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/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/uaccess.h>
24 #include <linux/proc_ns.h>
25 #include <linux/magic.h>
26 #include <linux/bootmem.h>
27 #include <linux/task_work.h>
28 #include <linux/sched/task.h>
33 /* Maximum number of mounts in a mount namespace */
34 unsigned int sysctl_mount_max __read_mostly
= 100000;
36 static unsigned int m_hash_mask __read_mostly
;
37 static unsigned int m_hash_shift __read_mostly
;
38 static unsigned int mp_hash_mask __read_mostly
;
39 static unsigned int mp_hash_shift __read_mostly
;
41 static __initdata
unsigned long mhash_entries
;
42 static int __init
set_mhash_entries(char *str
)
46 mhash_entries
= simple_strtoul(str
, &str
, 0);
49 __setup("mhash_entries=", set_mhash_entries
);
51 static __initdata
unsigned long mphash_entries
;
52 static int __init
set_mphash_entries(char *str
)
56 mphash_entries
= simple_strtoul(str
, &str
, 0);
59 __setup("mphash_entries=", set_mphash_entries
);
62 static DEFINE_IDA(mnt_id_ida
);
63 static DEFINE_IDA(mnt_group_ida
);
64 static DEFINE_SPINLOCK(mnt_id_lock
);
65 static int mnt_id_start
= 0;
66 static int mnt_group_start
= 1;
68 static struct hlist_head
*mount_hashtable __read_mostly
;
69 static struct hlist_head
*mountpoint_hashtable __read_mostly
;
70 static struct kmem_cache
*mnt_cache __read_mostly
;
71 static DECLARE_RWSEM(namespace_sem
);
74 struct kobject
*fs_kobj
;
75 EXPORT_SYMBOL_GPL(fs_kobj
);
78 * vfsmount lock may be taken for read to prevent changes to the
79 * vfsmount hash, ie. during mountpoint lookups or walking back
82 * It should be taken for write in all cases where the vfsmount
83 * tree or hash is modified or when a vfsmount structure is modified.
85 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(mount_lock
);
87 static inline struct hlist_head
*m_hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
89 unsigned long tmp
= ((unsigned long)mnt
/ L1_CACHE_BYTES
);
90 tmp
+= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
91 tmp
= tmp
+ (tmp
>> m_hash_shift
);
92 return &mount_hashtable
[tmp
& m_hash_mask
];
95 static inline struct hlist_head
*mp_hash(struct dentry
*dentry
)
97 unsigned long tmp
= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
98 tmp
= tmp
+ (tmp
>> mp_hash_shift
);
99 return &mountpoint_hashtable
[tmp
& mp_hash_mask
];
102 static int mnt_alloc_id(struct mount
*mnt
)
107 ida_pre_get(&mnt_id_ida
, GFP_KERNEL
);
108 spin_lock(&mnt_id_lock
);
109 res
= ida_get_new_above(&mnt_id_ida
, mnt_id_start
, &mnt
->mnt_id
);
111 mnt_id_start
= mnt
->mnt_id
+ 1;
112 spin_unlock(&mnt_id_lock
);
119 static void mnt_free_id(struct mount
*mnt
)
121 int id
= mnt
->mnt_id
;
122 spin_lock(&mnt_id_lock
);
123 ida_remove(&mnt_id_ida
, id
);
124 if (mnt_id_start
> id
)
126 spin_unlock(&mnt_id_lock
);
130 * Allocate a new peer group ID
132 * mnt_group_ida is protected by namespace_sem
134 static int mnt_alloc_group_id(struct mount
*mnt
)
138 if (!ida_pre_get(&mnt_group_ida
, GFP_KERNEL
))
141 res
= ida_get_new_above(&mnt_group_ida
,
145 mnt_group_start
= mnt
->mnt_group_id
+ 1;
151 * Release a peer group ID
153 void mnt_release_group_id(struct mount
*mnt
)
155 int id
= mnt
->mnt_group_id
;
156 ida_remove(&mnt_group_ida
, id
);
157 if (mnt_group_start
> id
)
158 mnt_group_start
= id
;
159 mnt
->mnt_group_id
= 0;
163 * vfsmount lock must be held for read
165 static inline void mnt_add_count(struct mount
*mnt
, int n
)
168 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, n
);
177 * vfsmount lock must be held for write
179 unsigned int mnt_get_count(struct mount
*mnt
)
182 unsigned int count
= 0;
185 for_each_possible_cpu(cpu
) {
186 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_count
;
191 return mnt
->mnt_count
;
195 static void drop_mountpoint(struct fs_pin
*p
)
197 struct mount
*m
= container_of(p
, struct mount
, mnt_umount
);
198 dput(m
->mnt_ex_mountpoint
);
203 static struct mount
*alloc_vfsmnt(const char *name
)
205 struct mount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
209 err
= mnt_alloc_id(mnt
);
214 mnt
->mnt_devname
= kstrdup_const(name
, GFP_KERNEL
);
215 if (!mnt
->mnt_devname
)
220 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
222 goto out_free_devname
;
224 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
227 mnt
->mnt_writers
= 0;
230 INIT_HLIST_NODE(&mnt
->mnt_hash
);
231 INIT_LIST_HEAD(&mnt
->mnt_child
);
232 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
233 INIT_LIST_HEAD(&mnt
->mnt_list
);
234 INIT_LIST_HEAD(&mnt
->mnt_expire
);
235 INIT_LIST_HEAD(&mnt
->mnt_share
);
236 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
237 INIT_LIST_HEAD(&mnt
->mnt_slave
);
238 INIT_HLIST_NODE(&mnt
->mnt_mp_list
);
239 INIT_LIST_HEAD(&mnt
->mnt_umounting
);
240 init_fs_pin(&mnt
->mnt_umount
, drop_mountpoint
);
246 kfree_const(mnt
->mnt_devname
);
251 kmem_cache_free(mnt_cache
, mnt
);
256 * Most r/o checks on a fs are for operations that take
257 * discrete amounts of time, like a write() or unlink().
258 * We must keep track of when those operations start
259 * (for permission checks) and when they end, so that
260 * we can determine when writes are able to occur to
264 * __mnt_is_readonly: check whether a mount is read-only
265 * @mnt: the mount to check for its write status
267 * This shouldn't be used directly ouside of the VFS.
268 * It does not guarantee that the filesystem will stay
269 * r/w, just that it is right *now*. This can not and
270 * should not be used in place of IS_RDONLY(inode).
271 * mnt_want/drop_write() will _keep_ the filesystem
274 int __mnt_is_readonly(struct vfsmount
*mnt
)
276 if (mnt
->mnt_flags
& MNT_READONLY
)
278 if (mnt
->mnt_sb
->s_flags
& MS_RDONLY
)
282 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
284 static inline void mnt_inc_writers(struct mount
*mnt
)
287 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
293 static inline void mnt_dec_writers(struct mount
*mnt
)
296 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
302 static unsigned int mnt_get_writers(struct mount
*mnt
)
305 unsigned int count
= 0;
308 for_each_possible_cpu(cpu
) {
309 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_writers
;
314 return mnt
->mnt_writers
;
318 static int mnt_is_readonly(struct vfsmount
*mnt
)
320 if (mnt
->mnt_sb
->s_readonly_remount
)
322 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
324 return __mnt_is_readonly(mnt
);
328 * Most r/o & frozen checks on a fs are for operations that take discrete
329 * amounts of time, like a write() or unlink(). We must keep track of when
330 * those operations start (for permission checks) and when they end, so that we
331 * can determine when writes are able to occur to a filesystem.
334 * __mnt_want_write - get write access to a mount without freeze protection
335 * @m: the mount on which to take a write
337 * This tells the low-level filesystem that a write is about to be performed to
338 * it, and makes sure that writes are allowed (mnt it read-write) before
339 * returning success. This operation does not protect against filesystem being
340 * frozen. When the write operation is finished, __mnt_drop_write() must be
341 * called. This is effectively a refcount.
343 int __mnt_want_write(struct vfsmount
*m
)
345 struct mount
*mnt
= real_mount(m
);
349 mnt_inc_writers(mnt
);
351 * The store to mnt_inc_writers must be visible before we pass
352 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
353 * incremented count after it has set MNT_WRITE_HOLD.
356 while (ACCESS_ONCE(mnt
->mnt
.mnt_flags
) & MNT_WRITE_HOLD
)
359 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
360 * be set to match its requirements. So we must not load that until
361 * MNT_WRITE_HOLD is cleared.
364 if (mnt_is_readonly(m
)) {
365 mnt_dec_writers(mnt
);
374 * mnt_want_write - get write access to a mount
375 * @m: the mount on which to take a write
377 * This tells the low-level filesystem that a write is about to be performed to
378 * it, and makes sure that writes are allowed (mount is read-write, filesystem
379 * is not frozen) before returning success. When the write operation is
380 * finished, mnt_drop_write() must be called. This is effectively a refcount.
382 int mnt_want_write(struct vfsmount
*m
)
386 sb_start_write(m
->mnt_sb
);
387 ret
= __mnt_want_write(m
);
389 sb_end_write(m
->mnt_sb
);
392 EXPORT_SYMBOL_GPL(mnt_want_write
);
395 * mnt_clone_write - get write access to a mount
396 * @mnt: the mount on which to take a write
398 * This is effectively like mnt_want_write, except
399 * it must only be used to take an extra write reference
400 * on a mountpoint that we already know has a write reference
401 * on it. This allows some optimisation.
403 * After finished, mnt_drop_write must be called as usual to
404 * drop the reference.
406 int mnt_clone_write(struct vfsmount
*mnt
)
408 /* superblock may be r/o */
409 if (__mnt_is_readonly(mnt
))
412 mnt_inc_writers(real_mount(mnt
));
416 EXPORT_SYMBOL_GPL(mnt_clone_write
);
419 * __mnt_want_write_file - get write access to a file's mount
420 * @file: the file who's mount on which to take a write
422 * This is like __mnt_want_write, but it takes a file and can
423 * do some optimisations if the file is open for write already
425 int __mnt_want_write_file(struct file
*file
)
427 if (!(file
->f_mode
& FMODE_WRITER
))
428 return __mnt_want_write(file
->f_path
.mnt
);
430 return mnt_clone_write(file
->f_path
.mnt
);
434 * mnt_want_write_file - get write access to a file's mount
435 * @file: the file who's mount on which to take a write
437 * This is like mnt_want_write, but it takes a file and can
438 * do some optimisations if the file is open for write already
440 int mnt_want_write_file(struct file
*file
)
444 sb_start_write(file
->f_path
.mnt
->mnt_sb
);
445 ret
= __mnt_want_write_file(file
);
447 sb_end_write(file
->f_path
.mnt
->mnt_sb
);
450 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
453 * __mnt_drop_write - give up write access to a mount
454 * @mnt: the mount on which to give up write access
456 * Tells the low-level filesystem that we are done
457 * performing writes to it. Must be matched with
458 * __mnt_want_write() call above.
460 void __mnt_drop_write(struct vfsmount
*mnt
)
463 mnt_dec_writers(real_mount(mnt
));
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 * lookup_mnt - Return the first child mount mounted at path
643 * "First" means first mounted chronologically. If you create the
646 * mount /dev/sda1 /mnt
647 * mount /dev/sda2 /mnt
648 * mount /dev/sda3 /mnt
650 * Then lookup_mnt() on the base /mnt dentry in the root mount will
651 * return successively the root dentry and vfsmount of /dev/sda1, then
652 * /dev/sda2, then /dev/sda3, then NULL.
654 * lookup_mnt takes a reference to the found vfsmount.
656 struct vfsmount
*lookup_mnt(const struct path
*path
)
658 struct mount
*child_mnt
;
664 seq
= read_seqbegin(&mount_lock
);
665 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
);
666 m
= child_mnt
? &child_mnt
->mnt
: NULL
;
667 } while (!legitimize_mnt(m
, seq
));
673 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
674 * current mount namespace.
676 * The common case is dentries are not mountpoints at all and that
677 * test is handled inline. For the slow case when we are actually
678 * dealing with a mountpoint of some kind, walk through all of the
679 * mounts in the current mount namespace and test to see if the dentry
682 * The mount_hashtable is not usable in the context because we
683 * need to identify all mounts that may be in the current mount
684 * namespace not just a mount that happens to have some specified
687 bool __is_local_mountpoint(struct dentry
*dentry
)
689 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
691 bool is_covered
= false;
693 if (!d_mountpoint(dentry
))
696 down_read(&namespace_sem
);
697 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
698 is_covered
= (mnt
->mnt_mountpoint
== dentry
);
702 up_read(&namespace_sem
);
707 static struct mountpoint
*lookup_mountpoint(struct dentry
*dentry
)
709 struct hlist_head
*chain
= mp_hash(dentry
);
710 struct mountpoint
*mp
;
712 hlist_for_each_entry(mp
, chain
, m_hash
) {
713 if (mp
->m_dentry
== dentry
) {
714 /* might be worth a WARN_ON() */
715 if (d_unlinked(dentry
))
716 return ERR_PTR(-ENOENT
);
724 static struct mountpoint
*get_mountpoint(struct dentry
*dentry
)
726 struct mountpoint
*mp
, *new = NULL
;
729 if (d_mountpoint(dentry
)) {
731 read_seqlock_excl(&mount_lock
);
732 mp
= lookup_mountpoint(dentry
);
733 read_sequnlock_excl(&mount_lock
);
739 new = kmalloc(sizeof(struct mountpoint
), GFP_KERNEL
);
741 return ERR_PTR(-ENOMEM
);
744 /* Exactly one processes may set d_mounted */
745 ret
= d_set_mounted(dentry
);
747 /* Someone else set d_mounted? */
751 /* The dentry is not available as a mountpoint? */
756 /* Add the new mountpoint to the hash table */
757 read_seqlock_excl(&mount_lock
);
758 new->m_dentry
= dentry
;
760 hlist_add_head(&new->m_hash
, mp_hash(dentry
));
761 INIT_HLIST_HEAD(&new->m_list
);
762 read_sequnlock_excl(&mount_lock
);
771 static void put_mountpoint(struct mountpoint
*mp
)
773 if (!--mp
->m_count
) {
774 struct dentry
*dentry
= mp
->m_dentry
;
775 BUG_ON(!hlist_empty(&mp
->m_list
));
776 spin_lock(&dentry
->d_lock
);
777 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
778 spin_unlock(&dentry
->d_lock
);
779 hlist_del(&mp
->m_hash
);
784 static inline int check_mnt(struct mount
*mnt
)
786 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
790 * vfsmount lock must be held for write
792 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
796 wake_up_interruptible(&ns
->poll
);
801 * vfsmount lock must be held for write
803 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
805 if (ns
&& ns
->event
!= event
) {
807 wake_up_interruptible(&ns
->poll
);
812 * vfsmount lock must be held for write
814 static void unhash_mnt(struct mount
*mnt
)
816 mnt
->mnt_parent
= mnt
;
817 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
818 list_del_init(&mnt
->mnt_child
);
819 hlist_del_init_rcu(&mnt
->mnt_hash
);
820 hlist_del_init(&mnt
->mnt_mp_list
);
821 put_mountpoint(mnt
->mnt_mp
);
826 * vfsmount lock must be held for write
828 static void detach_mnt(struct mount
*mnt
, struct path
*old_path
)
830 old_path
->dentry
= mnt
->mnt_mountpoint
;
831 old_path
->mnt
= &mnt
->mnt_parent
->mnt
;
836 * vfsmount lock must be held for write
838 static void umount_mnt(struct mount
*mnt
)
840 /* old mountpoint will be dropped when we can do that */
841 mnt
->mnt_ex_mountpoint
= mnt
->mnt_mountpoint
;
846 * vfsmount lock must be held for write
848 void mnt_set_mountpoint(struct mount
*mnt
,
849 struct mountpoint
*mp
,
850 struct mount
*child_mnt
)
853 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
854 child_mnt
->mnt_mountpoint
= dget(mp
->m_dentry
);
855 child_mnt
->mnt_parent
= mnt
;
856 child_mnt
->mnt_mp
= mp
;
857 hlist_add_head(&child_mnt
->mnt_mp_list
, &mp
->m_list
);
860 static void __attach_mnt(struct mount
*mnt
, struct mount
*parent
)
862 hlist_add_head_rcu(&mnt
->mnt_hash
,
863 m_hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
864 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
868 * vfsmount lock must be held for write
870 static void attach_mnt(struct mount
*mnt
,
871 struct mount
*parent
,
872 struct mountpoint
*mp
)
874 mnt_set_mountpoint(parent
, mp
, mnt
);
875 __attach_mnt(mnt
, parent
);
878 void mnt_change_mountpoint(struct mount
*parent
, struct mountpoint
*mp
, struct mount
*mnt
)
880 struct mountpoint
*old_mp
= mnt
->mnt_mp
;
881 struct dentry
*old_mountpoint
= mnt
->mnt_mountpoint
;
882 struct mount
*old_parent
= mnt
->mnt_parent
;
884 list_del_init(&mnt
->mnt_child
);
885 hlist_del_init(&mnt
->mnt_mp_list
);
886 hlist_del_init_rcu(&mnt
->mnt_hash
);
888 attach_mnt(mnt
, parent
, mp
);
890 put_mountpoint(old_mp
);
893 * Safely avoid even the suggestion this code might sleep or
894 * lock the mount hash by taking advantage of the knowledge that
895 * mnt_change_mountpoint will not release the final reference
898 * During mounting, the mount passed in as the parent mount will
899 * continue to use the old mountpoint and during unmounting, the
900 * old mountpoint will continue to exist until namespace_unlock,
901 * which happens well after mnt_change_mountpoint.
903 spin_lock(&old_mountpoint
->d_lock
);
904 old_mountpoint
->d_lockref
.count
--;
905 spin_unlock(&old_mountpoint
->d_lock
);
907 mnt_add_count(old_parent
, -1);
911 * vfsmount lock must be held for write
913 static void commit_tree(struct mount
*mnt
)
915 struct mount
*parent
= mnt
->mnt_parent
;
918 struct mnt_namespace
*n
= parent
->mnt_ns
;
920 BUG_ON(parent
== mnt
);
922 list_add_tail(&head
, &mnt
->mnt_list
);
923 list_for_each_entry(m
, &head
, mnt_list
)
926 list_splice(&head
, n
->list
.prev
);
928 n
->mounts
+= n
->pending_mounts
;
929 n
->pending_mounts
= 0;
931 __attach_mnt(mnt
, parent
);
932 touch_mnt_namespace(n
);
935 static struct mount
*next_mnt(struct mount
*p
, struct mount
*root
)
937 struct list_head
*next
= p
->mnt_mounts
.next
;
938 if (next
== &p
->mnt_mounts
) {
942 next
= p
->mnt_child
.next
;
943 if (next
!= &p
->mnt_parent
->mnt_mounts
)
948 return list_entry(next
, struct mount
, mnt_child
);
951 static struct mount
*skip_mnt_tree(struct mount
*p
)
953 struct list_head
*prev
= p
->mnt_mounts
.prev
;
954 while (prev
!= &p
->mnt_mounts
) {
955 p
= list_entry(prev
, struct mount
, mnt_child
);
956 prev
= p
->mnt_mounts
.prev
;
962 vfs_kern_mount(struct file_system_type
*type
, int flags
, const char *name
, void *data
)
968 return ERR_PTR(-ENODEV
);
970 mnt
= alloc_vfsmnt(name
);
972 return ERR_PTR(-ENOMEM
);
974 if (flags
& MS_KERNMOUNT
)
975 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
977 root
= mount_fs(type
, flags
, name
, data
);
981 return ERR_CAST(root
);
984 mnt
->mnt
.mnt_root
= root
;
985 mnt
->mnt
.mnt_sb
= root
->d_sb
;
986 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
987 mnt
->mnt_parent
= mnt
;
989 list_add_tail(&mnt
->mnt_instance
, &root
->d_sb
->s_mounts
);
993 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
996 vfs_submount(const struct dentry
*mountpoint
, struct file_system_type
*type
,
997 const char *name
, void *data
)
999 /* Until it is worked out how to pass the user namespace
1000 * through from the parent mount to the submount don't support
1001 * unprivileged mounts with submounts.
1003 if (mountpoint
->d_sb
->s_user_ns
!= &init_user_ns
)
1004 return ERR_PTR(-EPERM
);
1006 return vfs_kern_mount(type
, MS_SUBMOUNT
, name
, data
);
1008 EXPORT_SYMBOL_GPL(vfs_submount
);
1010 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
1013 struct super_block
*sb
= old
->mnt
.mnt_sb
;
1017 mnt
= alloc_vfsmnt(old
->mnt_devname
);
1019 return ERR_PTR(-ENOMEM
);
1021 if (flag
& (CL_SLAVE
| CL_PRIVATE
| CL_SHARED_TO_SLAVE
))
1022 mnt
->mnt_group_id
= 0; /* not a peer of original */
1024 mnt
->mnt_group_id
= old
->mnt_group_id
;
1026 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
1027 err
= mnt_alloc_group_id(mnt
);
1032 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
& ~(MNT_WRITE_HOLD
|MNT_MARKED
);
1033 /* Don't allow unprivileged users to change mount flags */
1034 if (flag
& CL_UNPRIVILEGED
) {
1035 mnt
->mnt
.mnt_flags
|= MNT_LOCK_ATIME
;
1037 if (mnt
->mnt
.mnt_flags
& MNT_READONLY
)
1038 mnt
->mnt
.mnt_flags
|= MNT_LOCK_READONLY
;
1040 if (mnt
->mnt
.mnt_flags
& MNT_NODEV
)
1041 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NODEV
;
1043 if (mnt
->mnt
.mnt_flags
& MNT_NOSUID
)
1044 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NOSUID
;
1046 if (mnt
->mnt
.mnt_flags
& MNT_NOEXEC
)
1047 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NOEXEC
;
1050 /* Don't allow unprivileged users to reveal what is under a mount */
1051 if ((flag
& CL_UNPRIVILEGED
) &&
1052 (!(flag
& CL_EXPIRE
) || list_empty(&old
->mnt_expire
)))
1053 mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
1055 atomic_inc(&sb
->s_active
);
1056 mnt
->mnt
.mnt_sb
= sb
;
1057 mnt
->mnt
.mnt_root
= dget(root
);
1058 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1059 mnt
->mnt_parent
= mnt
;
1061 list_add_tail(&mnt
->mnt_instance
, &sb
->s_mounts
);
1062 unlock_mount_hash();
1064 if ((flag
& CL_SLAVE
) ||
1065 ((flag
& CL_SHARED_TO_SLAVE
) && IS_MNT_SHARED(old
))) {
1066 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
1067 mnt
->mnt_master
= old
;
1068 CLEAR_MNT_SHARED(mnt
);
1069 } else if (!(flag
& CL_PRIVATE
)) {
1070 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
1071 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
1072 if (IS_MNT_SLAVE(old
))
1073 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
1074 mnt
->mnt_master
= old
->mnt_master
;
1076 CLEAR_MNT_SHARED(mnt
);
1078 if (flag
& CL_MAKE_SHARED
)
1079 set_mnt_shared(mnt
);
1081 /* stick the duplicate mount on the same expiry list
1082 * as the original if that was on one */
1083 if (flag
& CL_EXPIRE
) {
1084 if (!list_empty(&old
->mnt_expire
))
1085 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
1093 return ERR_PTR(err
);
1096 static void cleanup_mnt(struct mount
*mnt
)
1099 * This probably indicates that somebody messed
1100 * up a mnt_want/drop_write() pair. If this
1101 * happens, the filesystem was probably unable
1102 * to make r/w->r/o transitions.
1105 * The locking used to deal with mnt_count decrement provides barriers,
1106 * so mnt_get_writers() below is safe.
1108 WARN_ON(mnt_get_writers(mnt
));
1109 if (unlikely(mnt
->mnt_pins
.first
))
1111 fsnotify_vfsmount_delete(&mnt
->mnt
);
1112 dput(mnt
->mnt
.mnt_root
);
1113 deactivate_super(mnt
->mnt
.mnt_sb
);
1115 call_rcu(&mnt
->mnt_rcu
, delayed_free_vfsmnt
);
1118 static void __cleanup_mnt(struct rcu_head
*head
)
1120 cleanup_mnt(container_of(head
, struct mount
, mnt_rcu
));
1123 static LLIST_HEAD(delayed_mntput_list
);
1124 static void delayed_mntput(struct work_struct
*unused
)
1126 struct llist_node
*node
= llist_del_all(&delayed_mntput_list
);
1127 struct llist_node
*next
;
1129 for (; node
; node
= next
) {
1130 next
= llist_next(node
);
1131 cleanup_mnt(llist_entry(node
, struct mount
, mnt_llist
));
1134 static DECLARE_DELAYED_WORK(delayed_mntput_work
, delayed_mntput
);
1136 static void mntput_no_expire(struct mount
*mnt
)
1139 mnt_add_count(mnt
, -1);
1140 if (likely(mnt
->mnt_ns
)) { /* shouldn't be the last one */
1145 if (mnt_get_count(mnt
)) {
1147 unlock_mount_hash();
1150 if (unlikely(mnt
->mnt
.mnt_flags
& MNT_DOOMED
)) {
1152 unlock_mount_hash();
1155 mnt
->mnt
.mnt_flags
|= MNT_DOOMED
;
1158 list_del(&mnt
->mnt_instance
);
1160 if (unlikely(!list_empty(&mnt
->mnt_mounts
))) {
1161 struct mount
*p
, *tmp
;
1162 list_for_each_entry_safe(p
, tmp
, &mnt
->mnt_mounts
, mnt_child
) {
1166 unlock_mount_hash();
1168 if (likely(!(mnt
->mnt
.mnt_flags
& MNT_INTERNAL
))) {
1169 struct task_struct
*task
= current
;
1170 if (likely(!(task
->flags
& PF_KTHREAD
))) {
1171 init_task_work(&mnt
->mnt_rcu
, __cleanup_mnt
);
1172 if (!task_work_add(task
, &mnt
->mnt_rcu
, true))
1175 if (llist_add(&mnt
->mnt_llist
, &delayed_mntput_list
))
1176 schedule_delayed_work(&delayed_mntput_work
, 1);
1182 void mntput(struct vfsmount
*mnt
)
1185 struct mount
*m
= real_mount(mnt
);
1186 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1187 if (unlikely(m
->mnt_expiry_mark
))
1188 m
->mnt_expiry_mark
= 0;
1189 mntput_no_expire(m
);
1192 EXPORT_SYMBOL(mntput
);
1194 struct vfsmount
*mntget(struct vfsmount
*mnt
)
1197 mnt_add_count(real_mount(mnt
), 1);
1200 EXPORT_SYMBOL(mntget
);
1202 /* path_is_mountpoint() - Check if path is a mount in the current
1205 * d_mountpoint() can only be used reliably to establish if a dentry is
1206 * not mounted in any namespace and that common case is handled inline.
1207 * d_mountpoint() isn't aware of the possibility there may be multiple
1208 * mounts using a given dentry in a different namespace. This function
1209 * checks if the passed in path is a mountpoint rather than the dentry
1212 bool path_is_mountpoint(const struct path
*path
)
1217 if (!d_mountpoint(path
->dentry
))
1222 seq
= read_seqbegin(&mount_lock
);
1223 res
= __path_is_mountpoint(path
);
1224 } while (read_seqretry(&mount_lock
, seq
));
1229 EXPORT_SYMBOL(path_is_mountpoint
);
1231 struct vfsmount
*mnt_clone_internal(const struct path
*path
)
1234 p
= clone_mnt(real_mount(path
->mnt
), path
->dentry
, CL_PRIVATE
);
1237 p
->mnt
.mnt_flags
|= MNT_INTERNAL
;
1241 static inline void mangle(struct seq_file
*m
, const char *s
)
1243 seq_escape(m
, s
, " \t\n\\");
1247 * Simple .show_options callback for filesystems which don't want to
1248 * implement more complex mount option showing.
1250 * See also save_mount_options().
1252 int generic_show_options(struct seq_file
*m
, struct dentry
*root
)
1254 const char *options
;
1257 options
= rcu_dereference(root
->d_sb
->s_options
);
1259 if (options
!= NULL
&& options
[0]) {
1267 EXPORT_SYMBOL(generic_show_options
);
1270 * If filesystem uses generic_show_options(), this function should be
1271 * called from the fill_super() callback.
1273 * The .remount_fs callback usually needs to be handled in a special
1274 * way, to make sure, that previous options are not overwritten if the
1277 * Also note, that if the filesystem's .remount_fs function doesn't
1278 * reset all options to their default value, but changes only newly
1279 * given options, then the displayed options will not reflect reality
1282 void save_mount_options(struct super_block
*sb
, char *options
)
1284 BUG_ON(sb
->s_options
);
1285 rcu_assign_pointer(sb
->s_options
, kstrdup(options
, GFP_KERNEL
));
1287 EXPORT_SYMBOL(save_mount_options
);
1289 void replace_mount_options(struct super_block
*sb
, char *options
)
1291 char *old
= sb
->s_options
;
1292 rcu_assign_pointer(sb
->s_options
, options
);
1298 EXPORT_SYMBOL(replace_mount_options
);
1300 #ifdef CONFIG_PROC_FS
1301 /* iterator; we want it to have access to namespace_sem, thus here... */
1302 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
1304 struct proc_mounts
*p
= m
->private;
1306 down_read(&namespace_sem
);
1307 if (p
->cached_event
== p
->ns
->event
) {
1308 void *v
= p
->cached_mount
;
1309 if (*pos
== p
->cached_index
)
1311 if (*pos
== p
->cached_index
+ 1) {
1312 v
= seq_list_next(v
, &p
->ns
->list
, &p
->cached_index
);
1313 return p
->cached_mount
= v
;
1317 p
->cached_event
= p
->ns
->event
;
1318 p
->cached_mount
= seq_list_start(&p
->ns
->list
, *pos
);
1319 p
->cached_index
= *pos
;
1320 return p
->cached_mount
;
1323 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
1325 struct proc_mounts
*p
= m
->private;
1327 p
->cached_mount
= seq_list_next(v
, &p
->ns
->list
, pos
);
1328 p
->cached_index
= *pos
;
1329 return p
->cached_mount
;
1332 static void m_stop(struct seq_file
*m
, void *v
)
1334 up_read(&namespace_sem
);
1337 static int m_show(struct seq_file
*m
, void *v
)
1339 struct proc_mounts
*p
= m
->private;
1340 struct mount
*r
= list_entry(v
, struct mount
, mnt_list
);
1341 return p
->show(m
, &r
->mnt
);
1344 const struct seq_operations mounts_op
= {
1350 #endif /* CONFIG_PROC_FS */
1353 * may_umount_tree - check if a mount tree is busy
1354 * @mnt: root of mount tree
1356 * This is called to check if a tree of mounts has any
1357 * open files, pwds, chroots or sub mounts that are
1360 int may_umount_tree(struct vfsmount
*m
)
1362 struct mount
*mnt
= real_mount(m
);
1363 int actual_refs
= 0;
1364 int minimum_refs
= 0;
1368 /* write lock needed for mnt_get_count */
1370 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1371 actual_refs
+= mnt_get_count(p
);
1374 unlock_mount_hash();
1376 if (actual_refs
> minimum_refs
)
1382 EXPORT_SYMBOL(may_umount_tree
);
1385 * may_umount - check if a mount point is busy
1386 * @mnt: root of mount
1388 * This is called to check if a mount point has any
1389 * open files, pwds, chroots or sub mounts. If the
1390 * mount has sub mounts this will return busy
1391 * regardless of whether the sub mounts are busy.
1393 * Doesn't take quota and stuff into account. IOW, in some cases it will
1394 * give false negatives. The main reason why it's here is that we need
1395 * a non-destructive way to look for easily umountable filesystems.
1397 int may_umount(struct vfsmount
*mnt
)
1400 down_read(&namespace_sem
);
1402 if (propagate_mount_busy(real_mount(mnt
), 2))
1404 unlock_mount_hash();
1405 up_read(&namespace_sem
);
1409 EXPORT_SYMBOL(may_umount
);
1411 static HLIST_HEAD(unmounted
); /* protected by namespace_sem */
1413 static void namespace_unlock(void)
1415 struct hlist_head head
;
1417 hlist_move_list(&unmounted
, &head
);
1419 up_write(&namespace_sem
);
1421 if (likely(hlist_empty(&head
)))
1426 group_pin_kill(&head
);
1429 static inline void namespace_lock(void)
1431 down_write(&namespace_sem
);
1434 enum umount_tree_flags
{
1436 UMOUNT_PROPAGATE
= 2,
1437 UMOUNT_CONNECTED
= 4,
1440 static bool disconnect_mount(struct mount
*mnt
, enum umount_tree_flags how
)
1442 /* Leaving mounts connected is only valid for lazy umounts */
1443 if (how
& UMOUNT_SYNC
)
1446 /* A mount without a parent has nothing to be connected to */
1447 if (!mnt_has_parent(mnt
))
1450 /* Because the reference counting rules change when mounts are
1451 * unmounted and connected, umounted mounts may not be
1452 * connected to mounted mounts.
1454 if (!(mnt
->mnt_parent
->mnt
.mnt_flags
& MNT_UMOUNT
))
1457 /* Has it been requested that the mount remain connected? */
1458 if (how
& UMOUNT_CONNECTED
)
1461 /* Is the mount locked such that it needs to remain connected? */
1462 if (IS_MNT_LOCKED(mnt
))
1465 /* By default disconnect the mount */
1470 * mount_lock must be held
1471 * namespace_sem must be held for write
1473 static void umount_tree(struct mount
*mnt
, enum umount_tree_flags how
)
1475 LIST_HEAD(tmp_list
);
1478 if (how
& UMOUNT_PROPAGATE
)
1479 propagate_mount_unlock(mnt
);
1481 /* Gather the mounts to umount */
1482 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1483 p
->mnt
.mnt_flags
|= MNT_UMOUNT
;
1484 list_move(&p
->mnt_list
, &tmp_list
);
1487 /* Hide the mounts from mnt_mounts */
1488 list_for_each_entry(p
, &tmp_list
, mnt_list
) {
1489 list_del_init(&p
->mnt_child
);
1492 /* Add propogated mounts to the tmp_list */
1493 if (how
& UMOUNT_PROPAGATE
)
1494 propagate_umount(&tmp_list
);
1496 while (!list_empty(&tmp_list
)) {
1497 struct mnt_namespace
*ns
;
1499 p
= list_first_entry(&tmp_list
, struct mount
, mnt_list
);
1500 list_del_init(&p
->mnt_expire
);
1501 list_del_init(&p
->mnt_list
);
1505 __touch_mnt_namespace(ns
);
1508 if (how
& UMOUNT_SYNC
)
1509 p
->mnt
.mnt_flags
|= MNT_SYNC_UMOUNT
;
1511 disconnect
= disconnect_mount(p
, how
);
1513 pin_insert_group(&p
->mnt_umount
, &p
->mnt_parent
->mnt
,
1514 disconnect
? &unmounted
: NULL
);
1515 if (mnt_has_parent(p
)) {
1516 mnt_add_count(p
->mnt_parent
, -1);
1518 /* Don't forget about p */
1519 list_add_tail(&p
->mnt_child
, &p
->mnt_parent
->mnt_mounts
);
1524 change_mnt_propagation(p
, MS_PRIVATE
);
1528 static void shrink_submounts(struct mount
*mnt
);
1530 static int do_umount(struct mount
*mnt
, int flags
)
1532 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1535 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1540 * Allow userspace to request a mountpoint be expired rather than
1541 * unmounting unconditionally. Unmount only happens if:
1542 * (1) the mark is already set (the mark is cleared by mntput())
1543 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1545 if (flags
& MNT_EXPIRE
) {
1546 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1547 flags
& (MNT_FORCE
| MNT_DETACH
))
1551 * probably don't strictly need the lock here if we examined
1552 * all race cases, but it's a slowpath.
1555 if (mnt_get_count(mnt
) != 2) {
1556 unlock_mount_hash();
1559 unlock_mount_hash();
1561 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1566 * If we may have to abort operations to get out of this
1567 * mount, and they will themselves hold resources we must
1568 * allow the fs to do things. In the Unix tradition of
1569 * 'Gee thats tricky lets do it in userspace' the umount_begin
1570 * might fail to complete on the first run through as other tasks
1571 * must return, and the like. Thats for the mount program to worry
1572 * about for the moment.
1575 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1576 sb
->s_op
->umount_begin(sb
);
1580 * No sense to grab the lock for this test, but test itself looks
1581 * somewhat bogus. Suggestions for better replacement?
1582 * Ho-hum... In principle, we might treat that as umount + switch
1583 * to rootfs. GC would eventually take care of the old vfsmount.
1584 * Actually it makes sense, especially if rootfs would contain a
1585 * /reboot - static binary that would close all descriptors and
1586 * call reboot(9). Then init(8) could umount root and exec /reboot.
1588 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1590 * Special case for "unmounting" root ...
1591 * we just try to remount it readonly.
1593 if (!capable(CAP_SYS_ADMIN
))
1595 down_write(&sb
->s_umount
);
1596 if (!(sb
->s_flags
& MS_RDONLY
))
1597 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
1598 up_write(&sb
->s_umount
);
1606 if (flags
& MNT_DETACH
) {
1607 if (!list_empty(&mnt
->mnt_list
))
1608 umount_tree(mnt
, UMOUNT_PROPAGATE
);
1611 shrink_submounts(mnt
);
1613 if (!propagate_mount_busy(mnt
, 2)) {
1614 if (!list_empty(&mnt
->mnt_list
))
1615 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
1619 unlock_mount_hash();
1625 * __detach_mounts - lazily unmount all mounts on the specified dentry
1627 * During unlink, rmdir, and d_drop it is possible to loose the path
1628 * to an existing mountpoint, and wind up leaking the mount.
1629 * detach_mounts allows lazily unmounting those mounts instead of
1632 * The caller may hold dentry->d_inode->i_mutex.
1634 void __detach_mounts(struct dentry
*dentry
)
1636 struct mountpoint
*mp
;
1641 mp
= lookup_mountpoint(dentry
);
1642 if (IS_ERR_OR_NULL(mp
))
1646 while (!hlist_empty(&mp
->m_list
)) {
1647 mnt
= hlist_entry(mp
->m_list
.first
, struct mount
, mnt_mp_list
);
1648 if (mnt
->mnt
.mnt_flags
& MNT_UMOUNT
) {
1649 hlist_add_head(&mnt
->mnt_umount
.s_list
, &unmounted
);
1652 else umount_tree(mnt
, UMOUNT_CONNECTED
);
1656 unlock_mount_hash();
1661 * Is the caller allowed to modify his namespace?
1663 static inline bool may_mount(void)
1665 return ns_capable(current
->nsproxy
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
);
1668 static inline bool may_mandlock(void)
1670 #ifndef CONFIG_MANDATORY_FILE_LOCKING
1673 return capable(CAP_SYS_ADMIN
);
1677 * Now umount can handle mount points as well as block devices.
1678 * This is important for filesystems which use unnamed block devices.
1680 * We now support a flag for forced unmount like the other 'big iron'
1681 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1684 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1689 int lookup_flags
= 0;
1691 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1697 if (!(flags
& UMOUNT_NOFOLLOW
))
1698 lookup_flags
|= LOOKUP_FOLLOW
;
1700 retval
= user_path_mountpoint_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1703 mnt
= real_mount(path
.mnt
);
1705 if (path
.dentry
!= path
.mnt
->mnt_root
)
1707 if (!check_mnt(mnt
))
1709 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
1712 if (flags
& MNT_FORCE
&& !capable(CAP_SYS_ADMIN
))
1715 retval
= do_umount(mnt
, flags
);
1717 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1719 mntput_no_expire(mnt
);
1724 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1727 * The 2.0 compatible umount. No flags.
1729 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1731 return sys_umount(name
, 0);
1736 static bool is_mnt_ns_file(struct dentry
*dentry
)
1738 /* Is this a proxy for a mount namespace? */
1739 return dentry
->d_op
== &ns_dentry_operations
&&
1740 dentry
->d_fsdata
== &mntns_operations
;
1743 struct mnt_namespace
*to_mnt_ns(struct ns_common
*ns
)
1745 return container_of(ns
, struct mnt_namespace
, ns
);
1748 static bool mnt_ns_loop(struct dentry
*dentry
)
1750 /* Could bind mounting the mount namespace inode cause a
1751 * mount namespace loop?
1753 struct mnt_namespace
*mnt_ns
;
1754 if (!is_mnt_ns_file(dentry
))
1757 mnt_ns
= to_mnt_ns(get_proc_ns(dentry
->d_inode
));
1758 return current
->nsproxy
->mnt_ns
->seq
>= mnt_ns
->seq
;
1761 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1764 struct mount
*res
, *p
, *q
, *r
, *parent
;
1766 if (!(flag
& CL_COPY_UNBINDABLE
) && IS_MNT_UNBINDABLE(mnt
))
1767 return ERR_PTR(-EINVAL
);
1769 if (!(flag
& CL_COPY_MNT_NS_FILE
) && is_mnt_ns_file(dentry
))
1770 return ERR_PTR(-EINVAL
);
1772 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1776 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1779 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1781 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1784 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1785 if (!(flag
& CL_COPY_UNBINDABLE
) &&
1786 IS_MNT_UNBINDABLE(s
)) {
1787 s
= skip_mnt_tree(s
);
1790 if (!(flag
& CL_COPY_MNT_NS_FILE
) &&
1791 is_mnt_ns_file(s
->mnt
.mnt_root
)) {
1792 s
= skip_mnt_tree(s
);
1795 while (p
!= s
->mnt_parent
) {
1801 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
1805 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1806 attach_mnt(q
, parent
, p
->mnt_mp
);
1807 unlock_mount_hash();
1814 umount_tree(res
, UMOUNT_SYNC
);
1815 unlock_mount_hash();
1820 /* Caller should check returned pointer for errors */
1822 struct vfsmount
*collect_mounts(const struct path
*path
)
1826 if (!check_mnt(real_mount(path
->mnt
)))
1827 tree
= ERR_PTR(-EINVAL
);
1829 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
1830 CL_COPY_ALL
| CL_PRIVATE
);
1833 return ERR_CAST(tree
);
1837 void drop_collected_mounts(struct vfsmount
*mnt
)
1841 umount_tree(real_mount(mnt
), UMOUNT_SYNC
);
1842 unlock_mount_hash();
1847 * clone_private_mount - create a private clone of a path
1849 * This creates a new vfsmount, which will be the clone of @path. The new will
1850 * not be attached anywhere in the namespace and will be private (i.e. changes
1851 * to the originating mount won't be propagated into this).
1853 * Release with mntput().
1855 struct vfsmount
*clone_private_mount(const struct path
*path
)
1857 struct mount
*old_mnt
= real_mount(path
->mnt
);
1858 struct mount
*new_mnt
;
1860 if (IS_MNT_UNBINDABLE(old_mnt
))
1861 return ERR_PTR(-EINVAL
);
1863 new_mnt
= clone_mnt(old_mnt
, path
->dentry
, CL_PRIVATE
);
1864 if (IS_ERR(new_mnt
))
1865 return ERR_CAST(new_mnt
);
1867 return &new_mnt
->mnt
;
1869 EXPORT_SYMBOL_GPL(clone_private_mount
);
1871 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1872 struct vfsmount
*root
)
1875 int res
= f(root
, arg
);
1878 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
1879 res
= f(&mnt
->mnt
, arg
);
1886 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
1890 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
1891 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
1892 mnt_release_group_id(p
);
1896 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
1900 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
1901 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
1902 int err
= mnt_alloc_group_id(p
);
1904 cleanup_group_ids(mnt
, p
);
1913 int count_mounts(struct mnt_namespace
*ns
, struct mount
*mnt
)
1915 unsigned int max
= READ_ONCE(sysctl_mount_max
);
1916 unsigned int mounts
= 0, old
, pending
, sum
;
1919 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
1923 pending
= ns
->pending_mounts
;
1924 sum
= old
+ pending
;
1928 (mounts
> (max
- sum
)))
1931 ns
->pending_mounts
= pending
+ mounts
;
1936 * @source_mnt : mount tree to be attached
1937 * @nd : place the mount tree @source_mnt is attached
1938 * @parent_nd : if non-null, detach the source_mnt from its parent and
1939 * store the parent mount and mountpoint dentry.
1940 * (done when source_mnt is moved)
1942 * NOTE: in the table below explains the semantics when a source mount
1943 * of a given type is attached to a destination mount of a given type.
1944 * ---------------------------------------------------------------------------
1945 * | BIND MOUNT OPERATION |
1946 * |**************************************************************************
1947 * | source-->| shared | private | slave | unbindable |
1951 * |**************************************************************************
1952 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1954 * |non-shared| shared (+) | private | slave (*) | invalid |
1955 * ***************************************************************************
1956 * A bind operation clones the source mount and mounts the clone on the
1957 * destination mount.
1959 * (++) the cloned mount is propagated to all the mounts in the propagation
1960 * tree of the destination mount and the cloned mount is added to
1961 * the peer group of the source mount.
1962 * (+) the cloned mount is created under the destination mount and is marked
1963 * as shared. The cloned mount is added to the peer group of the source
1965 * (+++) the mount is propagated to all the mounts in the propagation tree
1966 * of the destination mount and the cloned mount is made slave
1967 * of the same master as that of the source mount. The cloned mount
1968 * is marked as 'shared and slave'.
1969 * (*) the cloned mount is made a slave of the same master as that of the
1972 * ---------------------------------------------------------------------------
1973 * | MOVE MOUNT OPERATION |
1974 * |**************************************************************************
1975 * | source-->| shared | private | slave | unbindable |
1979 * |**************************************************************************
1980 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1982 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1983 * ***************************************************************************
1985 * (+) the mount is moved to the destination. And is then propagated to
1986 * all the mounts in the propagation tree of the destination mount.
1987 * (+*) the mount is moved to the destination.
1988 * (+++) the mount is moved to the destination and is then propagated to
1989 * all the mounts belonging to the destination mount's propagation tree.
1990 * the mount is marked as 'shared and slave'.
1991 * (*) the mount continues to be a slave at the new location.
1993 * if the source mount is a tree, the operations explained above is
1994 * applied to each mount in the tree.
1995 * Must be called without spinlocks held, since this function can sleep
1998 static int attach_recursive_mnt(struct mount
*source_mnt
,
1999 struct mount
*dest_mnt
,
2000 struct mountpoint
*dest_mp
,
2001 struct path
*parent_path
)
2003 HLIST_HEAD(tree_list
);
2004 struct mnt_namespace
*ns
= dest_mnt
->mnt_ns
;
2005 struct mountpoint
*smp
;
2006 struct mount
*child
, *p
;
2007 struct hlist_node
*n
;
2010 /* Preallocate a mountpoint in case the new mounts need
2011 * to be tucked under other mounts.
2013 smp
= get_mountpoint(source_mnt
->mnt
.mnt_root
);
2015 return PTR_ERR(smp
);
2017 /* Is there space to add these mounts to the mount namespace? */
2019 err
= count_mounts(ns
, source_mnt
);
2024 if (IS_MNT_SHARED(dest_mnt
)) {
2025 err
= invent_group_ids(source_mnt
, true);
2028 err
= propagate_mnt(dest_mnt
, dest_mp
, source_mnt
, &tree_list
);
2031 goto out_cleanup_ids
;
2032 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
2038 detach_mnt(source_mnt
, parent_path
);
2039 attach_mnt(source_mnt
, dest_mnt
, dest_mp
);
2040 touch_mnt_namespace(source_mnt
->mnt_ns
);
2042 mnt_set_mountpoint(dest_mnt
, dest_mp
, source_mnt
);
2043 commit_tree(source_mnt
);
2046 hlist_for_each_entry_safe(child
, n
, &tree_list
, mnt_hash
) {
2048 hlist_del_init(&child
->mnt_hash
);
2049 q
= __lookup_mnt(&child
->mnt_parent
->mnt
,
2050 child
->mnt_mountpoint
);
2052 mnt_change_mountpoint(child
, smp
, q
);
2055 put_mountpoint(smp
);
2056 unlock_mount_hash();
2061 while (!hlist_empty(&tree_list
)) {
2062 child
= hlist_entry(tree_list
.first
, struct mount
, mnt_hash
);
2063 child
->mnt_parent
->mnt_ns
->pending_mounts
= 0;
2064 umount_tree(child
, UMOUNT_SYNC
);
2066 unlock_mount_hash();
2067 cleanup_group_ids(source_mnt
, NULL
);
2069 ns
->pending_mounts
= 0;
2071 read_seqlock_excl(&mount_lock
);
2072 put_mountpoint(smp
);
2073 read_sequnlock_excl(&mount_lock
);
2078 static struct mountpoint
*lock_mount(struct path
*path
)
2080 struct vfsmount
*mnt
;
2081 struct dentry
*dentry
= path
->dentry
;
2083 inode_lock(dentry
->d_inode
);
2084 if (unlikely(cant_mount(dentry
))) {
2085 inode_unlock(dentry
->d_inode
);
2086 return ERR_PTR(-ENOENT
);
2089 mnt
= lookup_mnt(path
);
2091 struct mountpoint
*mp
= get_mountpoint(dentry
);
2094 inode_unlock(dentry
->d_inode
);
2100 inode_unlock(path
->dentry
->d_inode
);
2103 dentry
= path
->dentry
= dget(mnt
->mnt_root
);
2107 static void unlock_mount(struct mountpoint
*where
)
2109 struct dentry
*dentry
= where
->m_dentry
;
2111 read_seqlock_excl(&mount_lock
);
2112 put_mountpoint(where
);
2113 read_sequnlock_excl(&mount_lock
);
2116 inode_unlock(dentry
->d_inode
);
2119 static int graft_tree(struct mount
*mnt
, struct mount
*p
, struct mountpoint
*mp
)
2121 if (mnt
->mnt
.mnt_sb
->s_flags
& MS_NOUSER
)
2124 if (d_is_dir(mp
->m_dentry
) !=
2125 d_is_dir(mnt
->mnt
.mnt_root
))
2128 return attach_recursive_mnt(mnt
, p
, mp
, NULL
);
2132 * Sanity check the flags to change_mnt_propagation.
2135 static int flags_to_propagation_type(int flags
)
2137 int type
= flags
& ~(MS_REC
| MS_SILENT
);
2139 /* Fail if any non-propagation flags are set */
2140 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2142 /* Only one propagation flag should be set */
2143 if (!is_power_of_2(type
))
2149 * recursively change the type of the mountpoint.
2151 static int do_change_type(struct path
*path
, int flag
)
2154 struct mount
*mnt
= real_mount(path
->mnt
);
2155 int recurse
= flag
& MS_REC
;
2159 if (path
->dentry
!= path
->mnt
->mnt_root
)
2162 type
= flags_to_propagation_type(flag
);
2167 if (type
== MS_SHARED
) {
2168 err
= invent_group_ids(mnt
, recurse
);
2174 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
2175 change_mnt_propagation(m
, type
);
2176 unlock_mount_hash();
2183 static bool has_locked_children(struct mount
*mnt
, struct dentry
*dentry
)
2185 struct mount
*child
;
2186 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
2187 if (!is_subdir(child
->mnt_mountpoint
, dentry
))
2190 if (child
->mnt
.mnt_flags
& MNT_LOCKED
)
2197 * do loopback mount.
2199 static int do_loopback(struct path
*path
, const char *old_name
,
2202 struct path old_path
;
2203 struct mount
*mnt
= NULL
, *old
, *parent
;
2204 struct mountpoint
*mp
;
2206 if (!old_name
|| !*old_name
)
2208 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
2213 if (mnt_ns_loop(old_path
.dentry
))
2216 mp
= lock_mount(path
);
2221 old
= real_mount(old_path
.mnt
);
2222 parent
= real_mount(path
->mnt
);
2225 if (IS_MNT_UNBINDABLE(old
))
2228 if (!check_mnt(parent
))
2231 if (!check_mnt(old
) && old_path
.dentry
->d_op
!= &ns_dentry_operations
)
2234 if (!recurse
&& has_locked_children(old
, old_path
.dentry
))
2238 mnt
= copy_tree(old
, old_path
.dentry
, CL_COPY_MNT_NS_FILE
);
2240 mnt
= clone_mnt(old
, old_path
.dentry
, 0);
2247 mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2249 err
= graft_tree(mnt
, parent
, mp
);
2252 umount_tree(mnt
, UMOUNT_SYNC
);
2253 unlock_mount_hash();
2258 path_put(&old_path
);
2262 static int change_mount_flags(struct vfsmount
*mnt
, int ms_flags
)
2265 int readonly_request
= 0;
2267 if (ms_flags
& MS_RDONLY
)
2268 readonly_request
= 1;
2269 if (readonly_request
== __mnt_is_readonly(mnt
))
2272 if (readonly_request
)
2273 error
= mnt_make_readonly(real_mount(mnt
));
2275 __mnt_unmake_readonly(real_mount(mnt
));
2280 * change filesystem flags. dir should be a physical root of filesystem.
2281 * If you've mounted a non-root directory somewhere and want to do remount
2282 * on it - tough luck.
2284 static int do_remount(struct path
*path
, int flags
, int mnt_flags
,
2288 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2289 struct mount
*mnt
= real_mount(path
->mnt
);
2291 if (!check_mnt(mnt
))
2294 if (path
->dentry
!= path
->mnt
->mnt_root
)
2297 /* Don't allow changing of locked mnt flags.
2299 * No locks need to be held here while testing the various
2300 * MNT_LOCK flags because those flags can never be cleared
2301 * once they are set.
2303 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_READONLY
) &&
2304 !(mnt_flags
& MNT_READONLY
)) {
2307 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NODEV
) &&
2308 !(mnt_flags
& MNT_NODEV
)) {
2311 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NOSUID
) &&
2312 !(mnt_flags
& MNT_NOSUID
)) {
2315 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NOEXEC
) &&
2316 !(mnt_flags
& MNT_NOEXEC
)) {
2319 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_ATIME
) &&
2320 ((mnt
->mnt
.mnt_flags
& MNT_ATIME_MASK
) != (mnt_flags
& MNT_ATIME_MASK
))) {
2324 err
= security_sb_remount(sb
, data
);
2328 down_write(&sb
->s_umount
);
2329 if (flags
& MS_BIND
)
2330 err
= change_mount_flags(path
->mnt
, flags
);
2331 else if (!capable(CAP_SYS_ADMIN
))
2334 err
= do_remount_sb(sb
, flags
, data
, 0);
2337 mnt_flags
|= mnt
->mnt
.mnt_flags
& ~MNT_USER_SETTABLE_MASK
;
2338 mnt
->mnt
.mnt_flags
= mnt_flags
;
2339 touch_mnt_namespace(mnt
->mnt_ns
);
2340 unlock_mount_hash();
2342 up_write(&sb
->s_umount
);
2346 static inline int tree_contains_unbindable(struct mount
*mnt
)
2349 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2350 if (IS_MNT_UNBINDABLE(p
))
2356 static int do_move_mount(struct path
*path
, const char *old_name
)
2358 struct path old_path
, parent_path
;
2361 struct mountpoint
*mp
;
2363 if (!old_name
|| !*old_name
)
2365 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
2369 mp
= lock_mount(path
);
2374 old
= real_mount(old_path
.mnt
);
2375 p
= real_mount(path
->mnt
);
2378 if (!check_mnt(p
) || !check_mnt(old
))
2381 if (old
->mnt
.mnt_flags
& MNT_LOCKED
)
2385 if (old_path
.dentry
!= old_path
.mnt
->mnt_root
)
2388 if (!mnt_has_parent(old
))
2391 if (d_is_dir(path
->dentry
) !=
2392 d_is_dir(old_path
.dentry
))
2395 * Don't move a mount residing in a shared parent.
2397 if (IS_MNT_SHARED(old
->mnt_parent
))
2400 * Don't move a mount tree containing unbindable mounts to a destination
2401 * mount which is shared.
2403 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
2406 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
2410 err
= attach_recursive_mnt(old
, real_mount(path
->mnt
), mp
, &parent_path
);
2414 /* if the mount is moved, it should no longer be expire
2416 list_del_init(&old
->mnt_expire
);
2421 path_put(&parent_path
);
2422 path_put(&old_path
);
2426 static struct vfsmount
*fs_set_subtype(struct vfsmount
*mnt
, const char *fstype
)
2429 const char *subtype
= strchr(fstype
, '.');
2438 mnt
->mnt_sb
->s_subtype
= kstrdup(subtype
, GFP_KERNEL
);
2440 if (!mnt
->mnt_sb
->s_subtype
)
2446 return ERR_PTR(err
);
2450 * add a mount into a namespace's mount tree
2452 static int do_add_mount(struct mount
*newmnt
, struct path
*path
, int mnt_flags
)
2454 struct mountpoint
*mp
;
2455 struct mount
*parent
;
2458 mnt_flags
&= ~MNT_INTERNAL_FLAGS
;
2460 mp
= lock_mount(path
);
2464 parent
= real_mount(path
->mnt
);
2466 if (unlikely(!check_mnt(parent
))) {
2467 /* that's acceptable only for automounts done in private ns */
2468 if (!(mnt_flags
& MNT_SHRINKABLE
))
2470 /* ... and for those we'd better have mountpoint still alive */
2471 if (!parent
->mnt_ns
)
2475 /* Refuse the same filesystem on the same mount point */
2477 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
2478 path
->mnt
->mnt_root
== path
->dentry
)
2482 if (d_is_symlink(newmnt
->mnt
.mnt_root
))
2485 newmnt
->mnt
.mnt_flags
= mnt_flags
;
2486 err
= graft_tree(newmnt
, parent
, mp
);
2493 static bool mount_too_revealing(struct vfsmount
*mnt
, int *new_mnt_flags
);
2496 * create a new mount for userspace and request it to be added into the
2499 static int do_new_mount(struct path
*path
, const char *fstype
, int flags
,
2500 int mnt_flags
, const char *name
, void *data
)
2502 struct file_system_type
*type
;
2503 struct vfsmount
*mnt
;
2509 type
= get_fs_type(fstype
);
2513 mnt
= vfs_kern_mount(type
, flags
, name
, data
);
2514 if (!IS_ERR(mnt
) && (type
->fs_flags
& FS_HAS_SUBTYPE
) &&
2515 !mnt
->mnt_sb
->s_subtype
)
2516 mnt
= fs_set_subtype(mnt
, fstype
);
2518 put_filesystem(type
);
2520 return PTR_ERR(mnt
);
2522 if (mount_too_revealing(mnt
, &mnt_flags
)) {
2527 err
= do_add_mount(real_mount(mnt
), path
, mnt_flags
);
2533 int finish_automount(struct vfsmount
*m
, struct path
*path
)
2535 struct mount
*mnt
= real_mount(m
);
2537 /* The new mount record should have at least 2 refs to prevent it being
2538 * expired before we get a chance to add it
2540 BUG_ON(mnt_get_count(mnt
) < 2);
2542 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
2543 m
->mnt_root
== path
->dentry
) {
2548 err
= do_add_mount(mnt
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
2552 /* remove m from any expiration list it may be on */
2553 if (!list_empty(&mnt
->mnt_expire
)) {
2555 list_del_init(&mnt
->mnt_expire
);
2564 * mnt_set_expiry - Put a mount on an expiration list
2565 * @mnt: The mount to list.
2566 * @expiry_list: The list to add the mount to.
2568 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
2572 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
2576 EXPORT_SYMBOL(mnt_set_expiry
);
2579 * process a list of expirable mountpoints with the intent of discarding any
2580 * mountpoints that aren't in use and haven't been touched since last we came
2583 void mark_mounts_for_expiry(struct list_head
*mounts
)
2585 struct mount
*mnt
, *next
;
2586 LIST_HEAD(graveyard
);
2588 if (list_empty(mounts
))
2594 /* extract from the expiration list every vfsmount that matches the
2595 * following criteria:
2596 * - only referenced by its parent vfsmount
2597 * - still marked for expiry (marked on the last call here; marks are
2598 * cleared by mntput())
2600 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
2601 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
2602 propagate_mount_busy(mnt
, 1))
2604 list_move(&mnt
->mnt_expire
, &graveyard
);
2606 while (!list_empty(&graveyard
)) {
2607 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
2608 touch_mnt_namespace(mnt
->mnt_ns
);
2609 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
2611 unlock_mount_hash();
2615 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
2618 * Ripoff of 'select_parent()'
2620 * search the list of submounts for a given mountpoint, and move any
2621 * shrinkable submounts to the 'graveyard' list.
2623 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
2625 struct mount
*this_parent
= parent
;
2626 struct list_head
*next
;
2630 next
= this_parent
->mnt_mounts
.next
;
2632 while (next
!= &this_parent
->mnt_mounts
) {
2633 struct list_head
*tmp
= next
;
2634 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
2637 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
2640 * Descend a level if the d_mounts list is non-empty.
2642 if (!list_empty(&mnt
->mnt_mounts
)) {
2647 if (!propagate_mount_busy(mnt
, 1)) {
2648 list_move_tail(&mnt
->mnt_expire
, graveyard
);
2653 * All done at this level ... ascend and resume the search
2655 if (this_parent
!= parent
) {
2656 next
= this_parent
->mnt_child
.next
;
2657 this_parent
= this_parent
->mnt_parent
;
2664 * process a list of expirable mountpoints with the intent of discarding any
2665 * submounts of a specific parent mountpoint
2667 * mount_lock must be held for write
2669 static void shrink_submounts(struct mount
*mnt
)
2671 LIST_HEAD(graveyard
);
2674 /* extract submounts of 'mountpoint' from the expiration list */
2675 while (select_submounts(mnt
, &graveyard
)) {
2676 while (!list_empty(&graveyard
)) {
2677 m
= list_first_entry(&graveyard
, struct mount
,
2679 touch_mnt_namespace(m
->mnt_ns
);
2680 umount_tree(m
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
2686 * Some copy_from_user() implementations do not return the exact number of
2687 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2688 * Note that this function differs from copy_from_user() in that it will oops
2689 * on bad values of `to', rather than returning a short copy.
2691 static long exact_copy_from_user(void *to
, const void __user
* from
,
2695 const char __user
*f
= from
;
2698 if (!access_ok(VERIFY_READ
, from
, n
))
2702 if (__get_user(c
, f
)) {
2713 void *copy_mount_options(const void __user
* data
)
2722 copy
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
2724 return ERR_PTR(-ENOMEM
);
2726 /* We only care that *some* data at the address the user
2727 * gave us is valid. Just in case, we'll zero
2728 * the remainder of the page.
2730 /* copy_from_user cannot cross TASK_SIZE ! */
2731 size
= TASK_SIZE
- (unsigned long)data
;
2732 if (size
> PAGE_SIZE
)
2735 i
= size
- exact_copy_from_user(copy
, data
, size
);
2738 return ERR_PTR(-EFAULT
);
2741 memset(copy
+ i
, 0, PAGE_SIZE
- i
);
2745 char *copy_mount_string(const void __user
*data
)
2747 return data
? strndup_user(data
, PAGE_SIZE
) : NULL
;
2751 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2752 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2754 * data is a (void *) that can point to any structure up to
2755 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2756 * information (or be NULL).
2758 * Pre-0.97 versions of mount() didn't have a flags word.
2759 * When the flags word was introduced its top half was required
2760 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2761 * Therefore, if this magic number is present, it carries no information
2762 * and must be discarded.
2764 long do_mount(const char *dev_name
, const char __user
*dir_name
,
2765 const char *type_page
, unsigned long flags
, void *data_page
)
2772 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
2773 flags
&= ~MS_MGC_MSK
;
2775 /* Basic sanity checks */
2777 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
2779 /* ... and get the mountpoint */
2780 retval
= user_path(dir_name
, &path
);
2784 retval
= security_sb_mount(dev_name
, &path
,
2785 type_page
, flags
, data_page
);
2786 if (!retval
&& !may_mount())
2788 if (!retval
&& (flags
& MS_MANDLOCK
) && !may_mandlock())
2793 /* Default to relatime unless overriden */
2794 if (!(flags
& MS_NOATIME
))
2795 mnt_flags
|= MNT_RELATIME
;
2797 /* Separate the per-mountpoint flags */
2798 if (flags
& MS_NOSUID
)
2799 mnt_flags
|= MNT_NOSUID
;
2800 if (flags
& MS_NODEV
)
2801 mnt_flags
|= MNT_NODEV
;
2802 if (flags
& MS_NOEXEC
)
2803 mnt_flags
|= MNT_NOEXEC
;
2804 if (flags
& MS_NOATIME
)
2805 mnt_flags
|= MNT_NOATIME
;
2806 if (flags
& MS_NODIRATIME
)
2807 mnt_flags
|= MNT_NODIRATIME
;
2808 if (flags
& MS_STRICTATIME
)
2809 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
2810 if (flags
& MS_RDONLY
)
2811 mnt_flags
|= MNT_READONLY
;
2813 /* The default atime for remount is preservation */
2814 if ((flags
& MS_REMOUNT
) &&
2815 ((flags
& (MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
|
2816 MS_STRICTATIME
)) == 0)) {
2817 mnt_flags
&= ~MNT_ATIME_MASK
;
2818 mnt_flags
|= path
.mnt
->mnt_flags
& MNT_ATIME_MASK
;
2821 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
| MS_BORN
|
2822 MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
| MS_KERNMOUNT
|
2823 MS_STRICTATIME
| MS_NOREMOTELOCK
| MS_SUBMOUNT
);
2825 if (flags
& MS_REMOUNT
)
2826 retval
= do_remount(&path
, flags
& ~MS_REMOUNT
, mnt_flags
,
2828 else if (flags
& MS_BIND
)
2829 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
2830 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2831 retval
= do_change_type(&path
, flags
);
2832 else if (flags
& MS_MOVE
)
2833 retval
= do_move_mount(&path
, dev_name
);
2835 retval
= do_new_mount(&path
, type_page
, flags
, mnt_flags
,
2836 dev_name
, data_page
);
2842 static struct ucounts
*inc_mnt_namespaces(struct user_namespace
*ns
)
2844 return inc_ucount(ns
, current_euid(), UCOUNT_MNT_NAMESPACES
);
2847 static void dec_mnt_namespaces(struct ucounts
*ucounts
)
2849 dec_ucount(ucounts
, UCOUNT_MNT_NAMESPACES
);
2852 static void free_mnt_ns(struct mnt_namespace
*ns
)
2854 ns_free_inum(&ns
->ns
);
2855 dec_mnt_namespaces(ns
->ucounts
);
2856 put_user_ns(ns
->user_ns
);
2861 * Assign a sequence number so we can detect when we attempt to bind
2862 * mount a reference to an older mount namespace into the current
2863 * mount namespace, preventing reference counting loops. A 64bit
2864 * number incrementing at 10Ghz will take 12,427 years to wrap which
2865 * is effectively never, so we can ignore the possibility.
2867 static atomic64_t mnt_ns_seq
= ATOMIC64_INIT(1);
2869 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*user_ns
)
2871 struct mnt_namespace
*new_ns
;
2872 struct ucounts
*ucounts
;
2875 ucounts
= inc_mnt_namespaces(user_ns
);
2877 return ERR_PTR(-ENOSPC
);
2879 new_ns
= kmalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
2881 dec_mnt_namespaces(ucounts
);
2882 return ERR_PTR(-ENOMEM
);
2884 ret
= ns_alloc_inum(&new_ns
->ns
);
2887 dec_mnt_namespaces(ucounts
);
2888 return ERR_PTR(ret
);
2890 new_ns
->ns
.ops
= &mntns_operations
;
2891 new_ns
->seq
= atomic64_add_return(1, &mnt_ns_seq
);
2892 atomic_set(&new_ns
->count
, 1);
2893 new_ns
->root
= NULL
;
2894 INIT_LIST_HEAD(&new_ns
->list
);
2895 init_waitqueue_head(&new_ns
->poll
);
2897 new_ns
->user_ns
= get_user_ns(user_ns
);
2898 new_ns
->ucounts
= ucounts
;
2900 new_ns
->pending_mounts
= 0;
2905 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
2906 struct user_namespace
*user_ns
, struct fs_struct
*new_fs
)
2908 struct mnt_namespace
*new_ns
;
2909 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
2910 struct mount
*p
, *q
;
2917 if (likely(!(flags
& CLONE_NEWNS
))) {
2924 new_ns
= alloc_mnt_ns(user_ns
);
2929 /* First pass: copy the tree topology */
2930 copy_flags
= CL_COPY_UNBINDABLE
| CL_EXPIRE
;
2931 if (user_ns
!= ns
->user_ns
)
2932 copy_flags
|= CL_SHARED_TO_SLAVE
| CL_UNPRIVILEGED
;
2933 new = copy_tree(old
, old
->mnt
.mnt_root
, copy_flags
);
2936 free_mnt_ns(new_ns
);
2937 return ERR_CAST(new);
2940 list_add_tail(&new_ns
->list
, &new->mnt_list
);
2943 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2944 * as belonging to new namespace. We have already acquired a private
2945 * fs_struct, so tsk->fs->lock is not needed.
2953 if (&p
->mnt
== new_fs
->root
.mnt
) {
2954 new_fs
->root
.mnt
= mntget(&q
->mnt
);
2957 if (&p
->mnt
== new_fs
->pwd
.mnt
) {
2958 new_fs
->pwd
.mnt
= mntget(&q
->mnt
);
2962 p
= next_mnt(p
, old
);
2963 q
= next_mnt(q
, new);
2966 while (p
->mnt
.mnt_root
!= q
->mnt
.mnt_root
)
2967 p
= next_mnt(p
, old
);
2980 * create_mnt_ns - creates a private namespace and adds a root filesystem
2981 * @mnt: pointer to the new root filesystem mountpoint
2983 static struct mnt_namespace
*create_mnt_ns(struct vfsmount
*m
)
2985 struct mnt_namespace
*new_ns
= alloc_mnt_ns(&init_user_ns
);
2986 if (!IS_ERR(new_ns
)) {
2987 struct mount
*mnt
= real_mount(m
);
2988 mnt
->mnt_ns
= new_ns
;
2991 list_add(&mnt
->mnt_list
, &new_ns
->list
);
2998 struct dentry
*mount_subtree(struct vfsmount
*mnt
, const char *name
)
3000 struct mnt_namespace
*ns
;
3001 struct super_block
*s
;
3005 ns
= create_mnt_ns(mnt
);
3007 return ERR_CAST(ns
);
3009 err
= vfs_path_lookup(mnt
->mnt_root
, mnt
,
3010 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
3015 return ERR_PTR(err
);
3017 /* trade a vfsmount reference for active sb one */
3018 s
= path
.mnt
->mnt_sb
;
3019 atomic_inc(&s
->s_active
);
3021 /* lock the sucker */
3022 down_write(&s
->s_umount
);
3023 /* ... and return the root of (sub)tree on it */
3026 EXPORT_SYMBOL(mount_subtree
);
3028 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
3029 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
3036 kernel_type
= copy_mount_string(type
);
3037 ret
= PTR_ERR(kernel_type
);
3038 if (IS_ERR(kernel_type
))
3041 kernel_dev
= copy_mount_string(dev_name
);
3042 ret
= PTR_ERR(kernel_dev
);
3043 if (IS_ERR(kernel_dev
))
3046 options
= copy_mount_options(data
);
3047 ret
= PTR_ERR(options
);
3048 if (IS_ERR(options
))
3051 ret
= do_mount(kernel_dev
, dir_name
, kernel_type
, flags
, options
);
3063 * Return true if path is reachable from root
3065 * namespace_sem or mount_lock is held
3067 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
3068 const struct path
*root
)
3070 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
3071 dentry
= mnt
->mnt_mountpoint
;
3072 mnt
= mnt
->mnt_parent
;
3074 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
3077 bool path_is_under(const struct path
*path1
, const struct path
*path2
)
3080 read_seqlock_excl(&mount_lock
);
3081 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
3082 read_sequnlock_excl(&mount_lock
);
3085 EXPORT_SYMBOL(path_is_under
);
3088 * pivot_root Semantics:
3089 * Moves the root file system of the current process to the directory put_old,
3090 * makes new_root as the new root file system of the current process, and sets
3091 * root/cwd of all processes which had them on the current root to new_root.
3094 * The new_root and put_old must be directories, and must not be on the
3095 * same file system as the current process root. The put_old must be
3096 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3097 * pointed to by put_old must yield the same directory as new_root. No other
3098 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3100 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3101 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
3102 * in this situation.
3105 * - we don't move root/cwd if they are not at the root (reason: if something
3106 * cared enough to change them, it's probably wrong to force them elsewhere)
3107 * - it's okay to pick a root that isn't the root of a file system, e.g.
3108 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3109 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3112 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
3113 const char __user
*, put_old
)
3115 struct path
new, old
, parent_path
, root_parent
, root
;
3116 struct mount
*new_mnt
, *root_mnt
, *old_mnt
;
3117 struct mountpoint
*old_mp
, *root_mp
;
3123 error
= user_path_dir(new_root
, &new);
3127 error
= user_path_dir(put_old
, &old
);
3131 error
= security_sb_pivotroot(&old
, &new);
3135 get_fs_root(current
->fs
, &root
);
3136 old_mp
= lock_mount(&old
);
3137 error
= PTR_ERR(old_mp
);
3142 new_mnt
= real_mount(new.mnt
);
3143 root_mnt
= real_mount(root
.mnt
);
3144 old_mnt
= real_mount(old
.mnt
);
3145 if (IS_MNT_SHARED(old_mnt
) ||
3146 IS_MNT_SHARED(new_mnt
->mnt_parent
) ||
3147 IS_MNT_SHARED(root_mnt
->mnt_parent
))
3149 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
3151 if (new_mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
3154 if (d_unlinked(new.dentry
))
3157 if (new_mnt
== root_mnt
|| old_mnt
== root_mnt
)
3158 goto out4
; /* loop, on the same file system */
3160 if (root
.mnt
->mnt_root
!= root
.dentry
)
3161 goto out4
; /* not a mountpoint */
3162 if (!mnt_has_parent(root_mnt
))
3163 goto out4
; /* not attached */
3164 root_mp
= root_mnt
->mnt_mp
;
3165 if (new.mnt
->mnt_root
!= new.dentry
)
3166 goto out4
; /* not a mountpoint */
3167 if (!mnt_has_parent(new_mnt
))
3168 goto out4
; /* not attached */
3169 /* make sure we can reach put_old from new_root */
3170 if (!is_path_reachable(old_mnt
, old
.dentry
, &new))
3172 /* make certain new is below the root */
3173 if (!is_path_reachable(new_mnt
, new.dentry
, &root
))
3175 root_mp
->m_count
++; /* pin it so it won't go away */
3177 detach_mnt(new_mnt
, &parent_path
);
3178 detach_mnt(root_mnt
, &root_parent
);
3179 if (root_mnt
->mnt
.mnt_flags
& MNT_LOCKED
) {
3180 new_mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
3181 root_mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
3183 /* mount old root on put_old */
3184 attach_mnt(root_mnt
, old_mnt
, old_mp
);
3185 /* mount new_root on / */
3186 attach_mnt(new_mnt
, real_mount(root_parent
.mnt
), root_mp
);
3187 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
3188 /* A moved mount should not expire automatically */
3189 list_del_init(&new_mnt
->mnt_expire
);
3190 put_mountpoint(root_mp
);
3191 unlock_mount_hash();
3192 chroot_fs_refs(&root
, &new);
3195 unlock_mount(old_mp
);
3197 path_put(&root_parent
);
3198 path_put(&parent_path
);
3210 static void __init
init_mount_tree(void)
3212 struct vfsmount
*mnt
;
3213 struct mnt_namespace
*ns
;
3215 struct file_system_type
*type
;
3217 type
= get_fs_type("rootfs");
3219 panic("Can't find rootfs type");
3220 mnt
= vfs_kern_mount(type
, 0, "rootfs", NULL
);
3221 put_filesystem(type
);
3223 panic("Can't create rootfs");
3225 ns
= create_mnt_ns(mnt
);
3227 panic("Can't allocate initial namespace");
3229 init_task
.nsproxy
->mnt_ns
= ns
;
3233 root
.dentry
= mnt
->mnt_root
;
3234 mnt
->mnt_flags
|= MNT_LOCKED
;
3236 set_fs_pwd(current
->fs
, &root
);
3237 set_fs_root(current
->fs
, &root
);
3240 void __init
mnt_init(void)
3244 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
3245 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
3247 mount_hashtable
= alloc_large_system_hash("Mount-cache",
3248 sizeof(struct hlist_head
),
3251 &m_hash_shift
, &m_hash_mask
, 0, 0);
3252 mountpoint_hashtable
= alloc_large_system_hash("Mountpoint-cache",
3253 sizeof(struct hlist_head
),
3256 &mp_hash_shift
, &mp_hash_mask
, 0, 0);
3258 if (!mount_hashtable
|| !mountpoint_hashtable
)
3259 panic("Failed to allocate mount hash table\n");
3265 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
3267 fs_kobj
= kobject_create_and_add("fs", NULL
);
3269 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
3274 void put_mnt_ns(struct mnt_namespace
*ns
)
3276 if (!atomic_dec_and_test(&ns
->count
))
3278 drop_collected_mounts(&ns
->root
->mnt
);
3282 struct vfsmount
*kern_mount_data(struct file_system_type
*type
, void *data
)
3284 struct vfsmount
*mnt
;
3285 mnt
= vfs_kern_mount(type
, MS_KERNMOUNT
, type
->name
, data
);
3288 * it is a longterm mount, don't release mnt until
3289 * we unmount before file sys is unregistered
3291 real_mount(mnt
)->mnt_ns
= MNT_NS_INTERNAL
;
3295 EXPORT_SYMBOL_GPL(kern_mount_data
);
3297 void kern_unmount(struct vfsmount
*mnt
)
3299 /* release long term mount so mount point can be released */
3300 if (!IS_ERR_OR_NULL(mnt
)) {
3301 real_mount(mnt
)->mnt_ns
= NULL
;
3302 synchronize_rcu(); /* yecchhh... */
3306 EXPORT_SYMBOL(kern_unmount
);
3308 bool our_mnt(struct vfsmount
*mnt
)
3310 return check_mnt(real_mount(mnt
));
3313 bool current_chrooted(void)
3315 /* Does the current process have a non-standard root */
3316 struct path ns_root
;
3317 struct path fs_root
;
3320 /* Find the namespace root */
3321 ns_root
.mnt
= ¤t
->nsproxy
->mnt_ns
->root
->mnt
;
3322 ns_root
.dentry
= ns_root
.mnt
->mnt_root
;
3324 while (d_mountpoint(ns_root
.dentry
) && follow_down_one(&ns_root
))
3327 get_fs_root(current
->fs
, &fs_root
);
3329 chrooted
= !path_equal(&fs_root
, &ns_root
);
3337 static bool mnt_already_visible(struct mnt_namespace
*ns
, struct vfsmount
*new,
3340 int new_flags
= *new_mnt_flags
;
3342 bool visible
= false;
3344 down_read(&namespace_sem
);
3345 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
3346 struct mount
*child
;
3349 if (mnt
->mnt
.mnt_sb
->s_type
!= new->mnt_sb
->s_type
)
3352 /* This mount is not fully visible if it's root directory
3353 * is not the root directory of the filesystem.
3355 if (mnt
->mnt
.mnt_root
!= mnt
->mnt
.mnt_sb
->s_root
)
3358 /* A local view of the mount flags */
3359 mnt_flags
= mnt
->mnt
.mnt_flags
;
3361 /* Don't miss readonly hidden in the superblock flags */
3362 if (mnt
->mnt
.mnt_sb
->s_flags
& MS_RDONLY
)
3363 mnt_flags
|= MNT_LOCK_READONLY
;
3365 /* Verify the mount flags are equal to or more permissive
3366 * than the proposed new mount.
3368 if ((mnt_flags
& MNT_LOCK_READONLY
) &&
3369 !(new_flags
& MNT_READONLY
))
3371 if ((mnt_flags
& MNT_LOCK_ATIME
) &&
3372 ((mnt_flags
& MNT_ATIME_MASK
) != (new_flags
& MNT_ATIME_MASK
)))
3375 /* This mount is not fully visible if there are any
3376 * locked child mounts that cover anything except for
3377 * empty directories.
3379 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
3380 struct inode
*inode
= child
->mnt_mountpoint
->d_inode
;
3381 /* Only worry about locked mounts */
3382 if (!(child
->mnt
.mnt_flags
& MNT_LOCKED
))
3384 /* Is the directory permanetly empty? */
3385 if (!is_empty_dir_inode(inode
))
3388 /* Preserve the locked attributes */
3389 *new_mnt_flags
|= mnt_flags
& (MNT_LOCK_READONLY
| \
3396 up_read(&namespace_sem
);
3400 static bool mount_too_revealing(struct vfsmount
*mnt
, int *new_mnt_flags
)
3402 const unsigned long required_iflags
= SB_I_NOEXEC
| SB_I_NODEV
;
3403 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
3404 unsigned long s_iflags
;
3406 if (ns
->user_ns
== &init_user_ns
)
3409 /* Can this filesystem be too revealing? */
3410 s_iflags
= mnt
->mnt_sb
->s_iflags
;
3411 if (!(s_iflags
& SB_I_USERNS_VISIBLE
))
3414 if ((s_iflags
& required_iflags
) != required_iflags
) {
3415 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
3420 return !mnt_already_visible(ns
, mnt
, new_mnt_flags
);
3423 bool mnt_may_suid(struct vfsmount
*mnt
)
3426 * Foreign mounts (accessed via fchdir or through /proc
3427 * symlinks) are always treated as if they are nosuid. This
3428 * prevents namespaces from trusting potentially unsafe
3429 * suid/sgid bits, file caps, or security labels that originate
3430 * in other namespaces.
3432 return !(mnt
->mnt_flags
& MNT_NOSUID
) && check_mnt(real_mount(mnt
)) &&
3433 current_in_userns(mnt
->mnt_sb
->s_user_ns
);
3436 static struct ns_common
*mntns_get(struct task_struct
*task
)
3438 struct ns_common
*ns
= NULL
;
3439 struct nsproxy
*nsproxy
;
3442 nsproxy
= task
->nsproxy
;
3444 ns
= &nsproxy
->mnt_ns
->ns
;
3445 get_mnt_ns(to_mnt_ns(ns
));
3452 static void mntns_put(struct ns_common
*ns
)
3454 put_mnt_ns(to_mnt_ns(ns
));
3457 static int mntns_install(struct nsproxy
*nsproxy
, struct ns_common
*ns
)
3459 struct fs_struct
*fs
= current
->fs
;
3460 struct mnt_namespace
*mnt_ns
= to_mnt_ns(ns
), *old_mnt_ns
;
3464 if (!ns_capable(mnt_ns
->user_ns
, CAP_SYS_ADMIN
) ||
3465 !ns_capable(current_user_ns(), CAP_SYS_CHROOT
) ||
3466 !ns_capable(current_user_ns(), CAP_SYS_ADMIN
))
3473 old_mnt_ns
= nsproxy
->mnt_ns
;
3474 nsproxy
->mnt_ns
= mnt_ns
;
3477 err
= vfs_path_lookup(mnt_ns
->root
->mnt
.mnt_root
, &mnt_ns
->root
->mnt
,
3478 "/", LOOKUP_DOWN
, &root
);
3480 /* revert to old namespace */
3481 nsproxy
->mnt_ns
= old_mnt_ns
;
3486 put_mnt_ns(old_mnt_ns
);
3488 /* Update the pwd and root */
3489 set_fs_pwd(fs
, &root
);
3490 set_fs_root(fs
, &root
);
3496 static struct user_namespace
*mntns_owner(struct ns_common
*ns
)
3498 return to_mnt_ns(ns
)->user_ns
;
3501 const struct proc_ns_operations mntns_operations
= {
3503 .type
= CLONE_NEWNS
,
3506 .install
= mntns_install
,
3507 .owner
= mntns_owner
,