove m from any expiration list it may be on */
2544 if (!list_empty(&mnt
->mnt_expire
)) {
2546 list_del_init(&mnt
->mnt_expire
);
2555 * mnt_set_expiry - Put a mount on an expiration list
2556 * @mnt: The mount to list.
2557 * @expiry_list: The list to add the mount to.
2559 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
2563 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
2567 EXPORT_SYMBOL(mnt_set_expiry
);
2570 * process a list of expirable mountpoints with the intent of discarding any
2571 * mountpoints that aren't in use and haven't been touched since last we came
2574 void mark_mounts_for_expiry(struct list_head
*mounts
)
2576 struct mount
*mnt
, *next
;
2577 LIST_HEAD(graveyard
);
2579 if (list_empty(mounts
))
2585 /* extract from the expiration list every vfsmount that matches the
2586 * following criteria:
2587 * - only referenced by its parent vfsmount
2588 * - still marked for expiry (marked on the last call here; marks are
2589 * cleared by mntput())
2591 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
2592 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
2593 propagate_mount_busy(mnt
, 1))
2595 list_move(&mnt
->mnt_expire
, &graveyard
);
2597 while (!list_empty(&graveyard
)) {
2598 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
2599 touch_mnt_namespace(mnt
->mnt_ns
);
2600 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
2602 unlock_mount_hash();
2606 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
2609 * Ripoff of 'select_parent()'
2611 * search the list of submounts for a given mountpoint, and move any
2612 * shrinkable submounts to the 'graveyard' list.
2614 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
2616 struct mount
*this_parent
= parent
;
2617 struct list_head
*next
;
2621 next
= this_parent
->mnt_mounts
.next
;
2623 while (next
!= &this_parent
->mnt_mounts
) {
2624 struct list_head
*tmp
= next
;
2625 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
2628 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
2631 * Descend a level if the d_mounts list is non-empty.
2633 if (!list_empty(&mnt
->mnt_mounts
)) {
2638 if (!propagate_mount_busy(mnt
, 1)) {
2639 list_move_tail(&mnt
->mnt_expire
, graveyard
);
2644 * All done at this level ... ascend and resume the search
2646 if (this_parent
!= parent
) {
2647 next
= this_parent
->mnt_child
.next
;
2648 this_parent
= this_parent
->mnt_parent
;
2655 * process a list of expirable mountpoints with the intent of discarding any
2656 * submounts of a specific parent mountpoint
2658 * mount_lock must be held for write
2660 static void shrink_submounts(struct mount
*mnt
)
2662 LIST_HEAD(graveyard
);
2665 /* extract submounts of 'mountpoint' from the expiration list */
2666 while (select_submounts(mnt
, &graveyard
)) {
2667 while (!list_empty(&graveyard
)) {
2668 m
= list_first_entry(&graveyard
, struct mount
,
2670 touch_mnt_namespace(m
->mnt_ns
);
2671 umount_tree(m
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
2677 * Some copy_from_user() implementations do not return the exact number of
2678 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2679 * Note that this function differs from copy_from_user() in that it will oops
2680 * on bad values of `to', rather than returning a short copy.
2682 static long exact_copy_from_user(void *to
, const void __user
* from
,
2686 const char __user
*f
= from
;
2689 if (!access_ok(VERIFY_READ
, from
, n
))
2693 if (__get_user(c
, f
)) {
2704 void *copy_mount_options(const void __user
* data
)
2713 copy
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
2715 return ERR_PTR(-ENOMEM
);
2717 /* We only care that *some* data at the address the user
2718 * gave us is valid. Just in case, we'll zero
2719 * the remainder of the page.
2721 /* copy_from_user cannot cross TASK_SIZE ! */
2722 size
= TASK_SIZE
- (unsigned long)data
;
2723 if (size
> PAGE_SIZE
)
2726 i
= size
- exact_copy_from_user(copy
, data
, size
);
2729 return ERR_PTR(-EFAULT
);
2732 memset(copy
+ i
, 0, PAGE_SIZE
- i
);
2736 char *copy_mount_string(const void __user
*data
)
2738 return data
? strndup_user(data
, PAGE_SIZE
) : NULL
;
2742 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2743 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2745 * data is a (void *) that can point to any structure up to
2746 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2747 * information (or be NULL).
2749 * Pre-0.97 versions of mount() didn't have a flags word.
2750 * When the flags word was introduced its top half was required
2751 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2752 * Therefore, if this magic number is present, it carries no information
2753 * and must be discarded.
2755 long do_mount(const char *dev_name
, const char __user
*dir_name
,
2756 const char *type_page
, unsigned long flags
, void *data_page
)
2763 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
2764 flags
&= ~MS_MGC_MSK
;
2766 /* Basic sanity checks */
2768 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
2770 /* ... and get the mountpoint */
2771 retval
= user_path(dir_name
, &path
);
2775 retval
= security_sb_mount(dev_name
, &path
,
2776 type_page
, flags
, data_page
);
2777 if (!retval
&& !may_mount())
2779 if (!retval
&& (flags
& MS_MANDLOCK
) && !may_mandlock())
2784 /* Default to relatime unless overriden */
2785 if (!(flags
& MS_NOATIME
))
2786 mnt_flags
|= MNT_RELATIME
;
2788 /* Separate the per-mountpoint flags */
2789 if (flags
& MS_NOSUID
)
2790 mnt_flags
|= MNT_NOSUID
;
2791 if (flags
& MS_NODEV
)
2792 mnt_flags
|= MNT_NODEV
;
2793 if (flags
& MS_NOEXEC
)
2794 mnt_flags
|= MNT_NOEXEC
;
2795 if (flags
& MS_NOATIME
)
2796 mnt_flags
|= MNT_NOATIME
;
2797 if (flags
& MS_NODIRATIME
)
2798 mnt_flags
|= MNT_NODIRATIME
;
2799 if (flags
& MS_STRICTATIME
)
2800 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
2801 if (flags
& MS_RDONLY
)
2802 mnt_flags
|= MNT_READONLY
;
2804 /* The default atime for remount is preservation */
2805 if ((flags
& MS_REMOUNT
) &&
2806 ((flags
& (MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
|
2807 MS_STRICTATIME
)) == 0)) {
2808 mnt_flags
&= ~MNT_ATIME_MASK
;
2809 mnt_flags
|= path
.mnt
->mnt_flags
& MNT_ATIME_MASK
;
2812 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
| MS_BORN
|
2813 MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
| MS_KERNMOUNT
|
2814 MS_STRICTATIME
| MS_NOREMOTELOCK
| MS_SUBMOUNT
);
2816 if (flags
& MS_REMOUNT
)
2817 retval
= do_remount(&path
, flags
& ~MS_REMOUNT
, mnt_flags
,
2819 else if (flags
& MS_BIND
)
2820 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
2821 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2822 retval
= do_change_type(&path
, flags
);
2823 else if (flags
& MS_MOVE
)
2824 retval
= do_move_mount(&path
, dev_name
);
2826 retval
= do_new_mount(&path
, type_page
, flags
, mnt_flags
,
2827 dev_name
, data_page
);
2833 static struct ucounts
*inc_mnt_namespaces(struct user_namespace
*ns
)
2835 return inc_ucount(ns
, current_euid(), UCOUNT_MNT_NAMESPACES
);
2838 static void dec_mnt_namespaces(struct ucounts
*ucounts
)
2840 dec_ucount(ucounts
, UCOUNT_MNT_NAMESPACES
);
2843 static void free_mnt_ns(struct mnt_namespace
*ns
)
2845 ns_free_inum(&ns
->ns
);
2846 dec_mnt_namespaces(ns
->ucounts
);
2847 put_user_ns(ns
->user_ns
);
2852 * Assign a sequence number so we can detect when we attempt to bind
2853 * mount a reference to an older mount namespace into the current
2854 * mount namespace, preventing reference counting loops. A 64bit
2855 * number incrementing at 10Ghz will take 12,427 years to wrap which
2856 * is effectively never, so we can ignore the possibility.
2858 static atomic64_t mnt_ns_seq
= ATOMIC64_INIT(1);
2860 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*user_ns
)
2862 struct mnt_namespace
*new_ns
;
2863 struct ucounts
*ucounts
;
2866 ucounts
= inc_mnt_namespaces(user_ns
);
2868 return ERR_PTR(-ENOSPC
);
2870 new_ns
= kmalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
2872 dec_mnt_namespaces(ucounts
);
2873 return ERR_PTR(-ENOMEM
);
2875 ret
= ns_alloc_inum(&new_ns
->ns
);
2878 dec_mnt_namespaces(ucounts
);
2879 return ERR_PTR(ret
);
2881 new_ns
->ns
.ops
= &mntns_operations
;
2882 new_ns
->seq
= atomic64_add_return(1, &mnt_ns_seq
);
2883 atomic_set(&new_ns
->count
, 1);
2884 new_ns
->root
= NULL
;
2885 INIT_LIST_HEAD(&new_ns
->list
);
2886 init_waitqueue_head(&new_ns
->poll
);
2888 new_ns
->user_ns
= get_user_ns(user_ns
);
2889 new_ns
->ucounts
= ucounts
;
2891 new_ns
->pending_mounts
= 0;
2896 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
2897 struct user_namespace
*user_ns
, struct fs_struct
*new_fs
)
2899 struct mnt_namespace
*new_ns
;
2900 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
2901 struct mount
*p
, *q
;
2908 if (likely(!(flags
& CLONE_NEWNS
))) {
2915 new_ns
= alloc_mnt_ns(user_ns
);
2920 /* First pass: copy the tree topology */
2921 copy_flags
= CL_COPY_UNBINDABLE
| CL_EXPIRE
;
2922 if (user_ns
!= ns
->user_ns
)
2923 copy_flags
|= CL_SHARED_TO_SLAVE
| CL_UNPRIVILEGED
;
2924 new = copy_tree(old
, old
->mnt
.mnt_root
, copy_flags
);
2927 free_mnt_ns(new_ns
);
2928 return ERR_CAST(new);
2931 list_add_tail(&new_ns
->list
, &new->mnt_list
);
2934 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2935 * as belonging to new namespace. We have already acquired a private
2936 * fs_struct, so tsk->fs->lock is not needed.
2944 if (&p
->mnt
== new_fs
->root
.mnt
) {
2945 new_fs
->root
.mnt
= mntget(&q
->mnt
);
2948 if (&p
->mnt
== new_fs
->pwd
.mnt
) {
2949 new_fs
->pwd
.mnt
= mntget(&q
->mnt
);
2953 p
= next_mnt(p
, old
);
2954 q
= next_mnt(q
, new);
2957 while (p
->mnt
.mnt_root
!= q
->mnt
.mnt_root
)
2958 p
= next_mnt(p
, old
);
2971 * create_mnt_ns - creates a private namespace and adds a root filesystem
2972 * @mnt: pointer to the new root filesystem mountpoint
2974 static struct mnt_namespace
*create_mnt_ns(struct vfsmount
*m
)
2976 struct mnt_namespace
*new_ns
= alloc_mnt_ns(&init_user_ns
);
2977 if (!IS_ERR(new_ns
)) {
2978 struct mount
*mnt
= real_mount(m
);
2979 mnt
->mnt_ns
= new_ns
;
2982 list_add(&mnt
->mnt_list
, &new_ns
->list
);
2989 struct dentry
*mount_subtree(struct vfsmount
*mnt
, const char *name
)
2991 struct mnt_namespace
*ns
;
2992 struct super_block
*s
;
2996 ns
= create_mnt_ns(mnt
);
2998 return ERR_CAST(ns
);
3000 err
= vfs_path_lookup(mnt
->mnt_root
, mnt
,
3001 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
3006 return ERR_PTR(err
);
3008 /* trade a vfsmount reference for active sb one */
3009 s
= path
.mnt
->mnt_sb
;
3010 atomic_inc(&s
->s_active
);
3012 /* lock the sucker */
3013 down_write(&s
->s_umount
);
3014 /* ... and return the root of (sub)tree on it */
3017 EXPORT_SYMBOL(mount_subtree
);
3019 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
3020 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
3027 kernel_type
= copy_mount_string(type
);
3028 ret
= PTR_ERR(kernel_type
);
3029 if (IS_ERR(kernel_type
))
3032 kernel_dev
= copy_mount_string(dev_name
);
3033 ret
= PTR_ERR(kernel_dev
);
3034 if (IS_ERR(kernel_dev
))
3037 options
= copy_mount_options(data
);
3038 ret
= PTR_ERR(options
);
3039 if (IS_ERR(options
))
3042 ret
= do_mount(kernel_dev
, dir_name
, kernel_type
, flags
, options
);
3054 * Return true if path is reachable from root
3056 * namespace_sem or mount_lock is held
3058 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
3059 const struct path
*root
)
3061 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
3062 dentry
= mnt
->mnt_mountpoint
;
3063 mnt
= mnt
->mnt_parent
;
3065 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
3068 bool path_is_under(const struct path
*path1
, const struct path
*path2
)
3071 read_seqlock_excl(&mount_lock
);
3072 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
3073 read_sequnlock_excl(&mount_lock
);
3076 EXPORT_SYMBOL(path_is_under
);
3079 * pivot_root Semantics:
3080 * Moves the root file system of the current process to the directory put_old,
3081 * makes new_root as the new root file system of the current process, and sets
3082 * root/cwd of all processes which had them on the current root to new_root.
3085 * The new_root and put_old must be directories, and must not be on the
3086 * same file system as the current process root. The put_old must be
3087 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3088 * pointed to by put_old must yield the same directory as new_root. No other
3089 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3091 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3092 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
3093 * in this situation.
3096 * - we don't move root/cwd if they are not at the root (reason: if something
3097 * cared enough to change them, it's probably wrong to force them elsewhere)
3098 * - it's okay to pick a root that isn't the root of a file system, e.g.
3099 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3100 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3103 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
3104 const char __user
*, put_old
)
3106 struct path
new, old
, parent_path
, root_parent
, root
;
3107 struct mount
*new_mnt
, *root_mnt
, *old_mnt
;
3108 struct mountpoint
*old_mp
, *root_mp
;
3114 error
= user_path_dir(new_root
, &new);
3118 error
= user_path_dir(put_old
, &old
);
3122 error
= security_sb_pivotroot(&old
, &new);
3126 get_fs_root(current
->fs
, &root
);
3127 old_mp
= lock_mount(&old
);
3128 error
= PTR_ERR(old_mp
);
3133 new_mnt
= real_mount(new.mnt
);
3134 root_mnt
= real_mount(root
.mnt
);
3135 old_mnt
= real_mount(old
.mnt
);
3136 if (IS_MNT_SHARED(old_mnt
) ||
3137 IS_MNT_SHARED(new_mnt
->mnt_parent
) ||
3138 IS_MNT_SHARED(root_mnt
->mnt_parent
))
3140 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
3142 if (new_mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
3145 if (d_unlinked(new.dentry
))
3148 if (new_mnt
== root_mnt
|| old_mnt
== root_mnt
)
3149 goto out4
; /* loop, on the same file system */
3151 if (root
.mnt
->mnt_root
!= root
.dentry
)
3152 goto out4
; /* not a mountpoint */
3153 if (!mnt_has_parent(root_mnt
))
3154 goto out4
; /* not attached */
3155 root_mp
= root_mnt
->mnt_mp
;
3156 if (new.mnt
->mnt_root
!= new.dentry
)
3157 goto out4
; /* not a mountpoint */
3158 if (!mnt_has_parent(new_mnt
))
3159 goto out4
; /* not attached */
3160 /* make sure we can reach put_old from new_root */
3161 if (!is_path_reachable(old_mnt
, old
.dentry
, &new))
3163 /* make certain new is below the root */
3164 if (!is_path_reachable(new_mnt
, new.dentry
, &root
))
3166 root_mp
->m_count
++; /* pin it so it won't go away */
3168 detach_mnt(new_mnt
, &parent_path
);
3169 detach_mnt(root_mnt
, &root_parent
);
3170 if (root_mnt
->mnt
.mnt_flags
& MNT_LOCKED
) {
3171 new_mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
3172 root_mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
3174 /* mount old root on put_old */
3175 attach_mnt(root_mnt
, old_mnt
, old_mp
);
3176 /* mount new_root on / */
3177 attach_mnt(new_mnt
, real_mount(root_parent
.mnt
), root_mp
);
3178 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
3179 /* A moved mount should not expire automatically */
3180 list_del_init(&new_mnt
->mnt_expire
);
3181 put_mountpoint(root_mp
);
3182 unlock_mount_hash();
3183 chroot_fs_refs(&root
, &new);
3186 unlock_mount(old_mp
);
3188 path_put(&root_parent
);
3189 path_put(&parent_path
);
3201 static void __init
init_mount_tree(void)
3203 struct vfsmount
*mnt
;
3204 struct mnt_namespace
*ns
;
3206 struct file_system_type
*type
;
3208 type
= get_fs_type("rootfs");
3210 panic("Can't find rootfs type");
3211 mnt
= vfs_kern_mount(type
, 0, "rootfs", NULL
);
3212 put_filesystem(type
);
3214 panic("Can't create rootfs");
3216 ns
= create_mnt_ns(mnt
);
3218 panic("Can't allocate initial namespace");
3220 init_task
.nsproxy
->mnt_ns
= ns
;
3224 root
.dentry
= mnt
->mnt_root
;
3225 mnt
->mnt_flags
|= MNT_LOCKED
;
3227 set_fs_pwd(current
->fs
, &root
);
3228 set_fs_root(current
->fs
, &root
);
3231 void __init
mnt_init(void)
3236 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
3237 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
3239 mount_hashtable
= alloc_large_system_hash("Mount-cache",
3240 sizeof(struct hlist_head
),
3243 &m_hash_shift
, &m_hash_mask
, 0, 0);
3244 mountpoint_hashtable
= alloc_large_system_hash("Mountpoint-cache",
3245 sizeof(struct hlist_head
),
3248 &mp_hash_shift
, &mp_hash_mask
, 0, 0);
3250 if (!mount_hashtable
|| !mountpoint_hashtable
)
3251 panic("Failed to allocate mount hash table\n");
3253 for (u
= 0; u
<= m_hash_mask
; u
++)
3254 INIT_HLIST_HEAD(&mount_hashtable
[u
]);
3255 for (u
= 0; u
<= mp_hash_mask
; u
++)
3256 INIT_HLIST_HEAD(&mountpoint_hashtable
[u
]);
3262 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
3264 fs_kobj
= kobject_create_and_add("fs", NULL
);
3266 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
3271 void put_mnt_ns(struct mnt_namespace
*ns
)
3273 if (!atomic_dec_and_test(&ns
->count
))
3275 drop_collected_mounts(&ns
->root
->mnt
);
3279 struct vfsmount
*kern_mount_data(struct file_system_type
*type
, void *data
)
3281 struct vfsmount
*mnt
;
3282 mnt
= vfs_kern_mount(type
, MS_KERNMOUNT
, type
->name
, data
);
3285 * it is a longterm mount, don't release mnt until
3286 * we unmount before file sys is unregistered
3288 real_mount(mnt
)->mnt_ns
= MNT_NS_INTERNAL
;
3292 EXPORT_SYMBOL_GPL(kern_mount_data
);
3294 void kern_unmount(struct vfsmount
*mnt
)
3296 /* release long term mount so mount point can be released */
3297 if (!IS_ERR_OR_NULL(mnt
)) {
3298 real_mount(mnt
)->mnt_ns
= NULL
;
3299 synchronize_rcu(); /* yecchhh... */
3303 EXPORT_SYMBOL(kern_unmount
);
3305 bool our_mnt(struct vfsmount
*mnt
)
3307 return check_mnt(real_mount(mnt
));
3310 bool current_chrooted(void)
3312 /* Does the current process have a non-standard root */
3313 struct path ns_root
;
3314 struct path fs_root
;
3317 /* Find the namespace root */
3318 ns_root
.mnt
= ¤t
->nsproxy
->mnt_ns
->root
->mnt
;
3319 ns_root
.dentry
= ns_root
.mnt
->mnt_root
;
3321 while (d_mountpoint(ns_root
.dentry
) && follow_down_one(&ns_root
))
3324 get_fs_root(current
->fs
, &fs_root
);
3326 chrooted
= !path_equal(&fs_root
, &ns_root
);
3334 static bool mnt_already_visible(struct mnt_namespace
*ns
, struct vfsmount
*new,
3337 int new_flags
= *new_mnt_flags
;
3339 bool visible
= false;
3341 down_read(&namespace_sem
);
3342 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
3343 struct mount
*child
;
3346 if (mnt
->mnt
.mnt_sb
->s_type
!= new->mnt_sb
->s_type
)
3349 /* This mount is not fully visible if it's root directory
3350 * is not the root directory of the filesystem.
3352 if (mnt
->mnt
.mnt_root
!= mnt
->mnt
.mnt_sb
->s_root
)
3355 /* A local view of the mount flags */
3356 mnt_flags
= mnt
->mnt
.mnt_flags
;
3358 /* Don't miss readonly hidden in the superblock flags */
3359 if (mnt
->mnt
.mnt_sb
->s_flags
& MS_RDONLY
)
3360 mnt_flags
|= MNT_LOCK_READONLY
;
3362 /* Verify the mount flags are equal to or more permissive
3363 * than the proposed new mount.
3365 if ((mnt_flags
& MNT_LOCK_READONLY
) &&
3366 !(new_flags
& MNT_READONLY
))
3368 if ((mnt_flags
& MNT_LOCK_ATIME
) &&
3369 ((mnt_flags
& MNT_ATIME_MASK
) != (new_flags
& MNT_ATIME_MASK
)))
3372 /* This mount is not fully visible if there are any
3373 * locked child mounts that cover anything except for
3374 * empty directories.
3376 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
3377 struct inode
*inode
= child
->mnt_mountpoint
->d_inode
;
3378 /* Only worry about locked mounts */
3379 if (!(child
->mnt
.mnt_flags
& MNT_LOCKED
))
3381 /* Is the directory permanetly empty? */
3382 if (!is_empty_dir_inode(inode
))
3385 /* Preserve the locked attributes */
3386 *new_mnt_flags
|= mnt_flags
& (MNT_LOCK_READONLY
| \
3393 up_read(&namespace_sem
);
3397 static bool mount_too_revealing(struct vfsmount
*mnt
, int *new_mnt_flags
)
3399 const unsigned long required_iflags
= SB_I_NOEXEC
| SB_I_NODEV
;
3400 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
3401 unsigned long s_iflags
;
3403 if (ns
->user_ns
== &init_user_ns
)
3406 /* Can this filesystem be too revealing? */
3407 s_iflags
= mnt
->mnt_sb
->s_iflags
;
3408 if (!(s_iflags
& SB_I_USERNS_VISIBLE
))
3411 if ((s_iflags
& required_iflags
) != required_iflags
) {
3412 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
3417 return !mnt_already_visible(ns
, mnt
, new_mnt_flags
);
3420 bool mnt_may_suid(struct vfsmount
*mnt
)
3423 * Foreign mounts (accessed via fchdir or through /proc
3424 * symlinks) are always treated as if they are nosuid. This
3425 * prevents namespaces from trusting potentially unsafe
3426 * suid/sgid bits, file caps, or security labels that originate
3427 * in other namespaces.
3429 return !(mnt
->mnt_flags
& MNT_NOSUID
) && check_mnt(real_mount(mnt
)) &&
3430 current_in_userns(mnt
->mnt_sb
->s_user_ns
);
3433 static struct ns_common
*mntns_get(struct task_struct
*task
)
3435 struct ns_common
*ns
= NULL
;
3436 struct nsproxy
*nsproxy
;
3439 nsproxy
= task
->nsproxy
;
3441 ns
= &nsproxy
->mnt_ns
->ns
;
3442 get_mnt_ns(to_mnt_ns(ns
));
3449 static void mntns_put(struct ns_common
*ns
)
3451 put_mnt_ns(to_mnt_ns(ns
));
3454 static int mntns_install(struct nsproxy
*nsproxy
, struct ns_common
*ns
)
3456 struct fs_struct
*fs
= current
->fs
;
3457 struct mnt_namespace
*mnt_ns
= to_mnt_ns(ns
);
3460 if (!ns_capable(mnt_ns
->user_ns
, CAP_SYS_ADMIN
) ||
3461 !ns_capable(current_user_ns(), CAP_SYS_CHROOT
) ||
3462 !ns_capable(current_user_ns(), CAP_SYS_ADMIN
))
3469 put_mnt_ns(nsproxy
->mnt_ns
);
3470 nsproxy
->mnt_ns
= mnt_ns
;
3473 root
.mnt
= &mnt_ns
->root
->mnt
;
3474 root
.dentry
= mnt_ns
->root
->mnt
.mnt_root
;
3476 while(d_mountpoint(root
.dentry
) && follow_down_one(&root
))
3479 /* Update the pwd and root */
3480 set_fs_pwd(fs
, &root
);
3481 set_fs_root(fs
, &root
);
3487 static struct user_namespace
*mntns_owner(struct ns_common
*ns
)
3489 return to_mnt_ns(ns
)->user_ns
;
3492 const struct proc_ns_operations mntns_operations
= {
3494 .type
= CLONE_NEWNS
,
3497 .install
= mntns_install
,
3498 .owner
= mntns_owner
,