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/acct.h> /* acct_auto_close_mnt */
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>
30 static unsigned int m_hash_mask __read_mostly
;
31 static unsigned int m_hash_shift __read_mostly
;
32 static unsigned int mp_hash_mask __read_mostly
;
33 static unsigned int mp_hash_shift __read_mostly
;
35 static __initdata
unsigned long mhash_entries
;
36 static int __init
set_mhash_entries(char *str
)
40 mhash_entries
= simple_strtoul(str
, &str
, 0);
43 __setup("mhash_entries=", set_mhash_entries
);
45 static __initdata
unsigned long mphash_entries
;
46 static int __init
set_mphash_entries(char *str
)
50 mphash_entries
= simple_strtoul(str
, &str
, 0);
53 __setup("mphash_entries=", set_mphash_entries
);
56 static DEFINE_IDA(mnt_id_ida
);
57 static DEFINE_IDA(mnt_group_ida
);
58 static DEFINE_SPINLOCK(mnt_id_lock
);
59 static int mnt_id_start
= 0;
60 static int mnt_group_start
= 1;
62 static struct hlist_head
*mount_hashtable __read_mostly
;
63 static struct hlist_head
*mountpoint_hashtable __read_mostly
;
64 static struct kmem_cache
*mnt_cache __read_mostly
;
65 static DECLARE_RWSEM(namespace_sem
);
68 struct kobject
*fs_kobj
;
69 EXPORT_SYMBOL_GPL(fs_kobj
);
72 * vfsmount lock may be taken for read to prevent changes to the
73 * vfsmount hash, ie. during mountpoint lookups or walking back
76 * It should be taken for write in all cases where the vfsmount
77 * tree or hash is modified or when a vfsmount structure is modified.
79 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(mount_lock
);
81 static inline struct hlist_head
*m_hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
83 unsigned long tmp
= ((unsigned long)mnt
/ L1_CACHE_BYTES
);
84 tmp
+= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
85 tmp
= tmp
+ (tmp
>> m_hash_shift
);
86 return &mount_hashtable
[tmp
& m_hash_mask
];
89 static inline struct hlist_head
*mp_hash(struct dentry
*dentry
)
91 unsigned long tmp
= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
92 tmp
= tmp
+ (tmp
>> mp_hash_shift
);
93 return &mountpoint_hashtable
[tmp
& mp_hash_mask
];
97 * allocation is serialized by namespace_sem, but we need the spinlock to
98 * serialize with freeing.
100 static int mnt_alloc_id(struct mount
*mnt
)
105 ida_pre_get(&mnt_id_ida
, GFP_KERNEL
);
106 spin_lock(&mnt_id_lock
);
107 res
= ida_get_new_above(&mnt_id_ida
, mnt_id_start
, &mnt
->mnt_id
);
109 mnt_id_start
= mnt
->mnt_id
+ 1;
110 spin_unlock(&mnt_id_lock
);
117 static void mnt_free_id(struct mount
*mnt
)
119 int id
= mnt
->mnt_id
;
120 spin_lock(&mnt_id_lock
);
121 ida_remove(&mnt_id_ida
, id
);
122 if (mnt_id_start
> id
)
124 spin_unlock(&mnt_id_lock
);
128 * Allocate a new peer group ID
130 * mnt_group_ida is protected by namespace_sem
132 static int mnt_alloc_group_id(struct mount
*mnt
)
136 if (!ida_pre_get(&mnt_group_ida
, GFP_KERNEL
))
139 res
= ida_get_new_above(&mnt_group_ida
,
143 mnt_group_start
= mnt
->mnt_group_id
+ 1;
149 * Release a peer group ID
151 void mnt_release_group_id(struct mount
*mnt
)
153 int id
= mnt
->mnt_group_id
;
154 ida_remove(&mnt_group_ida
, id
);
155 if (mnt_group_start
> id
)
156 mnt_group_start
= id
;
157 mnt
->mnt_group_id
= 0;
161 * vfsmount lock must be held for read
163 static inline void mnt_add_count(struct mount
*mnt
, int n
)
166 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, n
);
175 * vfsmount lock must be held for write
177 unsigned int mnt_get_count(struct mount
*mnt
)
180 unsigned int count
= 0;
183 for_each_possible_cpu(cpu
) {
184 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_count
;
189 return mnt
->mnt_count
;
193 static struct mount
*alloc_vfsmnt(const char *name
)
195 struct mount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
199 err
= mnt_alloc_id(mnt
);
204 mnt
->mnt_devname
= kstrdup(name
, GFP_KERNEL
);
205 if (!mnt
->mnt_devname
)
210 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
212 goto out_free_devname
;
214 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
217 mnt
->mnt_writers
= 0;
220 INIT_HLIST_NODE(&mnt
->mnt_hash
);
221 INIT_LIST_HEAD(&mnt
->mnt_child
);
222 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
223 INIT_LIST_HEAD(&mnt
->mnt_list
);
224 INIT_LIST_HEAD(&mnt
->mnt_expire
);
225 INIT_LIST_HEAD(&mnt
->mnt_share
);
226 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
227 INIT_LIST_HEAD(&mnt
->mnt_slave
);
228 #ifdef CONFIG_FSNOTIFY
229 INIT_HLIST_HEAD(&mnt
->mnt_fsnotify_marks
);
236 kfree(mnt
->mnt_devname
);
241 kmem_cache_free(mnt_cache
, mnt
);
246 * Most r/o checks on a fs are for operations that take
247 * discrete amounts of time, like a write() or unlink().
248 * We must keep track of when those operations start
249 * (for permission checks) and when they end, so that
250 * we can determine when writes are able to occur to
254 * __mnt_is_readonly: check whether a mount is read-only
255 * @mnt: the mount to check for its write status
257 * This shouldn't be used directly ouside of the VFS.
258 * It does not guarantee that the filesystem will stay
259 * r/w, just that it is right *now*. This can not and
260 * should not be used in place of IS_RDONLY(inode).
261 * mnt_want/drop_write() will _keep_ the filesystem
264 int __mnt_is_readonly(struct vfsmount
*mnt
)
266 if (mnt
->mnt_flags
& MNT_READONLY
)
268 if (mnt
->mnt_sb
->s_flags
& MS_RDONLY
)
272 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
274 static inline void mnt_inc_writers(struct mount
*mnt
)
277 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
283 static inline void mnt_dec_writers(struct mount
*mnt
)
286 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
292 static unsigned int mnt_get_writers(struct mount
*mnt
)
295 unsigned int count
= 0;
298 for_each_possible_cpu(cpu
) {
299 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_writers
;
304 return mnt
->mnt_writers
;
308 static int mnt_is_readonly(struct vfsmount
*mnt
)
310 if (mnt
->mnt_sb
->s_readonly_remount
)
312 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
314 return __mnt_is_readonly(mnt
);
318 * Most r/o & frozen checks on a fs are for operations that take discrete
319 * amounts of time, like a write() or unlink(). We must keep track of when
320 * those operations start (for permission checks) and when they end, so that we
321 * can determine when writes are able to occur to a filesystem.
324 * __mnt_want_write - get write access to a mount without freeze protection
325 * @m: the mount on which to take a write
327 * This tells the low-level filesystem that a write is about to be performed to
328 * it, and makes sure that writes are allowed (mnt it read-write) before
329 * returning success. This operation does not protect against filesystem being
330 * frozen. When the write operation is finished, __mnt_drop_write() must be
331 * called. This is effectively a refcount.
333 int __mnt_want_write(struct vfsmount
*m
)
335 struct mount
*mnt
= real_mount(m
);
339 mnt_inc_writers(mnt
);
341 * The store to mnt_inc_writers must be visible before we pass
342 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
343 * incremented count after it has set MNT_WRITE_HOLD.
346 while (ACCESS_ONCE(mnt
->mnt
.mnt_flags
) & MNT_WRITE_HOLD
)
349 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
350 * be set to match its requirements. So we must not load that until
351 * MNT_WRITE_HOLD is cleared.
354 if (mnt_is_readonly(m
)) {
355 mnt_dec_writers(mnt
);
364 * mnt_want_write - get write access to a mount
365 * @m: the mount on which to take a write
367 * This tells the low-level filesystem that a write is about to be performed to
368 * it, and makes sure that writes are allowed (mount is read-write, filesystem
369 * is not frozen) before returning success. When the write operation is
370 * finished, mnt_drop_write() must be called. This is effectively a refcount.
372 int mnt_want_write(struct vfsmount
*m
)
376 sb_start_write(m
->mnt_sb
);
377 ret
= __mnt_want_write(m
);
379 sb_end_write(m
->mnt_sb
);
382 EXPORT_SYMBOL_GPL(mnt_want_write
);
385 * mnt_clone_write - get write access to a mount
386 * @mnt: the mount on which to take a write
388 * This is effectively like mnt_want_write, except
389 * it must only be used to take an extra write reference
390 * on a mountpoint that we already know has a write reference
391 * on it. This allows some optimisation.
393 * After finished, mnt_drop_write must be called as usual to
394 * drop the reference.
396 int mnt_clone_write(struct vfsmount
*mnt
)
398 /* superblock may be r/o */
399 if (__mnt_is_readonly(mnt
))
402 mnt_inc_writers(real_mount(mnt
));
406 EXPORT_SYMBOL_GPL(mnt_clone_write
);
409 * __mnt_want_write_file - get write access to a file's mount
410 * @file: the file who's mount on which to take a write
412 * This is like __mnt_want_write, but it takes a file and can
413 * do some optimisations if the file is open for write already
415 int __mnt_want_write_file(struct file
*file
)
417 if (!(file
->f_mode
& FMODE_WRITER
))
418 return __mnt_want_write(file
->f_path
.mnt
);
420 return mnt_clone_write(file
->f_path
.mnt
);
424 * mnt_want_write_file - get write access to a file's mount
425 * @file: the file who's mount on which to take a write
427 * This is like mnt_want_write, but it takes a file and can
428 * do some optimisations if the file is open for write already
430 int mnt_want_write_file(struct file
*file
)
434 sb_start_write(file
->f_path
.mnt
->mnt_sb
);
435 ret
= __mnt_want_write_file(file
);
437 sb_end_write(file
->f_path
.mnt
->mnt_sb
);
440 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
443 * __mnt_drop_write - give up write access to a mount
444 * @mnt: the mount on which to give up write access
446 * Tells the low-level filesystem that we are done
447 * performing writes to it. Must be matched with
448 * __mnt_want_write() call above.
450 void __mnt_drop_write(struct vfsmount
*mnt
)
453 mnt_dec_writers(real_mount(mnt
));
458 * mnt_drop_write - give up write access to a mount
459 * @mnt: the mount on which to give up write access
461 * Tells the low-level filesystem that we are done performing writes to it and
462 * also allows filesystem to be frozen again. Must be matched with
463 * mnt_want_write() call above.
465 void mnt_drop_write(struct vfsmount
*mnt
)
467 __mnt_drop_write(mnt
);
468 sb_end_write(mnt
->mnt_sb
);
470 EXPORT_SYMBOL_GPL(mnt_drop_write
);
472 void __mnt_drop_write_file(struct file
*file
)
474 __mnt_drop_write(file
->f_path
.mnt
);
477 void mnt_drop_write_file(struct file
*file
)
479 mnt_drop_write(file
->f_path
.mnt
);
481 EXPORT_SYMBOL(mnt_drop_write_file
);
483 static int mnt_make_readonly(struct mount
*mnt
)
488 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
490 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
491 * should be visible before we do.
496 * With writers on hold, if this value is zero, then there are
497 * definitely no active writers (although held writers may subsequently
498 * increment the count, they'll have to wait, and decrement it after
499 * seeing MNT_READONLY).
501 * It is OK to have counter incremented on one CPU and decremented on
502 * another: the sum will add up correctly. The danger would be when we
503 * sum up each counter, if we read a counter before it is incremented,
504 * but then read another CPU's count which it has been subsequently
505 * decremented from -- we would see more decrements than we should.
506 * MNT_WRITE_HOLD protects against this scenario, because
507 * mnt_want_write first increments count, then smp_mb, then spins on
508 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
509 * we're counting up here.
511 if (mnt_get_writers(mnt
) > 0)
514 mnt
->mnt
.mnt_flags
|= MNT_READONLY
;
516 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
517 * that become unheld will see MNT_READONLY.
520 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
525 static void __mnt_unmake_readonly(struct mount
*mnt
)
528 mnt
->mnt
.mnt_flags
&= ~MNT_READONLY
;
532 int sb_prepare_remount_readonly(struct super_block
*sb
)
537 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
538 if (atomic_long_read(&sb
->s_remove_count
))
542 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
543 if (!(mnt
->mnt
.mnt_flags
& MNT_READONLY
)) {
544 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
546 if (mnt_get_writers(mnt
) > 0) {
552 if (!err
&& atomic_long_read(&sb
->s_remove_count
))
556 sb
->s_readonly_remount
= 1;
559 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
560 if (mnt
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
561 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
568 static void free_vfsmnt(struct mount
*mnt
)
570 kfree(mnt
->mnt_devname
);
572 free_percpu(mnt
->mnt_pcp
);
574 kmem_cache_free(mnt_cache
, mnt
);
577 static void delayed_free_vfsmnt(struct rcu_head
*head
)
579 free_vfsmnt(container_of(head
, struct mount
, mnt_rcu
));
582 /* call under rcu_read_lock */
583 bool legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
586 if (read_seqretry(&mount_lock
, seq
))
590 mnt
= real_mount(bastard
);
591 mnt_add_count(mnt
, 1);
592 if (likely(!read_seqretry(&mount_lock
, seq
)))
594 if (bastard
->mnt_flags
& MNT_SYNC_UMOUNT
) {
595 mnt_add_count(mnt
, -1);
605 * find the first mount at @dentry on vfsmount @mnt.
606 * call under rcu_read_lock()
608 struct mount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
610 struct hlist_head
*head
= m_hash(mnt
, dentry
);
613 hlist_for_each_entry_rcu(p
, head
, mnt_hash
)
614 if (&p
->mnt_parent
->mnt
== mnt
&& p
->mnt_mountpoint
== dentry
)
620 * find the last mount at @dentry on vfsmount @mnt.
621 * mount_lock must be held.
623 struct mount
*__lookup_mnt_last(struct vfsmount
*mnt
, struct dentry
*dentry
)
625 struct mount
*p
, *res
;
626 res
= p
= __lookup_mnt(mnt
, dentry
);
629 hlist_for_each_entry_continue(p
, mnt_hash
) {
630 if (&p
->mnt_parent
->mnt
!= mnt
|| p
->mnt_mountpoint
!= dentry
)
639 * lookup_mnt - Return the first child mount mounted at path
641 * "First" means first mounted chronologically. If you create the
644 * mount /dev/sda1 /mnt
645 * mount /dev/sda2 /mnt
646 * mount /dev/sda3 /mnt
648 * Then lookup_mnt() on the base /mnt dentry in the root mount will
649 * return successively the root dentry and vfsmount of /dev/sda1, then
650 * /dev/sda2, then /dev/sda3, then NULL.
652 * lookup_mnt takes a reference to the found vfsmount.
654 struct vfsmount
*lookup_mnt(struct path
*path
)
656 struct mount
*child_mnt
;
662 seq
= read_seqbegin(&mount_lock
);
663 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
);
664 m
= child_mnt
? &child_mnt
->mnt
: NULL
;
665 } while (!legitimize_mnt(m
, seq
));
670 static struct mountpoint
*new_mountpoint(struct dentry
*dentry
)
672 struct hlist_head
*chain
= mp_hash(dentry
);
673 struct mountpoint
*mp
;
676 hlist_for_each_entry(mp
, chain
, m_hash
) {
677 if (mp
->m_dentry
== dentry
) {
678 /* might be worth a WARN_ON() */
679 if (d_unlinked(dentry
))
680 return ERR_PTR(-ENOENT
);
686 mp
= kmalloc(sizeof(struct mountpoint
), GFP_KERNEL
);
688 return ERR_PTR(-ENOMEM
);
690 ret
= d_set_mounted(dentry
);
696 mp
->m_dentry
= dentry
;
698 hlist_add_head(&mp
->m_hash
, chain
);
702 static void put_mountpoint(struct mountpoint
*mp
)
704 if (!--mp
->m_count
) {
705 struct dentry
*dentry
= mp
->m_dentry
;
706 spin_lock(&dentry
->d_lock
);
707 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
708 spin_unlock(&dentry
->d_lock
);
709 hlist_del(&mp
->m_hash
);
714 static inline int check_mnt(struct mount
*mnt
)
716 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
720 * vfsmount lock must be held for write
722 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
726 wake_up_interruptible(&ns
->poll
);
731 * vfsmount lock must be held for write
733 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
735 if (ns
&& ns
->event
!= event
) {
737 wake_up_interruptible(&ns
->poll
);
742 * vfsmount lock must be held for write
744 static void detach_mnt(struct mount
*mnt
, struct path
*old_path
)
746 old_path
->dentry
= mnt
->mnt_mountpoint
;
747 old_path
->mnt
= &mnt
->mnt_parent
->mnt
;
748 mnt
->mnt_parent
= mnt
;
749 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
750 list_del_init(&mnt
->mnt_child
);
751 hlist_del_init_rcu(&mnt
->mnt_hash
);
752 put_mountpoint(mnt
->mnt_mp
);
757 * vfsmount lock must be held for write
759 void mnt_set_mountpoint(struct mount
*mnt
,
760 struct mountpoint
*mp
,
761 struct mount
*child_mnt
)
764 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
765 child_mnt
->mnt_mountpoint
= dget(mp
->m_dentry
);
766 child_mnt
->mnt_parent
= mnt
;
767 child_mnt
->mnt_mp
= mp
;
771 * vfsmount lock must be held for write
773 static void attach_mnt(struct mount
*mnt
,
774 struct mount
*parent
,
775 struct mountpoint
*mp
)
777 mnt_set_mountpoint(parent
, mp
, mnt
);
778 hlist_add_head_rcu(&mnt
->mnt_hash
, m_hash(&parent
->mnt
, mp
->m_dentry
));
779 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
783 * vfsmount lock must be held for write
785 static void commit_tree(struct mount
*mnt
, struct mount
*shadows
)
787 struct mount
*parent
= mnt
->mnt_parent
;
790 struct mnt_namespace
*n
= parent
->mnt_ns
;
792 BUG_ON(parent
== mnt
);
794 list_add_tail(&head
, &mnt
->mnt_list
);
795 list_for_each_entry(m
, &head
, mnt_list
)
798 list_splice(&head
, n
->list
.prev
);
801 hlist_add_behind_rcu(&mnt
->mnt_hash
, &shadows
->mnt_hash
);
803 hlist_add_head_rcu(&mnt
->mnt_hash
,
804 m_hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
805 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
806 touch_mnt_namespace(n
);
809 static struct mount
*next_mnt(struct mount
*p
, struct mount
*root
)
811 struct list_head
*next
= p
->mnt_mounts
.next
;
812 if (next
== &p
->mnt_mounts
) {
816 next
= p
->mnt_child
.next
;
817 if (next
!= &p
->mnt_parent
->mnt_mounts
)
822 return list_entry(next
, struct mount
, mnt_child
);
825 static struct mount
*skip_mnt_tree(struct mount
*p
)
827 struct list_head
*prev
= p
->mnt_mounts
.prev
;
828 while (prev
!= &p
->mnt_mounts
) {
829 p
= list_entry(prev
, struct mount
, mnt_child
);
830 prev
= p
->mnt_mounts
.prev
;
836 vfs_kern_mount(struct file_system_type
*type
, int flags
, const char *name
, void *data
)
842 return ERR_PTR(-ENODEV
);
844 mnt
= alloc_vfsmnt(name
);
846 return ERR_PTR(-ENOMEM
);
848 if (flags
& MS_KERNMOUNT
)
849 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
851 root
= mount_fs(type
, flags
, name
, data
);
855 return ERR_CAST(root
);
858 mnt
->mnt
.mnt_root
= root
;
859 mnt
->mnt
.mnt_sb
= root
->d_sb
;
860 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
861 mnt
->mnt_parent
= mnt
;
863 list_add_tail(&mnt
->mnt_instance
, &root
->d_sb
->s_mounts
);
867 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
869 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
872 struct super_block
*sb
= old
->mnt
.mnt_sb
;
876 mnt
= alloc_vfsmnt(old
->mnt_devname
);
878 return ERR_PTR(-ENOMEM
);
880 if (flag
& (CL_SLAVE
| CL_PRIVATE
| CL_SHARED_TO_SLAVE
))
881 mnt
->mnt_group_id
= 0; /* not a peer of original */
883 mnt
->mnt_group_id
= old
->mnt_group_id
;
885 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
886 err
= mnt_alloc_group_id(mnt
);
891 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
& ~(MNT_WRITE_HOLD
|MNT_MARKED
);
892 /* Don't allow unprivileged users to change mount flags */
893 if (flag
& CL_UNPRIVILEGED
) {
894 mnt
->mnt
.mnt_flags
|= MNT_LOCK_ATIME
;
896 if (mnt
->mnt
.mnt_flags
& MNT_READONLY
)
897 mnt
->mnt
.mnt_flags
|= MNT_LOCK_READONLY
;
899 if (mnt
->mnt
.mnt_flags
& MNT_NODEV
)
900 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NODEV
;
902 if (mnt
->mnt
.mnt_flags
& MNT_NOSUID
)
903 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NOSUID
;
905 if (mnt
->mnt
.mnt_flags
& MNT_NOEXEC
)
906 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NOEXEC
;
909 /* Don't allow unprivileged users to reveal what is under a mount */
910 if ((flag
& CL_UNPRIVILEGED
) && list_empty(&old
->mnt_expire
))
911 mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
913 atomic_inc(&sb
->s_active
);
914 mnt
->mnt
.mnt_sb
= sb
;
915 mnt
->mnt
.mnt_root
= dget(root
);
916 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
917 mnt
->mnt_parent
= mnt
;
919 list_add_tail(&mnt
->mnt_instance
, &sb
->s_mounts
);
922 if ((flag
& CL_SLAVE
) ||
923 ((flag
& CL_SHARED_TO_SLAVE
) && IS_MNT_SHARED(old
))) {
924 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
925 mnt
->mnt_master
= old
;
926 CLEAR_MNT_SHARED(mnt
);
927 } else if (!(flag
& CL_PRIVATE
)) {
928 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
929 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
930 if (IS_MNT_SLAVE(old
))
931 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
932 mnt
->mnt_master
= old
->mnt_master
;
934 if (flag
& CL_MAKE_SHARED
)
937 /* stick the duplicate mount on the same expiry list
938 * as the original if that was on one */
939 if (flag
& CL_EXPIRE
) {
940 if (!list_empty(&old
->mnt_expire
))
941 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
952 static void mntput_no_expire(struct mount
*mnt
)
956 mnt_add_count(mnt
, -1);
957 if (likely(mnt
->mnt_ns
)) { /* shouldn't be the last one */
962 if (mnt_get_count(mnt
)) {
967 if (unlikely(mnt
->mnt_pinned
)) {
968 mnt_add_count(mnt
, mnt
->mnt_pinned
+ 1);
972 acct_auto_close_mnt(&mnt
->mnt
);
975 if (unlikely(mnt
->mnt
.mnt_flags
& MNT_DOOMED
)) {
980 mnt
->mnt
.mnt_flags
|= MNT_DOOMED
;
983 list_del(&mnt
->mnt_instance
);
987 * This probably indicates that somebody messed
988 * up a mnt_want/drop_write() pair. If this
989 * happens, the filesystem was probably unable
990 * to make r/w->r/o transitions.
993 * The locking used to deal with mnt_count decrement provides barriers,
994 * so mnt_get_writers() below is safe.
996 WARN_ON(mnt_get_writers(mnt
));
997 fsnotify_vfsmount_delete(&mnt
->mnt
);
998 dput(mnt
->mnt
.mnt_root
);
999 deactivate_super(mnt
->mnt
.mnt_sb
);
1001 call_rcu(&mnt
->mnt_rcu
, delayed_free_vfsmnt
);
1004 void mntput(struct vfsmount
*mnt
)
1007 struct mount
*m
= real_mount(mnt
);
1008 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1009 if (unlikely(m
->mnt_expiry_mark
))
1010 m
->mnt_expiry_mark
= 0;
1011 mntput_no_expire(m
);
1014 EXPORT_SYMBOL(mntput
);
1016 struct vfsmount
*mntget(struct vfsmount
*mnt
)
1019 mnt_add_count(real_mount(mnt
), 1);
1022 EXPORT_SYMBOL(mntget
);
1024 void mnt_pin(struct vfsmount
*mnt
)
1027 real_mount(mnt
)->mnt_pinned
++;
1028 unlock_mount_hash();
1030 EXPORT_SYMBOL(mnt_pin
);
1032 void mnt_unpin(struct vfsmount
*m
)
1034 struct mount
*mnt
= real_mount(m
);
1036 if (mnt
->mnt_pinned
) {
1037 mnt_add_count(mnt
, 1);
1040 unlock_mount_hash();
1042 EXPORT_SYMBOL(mnt_unpin
);
1044 static inline void mangle(struct seq_file
*m
, const char *s
)
1046 seq_escape(m
, s
, " \t\n\\");
1050 * Simple .show_options callback for filesystems which don't want to
1051 * implement more complex mount option showing.
1053 * See also save_mount_options().
1055 int generic_show_options(struct seq_file
*m
, struct dentry
*root
)
1057 const char *options
;
1060 options
= rcu_dereference(root
->d_sb
->s_options
);
1062 if (options
!= NULL
&& options
[0]) {
1070 EXPORT_SYMBOL(generic_show_options
);
1073 * If filesystem uses generic_show_options(), this function should be
1074 * called from the fill_super() callback.
1076 * The .remount_fs callback usually needs to be handled in a special
1077 * way, to make sure, that previous options are not overwritten if the
1080 * Also note, that if the filesystem's .remount_fs function doesn't
1081 * reset all options to their default value, but changes only newly
1082 * given options, then the displayed options will not reflect reality
1085 void save_mount_options(struct super_block
*sb
, char *options
)
1087 BUG_ON(sb
->s_options
);
1088 rcu_assign_pointer(sb
->s_options
, kstrdup(options
, GFP_KERNEL
));
1090 EXPORT_SYMBOL(save_mount_options
);
1092 void replace_mount_options(struct super_block
*sb
, char *options
)
1094 char *old
= sb
->s_options
;
1095 rcu_assign_pointer(sb
->s_options
, options
);
1101 EXPORT_SYMBOL(replace_mount_options
);
1103 #ifdef CONFIG_PROC_FS
1104 /* iterator; we want it to have access to namespace_sem, thus here... */
1105 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
1107 struct proc_mounts
*p
= proc_mounts(m
);
1109 down_read(&namespace_sem
);
1110 if (p
->cached_event
== p
->ns
->event
) {
1111 void *v
= p
->cached_mount
;
1112 if (*pos
== p
->cached_index
)
1114 if (*pos
== p
->cached_index
+ 1) {
1115 v
= seq_list_next(v
, &p
->ns
->list
, &p
->cached_index
);
1116 return p
->cached_mount
= v
;
1120 p
->cached_event
= p
->ns
->event
;
1121 p
->cached_mount
= seq_list_start(&p
->ns
->list
, *pos
);
1122 p
->cached_index
= *pos
;
1123 return p
->cached_mount
;
1126 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
1128 struct proc_mounts
*p
= proc_mounts(m
);
1130 p
->cached_mount
= seq_list_next(v
, &p
->ns
->list
, pos
);
1131 p
->cached_index
= *pos
;
1132 return p
->cached_mount
;
1135 static void m_stop(struct seq_file
*m
, void *v
)
1137 up_read(&namespace_sem
);
1140 static int m_show(struct seq_file
*m
, void *v
)
1142 struct proc_mounts
*p
= proc_mounts(m
);
1143 struct mount
*r
= list_entry(v
, struct mount
, mnt_list
);
1144 return p
->show(m
, &r
->mnt
);
1147 const struct seq_operations mounts_op
= {
1153 #endif /* CONFIG_PROC_FS */
1156 * may_umount_tree - check if a mount tree is busy
1157 * @mnt: root of mount tree
1159 * This is called to check if a tree of mounts has any
1160 * open files, pwds, chroots or sub mounts that are
1163 int may_umount_tree(struct vfsmount
*m
)
1165 struct mount
*mnt
= real_mount(m
);
1166 int actual_refs
= 0;
1167 int minimum_refs
= 0;
1171 /* write lock needed for mnt_get_count */
1173 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1174 actual_refs
+= mnt_get_count(p
);
1177 unlock_mount_hash();
1179 if (actual_refs
> minimum_refs
)
1185 EXPORT_SYMBOL(may_umount_tree
);
1188 * may_umount - check if a mount point is busy
1189 * @mnt: root of mount
1191 * This is called to check if a mount point has any
1192 * open files, pwds, chroots or sub mounts. If the
1193 * mount has sub mounts this will return busy
1194 * regardless of whether the sub mounts are busy.
1196 * Doesn't take quota and stuff into account. IOW, in some cases it will
1197 * give false negatives. The main reason why it's here is that we need
1198 * a non-destructive way to look for easily umountable filesystems.
1200 int may_umount(struct vfsmount
*mnt
)
1203 down_read(&namespace_sem
);
1205 if (propagate_mount_busy(real_mount(mnt
), 2))
1207 unlock_mount_hash();
1208 up_read(&namespace_sem
);
1212 EXPORT_SYMBOL(may_umount
);
1214 static HLIST_HEAD(unmounted
); /* protected by namespace_sem */
1216 static void namespace_unlock(void)
1219 struct hlist_head head
= unmounted
;
1221 if (likely(hlist_empty(&head
))) {
1222 up_write(&namespace_sem
);
1226 head
.first
->pprev
= &head
.first
;
1227 INIT_HLIST_HEAD(&unmounted
);
1229 up_write(&namespace_sem
);
1233 while (!hlist_empty(&head
)) {
1234 mnt
= hlist_entry(head
.first
, struct mount
, mnt_hash
);
1235 hlist_del_init(&mnt
->mnt_hash
);
1236 if (mnt
->mnt_ex_mountpoint
.mnt
)
1237 path_put(&mnt
->mnt_ex_mountpoint
);
1242 static inline void namespace_lock(void)
1244 down_write(&namespace_sem
);
1248 * mount_lock must be held
1249 * namespace_sem must be held for write
1250 * how = 0 => just this tree, don't propagate
1251 * how = 1 => propagate; we know that nobody else has reference to any victims
1252 * how = 2 => lazy umount
1254 void umount_tree(struct mount
*mnt
, int how
)
1256 HLIST_HEAD(tmp_list
);
1258 struct mount
*last
= NULL
;
1260 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1261 hlist_del_init_rcu(&p
->mnt_hash
);
1262 hlist_add_head(&p
->mnt_hash
, &tmp_list
);
1266 propagate_umount(&tmp_list
);
1268 hlist_for_each_entry(p
, &tmp_list
, mnt_hash
) {
1269 list_del_init(&p
->mnt_expire
);
1270 list_del_init(&p
->mnt_list
);
1271 __touch_mnt_namespace(p
->mnt_ns
);
1274 p
->mnt
.mnt_flags
|= MNT_SYNC_UMOUNT
;
1275 list_del_init(&p
->mnt_child
);
1276 if (mnt_has_parent(p
)) {
1277 put_mountpoint(p
->mnt_mp
);
1278 /* move the reference to mountpoint into ->mnt_ex_mountpoint */
1279 p
->mnt_ex_mountpoint
.dentry
= p
->mnt_mountpoint
;
1280 p
->mnt_ex_mountpoint
.mnt
= &p
->mnt_parent
->mnt
;
1281 p
->mnt_mountpoint
= p
->mnt
.mnt_root
;
1285 change_mnt_propagation(p
, MS_PRIVATE
);
1289 last
->mnt_hash
.next
= unmounted
.first
;
1290 unmounted
.first
= tmp_list
.first
;
1291 unmounted
.first
->pprev
= &unmounted
.first
;
1295 static void shrink_submounts(struct mount
*mnt
);
1297 static int do_umount(struct mount
*mnt
, int flags
)
1299 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1302 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1307 * Allow userspace to request a mountpoint be expired rather than
1308 * unmounting unconditionally. Unmount only happens if:
1309 * (1) the mark is already set (the mark is cleared by mntput())
1310 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1312 if (flags
& MNT_EXPIRE
) {
1313 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1314 flags
& (MNT_FORCE
| MNT_DETACH
))
1318 * probably don't strictly need the lock here if we examined
1319 * all race cases, but it's a slowpath.
1322 if (mnt_get_count(mnt
) != 2) {
1323 unlock_mount_hash();
1326 unlock_mount_hash();
1328 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1333 * If we may have to abort operations to get out of this
1334 * mount, and they will themselves hold resources we must
1335 * allow the fs to do things. In the Unix tradition of
1336 * 'Gee thats tricky lets do it in userspace' the umount_begin
1337 * might fail to complete on the first run through as other tasks
1338 * must return, and the like. Thats for the mount program to worry
1339 * about for the moment.
1342 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1343 sb
->s_op
->umount_begin(sb
);
1347 * No sense to grab the lock for this test, but test itself looks
1348 * somewhat bogus. Suggestions for better replacement?
1349 * Ho-hum... In principle, we might treat that as umount + switch
1350 * to rootfs. GC would eventually take care of the old vfsmount.
1351 * Actually it makes sense, especially if rootfs would contain a
1352 * /reboot - static binary that would close all descriptors and
1353 * call reboot(9). Then init(8) could umount root and exec /reboot.
1355 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1357 * Special case for "unmounting" root ...
1358 * we just try to remount it readonly.
1360 down_write(&sb
->s_umount
);
1361 if (!(sb
->s_flags
& MS_RDONLY
))
1362 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
1363 up_write(&sb
->s_umount
);
1371 if (flags
& MNT_DETACH
) {
1372 if (!list_empty(&mnt
->mnt_list
))
1373 umount_tree(mnt
, 2);
1376 shrink_submounts(mnt
);
1378 if (!propagate_mount_busy(mnt
, 2)) {
1379 if (!list_empty(&mnt
->mnt_list
))
1380 umount_tree(mnt
, 1);
1384 unlock_mount_hash();
1390 * Is the caller allowed to modify his namespace?
1392 static inline bool may_mount(void)
1394 return ns_capable(current
->nsproxy
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
);
1398 * Now umount can handle mount points as well as block devices.
1399 * This is important for filesystems which use unnamed block devices.
1401 * We now support a flag for forced unmount like the other 'big iron'
1402 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1405 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1410 int lookup_flags
= 0;
1412 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1418 if (!(flags
& UMOUNT_NOFOLLOW
))
1419 lookup_flags
|= LOOKUP_FOLLOW
;
1421 retval
= user_path_mountpoint_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1424 mnt
= real_mount(path
.mnt
);
1426 if (path
.dentry
!= path
.mnt
->mnt_root
)
1428 if (!check_mnt(mnt
))
1430 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
1433 retval
= do_umount(mnt
, flags
);
1435 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1437 mntput_no_expire(mnt
);
1442 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1445 * The 2.0 compatible umount. No flags.
1447 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1449 return sys_umount(name
, 0);
1454 static bool is_mnt_ns_file(struct dentry
*dentry
)
1456 /* Is this a proxy for a mount namespace? */
1457 struct inode
*inode
= dentry
->d_inode
;
1460 if (!proc_ns_inode(inode
))
1463 ei
= get_proc_ns(inode
);
1464 if (ei
->ns_ops
!= &mntns_operations
)
1470 static bool mnt_ns_loop(struct dentry
*dentry
)
1472 /* Could bind mounting the mount namespace inode cause a
1473 * mount namespace loop?
1475 struct mnt_namespace
*mnt_ns
;
1476 if (!is_mnt_ns_file(dentry
))
1479 mnt_ns
= get_proc_ns(dentry
->d_inode
)->ns
;
1480 return current
->nsproxy
->mnt_ns
->seq
>= mnt_ns
->seq
;
1483 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1486 struct mount
*res
, *p
, *q
, *r
, *parent
;
1488 if (!(flag
& CL_COPY_UNBINDABLE
) && IS_MNT_UNBINDABLE(mnt
))
1489 return ERR_PTR(-EINVAL
);
1491 if (!(flag
& CL_COPY_MNT_NS_FILE
) && is_mnt_ns_file(dentry
))
1492 return ERR_PTR(-EINVAL
);
1494 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1498 q
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
1499 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1502 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1504 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1507 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1508 if (!(flag
& CL_COPY_UNBINDABLE
) &&
1509 IS_MNT_UNBINDABLE(s
)) {
1510 s
= skip_mnt_tree(s
);
1513 if (!(flag
& CL_COPY_MNT_NS_FILE
) &&
1514 is_mnt_ns_file(s
->mnt
.mnt_root
)) {
1515 s
= skip_mnt_tree(s
);
1518 while (p
!= s
->mnt_parent
) {
1524 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
1528 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1529 attach_mnt(q
, parent
, p
->mnt_mp
);
1530 unlock_mount_hash();
1537 umount_tree(res
, 0);
1538 unlock_mount_hash();
1543 /* Caller should check returned pointer for errors */
1545 struct vfsmount
*collect_mounts(struct path
*path
)
1549 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
1550 CL_COPY_ALL
| CL_PRIVATE
);
1553 return ERR_CAST(tree
);
1557 void drop_collected_mounts(struct vfsmount
*mnt
)
1561 umount_tree(real_mount(mnt
), 0);
1562 unlock_mount_hash();
1566 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1567 struct vfsmount
*root
)
1570 int res
= f(root
, arg
);
1573 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
1574 res
= f(&mnt
->mnt
, arg
);
1581 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
1585 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
1586 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
1587 mnt_release_group_id(p
);
1591 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
1595 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
1596 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
1597 int err
= mnt_alloc_group_id(p
);
1599 cleanup_group_ids(mnt
, p
);
1609 * @source_mnt : mount tree to be attached
1610 * @nd : place the mount tree @source_mnt is attached
1611 * @parent_nd : if non-null, detach the source_mnt from its parent and
1612 * store the parent mount and mountpoint dentry.
1613 * (done when source_mnt is moved)
1615 * NOTE: in the table below explains the semantics when a source mount
1616 * of a given type is attached to a destination mount of a given type.
1617 * ---------------------------------------------------------------------------
1618 * | BIND MOUNT OPERATION |
1619 * |**************************************************************************
1620 * | source-->| shared | private | slave | unbindable |
1624 * |**************************************************************************
1625 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1627 * |non-shared| shared (+) | private | slave (*) | invalid |
1628 * ***************************************************************************
1629 * A bind operation clones the source mount and mounts the clone on the
1630 * destination mount.
1632 * (++) the cloned mount is propagated to all the mounts in the propagation
1633 * tree of the destination mount and the cloned mount is added to
1634 * the peer group of the source mount.
1635 * (+) the cloned mount is created under the destination mount and is marked
1636 * as shared. The cloned mount is added to the peer group of the source
1638 * (+++) the mount is propagated to all the mounts in the propagation tree
1639 * of the destination mount and the cloned mount is made slave
1640 * of the same master as that of the source mount. The cloned mount
1641 * is marked as 'shared and slave'.
1642 * (*) the cloned mount is made a slave of the same master as that of the
1645 * ---------------------------------------------------------------------------
1646 * | MOVE MOUNT OPERATION |
1647 * |**************************************************************************
1648 * | source-->| shared | private | slave | unbindable |
1652 * |**************************************************************************
1653 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1655 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1656 * ***************************************************************************
1658 * (+) the mount is moved to the destination. And is then propagated to
1659 * all the mounts in the propagation tree of the destination mount.
1660 * (+*) the mount is moved to the destination.
1661 * (+++) the mount is moved to the destination and is then propagated to
1662 * all the mounts belonging to the destination mount's propagation tree.
1663 * the mount is marked as 'shared and slave'.
1664 * (*) the mount continues to be a slave at the new location.
1666 * if the source mount is a tree, the operations explained above is
1667 * applied to each mount in the tree.
1668 * Must be called without spinlocks held, since this function can sleep
1671 static int attach_recursive_mnt(struct mount
*source_mnt
,
1672 struct mount
*dest_mnt
,
1673 struct mountpoint
*dest_mp
,
1674 struct path
*parent_path
)
1676 HLIST_HEAD(tree_list
);
1677 struct mount
*child
, *p
;
1678 struct hlist_node
*n
;
1681 if (IS_MNT_SHARED(dest_mnt
)) {
1682 err
= invent_group_ids(source_mnt
, true);
1685 err
= propagate_mnt(dest_mnt
, dest_mp
, source_mnt
, &tree_list
);
1688 goto out_cleanup_ids
;
1689 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
1695 detach_mnt(source_mnt
, parent_path
);
1696 attach_mnt(source_mnt
, dest_mnt
, dest_mp
);
1697 touch_mnt_namespace(source_mnt
->mnt_ns
);
1699 mnt_set_mountpoint(dest_mnt
, dest_mp
, source_mnt
);
1700 commit_tree(source_mnt
, NULL
);
1703 hlist_for_each_entry_safe(child
, n
, &tree_list
, mnt_hash
) {
1705 hlist_del_init(&child
->mnt_hash
);
1706 q
= __lookup_mnt_last(&child
->mnt_parent
->mnt
,
1707 child
->mnt_mountpoint
);
1708 commit_tree(child
, q
);
1710 unlock_mount_hash();
1715 while (!hlist_empty(&tree_list
)) {
1716 child
= hlist_entry(tree_list
.first
, struct mount
, mnt_hash
);
1717 umount_tree(child
, 0);
1719 unlock_mount_hash();
1720 cleanup_group_ids(source_mnt
, NULL
);
1725 static struct mountpoint
*lock_mount(struct path
*path
)
1727 struct vfsmount
*mnt
;
1728 struct dentry
*dentry
= path
->dentry
;
1730 mutex_lock(&dentry
->d_inode
->i_mutex
);
1731 if (unlikely(cant_mount(dentry
))) {
1732 mutex_unlock(&dentry
->d_inode
->i_mutex
);
1733 return ERR_PTR(-ENOENT
);
1736 mnt
= lookup_mnt(path
);
1738 struct mountpoint
*mp
= new_mountpoint(dentry
);
1741 mutex_unlock(&dentry
->d_inode
->i_mutex
);
1747 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1750 dentry
= path
->dentry
= dget(mnt
->mnt_root
);
1754 static void unlock_mount(struct mountpoint
*where
)
1756 struct dentry
*dentry
= where
->m_dentry
;
1757 put_mountpoint(where
);
1759 mutex_unlock(&dentry
->d_inode
->i_mutex
);
1762 static int graft_tree(struct mount
*mnt
, struct mount
*p
, struct mountpoint
*mp
)
1764 if (mnt
->mnt
.mnt_sb
->s_flags
& MS_NOUSER
)
1767 if (S_ISDIR(mp
->m_dentry
->d_inode
->i_mode
) !=
1768 S_ISDIR(mnt
->mnt
.mnt_root
->d_inode
->i_mode
))
1771 return attach_recursive_mnt(mnt
, p
, mp
, NULL
);
1775 * Sanity check the flags to change_mnt_propagation.
1778 static int flags_to_propagation_type(int flags
)
1780 int type
= flags
& ~(MS_REC
| MS_SILENT
);
1782 /* Fail if any non-propagation flags are set */
1783 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
1785 /* Only one propagation flag should be set */
1786 if (!is_power_of_2(type
))
1792 * recursively change the type of the mountpoint.
1794 static int do_change_type(struct path
*path
, int flag
)
1797 struct mount
*mnt
= real_mount(path
->mnt
);
1798 int recurse
= flag
& MS_REC
;
1802 if (path
->dentry
!= path
->mnt
->mnt_root
)
1805 type
= flags_to_propagation_type(flag
);
1810 if (type
== MS_SHARED
) {
1811 err
= invent_group_ids(mnt
, recurse
);
1817 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
1818 change_mnt_propagation(m
, type
);
1819 unlock_mount_hash();
1826 static bool has_locked_children(struct mount
*mnt
, struct dentry
*dentry
)
1828 struct mount
*child
;
1829 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
1830 if (!is_subdir(child
->mnt_mountpoint
, dentry
))
1833 if (child
->mnt
.mnt_flags
& MNT_LOCKED
)
1840 * do loopback mount.
1842 static int do_loopback(struct path
*path
, const char *old_name
,
1845 struct path old_path
;
1846 struct mount
*mnt
= NULL
, *old
, *parent
;
1847 struct mountpoint
*mp
;
1849 if (!old_name
|| !*old_name
)
1851 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
1856 if (mnt_ns_loop(old_path
.dentry
))
1859 mp
= lock_mount(path
);
1864 old
= real_mount(old_path
.mnt
);
1865 parent
= real_mount(path
->mnt
);
1868 if (IS_MNT_UNBINDABLE(old
))
1871 if (!check_mnt(parent
) || !check_mnt(old
))
1874 if (!recurse
&& has_locked_children(old
, old_path
.dentry
))
1878 mnt
= copy_tree(old
, old_path
.dentry
, CL_COPY_MNT_NS_FILE
);
1880 mnt
= clone_mnt(old
, old_path
.dentry
, 0);
1887 mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
1889 err
= graft_tree(mnt
, parent
, mp
);
1892 umount_tree(mnt
, 0);
1893 unlock_mount_hash();
1898 path_put(&old_path
);
1902 static int change_mount_flags(struct vfsmount
*mnt
, int ms_flags
)
1905 int readonly_request
= 0;
1907 if (ms_flags
& MS_RDONLY
)
1908 readonly_request
= 1;
1909 if (readonly_request
== __mnt_is_readonly(mnt
))
1912 if (readonly_request
)
1913 error
= mnt_make_readonly(real_mount(mnt
));
1915 __mnt_unmake_readonly(real_mount(mnt
));
1920 * change filesystem flags. dir should be a physical root of filesystem.
1921 * If you've mounted a non-root directory somewhere and want to do remount
1922 * on it - tough luck.
1924 static int do_remount(struct path
*path
, int flags
, int mnt_flags
,
1928 struct super_block
*sb
= path
->mnt
->mnt_sb
;
1929 struct mount
*mnt
= real_mount(path
->mnt
);
1931 if (!check_mnt(mnt
))
1934 if (path
->dentry
!= path
->mnt
->mnt_root
)
1937 /* Don't allow changing of locked mnt flags.
1939 * No locks need to be held here while testing the various
1940 * MNT_LOCK flags because those flags can never be cleared
1941 * once they are set.
1943 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_READONLY
) &&
1944 !(mnt_flags
& MNT_READONLY
)) {
1947 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NODEV
) &&
1948 !(mnt_flags
& MNT_NODEV
)) {
1951 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NOSUID
) &&
1952 !(mnt_flags
& MNT_NOSUID
)) {
1955 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NOEXEC
) &&
1956 !(mnt_flags
& MNT_NOEXEC
)) {
1959 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_ATIME
) &&
1960 ((mnt
->mnt
.mnt_flags
& MNT_ATIME_MASK
) != (mnt_flags
& MNT_ATIME_MASK
))) {
1964 err
= security_sb_remount(sb
, data
);
1968 down_write(&sb
->s_umount
);
1969 if (flags
& MS_BIND
)
1970 err
= change_mount_flags(path
->mnt
, flags
);
1971 else if (!capable(CAP_SYS_ADMIN
))
1974 err
= do_remount_sb(sb
, flags
, data
, 0);
1977 mnt_flags
|= mnt
->mnt
.mnt_flags
& ~MNT_USER_SETTABLE_MASK
;
1978 mnt
->mnt
.mnt_flags
= mnt_flags
;
1979 touch_mnt_namespace(mnt
->mnt_ns
);
1980 unlock_mount_hash();
1982 up_write(&sb
->s_umount
);
1986 static inline int tree_contains_unbindable(struct mount
*mnt
)
1989 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1990 if (IS_MNT_UNBINDABLE(p
))
1996 static int do_move_mount(struct path
*path
, const char *old_name
)
1998 struct path old_path
, parent_path
;
2001 struct mountpoint
*mp
;
2003 if (!old_name
|| !*old_name
)
2005 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
2009 mp
= lock_mount(path
);
2014 old
= real_mount(old_path
.mnt
);
2015 p
= real_mount(path
->mnt
);
2018 if (!check_mnt(p
) || !check_mnt(old
))
2021 if (old
->mnt
.mnt_flags
& MNT_LOCKED
)
2025 if (old_path
.dentry
!= old_path
.mnt
->mnt_root
)
2028 if (!mnt_has_parent(old
))
2031 if (S_ISDIR(path
->dentry
->d_inode
->i_mode
) !=
2032 S_ISDIR(old_path
.dentry
->d_inode
->i_mode
))
2035 * Don't move a mount residing in a shared parent.
2037 if (IS_MNT_SHARED(old
->mnt_parent
))
2040 * Don't move a mount tree containing unbindable mounts to a destination
2041 * mount which is shared.
2043 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
2046 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
2050 err
= attach_recursive_mnt(old
, real_mount(path
->mnt
), mp
, &parent_path
);
2054 /* if the mount is moved, it should no longer be expire
2056 list_del_init(&old
->mnt_expire
);
2061 path_put(&parent_path
);
2062 path_put(&old_path
);
2066 static struct vfsmount
*fs_set_subtype(struct vfsmount
*mnt
, const char *fstype
)
2069 const char *subtype
= strchr(fstype
, '.');
2078 mnt
->mnt_sb
->s_subtype
= kstrdup(subtype
, GFP_KERNEL
);
2080 if (!mnt
->mnt_sb
->s_subtype
)
2086 return ERR_PTR(err
);
2090 * add a mount into a namespace's mount tree
2092 static int do_add_mount(struct mount
*newmnt
, struct path
*path
, int mnt_flags
)
2094 struct mountpoint
*mp
;
2095 struct mount
*parent
;
2098 mnt_flags
&= ~MNT_INTERNAL_FLAGS
;
2100 mp
= lock_mount(path
);
2104 parent
= real_mount(path
->mnt
);
2106 if (unlikely(!check_mnt(parent
))) {
2107 /* that's acceptable only for automounts done in private ns */
2108 if (!(mnt_flags
& MNT_SHRINKABLE
))
2110 /* ... and for those we'd better have mountpoint still alive */
2111 if (!parent
->mnt_ns
)
2115 /* Refuse the same filesystem on the same mount point */
2117 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
2118 path
->mnt
->mnt_root
== path
->dentry
)
2122 if (S_ISLNK(newmnt
->mnt
.mnt_root
->d_inode
->i_mode
))
2125 newmnt
->mnt
.mnt_flags
= mnt_flags
;
2126 err
= graft_tree(newmnt
, parent
, mp
);
2134 * create a new mount for userspace and request it to be added into the
2137 static int do_new_mount(struct path
*path
, const char *fstype
, int flags
,
2138 int mnt_flags
, const char *name
, void *data
)
2140 struct file_system_type
*type
;
2141 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2142 struct vfsmount
*mnt
;
2148 type
= get_fs_type(fstype
);
2152 if (user_ns
!= &init_user_ns
) {
2153 if (!(type
->fs_flags
& FS_USERNS_MOUNT
)) {
2154 put_filesystem(type
);
2157 /* Only in special cases allow devices from mounts
2158 * created outside the initial user namespace.
2160 if (!(type
->fs_flags
& FS_USERNS_DEV_MOUNT
)) {
2162 mnt_flags
|= MNT_NODEV
| MNT_LOCK_NODEV
;
2166 mnt
= vfs_kern_mount(type
, flags
, name
, data
);
2167 if (!IS_ERR(mnt
) && (type
->fs_flags
& FS_HAS_SUBTYPE
) &&
2168 !mnt
->mnt_sb
->s_subtype
)
2169 mnt
= fs_set_subtype(mnt
, fstype
);
2171 put_filesystem(type
);
2173 return PTR_ERR(mnt
);
2175 err
= do_add_mount(real_mount(mnt
), path
, mnt_flags
);
2181 int finish_automount(struct vfsmount
*m
, struct path
*path
)
2183 struct mount
*mnt
= real_mount(m
);
2185 /* The new mount record should have at least 2 refs to prevent it being
2186 * expired before we get a chance to add it
2188 BUG_ON(mnt_get_count(mnt
) < 2);
2190 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
2191 m
->mnt_root
== path
->dentry
) {
2196 err
= do_add_mount(mnt
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
2200 /* remove m from any expiration list it may be on */
2201 if (!list_empty(&mnt
->mnt_expire
)) {
2203 list_del_init(&mnt
->mnt_expire
);
2212 * mnt_set_expiry - Put a mount on an expiration list
2213 * @mnt: The mount to list.
2214 * @expiry_list: The list to add the mount to.
2216 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
2220 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
2224 EXPORT_SYMBOL(mnt_set_expiry
);
2227 * process a list of expirable mountpoints with the intent of discarding any
2228 * mountpoints that aren't in use and haven't been touched since last we came
2231 void mark_mounts_for_expiry(struct list_head
*mounts
)
2233 struct mount
*mnt
, *next
;
2234 LIST_HEAD(graveyard
);
2236 if (list_empty(mounts
))
2242 /* extract from the expiration list every vfsmount that matches the
2243 * following criteria:
2244 * - only referenced by its parent vfsmount
2245 * - still marked for expiry (marked on the last call here; marks are
2246 * cleared by mntput())
2248 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
2249 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
2250 propagate_mount_busy(mnt
, 1))
2252 list_move(&mnt
->mnt_expire
, &graveyard
);
2254 while (!list_empty(&graveyard
)) {
2255 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
2256 touch_mnt_namespace(mnt
->mnt_ns
);
2257 umount_tree(mnt
, 1);
2259 unlock_mount_hash();
2263 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
2266 * Ripoff of 'select_parent()'
2268 * search the list of submounts for a given mountpoint, and move any
2269 * shrinkable submounts to the 'graveyard' list.
2271 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
2273 struct mount
*this_parent
= parent
;
2274 struct list_head
*next
;
2278 next
= this_parent
->mnt_mounts
.next
;
2280 while (next
!= &this_parent
->mnt_mounts
) {
2281 struct list_head
*tmp
= next
;
2282 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
2285 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
2288 * Descend a level if the d_mounts list is non-empty.
2290 if (!list_empty(&mnt
->mnt_mounts
)) {
2295 if (!propagate_mount_busy(mnt
, 1)) {
2296 list_move_tail(&mnt
->mnt_expire
, graveyard
);
2301 * All done at this level ... ascend and resume the search
2303 if (this_parent
!= parent
) {
2304 next
= this_parent
->mnt_child
.next
;
2305 this_parent
= this_parent
->mnt_parent
;
2312 * process a list of expirable mountpoints with the intent of discarding any
2313 * submounts of a specific parent mountpoint
2315 * mount_lock must be held for write
2317 static void shrink_submounts(struct mount
*mnt
)
2319 LIST_HEAD(graveyard
);
2322 /* extract submounts of 'mountpoint' from the expiration list */
2323 while (select_submounts(mnt
, &graveyard
)) {
2324 while (!list_empty(&graveyard
)) {
2325 m
= list_first_entry(&graveyard
, struct mount
,
2327 touch_mnt_namespace(m
->mnt_ns
);
2334 * Some copy_from_user() implementations do not return the exact number of
2335 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2336 * Note that this function differs from copy_from_user() in that it will oops
2337 * on bad values of `to', rather than returning a short copy.
2339 static long exact_copy_from_user(void *to
, const void __user
* from
,
2343 const char __user
*f
= from
;
2346 if (!access_ok(VERIFY_READ
, from
, n
))
2350 if (__get_user(c
, f
)) {
2361 int copy_mount_options(const void __user
* data
, unsigned long *where
)
2371 if (!(page
= __get_free_page(GFP_KERNEL
)))
2374 /* We only care that *some* data at the address the user
2375 * gave us is valid. Just in case, we'll zero
2376 * the remainder of the page.
2378 /* copy_from_user cannot cross TASK_SIZE ! */
2379 size
= TASK_SIZE
- (unsigned long)data
;
2380 if (size
> PAGE_SIZE
)
2383 i
= size
- exact_copy_from_user((void *)page
, data
, size
);
2389 memset((char *)page
+ i
, 0, PAGE_SIZE
- i
);
2394 int copy_mount_string(const void __user
*data
, char **where
)
2403 tmp
= strndup_user(data
, PAGE_SIZE
);
2405 return PTR_ERR(tmp
);
2412 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2413 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2415 * data is a (void *) that can point to any structure up to
2416 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2417 * information (or be NULL).
2419 * Pre-0.97 versions of mount() didn't have a flags word.
2420 * When the flags word was introduced its top half was required
2421 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2422 * Therefore, if this magic number is present, it carries no information
2423 * and must be discarded.
2425 long do_mount(const char *dev_name
, const char *dir_name
,
2426 const char *type_page
, unsigned long flags
, void *data_page
)
2433 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
2434 flags
&= ~MS_MGC_MSK
;
2436 /* Basic sanity checks */
2438 if (!dir_name
|| !*dir_name
|| !memchr(dir_name
, 0, PAGE_SIZE
))
2442 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
2444 /* ... and get the mountpoint */
2445 retval
= kern_path(dir_name
, LOOKUP_FOLLOW
, &path
);
2449 retval
= security_sb_mount(dev_name
, &path
,
2450 type_page
, flags
, data_page
);
2451 if (!retval
&& !may_mount())
2456 /* Default to relatime unless overriden */
2457 if (!(flags
& MS_NOATIME
))
2458 mnt_flags
|= MNT_RELATIME
;
2460 /* Separate the per-mountpoint flags */
2461 if (flags
& MS_NOSUID
)
2462 mnt_flags
|= MNT_NOSUID
;
2463 if (flags
& MS_NODEV
)
2464 mnt_flags
|= MNT_NODEV
;
2465 if (flags
& MS_NOEXEC
)
2466 mnt_flags
|= MNT_NOEXEC
;
2467 if (flags
& MS_NOATIME
)
2468 mnt_flags
|= MNT_NOATIME
;
2469 if (flags
& MS_NODIRATIME
)
2470 mnt_flags
|= MNT_NODIRATIME
;
2471 if (flags
& MS_STRICTATIME
)
2472 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
2473 if (flags
& MS_RDONLY
)
2474 mnt_flags
|= MNT_READONLY
;
2476 /* The default atime for remount is preservation */
2477 if ((flags
& MS_REMOUNT
) &&
2478 ((flags
& (MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
|
2479 MS_STRICTATIME
)) == 0)) {
2480 mnt_flags
&= ~MNT_ATIME_MASK
;
2481 mnt_flags
|= path
.mnt
->mnt_flags
& MNT_ATIME_MASK
;
2484 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
| MS_BORN
|
2485 MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
| MS_KERNMOUNT
|
2488 if (flags
& MS_REMOUNT
)
2489 retval
= do_remount(&path
, flags
& ~MS_REMOUNT
, mnt_flags
,
2491 else if (flags
& MS_BIND
)
2492 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
2493 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2494 retval
= do_change_type(&path
, flags
);
2495 else if (flags
& MS_MOVE
)
2496 retval
= do_move_mount(&path
, dev_name
);
2498 retval
= do_new_mount(&path
, type_page
, flags
, mnt_flags
,
2499 dev_name
, data_page
);
2505 static void free_mnt_ns(struct mnt_namespace
*ns
)
2507 proc_free_inum(ns
->proc_inum
);
2508 put_user_ns(ns
->user_ns
);
2513 * Assign a sequence number so we can detect when we attempt to bind
2514 * mount a reference to an older mount namespace into the current
2515 * mount namespace, preventing reference counting loops. A 64bit
2516 * number incrementing at 10Ghz will take 12,427 years to wrap which
2517 * is effectively never, so we can ignore the possibility.
2519 static atomic64_t mnt_ns_seq
= ATOMIC64_INIT(1);
2521 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*user_ns
)
2523 struct mnt_namespace
*new_ns
;
2526 new_ns
= kmalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
2528 return ERR_PTR(-ENOMEM
);
2529 ret
= proc_alloc_inum(&new_ns
->proc_inum
);
2532 return ERR_PTR(ret
);
2534 new_ns
->seq
= atomic64_add_return(1, &mnt_ns_seq
);
2535 atomic_set(&new_ns
->count
, 1);
2536 new_ns
->root
= NULL
;
2537 INIT_LIST_HEAD(&new_ns
->list
);
2538 init_waitqueue_head(&new_ns
->poll
);
2540 new_ns
->user_ns
= get_user_ns(user_ns
);
2544 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
2545 struct user_namespace
*user_ns
, struct fs_struct
*new_fs
)
2547 struct mnt_namespace
*new_ns
;
2548 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
2549 struct mount
*p
, *q
;
2556 if (likely(!(flags
& CLONE_NEWNS
))) {
2563 new_ns
= alloc_mnt_ns(user_ns
);
2568 /* First pass: copy the tree topology */
2569 copy_flags
= CL_COPY_UNBINDABLE
| CL_EXPIRE
;
2570 if (user_ns
!= ns
->user_ns
)
2571 copy_flags
|= CL_SHARED_TO_SLAVE
| CL_UNPRIVILEGED
;
2572 new = copy_tree(old
, old
->mnt
.mnt_root
, copy_flags
);
2575 free_mnt_ns(new_ns
);
2576 return ERR_CAST(new);
2579 list_add_tail(&new_ns
->list
, &new->mnt_list
);
2582 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2583 * as belonging to new namespace. We have already acquired a private
2584 * fs_struct, so tsk->fs->lock is not needed.
2591 if (&p
->mnt
== new_fs
->root
.mnt
) {
2592 new_fs
->root
.mnt
= mntget(&q
->mnt
);
2595 if (&p
->mnt
== new_fs
->pwd
.mnt
) {
2596 new_fs
->pwd
.mnt
= mntget(&q
->mnt
);
2600 p
= next_mnt(p
, old
);
2601 q
= next_mnt(q
, new);
2604 while (p
->mnt
.mnt_root
!= q
->mnt
.mnt_root
)
2605 p
= next_mnt(p
, old
);
2618 * create_mnt_ns - creates a private namespace and adds a root filesystem
2619 * @mnt: pointer to the new root filesystem mountpoint
2621 static struct mnt_namespace
*create_mnt_ns(struct vfsmount
*m
)
2623 struct mnt_namespace
*new_ns
= alloc_mnt_ns(&init_user_ns
);
2624 if (!IS_ERR(new_ns
)) {
2625 struct mount
*mnt
= real_mount(m
);
2626 mnt
->mnt_ns
= new_ns
;
2628 list_add(&mnt
->mnt_list
, &new_ns
->list
);
2635 struct dentry
*mount_subtree(struct vfsmount
*mnt
, const char *name
)
2637 struct mnt_namespace
*ns
;
2638 struct super_block
*s
;
2642 ns
= create_mnt_ns(mnt
);
2644 return ERR_CAST(ns
);
2646 err
= vfs_path_lookup(mnt
->mnt_root
, mnt
,
2647 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
2652 return ERR_PTR(err
);
2654 /* trade a vfsmount reference for active sb one */
2655 s
= path
.mnt
->mnt_sb
;
2656 atomic_inc(&s
->s_active
);
2658 /* lock the sucker */
2659 down_write(&s
->s_umount
);
2660 /* ... and return the root of (sub)tree on it */
2663 EXPORT_SYMBOL(mount_subtree
);
2665 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
2666 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
2670 struct filename
*kernel_dir
;
2672 unsigned long data_page
;
2674 ret
= copy_mount_string(type
, &kernel_type
);
2678 kernel_dir
= getname(dir_name
);
2679 if (IS_ERR(kernel_dir
)) {
2680 ret
= PTR_ERR(kernel_dir
);
2684 ret
= copy_mount_string(dev_name
, &kernel_dev
);
2688 ret
= copy_mount_options(data
, &data_page
);
2692 ret
= do_mount(kernel_dev
, kernel_dir
->name
, kernel_type
, flags
,
2693 (void *) data_page
);
2695 free_page(data_page
);
2699 putname(kernel_dir
);
2707 * Return true if path is reachable from root
2709 * namespace_sem or mount_lock is held
2711 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
2712 const struct path
*root
)
2714 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
2715 dentry
= mnt
->mnt_mountpoint
;
2716 mnt
= mnt
->mnt_parent
;
2718 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
2721 int path_is_under(struct path
*path1
, struct path
*path2
)
2724 read_seqlock_excl(&mount_lock
);
2725 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
2726 read_sequnlock_excl(&mount_lock
);
2729 EXPORT_SYMBOL(path_is_under
);
2732 * pivot_root Semantics:
2733 * Moves the root file system of the current process to the directory put_old,
2734 * makes new_root as the new root file system of the current process, and sets
2735 * root/cwd of all processes which had them on the current root to new_root.
2738 * The new_root and put_old must be directories, and must not be on the
2739 * same file system as the current process root. The put_old must be
2740 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2741 * pointed to by put_old must yield the same directory as new_root. No other
2742 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2744 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2745 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2746 * in this situation.
2749 * - we don't move root/cwd if they are not at the root (reason: if something
2750 * cared enough to change them, it's probably wrong to force them elsewhere)
2751 * - it's okay to pick a root that isn't the root of a file system, e.g.
2752 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2753 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2756 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
2757 const char __user
*, put_old
)
2759 struct path
new, old
, parent_path
, root_parent
, root
;
2760 struct mount
*new_mnt
, *root_mnt
, *old_mnt
;
2761 struct mountpoint
*old_mp
, *root_mp
;
2767 error
= user_path_dir(new_root
, &new);
2771 error
= user_path_dir(put_old
, &old
);
2775 error
= security_sb_pivotroot(&old
, &new);
2779 get_fs_root(current
->fs
, &root
);
2780 old_mp
= lock_mount(&old
);
2781 error
= PTR_ERR(old_mp
);
2786 new_mnt
= real_mount(new.mnt
);
2787 root_mnt
= real_mount(root
.mnt
);
2788 old_mnt
= real_mount(old
.mnt
);
2789 if (IS_MNT_SHARED(old_mnt
) ||
2790 IS_MNT_SHARED(new_mnt
->mnt_parent
) ||
2791 IS_MNT_SHARED(root_mnt
->mnt_parent
))
2793 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
2795 if (new_mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
2798 if (d_unlinked(new.dentry
))
2801 if (new_mnt
== root_mnt
|| old_mnt
== root_mnt
)
2802 goto out4
; /* loop, on the same file system */
2804 if (root
.mnt
->mnt_root
!= root
.dentry
)
2805 goto out4
; /* not a mountpoint */
2806 if (!mnt_has_parent(root_mnt
))
2807 goto out4
; /* not attached */
2808 root_mp
= root_mnt
->mnt_mp
;
2809 if (new.mnt
->mnt_root
!= new.dentry
)
2810 goto out4
; /* not a mountpoint */
2811 if (!mnt_has_parent(new_mnt
))
2812 goto out4
; /* not attached */
2813 /* make sure we can reach put_old from new_root */
2814 if (!is_path_reachable(old_mnt
, old
.dentry
, &new))
2816 root_mp
->m_count
++; /* pin it so it won't go away */
2818 detach_mnt(new_mnt
, &parent_path
);
2819 detach_mnt(root_mnt
, &root_parent
);
2820 if (root_mnt
->mnt
.mnt_flags
& MNT_LOCKED
) {
2821 new_mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
2822 root_mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2824 /* mount old root on put_old */
2825 attach_mnt(root_mnt
, old_mnt
, old_mp
);
2826 /* mount new_root on / */
2827 attach_mnt(new_mnt
, real_mount(root_parent
.mnt
), root_mp
);
2828 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
2829 unlock_mount_hash();
2830 chroot_fs_refs(&root
, &new);
2831 put_mountpoint(root_mp
);
2834 unlock_mount(old_mp
);
2836 path_put(&root_parent
);
2837 path_put(&parent_path
);
2849 static void __init
init_mount_tree(void)
2851 struct vfsmount
*mnt
;
2852 struct mnt_namespace
*ns
;
2854 struct file_system_type
*type
;
2856 type
= get_fs_type("rootfs");
2858 panic("Can't find rootfs type");
2859 mnt
= vfs_kern_mount(type
, 0, "rootfs", NULL
);
2860 put_filesystem(type
);
2862 panic("Can't create rootfs");
2864 ns
= create_mnt_ns(mnt
);
2866 panic("Can't allocate initial namespace");
2868 init_task
.nsproxy
->mnt_ns
= ns
;
2872 root
.dentry
= mnt
->mnt_root
;
2874 set_fs_pwd(current
->fs
, &root
);
2875 set_fs_root(current
->fs
, &root
);
2878 void __init
mnt_init(void)
2883 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
2884 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
2886 mount_hashtable
= alloc_large_system_hash("Mount-cache",
2887 sizeof(struct hlist_head
),
2890 &m_hash_shift
, &m_hash_mask
, 0, 0);
2891 mountpoint_hashtable
= alloc_large_system_hash("Mountpoint-cache",
2892 sizeof(struct hlist_head
),
2895 &mp_hash_shift
, &mp_hash_mask
, 0, 0);
2897 if (!mount_hashtable
|| !mountpoint_hashtable
)
2898 panic("Failed to allocate mount hash table\n");
2900 for (u
= 0; u
<= m_hash_mask
; u
++)
2901 INIT_HLIST_HEAD(&mount_hashtable
[u
]);
2902 for (u
= 0; u
<= mp_hash_mask
; u
++)
2903 INIT_HLIST_HEAD(&mountpoint_hashtable
[u
]);
2909 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
2911 fs_kobj
= kobject_create_and_add("fs", NULL
);
2913 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
2918 void put_mnt_ns(struct mnt_namespace
*ns
)
2920 if (!atomic_dec_and_test(&ns
->count
))
2922 drop_collected_mounts(&ns
->root
->mnt
);
2926 struct vfsmount
*kern_mount_data(struct file_system_type
*type
, void *data
)
2928 struct vfsmount
*mnt
;
2929 mnt
= vfs_kern_mount(type
, MS_KERNMOUNT
, type
->name
, data
);
2932 * it is a longterm mount, don't release mnt until
2933 * we unmount before file sys is unregistered
2935 real_mount(mnt
)->mnt_ns
= MNT_NS_INTERNAL
;
2939 EXPORT_SYMBOL_GPL(kern_mount_data
);
2941 void kern_unmount(struct vfsmount
*mnt
)
2943 /* release long term mount so mount point can be released */
2944 if (!IS_ERR_OR_NULL(mnt
)) {
2945 real_mount(mnt
)->mnt_ns
= NULL
;
2946 synchronize_rcu(); /* yecchhh... */
2950 EXPORT_SYMBOL(kern_unmount
);
2952 bool our_mnt(struct vfsmount
*mnt
)
2954 return check_mnt(real_mount(mnt
));
2957 bool current_chrooted(void)
2959 /* Does the current process have a non-standard root */
2960 struct path ns_root
;
2961 struct path fs_root
;
2964 /* Find the namespace root */
2965 ns_root
.mnt
= ¤t
->nsproxy
->mnt_ns
->root
->mnt
;
2966 ns_root
.dentry
= ns_root
.mnt
->mnt_root
;
2968 while (d_mountpoint(ns_root
.dentry
) && follow_down_one(&ns_root
))
2971 get_fs_root(current
->fs
, &fs_root
);
2973 chrooted
= !path_equal(&fs_root
, &ns_root
);
2981 bool fs_fully_visible(struct file_system_type
*type
)
2983 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
2985 bool visible
= false;
2990 down_read(&namespace_sem
);
2991 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
2992 struct mount
*child
;
2993 if (mnt
->mnt
.mnt_sb
->s_type
!= type
)
2996 /* This mount is not fully visible if there are any child mounts
2997 * that cover anything except for empty directories.
2999 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
3000 struct inode
*inode
= child
->mnt_mountpoint
->d_inode
;
3001 if (!S_ISDIR(inode
->i_mode
))
3003 if (inode
->i_nlink
> 2)
3011 up_read(&namespace_sem
);
3015 static void *mntns_get(struct task_struct
*task
)
3017 struct mnt_namespace
*ns
= NULL
;
3018 struct nsproxy
*nsproxy
;
3021 nsproxy
= task
->nsproxy
;
3023 ns
= nsproxy
->mnt_ns
;
3031 static void mntns_put(void *ns
)
3036 static int mntns_install(struct nsproxy
*nsproxy
, void *ns
)
3038 struct fs_struct
*fs
= current
->fs
;
3039 struct mnt_namespace
*mnt_ns
= ns
;
3042 if (!ns_capable(mnt_ns
->user_ns
, CAP_SYS_ADMIN
) ||
3043 !ns_capable(current_user_ns(), CAP_SYS_CHROOT
) ||
3044 !ns_capable(current_user_ns(), CAP_SYS_ADMIN
))
3051 put_mnt_ns(nsproxy
->mnt_ns
);
3052 nsproxy
->mnt_ns
= mnt_ns
;
3055 root
.mnt
= &mnt_ns
->root
->mnt
;
3056 root
.dentry
= mnt_ns
->root
->mnt
.mnt_root
;
3058 while(d_mountpoint(root
.dentry
) && follow_down_one(&root
))
3061 /* Update the pwd and root */
3062 set_fs_pwd(fs
, &root
);
3063 set_fs_root(fs
, &root
);
3069 static unsigned int mntns_inum(void *ns
)
3071 struct mnt_namespace
*mnt_ns
= ns
;
3072 return mnt_ns
->proc_inum
;
3075 const struct proc_ns_operations mntns_operations
= {
3077 .type
= CLONE_NEWNS
,
3080 .install
= mntns_install
,