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 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 unsigned int attr_set;
80 unsigned int attr_clr;
81 unsigned int propagation;
82 unsigned int lookup_flags;
84 struct user_namespace *mnt_userns;
88 struct kobject *fs_kobj;
89 EXPORT_SYMBOL_GPL(fs_kobj);
92 * vfsmount lock may be taken for read to prevent changes to the
93 * vfsmount hash, ie. during mountpoint lookups or walking back
96 * It should be taken for write in all cases where the vfsmount
97 * tree or hash is modified or when a vfsmount structure is modified.
99 __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
101 static inline void lock_mount_hash(void)
103 write_seqlock(&mount_lock);
106 static inline void unlock_mount_hash(void)
108 write_sequnlock(&mount_lock);
111 static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
113 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
114 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
115 tmp = tmp + (tmp >> m_hash_shift);
116 return &mount_hashtable[tmp & m_hash_mask];
119 static inline struct hlist_head *mp_hash(struct dentry *dentry)
121 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
122 tmp = tmp + (tmp >> mp_hash_shift);
123 return &mountpoint_hashtable[tmp & mp_hash_mask];
126 static int mnt_alloc_id(struct mount *mnt)
128 int res = ida_alloc(&mnt_id_ida, GFP_KERNEL);
136 static void mnt_free_id(struct mount *mnt)
138 ida_free(&mnt_id_ida, mnt->mnt_id);
142 * Allocate a new peer group ID
144 static int mnt_alloc_group_id(struct mount *mnt)
146 int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL);
150 mnt->mnt_group_id = res;
155 * Release a peer group ID
157 void mnt_release_group_id(struct mount *mnt)
159 ida_free(&mnt_group_ida, mnt->mnt_group_id);
160 mnt->mnt_group_id = 0;
164 * vfsmount lock must be held for read
166 static inline void mnt_add_count(struct mount *mnt, int n)
169 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
178 * vfsmount lock must be held for write
180 int mnt_get_count(struct mount *mnt)
186 for_each_possible_cpu(cpu) {
187 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
192 return mnt->mnt_count;
196 static struct mount *alloc_vfsmnt(const char *name)
198 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
202 err = mnt_alloc_id(mnt);
207 mnt->mnt_devname = kstrdup_const(name,
209 if (!mnt->mnt_devname)
214 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
216 goto out_free_devname;
218 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
221 mnt->mnt_writers = 0;
224 INIT_HLIST_NODE(&mnt->mnt_hash);
225 INIT_LIST_HEAD(&mnt->mnt_child);
226 INIT_LIST_HEAD(&mnt->mnt_mounts);
227 INIT_LIST_HEAD(&mnt->mnt_list);
228 INIT_LIST_HEAD(&mnt->mnt_expire);
229 INIT_LIST_HEAD(&mnt->mnt_share);
230 INIT_LIST_HEAD(&mnt->mnt_slave_list);
231 INIT_LIST_HEAD(&mnt->mnt_slave);
232 INIT_HLIST_NODE(&mnt->mnt_mp_list);
233 INIT_LIST_HEAD(&mnt->mnt_umounting);
234 INIT_HLIST_HEAD(&mnt->mnt_stuck_children);
235 mnt->mnt.mnt_userns = &init_user_ns;
241 kfree_const(mnt->mnt_devname);
246 kmem_cache_free(mnt_cache, mnt);
251 * Most r/o checks on a fs are for operations that take
252 * discrete amounts of time, like a write() or unlink().
253 * We must keep track of when those operations start
254 * (for permission checks) and when they end, so that
255 * we can determine when writes are able to occur to
259 * __mnt_is_readonly: check whether a mount is read-only
260 * @mnt: the mount to check for its write status
262 * This shouldn't be used directly ouside of the VFS.
263 * It does not guarantee that the filesystem will stay
264 * r/w, just that it is right *now*. This can not and
265 * should not be used in place of IS_RDONLY(inode).
266 * mnt_want/drop_write() will _keep_ the filesystem
269 bool __mnt_is_readonly(struct vfsmount *mnt)
271 return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb);
273 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
275 static inline void mnt_inc_writers(struct mount *mnt)
278 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
284 static inline void mnt_dec_writers(struct mount *mnt)
287 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
293 static unsigned int mnt_get_writers(struct mount *mnt)
296 unsigned int count = 0;
299 for_each_possible_cpu(cpu) {
300 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
305 return mnt->mnt_writers;
309 static int mnt_is_readonly(struct vfsmount *mnt)
311 if (mnt->mnt_sb->s_readonly_remount)
313 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
315 return __mnt_is_readonly(mnt);
319 * Most r/o & frozen checks on a fs are for operations that take discrete
320 * amounts of time, like a write() or unlink(). We must keep track of when
321 * those operations start (for permission checks) and when they end, so that we
322 * can determine when writes are able to occur to a filesystem.
325 * __mnt_want_write - get write access to a mount without freeze protection
326 * @m: the mount on which to take a write
328 * This tells the low-level filesystem that a write is about to be performed to
329 * it, and makes sure that writes are allowed (mnt it read-write) before
330 * returning success. This operation does not protect against filesystem being
331 * frozen. When the write operation is finished, __mnt_drop_write() must be
332 * called. This is effectively a refcount.
334 int __mnt_want_write(struct vfsmount *m)
336 struct mount *mnt = real_mount(m);
340 mnt_inc_writers(mnt);
342 * The store to mnt_inc_writers must be visible before we pass
343 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
344 * incremented count after it has set MNT_WRITE_HOLD.
347 while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
350 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
351 * be set to match its requirements. So we must not load that until
352 * MNT_WRITE_HOLD is cleared.
355 if (mnt_is_readonly(m)) {
356 mnt_dec_writers(mnt);
365 * mnt_want_write - get write access to a mount
366 * @m: the mount on which to take a write
368 * This tells the low-level filesystem that a write is about to be performed to
369 * it, and makes sure that writes are allowed (mount is read-write, filesystem
370 * is not frozen) before returning success. When the write operation is
371 * finished, mnt_drop_write() must be called. This is effectively a refcount.
373 int mnt_want_write(struct vfsmount *m)
377 sb_start_write(m->mnt_sb);
378 ret = __mnt_want_write(m);
380 sb_end_write(m->mnt_sb);
383 EXPORT_SYMBOL_GPL(mnt_want_write);
386 * __mnt_want_write_file - get write access to a file's mount
387 * @file: the file who's mount on which to take a write
389 * This is like __mnt_want_write, but if the file is already open for writing it
390 * skips incrementing mnt_writers (since the open file already has a reference)
391 * and instead only does the check for emergency r/o remounts. This must be
392 * paired with __mnt_drop_write_file.
394 int __mnt_want_write_file(struct file *file)
396 if (file->f_mode & FMODE_WRITER) {
398 * Superblock may have become readonly while there are still
399 * writable fd's, e.g. due to a fs error with errors=remount-ro
401 if (__mnt_is_readonly(file->f_path.mnt))
405 return __mnt_want_write(file->f_path.mnt);
409 * mnt_want_write_file - get write access to a file's mount
410 * @file: the file who's mount on which to take a write
412 * This is like mnt_want_write, but if the file is already open for writing it
413 * skips incrementing mnt_writers (since the open file already has a reference)
414 * and instead only does the freeze protection and the check for emergency r/o
415 * remounts. This must be paired with mnt_drop_write_file.
417 int mnt_want_write_file(struct file *file)
421 sb_start_write(file_inode(file)->i_sb);
422 ret = __mnt_want_write_file(file);
424 sb_end_write(file_inode(file)->i_sb);
427 EXPORT_SYMBOL_GPL(mnt_want_write_file);
430 * __mnt_drop_write - give up write access to a mount
431 * @mnt: the mount on which to give up write access
433 * Tells the low-level filesystem that we are done
434 * performing writes to it. Must be matched with
435 * __mnt_want_write() call above.
437 void __mnt_drop_write(struct vfsmount *mnt)
440 mnt_dec_writers(real_mount(mnt));
445 * mnt_drop_write - give up write access to a mount
446 * @mnt: the mount on which to give up write access
448 * Tells the low-level filesystem that we are done performing writes to it and
449 * also allows filesystem to be frozen again. Must be matched with
450 * mnt_want_write() call above.
452 void mnt_drop_write(struct vfsmount *mnt)
454 __mnt_drop_write(mnt);
455 sb_end_write(mnt->mnt_sb);
457 EXPORT_SYMBOL_GPL(mnt_drop_write);
459 void __mnt_drop_write_file(struct file *file)
461 if (!(file->f_mode & FMODE_WRITER))
462 __mnt_drop_write(file->f_path.mnt);
465 void mnt_drop_write_file(struct file *file)
467 __mnt_drop_write_file(file);
468 sb_end_write(file_inode(file)->i_sb);
470 EXPORT_SYMBOL(mnt_drop_write_file);
472 static inline int mnt_hold_writers(struct mount *mnt)
474 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
476 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
477 * should be visible before we do.
482 * With writers on hold, if this value is zero, then there are
483 * definitely no active writers (although held writers may subsequently
484 * increment the count, they'll have to wait, and decrement it after
485 * seeing MNT_READONLY).
487 * It is OK to have counter incremented on one CPU and decremented on
488 * another: the sum will add up correctly. The danger would be when we
489 * sum up each counter, if we read a counter before it is incremented,
490 * but then read another CPU's count which it has been subsequently
491 * decremented from -- we would see more decrements than we should.
492 * MNT_WRITE_HOLD protects against this scenario, because
493 * mnt_want_write first increments count, then smp_mb, then spins on
494 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
495 * we're counting up here.
497 if (mnt_get_writers(mnt) > 0)
503 static inline void mnt_unhold_writers(struct mount *mnt)
506 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
507 * that become unheld will see MNT_READONLY.
510 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
513 static int mnt_make_readonly(struct mount *mnt)
517 ret = mnt_hold_writers(mnt);
519 mnt->mnt.mnt_flags |= MNT_READONLY;
520 mnt_unhold_writers(mnt);
524 int sb_prepare_remount_readonly(struct super_block *sb)
529 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
530 if (atomic_long_read(&sb->s_remove_count))
534 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
535 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
536 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
538 if (mnt_get_writers(mnt) > 0) {
544 if (!err && atomic_long_read(&sb->s_remove_count))
548 sb->s_readonly_remount = 1;
551 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
552 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
553 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
560 static void free_vfsmnt(struct mount *mnt)
562 struct user_namespace *mnt_userns;
564 mnt_userns = mnt_user_ns(&mnt->mnt);
565 if (!initial_idmapping(mnt_userns))
566 put_user_ns(mnt_userns);
567 kfree_const(mnt->mnt_devname);
569 free_percpu(mnt->mnt_pcp);
571 kmem_cache_free(mnt_cache, mnt);
574 static void delayed_free_vfsmnt(struct rcu_head *head)
576 free_vfsmnt(container_of(head, struct mount, mnt_rcu));
579 /* call under rcu_read_lock */
580 int __legitimize_mnt(struct vfsmount *bastard, unsigned seq)
583 if (read_seqretry(&mount_lock, seq))
587 mnt = real_mount(bastard);
588 mnt_add_count(mnt, 1);
589 smp_mb(); // see mntput_no_expire()
590 if (likely(!read_seqretry(&mount_lock, seq)))
592 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
593 mnt_add_count(mnt, -1);
597 if (unlikely(bastard->mnt_flags & MNT_DOOMED)) {
598 mnt_add_count(mnt, -1);
603 /* caller will mntput() */
607 /* call under rcu_read_lock */
608 bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
610 int res = __legitimize_mnt(bastard, seq);
613 if (unlikely(res < 0)) {
622 * find the first mount at @dentry on vfsmount @mnt.
623 * call under rcu_read_lock()
625 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
627 struct hlist_head *head = m_hash(mnt, dentry);
630 hlist_for_each_entry_rcu(p, head, mnt_hash)
631 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
637 * lookup_mnt - Return the first child mount mounted at path
639 * "First" means first mounted chronologically. If you create the
642 * mount /dev/sda1 /mnt
643 * mount /dev/sda2 /mnt
644 * mount /dev/sda3 /mnt
646 * Then lookup_mnt() on the base /mnt dentry in the root mount will
647 * return successively the root dentry and vfsmount of /dev/sda1, then
648 * /dev/sda2, then /dev/sda3, then NULL.
650 * lookup_mnt takes a reference to the found vfsmount.
652 struct vfsmount *lookup_mnt(const struct path *path)
654 struct mount *child_mnt;
660 seq = read_seqbegin(&mount_lock);
661 child_mnt = __lookup_mnt(path->mnt, path->dentry);
662 m = child_mnt ? &child_mnt->mnt : NULL;
663 } while (!legitimize_mnt(m, seq));
668 static inline void lock_ns_list(struct mnt_namespace *ns)
670 spin_lock(&ns->ns_lock);
673 static inline void unlock_ns_list(struct mnt_namespace *ns)
675 spin_unlock(&ns->ns_lock);
678 static inline bool mnt_is_cursor(struct mount *mnt)
680 return mnt->mnt.mnt_flags & MNT_CURSOR;
684 * __is_local_mountpoint - Test to see if dentry is a mountpoint in the
685 * current mount namespace.
687 * The common case is dentries are not mountpoints at all and that
688 * test is handled inline. For the slow case when we are actually
689 * dealing with a mountpoint of some kind, walk through all of the
690 * mounts in the current mount namespace and test to see if the dentry
693 * The mount_hashtable is not usable in the context because we
694 * need to identify all mounts that may be in the current mount
695 * namespace not just a mount that happens to have some specified
698 bool __is_local_mountpoint(struct dentry *dentry)
700 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
702 bool is_covered = false;
704 down_read(&namespace_sem);
706 list_for_each_entry(mnt, &ns->list, mnt_list) {
707 if (mnt_is_cursor(mnt))
709 is_covered = (mnt->mnt_mountpoint == dentry);
714 up_read(&namespace_sem);
719 static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
721 struct hlist_head *chain = mp_hash(dentry);
722 struct mountpoint *mp;
724 hlist_for_each_entry(mp, chain, m_hash) {
725 if (mp->m_dentry == dentry) {
733 static struct mountpoint *get_mountpoint(struct dentry *dentry)
735 struct mountpoint *mp, *new = NULL;
738 if (d_mountpoint(dentry)) {
739 /* might be worth a WARN_ON() */
740 if (d_unlinked(dentry))
741 return ERR_PTR(-ENOENT);
743 read_seqlock_excl(&mount_lock);
744 mp = lookup_mountpoint(dentry);
745 read_sequnlock_excl(&mount_lock);
751 new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
753 return ERR_PTR(-ENOMEM);
756 /* Exactly one processes may set d_mounted */
757 ret = d_set_mounted(dentry);
759 /* Someone else set d_mounted? */
763 /* The dentry is not available as a mountpoint? */
768 /* Add the new mountpoint to the hash table */
769 read_seqlock_excl(&mount_lock);
770 new->m_dentry = dget(dentry);
772 hlist_add_head(&new->m_hash, mp_hash(dentry));
773 INIT_HLIST_HEAD(&new->m_list);
774 read_sequnlock_excl(&mount_lock);
784 * vfsmount lock must be held. Additionally, the caller is responsible
785 * for serializing calls for given disposal list.
787 static void __put_mountpoint(struct mountpoint *mp, struct list_head *list)
789 if (!--mp->m_count) {
790 struct dentry *dentry = mp->m_dentry;
791 BUG_ON(!hlist_empty(&mp->m_list));
792 spin_lock(&dentry->d_lock);
793 dentry->d_flags &= ~DCACHE_MOUNTED;
794 spin_unlock(&dentry->d_lock);
795 dput_to_list(dentry, list);
796 hlist_del(&mp->m_hash);
801 /* called with namespace_lock and vfsmount lock */
802 static void put_mountpoint(struct mountpoint *mp)
804 __put_mountpoint(mp, &ex_mountpoints);
807 static inline int check_mnt(struct mount *mnt)
809 return mnt->mnt_ns == current->nsproxy->mnt_ns;
813 * vfsmount lock must be held for write
815 static void touch_mnt_namespace(struct mnt_namespace *ns)
819 wake_up_interruptible(&ns->poll);
824 * vfsmount lock must be held for write
826 static void __touch_mnt_namespace(struct mnt_namespace *ns)
828 if (ns && ns->event != event) {
830 wake_up_interruptible(&ns->poll);
835 * vfsmount lock must be held for write
837 static struct mountpoint *unhash_mnt(struct mount *mnt)
839 struct mountpoint *mp;
840 mnt->mnt_parent = mnt;
841 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
842 list_del_init(&mnt->mnt_child);
843 hlist_del_init_rcu(&mnt->mnt_hash);
844 hlist_del_init(&mnt->mnt_mp_list);
851 * vfsmount lock must be held for write
853 static void umount_mnt(struct mount *mnt)
855 put_mountpoint(unhash_mnt(mnt));
859 * vfsmount lock must be held for write
861 void mnt_set_mountpoint(struct mount *mnt,
862 struct mountpoint *mp,
863 struct mount *child_mnt)
866 mnt_add_count(mnt, 1); /* essentially, that's mntget */
867 child_mnt->mnt_mountpoint = mp->m_dentry;
868 child_mnt->mnt_parent = mnt;
869 child_mnt->mnt_mp = mp;
870 hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
873 static void __attach_mnt(struct mount *mnt, struct mount *parent)
875 hlist_add_head_rcu(&mnt->mnt_hash,
876 m_hash(&parent->mnt, mnt->mnt_mountpoint));
877 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
881 * vfsmount lock must be held for write
883 static void attach_mnt(struct mount *mnt,
884 struct mount *parent,
885 struct mountpoint *mp)
887 mnt_set_mountpoint(parent, mp, mnt);
888 __attach_mnt(mnt, parent);
891 void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
893 struct mountpoint *old_mp = mnt->mnt_mp;
894 struct mount *old_parent = mnt->mnt_parent;
896 list_del_init(&mnt->mnt_child);
897 hlist_del_init(&mnt->mnt_mp_list);
898 hlist_del_init_rcu(&mnt->mnt_hash);
900 attach_mnt(mnt, parent, mp);
902 put_mountpoint(old_mp);
903 mnt_add_count(old_parent, -1);
907 * vfsmount lock must be held for write
909 static void commit_tree(struct mount *mnt)
911 struct mount *parent = mnt->mnt_parent;
914 struct mnt_namespace *n = parent->mnt_ns;
916 BUG_ON(parent == mnt);
918 list_add_tail(&head, &mnt->mnt_list);
919 list_for_each_entry(m, &head, mnt_list)
922 list_splice(&head, n->list.prev);
924 n->mounts += n->pending_mounts;
925 n->pending_mounts = 0;
927 __attach_mnt(mnt, parent);
928 touch_mnt_namespace(n);
931 static struct mount *next_mnt(struct mount *p, struct mount *root)
933 struct list_head *next = p->mnt_mounts.next;
934 if (next == &p->mnt_mounts) {
938 next = p->mnt_child.next;
939 if (next != &p->mnt_parent->mnt_mounts)
944 return list_entry(next, struct mount, mnt_child);
947 static struct mount *skip_mnt_tree(struct mount *p)
949 struct list_head *prev = p->mnt_mounts.prev;
950 while (prev != &p->mnt_mounts) {
951 p = list_entry(prev, struct mount, mnt_child);
952 prev = p->mnt_mounts.prev;
958 * vfs_create_mount - Create a mount for a configured superblock
959 * @fc: The configuration context with the superblock attached
961 * Create a mount to an already configured superblock. If necessary, the
962 * caller should invoke vfs_get_tree() before calling this.
964 * Note that this does not attach the mount to anything.
966 struct vfsmount *vfs_create_mount(struct fs_context *fc)
969 struct user_namespace *fs_userns;
972 return ERR_PTR(-EINVAL);
974 mnt = alloc_vfsmnt(fc->source ?: "none");
976 return ERR_PTR(-ENOMEM);
978 if (fc->sb_flags & SB_KERNMOUNT)
979 mnt->mnt.mnt_flags = MNT_INTERNAL;
981 atomic_inc(&fc->root->d_sb->s_active);
982 mnt->mnt.mnt_sb = fc->root->d_sb;
983 mnt->mnt.mnt_root = dget(fc->root);
984 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
985 mnt->mnt_parent = mnt;
987 fs_userns = mnt->mnt.mnt_sb->s_user_ns;
988 if (!initial_idmapping(fs_userns))
989 mnt->mnt.mnt_userns = get_user_ns(fs_userns);
992 list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts);
996 EXPORT_SYMBOL(vfs_create_mount);
998 struct vfsmount *fc_mount(struct fs_context *fc)
1000 int err = vfs_get_tree(fc);
1002 up_write(&fc->root->d_sb->s_umount);
1003 return vfs_create_mount(fc);
1005 return ERR_PTR(err);
1007 EXPORT_SYMBOL(fc_mount);
1009 struct vfsmount *vfs_kern_mount(struct file_system_type *type,
1010 int flags, const char *name,
1013 struct fs_context *fc;
1014 struct vfsmount *mnt;
1018 return ERR_PTR(-EINVAL);
1020 fc = fs_context_for_mount(type, flags);
1022 return ERR_CAST(fc);
1025 ret = vfs_parse_fs_string(fc, "source",
1026 name, strlen(name));
1028 ret = parse_monolithic_mount_data(fc, data);
1037 EXPORT_SYMBOL_GPL(vfs_kern_mount);
1040 vfs_submount(const struct dentry *mountpoint, struct file_system_type *type,
1041 const char *name, void *data)
1043 /* Until it is worked out how to pass the user namespace
1044 * through from the parent mount to the submount don't support
1045 * unprivileged mounts with submounts.
1047 if (mountpoint->d_sb->s_user_ns != &init_user_ns)
1048 return ERR_PTR(-EPERM);
1050 return vfs_kern_mount(type, SB_SUBMOUNT, name, data);
1052 EXPORT_SYMBOL_GPL(vfs_submount);
1054 static struct mount *clone_mnt(struct mount *old, struct dentry *root,
1057 struct super_block *sb = old->mnt.mnt_sb;
1061 mnt = alloc_vfsmnt(old->mnt_devname);
1063 return ERR_PTR(-ENOMEM);
1065 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
1066 mnt->mnt_group_id = 0; /* not a peer of original */
1068 mnt->mnt_group_id = old->mnt_group_id;
1070 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
1071 err = mnt_alloc_group_id(mnt);
1076 mnt->mnt.mnt_flags = old->mnt.mnt_flags;
1077 mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL);
1079 atomic_inc(&sb->s_active);
1080 mnt->mnt.mnt_userns = mnt_user_ns(&old->mnt);
1081 if (!initial_idmapping(mnt->mnt.mnt_userns))
1082 mnt->mnt.mnt_userns = get_user_ns(mnt->mnt.mnt_userns);
1083 mnt->mnt.mnt_sb = sb;
1084 mnt->mnt.mnt_root = dget(root);
1085 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1086 mnt->mnt_parent = mnt;
1088 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
1089 unlock_mount_hash();
1091 if ((flag & CL_SLAVE) ||
1092 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
1093 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
1094 mnt->mnt_master = old;
1095 CLEAR_MNT_SHARED(mnt);
1096 } else if (!(flag & CL_PRIVATE)) {
1097 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
1098 list_add(&mnt->mnt_share, &old->mnt_share);
1099 if (IS_MNT_SLAVE(old))
1100 list_add(&mnt->mnt_slave, &old->mnt_slave);
1101 mnt->mnt_master = old->mnt_master;
1103 CLEAR_MNT_SHARED(mnt);
1105 if (flag & CL_MAKE_SHARED)
1106 set_mnt_shared(mnt);
1108 /* stick the duplicate mount on the same expiry list
1109 * as the original if that was on one */
1110 if (flag & CL_EXPIRE) {
1111 if (!list_empty(&old->mnt_expire))
1112 list_add(&mnt->mnt_expire, &old->mnt_expire);
1120 return ERR_PTR(err);
1123 static void cleanup_mnt(struct mount *mnt)
1125 struct hlist_node *p;
1128 * The warning here probably indicates that somebody messed
1129 * up a mnt_want/drop_write() pair. If this happens, the
1130 * filesystem was probably unable to make r/w->r/o transitions.
1131 * The locking used to deal with mnt_count decrement provides barriers,
1132 * so mnt_get_writers() below is safe.
1134 WARN_ON(mnt_get_writers(mnt));
1135 if (unlikely(mnt->mnt_pins.first))
1137 hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) {
1138 hlist_del(&m->mnt_umount);
1141 fsnotify_vfsmount_delete(&mnt->mnt);
1142 dput(mnt->mnt.mnt_root);
1143 deactivate_super(mnt->mnt.mnt_sb);
1145 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
1148 static void __cleanup_mnt(struct rcu_head *head)
1150 cleanup_mnt(container_of(head, struct mount, mnt_rcu));
1153 static LLIST_HEAD(delayed_mntput_list);
1154 static void delayed_mntput(struct work_struct *unused)
1156 struct llist_node *node = llist_del_all(&delayed_mntput_list);
1157 struct mount *m, *t;
1159 llist_for_each_entry_safe(m, t, node, mnt_llist)
1162 static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput);
1164 static void mntput_no_expire(struct mount *mnt)
1170 if (likely(READ_ONCE(mnt->mnt_ns))) {
1172 * Since we don't do lock_mount_hash() here,
1173 * ->mnt_ns can change under us. However, if it's
1174 * non-NULL, then there's a reference that won't
1175 * be dropped until after an RCU delay done after
1176 * turning ->mnt_ns NULL. So if we observe it
1177 * non-NULL under rcu_read_lock(), the reference
1178 * we are dropping is not the final one.
1180 mnt_add_count(mnt, -1);
1186 * make sure that if __legitimize_mnt() has not seen us grab
1187 * mount_lock, we'll see their refcount increment here.
1190 mnt_add_count(mnt, -1);
1191 count = mnt_get_count(mnt);
1195 unlock_mount_hash();
1198 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
1200 unlock_mount_hash();
1203 mnt->mnt.mnt_flags |= MNT_DOOMED;
1206 list_del(&mnt->mnt_instance);
1208 if (unlikely(!list_empty(&mnt->mnt_mounts))) {
1209 struct mount *p, *tmp;
1210 list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) {
1211 __put_mountpoint(unhash_mnt(p), &list);
1212 hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children);
1215 unlock_mount_hash();
1216 shrink_dentry_list(&list);
1218 if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) {
1219 struct task_struct *task = current;
1220 if (likely(!(task->flags & PF_KTHREAD))) {
1221 init_task_work(&mnt->mnt_rcu, __cleanup_mnt);
1222 if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME))
1225 if (llist_add(&mnt->mnt_llist, &delayed_mntput_list))
1226 schedule_delayed_work(&delayed_mntput_work, 1);
1232 void mntput(struct vfsmount *mnt)
1235 struct mount *m = real_mount(mnt);
1236 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1237 if (unlikely(m->mnt_expiry_mark))
1238 m->mnt_expiry_mark = 0;
1239 mntput_no_expire(m);
1242 EXPORT_SYMBOL(mntput);
1244 struct vfsmount *mntget(struct vfsmount *mnt)
1247 mnt_add_count(real_mount(mnt), 1);
1250 EXPORT_SYMBOL(mntget);
1253 * path_is_mountpoint() - Check if path is a mount in the current namespace.
1254 * @path: path to check
1256 * d_mountpoint() can only be used reliably to establish if a dentry is
1257 * not mounted in any namespace and that common case is handled inline.
1258 * d_mountpoint() isn't aware of the possibility there may be multiple
1259 * mounts using a given dentry in a different namespace. This function
1260 * checks if the passed in path is a mountpoint rather than the dentry
1263 bool path_is_mountpoint(const struct path *path)
1268 if (!d_mountpoint(path->dentry))
1273 seq = read_seqbegin(&mount_lock);
1274 res = __path_is_mountpoint(path);
1275 } while (read_seqretry(&mount_lock, seq));
1280 EXPORT_SYMBOL(path_is_mountpoint);
1282 struct vfsmount *mnt_clone_internal(const struct path *path)
1285 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
1288 p->mnt.mnt_flags |= MNT_INTERNAL;
1292 #ifdef CONFIG_PROC_FS
1293 static struct mount *mnt_list_next(struct mnt_namespace *ns,
1294 struct list_head *p)
1296 struct mount *mnt, *ret = NULL;
1299 list_for_each_continue(p, &ns->list) {
1300 mnt = list_entry(p, typeof(*mnt), mnt_list);
1301 if (!mnt_is_cursor(mnt)) {
1311 /* iterator; we want it to have access to namespace_sem, thus here... */
1312 static void *m_start(struct seq_file *m, loff_t *pos)
1314 struct proc_mounts *p = m->private;
1315 struct list_head *prev;
1317 down_read(&namespace_sem);
1319 prev = &p->ns->list;
1321 prev = &p->cursor.mnt_list;
1323 /* Read after we'd reached the end? */
1324 if (list_empty(prev))
1328 return mnt_list_next(p->ns, prev);
1331 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1333 struct proc_mounts *p = m->private;
1334 struct mount *mnt = v;
1337 return mnt_list_next(p->ns, &mnt->mnt_list);
1340 static void m_stop(struct seq_file *m, void *v)
1342 struct proc_mounts *p = m->private;
1343 struct mount *mnt = v;
1345 lock_ns_list(p->ns);
1347 list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list);
1349 list_del_init(&p->cursor.mnt_list);
1350 unlock_ns_list(p->ns);
1351 up_read(&namespace_sem);
1354 static int m_show(struct seq_file *m, void *v)
1356 struct proc_mounts *p = m->private;
1357 struct mount *r = v;
1358 return p->show(m, &r->mnt);
1361 const struct seq_operations mounts_op = {
1368 void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor)
1370 down_read(&namespace_sem);
1372 list_del(&cursor->mnt_list);
1374 up_read(&namespace_sem);
1376 #endif /* CONFIG_PROC_FS */
1379 * may_umount_tree - check if a mount tree is busy
1380 * @m: root of mount tree
1382 * This is called to check if a tree of mounts has any
1383 * open files, pwds, chroots or sub mounts that are
1386 int may_umount_tree(struct vfsmount *m)
1388 struct mount *mnt = real_mount(m);
1389 int actual_refs = 0;
1390 int minimum_refs = 0;
1394 /* write lock needed for mnt_get_count */
1396 for (p = mnt; p; p = next_mnt(p, mnt)) {
1397 actual_refs += mnt_get_count(p);
1400 unlock_mount_hash();
1402 if (actual_refs > minimum_refs)
1408 EXPORT_SYMBOL(may_umount_tree);
1411 * may_umount - check if a mount point is busy
1412 * @mnt: root of mount
1414 * This is called to check if a mount point has any
1415 * open files, pwds, chroots or sub mounts. If the
1416 * mount has sub mounts this will return busy
1417 * regardless of whether the sub mounts are busy.
1419 * Doesn't take quota and stuff into account. IOW, in some cases it will
1420 * give false negatives. The main reason why it's here is that we need
1421 * a non-destructive way to look for easily umountable filesystems.
1423 int may_umount(struct vfsmount *mnt)
1426 down_read(&namespace_sem);
1428 if (propagate_mount_busy(real_mount(mnt), 2))
1430 unlock_mount_hash();
1431 up_read(&namespace_sem);
1435 EXPORT_SYMBOL(may_umount);
1437 static void namespace_unlock(void)
1439 struct hlist_head head;
1440 struct hlist_node *p;
1444 hlist_move_list(&unmounted, &head);
1445 list_splice_init(&ex_mountpoints, &list);
1447 up_write(&namespace_sem);
1449 shrink_dentry_list(&list);
1451 if (likely(hlist_empty(&head)))
1454 synchronize_rcu_expedited();
1456 hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
1457 hlist_del(&m->mnt_umount);
1462 static inline void namespace_lock(void)
1464 down_write(&namespace_sem);
1467 enum umount_tree_flags {
1469 UMOUNT_PROPAGATE = 2,
1470 UMOUNT_CONNECTED = 4,
1473 static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how)
1475 /* Leaving mounts connected is only valid for lazy umounts */
1476 if (how & UMOUNT_SYNC)
1479 /* A mount without a parent has nothing to be connected to */
1480 if (!mnt_has_parent(mnt))
1483 /* Because the reference counting rules change when mounts are
1484 * unmounted and connected, umounted mounts may not be
1485 * connected to mounted mounts.
1487 if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT))
1490 /* Has it been requested that the mount remain connected? */
1491 if (how & UMOUNT_CONNECTED)
1494 /* Is the mount locked such that it needs to remain connected? */
1495 if (IS_MNT_LOCKED(mnt))
1498 /* By default disconnect the mount */
1503 * mount_lock must be held
1504 * namespace_sem must be held for write
1506 static void umount_tree(struct mount *mnt, enum umount_tree_flags how)
1508 LIST_HEAD(tmp_list);
1511 if (how & UMOUNT_PROPAGATE)
1512 propagate_mount_unlock(mnt);
1514 /* Gather the mounts to umount */
1515 for (p = mnt; p; p = next_mnt(p, mnt)) {
1516 p->mnt.mnt_flags |= MNT_UMOUNT;
1517 list_move(&p->mnt_list, &tmp_list);
1520 /* Hide the mounts from mnt_mounts */
1521 list_for_each_entry(p, &tmp_list, mnt_list) {
1522 list_del_init(&p->mnt_child);
1525 /* Add propogated mounts to the tmp_list */
1526 if (how & UMOUNT_PROPAGATE)
1527 propagate_umount(&tmp_list);
1529 while (!list_empty(&tmp_list)) {
1530 struct mnt_namespace *ns;
1532 p = list_first_entry(&tmp_list, struct mount, mnt_list);
1533 list_del_init(&p->mnt_expire);
1534 list_del_init(&p->mnt_list);
1538 __touch_mnt_namespace(ns);
1541 if (how & UMOUNT_SYNC)
1542 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1544 disconnect = disconnect_mount(p, how);
1545 if (mnt_has_parent(p)) {
1546 mnt_add_count(p->mnt_parent, -1);
1548 /* Don't forget about p */
1549 list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts);
1554 change_mnt_propagation(p, MS_PRIVATE);
1556 hlist_add_head(&p->mnt_umount, &unmounted);
1560 static void shrink_submounts(struct mount *mnt);
1562 static int do_umount_root(struct super_block *sb)
1566 down_write(&sb->s_umount);
1567 if (!sb_rdonly(sb)) {
1568 struct fs_context *fc;
1570 fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY,
1575 ret = parse_monolithic_mount_data(fc, NULL);
1577 ret = reconfigure_super(fc);
1581 up_write(&sb->s_umount);
1585 static int do_umount(struct mount *mnt, int flags)
1587 struct super_block *sb = mnt->mnt.mnt_sb;
1590 retval = security_sb_umount(&mnt->mnt, flags);
1595 * Allow userspace to request a mountpoint be expired rather than
1596 * unmounting unconditionally. Unmount only happens if:
1597 * (1) the mark is already set (the mark is cleared by mntput())
1598 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1600 if (flags & MNT_EXPIRE) {
1601 if (&mnt->mnt == current->fs->root.mnt ||
1602 flags & (MNT_FORCE | MNT_DETACH))
1606 * probably don't strictly need the lock here if we examined
1607 * all race cases, but it's a slowpath.
1610 if (mnt_get_count(mnt) != 2) {
1611 unlock_mount_hash();
1614 unlock_mount_hash();
1616 if (!xchg(&mnt->mnt_expiry_mark, 1))
1621 * If we may have to abort operations to get out of this
1622 * mount, and they will themselves hold resources we must
1623 * allow the fs to do things. In the Unix tradition of
1624 * 'Gee thats tricky lets do it in userspace' the umount_begin
1625 * might fail to complete on the first run through as other tasks
1626 * must return, and the like. Thats for the mount program to worry
1627 * about for the moment.
1630 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1631 sb->s_op->umount_begin(sb);
1635 * No sense to grab the lock for this test, but test itself looks
1636 * somewhat bogus. Suggestions for better replacement?
1637 * Ho-hum... In principle, we might treat that as umount + switch
1638 * to rootfs. GC would eventually take care of the old vfsmount.
1639 * Actually it makes sense, especially if rootfs would contain a
1640 * /reboot - static binary that would close all descriptors and
1641 * call reboot(9). Then init(8) could umount root and exec /reboot.
1643 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1645 * Special case for "unmounting" root ...
1646 * we just try to remount it readonly.
1648 if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
1650 return do_umount_root(sb);
1656 /* Recheck MNT_LOCKED with the locks held */
1658 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1662 if (flags & MNT_DETACH) {
1663 if (!list_empty(&mnt->mnt_list))
1664 umount_tree(mnt, UMOUNT_PROPAGATE);
1667 shrink_submounts(mnt);
1669 if (!propagate_mount_busy(mnt, 2)) {
1670 if (!list_empty(&mnt->mnt_list))
1671 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
1676 unlock_mount_hash();
1682 * __detach_mounts - lazily unmount all mounts on the specified dentry
1684 * During unlink, rmdir, and d_drop it is possible to loose the path
1685 * to an existing mountpoint, and wind up leaking the mount.
1686 * detach_mounts allows lazily unmounting those mounts instead of
1689 * The caller may hold dentry->d_inode->i_mutex.
1691 void __detach_mounts(struct dentry *dentry)
1693 struct mountpoint *mp;
1698 mp = lookup_mountpoint(dentry);
1703 while (!hlist_empty(&mp->m_list)) {
1704 mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
1705 if (mnt->mnt.mnt_flags & MNT_UMOUNT) {
1707 hlist_add_head(&mnt->mnt_umount, &unmounted);
1709 else umount_tree(mnt, UMOUNT_CONNECTED);
1713 unlock_mount_hash();
1718 * Is the caller allowed to modify his namespace?
1720 static inline bool may_mount(void)
1722 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1725 static void warn_mandlock(void)
1727 pr_warn_once("=======================================================\n"
1728 "WARNING: The mand mount option has been deprecated and\n"
1729 " and is ignored by this kernel. Remove the mand\n"
1730 " option from the mount to silence this warning.\n"
1731 "=======================================================\n");
1734 static int can_umount(const struct path *path, int flags)
1736 struct mount *mnt = real_mount(path->mnt);
1740 if (path->dentry != path->mnt->mnt_root)
1742 if (!check_mnt(mnt))
1744 if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */
1746 if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN))
1751 // caller is responsible for flags being sane
1752 int path_umount(struct path *path, int flags)
1754 struct mount *mnt = real_mount(path->mnt);
1757 ret = can_umount(path, flags);
1759 ret = do_umount(mnt, flags);
1761 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1763 mntput_no_expire(mnt);
1767 static int ksys_umount(char __user *name, int flags)
1769 int lookup_flags = LOOKUP_MOUNTPOINT;
1773 // basic validity checks done first
1774 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1777 if (!(flags & UMOUNT_NOFOLLOW))
1778 lookup_flags |= LOOKUP_FOLLOW;
1779 ret = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1782 return path_umount(&path, flags);
1785 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1787 return ksys_umount(name, flags);
1790 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1793 * The 2.0 compatible umount. No flags.
1795 SYSCALL_DEFINE1(oldumount, char __user *, name)
1797 return ksys_umount(name, 0);
1802 static bool is_mnt_ns_file(struct dentry *dentry)
1804 /* Is this a proxy for a mount namespace? */
1805 return dentry->d_op == &ns_dentry_operations &&
1806 dentry->d_fsdata == &mntns_operations;
1809 static struct mnt_namespace *to_mnt_ns(struct ns_common *ns)
1811 return container_of(ns, struct mnt_namespace, ns);
1814 struct ns_common *from_mnt_ns(struct mnt_namespace *mnt)
1819 static bool mnt_ns_loop(struct dentry *dentry)
1821 /* Could bind mounting the mount namespace inode cause a
1822 * mount namespace loop?
1824 struct mnt_namespace *mnt_ns;
1825 if (!is_mnt_ns_file(dentry))
1828 mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode));
1829 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1832 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1835 struct mount *res, *p, *q, *r, *parent;
1837 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1838 return ERR_PTR(-EINVAL);
1840 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1841 return ERR_PTR(-EINVAL);
1843 res = q = clone_mnt(mnt, dentry, flag);
1847 q->mnt_mountpoint = mnt->mnt_mountpoint;
1850 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1852 if (!is_subdir(r->mnt_mountpoint, dentry))
1855 for (s = r; s; s = next_mnt(s, r)) {
1856 if (!(flag & CL_COPY_UNBINDABLE) &&
1857 IS_MNT_UNBINDABLE(s)) {
1858 if (s->mnt.mnt_flags & MNT_LOCKED) {
1859 /* Both unbindable and locked. */
1860 q = ERR_PTR(-EPERM);
1863 s = skip_mnt_tree(s);
1867 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1868 is_mnt_ns_file(s->mnt.mnt_root)) {
1869 s = skip_mnt_tree(s);
1872 while (p != s->mnt_parent) {
1878 q = clone_mnt(p, p->mnt.mnt_root, flag);
1882 list_add_tail(&q->mnt_list, &res->mnt_list);
1883 attach_mnt(q, parent, p->mnt_mp);
1884 unlock_mount_hash();
1891 umount_tree(res, UMOUNT_SYNC);
1892 unlock_mount_hash();
1897 /* Caller should check returned pointer for errors */
1899 struct vfsmount *collect_mounts(const struct path *path)
1903 if (!check_mnt(real_mount(path->mnt)))
1904 tree = ERR_PTR(-EINVAL);
1906 tree = copy_tree(real_mount(path->mnt), path->dentry,
1907 CL_COPY_ALL | CL_PRIVATE);
1910 return ERR_CAST(tree);
1913 EXPORT_SYMBOL_GPL(collect_mounts);
1915 static void free_mnt_ns(struct mnt_namespace *);
1916 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool);
1918 void dissolve_on_fput(struct vfsmount *mnt)
1920 struct mnt_namespace *ns;
1923 ns = real_mount(mnt)->mnt_ns;
1926 umount_tree(real_mount(mnt), UMOUNT_CONNECTED);
1930 unlock_mount_hash();
1936 void drop_collected_mounts(struct vfsmount *mnt)
1940 umount_tree(real_mount(mnt), 0);
1941 unlock_mount_hash();
1944 EXPORT_SYMBOL_GPL(drop_collected_mounts);
1946 static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
1948 struct mount *child;
1950 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
1951 if (!is_subdir(child->mnt_mountpoint, dentry))
1954 if (child->mnt.mnt_flags & MNT_LOCKED)
1961 * clone_private_mount - create a private clone of a path
1962 * @path: path to clone
1964 * This creates a new vfsmount, which will be the clone of @path. The new mount
1965 * will not be attached anywhere in the namespace and will be private (i.e.
1966 * changes to the originating mount won't be propagated into this).
1968 * Release with mntput().
1970 struct vfsmount *clone_private_mount(const struct path *path)
1972 struct mount *old_mnt = real_mount(path->mnt);
1973 struct mount *new_mnt;
1975 down_read(&namespace_sem);
1976 if (IS_MNT_UNBINDABLE(old_mnt))
1979 if (!check_mnt(old_mnt))
1982 if (has_locked_children(old_mnt, path->dentry))
1985 new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE);
1986 up_read(&namespace_sem);
1988 if (IS_ERR(new_mnt))
1989 return ERR_CAST(new_mnt);
1991 /* Longterm mount to be removed by kern_unmount*() */
1992 new_mnt->mnt_ns = MNT_NS_INTERNAL;
1994 return &new_mnt->mnt;
1997 up_read(&namespace_sem);
1998 return ERR_PTR(-EINVAL);
2000 EXPORT_SYMBOL_GPL(clone_private_mount);
2002 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
2003 struct vfsmount *root)
2006 int res = f(root, arg);
2009 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
2010 res = f(&mnt->mnt, arg);
2016 EXPORT_SYMBOL_GPL(iterate_mounts);
2018 static void lock_mnt_tree(struct mount *mnt)
2022 for (p = mnt; p; p = next_mnt(p, mnt)) {
2023 int flags = p->mnt.mnt_flags;
2024 /* Don't allow unprivileged users to change mount flags */
2025 flags |= MNT_LOCK_ATIME;
2027 if (flags & MNT_READONLY)
2028 flags |= MNT_LOCK_READONLY;
2030 if (flags & MNT_NODEV)
2031 flags |= MNT_LOCK_NODEV;
2033 if (flags & MNT_NOSUID)
2034 flags |= MNT_LOCK_NOSUID;
2036 if (flags & MNT_NOEXEC)
2037 flags |= MNT_LOCK_NOEXEC;
2038 /* Don't allow unprivileged users to reveal what is under a mount */
2039 if (list_empty(&p->mnt_expire))
2040 flags |= MNT_LOCKED;
2041 p->mnt.mnt_flags = flags;
2045 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
2049 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
2050 if (p->mnt_group_id && !IS_MNT_SHARED(p))
2051 mnt_release_group_id(p);
2055 static int invent_group_ids(struct mount *mnt, bool recurse)
2059 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
2060 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
2061 int err = mnt_alloc_group_id(p);
2063 cleanup_group_ids(mnt, p);
2072 int count_mounts(struct mnt_namespace *ns, struct mount *mnt)
2074 unsigned int max = READ_ONCE(sysctl_mount_max);
2075 unsigned int mounts = 0, old, pending, sum;
2078 for (p = mnt; p; p = next_mnt(p, mnt))
2082 pending = ns->pending_mounts;
2083 sum = old + pending;
2087 (mounts > (max - sum)))
2090 ns->pending_mounts = pending + mounts;
2095 * @source_mnt : mount tree to be attached
2096 * @nd : place the mount tree @source_mnt is attached
2097 * @parent_nd : if non-null, detach the source_mnt from its parent and
2098 * store the parent mount and mountpoint dentry.
2099 * (done when source_mnt is moved)
2101 * NOTE: in the table below explains the semantics when a source mount
2102 * of a given type is attached to a destination mount of a given type.
2103 * ---------------------------------------------------------------------------
2104 * | BIND MOUNT OPERATION |
2105 * |**************************************************************************
2106 * | source-->| shared | private | slave | unbindable |
2110 * |**************************************************************************
2111 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
2113 * |non-shared| shared (+) | private | slave (*) | invalid |
2114 * ***************************************************************************
2115 * A bind operation clones the source mount and mounts the clone on the
2116 * destination mount.
2118 * (++) the cloned mount is propagated to all the mounts in the propagation
2119 * tree of the destination mount and the cloned mount is added to
2120 * the peer group of the source mount.
2121 * (+) the cloned mount is created under the destination mount and is marked
2122 * as shared. The cloned mount is added to the peer group of the source
2124 * (+++) the mount is propagated to all the mounts in the propagation tree
2125 * of the destination mount and the cloned mount is made slave
2126 * of the same master as that of the source mount. The cloned mount
2127 * is marked as 'shared and slave'.
2128 * (*) the cloned mount is made a slave of the same master as that of the
2131 * ---------------------------------------------------------------------------
2132 * | MOVE MOUNT OPERATION |
2133 * |**************************************************************************
2134 * | source-->| shared | private | slave | unbindable |
2138 * |**************************************************************************
2139 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
2141 * |non-shared| shared (+*) | private | slave (*) | unbindable |
2142 * ***************************************************************************
2144 * (+) the mount is moved to the destination. And is then propagated to
2145 * all the mounts in the propagation tree of the destination mount.
2146 * (+*) the mount is moved to the destination.
2147 * (+++) the mount is moved to the destination and is then propagated to
2148 * all the mounts belonging to the destination mount's propagation tree.
2149 * the mount is marked as 'shared and slave'.
2150 * (*) the mount continues to be a slave at the new location.
2152 * if the source mount is a tree, the operations explained above is
2153 * applied to each mount in the tree.
2154 * Must be called without spinlocks held, since this function can sleep
2157 static int attach_recursive_mnt(struct mount *source_mnt,
2158 struct mount *dest_mnt,
2159 struct mountpoint *dest_mp,
2162 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2163 HLIST_HEAD(tree_list);
2164 struct mnt_namespace *ns = dest_mnt->mnt_ns;
2165 struct mountpoint *smp;
2166 struct mount *child, *p;
2167 struct hlist_node *n;
2170 /* Preallocate a mountpoint in case the new mounts need
2171 * to be tucked under other mounts.
2173 smp = get_mountpoint(source_mnt->mnt.mnt_root);
2175 return PTR_ERR(smp);
2177 /* Is there space to add these mounts to the mount namespace? */
2179 err = count_mounts(ns, source_mnt);
2184 if (IS_MNT_SHARED(dest_mnt)) {
2185 err = invent_group_ids(source_mnt, true);
2188 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
2191 goto out_cleanup_ids;
2192 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
2198 unhash_mnt(source_mnt);
2199 attach_mnt(source_mnt, dest_mnt, dest_mp);
2200 touch_mnt_namespace(source_mnt->mnt_ns);
2202 if (source_mnt->mnt_ns) {
2203 /* move from anon - the caller will destroy */
2204 list_del_init(&source_mnt->mnt_ns->list);
2206 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
2207 commit_tree(source_mnt);
2210 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
2212 hlist_del_init(&child->mnt_hash);
2213 q = __lookup_mnt(&child->mnt_parent->mnt,
2214 child->mnt_mountpoint);
2216 mnt_change_mountpoint(child, smp, q);
2217 /* Notice when we are propagating across user namespaces */
2218 if (child->mnt_parent->mnt_ns->user_ns != user_ns)
2219 lock_mnt_tree(child);
2220 child->mnt.mnt_flags &= ~MNT_LOCKED;
2223 put_mountpoint(smp);
2224 unlock_mount_hash();
2229 while (!hlist_empty(&tree_list)) {
2230 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
2231 child->mnt_parent->mnt_ns->pending_mounts = 0;
2232 umount_tree(child, UMOUNT_SYNC);
2234 unlock_mount_hash();
2235 cleanup_group_ids(source_mnt, NULL);
2237 ns->pending_mounts = 0;
2239 read_seqlock_excl(&mount_lock);
2240 put_mountpoint(smp);
2241 read_sequnlock_excl(&mount_lock);
2246 static struct mountpoint *lock_mount(struct path *path)
2248 struct vfsmount *mnt;
2249 struct dentry *dentry = path->dentry;
2251 inode_lock(dentry->d_inode);
2252 if (unlikely(cant_mount(dentry))) {
2253 inode_unlock(dentry->d_inode);
2254 return ERR_PTR(-ENOENT);
2257 mnt = lookup_mnt(path);
2259 struct mountpoint *mp = get_mountpoint(dentry);
2262 inode_unlock(dentry->d_inode);
2268 inode_unlock(path->dentry->d_inode);
2271 dentry = path->dentry = dget(mnt->mnt_root);
2275 static void unlock_mount(struct mountpoint *where)
2277 struct dentry *dentry = where->m_dentry;
2279 read_seqlock_excl(&mount_lock);
2280 put_mountpoint(where);
2281 read_sequnlock_excl(&mount_lock);
2284 inode_unlock(dentry->d_inode);
2287 static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
2289 if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER)
2292 if (d_is_dir(mp->m_dentry) !=
2293 d_is_dir(mnt->mnt.mnt_root))
2296 return attach_recursive_mnt(mnt, p, mp, false);
2300 * Sanity check the flags to change_mnt_propagation.
2303 static int flags_to_propagation_type(int ms_flags)
2305 int type = ms_flags & ~(MS_REC | MS_SILENT);
2307 /* Fail if any non-propagation flags are set */
2308 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2310 /* Only one propagation flag should be set */
2311 if (!is_power_of_2(type))
2317 * recursively change the type of the mountpoint.
2319 static int do_change_type(struct path *path, int ms_flags)
2322 struct mount *mnt = real_mount(path->mnt);
2323 int recurse = ms_flags & MS_REC;
2327 if (path->dentry != path->mnt->mnt_root)
2330 type = flags_to_propagation_type(ms_flags);
2335 if (type == MS_SHARED) {
2336 err = invent_group_ids(mnt, recurse);
2342 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
2343 change_mnt_propagation(m, type);
2344 unlock_mount_hash();
2351 static struct mount *__do_loopback(struct path *old_path, int recurse)
2353 struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt);
2355 if (IS_MNT_UNBINDABLE(old))
2358 if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations)
2361 if (!recurse && has_locked_children(old, old_path->dentry))
2365 mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE);
2367 mnt = clone_mnt(old, old_path->dentry, 0);
2370 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2376 * do loopback mount.
2378 static int do_loopback(struct path *path, const char *old_name,
2381 struct path old_path;
2382 struct mount *mnt = NULL, *parent;
2383 struct mountpoint *mp;
2385 if (!old_name || !*old_name)
2387 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
2392 if (mnt_ns_loop(old_path.dentry))
2395 mp = lock_mount(path);
2401 parent = real_mount(path->mnt);
2402 if (!check_mnt(parent))
2405 mnt = __do_loopback(&old_path, recurse);
2411 err = graft_tree(mnt, parent, mp);
2414 umount_tree(mnt, UMOUNT_SYNC);
2415 unlock_mount_hash();
2420 path_put(&old_path);
2424 static struct file *open_detached_copy(struct path *path, bool recursive)
2426 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2427 struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true);
2428 struct mount *mnt, *p;
2432 return ERR_CAST(ns);
2435 mnt = __do_loopback(path, recursive);
2439 return ERR_CAST(mnt);
2443 for (p = mnt; p; p = next_mnt(p, mnt)) {
2448 list_add_tail(&ns->list, &mnt->mnt_list);
2450 unlock_mount_hash();
2454 path->mnt = &mnt->mnt;
2455 file = dentry_open(path, O_PATH, current_cred());
2457 dissolve_on_fput(path->mnt);
2459 file->f_mode |= FMODE_NEED_UNMOUNT;
2463 SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags)
2467 int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
2468 bool detached = flags & OPEN_TREE_CLONE;
2472 BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC);
2474 if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE |
2475 AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE |
2479 if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE)
2482 if (flags & AT_NO_AUTOMOUNT)
2483 lookup_flags &= ~LOOKUP_AUTOMOUNT;
2484 if (flags & AT_SYMLINK_NOFOLLOW)
2485 lookup_flags &= ~LOOKUP_FOLLOW;
2486 if (flags & AT_EMPTY_PATH)
2487 lookup_flags |= LOOKUP_EMPTY;
2489 if (detached && !may_mount())
2492 fd = get_unused_fd_flags(flags & O_CLOEXEC);
2496 error = user_path_at(dfd, filename, lookup_flags, &path);
2497 if (unlikely(error)) {
2498 file = ERR_PTR(error);
2501 file = open_detached_copy(&path, flags & AT_RECURSIVE);
2503 file = dentry_open(&path, O_PATH, current_cred());
2508 return PTR_ERR(file);
2510 fd_install(fd, file);
2515 * Don't allow locked mount flags to be cleared.
2517 * No locks need to be held here while testing the various MNT_LOCK
2518 * flags because those flags can never be cleared once they are set.
2520 static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags)
2522 unsigned int fl = mnt->mnt.mnt_flags;
2524 if ((fl & MNT_LOCK_READONLY) &&
2525 !(mnt_flags & MNT_READONLY))
2528 if ((fl & MNT_LOCK_NODEV) &&
2529 !(mnt_flags & MNT_NODEV))
2532 if ((fl & MNT_LOCK_NOSUID) &&
2533 !(mnt_flags & MNT_NOSUID))
2536 if ((fl & MNT_LOCK_NOEXEC) &&
2537 !(mnt_flags & MNT_NOEXEC))
2540 if ((fl & MNT_LOCK_ATIME) &&
2541 ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK)))
2547 static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags)
2549 bool readonly_request = (mnt_flags & MNT_READONLY);
2551 if (readonly_request == __mnt_is_readonly(&mnt->mnt))
2554 if (readonly_request)
2555 return mnt_make_readonly(mnt);
2557 mnt->mnt.mnt_flags &= ~MNT_READONLY;
2561 static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags)
2563 mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK;
2564 mnt->mnt.mnt_flags = mnt_flags;
2565 touch_mnt_namespace(mnt->mnt_ns);
2568 static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt)
2570 struct super_block *sb = mnt->mnt_sb;
2572 if (!__mnt_is_readonly(mnt) &&
2573 (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
2574 char *buf = (char *)__get_free_page(GFP_KERNEL);
2575 char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM);
2578 time64_to_tm(sb->s_time_max, 0, &tm);
2580 pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n",
2582 is_mounted(mnt) ? "remounted" : "mounted",
2584 tm.tm_year+1900, (unsigned long long)sb->s_time_max);
2586 free_page((unsigned long)buf);
2591 * Handle reconfiguration of the mountpoint only without alteration of the
2592 * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND
2595 static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags)
2597 struct super_block *sb = path->mnt->mnt_sb;
2598 struct mount *mnt = real_mount(path->mnt);
2601 if (!check_mnt(mnt))
2604 if (path->dentry != mnt->mnt.mnt_root)
2607 if (!can_change_locked_flags(mnt, mnt_flags))
2611 * We're only checking whether the superblock is read-only not
2612 * changing it, so only take down_read(&sb->s_umount).
2614 down_read(&sb->s_umount);
2616 ret = change_mount_ro_state(mnt, mnt_flags);
2618 set_mount_attributes(mnt, mnt_flags);
2619 unlock_mount_hash();
2620 up_read(&sb->s_umount);
2622 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2628 * change filesystem flags. dir should be a physical root of filesystem.
2629 * If you've mounted a non-root directory somewhere and want to do remount
2630 * on it - tough luck.
2632 static int do_remount(struct path *path, int ms_flags, int sb_flags,
2633 int mnt_flags, void *data)
2636 struct super_block *sb = path->mnt->mnt_sb;
2637 struct mount *mnt = real_mount(path->mnt);
2638 struct fs_context *fc;
2640 if (!check_mnt(mnt))
2643 if (path->dentry != path->mnt->mnt_root)
2646 if (!can_change_locked_flags(mnt, mnt_flags))
2649 fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK);
2654 err = parse_monolithic_mount_data(fc, data);
2656 down_write(&sb->s_umount);
2658 if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) {
2659 err = reconfigure_super(fc);
2662 set_mount_attributes(mnt, mnt_flags);
2663 unlock_mount_hash();
2666 up_write(&sb->s_umount);
2669 mnt_warn_timestamp_expiry(path, &mnt->mnt);
2675 static inline int tree_contains_unbindable(struct mount *mnt)
2678 for (p = mnt; p; p = next_mnt(p, mnt)) {
2679 if (IS_MNT_UNBINDABLE(p))
2686 * Check that there aren't references to earlier/same mount namespaces in the
2687 * specified subtree. Such references can act as pins for mount namespaces
2688 * that aren't checked by the mount-cycle checking code, thereby allowing
2689 * cycles to be made.
2691 static bool check_for_nsfs_mounts(struct mount *subtree)
2697 for (p = subtree; p; p = next_mnt(p, subtree))
2698 if (mnt_ns_loop(p->mnt.mnt_root))
2703 unlock_mount_hash();
2707 static int do_set_group(struct path *from_path, struct path *to_path)
2709 struct mount *from, *to;
2712 from = real_mount(from_path->mnt);
2713 to = real_mount(to_path->mnt);
2718 /* To and From must be mounted */
2719 if (!is_mounted(&from->mnt))
2721 if (!is_mounted(&to->mnt))
2725 /* We should be allowed to modify mount namespaces of both mounts */
2726 if (!ns_capable(from->mnt_ns->user_ns, CAP_SYS_ADMIN))
2728 if (!ns_capable(to->mnt_ns->user_ns, CAP_SYS_ADMIN))
2732 /* To and From paths should be mount roots */
2733 if (from_path->dentry != from_path->mnt->mnt_root)
2735 if (to_path->dentry != to_path->mnt->mnt_root)
2738 /* Setting sharing groups is only allowed across same superblock */
2739 if (from->mnt.mnt_sb != to->mnt.mnt_sb)
2742 /* From mount root should be wider than To mount root */
2743 if (!is_subdir(to->mnt.mnt_root, from->mnt.mnt_root))
2746 /* From mount should not have locked children in place of To's root */
2747 if (has_locked_children(from, to->mnt.mnt_root))
2750 /* Setting sharing groups is only allowed on private mounts */
2751 if (IS_MNT_SHARED(to) || IS_MNT_SLAVE(to))
2754 /* From should not be private */
2755 if (!IS_MNT_SHARED(from) && !IS_MNT_SLAVE(from))
2758 if (IS_MNT_SLAVE(from)) {
2759 struct mount *m = from->mnt_master;
2761 list_add(&to->mnt_slave, &m->mnt_slave_list);
2765 if (IS_MNT_SHARED(from)) {
2766 to->mnt_group_id = from->mnt_group_id;
2767 list_add(&to->mnt_share, &from->mnt_share);
2770 unlock_mount_hash();
2779 static int do_move_mount(struct path *old_path, struct path *new_path)
2781 struct mnt_namespace *ns;
2784 struct mount *parent;
2785 struct mountpoint *mp, *old_mp;
2789 mp = lock_mount(new_path);
2793 old = real_mount(old_path->mnt);
2794 p = real_mount(new_path->mnt);
2795 parent = old->mnt_parent;
2796 attached = mnt_has_parent(old);
2797 old_mp = old->mnt_mp;
2801 /* The mountpoint must be in our namespace. */
2805 /* The thing moved must be mounted... */
2806 if (!is_mounted(&old->mnt))
2809 /* ... and either ours or the root of anon namespace */
2810 if (!(attached ? check_mnt(old) : is_anon_ns(ns)))
2813 if (old->mnt.mnt_flags & MNT_LOCKED)
2816 if (old_path->dentry != old_path->mnt->mnt_root)
2819 if (d_is_dir(new_path->dentry) !=
2820 d_is_dir(old_path->dentry))
2823 * Don't move a mount residing in a shared parent.
2825 if (attached && IS_MNT_SHARED(parent))
2828 * Don't move a mount tree containing unbindable mounts to a destination
2829 * mount which is shared.
2831 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
2834 if (!check_for_nsfs_mounts(old))
2836 for (; mnt_has_parent(p); p = p->mnt_parent)
2840 err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp,
2845 /* if the mount is moved, it should no longer be expire
2847 list_del_init(&old->mnt_expire);
2849 put_mountpoint(old_mp);
2854 mntput_no_expire(parent);
2861 static int do_move_mount_old(struct path *path, const char *old_name)
2863 struct path old_path;
2866 if (!old_name || !*old_name)
2869 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
2873 err = do_move_mount(&old_path, path);
2874 path_put(&old_path);
2879 * add a mount into a namespace's mount tree
2881 static int do_add_mount(struct mount *newmnt, struct mountpoint *mp,
2882 struct path *path, int mnt_flags)
2884 struct mount *parent = real_mount(path->mnt);
2886 mnt_flags &= ~MNT_INTERNAL_FLAGS;
2888 if (unlikely(!check_mnt(parent))) {
2889 /* that's acceptable only for automounts done in private ns */
2890 if (!(mnt_flags & MNT_SHRINKABLE))
2892 /* ... and for those we'd better have mountpoint still alive */
2893 if (!parent->mnt_ns)
2897 /* Refuse the same filesystem on the same mount point */
2898 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
2899 path->mnt->mnt_root == path->dentry)
2902 if (d_is_symlink(newmnt->mnt.mnt_root))
2905 newmnt->mnt.mnt_flags = mnt_flags;
2906 return graft_tree(newmnt, parent, mp);
2909 static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags);
2912 * Create a new mount using a superblock configuration and request it
2913 * be added to the namespace tree.
2915 static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
2916 unsigned int mnt_flags)
2918 struct vfsmount *mnt;
2919 struct mountpoint *mp;
2920 struct super_block *sb = fc->root->d_sb;
2923 error = security_sb_kern_mount(sb);
2924 if (!error && mount_too_revealing(sb, &mnt_flags))
2927 if (unlikely(error)) {
2932 up_write(&sb->s_umount);
2934 mnt = vfs_create_mount(fc);
2936 return PTR_ERR(mnt);
2938 mnt_warn_timestamp_expiry(mountpoint, mnt);
2940 mp = lock_mount(mountpoint);
2945 error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags);
2953 * create a new mount for userspace and request it to be added into the
2956 static int do_new_mount(struct path *path, const char *fstype, int sb_flags,
2957 int mnt_flags, const char *name, void *data)
2959 struct file_system_type *type;
2960 struct fs_context *fc;
2961 const char *subtype = NULL;
2967 type = get_fs_type(fstype);
2971 if (type->fs_flags & FS_HAS_SUBTYPE) {
2972 subtype = strchr(fstype, '.');
2976 put_filesystem(type);
2982 fc = fs_context_for_mount(type, sb_flags);
2983 put_filesystem(type);
2988 err = vfs_parse_fs_string(fc, "subtype",
2989 subtype, strlen(subtype));
2991 err = vfs_parse_fs_string(fc, "source", name, strlen(name));
2993 err = parse_monolithic_mount_data(fc, data);
2994 if (!err && !mount_capable(fc))
2997 err = vfs_get_tree(fc);
2999 err = do_new_mount_fc(fc, path, mnt_flags);
3005 int finish_automount(struct vfsmount *m, struct path *path)
3007 struct dentry *dentry = path->dentry;
3008 struct mountpoint *mp;
3017 mnt = real_mount(m);
3018 /* The new mount record should have at least 2 refs to prevent it being
3019 * expired before we get a chance to add it
3021 BUG_ON(mnt_get_count(mnt) < 2);
3023 if (m->mnt_sb == path->mnt->mnt_sb &&
3024 m->mnt_root == dentry) {
3030 * we don't want to use lock_mount() - in this case finding something
3031 * that overmounts our mountpoint to be means "quitely drop what we've
3032 * got", not "try to mount it on top".
3034 inode_lock(dentry->d_inode);
3036 if (unlikely(cant_mount(dentry))) {
3038 goto discard_locked;
3041 if (unlikely(__lookup_mnt(path->mnt, dentry))) {
3044 goto discard_locked;
3047 mp = get_mountpoint(dentry);
3050 goto discard_locked;
3053 err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
3062 inode_unlock(dentry->d_inode);
3064 /* remove m from any expiration list it may be on */
3065 if (!list_empty(&mnt->mnt_expire)) {
3067 list_del_init(&mnt->mnt_expire);
3076 * mnt_set_expiry - Put a mount on an expiration list
3077 * @mnt: The mount to list.
3078 * @expiry_list: The list to add the mount to.
3080 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
3084 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
3088 EXPORT_SYMBOL(mnt_set_expiry);
3091 * process a list of expirable mountpoints with the intent of discarding any
3092 * mountpoints that aren't in use and haven't been touched since last we came
3095 void mark_mounts_for_expiry(struct list_head *mounts)
3097 struct mount *mnt, *next;
3098 LIST_HEAD(graveyard);
3100 if (list_empty(mounts))
3106 /* extract from the expiration list every vfsmount that matches the
3107 * following criteria:
3108 * - only referenced by its parent vfsmount
3109 * - still marked for expiry (marked on the last call here; marks are
3110 * cleared by mntput())
3112 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
3113 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
3114 propagate_mount_busy(mnt, 1))
3116 list_move(&mnt->mnt_expire, &graveyard);
3118 while (!list_empty(&graveyard)) {
3119 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
3120 touch_mnt_namespace(mnt->mnt_ns);
3121 umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC);
3123 unlock_mount_hash();
3127 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
3130 * Ripoff of 'select_parent()'
3132 * search the list of submounts for a given mountpoint, and move any
3133 * shrinkable submounts to the 'graveyard' list.
3135 static int select_submounts(struct mount *parent, struct list_head *graveyard)
3137 struct mount *this_parent = parent;
3138 struct list_head *next;
3142 next = this_parent->mnt_mounts.next;
3144 while (next != &this_parent->mnt_mounts) {
3145 struct list_head *tmp = next;
3146 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
3149 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
3152 * Descend a level if the d_mounts list is non-empty.
3154 if (!list_empty(&mnt->mnt_mounts)) {
3159 if (!propagate_mount_busy(mnt, 1)) {
3160 list_move_tail(&mnt->mnt_expire, graveyard);
3165 * All done at this level ... ascend and resume the search
3167 if (this_parent != parent) {
3168 next = this_parent->mnt_child.next;
3169 this_parent = this_parent->mnt_parent;
3176 * process a list of expirable mountpoints with the intent of discarding any
3177 * submounts of a specific parent mountpoint
3179 * mount_lock must be held for write
3181 static void shrink_submounts(struct mount *mnt)
3183 LIST_HEAD(graveyard);
3186 /* extract submounts of 'mountpoint' from the expiration list */
3187 while (select_submounts(mnt, &graveyard)) {
3188 while (!list_empty(&graveyard)) {
3189 m = list_first_entry(&graveyard, struct mount,
3191 touch_mnt_namespace(m->mnt_ns);
3192 umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC);
3197 static void *copy_mount_options(const void __user * data)
3200 unsigned left, offset;
3205 copy = kmalloc(PAGE_SIZE, GFP_KERNEL);
3207 return ERR_PTR(-ENOMEM);
3209 left = copy_from_user(copy, data, PAGE_SIZE);
3212 * Not all architectures have an exact copy_from_user(). Resort to
3215 offset = PAGE_SIZE - left;
3218 if (get_user(c, (const char __user *)data + offset))
3225 if (left == PAGE_SIZE) {
3227 return ERR_PTR(-EFAULT);
3233 static char *copy_mount_string(const void __user *data)
3235 return data ? strndup_user(data, PATH_MAX) : NULL;
3239 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
3240 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
3242 * data is a (void *) that can point to any structure up to
3243 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
3244 * information (or be NULL).
3246 * Pre-0.97 versions of mount() didn't have a flags word.
3247 * When the flags word was introduced its top half was required
3248 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
3249 * Therefore, if this magic number is present, it carries no information
3250 * and must be discarded.
3252 int path_mount(const char *dev_name, struct path *path,
3253 const char *type_page, unsigned long flags, void *data_page)
3255 unsigned int mnt_flags = 0, sb_flags;
3259 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
3260 flags &= ~MS_MGC_MSK;
3262 /* Basic sanity checks */
3264 ((char *)data_page)[PAGE_SIZE - 1] = 0;
3266 if (flags & MS_NOUSER)
3269 ret = security_sb_mount(dev_name, path, type_page, flags, data_page);
3274 if (flags & SB_MANDLOCK)
3277 /* Default to relatime unless overriden */
3278 if (!(flags & MS_NOATIME))
3279 mnt_flags |= MNT_RELATIME;
3281 /* Separate the per-mountpoint flags */
3282 if (flags & MS_NOSUID)
3283 mnt_flags |= MNT_NOSUID;
3284 if (flags & MS_NODEV)
3285 mnt_flags |= MNT_NODEV;
3286 if (flags & MS_NOEXEC)
3287 mnt_flags |= MNT_NOEXEC;
3288 if (flags & MS_NOATIME)
3289 mnt_flags |= MNT_NOATIME;
3290 if (flags & MS_NODIRATIME)
3291 mnt_flags |= MNT_NODIRATIME;
3292 if (flags & MS_STRICTATIME)
3293 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
3294 if (flags & MS_RDONLY)
3295 mnt_flags |= MNT_READONLY;
3296 if (flags & MS_NOSYMFOLLOW)
3297 mnt_flags |= MNT_NOSYMFOLLOW;
3299 /* The default atime for remount is preservation */
3300 if ((flags & MS_REMOUNT) &&
3301 ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME |
3302 MS_STRICTATIME)) == 0)) {
3303 mnt_flags &= ~MNT_ATIME_MASK;
3304 mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK;
3307 sb_flags = flags & (SB_RDONLY |
3316 if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND))
3317 return do_reconfigure_mnt(path, mnt_flags);
3318 if (flags & MS_REMOUNT)
3319 return do_remount(path, flags, sb_flags, mnt_flags, data_page);
3320 if (flags & MS_BIND)
3321 return do_loopback(path, dev_name, flags & MS_REC);
3322 if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
3323 return do_change_type(path, flags);
3324 if (flags & MS_MOVE)
3325 return do_move_mount_old(path, dev_name);
3327 return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name,
3331 long do_mount(const char *dev_name, const char __user *dir_name,
3332 const char *type_page, unsigned long flags, void *data_page)
3337 ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path);
3340 ret = path_mount(dev_name, &path, type_page, flags, data_page);
3345 static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns)
3347 return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES);
3350 static void dec_mnt_namespaces(struct ucounts *ucounts)
3352 dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES);
3355 static void free_mnt_ns(struct mnt_namespace *ns)
3357 if (!is_anon_ns(ns))
3358 ns_free_inum(&ns->ns);
3359 dec_mnt_namespaces(ns->ucounts);
3360 put_user_ns(ns->user_ns);
3365 * Assign a sequence number so we can detect when we attempt to bind
3366 * mount a reference to an older mount namespace into the current
3367 * mount namespace, preventing reference counting loops. A 64bit
3368 * number incrementing at 10Ghz will take 12,427 years to wrap which
3369 * is effectively never, so we can ignore the possibility.
3371 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
3373 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon)
3375 struct mnt_namespace *new_ns;
3376 struct ucounts *ucounts;
3379 ucounts = inc_mnt_namespaces(user_ns);
3381 return ERR_PTR(-ENOSPC);
3383 new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL_ACCOUNT);
3385 dec_mnt_namespaces(ucounts);
3386 return ERR_PTR(-ENOMEM);
3389 ret = ns_alloc_inum(&new_ns->ns);
3392 dec_mnt_namespaces(ucounts);
3393 return ERR_PTR(ret);
3396 new_ns->ns.ops = &mntns_operations;
3398 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
3399 refcount_set(&new_ns->ns.count, 1);
3400 INIT_LIST_HEAD(&new_ns->list);
3401 init_waitqueue_head(&new_ns->poll);
3402 spin_lock_init(&new_ns->ns_lock);
3403 new_ns->user_ns = get_user_ns(user_ns);
3404 new_ns->ucounts = ucounts;
3409 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
3410 struct user_namespace *user_ns, struct fs_struct *new_fs)
3412 struct mnt_namespace *new_ns;
3413 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
3414 struct mount *p, *q;
3421 if (likely(!(flags & CLONE_NEWNS))) {
3428 new_ns = alloc_mnt_ns(user_ns, false);
3433 /* First pass: copy the tree topology */
3434 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
3435 if (user_ns != ns->user_ns)
3436 copy_flags |= CL_SHARED_TO_SLAVE;
3437 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
3440 free_mnt_ns(new_ns);
3441 return ERR_CAST(new);
3443 if (user_ns != ns->user_ns) {
3446 unlock_mount_hash();
3449 list_add_tail(&new_ns->list, &new->mnt_list);
3452 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
3453 * as belonging to new namespace. We have already acquired a private
3454 * fs_struct, so tsk->fs->lock is not needed.
3462 if (&p->mnt == new_fs->root.mnt) {
3463 new_fs->root.mnt = mntget(&q->mnt);
3466 if (&p->mnt == new_fs->pwd.mnt) {
3467 new_fs->pwd.mnt = mntget(&q->mnt);
3471 p = next_mnt(p, old);
3472 q = next_mnt(q, new);
3475 while (p->mnt.mnt_root != q->mnt.mnt_root)
3476 p = next_mnt(p, old);
3488 struct dentry *mount_subtree(struct vfsmount *m, const char *name)
3490 struct mount *mnt = real_mount(m);
3491 struct mnt_namespace *ns;
3492 struct super_block *s;
3496 ns = alloc_mnt_ns(&init_user_ns, true);
3499 return ERR_CAST(ns);
3504 list_add(&mnt->mnt_list, &ns->list);
3506 err = vfs_path_lookup(m->mnt_root, m,
3507 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
3512 return ERR_PTR(err);
3514 /* trade a vfsmount reference for active sb one */
3515 s = path.mnt->mnt_sb;
3516 atomic_inc(&s->s_active);
3518 /* lock the sucker */
3519 down_write(&s->s_umount);
3520 /* ... and return the root of (sub)tree on it */
3523 EXPORT_SYMBOL(mount_subtree);
3525 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
3526 char __user *, type, unsigned long, flags, void __user *, data)
3533 kernel_type = copy_mount_string(type);
3534 ret = PTR_ERR(kernel_type);
3535 if (IS_ERR(kernel_type))
3538 kernel_dev = copy_mount_string(dev_name);
3539 ret = PTR_ERR(kernel_dev);
3540 if (IS_ERR(kernel_dev))
3543 options = copy_mount_options(data);
3544 ret = PTR_ERR(options);
3545 if (IS_ERR(options))
3548 ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options);
3559 #define FSMOUNT_VALID_FLAGS \
3560 (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \
3561 MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \
3562 MOUNT_ATTR_NOSYMFOLLOW)
3564 #define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP)
3566 #define MOUNT_SETATTR_PROPAGATION_FLAGS \
3567 (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED)
3569 static unsigned int attr_flags_to_mnt_flags(u64 attr_flags)
3571 unsigned int mnt_flags = 0;
3573 if (attr_flags & MOUNT_ATTR_RDONLY)
3574 mnt_flags |= MNT_READONLY;
3575 if (attr_flags & MOUNT_ATTR_NOSUID)
3576 mnt_flags |= MNT_NOSUID;
3577 if (attr_flags & MOUNT_ATTR_NODEV)
3578 mnt_flags |= MNT_NODEV;
3579 if (attr_flags & MOUNT_ATTR_NOEXEC)
3580 mnt_flags |= MNT_NOEXEC;
3581 if (attr_flags & MOUNT_ATTR_NODIRATIME)
3582 mnt_flags |= MNT_NODIRATIME;
3583 if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW)
3584 mnt_flags |= MNT_NOSYMFOLLOW;
3590 * Create a kernel mount representation for a new, prepared superblock
3591 * (specified by fs_fd) and attach to an open_tree-like file descriptor.
3593 SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
3594 unsigned int, attr_flags)
3596 struct mnt_namespace *ns;
3597 struct fs_context *fc;
3599 struct path newmount;
3602 unsigned int mnt_flags = 0;
3608 if ((flags & ~(FSMOUNT_CLOEXEC)) != 0)
3611 if (attr_flags & ~FSMOUNT_VALID_FLAGS)
3614 mnt_flags = attr_flags_to_mnt_flags(attr_flags);
3616 switch (attr_flags & MOUNT_ATTR__ATIME) {
3617 case MOUNT_ATTR_STRICTATIME:
3619 case MOUNT_ATTR_NOATIME:
3620 mnt_flags |= MNT_NOATIME;
3622 case MOUNT_ATTR_RELATIME:
3623 mnt_flags |= MNT_RELATIME;
3634 if (f.file->f_op != &fscontext_fops)
3637 fc = f.file->private_data;
3639 ret = mutex_lock_interruptible(&fc->uapi_mutex);
3643 /* There must be a valid superblock or we can't mount it */
3649 if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
3650 pr_warn("VFS: Mount too revealing\n");
3655 if (fc->phase != FS_CONTEXT_AWAITING_MOUNT)
3658 if (fc->sb_flags & SB_MANDLOCK)
3661 newmount.mnt = vfs_create_mount(fc);
3662 if (IS_ERR(newmount.mnt)) {
3663 ret = PTR_ERR(newmount.mnt);
3666 newmount.dentry = dget(fc->root);
3667 newmount.mnt->mnt_flags = mnt_flags;
3669 /* We've done the mount bit - now move the file context into more or
3670 * less the same state as if we'd done an fspick(). We don't want to
3671 * do any memory allocation or anything like that at this point as we
3672 * don't want to have to handle any errors incurred.
3674 vfs_clean_context(fc);
3676 ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true);
3681 mnt = real_mount(newmount.mnt);
3685 list_add(&mnt->mnt_list, &ns->list);
3686 mntget(newmount.mnt);
3688 /* Attach to an apparent O_PATH fd with a note that we need to unmount
3689 * it, not just simply put it.
3691 file = dentry_open(&newmount, O_PATH, fc->cred);
3693 dissolve_on_fput(newmount.mnt);
3694 ret = PTR_ERR(file);
3697 file->f_mode |= FMODE_NEED_UNMOUNT;
3699 ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0);
3701 fd_install(ret, file);
3706 path_put(&newmount);
3708 mutex_unlock(&fc->uapi_mutex);
3715 * Move a mount from one place to another. In combination with
3716 * fsopen()/fsmount() this is used to install a new mount and in combination
3717 * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy
3720 * Note the flags value is a combination of MOVE_MOUNT_* flags.
3722 SYSCALL_DEFINE5(move_mount,
3723 int, from_dfd, const char __user *, from_pathname,
3724 int, to_dfd, const char __user *, to_pathname,
3725 unsigned int, flags)
3727 struct path from_path, to_path;
3728 unsigned int lflags;
3734 if (flags & ~MOVE_MOUNT__MASK)
3737 /* If someone gives a pathname, they aren't permitted to move
3738 * from an fd that requires unmount as we can't get at the flag
3739 * to clear it afterwards.
3742 if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3743 if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3744 if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3746 ret = user_path_at(from_dfd, from_pathname, lflags, &from_path);
3751 if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW;
3752 if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT;
3753 if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY;
3755 ret = user_path_at(to_dfd, to_pathname, lflags, &to_path);
3759 ret = security_move_mount(&from_path, &to_path);
3763 if (flags & MOVE_MOUNT_SET_GROUP)
3764 ret = do_set_group(&from_path, &to_path);
3766 ret = do_move_mount(&from_path, &to_path);
3771 path_put(&from_path);
3776 * Return true if path is reachable from root
3778 * namespace_sem or mount_lock is held
3780 bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
3781 const struct path *root)
3783 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
3784 dentry = mnt->mnt_mountpoint;
3785 mnt = mnt->mnt_parent;
3787 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
3790 bool path_is_under(const struct path *path1, const struct path *path2)
3793 read_seqlock_excl(&mount_lock);
3794 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
3795 read_sequnlock_excl(&mount_lock);
3798 EXPORT_SYMBOL(path_is_under);
3801 * pivot_root Semantics:
3802 * Moves the root file system of the current process to the directory put_old,
3803 * makes new_root as the new root file system of the current process, and sets
3804 * root/cwd of all processes which had them on the current root to new_root.
3807 * The new_root and put_old must be directories, and must not be on the
3808 * same file system as the current process root. The put_old must be
3809 * underneath new_root, i.e. adding a non-zero number of /.. to the string
3810 * pointed to by put_old must yield the same directory as new_root. No other
3811 * file system may be mounted on put_old. After all, new_root is a mountpoint.
3813 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
3814 * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives
3815 * in this situation.
3818 * - we don't move root/cwd if they are not at the root (reason: if something
3819 * cared enough to change them, it's probably wrong to force them elsewhere)
3820 * - it's okay to pick a root that isn't the root of a file system, e.g.
3821 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
3822 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
3825 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
3826 const char __user *, put_old)
3828 struct path new, old, root;
3829 struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent;
3830 struct mountpoint *old_mp, *root_mp;
3836 error = user_path_at(AT_FDCWD, new_root,
3837 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new);
3841 error = user_path_at(AT_FDCWD, put_old,
3842 LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old);
3846 error = security_sb_pivotroot(&old, &new);
3850 get_fs_root(current->fs, &root);
3851 old_mp = lock_mount(&old);
3852 error = PTR_ERR(old_mp);
3857 new_mnt = real_mount(new.mnt);
3858 root_mnt = real_mount(root.mnt);
3859 old_mnt = real_mount(old.mnt);
3860 ex_parent = new_mnt->mnt_parent;
3861 root_parent = root_mnt->mnt_parent;
3862 if (IS_MNT_SHARED(old_mnt) ||
3863 IS_MNT_SHARED(ex_parent) ||
3864 IS_MNT_SHARED(root_parent))
3866 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
3868 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
3871 if (d_unlinked(new.dentry))
3874 if (new_mnt == root_mnt || old_mnt == root_mnt)
3875 goto out4; /* loop, on the same file system */
3877 if (root.mnt->mnt_root != root.dentry)
3878 goto out4; /* not a mountpoint */
3879 if (!mnt_has_parent(root_mnt))
3880 goto out4; /* not attached */
3881 if (new.mnt->mnt_root != new.dentry)
3882 goto out4; /* not a mountpoint */
3883 if (!mnt_has_parent(new_mnt))
3884 goto out4; /* not attached */
3885 /* make sure we can reach put_old from new_root */
3886 if (!is_path_reachable(old_mnt, old.dentry, &new))
3888 /* make certain new is below the root */
3889 if (!is_path_reachable(new_mnt, new.dentry, &root))
3892 umount_mnt(new_mnt);
3893 root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */
3894 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
3895 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
3896 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
3898 /* mount old root on put_old */
3899 attach_mnt(root_mnt, old_mnt, old_mp);
3900 /* mount new_root on / */
3901 attach_mnt(new_mnt, root_parent, root_mp);
3902 mnt_add_count(root_parent, -1);
3903 touch_mnt_namespace(current->nsproxy->mnt_ns);
3904 /* A moved mount should not expire automatically */
3905 list_del_init(&new_mnt->mnt_expire);
3906 put_mountpoint(root_mp);
3907 unlock_mount_hash();
3908 chroot_fs_refs(&root, &new);
3911 unlock_mount(old_mp);
3913 mntput_no_expire(ex_parent);
3924 static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt)
3926 unsigned int flags = mnt->mnt.mnt_flags;
3928 /* flags to clear */
3929 flags &= ~kattr->attr_clr;
3930 /* flags to raise */
3931 flags |= kattr->attr_set;
3936 static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
3938 struct vfsmount *m = &mnt->mnt;
3939 struct user_namespace *fs_userns = m->mnt_sb->s_user_ns;
3941 if (!kattr->mnt_userns)
3945 * Creating an idmapped mount with the filesystem wide idmapping
3946 * doesn't make sense so block that. We don't allow mushy semantics.
3948 if (kattr->mnt_userns == fs_userns)
3952 * Once a mount has been idmapped we don't allow it to change its
3953 * mapping. It makes things simpler and callers can just create
3954 * another bind-mount they can idmap if they want to.
3956 if (is_idmapped_mnt(m))
3959 /* The underlying filesystem doesn't support idmapped mounts yet. */
3960 if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP))
3963 /* We're not controlling the superblock. */
3964 if (!ns_capable(fs_userns, CAP_SYS_ADMIN))
3967 /* Mount has already been visible in the filesystem hierarchy. */
3968 if (!is_anon_ns(mnt->mnt_ns))
3974 static struct mount *mount_setattr_prepare(struct mount_kattr *kattr,
3975 struct mount *mnt, int *err)
3977 struct mount *m = mnt, *last = NULL;
3979 if (!is_mounted(&m->mnt)) {
3984 if (!(mnt_has_parent(m) ? check_mnt(m) : is_anon_ns(m->mnt_ns))) {
3992 flags = recalc_flags(kattr, m);
3993 if (!can_change_locked_flags(m, flags)) {
3998 *err = can_idmap_mount(kattr, m);
4004 if ((kattr->attr_set & MNT_READONLY) &&
4005 !(m->mnt.mnt_flags & MNT_READONLY)) {
4006 *err = mnt_hold_writers(m);
4010 } while (kattr->recurse && (m = next_mnt(m, mnt)));
4016 static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt)
4018 struct user_namespace *mnt_userns, *old_mnt_userns;
4020 if (!kattr->mnt_userns)
4024 * We're the only ones able to change the mount's idmapping. So
4025 * mnt->mnt.mnt_userns is stable and we can retrieve it directly.
4027 old_mnt_userns = mnt->mnt.mnt_userns;
4029 mnt_userns = get_user_ns(kattr->mnt_userns);
4030 /* Pairs with smp_load_acquire() in mnt_user_ns(). */
4031 smp_store_release(&mnt->mnt.mnt_userns, mnt_userns);
4034 * If this is an idmapped filesystem drop the reference we've taken
4035 * in vfs_create_mount() before.
4037 if (!initial_idmapping(old_mnt_userns))
4038 put_user_ns(old_mnt_userns);
4041 static void mount_setattr_commit(struct mount_kattr *kattr,
4042 struct mount *mnt, struct mount *last,
4045 struct mount *m = mnt;
4051 do_idmap_mount(kattr, m);
4052 flags = recalc_flags(kattr, m);
4053 WRITE_ONCE(m->mnt.mnt_flags, flags);
4057 * We either set MNT_READONLY above so make it visible
4058 * before ~MNT_WRITE_HOLD or we failed to recursively
4059 * apply mount options.
4061 if ((kattr->attr_set & MNT_READONLY) &&
4062 (m->mnt.mnt_flags & MNT_WRITE_HOLD))
4063 mnt_unhold_writers(m);
4065 if (!err && kattr->propagation)
4066 change_mnt_propagation(m, kattr->propagation);
4069 * On failure, only cleanup until we found the first mount
4070 * we failed to handle.
4072 if (err && m == last)
4074 } while (kattr->recurse && (m = next_mnt(m, mnt)));
4077 touch_mnt_namespace(mnt->mnt_ns);
4080 static int do_mount_setattr(struct path *path, struct mount_kattr *kattr)
4082 struct mount *mnt = real_mount(path->mnt), *last = NULL;
4085 if (path->dentry != mnt->mnt.mnt_root)
4088 if (kattr->propagation) {
4090 * Only take namespace_lock() if we're actually changing
4094 if (kattr->propagation == MS_SHARED) {
4095 err = invent_group_ids(mnt, kattr->recurse);
4106 * Get the mount tree in a shape where we can change mount
4107 * properties without failure.
4109 last = mount_setattr_prepare(kattr, mnt, &err);
4110 if (last) /* Commit all changes or revert to the old state. */
4111 mount_setattr_commit(kattr, mnt, last, err);
4113 unlock_mount_hash();
4115 if (kattr->propagation) {
4118 cleanup_group_ids(mnt, NULL);
4124 static int build_mount_idmapped(const struct mount_attr *attr, size_t usize,
4125 struct mount_kattr *kattr, unsigned int flags)
4128 struct ns_common *ns;
4129 struct user_namespace *mnt_userns;
4132 if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP))
4136 * We currently do not support clearing an idmapped mount. If this ever
4137 * is a use-case we can revisit this but for now let's keep it simple
4140 if (attr->attr_clr & MOUNT_ATTR_IDMAP)
4143 if (attr->userns_fd > INT_MAX)
4146 file = fget(attr->userns_fd);
4150 if (!proc_ns_file(file)) {
4155 ns = get_proc_ns(file_inode(file));
4156 if (ns->ops->type != CLONE_NEWUSER) {
4162 * The initial idmapping cannot be used to create an idmapped
4163 * mount. We use the initial idmapping as an indicator of a mount
4164 * that is not idmapped. It can simply be passed into helpers that
4165 * are aware of idmapped mounts as a convenient shortcut. A user
4166 * can just create a dedicated identity mapping to achieve the same
4169 mnt_userns = container_of(ns, struct user_namespace, ns);
4170 if (initial_idmapping(mnt_userns)) {
4175 /* We're not controlling the target namespace. */
4176 if (!ns_capable(mnt_userns, CAP_SYS_ADMIN)) {
4181 kattr->mnt_userns = get_user_ns(mnt_userns);
4188 static int build_mount_kattr(const struct mount_attr *attr, size_t usize,
4189 struct mount_kattr *kattr, unsigned int flags)
4191 unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW;
4193 if (flags & AT_NO_AUTOMOUNT)
4194 lookup_flags &= ~LOOKUP_AUTOMOUNT;
4195 if (flags & AT_SYMLINK_NOFOLLOW)
4196 lookup_flags &= ~LOOKUP_FOLLOW;
4197 if (flags & AT_EMPTY_PATH)
4198 lookup_flags |= LOOKUP_EMPTY;
4200 *kattr = (struct mount_kattr) {
4201 .lookup_flags = lookup_flags,
4202 .recurse = !!(flags & AT_RECURSIVE),
4205 if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS)
4207 if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1)
4209 kattr->propagation = attr->propagation;
4211 if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS)
4214 kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set);
4215 kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr);
4218 * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap,
4219 * users wanting to transition to a different atime setting cannot
4220 * simply specify the atime setting in @attr_set, but must also
4221 * specify MOUNT_ATTR__ATIME in the @attr_clr field.
4222 * So ensure that MOUNT_ATTR__ATIME can't be partially set in
4223 * @attr_clr and that @attr_set can't have any atime bits set if
4224 * MOUNT_ATTR__ATIME isn't set in @attr_clr.
4226 if (attr->attr_clr & MOUNT_ATTR__ATIME) {
4227 if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME)
4231 * Clear all previous time settings as they are mutually
4234 kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME;
4235 switch (attr->attr_set & MOUNT_ATTR__ATIME) {
4236 case MOUNT_ATTR_RELATIME:
4237 kattr->attr_set |= MNT_RELATIME;
4239 case MOUNT_ATTR_NOATIME:
4240 kattr->attr_set |= MNT_NOATIME;
4242 case MOUNT_ATTR_STRICTATIME:
4248 if (attr->attr_set & MOUNT_ATTR__ATIME)
4252 return build_mount_idmapped(attr, usize, kattr, flags);
4255 static void finish_mount_kattr(struct mount_kattr *kattr)
4257 put_user_ns(kattr->mnt_userns);
4258 kattr->mnt_userns = NULL;
4261 SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path,
4262 unsigned int, flags, struct mount_attr __user *, uattr,
4267 struct mount_attr attr;
4268 struct mount_kattr kattr;
4270 BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0);
4272 if (flags & ~(AT_EMPTY_PATH |
4274 AT_SYMLINK_NOFOLLOW |
4278 if (unlikely(usize > PAGE_SIZE))
4280 if (unlikely(usize < MOUNT_ATTR_SIZE_VER0))
4286 err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize);
4290 /* Don't bother walking through the mounts if this is a nop. */
4291 if (attr.attr_set == 0 &&
4292 attr.attr_clr == 0 &&
4293 attr.propagation == 0)
4296 err = build_mount_kattr(&attr, usize, &kattr, flags);
4300 err = user_path_at(dfd, path, kattr.lookup_flags, &target);
4302 err = do_mount_setattr(&target, &kattr);
4305 finish_mount_kattr(&kattr);
4309 static void __init init_mount_tree(void)
4311 struct vfsmount *mnt;
4313 struct mnt_namespace *ns;
4316 mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL);
4318 panic("Can't create rootfs");
4320 ns = alloc_mnt_ns(&init_user_ns, false);
4322 panic("Can't allocate initial namespace");
4323 m = real_mount(mnt);
4327 list_add(&m->mnt_list, &ns->list);
4328 init_task.nsproxy->mnt_ns = ns;
4332 root.dentry = mnt->mnt_root;
4333 mnt->mnt_flags |= MNT_LOCKED;
4335 set_fs_pwd(current->fs, &root);
4336 set_fs_root(current->fs, &root);
4339 void __init mnt_init(void)
4343 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
4344 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);
4346 mount_hashtable = alloc_large_system_hash("Mount-cache",
4347 sizeof(struct hlist_head),
4350 &m_hash_shift, &m_hash_mask, 0, 0);
4351 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
4352 sizeof(struct hlist_head),
4355 &mp_hash_shift, &mp_hash_mask, 0, 0);
4357 if (!mount_hashtable || !mountpoint_hashtable)
4358 panic("Failed to allocate mount hash table\n");
4364 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
4366 fs_kobj = kobject_create_and_add("fs", NULL);
4368 printk(KERN_WARNING "%s: kobj create error\n", __func__);
4374 void put_mnt_ns(struct mnt_namespace *ns)
4376 if (!refcount_dec_and_test(&ns->ns.count))
4378 drop_collected_mounts(&ns->root->mnt);
4382 struct vfsmount *kern_mount(struct file_system_type *type)
4384 struct vfsmount *mnt;
4385 mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL);
4388 * it is a longterm mount, don't release mnt until
4389 * we unmount before file sys is unregistered
4391 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
4395 EXPORT_SYMBOL_GPL(kern_mount);
4397 void kern_unmount(struct vfsmount *mnt)
4399 /* release long term mount so mount point can be released */
4400 if (!IS_ERR_OR_NULL(mnt)) {
4401 real_mount(mnt)->mnt_ns = NULL;
4402 synchronize_rcu(); /* yecchhh... */
4406 EXPORT_SYMBOL(kern_unmount);
4408 void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
4412 for (i = 0; i < num; i++)
4414 real_mount(mnt[i])->mnt_ns = NULL;
4415 synchronize_rcu_expedited();
4416 for (i = 0; i < num; i++)
4419 EXPORT_SYMBOL(kern_unmount_array);
4421 bool our_mnt(struct vfsmount *mnt)
4423 return check_mnt(real_mount(mnt));
4426 bool current_chrooted(void)
4428 /* Does the current process have a non-standard root */
4429 struct path ns_root;
4430 struct path fs_root;
4433 /* Find the namespace root */
4434 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
4435 ns_root.dentry = ns_root.mnt->mnt_root;
4437 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
4440 get_fs_root(current->fs, &fs_root);
4442 chrooted = !path_equal(&fs_root, &ns_root);
4450 static bool mnt_already_visible(struct mnt_namespace *ns,
4451 const struct super_block *sb,
4454 int new_flags = *new_mnt_flags;
4456 bool visible = false;
4458 down_read(&namespace_sem);
4460 list_for_each_entry(mnt, &ns->list, mnt_list) {
4461 struct mount *child;
4464 if (mnt_is_cursor(mnt))
4467 if (mnt->mnt.mnt_sb->s_type != sb->s_type)
4470 /* This mount is not fully visible if it's root directory
4471 * is not the root directory of the filesystem.
4473 if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root)
4476 /* A local view of the mount flags */
4477 mnt_flags = mnt->mnt.mnt_flags;
4479 /* Don't miss readonly hidden in the superblock flags */
4480 if (sb_rdonly(mnt->mnt.mnt_sb))
4481 mnt_flags |= MNT_LOCK_READONLY;
4483 /* Verify the mount flags are equal to or more permissive
4484 * than the proposed new mount.
4486 if ((mnt_flags & MNT_LOCK_READONLY) &&
4487 !(new_flags & MNT_READONLY))
4489 if ((mnt_flags & MNT_LOCK_ATIME) &&
4490 ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK)))
4493 /* This mount is not fully visible if there are any
4494 * locked child mounts that cover anything except for
4495 * empty directories.
4497 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
4498 struct inode *inode = child->mnt_mountpoint->d_inode;
4499 /* Only worry about locked mounts */
4500 if (!(child->mnt.mnt_flags & MNT_LOCKED))
4502 /* Is the directory permanetly empty? */
4503 if (!is_empty_dir_inode(inode))
4506 /* Preserve the locked attributes */
4507 *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \
4515 up_read(&namespace_sem);
4519 static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags)
4521 const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV;
4522 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
4523 unsigned long s_iflags;
4525 if (ns->user_ns == &init_user_ns)
4528 /* Can this filesystem be too revealing? */
4529 s_iflags = sb->s_iflags;
4530 if (!(s_iflags & SB_I_USERNS_VISIBLE))
4533 if ((s_iflags & required_iflags) != required_iflags) {
4534 WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n",
4539 return !mnt_already_visible(ns, sb, new_mnt_flags);
4542 bool mnt_may_suid(struct vfsmount *mnt)
4545 * Foreign mounts (accessed via fchdir or through /proc
4546 * symlinks) are always treated as if they are nosuid. This
4547 * prevents namespaces from trusting potentially unsafe
4548 * suid/sgid bits, file caps, or security labels that originate
4549 * in other namespaces.
4551 return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) &&
4552 current_in_userns(mnt->mnt_sb->s_user_ns);
4555 static struct ns_common *mntns_get(struct task_struct *task)
4557 struct ns_common *ns = NULL;
4558 struct nsproxy *nsproxy;
4561 nsproxy = task->nsproxy;
4563 ns = &nsproxy->mnt_ns->ns;
4564 get_mnt_ns(to_mnt_ns(ns));
4571 static void mntns_put(struct ns_common *ns)
4573 put_mnt_ns(to_mnt_ns(ns));
4576 static int mntns_install(struct nsset *nsset, struct ns_common *ns)
4578 struct nsproxy *nsproxy = nsset->nsproxy;
4579 struct fs_struct *fs = nsset->fs;
4580 struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns;
4581 struct user_namespace *user_ns = nsset->cred->user_ns;
4585 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
4586 !ns_capable(user_ns, CAP_SYS_CHROOT) ||
4587 !ns_capable(user_ns, CAP_SYS_ADMIN))
4590 if (is_anon_ns(mnt_ns))
4597 old_mnt_ns = nsproxy->mnt_ns;
4598 nsproxy->mnt_ns = mnt_ns;
4601 err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt,
4602 "/", LOOKUP_DOWN, &root);
4604 /* revert to old namespace */
4605 nsproxy->mnt_ns = old_mnt_ns;
4610 put_mnt_ns(old_mnt_ns);
4612 /* Update the pwd and root */
4613 set_fs_pwd(fs, &root);
4614 set_fs_root(fs, &root);
4620 static struct user_namespace *mntns_owner(struct ns_common *ns)
4622 return to_mnt_ns(ns)->user_ns;
4625 const struct proc_ns_operations mntns_operations = {
4627 .type = CLONE_NEWNS,
4630 .install = mntns_install,
4631 .owner = mntns_owner,