1 // SPDX-License-Identifier: GPL-2.0-only
5 * (C) Copyright Al Viro 2000, 2001
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
11 #include <linux/syscalls.h>
12 #include <linux/export.h>
13 #include <linux/capability.h>
14 #include <linux/mnt_namespace.h>
15 #include <linux/user_namespace.h>
16 #include <linux/namei.h>
17 #include <linux/security.h>
18 #include <linux/cred.h>
19 #include <linux/idr.h>
20 #include <linux/init.h> /* init_rootfs */
21 #include <linux/fs_struct.h> /* get_fs_root et.al. */
22 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
23 #include <linux/file.h>
24 #include <linux/uaccess.h>
25 #include <linux/proc_ns.h>
26 #include <linux/magic.h>
27 #include <linux/memblock.h>
28 #include <linux/proc_fs.h>
29 #include <linux/task_work.h>
30 #include <linux/sched/task.h>
31 #include <uapi/linux/mount.h>
32 #include <linux/fs_context.h>
33 #include <linux/shmem_fs.h>
34 #include <linux/mnt_idmapping.h>
39 /* Maximum number of mounts in a mount namespace */
40 static unsigned int sysctl_mount_max __read_mostly
= 100000;
42 static unsigned int m_hash_mask __read_mostly
;
43 static unsigned int m_hash_shift __read_mostly
;
44 static unsigned int mp_hash_mask __read_mostly
;
45 static unsigned int mp_hash_shift __read_mostly
;
47 static __initdata
unsigned long mhash_entries
;
48 static int __init
set_mhash_entries(char *str
)
52 mhash_entries
= simple_strtoul(str
, &str
, 0);
55 __setup("mhash_entries=", set_mhash_entries
);
57 static __initdata
unsigned long mphash_entries
;
58 static int __init
set_mphash_entries(char *str
)
62 mphash_entries
= simple_strtoul(str
, &str
, 0);
65 __setup("mphash_entries=", set_mphash_entries
);
68 static DEFINE_IDA(mnt_id_ida
);
69 static DEFINE_IDA(mnt_group_ida
);
71 static struct hlist_head
*mount_hashtable __read_mostly
;
72 static struct hlist_head
*mountpoint_hashtable __read_mostly
;
73 static struct kmem_cache
*mnt_cache __read_mostly
;
74 static DECLARE_RWSEM(namespace_sem
);
75 static HLIST_HEAD(unmounted
); /* protected by namespace_sem */
76 static LIST_HEAD(ex_mountpoints
); /* protected by namespace_sem */
79 struct user_namespace
*owner
;
84 * Carries the initial idmapping of 0:0:4294967295 which is an identity
85 * mapping. This means that {g,u}id 0 is mapped to {g,u}id 0, {g,u}id 1 is
86 * mapped to {g,u}id 1, [...], {g,u}id 1000 to {g,u}id 1000, [...].
88 struct mnt_idmap nop_mnt_idmap
= {
89 .owner
= &init_user_ns
,
90 .count
= REFCOUNT_INIT(1),
92 EXPORT_SYMBOL_GPL(nop_mnt_idmap
);
95 unsigned int attr_set
;
96 unsigned int attr_clr
;
97 unsigned int propagation
;
98 unsigned int lookup_flags
;
100 struct user_namespace
*mnt_userns
;
101 struct mnt_idmap
*mnt_idmap
;
105 struct kobject
*fs_kobj
;
106 EXPORT_SYMBOL_GPL(fs_kobj
);
109 * vfsmount lock may be taken for read to prevent changes to the
110 * vfsmount hash, ie. during mountpoint lookups or walking back
113 * It should be taken for write in all cases where the vfsmount
114 * tree or hash is modified or when a vfsmount structure is modified.
116 __cacheline_aligned_in_smp
DEFINE_SEQLOCK(mount_lock
);
118 static inline void lock_mount_hash(void)
120 write_seqlock(&mount_lock
);
123 static inline void unlock_mount_hash(void)
125 write_sequnlock(&mount_lock
);
128 static inline struct hlist_head
*m_hash(struct vfsmount
*mnt
, struct dentry
*dentry
)
130 unsigned long tmp
= ((unsigned long)mnt
/ L1_CACHE_BYTES
);
131 tmp
+= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
132 tmp
= tmp
+ (tmp
>> m_hash_shift
);
133 return &mount_hashtable
[tmp
& m_hash_mask
];
136 static inline struct hlist_head
*mp_hash(struct dentry
*dentry
)
138 unsigned long tmp
= ((unsigned long)dentry
/ L1_CACHE_BYTES
);
139 tmp
= tmp
+ (tmp
>> mp_hash_shift
);
140 return &mountpoint_hashtable
[tmp
& mp_hash_mask
];
143 static int mnt_alloc_id(struct mount
*mnt
)
145 int res
= ida_alloc(&mnt_id_ida
, GFP_KERNEL
);
153 static void mnt_free_id(struct mount
*mnt
)
155 ida_free(&mnt_id_ida
, mnt
->mnt_id
);
159 * Allocate a new peer group ID
161 static int mnt_alloc_group_id(struct mount
*mnt
)
163 int res
= ida_alloc_min(&mnt_group_ida
, 1, GFP_KERNEL
);
167 mnt
->mnt_group_id
= res
;
172 * Release a peer group ID
174 void mnt_release_group_id(struct mount
*mnt
)
176 ida_free(&mnt_group_ida
, mnt
->mnt_group_id
);
177 mnt
->mnt_group_id
= 0;
181 * vfsmount lock must be held for read
183 static inline void mnt_add_count(struct mount
*mnt
, int n
)
186 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, n
);
195 * vfsmount lock must be held for write
197 int mnt_get_count(struct mount
*mnt
)
203 for_each_possible_cpu(cpu
) {
204 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_count
;
209 return mnt
->mnt_count
;
214 * mnt_idmap_owner - retrieve owner of the mount's idmapping
215 * @idmap: mount idmapping
217 * This helper will go away once the conversion to use struct mnt_idmap
218 * everywhere has finished at which point the helper will be unexported.
220 * Only code that needs to perform permission checks based on the owner of the
221 * idmapping will get access to it. All other code will solely rely on
222 * idmappings. This will get us type safety so it's impossible to conflate
223 * filesystems idmappings with mount idmappings.
225 * Return: The owner of the idmapping.
227 struct user_namespace
*mnt_idmap_owner(const struct mnt_idmap
*idmap
)
231 EXPORT_SYMBOL_GPL(mnt_idmap_owner
);
234 * mnt_user_ns - retrieve owner of an idmapped mount
235 * @mnt: the relevant vfsmount
237 * This helper will go away once the conversion to use struct mnt_idmap
238 * everywhere has finished at which point the helper will be unexported.
240 * Only code that needs to perform permission checks based on the owner of the
241 * idmapping will get access to it. All other code will solely rely on
242 * idmappings. This will get us type safety so it's impossible to conflate
243 * filesystems idmappings with mount idmappings.
245 * Return: The owner of the idmapped.
247 struct user_namespace
*mnt_user_ns(const struct vfsmount
*mnt
)
249 struct mnt_idmap
*idmap
= mnt_idmap(mnt
);
251 /* Return the actual owner of the filesystem instead of the nop. */
252 if (idmap
== &nop_mnt_idmap
&&
253 !initial_idmapping(mnt
->mnt_sb
->s_user_ns
))
254 return mnt
->mnt_sb
->s_user_ns
;
255 return mnt_idmap_owner(idmap
);
257 EXPORT_SYMBOL_GPL(mnt_user_ns
);
260 * alloc_mnt_idmap - allocate a new idmapping for the mount
261 * @mnt_userns: owning userns of the idmapping
263 * Allocate a new struct mnt_idmap which carries the idmapping of the mount.
265 * Return: On success a new idmap, on error an error pointer is returned.
267 static struct mnt_idmap
*alloc_mnt_idmap(struct user_namespace
*mnt_userns
)
269 struct mnt_idmap
*idmap
;
271 idmap
= kzalloc(sizeof(struct mnt_idmap
), GFP_KERNEL_ACCOUNT
);
273 return ERR_PTR(-ENOMEM
);
275 idmap
->owner
= get_user_ns(mnt_userns
);
276 refcount_set(&idmap
->count
, 1);
281 * mnt_idmap_get - get a reference to an idmapping
282 * @idmap: the idmap to bump the reference on
284 * If @idmap is not the @nop_mnt_idmap bump the reference count.
286 * Return: @idmap with reference count bumped if @not_mnt_idmap isn't passed.
288 static inline struct mnt_idmap
*mnt_idmap_get(struct mnt_idmap
*idmap
)
290 if (idmap
!= &nop_mnt_idmap
)
291 refcount_inc(&idmap
->count
);
297 * mnt_idmap_put - put a reference to an idmapping
298 * @idmap: the idmap to put the reference on
300 * If this is a non-initial idmapping, put the reference count when a mount is
301 * released and free it if we're the last user.
303 static inline void mnt_idmap_put(struct mnt_idmap
*idmap
)
305 if (idmap
!= &nop_mnt_idmap
&& refcount_dec_and_test(&idmap
->count
)) {
306 put_user_ns(idmap
->owner
);
311 static struct mount
*alloc_vfsmnt(const char *name
)
313 struct mount
*mnt
= kmem_cache_zalloc(mnt_cache
, GFP_KERNEL
);
317 err
= mnt_alloc_id(mnt
);
322 mnt
->mnt_devname
= kstrdup_const(name
,
324 if (!mnt
->mnt_devname
)
329 mnt
->mnt_pcp
= alloc_percpu(struct mnt_pcp
);
331 goto out_free_devname
;
333 this_cpu_add(mnt
->mnt_pcp
->mnt_count
, 1);
336 mnt
->mnt_writers
= 0;
339 INIT_HLIST_NODE(&mnt
->mnt_hash
);
340 INIT_LIST_HEAD(&mnt
->mnt_child
);
341 INIT_LIST_HEAD(&mnt
->mnt_mounts
);
342 INIT_LIST_HEAD(&mnt
->mnt_list
);
343 INIT_LIST_HEAD(&mnt
->mnt_expire
);
344 INIT_LIST_HEAD(&mnt
->mnt_share
);
345 INIT_LIST_HEAD(&mnt
->mnt_slave_list
);
346 INIT_LIST_HEAD(&mnt
->mnt_slave
);
347 INIT_HLIST_NODE(&mnt
->mnt_mp_list
);
348 INIT_LIST_HEAD(&mnt
->mnt_umounting
);
349 INIT_HLIST_HEAD(&mnt
->mnt_stuck_children
);
350 mnt
->mnt
.mnt_idmap
= &nop_mnt_idmap
;
356 kfree_const(mnt
->mnt_devname
);
361 kmem_cache_free(mnt_cache
, mnt
);
366 * Most r/o checks on a fs are for operations that take
367 * discrete amounts of time, like a write() or unlink().
368 * We must keep track of when those operations start
369 * (for permission checks) and when they end, so that
370 * we can determine when writes are able to occur to
374 * __mnt_is_readonly: check whether a mount is read-only
375 * @mnt: the mount to check for its write status
377 * This shouldn't be used directly ouside of the VFS.
378 * It does not guarantee that the filesystem will stay
379 * r/w, just that it is right *now*. This can not and
380 * should not be used in place of IS_RDONLY(inode).
381 * mnt_want/drop_write() will _keep_ the filesystem
384 bool __mnt_is_readonly(struct vfsmount
*mnt
)
386 return (mnt
->mnt_flags
& MNT_READONLY
) || sb_rdonly(mnt
->mnt_sb
);
388 EXPORT_SYMBOL_GPL(__mnt_is_readonly
);
390 static inline void mnt_inc_writers(struct mount
*mnt
)
393 this_cpu_inc(mnt
->mnt_pcp
->mnt_writers
);
399 static inline void mnt_dec_writers(struct mount
*mnt
)
402 this_cpu_dec(mnt
->mnt_pcp
->mnt_writers
);
408 static unsigned int mnt_get_writers(struct mount
*mnt
)
411 unsigned int count
= 0;
414 for_each_possible_cpu(cpu
) {
415 count
+= per_cpu_ptr(mnt
->mnt_pcp
, cpu
)->mnt_writers
;
420 return mnt
->mnt_writers
;
424 static int mnt_is_readonly(struct vfsmount
*mnt
)
426 if (mnt
->mnt_sb
->s_readonly_remount
)
428 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
430 return __mnt_is_readonly(mnt
);
434 * Most r/o & frozen checks on a fs are for operations that take discrete
435 * amounts of time, like a write() or unlink(). We must keep track of when
436 * those operations start (for permission checks) and when they end, so that we
437 * can determine when writes are able to occur to a filesystem.
440 * __mnt_want_write - get write access to a mount without freeze protection
441 * @m: the mount on which to take a write
443 * This tells the low-level filesystem that a write is about to be performed to
444 * it, and makes sure that writes are allowed (mnt it read-write) before
445 * returning success. This operation does not protect against filesystem being
446 * frozen. When the write operation is finished, __mnt_drop_write() must be
447 * called. This is effectively a refcount.
449 int __mnt_want_write(struct vfsmount
*m
)
451 struct mount
*mnt
= real_mount(m
);
455 mnt_inc_writers(mnt
);
457 * The store to mnt_inc_writers must be visible before we pass
458 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
459 * incremented count after it has set MNT_WRITE_HOLD.
462 might_lock(&mount_lock
.lock
);
463 while (READ_ONCE(mnt
->mnt
.mnt_flags
) & MNT_WRITE_HOLD
) {
464 if (!IS_ENABLED(CONFIG_PREEMPT_RT
)) {
468 * This prevents priority inversion, if the task
469 * setting MNT_WRITE_HOLD got preempted on a remote
470 * CPU, and it prevents life lock if the task setting
471 * MNT_WRITE_HOLD has a lower priority and is bound to
472 * the same CPU as the task that is spinning here.
481 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
482 * be set to match its requirements. So we must not load that until
483 * MNT_WRITE_HOLD is cleared.
486 if (mnt_is_readonly(m
)) {
487 mnt_dec_writers(mnt
);
496 * mnt_want_write - get write access to a mount
497 * @m: the mount on which to take a write
499 * This tells the low-level filesystem that a write is about to be performed to
500 * it, and makes sure that writes are allowed (mount is read-write, filesystem
501 * is not frozen) before returning success. When the write operation is
502 * finished, mnt_drop_write() must be called. This is effectively a refcount.
504 int mnt_want_write(struct vfsmount
*m
)
508 sb_start_write(m
->mnt_sb
);
509 ret
= __mnt_want_write(m
);
511 sb_end_write(m
->mnt_sb
);
514 EXPORT_SYMBOL_GPL(mnt_want_write
);
517 * __mnt_want_write_file - get write access to a file's mount
518 * @file: the file who's mount on which to take a write
520 * This is like __mnt_want_write, but if the file is already open for writing it
521 * skips incrementing mnt_writers (since the open file already has a reference)
522 * and instead only does the check for emergency r/o remounts. This must be
523 * paired with __mnt_drop_write_file.
525 int __mnt_want_write_file(struct file
*file
)
527 if (file
->f_mode
& FMODE_WRITER
) {
529 * Superblock may have become readonly while there are still
530 * writable fd's, e.g. due to a fs error with errors=remount-ro
532 if (__mnt_is_readonly(file
->f_path
.mnt
))
536 return __mnt_want_write(file
->f_path
.mnt
);
540 * mnt_want_write_file - get write access to a file's mount
541 * @file: the file who's mount on which to take a write
543 * This is like mnt_want_write, but if the file is already open for writing it
544 * skips incrementing mnt_writers (since the open file already has a reference)
545 * and instead only does the freeze protection and the check for emergency r/o
546 * remounts. This must be paired with mnt_drop_write_file.
548 int mnt_want_write_file(struct file
*file
)
552 sb_start_write(file_inode(file
)->i_sb
);
553 ret
= __mnt_want_write_file(file
);
555 sb_end_write(file_inode(file
)->i_sb
);
558 EXPORT_SYMBOL_GPL(mnt_want_write_file
);
561 * __mnt_drop_write - give up write access to a mount
562 * @mnt: the mount on which to give up write access
564 * Tells the low-level filesystem that we are done
565 * performing writes to it. Must be matched with
566 * __mnt_want_write() call above.
568 void __mnt_drop_write(struct vfsmount
*mnt
)
571 mnt_dec_writers(real_mount(mnt
));
576 * mnt_drop_write - give up write access to a mount
577 * @mnt: the mount on which to give up write access
579 * Tells the low-level filesystem that we are done performing writes to it and
580 * also allows filesystem to be frozen again. Must be matched with
581 * mnt_want_write() call above.
583 void mnt_drop_write(struct vfsmount
*mnt
)
585 __mnt_drop_write(mnt
);
586 sb_end_write(mnt
->mnt_sb
);
588 EXPORT_SYMBOL_GPL(mnt_drop_write
);
590 void __mnt_drop_write_file(struct file
*file
)
592 if (!(file
->f_mode
& FMODE_WRITER
))
593 __mnt_drop_write(file
->f_path
.mnt
);
596 void mnt_drop_write_file(struct file
*file
)
598 __mnt_drop_write_file(file
);
599 sb_end_write(file_inode(file
)->i_sb
);
601 EXPORT_SYMBOL(mnt_drop_write_file
);
604 * mnt_hold_writers - prevent write access to the given mount
605 * @mnt: mnt to prevent write access to
607 * Prevents write access to @mnt if there are no active writers for @mnt.
608 * This function needs to be called and return successfully before changing
609 * properties of @mnt that need to remain stable for callers with write access
612 * After this functions has been called successfully callers must pair it with
613 * a call to mnt_unhold_writers() in order to stop preventing write access to
616 * Context: This function expects lock_mount_hash() to be held serializing
617 * setting MNT_WRITE_HOLD.
618 * Return: On success 0 is returned.
619 * On error, -EBUSY is returned.
621 static inline int mnt_hold_writers(struct mount
*mnt
)
623 mnt
->mnt
.mnt_flags
|= MNT_WRITE_HOLD
;
625 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
626 * should be visible before we do.
631 * With writers on hold, if this value is zero, then there are
632 * definitely no active writers (although held writers may subsequently
633 * increment the count, they'll have to wait, and decrement it after
634 * seeing MNT_READONLY).
636 * It is OK to have counter incremented on one CPU and decremented on
637 * another: the sum will add up correctly. The danger would be when we
638 * sum up each counter, if we read a counter before it is incremented,
639 * but then read another CPU's count which it has been subsequently
640 * decremented from -- we would see more decrements than we should.
641 * MNT_WRITE_HOLD protects against this scenario, because
642 * mnt_want_write first increments count, then smp_mb, then spins on
643 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
644 * we're counting up here.
646 if (mnt_get_writers(mnt
) > 0)
653 * mnt_unhold_writers - stop preventing write access to the given mount
654 * @mnt: mnt to stop preventing write access to
656 * Stop preventing write access to @mnt allowing callers to gain write access
659 * This function can only be called after a successful call to
660 * mnt_hold_writers().
662 * Context: This function expects lock_mount_hash() to be held.
664 static inline void mnt_unhold_writers(struct mount
*mnt
)
667 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
668 * that become unheld will see MNT_READONLY.
671 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
674 static int mnt_make_readonly(struct mount
*mnt
)
678 ret
= mnt_hold_writers(mnt
);
680 mnt
->mnt
.mnt_flags
|= MNT_READONLY
;
681 mnt_unhold_writers(mnt
);
685 int sb_prepare_remount_readonly(struct super_block
*sb
)
690 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
691 if (atomic_long_read(&sb
->s_remove_count
))
695 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
696 if (!(mnt
->mnt
.mnt_flags
& MNT_READONLY
)) {
697 err
= mnt_hold_writers(mnt
);
702 if (!err
&& atomic_long_read(&sb
->s_remove_count
))
706 sb
->s_readonly_remount
= 1;
709 list_for_each_entry(mnt
, &sb
->s_mounts
, mnt_instance
) {
710 if (mnt
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
711 mnt
->mnt
.mnt_flags
&= ~MNT_WRITE_HOLD
;
718 static void free_vfsmnt(struct mount
*mnt
)
720 mnt_idmap_put(mnt_idmap(&mnt
->mnt
));
721 kfree_const(mnt
->mnt_devname
);
723 free_percpu(mnt
->mnt_pcp
);
725 kmem_cache_free(mnt_cache
, mnt
);
728 static void delayed_free_vfsmnt(struct rcu_head
*head
)
730 free_vfsmnt(container_of(head
, struct mount
, mnt_rcu
));
733 /* call under rcu_read_lock */
734 int __legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
737 if (read_seqretry(&mount_lock
, seq
))
741 mnt
= real_mount(bastard
);
742 mnt_add_count(mnt
, 1);
743 smp_mb(); // see mntput_no_expire()
744 if (likely(!read_seqretry(&mount_lock
, seq
)))
746 if (bastard
->mnt_flags
& MNT_SYNC_UMOUNT
) {
747 mnt_add_count(mnt
, -1);
751 if (unlikely(bastard
->mnt_flags
& MNT_DOOMED
)) {
752 mnt_add_count(mnt
, -1);
757 /* caller will mntput() */
761 /* call under rcu_read_lock */
762 static bool legitimize_mnt(struct vfsmount
*bastard
, unsigned seq
)
764 int res
= __legitimize_mnt(bastard
, seq
);
767 if (unlikely(res
< 0)) {
776 * find the first mount at @dentry on vfsmount @mnt.
777 * call under rcu_read_lock()
779 struct mount
*__lookup_mnt(struct vfsmount
*mnt
, struct dentry
*dentry
)
781 struct hlist_head
*head
= m_hash(mnt
, dentry
);
784 hlist_for_each_entry_rcu(p
, head
, mnt_hash
)
785 if (&p
->mnt_parent
->mnt
== mnt
&& p
->mnt_mountpoint
== dentry
)
791 * lookup_mnt - Return the first child mount mounted at path
793 * "First" means first mounted chronologically. If you create the
796 * mount /dev/sda1 /mnt
797 * mount /dev/sda2 /mnt
798 * mount /dev/sda3 /mnt
800 * Then lookup_mnt() on the base /mnt dentry in the root mount will
801 * return successively the root dentry and vfsmount of /dev/sda1, then
802 * /dev/sda2, then /dev/sda3, then NULL.
804 * lookup_mnt takes a reference to the found vfsmount.
806 struct vfsmount
*lookup_mnt(const struct path
*path
)
808 struct mount
*child_mnt
;
814 seq
= read_seqbegin(&mount_lock
);
815 child_mnt
= __lookup_mnt(path
->mnt
, path
->dentry
);
816 m
= child_mnt
? &child_mnt
->mnt
: NULL
;
817 } while (!legitimize_mnt(m
, seq
));
822 static inline void lock_ns_list(struct mnt_namespace
*ns
)
824 spin_lock(&ns
->ns_lock
);
827 static inline void unlock_ns_list(struct mnt_namespace
*ns
)
829 spin_unlock(&ns
->ns_lock
);
832 static inline bool mnt_is_cursor(struct mount
*mnt
)
834 return mnt
->mnt
.mnt_flags
& MNT_CURSOR
;
838 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
839 * current mount namespace.
841 * The common case is dentries are not mountpoints at all and that
842 * test is handled inline. For the slow case when we are actually
843 * dealing with a mountpoint of some kind, walk through all of the
844 * mounts in the current mount namespace and test to see if the dentry
847 * The mount_hashtable is not usable in the context because we
848 * need to identify all mounts that may be in the current mount
849 * namespace not just a mount that happens to have some specified
852 bool __is_local_mountpoint(struct dentry
*dentry
)
854 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
856 bool is_covered
= false;
858 down_read(&namespace_sem
);
860 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
861 if (mnt_is_cursor(mnt
))
863 is_covered
= (mnt
->mnt_mountpoint
== dentry
);
868 up_read(&namespace_sem
);
873 static struct mountpoint
*lookup_mountpoint(struct dentry
*dentry
)
875 struct hlist_head
*chain
= mp_hash(dentry
);
876 struct mountpoint
*mp
;
878 hlist_for_each_entry(mp
, chain
, m_hash
) {
879 if (mp
->m_dentry
== dentry
) {
887 static struct mountpoint
*get_mountpoint(struct dentry
*dentry
)
889 struct mountpoint
*mp
, *new = NULL
;
892 if (d_mountpoint(dentry
)) {
893 /* might be worth a WARN_ON() */
894 if (d_unlinked(dentry
))
895 return ERR_PTR(-ENOENT
);
897 read_seqlock_excl(&mount_lock
);
898 mp
= lookup_mountpoint(dentry
);
899 read_sequnlock_excl(&mount_lock
);
905 new = kmalloc(sizeof(struct mountpoint
), GFP_KERNEL
);
907 return ERR_PTR(-ENOMEM
);
910 /* Exactly one processes may set d_mounted */
911 ret
= d_set_mounted(dentry
);
913 /* Someone else set d_mounted? */
917 /* The dentry is not available as a mountpoint? */
922 /* Add the new mountpoint to the hash table */
923 read_seqlock_excl(&mount_lock
);
924 new->m_dentry
= dget(dentry
);
926 hlist_add_head(&new->m_hash
, mp_hash(dentry
));
927 INIT_HLIST_HEAD(&new->m_list
);
928 read_sequnlock_excl(&mount_lock
);
938 * vfsmount lock must be held. Additionally, the caller is responsible
939 * for serializing calls for given disposal list.
941 static void __put_mountpoint(struct mountpoint
*mp
, struct list_head
*list
)
943 if (!--mp
->m_count
) {
944 struct dentry
*dentry
= mp
->m_dentry
;
945 BUG_ON(!hlist_empty(&mp
->m_list
));
946 spin_lock(&dentry
->d_lock
);
947 dentry
->d_flags
&= ~DCACHE_MOUNTED
;
948 spin_unlock(&dentry
->d_lock
);
949 dput_to_list(dentry
, list
);
950 hlist_del(&mp
->m_hash
);
955 /* called with namespace_lock and vfsmount lock */
956 static void put_mountpoint(struct mountpoint
*mp
)
958 __put_mountpoint(mp
, &ex_mountpoints
);
961 static inline int check_mnt(struct mount
*mnt
)
963 return mnt
->mnt_ns
== current
->nsproxy
->mnt_ns
;
967 * vfsmount lock must be held for write
969 static void touch_mnt_namespace(struct mnt_namespace
*ns
)
973 wake_up_interruptible(&ns
->poll
);
978 * vfsmount lock must be held for write
980 static void __touch_mnt_namespace(struct mnt_namespace
*ns
)
982 if (ns
&& ns
->event
!= event
) {
984 wake_up_interruptible(&ns
->poll
);
989 * vfsmount lock must be held for write
991 static struct mountpoint
*unhash_mnt(struct mount
*mnt
)
993 struct mountpoint
*mp
;
994 mnt
->mnt_parent
= mnt
;
995 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
996 list_del_init(&mnt
->mnt_child
);
997 hlist_del_init_rcu(&mnt
->mnt_hash
);
998 hlist_del_init(&mnt
->mnt_mp_list
);
1005 * vfsmount lock must be held for write
1007 static void umount_mnt(struct mount
*mnt
)
1009 put_mountpoint(unhash_mnt(mnt
));
1013 * vfsmount lock must be held for write
1015 void mnt_set_mountpoint(struct mount
*mnt
,
1016 struct mountpoint
*mp
,
1017 struct mount
*child_mnt
)
1020 mnt_add_count(mnt
, 1); /* essentially, that's mntget */
1021 child_mnt
->mnt_mountpoint
= mp
->m_dentry
;
1022 child_mnt
->mnt_parent
= mnt
;
1023 child_mnt
->mnt_mp
= mp
;
1024 hlist_add_head(&child_mnt
->mnt_mp_list
, &mp
->m_list
);
1027 static void __attach_mnt(struct mount
*mnt
, struct mount
*parent
)
1029 hlist_add_head_rcu(&mnt
->mnt_hash
,
1030 m_hash(&parent
->mnt
, mnt
->mnt_mountpoint
));
1031 list_add_tail(&mnt
->mnt_child
, &parent
->mnt_mounts
);
1035 * vfsmount lock must be held for write
1037 static void attach_mnt(struct mount
*mnt
,
1038 struct mount
*parent
,
1039 struct mountpoint
*mp
)
1041 mnt_set_mountpoint(parent
, mp
, mnt
);
1042 __attach_mnt(mnt
, parent
);
1045 void mnt_change_mountpoint(struct mount
*parent
, struct mountpoint
*mp
, struct mount
*mnt
)
1047 struct mountpoint
*old_mp
= mnt
->mnt_mp
;
1048 struct mount
*old_parent
= mnt
->mnt_parent
;
1050 list_del_init(&mnt
->mnt_child
);
1051 hlist_del_init(&mnt
->mnt_mp_list
);
1052 hlist_del_init_rcu(&mnt
->mnt_hash
);
1054 attach_mnt(mnt
, parent
, mp
);
1056 put_mountpoint(old_mp
);
1057 mnt_add_count(old_parent
, -1);
1061 * vfsmount lock must be held for write
1063 static void commit_tree(struct mount
*mnt
)
1065 struct mount
*parent
= mnt
->mnt_parent
;
1068 struct mnt_namespace
*n
= parent
->mnt_ns
;
1070 BUG_ON(parent
== mnt
);
1072 list_add_tail(&head
, &mnt
->mnt_list
);
1073 list_for_each_entry(m
, &head
, mnt_list
)
1076 list_splice(&head
, n
->list
.prev
);
1078 n
->mounts
+= n
->pending_mounts
;
1079 n
->pending_mounts
= 0;
1081 __attach_mnt(mnt
, parent
);
1082 touch_mnt_namespace(n
);
1085 static struct mount
*next_mnt(struct mount
*p
, struct mount
*root
)
1087 struct list_head
*next
= p
->mnt_mounts
.next
;
1088 if (next
== &p
->mnt_mounts
) {
1092 next
= p
->mnt_child
.next
;
1093 if (next
!= &p
->mnt_parent
->mnt_mounts
)
1098 return list_entry(next
, struct mount
, mnt_child
);
1101 static struct mount
*skip_mnt_tree(struct mount
*p
)
1103 struct list_head
*prev
= p
->mnt_mounts
.prev
;
1104 while (prev
!= &p
->mnt_mounts
) {
1105 p
= list_entry(prev
, struct mount
, mnt_child
);
1106 prev
= p
->mnt_mounts
.prev
;
1112 * vfs_create_mount - Create a mount for a configured superblock
1113 * @fc: The configuration context with the superblock attached
1115 * Create a mount to an already configured superblock. If necessary, the
1116 * caller should invoke vfs_get_tree() before calling this.
1118 * Note that this does not attach the mount to anything.
1120 struct vfsmount
*vfs_create_mount(struct fs_context
*fc
)
1125 return ERR_PTR(-EINVAL
);
1127 mnt
= alloc_vfsmnt(fc
->source
?: "none");
1129 return ERR_PTR(-ENOMEM
);
1131 if (fc
->sb_flags
& SB_KERNMOUNT
)
1132 mnt
->mnt
.mnt_flags
= MNT_INTERNAL
;
1134 atomic_inc(&fc
->root
->d_sb
->s_active
);
1135 mnt
->mnt
.mnt_sb
= fc
->root
->d_sb
;
1136 mnt
->mnt
.mnt_root
= dget(fc
->root
);
1137 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1138 mnt
->mnt_parent
= mnt
;
1141 list_add_tail(&mnt
->mnt_instance
, &mnt
->mnt
.mnt_sb
->s_mounts
);
1142 unlock_mount_hash();
1145 EXPORT_SYMBOL(vfs_create_mount
);
1147 struct vfsmount
*fc_mount(struct fs_context
*fc
)
1149 int err
= vfs_get_tree(fc
);
1151 up_write(&fc
->root
->d_sb
->s_umount
);
1152 return vfs_create_mount(fc
);
1154 return ERR_PTR(err
);
1156 EXPORT_SYMBOL(fc_mount
);
1158 struct vfsmount
*vfs_kern_mount(struct file_system_type
*type
,
1159 int flags
, const char *name
,
1162 struct fs_context
*fc
;
1163 struct vfsmount
*mnt
;
1167 return ERR_PTR(-EINVAL
);
1169 fc
= fs_context_for_mount(type
, flags
);
1171 return ERR_CAST(fc
);
1174 ret
= vfs_parse_fs_string(fc
, "source",
1175 name
, strlen(name
));
1177 ret
= parse_monolithic_mount_data(fc
, data
);
1186 EXPORT_SYMBOL_GPL(vfs_kern_mount
);
1189 vfs_submount(const struct dentry
*mountpoint
, struct file_system_type
*type
,
1190 const char *name
, void *data
)
1192 /* Until it is worked out how to pass the user namespace
1193 * through from the parent mount to the submount don't support
1194 * unprivileged mounts with submounts.
1196 if (mountpoint
->d_sb
->s_user_ns
!= &init_user_ns
)
1197 return ERR_PTR(-EPERM
);
1199 return vfs_kern_mount(type
, SB_SUBMOUNT
, name
, data
);
1201 EXPORT_SYMBOL_GPL(vfs_submount
);
1203 static struct mount
*clone_mnt(struct mount
*old
, struct dentry
*root
,
1206 struct super_block
*sb
= old
->mnt
.mnt_sb
;
1210 mnt
= alloc_vfsmnt(old
->mnt_devname
);
1212 return ERR_PTR(-ENOMEM
);
1214 if (flag
& (CL_SLAVE
| CL_PRIVATE
| CL_SHARED_TO_SLAVE
))
1215 mnt
->mnt_group_id
= 0; /* not a peer of original */
1217 mnt
->mnt_group_id
= old
->mnt_group_id
;
1219 if ((flag
& CL_MAKE_SHARED
) && !mnt
->mnt_group_id
) {
1220 err
= mnt_alloc_group_id(mnt
);
1225 mnt
->mnt
.mnt_flags
= old
->mnt
.mnt_flags
;
1226 mnt
->mnt
.mnt_flags
&= ~(MNT_WRITE_HOLD
|MNT_MARKED
|MNT_INTERNAL
);
1228 atomic_inc(&sb
->s_active
);
1229 mnt
->mnt
.mnt_idmap
= mnt_idmap_get(mnt_idmap(&old
->mnt
));
1231 mnt
->mnt
.mnt_sb
= sb
;
1232 mnt
->mnt
.mnt_root
= dget(root
);
1233 mnt
->mnt_mountpoint
= mnt
->mnt
.mnt_root
;
1234 mnt
->mnt_parent
= mnt
;
1236 list_add_tail(&mnt
->mnt_instance
, &sb
->s_mounts
);
1237 unlock_mount_hash();
1239 if ((flag
& CL_SLAVE
) ||
1240 ((flag
& CL_SHARED_TO_SLAVE
) && IS_MNT_SHARED(old
))) {
1241 list_add(&mnt
->mnt_slave
, &old
->mnt_slave_list
);
1242 mnt
->mnt_master
= old
;
1243 CLEAR_MNT_SHARED(mnt
);
1244 } else if (!(flag
& CL_PRIVATE
)) {
1245 if ((flag
& CL_MAKE_SHARED
) || IS_MNT_SHARED(old
))
1246 list_add(&mnt
->mnt_share
, &old
->mnt_share
);
1247 if (IS_MNT_SLAVE(old
))
1248 list_add(&mnt
->mnt_slave
, &old
->mnt_slave
);
1249 mnt
->mnt_master
= old
->mnt_master
;
1251 CLEAR_MNT_SHARED(mnt
);
1253 if (flag
& CL_MAKE_SHARED
)
1254 set_mnt_shared(mnt
);
1256 /* stick the duplicate mount on the same expiry list
1257 * as the original if that was on one */
1258 if (flag
& CL_EXPIRE
) {
1259 if (!list_empty(&old
->mnt_expire
))
1260 list_add(&mnt
->mnt_expire
, &old
->mnt_expire
);
1268 return ERR_PTR(err
);
1271 static void cleanup_mnt(struct mount
*mnt
)
1273 struct hlist_node
*p
;
1276 * The warning here probably indicates that somebody messed
1277 * up a mnt_want/drop_write() pair. If this happens, the
1278 * filesystem was probably unable to make r/w->r/o transitions.
1279 * The locking used to deal with mnt_count decrement provides barriers,
1280 * so mnt_get_writers() below is safe.
1282 WARN_ON(mnt_get_writers(mnt
));
1283 if (unlikely(mnt
->mnt_pins
.first
))
1285 hlist_for_each_entry_safe(m
, p
, &mnt
->mnt_stuck_children
, mnt_umount
) {
1286 hlist_del(&m
->mnt_umount
);
1289 fsnotify_vfsmount_delete(&mnt
->mnt
);
1290 dput(mnt
->mnt
.mnt_root
);
1291 deactivate_super(mnt
->mnt
.mnt_sb
);
1293 call_rcu(&mnt
->mnt_rcu
, delayed_free_vfsmnt
);
1296 static void __cleanup_mnt(struct rcu_head
*head
)
1298 cleanup_mnt(container_of(head
, struct mount
, mnt_rcu
));
1301 static LLIST_HEAD(delayed_mntput_list
);
1302 static void delayed_mntput(struct work_struct
*unused
)
1304 struct llist_node
*node
= llist_del_all(&delayed_mntput_list
);
1305 struct mount
*m
, *t
;
1307 llist_for_each_entry_safe(m
, t
, node
, mnt_llist
)
1310 static DECLARE_DELAYED_WORK(delayed_mntput_work
, delayed_mntput
);
1312 static void mntput_no_expire(struct mount
*mnt
)
1318 if (likely(READ_ONCE(mnt
->mnt_ns
))) {
1320 * Since we don't do lock_mount_hash() here,
1321 * ->mnt_ns can change under us. However, if it's
1322 * non-NULL, then there's a reference that won't
1323 * be dropped until after an RCU delay done after
1324 * turning ->mnt_ns NULL. So if we observe it
1325 * non-NULL under rcu_read_lock(), the reference
1326 * we are dropping is not the final one.
1328 mnt_add_count(mnt
, -1);
1334 * make sure that if __legitimize_mnt() has not seen us grab
1335 * mount_lock, we'll see their refcount increment here.
1338 mnt_add_count(mnt
, -1);
1339 count
= mnt_get_count(mnt
);
1343 unlock_mount_hash();
1346 if (unlikely(mnt
->mnt
.mnt_flags
& MNT_DOOMED
)) {
1348 unlock_mount_hash();
1351 mnt
->mnt
.mnt_flags
|= MNT_DOOMED
;
1354 list_del(&mnt
->mnt_instance
);
1356 if (unlikely(!list_empty(&mnt
->mnt_mounts
))) {
1357 struct mount
*p
, *tmp
;
1358 list_for_each_entry_safe(p
, tmp
, &mnt
->mnt_mounts
, mnt_child
) {
1359 __put_mountpoint(unhash_mnt(p
), &list
);
1360 hlist_add_head(&p
->mnt_umount
, &mnt
->mnt_stuck_children
);
1363 unlock_mount_hash();
1364 shrink_dentry_list(&list
);
1366 if (likely(!(mnt
->mnt
.mnt_flags
& MNT_INTERNAL
))) {
1367 struct task_struct
*task
= current
;
1368 if (likely(!(task
->flags
& PF_KTHREAD
))) {
1369 init_task_work(&mnt
->mnt_rcu
, __cleanup_mnt
);
1370 if (!task_work_add(task
, &mnt
->mnt_rcu
, TWA_RESUME
))
1373 if (llist_add(&mnt
->mnt_llist
, &delayed_mntput_list
))
1374 schedule_delayed_work(&delayed_mntput_work
, 1);
1380 void mntput(struct vfsmount
*mnt
)
1383 struct mount
*m
= real_mount(mnt
);
1384 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1385 if (unlikely(m
->mnt_expiry_mark
))
1386 m
->mnt_expiry_mark
= 0;
1387 mntput_no_expire(m
);
1390 EXPORT_SYMBOL(mntput
);
1392 struct vfsmount
*mntget(struct vfsmount
*mnt
)
1395 mnt_add_count(real_mount(mnt
), 1);
1398 EXPORT_SYMBOL(mntget
);
1401 * path_is_mountpoint() - Check if path is a mount in the current namespace.
1402 * @path: path to check
1404 * d_mountpoint() can only be used reliably to establish if a dentry is
1405 * not mounted in any namespace and that common case is handled inline.
1406 * d_mountpoint() isn't aware of the possibility there may be multiple
1407 * mounts using a given dentry in a different namespace. This function
1408 * checks if the passed in path is a mountpoint rather than the dentry
1411 bool path_is_mountpoint(const struct path
*path
)
1416 if (!d_mountpoint(path
->dentry
))
1421 seq
= read_seqbegin(&mount_lock
);
1422 res
= __path_is_mountpoint(path
);
1423 } while (read_seqretry(&mount_lock
, seq
));
1428 EXPORT_SYMBOL(path_is_mountpoint
);
1430 struct vfsmount
*mnt_clone_internal(const struct path
*path
)
1433 p
= clone_mnt(real_mount(path
->mnt
), path
->dentry
, CL_PRIVATE
);
1436 p
->mnt
.mnt_flags
|= MNT_INTERNAL
;
1440 #ifdef CONFIG_PROC_FS
1441 static struct mount
*mnt_list_next(struct mnt_namespace
*ns
,
1442 struct list_head
*p
)
1444 struct mount
*mnt
, *ret
= NULL
;
1447 list_for_each_continue(p
, &ns
->list
) {
1448 mnt
= list_entry(p
, typeof(*mnt
), mnt_list
);
1449 if (!mnt_is_cursor(mnt
)) {
1459 /* iterator; we want it to have access to namespace_sem, thus here... */
1460 static void *m_start(struct seq_file
*m
, loff_t
*pos
)
1462 struct proc_mounts
*p
= m
->private;
1463 struct list_head
*prev
;
1465 down_read(&namespace_sem
);
1467 prev
= &p
->ns
->list
;
1469 prev
= &p
->cursor
.mnt_list
;
1471 /* Read after we'd reached the end? */
1472 if (list_empty(prev
))
1476 return mnt_list_next(p
->ns
, prev
);
1479 static void *m_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
1481 struct proc_mounts
*p
= m
->private;
1482 struct mount
*mnt
= v
;
1485 return mnt_list_next(p
->ns
, &mnt
->mnt_list
);
1488 static void m_stop(struct seq_file
*m
, void *v
)
1490 struct proc_mounts
*p
= m
->private;
1491 struct mount
*mnt
= v
;
1493 lock_ns_list(p
->ns
);
1495 list_move_tail(&p
->cursor
.mnt_list
, &mnt
->mnt_list
);
1497 list_del_init(&p
->cursor
.mnt_list
);
1498 unlock_ns_list(p
->ns
);
1499 up_read(&namespace_sem
);
1502 static int m_show(struct seq_file
*m
, void *v
)
1504 struct proc_mounts
*p
= m
->private;
1505 struct mount
*r
= v
;
1506 return p
->show(m
, &r
->mnt
);
1509 const struct seq_operations mounts_op
= {
1516 void mnt_cursor_del(struct mnt_namespace
*ns
, struct mount
*cursor
)
1518 down_read(&namespace_sem
);
1520 list_del(&cursor
->mnt_list
);
1522 up_read(&namespace_sem
);
1524 #endif /* CONFIG_PROC_FS */
1527 * may_umount_tree - check if a mount tree is busy
1528 * @m: root of mount tree
1530 * This is called to check if a tree of mounts has any
1531 * open files, pwds, chroots or sub mounts that are
1534 int may_umount_tree(struct vfsmount
*m
)
1536 struct mount
*mnt
= real_mount(m
);
1537 int actual_refs
= 0;
1538 int minimum_refs
= 0;
1542 /* write lock needed for mnt_get_count */
1544 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1545 actual_refs
+= mnt_get_count(p
);
1548 unlock_mount_hash();
1550 if (actual_refs
> minimum_refs
)
1556 EXPORT_SYMBOL(may_umount_tree
);
1559 * may_umount - check if a mount point is busy
1560 * @mnt: root of mount
1562 * This is called to check if a mount point has any
1563 * open files, pwds, chroots or sub mounts. If the
1564 * mount has sub mounts this will return busy
1565 * regardless of whether the sub mounts are busy.
1567 * Doesn't take quota and stuff into account. IOW, in some cases it will
1568 * give false negatives. The main reason why it's here is that we need
1569 * a non-destructive way to look for easily umountable filesystems.
1571 int may_umount(struct vfsmount
*mnt
)
1574 down_read(&namespace_sem
);
1576 if (propagate_mount_busy(real_mount(mnt
), 2))
1578 unlock_mount_hash();
1579 up_read(&namespace_sem
);
1583 EXPORT_SYMBOL(may_umount
);
1585 static void namespace_unlock(void)
1587 struct hlist_head head
;
1588 struct hlist_node
*p
;
1592 hlist_move_list(&unmounted
, &head
);
1593 list_splice_init(&ex_mountpoints
, &list
);
1595 up_write(&namespace_sem
);
1597 shrink_dentry_list(&list
);
1599 if (likely(hlist_empty(&head
)))
1602 synchronize_rcu_expedited();
1604 hlist_for_each_entry_safe(m
, p
, &head
, mnt_umount
) {
1605 hlist_del(&m
->mnt_umount
);
1610 static inline void namespace_lock(void)
1612 down_write(&namespace_sem
);
1615 enum umount_tree_flags
{
1617 UMOUNT_PROPAGATE
= 2,
1618 UMOUNT_CONNECTED
= 4,
1621 static bool disconnect_mount(struct mount
*mnt
, enum umount_tree_flags how
)
1623 /* Leaving mounts connected is only valid for lazy umounts */
1624 if (how
& UMOUNT_SYNC
)
1627 /* A mount without a parent has nothing to be connected to */
1628 if (!mnt_has_parent(mnt
))
1631 /* Because the reference counting rules change when mounts are
1632 * unmounted and connected, umounted mounts may not be
1633 * connected to mounted mounts.
1635 if (!(mnt
->mnt_parent
->mnt
.mnt_flags
& MNT_UMOUNT
))
1638 /* Has it been requested that the mount remain connected? */
1639 if (how
& UMOUNT_CONNECTED
)
1642 /* Is the mount locked such that it needs to remain connected? */
1643 if (IS_MNT_LOCKED(mnt
))
1646 /* By default disconnect the mount */
1651 * mount_lock must be held
1652 * namespace_sem must be held for write
1654 static void umount_tree(struct mount
*mnt
, enum umount_tree_flags how
)
1656 LIST_HEAD(tmp_list
);
1659 if (how
& UMOUNT_PROPAGATE
)
1660 propagate_mount_unlock(mnt
);
1662 /* Gather the mounts to umount */
1663 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
1664 p
->mnt
.mnt_flags
|= MNT_UMOUNT
;
1665 list_move(&p
->mnt_list
, &tmp_list
);
1668 /* Hide the mounts from mnt_mounts */
1669 list_for_each_entry(p
, &tmp_list
, mnt_list
) {
1670 list_del_init(&p
->mnt_child
);
1673 /* Add propogated mounts to the tmp_list */
1674 if (how
& UMOUNT_PROPAGATE
)
1675 propagate_umount(&tmp_list
);
1677 while (!list_empty(&tmp_list
)) {
1678 struct mnt_namespace
*ns
;
1680 p
= list_first_entry(&tmp_list
, struct mount
, mnt_list
);
1681 list_del_init(&p
->mnt_expire
);
1682 list_del_init(&p
->mnt_list
);
1686 __touch_mnt_namespace(ns
);
1689 if (how
& UMOUNT_SYNC
)
1690 p
->mnt
.mnt_flags
|= MNT_SYNC_UMOUNT
;
1692 disconnect
= disconnect_mount(p
, how
);
1693 if (mnt_has_parent(p
)) {
1694 mnt_add_count(p
->mnt_parent
, -1);
1696 /* Don't forget about p */
1697 list_add_tail(&p
->mnt_child
, &p
->mnt_parent
->mnt_mounts
);
1702 change_mnt_propagation(p
, MS_PRIVATE
);
1704 hlist_add_head(&p
->mnt_umount
, &unmounted
);
1708 static void shrink_submounts(struct mount
*mnt
);
1710 static int do_umount_root(struct super_block
*sb
)
1714 down_write(&sb
->s_umount
);
1715 if (!sb_rdonly(sb
)) {
1716 struct fs_context
*fc
;
1718 fc
= fs_context_for_reconfigure(sb
->s_root
, SB_RDONLY
,
1723 ret
= parse_monolithic_mount_data(fc
, NULL
);
1725 ret
= reconfigure_super(fc
);
1729 up_write(&sb
->s_umount
);
1733 static int do_umount(struct mount
*mnt
, int flags
)
1735 struct super_block
*sb
= mnt
->mnt
.mnt_sb
;
1738 retval
= security_sb_umount(&mnt
->mnt
, flags
);
1743 * Allow userspace to request a mountpoint be expired rather than
1744 * unmounting unconditionally. Unmount only happens if:
1745 * (1) the mark is already set (the mark is cleared by mntput())
1746 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1748 if (flags
& MNT_EXPIRE
) {
1749 if (&mnt
->mnt
== current
->fs
->root
.mnt
||
1750 flags
& (MNT_FORCE
| MNT_DETACH
))
1754 * probably don't strictly need the lock here if we examined
1755 * all race cases, but it's a slowpath.
1758 if (mnt_get_count(mnt
) != 2) {
1759 unlock_mount_hash();
1762 unlock_mount_hash();
1764 if (!xchg(&mnt
->mnt_expiry_mark
, 1))
1769 * If we may have to abort operations to get out of this
1770 * mount, and they will themselves hold resources we must
1771 * allow the fs to do things. In the Unix tradition of
1772 * 'Gee thats tricky lets do it in userspace' the umount_begin
1773 * might fail to complete on the first run through as other tasks
1774 * must return, and the like. Thats for the mount program to worry
1775 * about for the moment.
1778 if (flags
& MNT_FORCE
&& sb
->s_op
->umount_begin
) {
1779 sb
->s_op
->umount_begin(sb
);
1783 * No sense to grab the lock for this test, but test itself looks
1784 * somewhat bogus. Suggestions for better replacement?
1785 * Ho-hum... In principle, we might treat that as umount + switch
1786 * to rootfs. GC would eventually take care of the old vfsmount.
1787 * Actually it makes sense, especially if rootfs would contain a
1788 * /reboot - static binary that would close all descriptors and
1789 * call reboot(9). Then init(8) could umount root and exec /reboot.
1791 if (&mnt
->mnt
== current
->fs
->root
.mnt
&& !(flags
& MNT_DETACH
)) {
1793 * Special case for "unmounting" root ...
1794 * we just try to remount it readonly.
1796 if (!ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
))
1798 return do_umount_root(sb
);
1804 /* Recheck MNT_LOCKED with the locks held */
1806 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
1810 if (flags
& MNT_DETACH
) {
1811 if (!list_empty(&mnt
->mnt_list
))
1812 umount_tree(mnt
, UMOUNT_PROPAGATE
);
1815 shrink_submounts(mnt
);
1817 if (!propagate_mount_busy(mnt
, 2)) {
1818 if (!list_empty(&mnt
->mnt_list
))
1819 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
1824 unlock_mount_hash();
1830 * __detach_mounts - lazily unmount all mounts on the specified dentry
1832 * During unlink, rmdir, and d_drop it is possible to loose the path
1833 * to an existing mountpoint, and wind up leaking the mount.
1834 * detach_mounts allows lazily unmounting those mounts instead of
1837 * The caller may hold dentry->d_inode->i_mutex.
1839 void __detach_mounts(struct dentry
*dentry
)
1841 struct mountpoint
*mp
;
1846 mp
= lookup_mountpoint(dentry
);
1851 while (!hlist_empty(&mp
->m_list
)) {
1852 mnt
= hlist_entry(mp
->m_list
.first
, struct mount
, mnt_mp_list
);
1853 if (mnt
->mnt
.mnt_flags
& MNT_UMOUNT
) {
1855 hlist_add_head(&mnt
->mnt_umount
, &unmounted
);
1857 else umount_tree(mnt
, UMOUNT_CONNECTED
);
1861 unlock_mount_hash();
1866 * Is the caller allowed to modify his namespace?
1868 bool may_mount(void)
1870 return ns_capable(current
->nsproxy
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
);
1873 static void warn_mandlock(void)
1875 pr_warn_once("=======================================================\n"
1876 "WARNING: The mand mount option has been deprecated and\n"
1877 " and is ignored by this kernel. Remove the mand\n"
1878 " option from the mount to silence this warning.\n"
1879 "=======================================================\n");
1882 static int can_umount(const struct path
*path
, int flags
)
1884 struct mount
*mnt
= real_mount(path
->mnt
);
1888 if (path
->dentry
!= path
->mnt
->mnt_root
)
1890 if (!check_mnt(mnt
))
1892 if (mnt
->mnt
.mnt_flags
& MNT_LOCKED
) /* Check optimistically */
1894 if (flags
& MNT_FORCE
&& !capable(CAP_SYS_ADMIN
))
1899 // caller is responsible for flags being sane
1900 int path_umount(struct path
*path
, int flags
)
1902 struct mount
*mnt
= real_mount(path
->mnt
);
1905 ret
= can_umount(path
, flags
);
1907 ret
= do_umount(mnt
, flags
);
1909 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1911 mntput_no_expire(mnt
);
1915 static int ksys_umount(char __user
*name
, int flags
)
1917 int lookup_flags
= LOOKUP_MOUNTPOINT
;
1921 // basic validity checks done first
1922 if (flags
& ~(MNT_FORCE
| MNT_DETACH
| MNT_EXPIRE
| UMOUNT_NOFOLLOW
))
1925 if (!(flags
& UMOUNT_NOFOLLOW
))
1926 lookup_flags
|= LOOKUP_FOLLOW
;
1927 ret
= user_path_at(AT_FDCWD
, name
, lookup_flags
, &path
);
1930 return path_umount(&path
, flags
);
1933 SYSCALL_DEFINE2(umount
, char __user
*, name
, int, flags
)
1935 return ksys_umount(name
, flags
);
1938 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1941 * The 2.0 compatible umount. No flags.
1943 SYSCALL_DEFINE1(oldumount
, char __user
*, name
)
1945 return ksys_umount(name
, 0);
1950 static bool is_mnt_ns_file(struct dentry
*dentry
)
1952 /* Is this a proxy for a mount namespace? */
1953 return dentry
->d_op
== &ns_dentry_operations
&&
1954 dentry
->d_fsdata
== &mntns_operations
;
1957 static struct mnt_namespace
*to_mnt_ns(struct ns_common
*ns
)
1959 return container_of(ns
, struct mnt_namespace
, ns
);
1962 struct ns_common
*from_mnt_ns(struct mnt_namespace
*mnt
)
1967 static bool mnt_ns_loop(struct dentry
*dentry
)
1969 /* Could bind mounting the mount namespace inode cause a
1970 * mount namespace loop?
1972 struct mnt_namespace
*mnt_ns
;
1973 if (!is_mnt_ns_file(dentry
))
1976 mnt_ns
= to_mnt_ns(get_proc_ns(dentry
->d_inode
));
1977 return current
->nsproxy
->mnt_ns
->seq
>= mnt_ns
->seq
;
1980 struct mount
*copy_tree(struct mount
*mnt
, struct dentry
*dentry
,
1983 struct mount
*res
, *p
, *q
, *r
, *parent
;
1985 if (!(flag
& CL_COPY_UNBINDABLE
) && IS_MNT_UNBINDABLE(mnt
))
1986 return ERR_PTR(-EINVAL
);
1988 if (!(flag
& CL_COPY_MNT_NS_FILE
) && is_mnt_ns_file(dentry
))
1989 return ERR_PTR(-EINVAL
);
1991 res
= q
= clone_mnt(mnt
, dentry
, flag
);
1995 q
->mnt_mountpoint
= mnt
->mnt_mountpoint
;
1998 list_for_each_entry(r
, &mnt
->mnt_mounts
, mnt_child
) {
2000 if (!is_subdir(r
->mnt_mountpoint
, dentry
))
2003 for (s
= r
; s
; s
= next_mnt(s
, r
)) {
2004 if (!(flag
& CL_COPY_UNBINDABLE
) &&
2005 IS_MNT_UNBINDABLE(s
)) {
2006 if (s
->mnt
.mnt_flags
& MNT_LOCKED
) {
2007 /* Both unbindable and locked. */
2008 q
= ERR_PTR(-EPERM
);
2011 s
= skip_mnt_tree(s
);
2015 if (!(flag
& CL_COPY_MNT_NS_FILE
) &&
2016 is_mnt_ns_file(s
->mnt
.mnt_root
)) {
2017 s
= skip_mnt_tree(s
);
2020 while (p
!= s
->mnt_parent
) {
2026 q
= clone_mnt(p
, p
->mnt
.mnt_root
, flag
);
2030 list_add_tail(&q
->mnt_list
, &res
->mnt_list
);
2031 attach_mnt(q
, parent
, p
->mnt_mp
);
2032 unlock_mount_hash();
2039 umount_tree(res
, UMOUNT_SYNC
);
2040 unlock_mount_hash();
2045 /* Caller should check returned pointer for errors */
2047 struct vfsmount
*collect_mounts(const struct path
*path
)
2051 if (!check_mnt(real_mount(path
->mnt
)))
2052 tree
= ERR_PTR(-EINVAL
);
2054 tree
= copy_tree(real_mount(path
->mnt
), path
->dentry
,
2055 CL_COPY_ALL
| CL_PRIVATE
);
2058 return ERR_CAST(tree
);
2062 static void free_mnt_ns(struct mnt_namespace
*);
2063 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*, bool);
2065 void dissolve_on_fput(struct vfsmount
*mnt
)
2067 struct mnt_namespace
*ns
;
2070 ns
= real_mount(mnt
)->mnt_ns
;
2073 umount_tree(real_mount(mnt
), UMOUNT_CONNECTED
);
2077 unlock_mount_hash();
2083 void drop_collected_mounts(struct vfsmount
*mnt
)
2087 umount_tree(real_mount(mnt
), 0);
2088 unlock_mount_hash();
2092 static bool has_locked_children(struct mount
*mnt
, struct dentry
*dentry
)
2094 struct mount
*child
;
2096 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
2097 if (!is_subdir(child
->mnt_mountpoint
, dentry
))
2100 if (child
->mnt
.mnt_flags
& MNT_LOCKED
)
2107 * clone_private_mount - create a private clone of a path
2108 * @path: path to clone
2110 * This creates a new vfsmount, which will be the clone of @path. The new mount
2111 * will not be attached anywhere in the namespace and will be private (i.e.
2112 * changes to the originating mount won't be propagated into this).
2114 * Release with mntput().
2116 struct vfsmount
*clone_private_mount(const struct path
*path
)
2118 struct mount
*old_mnt
= real_mount(path
->mnt
);
2119 struct mount
*new_mnt
;
2121 down_read(&namespace_sem
);
2122 if (IS_MNT_UNBINDABLE(old_mnt
))
2125 if (!check_mnt(old_mnt
))
2128 if (has_locked_children(old_mnt
, path
->dentry
))
2131 new_mnt
= clone_mnt(old_mnt
, path
->dentry
, CL_PRIVATE
);
2132 up_read(&namespace_sem
);
2134 if (IS_ERR(new_mnt
))
2135 return ERR_CAST(new_mnt
);
2137 /* Longterm mount to be removed by kern_unmount*() */
2138 new_mnt
->mnt_ns
= MNT_NS_INTERNAL
;
2140 return &new_mnt
->mnt
;
2143 up_read(&namespace_sem
);
2144 return ERR_PTR(-EINVAL
);
2146 EXPORT_SYMBOL_GPL(clone_private_mount
);
2148 int iterate_mounts(int (*f
)(struct vfsmount
*, void *), void *arg
,
2149 struct vfsmount
*root
)
2152 int res
= f(root
, arg
);
2155 list_for_each_entry(mnt
, &real_mount(root
)->mnt_list
, mnt_list
) {
2156 res
= f(&mnt
->mnt
, arg
);
2163 static void lock_mnt_tree(struct mount
*mnt
)
2167 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2168 int flags
= p
->mnt
.mnt_flags
;
2169 /* Don't allow unprivileged users to change mount flags */
2170 flags
|= MNT_LOCK_ATIME
;
2172 if (flags
& MNT_READONLY
)
2173 flags
|= MNT_LOCK_READONLY
;
2175 if (flags
& MNT_NODEV
)
2176 flags
|= MNT_LOCK_NODEV
;
2178 if (flags
& MNT_NOSUID
)
2179 flags
|= MNT_LOCK_NOSUID
;
2181 if (flags
& MNT_NOEXEC
)
2182 flags
|= MNT_LOCK_NOEXEC
;
2183 /* Don't allow unprivileged users to reveal what is under a mount */
2184 if (list_empty(&p
->mnt_expire
))
2185 flags
|= MNT_LOCKED
;
2186 p
->mnt
.mnt_flags
= flags
;
2190 static void cleanup_group_ids(struct mount
*mnt
, struct mount
*end
)
2194 for (p
= mnt
; p
!= end
; p
= next_mnt(p
, mnt
)) {
2195 if (p
->mnt_group_id
&& !IS_MNT_SHARED(p
))
2196 mnt_release_group_id(p
);
2200 static int invent_group_ids(struct mount
*mnt
, bool recurse
)
2204 for (p
= mnt
; p
; p
= recurse
? next_mnt(p
, mnt
) : NULL
) {
2205 if (!p
->mnt_group_id
&& !IS_MNT_SHARED(p
)) {
2206 int err
= mnt_alloc_group_id(p
);
2208 cleanup_group_ids(mnt
, p
);
2217 int count_mounts(struct mnt_namespace
*ns
, struct mount
*mnt
)
2219 unsigned int max
= READ_ONCE(sysctl_mount_max
);
2220 unsigned int mounts
= 0;
2223 if (ns
->mounts
>= max
)
2226 if (ns
->pending_mounts
>= max
)
2228 max
-= ns
->pending_mounts
;
2230 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
))
2236 ns
->pending_mounts
+= mounts
;
2241 * @source_mnt : mount tree to be attached
2242 * @nd : place the mount tree @source_mnt is attached
2243 * @parent_nd : if non-null, detach the source_mnt from its parent and
2244 * store the parent mount and mountpoint dentry.
2245 * (done when source_mnt is moved)
2247 * NOTE: in the table below explains the semantics when a source mount
2248 * of a given type is attached to a destination mount of a given type.
2249 * ---------------------------------------------------------------------------
2250 * | BIND MOUNT OPERATION |
2251 * |**************************************************************************
2252 * | source-->| shared | private | slave | unbindable |
2256 * |**************************************************************************
2257 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
2259 * |non-shared| shared (+) | private | slave (*) | invalid |
2260 * ***************************************************************************
2261 * A bind operation clones the source mount and mounts the clone on the
2262 * destination mount.
2264 * (++) the cloned mount is propagated to all the mounts in the propagation
2265 * tree of the destination mount and the cloned mount is added to
2266 * the peer group of the source mount.
2267 * (+) the cloned mount is created under the destination mount and is marked
2268 * as shared. The cloned mount is added to the peer group of the source
2270 * (+++) the mount is propagated to all the mounts in the propagation tree
2271 * of the destination mount and the cloned mount is made slave
2272 * of the same master as that of the source mount. The cloned mount
2273 * is marked as 'shared and slave'.
2274 * (*) the cloned mount is made a slave of the same master as that of the
2277 * ---------------------------------------------------------------------------
2278 * | MOVE MOUNT OPERATION |
2279 * |**************************************************************************
2280 * | source-->| shared | private | slave | unbindable |
2284 * |**************************************************************************
2285 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2287 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2288 * ***************************************************************************
2290 * (+) the mount is moved to the destination. And is then propagated to
2291 * all the mounts in the propagation tree of the destination mount.
2292 * (+*) the mount is moved to the destination.
2293 * (+++) the mount is moved to the destination and is then propagated to
2294 * all the mounts belonging to the destination mount's propagation tree.
2295 * the mount is marked as 'shared and slave'.
2296 * (*) the mount continues to be a slave at the new location.
2298 * if the source mount is a tree, the operations explained above is
2299 * applied to each mount in the tree.
2300 * Must be called without spinlocks held, since this function can sleep
2303 static int attach_recursive_mnt(struct mount
*source_mnt
,
2304 struct mount
*dest_mnt
,
2305 struct mountpoint
*dest_mp
,
2308 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2309 HLIST_HEAD(tree_list
);
2310 struct mnt_namespace
*ns
= dest_mnt
->mnt_ns
;
2311 struct mountpoint
*smp
;
2312 struct mount
*child
, *p
;
2313 struct hlist_node
*n
;
2316 /* Preallocate a mountpoint in case the new mounts need
2317 * to be tucked under other mounts.
2319 smp
= get_mountpoint(source_mnt
->mnt
.mnt_root
);
2321 return PTR_ERR(smp
);
2323 /* Is there space to add these mounts to the mount namespace? */
2325 err
= count_mounts(ns
, source_mnt
);
2330 if (IS_MNT_SHARED(dest_mnt
)) {
2331 err
= invent_group_ids(source_mnt
, true);
2334 err
= propagate_mnt(dest_mnt
, dest_mp
, source_mnt
, &tree_list
);
2337 goto out_cleanup_ids
;
2338 for (p
= source_mnt
; p
; p
= next_mnt(p
, source_mnt
))
2344 unhash_mnt(source_mnt
);
2345 attach_mnt(source_mnt
, dest_mnt
, dest_mp
);
2346 touch_mnt_namespace(source_mnt
->mnt_ns
);
2348 if (source_mnt
->mnt_ns
) {
2349 /* move from anon - the caller will destroy */
2350 list_del_init(&source_mnt
->mnt_ns
->list
);
2352 mnt_set_mountpoint(dest_mnt
, dest_mp
, source_mnt
);
2353 commit_tree(source_mnt
);
2356 hlist_for_each_entry_safe(child
, n
, &tree_list
, mnt_hash
) {
2358 hlist_del_init(&child
->mnt_hash
);
2359 q
= __lookup_mnt(&child
->mnt_parent
->mnt
,
2360 child
->mnt_mountpoint
);
2362 mnt_change_mountpoint(child
, smp
, q
);
2363 /* Notice when we are propagating across user namespaces */
2364 if (child
->mnt_parent
->mnt_ns
->user_ns
!= user_ns
)
2365 lock_mnt_tree(child
);
2366 child
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2369 put_mountpoint(smp
);
2370 unlock_mount_hash();
2375 while (!hlist_empty(&tree_list
)) {
2376 child
= hlist_entry(tree_list
.first
, struct mount
, mnt_hash
);
2377 child
->mnt_parent
->mnt_ns
->pending_mounts
= 0;
2378 umount_tree(child
, UMOUNT_SYNC
);
2380 unlock_mount_hash();
2381 cleanup_group_ids(source_mnt
, NULL
);
2383 ns
->pending_mounts
= 0;
2385 read_seqlock_excl(&mount_lock
);
2386 put_mountpoint(smp
);
2387 read_sequnlock_excl(&mount_lock
);
2392 static struct mountpoint
*lock_mount(struct path
*path
)
2394 struct vfsmount
*mnt
;
2395 struct dentry
*dentry
= path
->dentry
;
2397 inode_lock(dentry
->d_inode
);
2398 if (unlikely(cant_mount(dentry
))) {
2399 inode_unlock(dentry
->d_inode
);
2400 return ERR_PTR(-ENOENT
);
2403 mnt
= lookup_mnt(path
);
2405 struct mountpoint
*mp
= get_mountpoint(dentry
);
2408 inode_unlock(dentry
->d_inode
);
2414 inode_unlock(path
->dentry
->d_inode
);
2417 dentry
= path
->dentry
= dget(mnt
->mnt_root
);
2421 static void unlock_mount(struct mountpoint
*where
)
2423 struct dentry
*dentry
= where
->m_dentry
;
2425 read_seqlock_excl(&mount_lock
);
2426 put_mountpoint(where
);
2427 read_sequnlock_excl(&mount_lock
);
2430 inode_unlock(dentry
->d_inode
);
2433 static int graft_tree(struct mount
*mnt
, struct mount
*p
, struct mountpoint
*mp
)
2435 if (mnt
->mnt
.mnt_sb
->s_flags
& SB_NOUSER
)
2438 if (d_is_dir(mp
->m_dentry
) !=
2439 d_is_dir(mnt
->mnt
.mnt_root
))
2442 return attach_recursive_mnt(mnt
, p
, mp
, false);
2446 * Sanity check the flags to change_mnt_propagation.
2449 static int flags_to_propagation_type(int ms_flags
)
2451 int type
= ms_flags
& ~(MS_REC
| MS_SILENT
);
2453 /* Fail if any non-propagation flags are set */
2454 if (type
& ~(MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
2456 /* Only one propagation flag should be set */
2457 if (!is_power_of_2(type
))
2463 * recursively change the type of the mountpoint.
2465 static int do_change_type(struct path
*path
, int ms_flags
)
2468 struct mount
*mnt
= real_mount(path
->mnt
);
2469 int recurse
= ms_flags
& MS_REC
;
2473 if (path
->dentry
!= path
->mnt
->mnt_root
)
2476 type
= flags_to_propagation_type(ms_flags
);
2481 if (type
== MS_SHARED
) {
2482 err
= invent_group_ids(mnt
, recurse
);
2488 for (m
= mnt
; m
; m
= (recurse
? next_mnt(m
, mnt
) : NULL
))
2489 change_mnt_propagation(m
, type
);
2490 unlock_mount_hash();
2497 static struct mount
*__do_loopback(struct path
*old_path
, int recurse
)
2499 struct mount
*mnt
= ERR_PTR(-EINVAL
), *old
= real_mount(old_path
->mnt
);
2501 if (IS_MNT_UNBINDABLE(old
))
2504 if (!check_mnt(old
) && old_path
->dentry
->d_op
!= &ns_dentry_operations
)
2507 if (!recurse
&& has_locked_children(old
, old_path
->dentry
))
2511 mnt
= copy_tree(old
, old_path
->dentry
, CL_COPY_MNT_NS_FILE
);
2513 mnt
= clone_mnt(old
, old_path
->dentry
, 0);
2516 mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
2522 * do loopback mount.
2524 static int do_loopback(struct path
*path
, const char *old_name
,
2527 struct path old_path
;
2528 struct mount
*mnt
= NULL
, *parent
;
2529 struct mountpoint
*mp
;
2531 if (!old_name
|| !*old_name
)
2533 err
= kern_path(old_name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &old_path
);
2538 if (mnt_ns_loop(old_path
.dentry
))
2541 mp
= lock_mount(path
);
2547 parent
= real_mount(path
->mnt
);
2548 if (!check_mnt(parent
))
2551 mnt
= __do_loopback(&old_path
, recurse
);
2557 err
= graft_tree(mnt
, parent
, mp
);
2560 umount_tree(mnt
, UMOUNT_SYNC
);
2561 unlock_mount_hash();
2566 path_put(&old_path
);
2570 static struct file
*open_detached_copy(struct path
*path
, bool recursive
)
2572 struct user_namespace
*user_ns
= current
->nsproxy
->mnt_ns
->user_ns
;
2573 struct mnt_namespace
*ns
= alloc_mnt_ns(user_ns
, true);
2574 struct mount
*mnt
, *p
;
2578 return ERR_CAST(ns
);
2581 mnt
= __do_loopback(path
, recursive
);
2585 return ERR_CAST(mnt
);
2589 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2594 list_add_tail(&ns
->list
, &mnt
->mnt_list
);
2596 unlock_mount_hash();
2600 path
->mnt
= &mnt
->mnt
;
2601 file
= dentry_open(path
, O_PATH
, current_cred());
2603 dissolve_on_fput(path
->mnt
);
2605 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
2609 SYSCALL_DEFINE3(open_tree
, int, dfd
, const char __user
*, filename
, unsigned, flags
)
2613 int lookup_flags
= LOOKUP_AUTOMOUNT
| LOOKUP_FOLLOW
;
2614 bool detached
= flags
& OPEN_TREE_CLONE
;
2618 BUILD_BUG_ON(OPEN_TREE_CLOEXEC
!= O_CLOEXEC
);
2620 if (flags
& ~(AT_EMPTY_PATH
| AT_NO_AUTOMOUNT
| AT_RECURSIVE
|
2621 AT_SYMLINK_NOFOLLOW
| OPEN_TREE_CLONE
|
2625 if ((flags
& (AT_RECURSIVE
| OPEN_TREE_CLONE
)) == AT_RECURSIVE
)
2628 if (flags
& AT_NO_AUTOMOUNT
)
2629 lookup_flags
&= ~LOOKUP_AUTOMOUNT
;
2630 if (flags
& AT_SYMLINK_NOFOLLOW
)
2631 lookup_flags
&= ~LOOKUP_FOLLOW
;
2632 if (flags
& AT_EMPTY_PATH
)
2633 lookup_flags
|= LOOKUP_EMPTY
;
2635 if (detached
&& !may_mount())
2638 fd
= get_unused_fd_flags(flags
& O_CLOEXEC
);
2642 error
= user_path_at(dfd
, filename
, lookup_flags
, &path
);
2643 if (unlikely(error
)) {
2644 file
= ERR_PTR(error
);
2647 file
= open_detached_copy(&path
, flags
& AT_RECURSIVE
);
2649 file
= dentry_open(&path
, O_PATH
, current_cred());
2654 return PTR_ERR(file
);
2656 fd_install(fd
, file
);
2661 * Don't allow locked mount flags to be cleared.
2663 * No locks need to be held here while testing the various MNT_LOCK
2664 * flags because those flags can never be cleared once they are set.
2666 static bool can_change_locked_flags(struct mount
*mnt
, unsigned int mnt_flags
)
2668 unsigned int fl
= mnt
->mnt
.mnt_flags
;
2670 if ((fl
& MNT_LOCK_READONLY
) &&
2671 !(mnt_flags
& MNT_READONLY
))
2674 if ((fl
& MNT_LOCK_NODEV
) &&
2675 !(mnt_flags
& MNT_NODEV
))
2678 if ((fl
& MNT_LOCK_NOSUID
) &&
2679 !(mnt_flags
& MNT_NOSUID
))
2682 if ((fl
& MNT_LOCK_NOEXEC
) &&
2683 !(mnt_flags
& MNT_NOEXEC
))
2686 if ((fl
& MNT_LOCK_ATIME
) &&
2687 ((fl
& MNT_ATIME_MASK
) != (mnt_flags
& MNT_ATIME_MASK
)))
2693 static int change_mount_ro_state(struct mount
*mnt
, unsigned int mnt_flags
)
2695 bool readonly_request
= (mnt_flags
& MNT_READONLY
);
2697 if (readonly_request
== __mnt_is_readonly(&mnt
->mnt
))
2700 if (readonly_request
)
2701 return mnt_make_readonly(mnt
);
2703 mnt
->mnt
.mnt_flags
&= ~MNT_READONLY
;
2707 static void set_mount_attributes(struct mount
*mnt
, unsigned int mnt_flags
)
2709 mnt_flags
|= mnt
->mnt
.mnt_flags
& ~MNT_USER_SETTABLE_MASK
;
2710 mnt
->mnt
.mnt_flags
= mnt_flags
;
2711 touch_mnt_namespace(mnt
->mnt_ns
);
2714 static void mnt_warn_timestamp_expiry(struct path
*mountpoint
, struct vfsmount
*mnt
)
2716 struct super_block
*sb
= mnt
->mnt_sb
;
2718 if (!__mnt_is_readonly(mnt
) &&
2719 (!(sb
->s_iflags
& SB_I_TS_EXPIRY_WARNED
)) &&
2720 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX
> sb
->s_time_max
)) {
2721 char *buf
= (char *)__get_free_page(GFP_KERNEL
);
2722 char *mntpath
= buf
? d_path(mountpoint
, buf
, PAGE_SIZE
) : ERR_PTR(-ENOMEM
);
2725 time64_to_tm(sb
->s_time_max
, 0, &tm
);
2727 pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n",
2729 is_mounted(mnt
) ? "remounted" : "mounted",
2731 tm
.tm_year
+1900, (unsigned long long)sb
->s_time_max
);
2733 free_page((unsigned long)buf
);
2734 sb
->s_iflags
|= SB_I_TS_EXPIRY_WARNED
;
2739 * Handle reconfiguration of the mountpoint only without alteration of the
2740 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2743 static int do_reconfigure_mnt(struct path
*path
, unsigned int mnt_flags
)
2745 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2746 struct mount
*mnt
= real_mount(path
->mnt
);
2749 if (!check_mnt(mnt
))
2752 if (path
->dentry
!= mnt
->mnt
.mnt_root
)
2755 if (!can_change_locked_flags(mnt
, mnt_flags
))
2759 * We're only checking whether the superblock is read-only not
2760 * changing it, so only take down_read(&sb->s_umount).
2762 down_read(&sb
->s_umount
);
2764 ret
= change_mount_ro_state(mnt
, mnt_flags
);
2766 set_mount_attributes(mnt
, mnt_flags
);
2767 unlock_mount_hash();
2768 up_read(&sb
->s_umount
);
2770 mnt_warn_timestamp_expiry(path
, &mnt
->mnt
);
2776 * change filesystem flags. dir should be a physical root of filesystem.
2777 * If you've mounted a non-root directory somewhere and want to do remount
2778 * on it - tough luck.
2780 static int do_remount(struct path
*path
, int ms_flags
, int sb_flags
,
2781 int mnt_flags
, void *data
)
2784 struct super_block
*sb
= path
->mnt
->mnt_sb
;
2785 struct mount
*mnt
= real_mount(path
->mnt
);
2786 struct fs_context
*fc
;
2788 if (!check_mnt(mnt
))
2791 if (path
->dentry
!= path
->mnt
->mnt_root
)
2794 if (!can_change_locked_flags(mnt
, mnt_flags
))
2797 fc
= fs_context_for_reconfigure(path
->dentry
, sb_flags
, MS_RMT_MASK
);
2802 err
= parse_monolithic_mount_data(fc
, data
);
2804 down_write(&sb
->s_umount
);
2806 if (ns_capable(sb
->s_user_ns
, CAP_SYS_ADMIN
)) {
2807 err
= reconfigure_super(fc
);
2810 set_mount_attributes(mnt
, mnt_flags
);
2811 unlock_mount_hash();
2814 up_write(&sb
->s_umount
);
2817 mnt_warn_timestamp_expiry(path
, &mnt
->mnt
);
2823 static inline int tree_contains_unbindable(struct mount
*mnt
)
2826 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
2827 if (IS_MNT_UNBINDABLE(p
))
2834 * Check that there aren't references to earlier/same mount namespaces in the
2835 * specified subtree. Such references can act as pins for mount namespaces
2836 * that aren't checked by the mount-cycle checking code, thereby allowing
2837 * cycles to be made.
2839 static bool check_for_nsfs_mounts(struct mount
*subtree
)
2845 for (p
= subtree
; p
; p
= next_mnt(p
, subtree
))
2846 if (mnt_ns_loop(p
->mnt
.mnt_root
))
2851 unlock_mount_hash();
2855 static int do_set_group(struct path
*from_path
, struct path
*to_path
)
2857 struct mount
*from
, *to
;
2860 from
= real_mount(from_path
->mnt
);
2861 to
= real_mount(to_path
->mnt
);
2866 /* To and From must be mounted */
2867 if (!is_mounted(&from
->mnt
))
2869 if (!is_mounted(&to
->mnt
))
2873 /* We should be allowed to modify mount namespaces of both mounts */
2874 if (!ns_capable(from
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
))
2876 if (!ns_capable(to
->mnt_ns
->user_ns
, CAP_SYS_ADMIN
))
2880 /* To and From paths should be mount roots */
2881 if (from_path
->dentry
!= from_path
->mnt
->mnt_root
)
2883 if (to_path
->dentry
!= to_path
->mnt
->mnt_root
)
2886 /* Setting sharing groups is only allowed across same superblock */
2887 if (from
->mnt
.mnt_sb
!= to
->mnt
.mnt_sb
)
2890 /* From mount root should be wider than To mount root */
2891 if (!is_subdir(to
->mnt
.mnt_root
, from
->mnt
.mnt_root
))
2894 /* From mount should not have locked children in place of To's root */
2895 if (has_locked_children(from
, to
->mnt
.mnt_root
))
2898 /* Setting sharing groups is only allowed on private mounts */
2899 if (IS_MNT_SHARED(to
) || IS_MNT_SLAVE(to
))
2902 /* From should not be private */
2903 if (!IS_MNT_SHARED(from
) && !IS_MNT_SLAVE(from
))
2906 if (IS_MNT_SLAVE(from
)) {
2907 struct mount
*m
= from
->mnt_master
;
2909 list_add(&to
->mnt_slave
, &m
->mnt_slave_list
);
2913 if (IS_MNT_SHARED(from
)) {
2914 to
->mnt_group_id
= from
->mnt_group_id
;
2915 list_add(&to
->mnt_share
, &from
->mnt_share
);
2918 unlock_mount_hash();
2927 static int do_move_mount(struct path
*old_path
, struct path
*new_path
)
2929 struct mnt_namespace
*ns
;
2932 struct mount
*parent
;
2933 struct mountpoint
*mp
, *old_mp
;
2937 mp
= lock_mount(new_path
);
2941 old
= real_mount(old_path
->mnt
);
2942 p
= real_mount(new_path
->mnt
);
2943 parent
= old
->mnt_parent
;
2944 attached
= mnt_has_parent(old
);
2945 old_mp
= old
->mnt_mp
;
2949 /* The mountpoint must be in our namespace. */
2953 /* The thing moved must be mounted... */
2954 if (!is_mounted(&old
->mnt
))
2957 /* ... and either ours or the root of anon namespace */
2958 if (!(attached
? check_mnt(old
) : is_anon_ns(ns
)))
2961 if (old
->mnt
.mnt_flags
& MNT_LOCKED
)
2964 if (old_path
->dentry
!= old_path
->mnt
->mnt_root
)
2967 if (d_is_dir(new_path
->dentry
) !=
2968 d_is_dir(old_path
->dentry
))
2971 * Don't move a mount residing in a shared parent.
2973 if (attached
&& IS_MNT_SHARED(parent
))
2976 * Don't move a mount tree containing unbindable mounts to a destination
2977 * mount which is shared.
2979 if (IS_MNT_SHARED(p
) && tree_contains_unbindable(old
))
2982 if (!check_for_nsfs_mounts(old
))
2984 for (; mnt_has_parent(p
); p
= p
->mnt_parent
)
2988 err
= attach_recursive_mnt(old
, real_mount(new_path
->mnt
), mp
,
2993 /* if the mount is moved, it should no longer be expire
2995 list_del_init(&old
->mnt_expire
);
2997 put_mountpoint(old_mp
);
3002 mntput_no_expire(parent
);
3009 static int do_move_mount_old(struct path
*path
, const char *old_name
)
3011 struct path old_path
;
3014 if (!old_name
|| !*old_name
)
3017 err
= kern_path(old_name
, LOOKUP_FOLLOW
, &old_path
);
3021 err
= do_move_mount(&old_path
, path
);
3022 path_put(&old_path
);
3027 * add a mount into a namespace's mount tree
3029 static int do_add_mount(struct mount
*newmnt
, struct mountpoint
*mp
,
3030 const struct path
*path
, int mnt_flags
)
3032 struct mount
*parent
= real_mount(path
->mnt
);
3034 mnt_flags
&= ~MNT_INTERNAL_FLAGS
;
3036 if (unlikely(!check_mnt(parent
))) {
3037 /* that's acceptable only for automounts done in private ns */
3038 if (!(mnt_flags
& MNT_SHRINKABLE
))
3040 /* ... and for those we'd better have mountpoint still alive */
3041 if (!parent
->mnt_ns
)
3045 /* Refuse the same filesystem on the same mount point */
3046 if (path
->mnt
->mnt_sb
== newmnt
->mnt
.mnt_sb
&&
3047 path
->mnt
->mnt_root
== path
->dentry
)
3050 if (d_is_symlink(newmnt
->mnt
.mnt_root
))
3053 newmnt
->mnt
.mnt_flags
= mnt_flags
;
3054 return graft_tree(newmnt
, parent
, mp
);
3057 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
);
3060 * Create a new mount using a superblock configuration and request it
3061 * be added to the namespace tree.
3063 static int do_new_mount_fc(struct fs_context
*fc
, struct path
*mountpoint
,
3064 unsigned int mnt_flags
)
3066 struct vfsmount
*mnt
;
3067 struct mountpoint
*mp
;
3068 struct super_block
*sb
= fc
->root
->d_sb
;
3071 error
= security_sb_kern_mount(sb
);
3072 if (!error
&& mount_too_revealing(sb
, &mnt_flags
))
3075 if (unlikely(error
)) {
3080 up_write(&sb
->s_umount
);
3082 mnt
= vfs_create_mount(fc
);
3084 return PTR_ERR(mnt
);
3086 mnt_warn_timestamp_expiry(mountpoint
, mnt
);
3088 mp
= lock_mount(mountpoint
);
3093 error
= do_add_mount(real_mount(mnt
), mp
, mountpoint
, mnt_flags
);
3101 * create a new mount for userspace and request it to be added into the
3104 static int do_new_mount(struct path
*path
, const char *fstype
, int sb_flags
,
3105 int mnt_flags
, const char *name
, void *data
)
3107 struct file_system_type
*type
;
3108 struct fs_context
*fc
;
3109 const char *subtype
= NULL
;
3115 type
= get_fs_type(fstype
);
3119 if (type
->fs_flags
& FS_HAS_SUBTYPE
) {
3120 subtype
= strchr(fstype
, '.');
3124 put_filesystem(type
);
3130 fc
= fs_context_for_mount(type
, sb_flags
);
3131 put_filesystem(type
);
3136 err
= vfs_parse_fs_string(fc
, "subtype",
3137 subtype
, strlen(subtype
));
3139 err
= vfs_parse_fs_string(fc
, "source", name
, strlen(name
));
3141 err
= parse_monolithic_mount_data(fc
, data
);
3142 if (!err
&& !mount_capable(fc
))
3145 err
= vfs_get_tree(fc
);
3147 err
= do_new_mount_fc(fc
, path
, mnt_flags
);
3153 int finish_automount(struct vfsmount
*m
, const struct path
*path
)
3155 struct dentry
*dentry
= path
->dentry
;
3156 struct mountpoint
*mp
;
3165 mnt
= real_mount(m
);
3166 /* The new mount record should have at least 2 refs to prevent it being
3167 * expired before we get a chance to add it
3169 BUG_ON(mnt_get_count(mnt
) < 2);
3171 if (m
->mnt_sb
== path
->mnt
->mnt_sb
&&
3172 m
->mnt_root
== dentry
) {
3178 * we don't want to use lock_mount() - in this case finding something
3179 * that overmounts our mountpoint to be means "quitely drop what we've
3180 * got", not "try to mount it on top".
3182 inode_lock(dentry
->d_inode
);
3184 if (unlikely(cant_mount(dentry
))) {
3186 goto discard_locked
;
3189 if (unlikely(__lookup_mnt(path
->mnt
, dentry
))) {
3192 goto discard_locked
;
3195 mp
= get_mountpoint(dentry
);
3198 goto discard_locked
;
3201 err
= do_add_mount(mnt
, mp
, path
, path
->mnt
->mnt_flags
| MNT_SHRINKABLE
);
3210 inode_unlock(dentry
->d_inode
);
3212 /* remove m from any expiration list it may be on */
3213 if (!list_empty(&mnt
->mnt_expire
)) {
3215 list_del_init(&mnt
->mnt_expire
);
3224 * mnt_set_expiry - Put a mount on an expiration list
3225 * @mnt: The mount to list.
3226 * @expiry_list: The list to add the mount to.
3228 void mnt_set_expiry(struct vfsmount
*mnt
, struct list_head
*expiry_list
)
3232 list_add_tail(&real_mount(mnt
)->mnt_expire
, expiry_list
);
3236 EXPORT_SYMBOL(mnt_set_expiry
);
3239 * process a list of expirable mountpoints with the intent of discarding any
3240 * mountpoints that aren't in use and haven't been touched since last we came
3243 void mark_mounts_for_expiry(struct list_head
*mounts
)
3245 struct mount
*mnt
, *next
;
3246 LIST_HEAD(graveyard
);
3248 if (list_empty(mounts
))
3254 /* extract from the expiration list every vfsmount that matches the
3255 * following criteria:
3256 * - only referenced by its parent vfsmount
3257 * - still marked for expiry (marked on the last call here; marks are
3258 * cleared by mntput())
3260 list_for_each_entry_safe(mnt
, next
, mounts
, mnt_expire
) {
3261 if (!xchg(&mnt
->mnt_expiry_mark
, 1) ||
3262 propagate_mount_busy(mnt
, 1))
3264 list_move(&mnt
->mnt_expire
, &graveyard
);
3266 while (!list_empty(&graveyard
)) {
3267 mnt
= list_first_entry(&graveyard
, struct mount
, mnt_expire
);
3268 touch_mnt_namespace(mnt
->mnt_ns
);
3269 umount_tree(mnt
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
3271 unlock_mount_hash();
3275 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry
);
3278 * Ripoff of 'select_parent()'
3280 * search the list of submounts for a given mountpoint, and move any
3281 * shrinkable submounts to the 'graveyard' list.
3283 static int select_submounts(struct mount
*parent
, struct list_head
*graveyard
)
3285 struct mount
*this_parent
= parent
;
3286 struct list_head
*next
;
3290 next
= this_parent
->mnt_mounts
.next
;
3292 while (next
!= &this_parent
->mnt_mounts
) {
3293 struct list_head
*tmp
= next
;
3294 struct mount
*mnt
= list_entry(tmp
, struct mount
, mnt_child
);
3297 if (!(mnt
->mnt
.mnt_flags
& MNT_SHRINKABLE
))
3300 * Descend a level if the d_mounts list is non-empty.
3302 if (!list_empty(&mnt
->mnt_mounts
)) {
3307 if (!propagate_mount_busy(mnt
, 1)) {
3308 list_move_tail(&mnt
->mnt_expire
, graveyard
);
3313 * All done at this level ... ascend and resume the search
3315 if (this_parent
!= parent
) {
3316 next
= this_parent
->mnt_child
.next
;
3317 this_parent
= this_parent
->mnt_parent
;
3324 * process a list of expirable mountpoints with the intent of discarding any
3325 * submounts of a specific parent mountpoint
3327 * mount_lock must be held for write
3329 static void shrink_submounts(struct mount
*mnt
)
3331 LIST_HEAD(graveyard
);
3334 /* extract submounts of 'mountpoint' from the expiration list */
3335 while (select_submounts(mnt
, &graveyard
)) {
3336 while (!list_empty(&graveyard
)) {
3337 m
= list_first_entry(&graveyard
, struct mount
,
3339 touch_mnt_namespace(m
->mnt_ns
);
3340 umount_tree(m
, UMOUNT_PROPAGATE
|UMOUNT_SYNC
);
3345 static void *copy_mount_options(const void __user
* data
)
3348 unsigned left
, offset
;
3353 copy
= kmalloc(PAGE_SIZE
, GFP_KERNEL
);
3355 return ERR_PTR(-ENOMEM
);
3357 left
= copy_from_user(copy
, data
, PAGE_SIZE
);
3360 * Not all architectures have an exact copy_from_user(). Resort to
3363 offset
= PAGE_SIZE
- left
;
3366 if (get_user(c
, (const char __user
*)data
+ offset
))
3373 if (left
== PAGE_SIZE
) {
3375 return ERR_PTR(-EFAULT
);
3381 static char *copy_mount_string(const void __user
*data
)
3383 return data
? strndup_user(data
, PATH_MAX
) : NULL
;
3387 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3388 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3390 * data is a (void *) that can point to any structure up to
3391 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3392 * information (or be NULL).
3394 * Pre-0.97 versions of mount() didn't have a flags word.
3395 * When the flags word was introduced its top half was required
3396 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3397 * Therefore, if this magic number is present, it carries no information
3398 * and must be discarded.
3400 int path_mount(const char *dev_name
, struct path
*path
,
3401 const char *type_page
, unsigned long flags
, void *data_page
)
3403 unsigned int mnt_flags
= 0, sb_flags
;
3407 if ((flags
& MS_MGC_MSK
) == MS_MGC_VAL
)
3408 flags
&= ~MS_MGC_MSK
;
3410 /* Basic sanity checks */
3412 ((char *)data_page
)[PAGE_SIZE
- 1] = 0;
3414 if (flags
& MS_NOUSER
)
3417 ret
= security_sb_mount(dev_name
, path
, type_page
, flags
, data_page
);
3422 if (flags
& SB_MANDLOCK
)
3425 /* Default to relatime unless overriden */
3426 if (!(flags
& MS_NOATIME
))
3427 mnt_flags
|= MNT_RELATIME
;
3429 /* Separate the per-mountpoint flags */
3430 if (flags
& MS_NOSUID
)
3431 mnt_flags
|= MNT_NOSUID
;
3432 if (flags
& MS_NODEV
)
3433 mnt_flags
|= MNT_NODEV
;
3434 if (flags
& MS_NOEXEC
)
3435 mnt_flags
|= MNT_NOEXEC
;
3436 if (flags
& MS_NOATIME
)
3437 mnt_flags
|= MNT_NOATIME
;
3438 if (flags
& MS_NODIRATIME
)
3439 mnt_flags
|= MNT_NODIRATIME
;
3440 if (flags
& MS_STRICTATIME
)
3441 mnt_flags
&= ~(MNT_RELATIME
| MNT_NOATIME
);
3442 if (flags
& MS_RDONLY
)
3443 mnt_flags
|= MNT_READONLY
;
3444 if (flags
& MS_NOSYMFOLLOW
)
3445 mnt_flags
|= MNT_NOSYMFOLLOW
;
3447 /* The default atime for remount is preservation */
3448 if ((flags
& MS_REMOUNT
) &&
3449 ((flags
& (MS_NOATIME
| MS_NODIRATIME
| MS_RELATIME
|
3450 MS_STRICTATIME
)) == 0)) {
3451 mnt_flags
&= ~MNT_ATIME_MASK
;
3452 mnt_flags
|= path
->mnt
->mnt_flags
& MNT_ATIME_MASK
;
3455 sb_flags
= flags
& (SB_RDONLY
|
3464 if ((flags
& (MS_REMOUNT
| MS_BIND
)) == (MS_REMOUNT
| MS_BIND
))
3465 return do_reconfigure_mnt(path
, mnt_flags
);
3466 if (flags
& MS_REMOUNT
)
3467 return do_remount(path
, flags
, sb_flags
, mnt_flags
, data_page
);
3468 if (flags
& MS_BIND
)
3469 return do_loopback(path
, dev_name
, flags
& MS_REC
);
3470 if (flags
& (MS_SHARED
| MS_PRIVATE
| MS_SLAVE
| MS_UNBINDABLE
))
3471 return do_change_type(path
, flags
);
3472 if (flags
& MS_MOVE
)
3473 return do_move_mount_old(path
, dev_name
);
3475 return do_new_mount(path
, type_page
, sb_flags
, mnt_flags
, dev_name
,
3479 long do_mount(const char *dev_name
, const char __user
*dir_name
,
3480 const char *type_page
, unsigned long flags
, void *data_page
)
3485 ret
= user_path_at(AT_FDCWD
, dir_name
, LOOKUP_FOLLOW
, &path
);
3488 ret
= path_mount(dev_name
, &path
, type_page
, flags
, data_page
);
3493 static struct ucounts
*inc_mnt_namespaces(struct user_namespace
*ns
)
3495 return inc_ucount(ns
, current_euid(), UCOUNT_MNT_NAMESPACES
);
3498 static void dec_mnt_namespaces(struct ucounts
*ucounts
)
3500 dec_ucount(ucounts
, UCOUNT_MNT_NAMESPACES
);
3503 static void free_mnt_ns(struct mnt_namespace
*ns
)
3505 if (!is_anon_ns(ns
))
3506 ns_free_inum(&ns
->ns
);
3507 dec_mnt_namespaces(ns
->ucounts
);
3508 put_user_ns(ns
->user_ns
);
3513 * Assign a sequence number so we can detect when we attempt to bind
3514 * mount a reference to an older mount namespace into the current
3515 * mount namespace, preventing reference counting loops. A 64bit
3516 * number incrementing at 10Ghz will take 12,427 years to wrap which
3517 * is effectively never, so we can ignore the possibility.
3519 static atomic64_t mnt_ns_seq
= ATOMIC64_INIT(1);
3521 static struct mnt_namespace
*alloc_mnt_ns(struct user_namespace
*user_ns
, bool anon
)
3523 struct mnt_namespace
*new_ns
;
3524 struct ucounts
*ucounts
;
3527 ucounts
= inc_mnt_namespaces(user_ns
);
3529 return ERR_PTR(-ENOSPC
);
3531 new_ns
= kzalloc(sizeof(struct mnt_namespace
), GFP_KERNEL_ACCOUNT
);
3533 dec_mnt_namespaces(ucounts
);
3534 return ERR_PTR(-ENOMEM
);
3537 ret
= ns_alloc_inum(&new_ns
->ns
);
3540 dec_mnt_namespaces(ucounts
);
3541 return ERR_PTR(ret
);
3544 new_ns
->ns
.ops
= &mntns_operations
;
3546 new_ns
->seq
= atomic64_add_return(1, &mnt_ns_seq
);
3547 refcount_set(&new_ns
->ns
.count
, 1);
3548 INIT_LIST_HEAD(&new_ns
->list
);
3549 init_waitqueue_head(&new_ns
->poll
);
3550 spin_lock_init(&new_ns
->ns_lock
);
3551 new_ns
->user_ns
= get_user_ns(user_ns
);
3552 new_ns
->ucounts
= ucounts
;
3557 struct mnt_namespace
*copy_mnt_ns(unsigned long flags
, struct mnt_namespace
*ns
,
3558 struct user_namespace
*user_ns
, struct fs_struct
*new_fs
)
3560 struct mnt_namespace
*new_ns
;
3561 struct vfsmount
*rootmnt
= NULL
, *pwdmnt
= NULL
;
3562 struct mount
*p
, *q
;
3569 if (likely(!(flags
& CLONE_NEWNS
))) {
3576 new_ns
= alloc_mnt_ns(user_ns
, false);
3581 /* First pass: copy the tree topology */
3582 copy_flags
= CL_COPY_UNBINDABLE
| CL_EXPIRE
;
3583 if (user_ns
!= ns
->user_ns
)
3584 copy_flags
|= CL_SHARED_TO_SLAVE
;
3585 new = copy_tree(old
, old
->mnt
.mnt_root
, copy_flags
);
3588 free_mnt_ns(new_ns
);
3589 return ERR_CAST(new);
3591 if (user_ns
!= ns
->user_ns
) {
3594 unlock_mount_hash();
3597 list_add_tail(&new_ns
->list
, &new->mnt_list
);
3600 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3601 * as belonging to new namespace. We have already acquired a private
3602 * fs_struct, so tsk->fs->lock is not needed.
3610 if (&p
->mnt
== new_fs
->root
.mnt
) {
3611 new_fs
->root
.mnt
= mntget(&q
->mnt
);
3614 if (&p
->mnt
== new_fs
->pwd
.mnt
) {
3615 new_fs
->pwd
.mnt
= mntget(&q
->mnt
);
3619 p
= next_mnt(p
, old
);
3620 q
= next_mnt(q
, new);
3623 // an mntns binding we'd skipped?
3624 while (p
->mnt
.mnt_root
!= q
->mnt
.mnt_root
)
3625 p
= next_mnt(skip_mnt_tree(p
), old
);
3637 struct dentry
*mount_subtree(struct vfsmount
*m
, const char *name
)
3639 struct mount
*mnt
= real_mount(m
);
3640 struct mnt_namespace
*ns
;
3641 struct super_block
*s
;
3645 ns
= alloc_mnt_ns(&init_user_ns
, true);
3648 return ERR_CAST(ns
);
3653 list_add(&mnt
->mnt_list
, &ns
->list
);
3655 err
= vfs_path_lookup(m
->mnt_root
, m
,
3656 name
, LOOKUP_FOLLOW
|LOOKUP_AUTOMOUNT
, &path
);
3661 return ERR_PTR(err
);
3663 /* trade a vfsmount reference for active sb one */
3664 s
= path
.mnt
->mnt_sb
;
3665 atomic_inc(&s
->s_active
);
3667 /* lock the sucker */
3668 down_write(&s
->s_umount
);
3669 /* ... and return the root of (sub)tree on it */
3672 EXPORT_SYMBOL(mount_subtree
);
3674 SYSCALL_DEFINE5(mount
, char __user
*, dev_name
, char __user
*, dir_name
,
3675 char __user
*, type
, unsigned long, flags
, void __user
*, data
)
3682 kernel_type
= copy_mount_string(type
);
3683 ret
= PTR_ERR(kernel_type
);
3684 if (IS_ERR(kernel_type
))
3687 kernel_dev
= copy_mount_string(dev_name
);
3688 ret
= PTR_ERR(kernel_dev
);
3689 if (IS_ERR(kernel_dev
))
3692 options
= copy_mount_options(data
);
3693 ret
= PTR_ERR(options
);
3694 if (IS_ERR(options
))
3697 ret
= do_mount(kernel_dev
, dir_name
, kernel_type
, flags
, options
);
3708 #define FSMOUNT_VALID_FLAGS \
3709 (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
3710 MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \
3711 MOUNT_ATTR_NOSYMFOLLOW)
3713 #define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
3715 #define MOUNT_SETATTR_PROPAGATION_FLAGS \
3716 (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
3718 static unsigned int attr_flags_to_mnt_flags(u64 attr_flags
)
3720 unsigned int mnt_flags
= 0;
3722 if (attr_flags
& MOUNT_ATTR_RDONLY
)
3723 mnt_flags
|= MNT_READONLY
;
3724 if (attr_flags
& MOUNT_ATTR_NOSUID
)
3725 mnt_flags
|= MNT_NOSUID
;
3726 if (attr_flags
& MOUNT_ATTR_NODEV
)
3727 mnt_flags
|= MNT_NODEV
;
3728 if (attr_flags
& MOUNT_ATTR_NOEXEC
)
3729 mnt_flags
|= MNT_NOEXEC
;
3730 if (attr_flags
& MOUNT_ATTR_NODIRATIME
)
3731 mnt_flags
|= MNT_NODIRATIME
;
3732 if (attr_flags
& MOUNT_ATTR_NOSYMFOLLOW
)
3733 mnt_flags
|= MNT_NOSYMFOLLOW
;
3739 * Create a kernel mount representation for a new, prepared superblock
3740 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3742 SYSCALL_DEFINE3(fsmount
, int, fs_fd
, unsigned int, flags
,
3743 unsigned int, attr_flags
)
3745 struct mnt_namespace
*ns
;
3746 struct fs_context
*fc
;
3748 struct path newmount
;
3751 unsigned int mnt_flags
= 0;
3757 if ((flags
& ~(FSMOUNT_CLOEXEC
)) != 0)
3760 if (attr_flags
& ~FSMOUNT_VALID_FLAGS
)
3763 mnt_flags
= attr_flags_to_mnt_flags(attr_flags
);
3765 switch (attr_flags
& MOUNT_ATTR__ATIME
) {
3766 case MOUNT_ATTR_STRICTATIME
:
3768 case MOUNT_ATTR_NOATIME
:
3769 mnt_flags
|= MNT_NOATIME
;
3771 case MOUNT_ATTR_RELATIME
:
3772 mnt_flags
|= MNT_RELATIME
;
3783 if (f
.file
->f_op
!= &fscontext_fops
)
3786 fc
= f
.file
->private_data
;
3788 ret
= mutex_lock_interruptible(&fc
->uapi_mutex
);
3792 /* There must be a valid superblock or we can't mount it */
3798 if (mount_too_revealing(fc
->root
->d_sb
, &mnt_flags
)) {
3799 pr_warn("VFS: Mount too revealing\n");
3804 if (fc
->phase
!= FS_CONTEXT_AWAITING_MOUNT
)
3807 if (fc
->sb_flags
& SB_MANDLOCK
)
3810 newmount
.mnt
= vfs_create_mount(fc
);
3811 if (IS_ERR(newmount
.mnt
)) {
3812 ret
= PTR_ERR(newmount
.mnt
);
3815 newmount
.dentry
= dget(fc
->root
);
3816 newmount
.mnt
->mnt_flags
= mnt_flags
;
3818 /* We've done the mount bit - now move the file context into more or
3819 * less the same state as if we'd done an fspick(). We don't want to
3820 * do any memory allocation or anything like that at this point as we
3821 * don't want to have to handle any errors incurred.
3823 vfs_clean_context(fc
);
3825 ns
= alloc_mnt_ns(current
->nsproxy
->mnt_ns
->user_ns
, true);
3830 mnt
= real_mount(newmount
.mnt
);
3834 list_add(&mnt
->mnt_list
, &ns
->list
);
3835 mntget(newmount
.mnt
);
3837 /* Attach to an apparent O_PATH fd with a note that we need to unmount
3838 * it, not just simply put it.
3840 file
= dentry_open(&newmount
, O_PATH
, fc
->cred
);
3842 dissolve_on_fput(newmount
.mnt
);
3843 ret
= PTR_ERR(file
);
3846 file
->f_mode
|= FMODE_NEED_UNMOUNT
;
3848 ret
= get_unused_fd_flags((flags
& FSMOUNT_CLOEXEC
) ? O_CLOEXEC
: 0);
3850 fd_install(ret
, file
);
3855 path_put(&newmount
);
3857 mutex_unlock(&fc
->uapi_mutex
);
3864 * Move a mount from one place to another. In combination with
3865 * fsopen()/fsmount() this is used to install a new mount and in combination
3866 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
3869 * Note the flags value is a combination of MOVE_MOUNT_* flags.
3871 SYSCALL_DEFINE5(move_mount
,
3872 int, from_dfd
, const char __user
*, from_pathname
,
3873 int, to_dfd
, const char __user
*, to_pathname
,
3874 unsigned int, flags
)
3876 struct path from_path
, to_path
;
3877 unsigned int lflags
;
3883 if (flags
& ~MOVE_MOUNT__MASK
)
3886 /* If someone gives a pathname, they aren't permitted to move
3887 * from an fd that requires unmount as we can't get at the flag
3888 * to clear it afterwards.
3891 if (flags
& MOVE_MOUNT_F_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
3892 if (flags
& MOVE_MOUNT_F_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
3893 if (flags
& MOVE_MOUNT_F_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
3895 ret
= user_path_at(from_dfd
, from_pathname
, lflags
, &from_path
);
3900 if (flags
& MOVE_MOUNT_T_SYMLINKS
) lflags
|= LOOKUP_FOLLOW
;
3901 if (flags
& MOVE_MOUNT_T_AUTOMOUNTS
) lflags
|= LOOKUP_AUTOMOUNT
;
3902 if (flags
& MOVE_MOUNT_T_EMPTY_PATH
) lflags
|= LOOKUP_EMPTY
;
3904 ret
= user_path_at(to_dfd
, to_pathname
, lflags
, &to_path
);
3908 ret
= security_move_mount(&from_path
, &to_path
);
3912 if (flags
& MOVE_MOUNT_SET_GROUP
)
3913 ret
= do_set_group(&from_path
, &to_path
);
3915 ret
= do_move_mount(&from_path
, &to_path
);
3920 path_put(&from_path
);
3925 * Return true if path is reachable from root
3927 * namespace_sem or mount_lock is held
3929 bool is_path_reachable(struct mount
*mnt
, struct dentry
*dentry
,
3930 const struct path
*root
)
3932 while (&mnt
->mnt
!= root
->mnt
&& mnt_has_parent(mnt
)) {
3933 dentry
= mnt
->mnt_mountpoint
;
3934 mnt
= mnt
->mnt_parent
;
3936 return &mnt
->mnt
== root
->mnt
&& is_subdir(dentry
, root
->dentry
);
3939 bool path_is_under(const struct path
*path1
, const struct path
*path2
)
3942 read_seqlock_excl(&mount_lock
);
3943 res
= is_path_reachable(real_mount(path1
->mnt
), path1
->dentry
, path2
);
3944 read_sequnlock_excl(&mount_lock
);
3947 EXPORT_SYMBOL(path_is_under
);
3950 * pivot_root Semantics:
3951 * Moves the root file system of the current process to the directory put_old,
3952 * makes new_root as the new root file system of the current process, and sets
3953 * root/cwd of all processes which had them on the current root to new_root.
3956 * The new_root and put_old must be directories, and must not be on the
3957 * same file system as the current process root. The put_old must be
3958 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3959 * pointed to by put_old must yield the same directory as new_root. No other
3960 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3962 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3963 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
3964 * in this situation.
3967 * - we don't move root/cwd if they are not at the root (reason: if something
3968 * cared enough to change them, it's probably wrong to force them elsewhere)
3969 * - it's okay to pick a root that isn't the root of a file system, e.g.
3970 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3971 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3974 SYSCALL_DEFINE2(pivot_root
, const char __user
*, new_root
,
3975 const char __user
*, put_old
)
3977 struct path
new, old
, root
;
3978 struct mount
*new_mnt
, *root_mnt
, *old_mnt
, *root_parent
, *ex_parent
;
3979 struct mountpoint
*old_mp
, *root_mp
;
3985 error
= user_path_at(AT_FDCWD
, new_root
,
3986 LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
, &new);
3990 error
= user_path_at(AT_FDCWD
, put_old
,
3991 LOOKUP_FOLLOW
| LOOKUP_DIRECTORY
, &old
);
3995 error
= security_sb_pivotroot(&old
, &new);
3999 get_fs_root(current
->fs
, &root
);
4000 old_mp
= lock_mount(&old
);
4001 error
= PTR_ERR(old_mp
);
4006 new_mnt
= real_mount(new.mnt
);
4007 root_mnt
= real_mount(root
.mnt
);
4008 old_mnt
= real_mount(old
.mnt
);
4009 ex_parent
= new_mnt
->mnt_parent
;
4010 root_parent
= root_mnt
->mnt_parent
;
4011 if (IS_MNT_SHARED(old_mnt
) ||
4012 IS_MNT_SHARED(ex_parent
) ||
4013 IS_MNT_SHARED(root_parent
))
4015 if (!check_mnt(root_mnt
) || !check_mnt(new_mnt
))
4017 if (new_mnt
->mnt
.mnt_flags
& MNT_LOCKED
)
4020 if (d_unlinked(new.dentry
))
4023 if (new_mnt
== root_mnt
|| old_mnt
== root_mnt
)
4024 goto out4
; /* loop, on the same file system */
4026 if (root
.mnt
->mnt_root
!= root
.dentry
)
4027 goto out4
; /* not a mountpoint */
4028 if (!mnt_has_parent(root_mnt
))
4029 goto out4
; /* not attached */
4030 if (new.mnt
->mnt_root
!= new.dentry
)
4031 goto out4
; /* not a mountpoint */
4032 if (!mnt_has_parent(new_mnt
))
4033 goto out4
; /* not attached */
4034 /* make sure we can reach put_old from new_root */
4035 if (!is_path_reachable(old_mnt
, old
.dentry
, &new))
4037 /* make certain new is below the root */
4038 if (!is_path_reachable(new_mnt
, new.dentry
, &root
))
4041 umount_mnt(new_mnt
);
4042 root_mp
= unhash_mnt(root_mnt
); /* we'll need its mountpoint */
4043 if (root_mnt
->mnt
.mnt_flags
& MNT_LOCKED
) {
4044 new_mnt
->mnt
.mnt_flags
|= MNT_LOCKED
;
4045 root_mnt
->mnt
.mnt_flags
&= ~MNT_LOCKED
;
4047 /* mount old root on put_old */
4048 attach_mnt(root_mnt
, old_mnt
, old_mp
);
4049 /* mount new_root on / */
4050 attach_mnt(new_mnt
, root_parent
, root_mp
);
4051 mnt_add_count(root_parent
, -1);
4052 touch_mnt_namespace(current
->nsproxy
->mnt_ns
);
4053 /* A moved mount should not expire automatically */
4054 list_del_init(&new_mnt
->mnt_expire
);
4055 put_mountpoint(root_mp
);
4056 unlock_mount_hash();
4057 chroot_fs_refs(&root
, &new);
4060 unlock_mount(old_mp
);
4062 mntput_no_expire(ex_parent
);
4073 static unsigned int recalc_flags(struct mount_kattr
*kattr
, struct mount
*mnt
)
4075 unsigned int flags
= mnt
->mnt
.mnt_flags
;
4077 /* flags to clear */
4078 flags
&= ~kattr
->attr_clr
;
4079 /* flags to raise */
4080 flags
|= kattr
->attr_set
;
4085 static int can_idmap_mount(const struct mount_kattr
*kattr
, struct mount
*mnt
)
4087 struct vfsmount
*m
= &mnt
->mnt
;
4088 struct user_namespace
*fs_userns
= m
->mnt_sb
->s_user_ns
;
4090 if (!kattr
->mnt_idmap
)
4094 * Creating an idmapped mount with the filesystem wide idmapping
4095 * doesn't make sense so block that. We don't allow mushy semantics.
4097 if (mnt_idmap_owner(kattr
->mnt_idmap
) == fs_userns
)
4101 * Once a mount has been idmapped we don't allow it to change its
4102 * mapping. It makes things simpler and callers can just create
4103 * another bind-mount they can idmap if they want to.
4105 if (is_idmapped_mnt(m
))
4108 /* The underlying filesystem doesn't support idmapped mounts yet. */
4109 if (!(m
->mnt_sb
->s_type
->fs_flags
& FS_ALLOW_IDMAP
))
4112 /* We're not controlling the superblock. */
4113 if (!ns_capable(fs_userns
, CAP_SYS_ADMIN
))
4116 /* Mount has already been visible in the filesystem hierarchy. */
4117 if (!is_anon_ns(mnt
->mnt_ns
))
4124 * mnt_allow_writers() - check whether the attribute change allows writers
4125 * @kattr: the new mount attributes
4126 * @mnt: the mount to which @kattr will be applied
4128 * Check whether thew new mount attributes in @kattr allow concurrent writers.
4130 * Return: true if writers need to be held, false if not
4132 static inline bool mnt_allow_writers(const struct mount_kattr
*kattr
,
4133 const struct mount
*mnt
)
4135 return (!(kattr
->attr_set
& MNT_READONLY
) ||
4136 (mnt
->mnt
.mnt_flags
& MNT_READONLY
)) &&
4140 static int mount_setattr_prepare(struct mount_kattr
*kattr
, struct mount
*mnt
)
4145 for (m
= mnt
; m
; m
= next_mnt(m
, mnt
)) {
4146 if (!can_change_locked_flags(m
, recalc_flags(kattr
, m
))) {
4151 err
= can_idmap_mount(kattr
, m
);
4155 if (!mnt_allow_writers(kattr
, m
)) {
4156 err
= mnt_hold_writers(m
);
4161 if (!kattr
->recurse
)
4169 * If we had to call mnt_hold_writers() MNT_WRITE_HOLD will
4170 * be set in @mnt_flags. The loop unsets MNT_WRITE_HOLD for all
4171 * mounts and needs to take care to include the first mount.
4173 for (p
= mnt
; p
; p
= next_mnt(p
, mnt
)) {
4174 /* If we had to hold writers unblock them. */
4175 if (p
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
4176 mnt_unhold_writers(p
);
4179 * We're done once the first mount we changed got
4180 * MNT_WRITE_HOLD unset.
4189 static void do_idmap_mount(const struct mount_kattr
*kattr
, struct mount
*mnt
)
4191 if (!kattr
->mnt_idmap
)
4195 * Pairs with smp_load_acquire() in mnt_idmap().
4197 * Since we only allow a mount to change the idmapping once and
4198 * verified this in can_idmap_mount() we know that the mount has
4199 * @nop_mnt_idmap attached to it. So there's no need to drop any
4202 smp_store_release(&mnt
->mnt
.mnt_idmap
, mnt_idmap_get(kattr
->mnt_idmap
));
4205 static void mount_setattr_commit(struct mount_kattr
*kattr
, struct mount
*mnt
)
4209 for (m
= mnt
; m
; m
= next_mnt(m
, mnt
)) {
4212 do_idmap_mount(kattr
, m
);
4213 flags
= recalc_flags(kattr
, m
);
4214 WRITE_ONCE(m
->mnt
.mnt_flags
, flags
);
4216 /* If we had to hold writers unblock them. */
4217 if (m
->mnt
.mnt_flags
& MNT_WRITE_HOLD
)
4218 mnt_unhold_writers(m
);
4220 if (kattr
->propagation
)
4221 change_mnt_propagation(m
, kattr
->propagation
);
4222 if (!kattr
->recurse
)
4225 touch_mnt_namespace(mnt
->mnt_ns
);
4228 static int do_mount_setattr(struct path
*path
, struct mount_kattr
*kattr
)
4230 struct mount
*mnt
= real_mount(path
->mnt
);
4233 if (path
->dentry
!= mnt
->mnt
.mnt_root
)
4236 if (kattr
->mnt_userns
) {
4237 struct mnt_idmap
*mnt_idmap
;
4239 mnt_idmap
= alloc_mnt_idmap(kattr
->mnt_userns
);
4240 if (IS_ERR(mnt_idmap
))
4241 return PTR_ERR(mnt_idmap
);
4242 kattr
->mnt_idmap
= mnt_idmap
;
4245 if (kattr
->propagation
) {
4247 * Only take namespace_lock() if we're actually changing
4251 if (kattr
->propagation
== MS_SHARED
) {
4252 err
= invent_group_ids(mnt
, kattr
->recurse
);
4263 /* Ensure that this isn't anything purely vfs internal. */
4264 if (!is_mounted(&mnt
->mnt
))
4268 * If this is an attached mount make sure it's located in the callers
4269 * mount namespace. If it's not don't let the caller interact with it.
4270 * If this is a detached mount make sure it has an anonymous mount
4271 * namespace attached to it, i.e. we've created it via OPEN_TREE_CLONE.
4273 if (!(mnt_has_parent(mnt
) ? check_mnt(mnt
) : is_anon_ns(mnt
->mnt_ns
)))
4277 * First, we get the mount tree in a shape where we can change mount
4278 * properties without failure. If we succeeded to do so we commit all
4279 * changes and if we failed we clean up.
4281 err
= mount_setattr_prepare(kattr
, mnt
);
4283 mount_setattr_commit(kattr
, mnt
);
4286 unlock_mount_hash();
4288 if (kattr
->propagation
) {
4291 cleanup_group_ids(mnt
, NULL
);
4297 static int build_mount_idmapped(const struct mount_attr
*attr
, size_t usize
,
4298 struct mount_kattr
*kattr
, unsigned int flags
)
4301 struct ns_common
*ns
;
4302 struct user_namespace
*mnt_userns
;
4305 if (!((attr
->attr_set
| attr
->attr_clr
) & MOUNT_ATTR_IDMAP
))
4309 * We currently do not support clearing an idmapped mount. If this ever
4310 * is a use-case we can revisit this but for now let's keep it simple
4313 if (attr
->attr_clr
& MOUNT_ATTR_IDMAP
)
4316 if (attr
->userns_fd
> INT_MAX
)
4319 file
= fget(attr
->userns_fd
);
4323 if (!proc_ns_file(file
)) {
4328 ns
= get_proc_ns(file_inode(file
));
4329 if (ns
->ops
->type
!= CLONE_NEWUSER
) {
4335 * The initial idmapping cannot be used to create an idmapped
4336 * mount. We use the initial idmapping as an indicator of a mount
4337 * that is not idmapped. It can simply be passed into helpers that
4338 * are aware of idmapped mounts as a convenient shortcut. A user
4339 * can just create a dedicated identity mapping to achieve the same
4342 mnt_userns
= container_of(ns
, struct user_namespace
, ns
);
4343 if (initial_idmapping(mnt_userns
)) {
4348 /* We're not controlling the target namespace. */
4349 if (!ns_capable(mnt_userns
, CAP_SYS_ADMIN
)) {
4354 kattr
->mnt_userns
= get_user_ns(mnt_userns
);
4361 static int build_mount_kattr(const struct mount_attr
*attr
, size_t usize
,
4362 struct mount_kattr
*kattr
, unsigned int flags
)
4364 unsigned int lookup_flags
= LOOKUP_AUTOMOUNT
| LOOKUP_FOLLOW
;
4366 if (flags
& AT_NO_AUTOMOUNT
)
4367 lookup_flags
&= ~LOOKUP_AUTOMOUNT
;
4368 if (flags
& AT_SYMLINK_NOFOLLOW
)
4369 lookup_flags
&= ~LOOKUP_FOLLOW
;
4370 if (flags
& AT_EMPTY_PATH
)
4371 lookup_flags
|= LOOKUP_EMPTY
;
4373 *kattr
= (struct mount_kattr
) {
4374 .lookup_flags
= lookup_flags
,
4375 .recurse
= !!(flags
& AT_RECURSIVE
),
4378 if (attr
->propagation
& ~MOUNT_SETATTR_PROPAGATION_FLAGS
)
4380 if (hweight32(attr
->propagation
& MOUNT_SETATTR_PROPAGATION_FLAGS
) > 1)
4382 kattr
->propagation
= attr
->propagation
;
4384 if ((attr
->attr_set
| attr
->attr_clr
) & ~MOUNT_SETATTR_VALID_FLAGS
)
4387 kattr
->attr_set
= attr_flags_to_mnt_flags(attr
->attr_set
);
4388 kattr
->attr_clr
= attr_flags_to_mnt_flags(attr
->attr_clr
);
4391 * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
4392 * users wanting to transition to a different atime setting cannot
4393 * simply specify the atime setting in @attr_set, but must also
4394 * specify MOUNT_ATTR__ATIME in the @attr_clr field.
4395 * So ensure that MOUNT_ATTR__ATIME can't be partially set in
4396 * @attr_clr and that @attr_set can't have any atime bits set if
4397 * MOUNT_ATTR__ATIME isn't set in @attr_clr.
4399 if (attr
->attr_clr
& MOUNT_ATTR__ATIME
) {
4400 if ((attr
->attr_clr
& MOUNT_ATTR__ATIME
) != MOUNT_ATTR__ATIME
)
4404 * Clear all previous time settings as they are mutually
4407 kattr
->attr_clr
|= MNT_RELATIME
| MNT_NOATIME
;
4408 switch (attr
->attr_set
& MOUNT_ATTR__ATIME
) {
4409 case MOUNT_ATTR_RELATIME
:
4410 kattr
->attr_set
|= MNT_RELATIME
;
4412 case MOUNT_ATTR_NOATIME
:
4413 kattr
->attr_set
|= MNT_NOATIME
;
4415 case MOUNT_ATTR_STRICTATIME
:
4421 if (attr
->attr_set
& MOUNT_ATTR__ATIME
)
4425 return build_mount_idmapped(attr
, usize
, kattr
, flags
);
4428 static void finish_mount_kattr(struct mount_kattr
*kattr
)
4430 put_user_ns(kattr
->mnt_userns
);
4431 kattr
->mnt_userns
= NULL
;
4433 if (kattr
->mnt_idmap
)
4434 mnt_idmap_put(kattr
->mnt_idmap
);
4437 SYSCALL_DEFINE5(mount_setattr
, int, dfd
, const char __user
*, path
,
4438 unsigned int, flags
, struct mount_attr __user
*, uattr
,
4443 struct mount_attr attr
;
4444 struct mount_kattr kattr
;
4446 BUILD_BUG_ON(sizeof(struct mount_attr
) != MOUNT_ATTR_SIZE_VER0
);
4448 if (flags
& ~(AT_EMPTY_PATH
|
4450 AT_SYMLINK_NOFOLLOW
|
4454 if (unlikely(usize
> PAGE_SIZE
))
4456 if (unlikely(usize
< MOUNT_ATTR_SIZE_VER0
))
4462 err
= copy_struct_from_user(&attr
, sizeof(attr
), uattr
, usize
);
4466 /* Don't bother walking through the mounts if this is a nop. */
4467 if (attr
.attr_set
== 0 &&
4468 attr
.attr_clr
== 0 &&
4469 attr
.propagation
== 0)
4472 err
= build_mount_kattr(&attr
, usize
, &kattr
, flags
);
4476 err
= user_path_at(dfd
, path
, kattr
.lookup_flags
, &target
);
4478 err
= do_mount_setattr(&target
, &kattr
);
4481 finish_mount_kattr(&kattr
);
4485 static void __init
init_mount_tree(void)
4487 struct vfsmount
*mnt
;
4489 struct mnt_namespace
*ns
;
4492 mnt
= vfs_kern_mount(&rootfs_fs_type
, 0, "rootfs", NULL
);
4494 panic("Can't create rootfs");
4496 ns
= alloc_mnt_ns(&init_user_ns
, false);
4498 panic("Can't allocate initial namespace");
4499 m
= real_mount(mnt
);
4503 list_add(&m
->mnt_list
, &ns
->list
);
4504 init_task
.nsproxy
->mnt_ns
= ns
;
4508 root
.dentry
= mnt
->mnt_root
;
4509 mnt
->mnt_flags
|= MNT_LOCKED
;
4511 set_fs_pwd(current
->fs
, &root
);
4512 set_fs_root(current
->fs
, &root
);
4515 void __init
mnt_init(void)
4519 mnt_cache
= kmem_cache_create("mnt_cache", sizeof(struct mount
),
4520 0, SLAB_HWCACHE_ALIGN
|SLAB_PANIC
|SLAB_ACCOUNT
, NULL
);
4522 mount_hashtable
= alloc_large_system_hash("Mount-cache",
4523 sizeof(struct hlist_head
),
4526 &m_hash_shift
, &m_hash_mask
, 0, 0);
4527 mountpoint_hashtable
= alloc_large_system_hash("Mountpoint-cache",
4528 sizeof(struct hlist_head
),
4531 &mp_hash_shift
, &mp_hash_mask
, 0, 0);
4533 if (!mount_hashtable
|| !mountpoint_hashtable
)
4534 panic("Failed to allocate mount hash table\n");
4540 printk(KERN_WARNING
"%s: sysfs_init error: %d\n",
4542 fs_kobj
= kobject_create_and_add("fs", NULL
);
4544 printk(KERN_WARNING
"%s: kobj create error\n", __func__
);
4550 void put_mnt_ns(struct mnt_namespace
*ns
)
4552 if (!refcount_dec_and_test(&ns
->ns
.count
))
4554 drop_collected_mounts(&ns
->root
->mnt
);
4558 struct vfsmount
*kern_mount(struct file_system_type
*type
)
4560 struct vfsmount
*mnt
;
4561 mnt
= vfs_kern_mount(type
, SB_KERNMOUNT
, type
->name
, NULL
);
4564 * it is a longterm mount, don't release mnt until
4565 * we unmount before file sys is unregistered
4567 real_mount(mnt
)->mnt_ns
= MNT_NS_INTERNAL
;
4571 EXPORT_SYMBOL_GPL(kern_mount
);
4573 void kern_unmount(struct vfsmount
*mnt
)
4575 /* release long term mount so mount point can be released */
4576 if (!IS_ERR_OR_NULL(mnt
)) {
4577 real_mount(mnt
)->mnt_ns
= NULL
;
4578 synchronize_rcu(); /* yecchhh... */
4582 EXPORT_SYMBOL(kern_unmount
);
4584 void kern_unmount_array(struct vfsmount
*mnt
[], unsigned int num
)
4588 for (i
= 0; i
< num
; i
++)
4590 real_mount(mnt
[i
])->mnt_ns
= NULL
;
4591 synchronize_rcu_expedited();
4592 for (i
= 0; i
< num
; i
++)
4595 EXPORT_SYMBOL(kern_unmount_array
);
4597 bool our_mnt(struct vfsmount
*mnt
)
4599 return check_mnt(real_mount(mnt
));
4602 bool current_chrooted(void)
4604 /* Does the current process have a non-standard root */
4605 struct path ns_root
;
4606 struct path fs_root
;
4609 /* Find the namespace root */
4610 ns_root
.mnt
= ¤t
->nsproxy
->mnt_ns
->root
->mnt
;
4611 ns_root
.dentry
= ns_root
.mnt
->mnt_root
;
4613 while (d_mountpoint(ns_root
.dentry
) && follow_down_one(&ns_root
))
4616 get_fs_root(current
->fs
, &fs_root
);
4618 chrooted
= !path_equal(&fs_root
, &ns_root
);
4626 static bool mnt_already_visible(struct mnt_namespace
*ns
,
4627 const struct super_block
*sb
,
4630 int new_flags
= *new_mnt_flags
;
4632 bool visible
= false;
4634 down_read(&namespace_sem
);
4636 list_for_each_entry(mnt
, &ns
->list
, mnt_list
) {
4637 struct mount
*child
;
4640 if (mnt_is_cursor(mnt
))
4643 if (mnt
->mnt
.mnt_sb
->s_type
!= sb
->s_type
)
4646 /* This mount is not fully visible if it's root directory
4647 * is not the root directory of the filesystem.
4649 if (mnt
->mnt
.mnt_root
!= mnt
->mnt
.mnt_sb
->s_root
)
4652 /* A local view of the mount flags */
4653 mnt_flags
= mnt
->mnt
.mnt_flags
;
4655 /* Don't miss readonly hidden in the superblock flags */
4656 if (sb_rdonly(mnt
->mnt
.mnt_sb
))
4657 mnt_flags
|= MNT_LOCK_READONLY
;
4659 /* Verify the mount flags are equal to or more permissive
4660 * than the proposed new mount.
4662 if ((mnt_flags
& MNT_LOCK_READONLY
) &&
4663 !(new_flags
& MNT_READONLY
))
4665 if ((mnt_flags
& MNT_LOCK_ATIME
) &&
4666 ((mnt_flags
& MNT_ATIME_MASK
) != (new_flags
& MNT_ATIME_MASK
)))
4669 /* This mount is not fully visible if there are any
4670 * locked child mounts that cover anything except for
4671 * empty directories.
4673 list_for_each_entry(child
, &mnt
->mnt_mounts
, mnt_child
) {
4674 struct inode
*inode
= child
->mnt_mountpoint
->d_inode
;
4675 /* Only worry about locked mounts */
4676 if (!(child
->mnt
.mnt_flags
& MNT_LOCKED
))
4678 /* Is the directory permanetly empty? */
4679 if (!is_empty_dir_inode(inode
))
4682 /* Preserve the locked attributes */
4683 *new_mnt_flags
|= mnt_flags
& (MNT_LOCK_READONLY
| \
4691 up_read(&namespace_sem
);
4695 static bool mount_too_revealing(const struct super_block
*sb
, int *new_mnt_flags
)
4697 const unsigned long required_iflags
= SB_I_NOEXEC
| SB_I_NODEV
;
4698 struct mnt_namespace
*ns
= current
->nsproxy
->mnt_ns
;
4699 unsigned long s_iflags
;
4701 if (ns
->user_ns
== &init_user_ns
)
4704 /* Can this filesystem be too revealing? */
4705 s_iflags
= sb
->s_iflags
;
4706 if (!(s_iflags
& SB_I_USERNS_VISIBLE
))
4709 if ((s_iflags
& required_iflags
) != required_iflags
) {
4710 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
4715 return !mnt_already_visible(ns
, sb
, new_mnt_flags
);
4718 bool mnt_may_suid(struct vfsmount
*mnt
)
4721 * Foreign mounts (accessed via fchdir or through /proc
4722 * symlinks) are always treated as if they are nosuid. This
4723 * prevents namespaces from trusting potentially unsafe
4724 * suid/sgid bits, file caps, or security labels that originate
4725 * in other namespaces.
4727 return !(mnt
->mnt_flags
& MNT_NOSUID
) && check_mnt(real_mount(mnt
)) &&
4728 current_in_userns(mnt
->mnt_sb
->s_user_ns
);
4731 static struct ns_common
*mntns_get(struct task_struct
*task
)
4733 struct ns_common
*ns
= NULL
;
4734 struct nsproxy
*nsproxy
;
4737 nsproxy
= task
->nsproxy
;
4739 ns
= &nsproxy
->mnt_ns
->ns
;
4740 get_mnt_ns(to_mnt_ns(ns
));
4747 static void mntns_put(struct ns_common
*ns
)
4749 put_mnt_ns(to_mnt_ns(ns
));
4752 static int mntns_install(struct nsset
*nsset
, struct ns_common
*ns
)
4754 struct nsproxy
*nsproxy
= nsset
->nsproxy
;
4755 struct fs_struct
*fs
= nsset
->fs
;
4756 struct mnt_namespace
*mnt_ns
= to_mnt_ns(ns
), *old_mnt_ns
;
4757 struct user_namespace
*user_ns
= nsset
->cred
->user_ns
;
4761 if (!ns_capable(mnt_ns
->user_ns
, CAP_SYS_ADMIN
) ||
4762 !ns_capable(user_ns
, CAP_SYS_CHROOT
) ||
4763 !ns_capable(user_ns
, CAP_SYS_ADMIN
))
4766 if (is_anon_ns(mnt_ns
))
4773 old_mnt_ns
= nsproxy
->mnt_ns
;
4774 nsproxy
->mnt_ns
= mnt_ns
;
4777 err
= vfs_path_lookup(mnt_ns
->root
->mnt
.mnt_root
, &mnt_ns
->root
->mnt
,
4778 "/", LOOKUP_DOWN
, &root
);
4780 /* revert to old namespace */
4781 nsproxy
->mnt_ns
= old_mnt_ns
;
4786 put_mnt_ns(old_mnt_ns
);
4788 /* Update the pwd and root */
4789 set_fs_pwd(fs
, &root
);
4790 set_fs_root(fs
, &root
);
4796 static struct user_namespace
*mntns_owner(struct ns_common
*ns
)
4798 return to_mnt_ns(ns
)->user_ns
;
4801 const struct proc_ns_operations mntns_operations
= {
4803 .type
= CLONE_NEWNS
,
4806 .install
= mntns_install
,
4807 .owner
= mntns_owner
,
4810 #ifdef CONFIG_SYSCTL
4811 static struct ctl_table fs_namespace_sysctls
[] = {
4813 .procname
= "mount-max",
4814 .data
= &sysctl_mount_max
,
4815 .maxlen
= sizeof(unsigned int),
4817 .proc_handler
= proc_dointvec_minmax
,
4818 .extra1
= SYSCTL_ONE
,
4823 static int __init
init_fs_namespace_sysctls(void)
4825 register_sysctl_init("fs", fs_namespace_sysctls
);
4828 fs_initcall(init_fs_namespace_sysctls
);
4830 #endif /* CONFIG_SYSCTL */