4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
11 #include <linux/syscalls.h>
12 #include <linux/export.h>
13 #include <linux/capability.h>
14 #include <linux/mnt_namespace.h>
15 #include <linux/user_namespace.h>
16 #include <linux/namei.h>
17 #include <linux/security.h>
18 #include <linux/idr.h>
19 #include <linux/init.h> /* init_rootfs */
20 #include <linux/fs_struct.h> /* get_fs_root et.al. */
21 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
22 #include <linux/uaccess.h>
23 #include <linux/proc_ns.h>
24 #include <linux/magic.h>
25 #include <linux/bootmem.h>
26 #include <linux/task_work.h>
30 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 void drop_mountpoint(struct fs_pin
*p
)
195 struct mount
*m
= container_of(p
, struct mount
, mnt_umount
);
196 dput(m
->mnt_ex_mountpoint
);
201 static struct mount
*alloc_vfsmnt(const char *name
)
203 struct mount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
207 err
= mnt_alloc_id(mnt
);
212 mnt
->mnt_devname
= kstrdup_const(name
, GFP_KERNEL
);
213 if (!mnt
->mnt_devname
)
218 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
220 goto out_free_devname
;
222 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
225 mnt
->mnt_writers
= 0;
228 INIT_HLIST_NODE(&mnt
->mnt_hash
);
229 INIT_LIST_HEAD(&mnt
->mnt_child
);
230 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
231 INIT_LIST_HEAD(&mnt
->mnt_list
);
232 INIT_LIST_HEAD(&mnt
->mnt_expire
);
233 INIT_LIST_HEAD(&mnt
->mnt_share
);
234 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
235 INIT_LIST_HEAD(&mnt
->mnt_slave
);
236 INIT_HLIST_NODE(&mnt
->mnt_mp_list
);
237 #ifdef CONFIG_FSNOTIFY
238 INIT_HLIST_HEAD(&mnt
->mnt_fsnotify_marks
);
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 bool 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);
615 * find the first mount at @dentry on vfsmount @mnt.
616 * call under rcu_read_lock()
618 struct mount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
620 struct hlist_head
*head
= m_hash(mnt
, dentry
);
623 hlist_for_each_entry_rcu(p
, head
, mnt_hash
)
624 if (&p
->mnt_parent
->mnt
== mnt
&& p
->mnt_mountpoint
== dentry
)
630 * find the last mount at @dentry on vfsmount @mnt.
631 * mount_lock must be held.
633 struct mount
*__lookup_mnt_last(struct vfsmount
*mnt
, struct dentry
*dentry
)
635 struct mount
*p
, *res
= NULL
;
636 p
= __lookup_mnt(mnt
, dentry
);
639 if (!(p
->mnt
.mnt_flags
& MNT_UMOUNT
))
641 hlist_for_each_entry_continue(p
, mnt_hash
) {
642 if (&p
->mnt_parent
->mnt
!= mnt
|| p
->mnt_mountpoint
!= dentry
)
644 if (!(p
->mnt
.mnt_flags
& MNT_UMOUNT
))
652 * lookup_mnt - Return the first child mount mounted at path
654 * "First" means first mounted chronologically. If you create the
657 * mount /dev/sda1 /mnt
658 * mount /dev/sda2 /mnt
659 * mount /dev/sda3 /mnt
661 * Then lookup_mnt() on the base /mnt dentry in the root mount will
662 * return successively the root dentry and vfsmount of /dev/sda1, then
663 * /dev/sda2, then /dev/sda3, then NULL.
665 * lookup_mnt takes a reference to the found vfsmount.
667 struct vfsmount
*lookup_mnt(struct path
*path
)
669 struct mount
*child_mnt
;
675 seq
= read_seqbegin(&mount_lock
);
676 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
);
677 m
= child_mnt
? &child_mnt
->mnt
: NULL
;
678 } while (!legitimize_mnt(m
, seq
));
684 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
685 * current mount namespace.
687 * The common case is dentries are not mountpoints at all and that
688 * test is handled inline. For the slow case when we are actually
689 * dealing with a mountpoint of some kind, walk through all of the
690 * mounts in the current mount namespace and test to see if the dentry
693 * The mount_hashtable is not usable in the context because we
694 * need to identify all mounts that may be in the current mount
695 * namespace not just a mount that happens to have some specified
698 bool __is_local_mountpoint(struct dentry
*dentry
)
700 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
702 bool is_covered
= false;
704 if (!d_mountpoint(dentry
))
707 down_read(&namespace_sem
);
708 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
709 is_covered
= (mnt
->mnt_mountpoint
== dentry
);
713 up_read(&namespace_sem
);
718 static struct mountpoint
*lookup_mountpoint(struct dentry
*dentry
)
720 struct hlist_head
*chain
= mp_hash(dentry
);
721 struct mountpoint
*mp
;
723 hlist_for_each_entry(mp
, chain
, m_hash
) {
724 if (mp
->m_dentry
== dentry
) {
725 /* might be worth a WARN_ON() */
726 if (d_unlinked(dentry
))
727 return ERR_PTR(-ENOENT
);
735 static struct mountpoint
*new_mountpoint(struct dentry
*dentry
)
737 struct hlist_head
*chain
= mp_hash(dentry
);
738 struct mountpoint
*mp
;
741 mp
= kmalloc(sizeof(struct mountpoint
), GFP_KERNEL
);
743 return ERR_PTR(-ENOMEM
);
745 ret
= d_set_mounted(dentry
);
751 mp
->m_dentry
= dentry
;
753 hlist_add_head(&mp
->m_hash
, chain
);
754 INIT_HLIST_HEAD(&mp
->m_list
);
758 static void put_mountpoint(struct mountpoint
*mp
)
760 if (!--mp
->m_count
) {
761 struct dentry
*dentry
= mp
->m_dentry
;
762 BUG_ON(!hlist_empty(&mp
->m_list
));
763 spin_lock(&dentry
->d_lock
);
764 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
765 spin_unlock(&dentry
->d_lock
);
766 hlist_del(&mp
->m_hash
);
771 static inline int check_mnt(struct mount
*mnt
)
773 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
777 * vfsmount lock must be held for write
779 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
783 wake_up_interruptible(&ns
->poll
);
788 * vfsmount lock must be held for write
790 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
792 if (ns
&& ns
->event
!= event
) {
794 wake_up_interruptible(&ns
->poll
);
799 * vfsmount lock must be held for write
801 static void unhash_mnt(struct mount
*mnt
)
803 mnt
->mnt_parent
= mnt
;
804 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
805 list_del_init(&mnt
->mnt_child
);
806 hlist_del_init_rcu(&mnt
->mnt_hash
);
807 hlist_del_init(&mnt
->mnt_mp_list
);
808 put_mountpoint(mnt
->mnt_mp
);
813 * vfsmount lock must be held for write
815 static void detach_mnt(struct mount
*mnt
, struct path
*old_path
)
817 old_path
->dentry
= mnt
->mnt_mountpoint
;
818 old_path
->mnt
= &mnt
->mnt_parent
->mnt
;
823 * vfsmount lock must be held for write
825 static void umount_mnt(struct mount
*mnt
)
827 /* old mountpoint will be dropped when we can do that */
828 mnt
->mnt_ex_mountpoint
= mnt
->mnt_mountpoint
;
833 * vfsmount lock must be held for write
835 void mnt_set_mountpoint(struct mount
*mnt
,
836 struct mountpoint
*mp
,
837 struct mount
*child_mnt
)
840 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
841 child_mnt
->mnt_mountpoint
= dget(mp
->m_dentry
);
842 child_mnt
->mnt_parent
= mnt
;
843 child_mnt
->mnt_mp
= mp
;
844 hlist_add_head(&child_mnt
->mnt_mp_list
, &mp
->m_list
);
848 * vfsmount lock must be held for write
850 static void attach_mnt(struct mount
*mnt
,
851 struct mount
*parent
,
852 struct mountpoint
*mp
)
854 mnt_set_mountpoint(parent
, mp
, mnt
);
855 hlist_add_head_rcu(&mnt
->mnt_hash
, m_hash(&parent
->mnt
, mp
->m_dentry
));
856 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
859 static void attach_shadowed(struct mount
*mnt
,
860 struct mount
*parent
,
861 struct mount
*shadows
)
864 hlist_add_behind_rcu(&mnt
->mnt_hash
, &shadows
->mnt_hash
);
865 list_add(&mnt
->mnt_child
, &shadows
->mnt_child
);
867 hlist_add_head_rcu(&mnt
->mnt_hash
,
868 m_hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
869 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
874 * vfsmount lock must be held for write
876 static void commit_tree(struct mount
*mnt
, struct mount
*shadows
)
878 struct mount
*parent
= mnt
->mnt_parent
;
881 struct mnt_namespace
*n
= parent
->mnt_ns
;
883 BUG_ON(parent
== mnt
);
885 list_add_tail(&head
, &mnt
->mnt_list
);
886 list_for_each_entry(m
, &head
, mnt_list
)
889 list_splice(&head
, n
->list
.prev
);
891 attach_shadowed(mnt
, parent
, shadows
);
892 touch_mnt_namespace(n
);
895 static struct mount
*next_mnt(struct mount
*p
, struct mount
*root
)
897 struct list_head
*next
= p
->mnt_mounts
.next
;
898 if (next
== &p
->mnt_mounts
) {
902 next
= p
->mnt_child
.next
;
903 if (next
!= &p
->mnt_parent
->mnt_mounts
)
908 return list_entry(next
, struct mount
, mnt_child
);
911 static struct mount
*skip_mnt_tree(struct mount
*p
)
913 struct list_head
*prev
= p
->mnt_mounts
.prev
;
914 while (prev
!= &p
->mnt_mounts
) {
915 p
= list_entry(prev
, struct mount
, mnt_child
);
916 prev
= p
->mnt_mounts
.prev
;
922 vfs_kern_mount(struct file_system_type
*type
, int flags
, const char *name
, void *data
)
928 return ERR_PTR(-ENODEV
);
930 mnt
= alloc_vfsmnt(name
);
932 return ERR_PTR(-ENOMEM
);
934 if (flags
& MS_KERNMOUNT
)
935 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
937 root
= mount_fs(type
, flags
, name
, data
);
941 return ERR_CAST(root
);
944 mnt
->mnt
.mnt_root
= root
;
945 mnt
->mnt
.mnt_sb
= root
->d_sb
;
946 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
947 mnt
->mnt_parent
= mnt
;
949 list_add_tail(&mnt
->mnt_instance
, &root
->d_sb
->s_mounts
);
953 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
955 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
958 struct super_block
*sb
= old
->mnt
.mnt_sb
;
962 mnt
= alloc_vfsmnt(old
->mnt_devname
);
964 return ERR_PTR(-ENOMEM
);
966 if (flag
& (CL_SLAVE
| CL_PRIVATE
| CL_SHARED_TO_SLAVE
))
967 mnt
->mnt_group_id
= 0; /* not a peer of original */
969 mnt
->mnt_group_id
= old
->mnt_group_id
;
971 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
972 err
= mnt_alloc_group_id(mnt
);
977 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
& ~(MNT_WRITE_HOLD
|MNT_MARKED
);
978 /* Don't allow unprivileged users to change mount flags */
979 if (flag
& CL_UNPRIVILEGED
) {
980 mnt
->mnt
.mnt_flags
|= MNT_LOCK_ATIME
;
982 if (mnt
->mnt
.mnt_flags
& MNT_READONLY
)
983 mnt
->mnt
.mnt_flags
|= MNT_LOCK_READONLY
;
985 if (mnt
->mnt
.mnt_flags
& MNT_NODEV
)
986 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NODEV
;
988 if (mnt
->mnt
.mnt_flags
& MNT_NOSUID
)
989 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NOSUID
;
991 if (mnt
->mnt
.mnt_flags
& MNT_NOEXEC
)
992 mnt
->mnt
.mnt_flags
|= MNT_LOCK_NOEXEC
;
995 /* Don't allow unprivileged users to reveal what is under a mount */
996 if ((flag
& CL_UNPRIVILEGED
) &&
997 (!(flag
& CL_EXPIRE
) || list_empty(&old
->mnt_expire
)))
998 mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
1000 atomic_inc(&sb
->s_active
);
1001 mnt
->mnt
.mnt_sb
= sb
;
1002 mnt
->mnt
.mnt_root
= dget(root
);
1003 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1004 mnt
->mnt_parent
= mnt
;
1006 list_add_tail(&mnt
->mnt_instance
, &sb
->s_mounts
);
1007 unlock_mount_hash();
1009 if ((flag
& CL_SLAVE
) ||
1010 ((flag
& CL_SHARED_TO_SLAVE
) && IS_MNT_SHARED(old
))) {
1011 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
1012 mnt
->mnt_master
= old
;
1013 CLEAR_MNT_SHARED(mnt
);
1014 } else if (!(flag
& CL_PRIVATE
)) {
1015 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
1016 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
1017 if (IS_MNT_SLAVE(old
))
1018 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
1019 mnt
->mnt_master
= old
->mnt_master
;
1021 if (flag
& CL_MAKE_SHARED
)
1022 set_mnt_shared(mnt
);
1024 /* stick the duplicate mount on the same expiry list
1025 * as the original if that was on one */
1026 if (flag
& CL_EXPIRE
) {
1027 if (!list_empty(&old
->mnt_expire
))
1028 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
1036 return ERR_PTR(err
);
1039 static void cleanup_mnt(struct mount
*mnt
)
1042 * This probably indicates that somebody messed
1043 * up a mnt_want/drop_write() pair. If this
1044 * happens, the filesystem was probably unable
1045 * to make r/w->r/o transitions.
1048 * The locking used to deal with mnt_count decrement provides barriers,
1049 * so mnt_get_writers() below is safe.
1051 WARN_ON(mnt_get_writers(mnt
));
1052 if (unlikely(mnt
->mnt_pins
.first
))
1054 fsnotify_vfsmount_delete(&mnt
->mnt
);
1055 dput(mnt
->mnt
.mnt_root
);
1056 deactivate_super(mnt
->mnt
.mnt_sb
);
1058 call_rcu(&mnt
->mnt_rcu
, delayed_free_vfsmnt
);
1061 static void __cleanup_mnt(struct rcu_head
*head
)
1063 cleanup_mnt(container_of(head
, struct mount
, mnt_rcu
));
1066 static LLIST_HEAD(delayed_mntput_list
);
1067 static void delayed_mntput(struct work_struct
*unused
)
1069 struct llist_node
*node
= llist_del_all(&delayed_mntput_list
);
1070 struct llist_node
*next
;
1072 for (; node
; node
= next
) {
1073 next
= llist_next(node
);
1074 cleanup_mnt(llist_entry(node
, struct mount
, mnt_llist
));
1077 static DECLARE_DELAYED_WORK(delayed_mntput_work
, delayed_mntput
);
1079 static void mntput_no_expire(struct mount
*mnt
)
1082 mnt_add_count(mnt
, -1);
1083 if (likely(mnt
->mnt_ns
)) { /* shouldn't be the last one */
1088 if (mnt_get_count(mnt
)) {
1090 unlock_mount_hash();
1093 if (unlikely(mnt
->mnt
.mnt_flags
& MNT_DOOMED
)) {
1095 unlock_mount_hash();
1098 mnt
->mnt
.mnt_flags
|= MNT_DOOMED
;
1101 list_del(&mnt
->mnt_instance
);
1102 unlock_mount_hash();
1104 if (likely(!(mnt
->mnt
.mnt_flags
& MNT_INTERNAL
))) {
1105 struct task_struct
*task
= current
;
1106 if (likely(!(task
->flags
& PF_KTHREAD
))) {
1107 init_task_work(&mnt
->mnt_rcu
, __cleanup_mnt
);
1108 if (!task_work_add(task
, &mnt
->mnt_rcu
, true))
1111 if (llist_add(&mnt
->mnt_llist
, &delayed_mntput_list
))
1112 schedule_delayed_work(&delayed_mntput_work
, 1);
1118 void mntput(struct vfsmount
*mnt
)
1121 struct mount
*m
= real_mount(mnt
);
1122 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1123 if (unlikely(m
->mnt_expiry_mark
))
1124 m
->mnt_expiry_mark
= 0;
1125 mntput_no_expire(m
);
1128 EXPORT_SYMBOL(mntput
);
1130 struct vfsmount
*mntget(struct vfsmount
*mnt
)
1133 mnt_add_count(real_mount(mnt
), 1);
1136 EXPORT_SYMBOL(mntget
);
1138 struct vfsmount
*mnt_clone_internal(struct path
*path
)
1141 p
= clone_mnt(real_mount(path
->mnt
), path
->dentry
, CL_PRIVATE
);
1144 p
->mnt
.mnt_flags
|= MNT_INTERNAL
;
1148 static inline void mangle(struct seq_file
*m
, const char *s
)
1150 seq_escape(m
, s
, " \t\n\\");
1154 * Simple .show_options callback for filesystems which don't want to
1155 * implement more complex mount option showing.
1157 * See also save_mount_options().
1159 int generic_show_options(struct seq_file
*m
, struct dentry
*root
)
1161 const char *options
;
1164 options
= rcu_dereference(root
->d_sb
->s_options
);
1166 if (options
!= NULL
&& options
[0]) {
1174 EXPORT_SYMBOL(generic_show_options
);
1177 * If filesystem uses generic_show_options(), this function should be
1178 * called from the fill_super() callback.
1180 * The .remount_fs callback usually needs to be handled in a special
1181 * way, to make sure, that previous options are not overwritten if the
1184 * Also note, that if the filesystem's .remount_fs function doesn't
1185 * reset all options to their default value, but changes only newly
1186 * given options, then the displayed options will not reflect reality
1189 void save_mount_options(struct super_block
*sb
, char *options
)
1191 BUG_ON(sb
->s_options
);
1192 rcu_assign_pointer(sb
->s_options
, kstrdup(options
, GFP_KERNEL
));
1194 EXPORT_SYMBOL(save_mount_options
);
1196 void replace_mount_options(struct super_block
*sb
, char *options
)
1198 char *old
= sb
->s_options
;
1199 rcu_assign_pointer(sb
->s_options
, options
);
1205 EXPORT_SYMBOL(replace_mount_options
);
1207 #ifdef CONFIG_PROC_FS
1208 /* iterator; we want it to have access to namespace_sem, thus here... */
1209 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
1211 struct proc_mounts
*p
= proc_mounts(m
);
1213 down_read(&namespace_sem
);
1214 if (p
->cached_event
== p
->ns
->event
) {
1215 void *v
= p
->cached_mount
;
1216 if (*pos
== p
->cached_index
)
1218 if (*pos
== p
->cached_index
+ 1) {
1219 v
= seq_list_next(v
, &p
->ns
->list
, &p
->cached_index
);
1220 return p
->cached_mount
= v
;
1224 p
->cached_event
= p
->ns
->event
;
1225 p
->cached_mount
= seq_list_start(&p
->ns
->list
, *pos
);
1226 p
->cached_index
= *pos
;
1227 return p
->cached_mount
;
1230 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
1232 struct proc_mounts
*p
= proc_mounts(m
);
1234 p
->cached_mount
= seq_list_next(v
, &p
->ns
->list
, pos
);
1235 p
->cached_index
= *pos
;
1236 return p
->cached_mount
;
1239 static void m_stop(struct seq_file
*m
, void *v
)
1241 up_read(&namespace_sem
);
1244 static int m_show(struct seq_file
*m
, void *v
)
1246 struct proc_mounts
*p
= proc_mounts(m
);
1247 struct mount
*r
= list_entry(v
, struct mount
, mnt_list
);
1248 return p
->show(m
, &r
->mnt
);
1251 const struct seq_operations mounts_op
= {
1257 #endif /* CONFIG_PROC_FS */
1260 * may_umount_tree - check if a mount tree is busy
1261 * @mnt: root of mount tree
1263 * This is called to check if a tree of mounts has any
1264 * open files, pwds, chroots or sub mounts that are
1267 int may_umount_tree(struct vfsmount
*m
)
1269 struct mount
*mnt
= real_mount(m
);
1270 int actual_refs
= 0;
1271 int minimum_refs
= 0;
1275 /* write lock needed for mnt_get_count */
1277 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1278 actual_refs
+= mnt_get_count(p
);
1281 unlock_mount_hash();
1283 if (actual_refs
> minimum_refs
)
1289 EXPORT_SYMBOL(may_umount_tree
);
1292 * may_umount - check if a mount point is busy
1293 * @mnt: root of mount
1295 * This is called to check if a mount point has any
1296 * open files, pwds, chroots or sub mounts. If the
1297 * mount has sub mounts this will return busy
1298 * regardless of whether the sub mounts are busy.
1300 * Doesn't take quota and stuff into account. IOW, in some cases it will
1301 * give false negatives. The main reason why it's here is that we need
1302 * a non-destructive way to look for easily umountable filesystems.
1304 int may_umount(struct vfsmount
*mnt
)
1307 down_read(&namespace_sem
);
1309 if (propagate_mount_busy(real_mount(mnt
), 2))
1311 unlock_mount_hash();
1312 up_read(&namespace_sem
);
1316 EXPORT_SYMBOL(may_umount
);
1318 static HLIST_HEAD(unmounted
); /* protected by namespace_sem */
1320 static void namespace_unlock(void)
1322 struct hlist_head head
;
1324 hlist_move_list(&unmounted
, &head
);
1326 up_write(&namespace_sem
);
1328 if (likely(hlist_empty(&head
)))
1333 group_pin_kill(&head
);
1336 static inline void namespace_lock(void)
1338 down_write(&namespace_sem
);
1341 enum umount_tree_flags
{
1343 UMOUNT_PROPAGATE
= 2,
1346 * mount_lock must be held
1347 * namespace_sem must be held for write
1349 static void umount_tree(struct mount
*mnt
, enum umount_tree_flags how
)
1351 LIST_HEAD(tmp_list
);
1354 if (how
& UMOUNT_PROPAGATE
)
1355 propagate_mount_unlock(mnt
);
1357 /* Gather the mounts to umount */
1358 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1359 p
->mnt
.mnt_flags
|= MNT_UMOUNT
;
1360 list_move(&p
->mnt_list
, &tmp_list
);
1363 /* Hide the mounts from mnt_mounts */
1364 list_for_each_entry(p
, &tmp_list
, mnt_list
) {
1365 list_del_init(&p
->mnt_child
);
1368 /* Add propogated mounts to the tmp_list */
1369 if (how
& UMOUNT_PROPAGATE
)
1370 propagate_umount(&tmp_list
);
1372 while (!list_empty(&tmp_list
)) {
1373 p
= list_first_entry(&tmp_list
, struct mount
, mnt_list
);
1374 list_del_init(&p
->mnt_expire
);
1375 list_del_init(&p
->mnt_list
);
1376 __touch_mnt_namespace(p
->mnt_ns
);
1378 if (how
& UMOUNT_SYNC
)
1379 p
->mnt
.mnt_flags
|= MNT_SYNC_UMOUNT
;
1381 pin_insert_group(&p
->mnt_umount
, &p
->mnt_parent
->mnt
, &unmounted
);
1382 if (mnt_has_parent(p
)) {
1383 mnt_add_count(p
->mnt_parent
, -1);
1386 change_mnt_propagation(p
, MS_PRIVATE
);
1390 static void shrink_submounts(struct mount
*mnt
);
1392 static int do_umount(struct mount
*mnt
, int flags
)
1394 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1397 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1402 * Allow userspace to request a mountpoint be expired rather than
1403 * unmounting unconditionally. Unmount only happens if:
1404 * (1) the mark is already set (the mark is cleared by mntput())
1405 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1407 if (flags
& MNT_EXPIRE
) {
1408 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1409 flags
& (MNT_FORCE
| MNT_DETACH
))
1413 * probably don't strictly need the lock here if we examined
1414 * all race cases, but it's a slowpath.
1417 if (mnt_get_count(mnt
) != 2) {
1418 unlock_mount_hash();
1421 unlock_mount_hash();
1423 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1428 * If we may have to abort operations to get out of this
1429 * mount, and they will themselves hold resources we must
1430 * allow the fs to do things. In the Unix tradition of
1431 * 'Gee thats tricky lets do it in userspace' the umount_begin
1432 * might fail to complete on the first run through as other tasks
1433 * must return, and the like. Thats for the mount program to worry
1434 * about for the moment.
1437 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1438 sb
->s_op
->umount_begin(sb
);
1442 * No sense to grab the lock for this test, but test itself looks
1443 * somewhat bogus. Suggestions for better replacement?
1444 * Ho-hum... In principle, we might treat that as umount + switch
1445 * to rootfs. GC would eventually take care of the old vfsmount.
1446 * Actually it makes sense, especially if rootfs would contain a
1447 * /reboot - static binary that would close all descriptors and
1448 * call reboot(9). Then init(8) could umount root and exec /reboot.
1450 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1452 * Special case for "unmounting" root ...
1453 * we just try to remount it readonly.
1455 if (!capable(CAP_SYS_ADMIN
))
1457 down_write(&sb
->s_umount
);
1458 if (!(sb
->s_flags
& MS_RDONLY
))
1459 retval
= do_remount_sb(sb
, MS_RDONLY
, NULL
, 0);
1460 up_write(&sb
->s_umount
);
1468 if (flags
& MNT_DETACH
) {
1469 if (!list_empty(&mnt
->mnt_list
))
1470 umount_tree(mnt
, UMOUNT_PROPAGATE
);
1473 shrink_submounts(mnt
);
1475 if (!propagate_mount_busy(mnt
, 2)) {
1476 if (!list_empty(&mnt
->mnt_list
))
1477 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
1481 unlock_mount_hash();
1487 * __detach_mounts - lazily unmount all mounts on the specified dentry
1489 * During unlink, rmdir, and d_drop it is possible to loose the path
1490 * to an existing mountpoint, and wind up leaking the mount.
1491 * detach_mounts allows lazily unmounting those mounts instead of
1494 * The caller may hold dentry->d_inode->i_mutex.
1496 void __detach_mounts(struct dentry
*dentry
)
1498 struct mountpoint
*mp
;
1502 mp
= lookup_mountpoint(dentry
);
1507 while (!hlist_empty(&mp
->m_list
)) {
1508 mnt
= hlist_entry(mp
->m_list
.first
, struct mount
, mnt_mp_list
);
1509 umount_tree(mnt
, 0);
1511 unlock_mount_hash();
1518 * Is the caller allowed to modify his namespace?
1520 static inline bool may_mount(void)
1522 return ns_capable(current
->nsproxy
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
);
1526 * Now umount can handle mount points as well as block devices.
1527 * This is important for filesystems which use unnamed block devices.
1529 * We now support a flag for forced unmount like the other 'big iron'
1530 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1533 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1538 int lookup_flags
= 0;
1540 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1546 if (!(flags
& UMOUNT_NOFOLLOW
))
1547 lookup_flags
|= LOOKUP_FOLLOW
;
1549 retval
= user_path_mountpoint_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1552 mnt
= real_mount(path
.mnt
);
1554 if (path
.dentry
!= path
.mnt
->mnt_root
)
1556 if (!check_mnt(mnt
))
1558 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
1561 if (flags
& MNT_FORCE
&& !capable(CAP_SYS_ADMIN
))
1564 retval
= do_umount(mnt
, flags
);
1566 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1568 mntput_no_expire(mnt
);
1573 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1576 * The 2.0 compatible umount. No flags.
1578 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1580 return sys_umount(name
, 0);
1585 static bool is_mnt_ns_file(struct dentry
*dentry
)
1587 /* Is this a proxy for a mount namespace? */
1588 return dentry
->d_op
== &ns_dentry_operations
&&
1589 dentry
->d_fsdata
== &mntns_operations
;
1592 struct mnt_namespace
*to_mnt_ns(struct ns_common
*ns
)
1594 return container_of(ns
, struct mnt_namespace
, ns
);
1597 static bool mnt_ns_loop(struct dentry
*dentry
)
1599 /* Could bind mounting the mount namespace inode cause a
1600 * mount namespace loop?
1602 struct mnt_namespace
*mnt_ns
;
1603 if (!is_mnt_ns_file(dentry
))
1606 mnt_ns
= to_mnt_ns(get_proc_ns(dentry
->d_inode
));
1607 return current
->nsproxy
->mnt_ns
->seq
>= mnt_ns
->seq
;
1610 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1613 struct mount
*res
, *p
, *q
, *r
, *parent
;
1615 if (!(flag
& CL_COPY_UNBINDABLE
) && IS_MNT_UNBINDABLE(mnt
))
1616 return ERR_PTR(-EINVAL
);
1618 if (!(flag
& CL_COPY_MNT_NS_FILE
) && is_mnt_ns_file(dentry
))
1619 return ERR_PTR(-EINVAL
);
1621 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1625 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1628 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
1630 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
1633 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
1634 struct mount
*t
= NULL
;
1635 if (!(flag
& CL_COPY_UNBINDABLE
) &&
1636 IS_MNT_UNBINDABLE(s
)) {
1637 s
= skip_mnt_tree(s
);
1640 if (!(flag
& CL_COPY_MNT_NS_FILE
) &&
1641 is_mnt_ns_file(s
->mnt
.mnt_root
)) {
1642 s
= skip_mnt_tree(s
);
1645 while (p
!= s
->mnt_parent
) {
1651 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
1655 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
1656 mnt_set_mountpoint(parent
, p
->mnt_mp
, q
);
1657 if (!list_empty(&parent
->mnt_mounts
)) {
1658 t
= list_last_entry(&parent
->mnt_mounts
,
1659 struct mount
, mnt_child
);
1660 if (t
->mnt_mp
!= p
->mnt_mp
)
1663 attach_shadowed(q
, parent
, t
);
1664 unlock_mount_hash();
1671 umount_tree(res
, UMOUNT_SYNC
);
1672 unlock_mount_hash();
1677 /* Caller should check returned pointer for errors */
1679 struct vfsmount
*collect_mounts(struct path
*path
)
1683 if (!check_mnt(real_mount(path
->mnt
)))
1684 tree
= ERR_PTR(-EINVAL
);
1686 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
1687 CL_COPY_ALL
| CL_PRIVATE
);
1690 return ERR_CAST(tree
);
1694 void drop_collected_mounts(struct vfsmount
*mnt
)
1698 umount_tree(real_mount(mnt
), UMOUNT_SYNC
);
1699 unlock_mount_hash();
1704 * clone_private_mount - create a private clone of a path
1706 * This creates a new vfsmount, which will be the clone of @path. The new will
1707 * not be attached anywhere in the namespace and will be private (i.e. changes
1708 * to the originating mount won't be propagated into this).
1710 * Release with mntput().
1712 struct vfsmount
*clone_private_mount(struct path
*path
)
1714 struct mount
*old_mnt
= real_mount(path
->mnt
);
1715 struct mount
*new_mnt
;
1717 if (IS_MNT_UNBINDABLE(old_mnt
))
1718 return ERR_PTR(-EINVAL
);
1720 down_read(&namespace_sem
);
1721 new_mnt
= clone_mnt(old_mnt
, path
->dentry
, CL_PRIVATE
);
1722 up_read(&namespace_sem
);
1723 if (IS_ERR(new_mnt
))
1724 return ERR_CAST(new_mnt
);
1726 return &new_mnt
->mnt
;
1728 EXPORT_SYMBOL_GPL(clone_private_mount
);
1730 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
1731 struct vfsmount
*root
)
1734 int res
= f(root
, arg
);
1737 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
1738 res
= f(&mnt
->mnt
, arg
);
1745 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
1749 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
1750 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
1751 mnt_release_group_id(p
);
1755 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
1759 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
1760 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
1761 int err
= mnt_alloc_group_id(p
);
1763 cleanup_group_ids(mnt
, p
);
1773 * @source_mnt : mount tree to be attached
1774 * @nd : place the mount tree @source_mnt is attached
1775 * @parent_nd : if non-null, detach the source_mnt from its parent and
1776 * store the parent mount and mountpoint dentry.
1777 * (done when source_mnt is moved)
1779 * NOTE: in the table below explains the semantics when a source mount
1780 * of a given type is attached to a destination mount of a given type.
1781 * ---------------------------------------------------------------------------
1782 * | BIND MOUNT OPERATION |
1783 * |**************************************************************************
1784 * | source-->| shared | private | slave | unbindable |
1788 * |**************************************************************************
1789 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1791 * |non-shared| shared (+) | private | slave (*) | invalid |
1792 * ***************************************************************************
1793 * A bind operation clones the source mount and mounts the clone on the
1794 * destination mount.
1796 * (++) the cloned mount is propagated to all the mounts in the propagation
1797 * tree of the destination mount and the cloned mount is added to
1798 * the peer group of the source mount.
1799 * (+) the cloned mount is created under the destination mount and is marked
1800 * as shared. The cloned mount is added to the peer group of the source
1802 * (+++) the mount is propagated to all the mounts in the propagation tree
1803 * of the destination mount and the cloned mount is made slave
1804 * of the same master as that of the source mount. The cloned mount
1805 * is marked as 'shared and slave'.
1806 * (*) the cloned mount is made a slave of the same master as that of the
1809 * ---------------------------------------------------------------------------
1810 * | MOVE MOUNT OPERATION |
1811 * |**************************************************************************
1812 * | source-->| shared | private | slave | unbindable |
1816 * |**************************************************************************
1817 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1819 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1820 * ***************************************************************************
1822 * (+) the mount is moved to the destination. And is then propagated to
1823 * all the mounts in the propagation tree of the destination mount.
1824 * (+*) the mount is moved to the destination.
1825 * (+++) the mount is moved to the destination and is then propagated to
1826 * all the mounts belonging to the destination mount's propagation tree.
1827 * the mount is marked as 'shared and slave'.
1828 * (*) the mount continues to be a slave at the new location.
1830 * if the source mount is a tree, the operations explained above is
1831 * applied to each mount in the tree.
1832 * Must be called without spinlocks held, since this function can sleep
1835 static int attach_recursive_mnt(struct mount
*source_mnt
,
1836 struct mount
*dest_mnt
,
1837 struct mountpoint
*dest_mp
,
1838 struct path
*parent_path
)
1840 HLIST_HEAD(tree_list
);
1841 struct mount
*child
, *p
;
1842 struct hlist_node
*n
;
1845 if (IS_MNT_SHARED(dest_mnt
)) {
1846 err
= invent_group_ids(source_mnt
, true);
1849 err
= propagate_mnt(dest_mnt
, dest_mp
, source_mnt
, &tree_list
);
1852 goto out_cleanup_ids
;
1853 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
1859 detach_mnt(source_mnt
, parent_path
);
1860 attach_mnt(source_mnt
, dest_mnt
, dest_mp
);
1861 touch_mnt_namespace(source_mnt
->mnt_ns
);
1863 mnt_set_mountpoint(dest_mnt
, dest_mp
, source_mnt
);
1864 commit_tree(source_mnt
, NULL
);
1867 hlist_for_each_entry_safe(child
, n
, &tree_list
, mnt_hash
) {
1869 hlist_del_init(&child
->mnt_hash
);
1870 q
= __lookup_mnt_last(&child
->mnt_parent
->mnt
,
1871 child
->mnt_mountpoint
);
1872 commit_tree(child
, q
);
1874 unlock_mount_hash();
1879 while (!hlist_empty(&tree_list
)) {
1880 child
= hlist_entry(tree_list
.first
, struct mount
, mnt_hash
);
1881 umount_tree(child
, UMOUNT_SYNC
);
1883 unlock_mount_hash();
1884 cleanup_group_ids(source_mnt
, NULL
);
1889 static struct mountpoint
*lock_mount(struct path
*path
)
1891 struct vfsmount
*mnt
;
1892 struct dentry
*dentry
= path
->dentry
;
1894 mutex_lock(&dentry
->d_inode
->i_mutex
);
1895 if (unlikely(cant_mount(dentry
))) {
1896 mutex_unlock(&dentry
->d_inode
->i_mutex
);
1897 return ERR_PTR(-ENOENT
);
1900 mnt
= lookup_mnt(path
);
1902 struct mountpoint
*mp
= lookup_mountpoint(dentry
);
1904 mp
= new_mountpoint(dentry
);
1907 mutex_unlock(&dentry
->d_inode
->i_mutex
);
1913 mutex_unlock(&path
->dentry
->d_inode
->i_mutex
);
1916 dentry
= path
->dentry
= dget(mnt
->mnt_root
);
1920 static void unlock_mount(struct mountpoint
*where
)
1922 struct dentry
*dentry
= where
->m_dentry
;
1923 put_mountpoint(where
);
1925 mutex_unlock(&dentry
->d_inode
->i_mutex
);
1928 static int graft_tree(struct mount
*mnt
, struct mount
*p
, struct mountpoint
*mp
)
1930 if (mnt
->mnt
.mnt_sb
->s_flags
& MS_NOUSER
)
1933 if (d_is_dir(mp
->m_dentry
) !=
1934 d_is_dir(mnt
->mnt
.mnt_root
))
1937 return attach_recursive_mnt(mnt
, p
, mp
, NULL
);
1941 * Sanity check the flags to change_mnt_propagation.
1944 static int flags_to_propagation_type(int flags
)
1946 int type
= flags
& ~(MS_REC
| MS_SILENT
);
1948 /* Fail if any non-propagation flags are set */
1949 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
1951 /* Only one propagation flag should be set */
1952 if (!is_power_of_2(type
))
1958 * recursively change the type of the mountpoint.
1960 static int do_change_type(struct path
*path
, int flag
)
1963 struct mount
*mnt
= real_mount(path
->mnt
);
1964 int recurse
= flag
& MS_REC
;
1968 if (path
->dentry
!= path
->mnt
->mnt_root
)
1971 type
= flags_to_propagation_type(flag
);
1976 if (type
== MS_SHARED
) {
1977 err
= invent_group_ids(mnt
, recurse
);
1983 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
1984 change_mnt_propagation(m
, type
);
1985 unlock_mount_hash();
1992 static bool has_locked_children(struct mount
*mnt
, struct dentry
*dentry
)
1994 struct mount
*child
;
1995 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
1996 if (!is_subdir(child
->mnt_mountpoint
, dentry
))
1999 if (child
->mnt
.mnt_flags
& MNT_LOCKED
)
2006 * do loopback mount.
2008 static int do_loopback(struct path
*path
, const char *old_name
,
2011 struct path old_path
;
2012 struct mount
*mnt
= NULL
, *old
, *parent
;
2013 struct mountpoint
*mp
;
2015 if (!old_name
|| !*old_name
)
2017 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
2022 if (mnt_ns_loop(old_path
.dentry
))
2025 mp
= lock_mount(path
);
2030 old
= real_mount(old_path
.mnt
);
2031 parent
= real_mount(path
->mnt
);
2034 if (IS_MNT_UNBINDABLE(old
))
2037 if (!check_mnt(parent
))
2040 if (!check_mnt(old
) && old_path
.dentry
->d_op
!= &ns_dentry_operations
)
2043 if (!recurse
&& has_locked_children(old
, old_path
.dentry
))
2047 mnt
= copy_tree(old
, old_path
.dentry
, CL_COPY_MNT_NS_FILE
);
2049 mnt
= clone_mnt(old
, old_path
.dentry
, 0);
2056 mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2058 err
= graft_tree(mnt
, parent
, mp
);
2061 umount_tree(mnt
, UMOUNT_SYNC
);
2062 unlock_mount_hash();
2067 path_put(&old_path
);
2071 static int change_mount_flags(struct vfsmount
*mnt
, int ms_flags
)
2074 int readonly_request
= 0;
2076 if (ms_flags
& MS_RDONLY
)
2077 readonly_request
= 1;
2078 if (readonly_request
== __mnt_is_readonly(mnt
))
2081 if (readonly_request
)
2082 error
= mnt_make_readonly(real_mount(mnt
));
2084 __mnt_unmake_readonly(real_mount(mnt
));
2089 * change filesystem flags. dir should be a physical root of filesystem.
2090 * If you've mounted a non-root directory somewhere and want to do remount
2091 * on it - tough luck.
2093 static int do_remount(struct path
*path
, int flags
, int mnt_flags
,
2097 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2098 struct mount
*mnt
= real_mount(path
->mnt
);
2100 if (!check_mnt(mnt
))
2103 if (path
->dentry
!= path
->mnt
->mnt_root
)
2106 /* Don't allow changing of locked mnt flags.
2108 * No locks need to be held here while testing the various
2109 * MNT_LOCK flags because those flags can never be cleared
2110 * once they are set.
2112 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_READONLY
) &&
2113 !(mnt_flags
& MNT_READONLY
)) {
2116 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NODEV
) &&
2117 !(mnt_flags
& MNT_NODEV
)) {
2118 /* Was the nodev implicitly added in mount? */
2119 if ((mnt
->mnt_ns
->user_ns
!= &init_user_ns
) &&
2120 !(sb
->s_type
->fs_flags
& FS_USERNS_DEV_MOUNT
)) {
2121 mnt_flags
|= MNT_NODEV
;
2126 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NOSUID
) &&
2127 !(mnt_flags
& MNT_NOSUID
)) {
2130 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_NOEXEC
) &&
2131 !(mnt_flags
& MNT_NOEXEC
)) {
2134 if ((mnt
->mnt
.mnt_flags
& MNT_LOCK_ATIME
) &&
2135 ((mnt
->mnt
.mnt_flags
& MNT_ATIME_MASK
) != (mnt_flags
& MNT_ATIME_MASK
))) {
2139 err
= security_sb_remount(sb
, data
);
2143 down_write(&sb
->s_umount
);
2144 if (flags
& MS_BIND
)
2145 err
= change_mount_flags(path
->mnt
, flags
);
2146 else if (!capable(CAP_SYS_ADMIN
))
2149 err
= do_remount_sb(sb
, flags
, data
, 0);
2152 mnt_flags
|= mnt
->mnt
.mnt_flags
& ~MNT_USER_SETTABLE_MASK
;
2153 mnt
->mnt
.mnt_flags
= mnt_flags
;
2154 touch_mnt_namespace(mnt
->mnt_ns
);
2155 unlock_mount_hash();
2157 up_write(&sb
->s_umount
);
2161 static inline int tree_contains_unbindable(struct mount
*mnt
)
2164 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2165 if (IS_MNT_UNBINDABLE(p
))
2171 static int do_move_mount(struct path
*path
, const char *old_name
)
2173 struct path old_path
, parent_path
;
2176 struct mountpoint
*mp
;
2178 if (!old_name
|| !*old_name
)
2180 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
2184 mp
= lock_mount(path
);
2189 old
= real_mount(old_path
.mnt
);
2190 p
= real_mount(path
->mnt
);
2193 if (!check_mnt(p
) || !check_mnt(old
))
2196 if (old
->mnt
.mnt_flags
& MNT_LOCKED
)
2200 if (old_path
.dentry
!= old_path
.mnt
->mnt_root
)
2203 if (!mnt_has_parent(old
))
2206 if (d_is_dir(path
->dentry
) !=
2207 d_is_dir(old_path
.dentry
))
2210 * Don't move a mount residing in a shared parent.
2212 if (IS_MNT_SHARED(old
->mnt_parent
))
2215 * Don't move a mount tree containing unbindable mounts to a destination
2216 * mount which is shared.
2218 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
2221 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
2225 err
= attach_recursive_mnt(old
, real_mount(path
->mnt
), mp
, &parent_path
);
2229 /* if the mount is moved, it should no longer be expire
2231 list_del_init(&old
->mnt_expire
);
2236 path_put(&parent_path
);
2237 path_put(&old_path
);
2241 static struct vfsmount
*fs_set_subtype(struct vfsmount
*mnt
, const char *fstype
)
2244 const char *subtype
= strchr(fstype
, '.');
2253 mnt
->mnt_sb
->s_subtype
= kstrdup(subtype
, GFP_KERNEL
);
2255 if (!mnt
->mnt_sb
->s_subtype
)
2261 return ERR_PTR(err
);
2265 * add a mount into a namespace's mount tree
2267 static int do_add_mount(struct mount
*newmnt
, struct path
*path
, int mnt_flags
)
2269 struct mountpoint
*mp
;
2270 struct mount
*parent
;
2273 mnt_flags
&= ~MNT_INTERNAL_FLAGS
;
2275 mp
= lock_mount(path
);
2279 parent
= real_mount(path
->mnt
);
2281 if (unlikely(!check_mnt(parent
))) {
2282 /* that's acceptable only for automounts done in private ns */
2283 if (!(mnt_flags
& MNT_SHRINKABLE
))
2285 /* ... and for those we'd better have mountpoint still alive */
2286 if (!parent
->mnt_ns
)
2290 /* Refuse the same filesystem on the same mount point */
2292 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
2293 path
->mnt
->mnt_root
== path
->dentry
)
2297 if (d_is_symlink(newmnt
->mnt
.mnt_root
))
2300 newmnt
->mnt
.mnt_flags
= mnt_flags
;
2301 err
= graft_tree(newmnt
, parent
, mp
);
2309 * create a new mount for userspace and request it to be added into the
2312 static int do_new_mount(struct path
*path
, const char *fstype
, int flags
,
2313 int mnt_flags
, const char *name
, void *data
)
2315 struct file_system_type
*type
;
2316 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2317 struct vfsmount
*mnt
;
2323 type
= get_fs_type(fstype
);
2327 if (user_ns
!= &init_user_ns
) {
2328 if (!(type
->fs_flags
& FS_USERNS_MOUNT
)) {
2329 put_filesystem(type
);
2332 /* Only in special cases allow devices from mounts
2333 * created outside the initial user namespace.
2335 if (!(type
->fs_flags
& FS_USERNS_DEV_MOUNT
)) {
2337 mnt_flags
|= MNT_NODEV
| MNT_LOCK_NODEV
;
2341 mnt
= vfs_kern_mount(type
, flags
, name
, data
);
2342 if (!IS_ERR(mnt
) && (type
->fs_flags
& FS_HAS_SUBTYPE
) &&
2343 !mnt
->mnt_sb
->s_subtype
)
2344 mnt
= fs_set_subtype(mnt
, fstype
);
2346 put_filesystem(type
);
2348 return PTR_ERR(mnt
);
2350 err
= do_add_mount(real_mount(mnt
), path
, mnt_flags
);
2356 int finish_automount(struct vfsmount
*m
, struct path
*path
)
2358 struct mount
*mnt
= real_mount(m
);
2360 /* The new mount record should have at least 2 refs to prevent it being
2361 * expired before we get a chance to add it
2363 BUG_ON(mnt_get_count(mnt
) < 2);
2365 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
2366 m
->mnt_root
== path
->dentry
) {
2371 err
= do_add_mount(mnt
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
2375 /* remove m from any expiration list it may be on */
2376 if (!list_empty(&mnt
->mnt_expire
)) {
2378 list_del_init(&mnt
->mnt_expire
);
2387 * mnt_set_expiry - Put a mount on an expiration list
2388 * @mnt: The mount to list.
2389 * @expiry_list: The list to add the mount to.
2391 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
2395 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
2399 EXPORT_SYMBOL(mnt_set_expiry
);
2402 * process a list of expirable mountpoints with the intent of discarding any
2403 * mountpoints that aren't in use and haven't been touched since last we came
2406 void mark_mounts_for_expiry(struct list_head
*mounts
)
2408 struct mount
*mnt
, *next
;
2409 LIST_HEAD(graveyard
);
2411 if (list_empty(mounts
))
2417 /* extract from the expiration list every vfsmount that matches the
2418 * following criteria:
2419 * - only referenced by its parent vfsmount
2420 * - still marked for expiry (marked on the last call here; marks are
2421 * cleared by mntput())
2423 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
2424 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
2425 propagate_mount_busy(mnt
, 1))
2427 list_move(&mnt
->mnt_expire
, &graveyard
);
2429 while (!list_empty(&graveyard
)) {
2430 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
2431 touch_mnt_namespace(mnt
->mnt_ns
);
2432 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
2434 unlock_mount_hash();
2438 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
2441 * Ripoff of 'select_parent()'
2443 * search the list of submounts for a given mountpoint, and move any
2444 * shrinkable submounts to the 'graveyard' list.
2446 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
2448 struct mount
*this_parent
= parent
;
2449 struct list_head
*next
;
2453 next
= this_parent
->mnt_mounts
.next
;
2455 while (next
!= &this_parent
->mnt_mounts
) {
2456 struct list_head
*tmp
= next
;
2457 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
2460 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
2463 * Descend a level if the d_mounts list is non-empty.
2465 if (!list_empty(&mnt
->mnt_mounts
)) {
2470 if (!propagate_mount_busy(mnt
, 1)) {
2471 list_move_tail(&mnt
->mnt_expire
, graveyard
);
2476 * All done at this level ... ascend and resume the search
2478 if (this_parent
!= parent
) {
2479 next
= this_parent
->mnt_child
.next
;
2480 this_parent
= this_parent
->mnt_parent
;
2487 * process a list of expirable mountpoints with the intent of discarding any
2488 * submounts of a specific parent mountpoint
2490 * mount_lock must be held for write
2492 static void shrink_submounts(struct mount
*mnt
)
2494 LIST_HEAD(graveyard
);
2497 /* extract submounts of 'mountpoint' from the expiration list */
2498 while (select_submounts(mnt
, &graveyard
)) {
2499 while (!list_empty(&graveyard
)) {
2500 m
= list_first_entry(&graveyard
, struct mount
,
2502 touch_mnt_namespace(m
->mnt_ns
);
2503 umount_tree(m
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
2509 * Some copy_from_user() implementations do not return the exact number of
2510 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2511 * Note that this function differs from copy_from_user() in that it will oops
2512 * on bad values of `to', rather than returning a short copy.
2514 static long exact_copy_from_user(void *to
, const void __user
* from
,
2518 const char __user
*f
= from
;
2521 if (!access_ok(VERIFY_READ
, from
, n
))
2525 if (__get_user(c
, f
)) {
2536 int copy_mount_options(const void __user
* data
, unsigned long *where
)
2546 if (!(page
= __get_free_page(GFP_KERNEL
)))
2549 /* We only care that *some* data at the address the user
2550 * gave us is valid. Just in case, we'll zero
2551 * the remainder of the page.
2553 /* copy_from_user cannot cross TASK_SIZE ! */
2554 size
= TASK_SIZE
- (unsigned long)data
;
2555 if (size
> PAGE_SIZE
)
2558 i
= size
- exact_copy_from_user((void *)page
, data
, size
);
2564 memset((char *)page
+ i
, 0, PAGE_SIZE
- i
);
2569 char *copy_mount_string(const void __user
*data
)
2571 return data
? strndup_user(data
, PAGE_SIZE
) : NULL
;
2575 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2576 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2578 * data is a (void *) that can point to any structure up to
2579 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2580 * information (or be NULL).
2582 * Pre-0.97 versions of mount() didn't have a flags word.
2583 * When the flags word was introduced its top half was required
2584 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2585 * Therefore, if this magic number is present, it carries no information
2586 * and must be discarded.
2588 long do_mount(const char *dev_name
, const char __user
*dir_name
,
2589 const char *type_page
, unsigned long flags
, void *data_page
)
2596 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
2597 flags
&= ~MS_MGC_MSK
;
2599 /* Basic sanity checks */
2601 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
2603 /* ... and get the mountpoint */
2604 retval
= user_path(dir_name
, &path
);
2608 retval
= security_sb_mount(dev_name
, &path
,
2609 type_page
, flags
, data_page
);
2610 if (!retval
&& !may_mount())
2615 /* Default to relatime unless overriden */
2616 if (!(flags
& MS_NOATIME
))
2617 mnt_flags
|= MNT_RELATIME
;
2619 /* Separate the per-mountpoint flags */
2620 if (flags
& MS_NOSUID
)
2621 mnt_flags
|= MNT_NOSUID
;
2622 if (flags
& MS_NODEV
)
2623 mnt_flags
|= MNT_NODEV
;
2624 if (flags
& MS_NOEXEC
)
2625 mnt_flags
|= MNT_NOEXEC
;
2626 if (flags
& MS_NOATIME
)
2627 mnt_flags
|= MNT_NOATIME
;
2628 if (flags
& MS_NODIRATIME
)
2629 mnt_flags
|= MNT_NODIRATIME
;
2630 if (flags
& MS_STRICTATIME
)
2631 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
2632 if (flags
& MS_RDONLY
)
2633 mnt_flags
|= MNT_READONLY
;
2635 /* The default atime for remount is preservation */
2636 if ((flags
& MS_REMOUNT
) &&
2637 ((flags
& (MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
|
2638 MS_STRICTATIME
)) == 0)) {
2639 mnt_flags
&= ~MNT_ATIME_MASK
;
2640 mnt_flags
|= path
.mnt
->mnt_flags
& MNT_ATIME_MASK
;
2643 flags
&= ~(MS_NOSUID
| MS_NOEXEC
| MS_NODEV
| MS_ACTIVE
| MS_BORN
|
2644 MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
| MS_KERNMOUNT
|
2647 if (flags
& MS_REMOUNT
)
2648 retval
= do_remount(&path
, flags
& ~MS_REMOUNT
, mnt_flags
,
2650 else if (flags
& MS_BIND
)
2651 retval
= do_loopback(&path
, dev_name
, flags
& MS_REC
);
2652 else if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2653 retval
= do_change_type(&path
, flags
);
2654 else if (flags
& MS_MOVE
)
2655 retval
= do_move_mount(&path
, dev_name
);
2657 retval
= do_new_mount(&path
, type_page
, flags
, mnt_flags
,
2658 dev_name
, data_page
);
2664 static void free_mnt_ns(struct mnt_namespace
*ns
)
2666 ns_free_inum(&ns
->ns
);
2667 put_user_ns(ns
->user_ns
);
2672 * Assign a sequence number so we can detect when we attempt to bind
2673 * mount a reference to an older mount namespace into the current
2674 * mount namespace, preventing reference counting loops. A 64bit
2675 * number incrementing at 10Ghz will take 12,427 years to wrap which
2676 * is effectively never, so we can ignore the possibility.
2678 static atomic64_t mnt_ns_seq
= ATOMIC64_INIT(1);
2680 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*user_ns
)
2682 struct mnt_namespace
*new_ns
;
2685 new_ns
= kmalloc(sizeof(struct mnt_namespace
), GFP_KERNEL
);
2687 return ERR_PTR(-ENOMEM
);
2688 ret
= ns_alloc_inum(&new_ns
->ns
);
2691 return ERR_PTR(ret
);
2693 new_ns
->ns
.ops
= &mntns_operations
;
2694 new_ns
->seq
= atomic64_add_return(1, &mnt_ns_seq
);
2695 atomic_set(&new_ns
->count
, 1);
2696 new_ns
->root
= NULL
;
2697 INIT_LIST_HEAD(&new_ns
->list
);
2698 init_waitqueue_head(&new_ns
->poll
);
2700 new_ns
->user_ns
= get_user_ns(user_ns
);
2704 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
2705 struct user_namespace
*user_ns
, struct fs_struct
*new_fs
)
2707 struct mnt_namespace
*new_ns
;
2708 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
2709 struct mount
*p
, *q
;
2716 if (likely(!(flags
& CLONE_NEWNS
))) {
2723 new_ns
= alloc_mnt_ns(user_ns
);
2728 /* First pass: copy the tree topology */
2729 copy_flags
= CL_COPY_UNBINDABLE
| CL_EXPIRE
;
2730 if (user_ns
!= ns
->user_ns
)
2731 copy_flags
|= CL_SHARED_TO_SLAVE
| CL_UNPRIVILEGED
;
2732 new = copy_tree(old
, old
->mnt
.mnt_root
, copy_flags
);
2735 free_mnt_ns(new_ns
);
2736 return ERR_CAST(new);
2739 list_add_tail(&new_ns
->list
, &new->mnt_list
);
2742 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2743 * as belonging to new namespace. We have already acquired a private
2744 * fs_struct, so tsk->fs->lock is not needed.
2751 if (&p
->mnt
== new_fs
->root
.mnt
) {
2752 new_fs
->root
.mnt
= mntget(&q
->mnt
);
2755 if (&p
->mnt
== new_fs
->pwd
.mnt
) {
2756 new_fs
->pwd
.mnt
= mntget(&q
->mnt
);
2760 p
= next_mnt(p
, old
);
2761 q
= next_mnt(q
, new);
2764 while (p
->mnt
.mnt_root
!= q
->mnt
.mnt_root
)
2765 p
= next_mnt(p
, old
);
2778 * create_mnt_ns - creates a private namespace and adds a root filesystem
2779 * @mnt: pointer to the new root filesystem mountpoint
2781 static struct mnt_namespace
*create_mnt_ns(struct vfsmount
*m
)
2783 struct mnt_namespace
*new_ns
= alloc_mnt_ns(&init_user_ns
);
2784 if (!IS_ERR(new_ns
)) {
2785 struct mount
*mnt
= real_mount(m
);
2786 mnt
->mnt_ns
= new_ns
;
2788 list_add(&mnt
->mnt_list
, &new_ns
->list
);
2795 struct dentry
*mount_subtree(struct vfsmount
*mnt
, const char *name
)
2797 struct mnt_namespace
*ns
;
2798 struct super_block
*s
;
2802 ns
= create_mnt_ns(mnt
);
2804 return ERR_CAST(ns
);
2806 err
= vfs_path_lookup(mnt
->mnt_root
, mnt
,
2807 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
2812 return ERR_PTR(err
);
2814 /* trade a vfsmount reference for active sb one */
2815 s
= path
.mnt
->mnt_sb
;
2816 atomic_inc(&s
->s_active
);
2818 /* lock the sucker */
2819 down_write(&s
->s_umount
);
2820 /* ... and return the root of (sub)tree on it */
2823 EXPORT_SYMBOL(mount_subtree
);
2825 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
2826 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
2831 unsigned long data_page
;
2833 kernel_type
= copy_mount_string(type
);
2834 ret
= PTR_ERR(kernel_type
);
2835 if (IS_ERR(kernel_type
))
2838 kernel_dev
= copy_mount_string(dev_name
);
2839 ret
= PTR_ERR(kernel_dev
);
2840 if (IS_ERR(kernel_dev
))
2843 ret
= copy_mount_options(data
, &data_page
);
2847 ret
= do_mount(kernel_dev
, dir_name
, kernel_type
, flags
,
2848 (void *) data_page
);
2850 free_page(data_page
);
2860 * Return true if path is reachable from root
2862 * namespace_sem or mount_lock is held
2864 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
2865 const struct path
*root
)
2867 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
2868 dentry
= mnt
->mnt_mountpoint
;
2869 mnt
= mnt
->mnt_parent
;
2871 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
2874 int path_is_under(struct path
*path1
, struct path
*path2
)
2877 read_seqlock_excl(&mount_lock
);
2878 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
2879 read_sequnlock_excl(&mount_lock
);
2882 EXPORT_SYMBOL(path_is_under
);
2885 * pivot_root Semantics:
2886 * Moves the root file system of the current process to the directory put_old,
2887 * makes new_root as the new root file system of the current process, and sets
2888 * root/cwd of all processes which had them on the current root to new_root.
2891 * The new_root and put_old must be directories, and must not be on the
2892 * same file system as the current process root. The put_old must be
2893 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2894 * pointed to by put_old must yield the same directory as new_root. No other
2895 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2897 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2898 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2899 * in this situation.
2902 * - we don't move root/cwd if they are not at the root (reason: if something
2903 * cared enough to change them, it's probably wrong to force them elsewhere)
2904 * - it's okay to pick a root that isn't the root of a file system, e.g.
2905 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2906 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2909 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
2910 const char __user
*, put_old
)
2912 struct path
new, old
, parent_path
, root_parent
, root
;
2913 struct mount
*new_mnt
, *root_mnt
, *old_mnt
;
2914 struct mountpoint
*old_mp
, *root_mp
;
2920 error
= user_path_dir(new_root
, &new);
2924 error
= user_path_dir(put_old
, &old
);
2928 error
= security_sb_pivotroot(&old
, &new);
2932 get_fs_root(current
->fs
, &root
);
2933 old_mp
= lock_mount(&old
);
2934 error
= PTR_ERR(old_mp
);
2939 new_mnt
= real_mount(new.mnt
);
2940 root_mnt
= real_mount(root
.mnt
);
2941 old_mnt
= real_mount(old
.mnt
);
2942 if (IS_MNT_SHARED(old_mnt
) ||
2943 IS_MNT_SHARED(new_mnt
->mnt_parent
) ||
2944 IS_MNT_SHARED(root_mnt
->mnt_parent
))
2946 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
2948 if (new_mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
2951 if (d_unlinked(new.dentry
))
2954 if (new_mnt
== root_mnt
|| old_mnt
== root_mnt
)
2955 goto out4
; /* loop, on the same file system */
2957 if (root
.mnt
->mnt_root
!= root
.dentry
)
2958 goto out4
; /* not a mountpoint */
2959 if (!mnt_has_parent(root_mnt
))
2960 goto out4
; /* not attached */
2961 root_mp
= root_mnt
->mnt_mp
;
2962 if (new.mnt
->mnt_root
!= new.dentry
)
2963 goto out4
; /* not a mountpoint */
2964 if (!mnt_has_parent(new_mnt
))
2965 goto out4
; /* not attached */
2966 /* make sure we can reach put_old from new_root */
2967 if (!is_path_reachable(old_mnt
, old
.dentry
, &new))
2969 /* make certain new is below the root */
2970 if (!is_path_reachable(new_mnt
, new.dentry
, &root
))
2972 root_mp
->m_count
++; /* pin it so it won't go away */
2974 detach_mnt(new_mnt
, &parent_path
);
2975 detach_mnt(root_mnt
, &root_parent
);
2976 if (root_mnt
->mnt
.mnt_flags
& MNT_LOCKED
) {
2977 new_mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
2978 root_mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2980 /* mount old root on put_old */
2981 attach_mnt(root_mnt
, old_mnt
, old_mp
);
2982 /* mount new_root on / */
2983 attach_mnt(new_mnt
, real_mount(root_parent
.mnt
), root_mp
);
2984 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
2985 /* A moved mount should not expire automatically */
2986 list_del_init(&new_mnt
->mnt_expire
);
2987 unlock_mount_hash();
2988 chroot_fs_refs(&root
, &new);
2989 put_mountpoint(root_mp
);
2992 unlock_mount(old_mp
);
2994 path_put(&root_parent
);
2995 path_put(&parent_path
);
3007 static void __init
init_mount_tree(void)
3009 struct vfsmount
*mnt
;
3010 struct mnt_namespace
*ns
;
3012 struct file_system_type
*type
;
3014 type
= get_fs_type("rootfs");
3016 panic("Can't find rootfs type");
3017 mnt
= vfs_kern_mount(type
, 0, "rootfs", NULL
);
3018 put_filesystem(type
);
3020 panic("Can't create rootfs");
3022 ns
= create_mnt_ns(mnt
);
3024 panic("Can't allocate initial namespace");
3026 init_task
.nsproxy
->mnt_ns
= ns
;
3030 root
.dentry
= mnt
->mnt_root
;
3031 mnt
->mnt_flags
|= MNT_LOCKED
;
3033 set_fs_pwd(current
->fs
, &root
);
3034 set_fs_root(current
->fs
, &root
);
3037 void __init
mnt_init(void)
3042 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
3043 0, SLAB_HWCACHE_ALIGN
| SLAB_PANIC
, NULL
);
3045 mount_hashtable
= alloc_large_system_hash("Mount-cache",
3046 sizeof(struct hlist_head
),
3049 &m_hash_shift
, &m_hash_mask
, 0, 0);
3050 mountpoint_hashtable
= alloc_large_system_hash("Mountpoint-cache",
3051 sizeof(struct hlist_head
),
3054 &mp_hash_shift
, &mp_hash_mask
, 0, 0);
3056 if (!mount_hashtable
|| !mountpoint_hashtable
)
3057 panic("Failed to allocate mount hash table\n");
3059 for (u
= 0; u
<= m_hash_mask
; u
++)
3060 INIT_HLIST_HEAD(&mount_hashtable
[u
]);
3061 for (u
= 0; u
<= mp_hash_mask
; u
++)
3062 INIT_HLIST_HEAD(&mountpoint_hashtable
[u
]);
3068 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
3070 fs_kobj
= kobject_create_and_add("fs", NULL
);
3072 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
3077 void put_mnt_ns(struct mnt_namespace
*ns
)
3079 if (!atomic_dec_and_test(&ns
->count
))
3081 drop_collected_mounts(&ns
->root
->mnt
);
3085 struct vfsmount
*kern_mount_data(struct file_system_type
*type
, void *data
)
3087 struct vfsmount
*mnt
;
3088 mnt
= vfs_kern_mount(type
, MS_KERNMOUNT
, type
->name
, data
);
3091 * it is a longterm mount, don't release mnt until
3092 * we unmount before file sys is unregistered
3094 real_mount(mnt
)->mnt_ns
= MNT_NS_INTERNAL
;
3098 EXPORT_SYMBOL_GPL(kern_mount_data
);
3100 void kern_unmount(struct vfsmount
*mnt
)
3102 /* release long term mount so mount point can be released */
3103 if (!IS_ERR_OR_NULL(mnt
)) {
3104 real_mount(mnt
)->mnt_ns
= NULL
;
3105 synchronize_rcu(); /* yecchhh... */
3109 EXPORT_SYMBOL(kern_unmount
);
3111 bool our_mnt(struct vfsmount
*mnt
)
3113 return check_mnt(real_mount(mnt
));
3116 bool current_chrooted(void)
3118 /* Does the current process have a non-standard root */
3119 struct path ns_root
;
3120 struct path fs_root
;
3123 /* Find the namespace root */
3124 ns_root
.mnt
= ¤t
->nsproxy
->mnt_ns
->root
->mnt
;
3125 ns_root
.dentry
= ns_root
.mnt
->mnt_root
;
3127 while (d_mountpoint(ns_root
.dentry
) && follow_down_one(&ns_root
))
3130 get_fs_root(current
->fs
, &fs_root
);
3132 chrooted
= !path_equal(&fs_root
, &ns_root
);
3140 bool fs_fully_visible(struct file_system_type
*type
)
3142 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
3144 bool visible
= false;
3149 down_read(&namespace_sem
);
3150 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
3151 struct mount
*child
;
3152 if (mnt
->mnt
.mnt_sb
->s_type
!= type
)
3155 /* This mount is not fully visible if there are any child mounts
3156 * that cover anything except for empty directories.
3158 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
3159 struct inode
*inode
= child
->mnt_mountpoint
->d_inode
;
3160 if (!S_ISDIR(inode
->i_mode
))
3162 if (inode
->i_nlink
> 2)
3170 up_read(&namespace_sem
);
3174 static struct ns_common
*mntns_get(struct task_struct
*task
)
3176 struct ns_common
*ns
= NULL
;
3177 struct nsproxy
*nsproxy
;
3180 nsproxy
= task
->nsproxy
;
3182 ns
= &nsproxy
->mnt_ns
->ns
;
3183 get_mnt_ns(to_mnt_ns(ns
));
3190 static void mntns_put(struct ns_common
*ns
)
3192 put_mnt_ns(to_mnt_ns(ns
));
3195 static int mntns_install(struct nsproxy
*nsproxy
, struct ns_common
*ns
)
3197 struct fs_struct
*fs
= current
->fs
;
3198 struct mnt_namespace
*mnt_ns
= to_mnt_ns(ns
);
3201 if (!ns_capable(mnt_ns
->user_ns
, CAP_SYS_ADMIN
) ||
3202 !ns_capable(current_user_ns(), CAP_SYS_CHROOT
) ||
3203 !ns_capable(current_user_ns(), CAP_SYS_ADMIN
))
3210 put_mnt_ns(nsproxy
->mnt_ns
);
3211 nsproxy
->mnt_ns
= mnt_ns
;
3214 root
.mnt
= &mnt_ns
->root
->mnt
;
3215 root
.dentry
= mnt_ns
->root
->mnt
.mnt_root
;
3217 while(d_mountpoint(root
.dentry
) && follow_down_one(&root
))
3220 /* Update the pwd and root */
3221 set_fs_pwd(fs
, &root
);
3222 set_fs_root(fs
, &root
);
3228 const struct proc_ns_operations mntns_operations
= {
3230 .type
= CLONE_NEWNS
,
3233 .install
= mntns_install
,