4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
11 #include <linux/syscalls.h>
12 #include <linux/export.h>
13 #include <linux/capability.h>
14 #include <linux/mnt_namespace.h>
15 #include <linux/user_namespace.h>
16 #include <linux/namei.h>
17 #include <linux/security.h>
18 #include <linux/idr.h>
19 #include <linux/acct.h> /* acct_auto_close_mnt */
20 #include <linux/init.h> /* init_rootfs */
21 #include <linux/fs_struct.h> /* get_fs_root et.al. */
22 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
23 #include <linux/uaccess.h>
24 #include <linux/proc_ns.h>
25 #include <linux/magic.h>
29 #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
30 #define HASH_SIZE (1UL << HASH_SHIFT)
33 static DEFINE_IDA(mnt_id_ida);
34 static DEFINE_IDA(mnt_group_ida);
35 static DEFINE_SPINLOCK(mnt_id_lock);
36 static int mnt_id_start = 0;
37 static int mnt_group_start = 1;
39 static struct list_head *mount_hashtable __read_mostly;
40 static struct list_head *mountpoint_hashtable __read_mostly;
41 static struct kmem_cache *mnt_cache __read_mostly;
42 static DECLARE_RWSEM(namespace_sem);
45 struct kobject *fs_kobj;
46 EXPORT_SYMBOL_GPL(fs_kobj);
49 * vfsmount lock may be taken for read to prevent changes to the
50 * vfsmount hash, ie. during mountpoint lookups or walking back
53 * It should be taken for write in all cases where the vfsmount
54 * tree or hash is modified or when a vfsmount structure is modified.
56 DEFINE_BRLOCK(vfsmount_lock);
58 static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
60 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
61 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
62 tmp = tmp + (tmp >> HASH_SHIFT);
63 return tmp & (HASH_SIZE - 1);
67 * allocation is serialized by namespace_sem, but we need the spinlock to
68 * serialize with freeing.
70 static int mnt_alloc_id(struct mount *mnt)
75 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
76 spin_lock(&mnt_id_lock);
77 res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
79 mnt_id_start = mnt->mnt_id + 1;
80 spin_unlock(&mnt_id_lock);
87 static void mnt_free_id(struct mount *mnt)
90 spin_lock(&mnt_id_lock);
91 ida_remove(&mnt_id_ida, id);
92 if (mnt_id_start > id)
94 spin_unlock(&mnt_id_lock);
98 * Allocate a new peer group ID
100 * mnt_group_ida is protected by namespace_sem
102 static int mnt_alloc_group_id(struct mount *mnt)
106 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
109 res = ida_get_new_above(&mnt_group_ida,
113 mnt_group_start = mnt->mnt_group_id + 1;
119 * Release a peer group ID
121 void mnt_release_group_id(struct mount *mnt)
123 int id = mnt->mnt_group_id;
124 ida_remove(&mnt_group_ida, id);
125 if (mnt_group_start > id)
126 mnt_group_start = id;
127 mnt->mnt_group_id = 0;
131 * vfsmount lock must be held for read
133 static inline void mnt_add_count(struct mount *mnt, int n)
136 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
145 * vfsmount lock must be held for write
147 unsigned int mnt_get_count(struct mount *mnt)
150 unsigned int count = 0;
153 for_each_possible_cpu(cpu) {
154 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
159 return mnt->mnt_count;
163 static struct mount *alloc_vfsmnt(const char *name)
165 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
169 err = mnt_alloc_id(mnt);
174 mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
175 if (!mnt->mnt_devname)
180 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
182 goto out_free_devname;
184 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
187 mnt->mnt_writers = 0;
190 INIT_LIST_HEAD(&mnt->mnt_hash);
191 INIT_LIST_HEAD(&mnt->mnt_child);
192 INIT_LIST_HEAD(&mnt->mnt_mounts);
193 INIT_LIST_HEAD(&mnt->mnt_list);
194 INIT_LIST_HEAD(&mnt->mnt_expire);
195 INIT_LIST_HEAD(&mnt->mnt_share);
196 INIT_LIST_HEAD(&mnt->mnt_slave_list);
197 INIT_LIST_HEAD(&mnt->mnt_slave);
198 #ifdef CONFIG_FSNOTIFY
199 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
206 kfree(mnt->mnt_devname);
211 kmem_cache_free(mnt_cache, mnt);
216 * Most r/o checks on a fs are for operations that take
217 * discrete amounts of time, like a write() or unlink().
218 * We must keep track of when those operations start
219 * (for permission checks) and when they end, so that
220 * we can determine when writes are able to occur to
224 * __mnt_is_readonly: check whether a mount is read-only
225 * @mnt: the mount to check for its write status
227 * This shouldn't be used directly ouside of the VFS.
228 * It does not guarantee that the filesystem will stay
229 * r/w, just that it is right *now*. This can not and
230 * should not be used in place of IS_RDONLY(inode).
231 * mnt_want/drop_write() will _keep_ the filesystem
234 int __mnt_is_readonly(struct vfsmount *mnt)
236 if (mnt->mnt_flags & MNT_READONLY)
238 if (mnt->mnt_sb->s_flags & MS_RDONLY)
242 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
244 static inline void mnt_inc_writers(struct mount *mnt)
247 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
253 static inline void mnt_dec_writers(struct mount *mnt)
256 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
262 static unsigned int mnt_get_writers(struct mount *mnt)
265 unsigned int count = 0;
268 for_each_possible_cpu(cpu) {
269 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
274 return mnt->mnt_writers;
278 static int mnt_is_readonly(struct vfsmount *mnt)
280 if (mnt->mnt_sb->s_readonly_remount)
282 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
284 return __mnt_is_readonly(mnt);
288 * Most r/o & frozen checks on a fs are for operations that take discrete
289 * amounts of time, like a write() or unlink(). We must keep track of when
290 * those operations start (for permission checks) and when they end, so that we
291 * can determine when writes are able to occur to a filesystem.
294 * __mnt_want_write - get write access to a mount without freeze protection
295 * @m: the mount on which to take a write
297 * This tells the low-level filesystem that a write is about to be performed to
298 * it, and makes sure that writes are allowed (mnt it read-write) before
299 * returning success. This operation does not protect against filesystem being
300 * frozen. When the write operation is finished, __mnt_drop_write() must be
301 * called. This is effectively a refcount.
303 int __mnt_want_write(struct vfsmount *m)
305 struct mount *mnt = real_mount(m);
309 mnt_inc_writers(mnt);
311 * The store to mnt_inc_writers must be visible before we pass
312 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
313 * incremented count after it has set MNT_WRITE_HOLD.
316 while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
319 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
320 * be set to match its requirements. So we must not load that until
321 * MNT_WRITE_HOLD is cleared.
324 if (mnt_is_readonly(m)) {
325 mnt_dec_writers(mnt);
334 * mnt_want_write - get write access to a mount
335 * @m: the mount on which to take a write
337 * This tells the low-level filesystem that a write is about to be performed to
338 * it, and makes sure that writes are allowed (mount is read-write, filesystem
339 * is not frozen) before returning success. When the write operation is
340 * finished, mnt_drop_write() must be called. This is effectively a refcount.
342 int mnt_want_write(struct vfsmount *m)
346 sb_start_write(m->mnt_sb);
347 ret = __mnt_want_write(m);
349 sb_end_write(m->mnt_sb);
352 EXPORT_SYMBOL_GPL(mnt_want_write);
355 * mnt_clone_write - get write access to a mount
356 * @mnt: the mount on which to take a write
358 * This is effectively like mnt_want_write, except
359 * it must only be used to take an extra write reference
360 * on a mountpoint that we already know has a write reference
361 * on it. This allows some optimisation.
363 * After finished, mnt_drop_write must be called as usual to
364 * drop the reference.
366 int mnt_clone_write(struct vfsmount *mnt)
368 /* superblock may be r/o */
369 if (__mnt_is_readonly(mnt))
372 mnt_inc_writers(real_mount(mnt));
376 EXPORT_SYMBOL_GPL(mnt_clone_write);
379 * __mnt_want_write_file - get write access to a file's mount
380 * @file: the file who's mount on which to take a write
382 * This is like __mnt_want_write, but it takes a file and can
383 * do some optimisations if the file is open for write already
385 int __mnt_want_write_file(struct file *file)
387 struct inode *inode = file_inode(file);
389 if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
390 return __mnt_want_write(file->f_path.mnt);
392 return mnt_clone_write(file->f_path.mnt);
396 * mnt_want_write_file - get write access to a file's mount
397 * @file: the file who's mount on which to take a write
399 * This is like mnt_want_write, but it takes a file and can
400 * do some optimisations if the file is open for write already
402 int mnt_want_write_file(struct file *file)
406 sb_start_write(file->f_path.mnt->mnt_sb);
407 ret = __mnt_want_write_file(file);
409 sb_end_write(file->f_path.mnt->mnt_sb);
412 EXPORT_SYMBOL_GPL(mnt_want_write_file);
415 * __mnt_drop_write - give up write access to a mount
416 * @mnt: the mount on which to give up write access
418 * Tells the low-level filesystem that we are done
419 * performing writes to it. Must be matched with
420 * __mnt_want_write() call above.
422 void __mnt_drop_write(struct vfsmount *mnt)
425 mnt_dec_writers(real_mount(mnt));
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 performing writes to it and
434 * also allows filesystem to be frozen again. Must be matched with
435 * mnt_want_write() call above.
437 void mnt_drop_write(struct vfsmount *mnt)
439 __mnt_drop_write(mnt);
440 sb_end_write(mnt->mnt_sb);
442 EXPORT_SYMBOL_GPL(mnt_drop_write);
444 void __mnt_drop_write_file(struct file *file)
446 __mnt_drop_write(file->f_path.mnt);
449 void mnt_drop_write_file(struct file *file)
451 mnt_drop_write(file->f_path.mnt);
453 EXPORT_SYMBOL(mnt_drop_write_file);
455 static int mnt_make_readonly(struct mount *mnt)
459 br_write_lock(&vfsmount_lock);
460 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
462 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
463 * should be visible before we do.
468 * With writers on hold, if this value is zero, then there are
469 * definitely no active writers (although held writers may subsequently
470 * increment the count, they'll have to wait, and decrement it after
471 * seeing MNT_READONLY).
473 * It is OK to have counter incremented on one CPU and decremented on
474 * another: the sum will add up correctly. The danger would be when we
475 * sum up each counter, if we read a counter before it is incremented,
476 * but then read another CPU's count which it has been subsequently
477 * decremented from -- we would see more decrements than we should.
478 * MNT_WRITE_HOLD protects against this scenario, because
479 * mnt_want_write first increments count, then smp_mb, then spins on
480 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
481 * we're counting up here.
483 if (mnt_get_writers(mnt) > 0)
486 mnt->mnt.mnt_flags |= MNT_READONLY;
488 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
489 * that become unheld will see MNT_READONLY.
492 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
493 br_write_unlock(&vfsmount_lock);
497 static void __mnt_unmake_readonly(struct mount *mnt)
499 br_write_lock(&vfsmount_lock);
500 mnt->mnt.mnt_flags &= ~MNT_READONLY;
501 br_write_unlock(&vfsmount_lock);
504 int sb_prepare_remount_readonly(struct super_block *sb)
509 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
510 if (atomic_long_read(&sb->s_remove_count))
513 br_write_lock(&vfsmount_lock);
514 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
515 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
516 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
518 if (mnt_get_writers(mnt) > 0) {
524 if (!err && atomic_long_read(&sb->s_remove_count))
528 sb->s_readonly_remount = 1;
531 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
532 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
533 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
535 br_write_unlock(&vfsmount_lock);
540 static void free_vfsmnt(struct mount *mnt)
542 kfree(mnt->mnt_devname);
545 free_percpu(mnt->mnt_pcp);
547 kmem_cache_free(mnt_cache, mnt);
551 * find the first or last mount at @dentry on vfsmount @mnt depending on
552 * @dir. If @dir is set return the first mount else return the last mount.
553 * vfsmount_lock must be held for read or write.
555 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
558 struct list_head *head = mount_hashtable + hash(mnt, dentry);
559 struct list_head *tmp = head;
560 struct mount *p, *found = NULL;
563 tmp = dir ? tmp->next : tmp->prev;
567 p = list_entry(tmp, struct mount, mnt_hash);
568 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) {
577 * lookup_mnt - Return the first child mount mounted at path
579 * "First" means first mounted chronologically. If you create the
582 * mount /dev/sda1 /mnt
583 * mount /dev/sda2 /mnt
584 * mount /dev/sda3 /mnt
586 * Then lookup_mnt() on the base /mnt dentry in the root mount will
587 * return successively the root dentry and vfsmount of /dev/sda1, then
588 * /dev/sda2, then /dev/sda3, then NULL.
590 * lookup_mnt takes a reference to the found vfsmount.
592 struct vfsmount *lookup_mnt(struct path *path)
594 struct mount *child_mnt;
596 br_read_lock(&vfsmount_lock);
597 child_mnt = __lookup_mnt(path->mnt, path->dentry, 1);
599 mnt_add_count(child_mnt, 1);
600 br_read_unlock(&vfsmount_lock);
601 return &child_mnt->mnt;
603 br_read_unlock(&vfsmount_lock);
608 static struct mountpoint *new_mountpoint(struct dentry *dentry)
610 struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry);
611 struct mountpoint *mp;
614 list_for_each_entry(mp, chain, m_hash) {
615 if (mp->m_dentry == dentry) {
616 /* might be worth a WARN_ON() */
617 if (d_unlinked(dentry))
618 return ERR_PTR(-ENOENT);
624 mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
626 return ERR_PTR(-ENOMEM);
628 ret = d_set_mounted(dentry);
634 mp->m_dentry = dentry;
636 list_add(&mp->m_hash, chain);
640 static void put_mountpoint(struct mountpoint *mp)
642 if (!--mp->m_count) {
643 struct dentry *dentry = mp->m_dentry;
644 spin_lock(&dentry->d_lock);
645 dentry->d_flags &= ~DCACHE_MOUNTED;
646 spin_unlock(&dentry->d_lock);
647 list_del(&mp->m_hash);
652 static inline int check_mnt(struct mount *mnt)
654 return mnt->mnt_ns == current->nsproxy->mnt_ns;
658 * vfsmount lock must be held for write
660 static void touch_mnt_namespace(struct mnt_namespace *ns)
664 wake_up_interruptible(&ns->poll);
669 * vfsmount lock must be held for write
671 static void __touch_mnt_namespace(struct mnt_namespace *ns)
673 if (ns && ns->event != event) {
675 wake_up_interruptible(&ns->poll);
680 * vfsmount lock must be held for write
682 static void detach_mnt(struct mount *mnt, struct path *old_path)
684 old_path->dentry = mnt->mnt_mountpoint;
685 old_path->mnt = &mnt->mnt_parent->mnt;
686 mnt->mnt_parent = mnt;
687 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
688 list_del_init(&mnt->mnt_child);
689 list_del_init(&mnt->mnt_hash);
690 put_mountpoint(mnt->mnt_mp);
695 * vfsmount lock must be held for write
697 void mnt_set_mountpoint(struct mount *mnt,
698 struct mountpoint *mp,
699 struct mount *child_mnt)
702 mnt_add_count(mnt, 1); /* essentially, that's mntget */
703 child_mnt->mnt_mountpoint = dget(mp->m_dentry);
704 child_mnt->mnt_parent = mnt;
705 child_mnt->mnt_mp = mp;
709 * vfsmount lock must be held for write
711 static void attach_mnt(struct mount *mnt,
712 struct mount *parent,
713 struct mountpoint *mp)
715 mnt_set_mountpoint(parent, mp, mnt);
716 list_add_tail(&mnt->mnt_hash, mount_hashtable +
717 hash(&parent->mnt, mp->m_dentry));
718 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
722 * vfsmount lock must be held for write
724 static void commit_tree(struct mount *mnt)
726 struct mount *parent = mnt->mnt_parent;
729 struct mnt_namespace *n = parent->mnt_ns;
731 BUG_ON(parent == mnt);
733 list_add_tail(&head, &mnt->mnt_list);
734 list_for_each_entry(m, &head, mnt_list)
737 list_splice(&head, n->list.prev);
739 list_add_tail(&mnt->mnt_hash, mount_hashtable +
740 hash(&parent->mnt, mnt->mnt_mountpoint));
741 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
742 touch_mnt_namespace(n);
745 static struct mount *next_mnt(struct mount *p, struct mount *root)
747 struct list_head *next = p->mnt_mounts.next;
748 if (next == &p->mnt_mounts) {
752 next = p->mnt_child.next;
753 if (next != &p->mnt_parent->mnt_mounts)
758 return list_entry(next, struct mount, mnt_child);
761 static struct mount *skip_mnt_tree(struct mount *p)
763 struct list_head *prev = p->mnt_mounts.prev;
764 while (prev != &p->mnt_mounts) {
765 p = list_entry(prev, struct mount, mnt_child);
766 prev = p->mnt_mounts.prev;
772 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
778 return ERR_PTR(-ENODEV);
780 mnt = alloc_vfsmnt(name);
782 return ERR_PTR(-ENOMEM);
784 if (flags & MS_KERNMOUNT)
785 mnt->mnt.mnt_flags = MNT_INTERNAL;
787 root = mount_fs(type, flags, name, data);
790 return ERR_CAST(root);
793 mnt->mnt.mnt_root = root;
794 mnt->mnt.mnt_sb = root->d_sb;
795 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
796 mnt->mnt_parent = mnt;
797 br_write_lock(&vfsmount_lock);
798 list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
799 br_write_unlock(&vfsmount_lock);
802 EXPORT_SYMBOL_GPL(vfs_kern_mount);
804 static struct mount *clone_mnt(struct mount *old, struct dentry *root,
807 struct super_block *sb = old->mnt.mnt_sb;
811 mnt = alloc_vfsmnt(old->mnt_devname);
813 return ERR_PTR(-ENOMEM);
815 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
816 mnt->mnt_group_id = 0; /* not a peer of original */
818 mnt->mnt_group_id = old->mnt_group_id;
820 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
821 err = mnt_alloc_group_id(mnt);
826 mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
827 /* Don't allow unprivileged users to change mount flags */
828 if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
829 mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
831 /* Don't allow unprivileged users to reveal what is under a mount */
832 if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
833 mnt->mnt.mnt_flags |= MNT_LOCKED;
835 atomic_inc(&sb->s_active);
836 mnt->mnt.mnt_sb = sb;
837 mnt->mnt.mnt_root = dget(root);
838 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
839 mnt->mnt_parent = mnt;
840 br_write_lock(&vfsmount_lock);
841 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
842 br_write_unlock(&vfsmount_lock);
844 if ((flag & CL_SLAVE) ||
845 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
846 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
847 mnt->mnt_master = old;
848 CLEAR_MNT_SHARED(mnt);
849 } else if (!(flag & CL_PRIVATE)) {
850 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
851 list_add(&mnt->mnt_share, &old->mnt_share);
852 if (IS_MNT_SLAVE(old))
853 list_add(&mnt->mnt_slave, &old->mnt_slave);
854 mnt->mnt_master = old->mnt_master;
856 if (flag & CL_MAKE_SHARED)
859 /* stick the duplicate mount on the same expiry list
860 * as the original if that was on one */
861 if (flag & CL_EXPIRE) {
862 if (!list_empty(&old->mnt_expire))
863 list_add(&mnt->mnt_expire, &old->mnt_expire);
873 static void mntput_no_expire(struct mount *mnt)
877 br_read_lock(&vfsmount_lock);
878 if (likely(mnt->mnt_ns)) {
879 /* shouldn't be the last one */
880 mnt_add_count(mnt, -1);
881 br_read_unlock(&vfsmount_lock);
884 br_read_unlock(&vfsmount_lock);
886 br_write_lock(&vfsmount_lock);
887 mnt_add_count(mnt, -1);
888 if (mnt_get_count(mnt)) {
889 br_write_unlock(&vfsmount_lock);
893 mnt_add_count(mnt, -1);
894 if (likely(mnt_get_count(mnt)))
896 br_write_lock(&vfsmount_lock);
898 if (unlikely(mnt->mnt_pinned)) {
899 mnt_add_count(mnt, mnt->mnt_pinned + 1);
901 br_write_unlock(&vfsmount_lock);
902 acct_auto_close_mnt(&mnt->mnt);
906 list_del(&mnt->mnt_instance);
907 br_write_unlock(&vfsmount_lock);
910 * This probably indicates that somebody messed
911 * up a mnt_want/drop_write() pair. If this
912 * happens, the filesystem was probably unable
913 * to make r/w->r/o transitions.
916 * The locking used to deal with mnt_count decrement provides barriers,
917 * so mnt_get_writers() below is safe.
919 WARN_ON(mnt_get_writers(mnt));
920 fsnotify_vfsmount_delete(&mnt->mnt);
921 dput(mnt->mnt.mnt_root);
922 deactivate_super(mnt->mnt.mnt_sb);
926 void mntput(struct vfsmount *mnt)
929 struct mount *m = real_mount(mnt);
930 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
931 if (unlikely(m->mnt_expiry_mark))
932 m->mnt_expiry_mark = 0;
936 EXPORT_SYMBOL(mntput);
938 struct vfsmount *mntget(struct vfsmount *mnt)
941 mnt_add_count(real_mount(mnt), 1);
944 EXPORT_SYMBOL(mntget);
946 void mnt_pin(struct vfsmount *mnt)
948 br_write_lock(&vfsmount_lock);
949 real_mount(mnt)->mnt_pinned++;
950 br_write_unlock(&vfsmount_lock);
952 EXPORT_SYMBOL(mnt_pin);
954 void mnt_unpin(struct vfsmount *m)
956 struct mount *mnt = real_mount(m);
957 br_write_lock(&vfsmount_lock);
958 if (mnt->mnt_pinned) {
959 mnt_add_count(mnt, 1);
962 br_write_unlock(&vfsmount_lock);
964 EXPORT_SYMBOL(mnt_unpin);
966 static inline void mangle(struct seq_file *m, const char *s)
968 seq_escape(m, s, " \t\n\\");
972 * Simple .show_options callback for filesystems which don't want to
973 * implement more complex mount option showing.
975 * See also save_mount_options().
977 int generic_show_options(struct seq_file *m, struct dentry *root)
982 options = rcu_dereference(root->d_sb->s_options);
984 if (options != NULL && options[0]) {
992 EXPORT_SYMBOL(generic_show_options);
995 * If filesystem uses generic_show_options(), this function should be
996 * called from the fill_super() callback.
998 * The .remount_fs callback usually needs to be handled in a special
999 * way, to make sure, that previous options are not overwritten if the
1002 * Also note, that if the filesystem's .remount_fs function doesn't
1003 * reset all options to their default value, but changes only newly
1004 * given options, then the displayed options will not reflect reality
1007 void save_mount_options(struct super_block *sb, char *options)
1009 BUG_ON(sb->s_options);
1010 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
1012 EXPORT_SYMBOL(save_mount_options);
1014 void replace_mount_options(struct super_block *sb, char *options)
1016 char *old = sb->s_options;
1017 rcu_assign_pointer(sb->s_options, options);
1023 EXPORT_SYMBOL(replace_mount_options);
1025 #ifdef CONFIG_PROC_FS
1026 /* iterator; we want it to have access to namespace_sem, thus here... */
1027 static void *m_start(struct seq_file *m, loff_t *pos)
1029 struct proc_mounts *p = proc_mounts(m);
1031 down_read(&namespace_sem);
1032 return seq_list_start(&p->ns->list, *pos);
1035 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1037 struct proc_mounts *p = proc_mounts(m);
1039 return seq_list_next(v, &p->ns->list, pos);
1042 static void m_stop(struct seq_file *m, void *v)
1044 up_read(&namespace_sem);
1047 static int m_show(struct seq_file *m, void *v)
1049 struct proc_mounts *p = proc_mounts(m);
1050 struct mount *r = list_entry(v, struct mount, mnt_list);
1051 return p->show(m, &r->mnt);
1054 const struct seq_operations mounts_op = {
1060 #endif /* CONFIG_PROC_FS */
1063 * may_umount_tree - check if a mount tree is busy
1064 * @mnt: root of mount tree
1066 * This is called to check if a tree of mounts has any
1067 * open files, pwds, chroots or sub mounts that are
1070 int may_umount_tree(struct vfsmount *m)
1072 struct mount *mnt = real_mount(m);
1073 int actual_refs = 0;
1074 int minimum_refs = 0;
1078 /* write lock needed for mnt_get_count */
1079 br_write_lock(&vfsmount_lock);
1080 for (p = mnt; p; p = next_mnt(p, mnt)) {
1081 actual_refs += mnt_get_count(p);
1084 br_write_unlock(&vfsmount_lock);
1086 if (actual_refs > minimum_refs)
1092 EXPORT_SYMBOL(may_umount_tree);
1095 * may_umount - check if a mount point is busy
1096 * @mnt: root of mount
1098 * This is called to check if a mount point has any
1099 * open files, pwds, chroots or sub mounts. If the
1100 * mount has sub mounts this will return busy
1101 * regardless of whether the sub mounts are busy.
1103 * Doesn't take quota and stuff into account. IOW, in some cases it will
1104 * give false negatives. The main reason why it's here is that we need
1105 * a non-destructive way to look for easily umountable filesystems.
1107 int may_umount(struct vfsmount *mnt)
1110 down_read(&namespace_sem);
1111 br_write_lock(&vfsmount_lock);
1112 if (propagate_mount_busy(real_mount(mnt), 2))
1114 br_write_unlock(&vfsmount_lock);
1115 up_read(&namespace_sem);
1119 EXPORT_SYMBOL(may_umount);
1121 static LIST_HEAD(unmounted); /* protected by namespace_sem */
1123 static void namespace_unlock(void)
1128 if (likely(list_empty(&unmounted))) {
1129 up_write(&namespace_sem);
1133 list_splice_init(&unmounted, &head);
1134 up_write(&namespace_sem);
1136 while (!list_empty(&head)) {
1137 mnt = list_first_entry(&head, struct mount, mnt_hash);
1138 list_del_init(&mnt->mnt_hash);
1139 if (mnt_has_parent(mnt)) {
1140 struct dentry *dentry;
1143 br_write_lock(&vfsmount_lock);
1144 dentry = mnt->mnt_mountpoint;
1145 m = mnt->mnt_parent;
1146 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1147 mnt->mnt_parent = mnt;
1149 br_write_unlock(&vfsmount_lock);
1157 static inline void namespace_lock(void)
1159 down_write(&namespace_sem);
1163 * vfsmount lock must be held for write
1164 * namespace_sem must be held for write
1166 void umount_tree(struct mount *mnt, int propagate)
1168 LIST_HEAD(tmp_list);
1171 for (p = mnt; p; p = next_mnt(p, mnt))
1172 list_move(&p->mnt_hash, &tmp_list);
1175 propagate_umount(&tmp_list);
1177 list_for_each_entry(p, &tmp_list, mnt_hash) {
1178 list_del_init(&p->mnt_expire);
1179 list_del_init(&p->mnt_list);
1180 __touch_mnt_namespace(p->mnt_ns);
1182 list_del_init(&p->mnt_child);
1183 if (mnt_has_parent(p)) {
1184 p->mnt_parent->mnt_ghosts++;
1185 put_mountpoint(p->mnt_mp);
1188 change_mnt_propagation(p, MS_PRIVATE);
1190 list_splice(&tmp_list, &unmounted);
1193 static void shrink_submounts(struct mount *mnt);
1195 static int do_umount(struct mount *mnt, int flags)
1197 struct super_block *sb = mnt->mnt.mnt_sb;
1200 retval = security_sb_umount(&mnt->mnt, flags);
1205 * Allow userspace to request a mountpoint be expired rather than
1206 * unmounting unconditionally. Unmount only happens if:
1207 * (1) the mark is already set (the mark is cleared by mntput())
1208 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1210 if (flags & MNT_EXPIRE) {
1211 if (&mnt->mnt == current->fs->root.mnt ||
1212 flags & (MNT_FORCE | MNT_DETACH))
1216 * probably don't strictly need the lock here if we examined
1217 * all race cases, but it's a slowpath.
1219 br_write_lock(&vfsmount_lock);
1220 if (mnt_get_count(mnt) != 2) {
1221 br_write_unlock(&vfsmount_lock);
1224 br_write_unlock(&vfsmount_lock);
1226 if (!xchg(&mnt->mnt_expiry_mark, 1))
1231 * If we may have to abort operations to get out of this
1232 * mount, and they will themselves hold resources we must
1233 * allow the fs to do things. In the Unix tradition of
1234 * 'Gee thats tricky lets do it in userspace' the umount_begin
1235 * might fail to complete on the first run through as other tasks
1236 * must return, and the like. Thats for the mount program to worry
1237 * about for the moment.
1240 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1241 sb->s_op->umount_begin(sb);
1245 * No sense to grab the lock for this test, but test itself looks
1246 * somewhat bogus. Suggestions for better replacement?
1247 * Ho-hum... In principle, we might treat that as umount + switch
1248 * to rootfs. GC would eventually take care of the old vfsmount.
1249 * Actually it makes sense, especially if rootfs would contain a
1250 * /reboot - static binary that would close all descriptors and
1251 * call reboot(9). Then init(8) could umount root and exec /reboot.
1253 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1255 * Special case for "unmounting" root ...
1256 * we just try to remount it readonly.
1258 down_write(&sb->s_umount);
1259 if (!(sb->s_flags & MS_RDONLY))
1260 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1261 up_write(&sb->s_umount);
1266 br_write_lock(&vfsmount_lock);
1269 if (!(flags & MNT_DETACH))
1270 shrink_submounts(mnt);
1273 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
1274 if (!list_empty(&mnt->mnt_list))
1275 umount_tree(mnt, 1);
1278 br_write_unlock(&vfsmount_lock);
1284 * Is the caller allowed to modify his namespace?
1286 static inline bool may_mount(void)
1288 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1292 * Now umount can handle mount points as well as block devices.
1293 * This is important for filesystems which use unnamed block devices.
1295 * We now support a flag for forced unmount like the other 'big iron'
1296 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1299 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1304 int lookup_flags = 0;
1306 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1312 if (!(flags & UMOUNT_NOFOLLOW))
1313 lookup_flags |= LOOKUP_FOLLOW;
1315 retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
1318 mnt = real_mount(path.mnt);
1320 if (path.dentry != path.mnt->mnt_root)
1322 if (!check_mnt(mnt))
1324 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1327 retval = do_umount(mnt, flags);
1329 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1331 mntput_no_expire(mnt);
1336 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1339 * The 2.0 compatible umount. No flags.
1341 SYSCALL_DEFINE1(oldumount, char __user *, name)
1343 return sys_umount(name, 0);
1348 static bool is_mnt_ns_file(struct dentry *dentry)
1350 /* Is this a proxy for a mount namespace? */
1351 struct inode *inode = dentry->d_inode;
1354 if (!proc_ns_inode(inode))
1357 ei = get_proc_ns(inode);
1358 if (ei->ns_ops != &mntns_operations)
1364 static bool mnt_ns_loop(struct dentry *dentry)
1366 /* Could bind mounting the mount namespace inode cause a
1367 * mount namespace loop?
1369 struct mnt_namespace *mnt_ns;
1370 if (!is_mnt_ns_file(dentry))
1373 mnt_ns = get_proc_ns(dentry->d_inode)->ns;
1374 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1377 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1380 struct mount *res, *p, *q, *r, *parent;
1382 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1383 return ERR_PTR(-EINVAL);
1385 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1386 return ERR_PTR(-EINVAL);
1388 res = q = clone_mnt(mnt, dentry, flag);
1392 q->mnt.mnt_flags &= ~MNT_LOCKED;
1393 q->mnt_mountpoint = mnt->mnt_mountpoint;
1396 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1398 if (!is_subdir(r->mnt_mountpoint, dentry))
1401 for (s = r; s; s = next_mnt(s, r)) {
1402 if (!(flag & CL_COPY_UNBINDABLE) &&
1403 IS_MNT_UNBINDABLE(s)) {
1404 s = skip_mnt_tree(s);
1407 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1408 is_mnt_ns_file(s->mnt.mnt_root)) {
1409 s = skip_mnt_tree(s);
1412 while (p != s->mnt_parent) {
1418 q = clone_mnt(p, p->mnt.mnt_root, flag);
1421 br_write_lock(&vfsmount_lock);
1422 list_add_tail(&q->mnt_list, &res->mnt_list);
1423 attach_mnt(q, parent, p->mnt_mp);
1424 br_write_unlock(&vfsmount_lock);
1430 br_write_lock(&vfsmount_lock);
1431 umount_tree(res, 0);
1432 br_write_unlock(&vfsmount_lock);
1437 /* Caller should check returned pointer for errors */
1439 struct vfsmount *collect_mounts(struct path *path)
1443 tree = copy_tree(real_mount(path->mnt), path->dentry,
1444 CL_COPY_ALL | CL_PRIVATE);
1447 return ERR_CAST(tree);
1451 void drop_collected_mounts(struct vfsmount *mnt)
1454 br_write_lock(&vfsmount_lock);
1455 umount_tree(real_mount(mnt), 0);
1456 br_write_unlock(&vfsmount_lock);
1460 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1461 struct vfsmount *root)
1464 int res = f(root, arg);
1467 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1468 res = f(&mnt->mnt, arg);
1475 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1479 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1480 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1481 mnt_release_group_id(p);
1485 static int invent_group_ids(struct mount *mnt, bool recurse)
1489 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1490 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1491 int err = mnt_alloc_group_id(p);
1493 cleanup_group_ids(mnt, p);
1503 * @source_mnt : mount tree to be attached
1504 * @nd : place the mount tree @source_mnt is attached
1505 * @parent_nd : if non-null, detach the source_mnt from its parent and
1506 * store the parent mount and mountpoint dentry.
1507 * (done when source_mnt is moved)
1509 * NOTE: in the table below explains the semantics when a source mount
1510 * of a given type is attached to a destination mount of a given type.
1511 * ---------------------------------------------------------------------------
1512 * | BIND MOUNT OPERATION |
1513 * |**************************************************************************
1514 * | source-->| shared | private | slave | unbindable |
1518 * |**************************************************************************
1519 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1521 * |non-shared| shared (+) | private | slave (*) | invalid |
1522 * ***************************************************************************
1523 * A bind operation clones the source mount and mounts the clone on the
1524 * destination mount.
1526 * (++) the cloned mount is propagated to all the mounts in the propagation
1527 * tree of the destination mount and the cloned mount is added to
1528 * the peer group of the source mount.
1529 * (+) the cloned mount is created under the destination mount and is marked
1530 * as shared. The cloned mount is added to the peer group of the source
1532 * (+++) the mount is propagated to all the mounts in the propagation tree
1533 * of the destination mount and the cloned mount is made slave
1534 * of the same master as that of the source mount. The cloned mount
1535 * is marked as 'shared and slave'.
1536 * (*) the cloned mount is made a slave of the same master as that of the
1539 * ---------------------------------------------------------------------------
1540 * | MOVE MOUNT OPERATION |
1541 * |**************************************************************************
1542 * | source-->| shared | private | slave | unbindable |
1546 * |**************************************************************************
1547 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1549 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1550 * ***************************************************************************
1552 * (+) the mount is moved to the destination. And is then propagated to
1553 * all the mounts in the propagation tree of the destination mount.
1554 * (+*) the mount is moved to the destination.
1555 * (+++) the mount is moved to the destination and is then propagated to
1556 * all the mounts belonging to the destination mount's propagation tree.
1557 * the mount is marked as 'shared and slave'.
1558 * (*) the mount continues to be a slave at the new location.
1560 * if the source mount is a tree, the operations explained above is
1561 * applied to each mount in the tree.
1562 * Must be called without spinlocks held, since this function can sleep
1565 static int attach_recursive_mnt(struct mount *source_mnt,
1566 struct mount *dest_mnt,
1567 struct mountpoint *dest_mp,
1568 struct path *parent_path)
1570 LIST_HEAD(tree_list);
1571 struct mount *child, *p;
1574 if (IS_MNT_SHARED(dest_mnt)) {
1575 err = invent_group_ids(source_mnt, true);
1579 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
1581 goto out_cleanup_ids;
1583 br_write_lock(&vfsmount_lock);
1585 if (IS_MNT_SHARED(dest_mnt)) {
1586 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1590 detach_mnt(source_mnt, parent_path);
1591 attach_mnt(source_mnt, dest_mnt, dest_mp);
1592 touch_mnt_namespace(source_mnt->mnt_ns);
1594 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
1595 commit_tree(source_mnt);
1598 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
1599 list_del_init(&child->mnt_hash);
1602 br_write_unlock(&vfsmount_lock);
1607 if (IS_MNT_SHARED(dest_mnt))
1608 cleanup_group_ids(source_mnt, NULL);
1613 static struct mountpoint *lock_mount(struct path *path)
1615 struct vfsmount *mnt;
1616 struct dentry *dentry = path->dentry;
1618 mutex_lock(&dentry->d_inode->i_mutex);
1619 if (unlikely(cant_mount(dentry))) {
1620 mutex_unlock(&dentry->d_inode->i_mutex);
1621 return ERR_PTR(-ENOENT);
1624 mnt = lookup_mnt(path);
1626 struct mountpoint *mp = new_mountpoint(dentry);
1629 mutex_unlock(&dentry->d_inode->i_mutex);
1635 mutex_unlock(&path->dentry->d_inode->i_mutex);
1638 dentry = path->dentry = dget(mnt->mnt_root);
1642 static void unlock_mount(struct mountpoint *where)
1644 struct dentry *dentry = where->m_dentry;
1645 put_mountpoint(where);
1647 mutex_unlock(&dentry->d_inode->i_mutex);
1650 static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
1652 if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
1655 if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
1656 S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
1659 return attach_recursive_mnt(mnt, p, mp, NULL);
1663 * Sanity check the flags to change_mnt_propagation.
1666 static int flags_to_propagation_type(int flags)
1668 int type = flags & ~(MS_REC | MS_SILENT);
1670 /* Fail if any non-propagation flags are set */
1671 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1673 /* Only one propagation flag should be set */
1674 if (!is_power_of_2(type))
1680 * recursively change the type of the mountpoint.
1682 static int do_change_type(struct path *path, int flag)
1685 struct mount *mnt = real_mount(path->mnt);
1686 int recurse = flag & MS_REC;
1690 if (path->dentry != path->mnt->mnt_root)
1693 type = flags_to_propagation_type(flag);
1698 if (type == MS_SHARED) {
1699 err = invent_group_ids(mnt, recurse);
1704 br_write_lock(&vfsmount_lock);
1705 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1706 change_mnt_propagation(m, type);
1707 br_write_unlock(&vfsmount_lock);
1714 static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
1716 struct mount *child;
1717 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
1718 if (!is_subdir(child->mnt_mountpoint, dentry))
1721 if (child->mnt.mnt_flags & MNT_LOCKED)
1728 * do loopback mount.
1730 static int do_loopback(struct path *path, const char *old_name,
1733 struct path old_path;
1734 struct mount *mnt = NULL, *old, *parent;
1735 struct mountpoint *mp;
1737 if (!old_name || !*old_name)
1739 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1744 if (mnt_ns_loop(old_path.dentry))
1747 mp = lock_mount(path);
1752 old = real_mount(old_path.mnt);
1753 parent = real_mount(path->mnt);
1756 if (IS_MNT_UNBINDABLE(old))
1759 if (!check_mnt(parent) || !check_mnt(old))
1762 if (!recurse && has_locked_children(old, old_path.dentry))
1766 mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
1768 mnt = clone_mnt(old, old_path.dentry, 0);
1775 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
1777 err = graft_tree(mnt, parent, mp);
1779 br_write_lock(&vfsmount_lock);
1780 umount_tree(mnt, 0);
1781 br_write_unlock(&vfsmount_lock);
1786 path_put(&old_path);
1790 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1793 int readonly_request = 0;
1795 if (ms_flags & MS_RDONLY)
1796 readonly_request = 1;
1797 if (readonly_request == __mnt_is_readonly(mnt))
1800 if (mnt->mnt_flags & MNT_LOCK_READONLY)
1803 if (readonly_request)
1804 error = mnt_make_readonly(real_mount(mnt));
1806 __mnt_unmake_readonly(real_mount(mnt));
1811 * change filesystem flags. dir should be a physical root of filesystem.
1812 * If you've mounted a non-root directory somewhere and want to do remount
1813 * on it - tough luck.
1815 static int do_remount(struct path *path, int flags, int mnt_flags,
1819 struct super_block *sb = path->mnt->mnt_sb;
1820 struct mount *mnt = real_mount(path->mnt);
1822 if (!check_mnt(mnt))
1825 if (path->dentry != path->mnt->mnt_root)
1828 err = security_sb_remount(sb, data);
1832 down_write(&sb->s_umount);
1833 if (flags & MS_BIND)
1834 err = change_mount_flags(path->mnt, flags);
1835 else if (!capable(CAP_SYS_ADMIN))
1838 err = do_remount_sb(sb, flags, data, 0);
1840 br_write_lock(&vfsmount_lock);
1841 mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
1842 mnt->mnt.mnt_flags = mnt_flags;
1843 touch_mnt_namespace(mnt->mnt_ns);
1844 br_write_unlock(&vfsmount_lock);
1846 up_write(&sb->s_umount);
1850 static inline int tree_contains_unbindable(struct mount *mnt)
1853 for (p = mnt; p; p = next_mnt(p, mnt)) {
1854 if (IS_MNT_UNBINDABLE(p))
1860 static int do_move_mount(struct path *path, const char *old_name)
1862 struct path old_path, parent_path;
1865 struct mountpoint *mp;
1867 if (!old_name || !*old_name)
1869 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1873 mp = lock_mount(path);
1878 old = real_mount(old_path.mnt);
1879 p = real_mount(path->mnt);
1882 if (!check_mnt(p) || !check_mnt(old))
1885 if (old->mnt.mnt_flags & MNT_LOCKED)
1889 if (old_path.dentry != old_path.mnt->mnt_root)
1892 if (!mnt_has_parent(old))
1895 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1896 S_ISDIR(old_path.dentry->d_inode->i_mode))
1899 * Don't move a mount residing in a shared parent.
1901 if (IS_MNT_SHARED(old->mnt_parent))
1904 * Don't move a mount tree containing unbindable mounts to a destination
1905 * mount which is shared.
1907 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
1910 for (; mnt_has_parent(p); p = p->mnt_parent)
1914 err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
1918 /* if the mount is moved, it should no longer be expire
1920 list_del_init(&old->mnt_expire);
1925 path_put(&parent_path);
1926 path_put(&old_path);
1930 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
1933 const char *subtype = strchr(fstype, '.');
1942 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
1944 if (!mnt->mnt_sb->s_subtype)
1950 return ERR_PTR(err);
1954 * add a mount into a namespace's mount tree
1956 static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
1958 struct mountpoint *mp;
1959 struct mount *parent;
1962 mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
1964 mp = lock_mount(path);
1968 parent = real_mount(path->mnt);
1970 if (unlikely(!check_mnt(parent))) {
1971 /* that's acceptable only for automounts done in private ns */
1972 if (!(mnt_flags & MNT_SHRINKABLE))
1974 /* ... and for those we'd better have mountpoint still alive */
1975 if (!parent->mnt_ns)
1979 /* Refuse the same filesystem on the same mount point */
1981 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
1982 path->mnt->mnt_root == path->dentry)
1986 if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
1989 newmnt->mnt.mnt_flags = mnt_flags;
1990 err = graft_tree(newmnt, parent, mp);
1998 * create a new mount for userspace and request it to be added into the
2001 static int do_new_mount(struct path *path, const char *fstype, int flags,
2002 int mnt_flags, const char *name, void *data)
2004 struct file_system_type *type;
2005 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2006 struct vfsmount *mnt;
2012 type = get_fs_type(fstype);
2016 if (user_ns != &init_user_ns) {
2017 if (!(type->fs_flags & FS_USERNS_MOUNT)) {
2018 put_filesystem(type);
2021 /* Only in special cases allow devices from mounts
2022 * created outside the initial user namespace.
2024 if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
2026 mnt_flags |= MNT_NODEV;
2030 mnt = vfs_kern_mount(type, flags, name, data);
2031 if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
2032 !mnt->mnt_sb->s_subtype)
2033 mnt = fs_set_subtype(mnt, fstype);
2035 put_filesystem(type);
2037 return PTR_ERR(mnt);
2039 err = do_add_mount(real_mount(mnt), path, mnt_flags);
2045 int finish_automount(struct vfsmount *m, struct path *path)
2047 struct mount *mnt = real_mount(m);
2049 /* The new mount record should have at least 2 refs to prevent it being
2050 * expired before we get a chance to add it
2052 BUG_ON(mnt_get_count(mnt) < 2);
2054 if (m->mnt_sb == path->mnt->mnt_sb &&
2055 m->mnt_root == path->dentry) {
2060 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2064 /* remove m from any expiration list it may be on */
2065 if (!list_empty(&mnt->mnt_expire)) {
2067 list_del_init(&mnt->mnt_expire);
2076 * mnt_set_expiry - Put a mount on an expiration list
2077 * @mnt: The mount to list.
2078 * @expiry_list: The list to add the mount to.
2080 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2084 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2088 EXPORT_SYMBOL(mnt_set_expiry);
2091 * process a list of expirable mountpoints with the intent of discarding any
2092 * mountpoints that aren't in use and haven't been touched since last we came
2095 void mark_mounts_for_expiry(struct list_head *mounts)
2097 struct mount *mnt, *next;
2098 LIST_HEAD(graveyard);
2100 if (list_empty(mounts))
2104 br_write_lock(&vfsmount_lock);
2106 /* extract from the expiration list every vfsmount that matches the
2107 * following criteria:
2108 * - only referenced by its parent vfsmount
2109 * - still marked for expiry (marked on the last call here; marks are
2110 * cleared by mntput())
2112 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2113 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2114 propagate_mount_busy(mnt, 1))
2116 list_move(&mnt->mnt_expire, &graveyard);
2118 while (!list_empty(&graveyard)) {
2119 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2120 touch_mnt_namespace(mnt->mnt_ns);
2121 umount_tree(mnt, 1);
2123 br_write_unlock(&vfsmount_lock);
2127 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2130 * Ripoff of 'select_parent()'
2132 * search the list of submounts for a given mountpoint, and move any
2133 * shrinkable submounts to the 'graveyard' list.
2135 static int select_submounts(struct mount *parent, struct list_head *graveyard)
2137 struct mount *this_parent = parent;
2138 struct list_head *next;
2142 next = this_parent->mnt_mounts.next;
2144 while (next != &this_parent->mnt_mounts) {
2145 struct list_head *tmp = next;
2146 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2149 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2152 * Descend a level if the d_mounts list is non-empty.
2154 if (!list_empty(&mnt->mnt_mounts)) {
2159 if (!propagate_mount_busy(mnt, 1)) {
2160 list_move_tail(&mnt->mnt_expire, graveyard);
2165 * All done at this level ... ascend and resume the search
2167 if (this_parent != parent) {
2168 next = this_parent->mnt_child.next;
2169 this_parent = this_parent->mnt_parent;
2176 * process a list of expirable mountpoints with the intent of discarding any
2177 * submounts of a specific parent mountpoint
2179 * vfsmount_lock must be held for write
2181 static void shrink_submounts(struct mount *mnt)
2183 LIST_HEAD(graveyard);
2186 /* extract submounts of 'mountpoint' from the expiration list */
2187 while (select_submounts(mnt, &graveyard)) {
2188 while (!list_empty(&graveyard)) {
2189 m = list_first_entry(&graveyard, struct mount,
2191 touch_mnt_namespace(m->mnt_ns);
2198 * Some copy_from_user() implementations do not return the exact number of
2199 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2200 * Note that this function differs from copy_from_user() in that it will oops
2201 * on bad values of `to', rather than returning a short copy.
2203 static long exact_copy_from_user(void *to, const void __user * from,
2207 const char __user *f = from;
2210 if (!access_ok(VERIFY_READ, from, n))
2214 if (__get_user(c, f)) {
2225 int copy_mount_options(const void __user * data, unsigned long *where)
2235 if (!(page = __get_free_page(GFP_KERNEL)))
2238 /* We only care that *some* data at the address the user
2239 * gave us is valid. Just in case, we'll zero
2240 * the remainder of the page.
2242 /* copy_from_user cannot cross TASK_SIZE ! */
2243 size = TASK_SIZE - (unsigned long)data;
2244 if (size > PAGE_SIZE)
2247 i = size - exact_copy_from_user((void *)page, data, size);
2253 memset((char *)page + i, 0, PAGE_SIZE - i);
2258 int copy_mount_string(const void __user *data, char **where)
2267 tmp = strndup_user(data, PAGE_SIZE);
2269 return PTR_ERR(tmp);
2276 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2277 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2279 * data is a (void *) that can point to any structure up to
2280 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2281 * information (or be NULL).
2283 * Pre-0.97 versions of mount() didn't have a flags word.
2284 * When the flags word was introduced its top half was required
2285 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2286 * Therefore, if this magic number is present, it carries no information
2287 * and must be discarded.
2289 long do_mount(const char *dev_name, const char *dir_name,
2290 const char *type_page, unsigned long flags, void *data_page)
2297 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2298 flags &= ~MS_MGC_MSK;
2300 /* Basic sanity checks */
2302 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2306 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2308 /* ... and get the mountpoint */
2309 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2313 retval = security_sb_mount(dev_name, &path,
2314 type_page, flags, data_page);
2315 if (!retval && !may_mount())
2320 /* Default to relatime unless overriden */
2321 if (!(flags & MS_NOATIME))
2322 mnt_flags |= MNT_RELATIME;
2324 /* Separate the per-mountpoint flags */
2325 if (flags & MS_NOSUID)
2326 mnt_flags |= MNT_NOSUID;
2327 if (flags & MS_NODEV)
2328 mnt_flags |= MNT_NODEV;
2329 if (flags & MS_NOEXEC)
2330 mnt_flags |= MNT_NOEXEC;
2331 if (flags & MS_NOATIME)
2332 mnt_flags |= MNT_NOATIME;
2333 if (flags & MS_NODIRATIME)
2334 mnt_flags |= MNT_NODIRATIME;
2335 if (flags & MS_STRICTATIME)
2336 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2337 if (flags & MS_RDONLY)
2338 mnt_flags |= MNT_READONLY;
2340 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2341 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2344 if (flags & MS_REMOUNT)
2345 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2347 else if (flags & MS_BIND)
2348 retval = do_loopback(&path, dev_name, flags & MS_REC);
2349 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2350 retval = do_change_type(&path, flags);
2351 else if (flags & MS_MOVE)
2352 retval = do_move_mount(&path, dev_name);
2354 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2355 dev_name, data_page);
2361 static void free_mnt_ns(struct mnt_namespace *ns)
2363 proc_free_inum(ns->proc_inum);
2364 put_user_ns(ns->user_ns);
2369 * Assign a sequence number so we can detect when we attempt to bind
2370 * mount a reference to an older mount namespace into the current
2371 * mount namespace, preventing reference counting loops. A 64bit
2372 * number incrementing at 10Ghz will take 12,427 years to wrap which
2373 * is effectively never, so we can ignore the possibility.
2375 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
2377 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
2379 struct mnt_namespace *new_ns;
2382 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2384 return ERR_PTR(-ENOMEM);
2385 ret = proc_alloc_inum(&new_ns->proc_inum);
2388 return ERR_PTR(ret);
2390 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
2391 atomic_set(&new_ns->count, 1);
2392 new_ns->root = NULL;
2393 INIT_LIST_HEAD(&new_ns->list);
2394 init_waitqueue_head(&new_ns->poll);
2396 new_ns->user_ns = get_user_ns(user_ns);
2401 * Allocate a new namespace structure and populate it with contents
2402 * copied from the namespace of the passed in task structure.
2404 static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
2405 struct user_namespace *user_ns, struct fs_struct *fs)
2407 struct mnt_namespace *new_ns;
2408 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2409 struct mount *p, *q;
2410 struct mount *old = mnt_ns->root;
2414 new_ns = alloc_mnt_ns(user_ns);
2419 /* First pass: copy the tree topology */
2420 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
2421 if (user_ns != mnt_ns->user_ns)
2422 copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
2423 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
2426 free_mnt_ns(new_ns);
2427 return ERR_CAST(new);
2430 list_add_tail(&new_ns->list, &new->mnt_list);
2433 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2434 * as belonging to new namespace. We have already acquired a private
2435 * fs_struct, so tsk->fs->lock is not needed.
2442 if (&p->mnt == fs->root.mnt) {
2443 fs->root.mnt = mntget(&q->mnt);
2446 if (&p->mnt == fs->pwd.mnt) {
2447 fs->pwd.mnt = mntget(&q->mnt);
2451 p = next_mnt(p, old);
2452 q = next_mnt(q, new);
2455 while (p->mnt.mnt_root != q->mnt.mnt_root)
2456 p = next_mnt(p, old);
2468 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2469 struct user_namespace *user_ns, struct fs_struct *new_fs)
2471 struct mnt_namespace *new_ns;
2476 if (!(flags & CLONE_NEWNS))
2479 new_ns = dup_mnt_ns(ns, user_ns, new_fs);
2486 * create_mnt_ns - creates a private namespace and adds a root filesystem
2487 * @mnt: pointer to the new root filesystem mountpoint
2489 static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
2491 struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
2492 if (!IS_ERR(new_ns)) {
2493 struct mount *mnt = real_mount(m);
2494 mnt->mnt_ns = new_ns;
2496 list_add(&mnt->mnt_list, &new_ns->list);
2503 struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
2505 struct mnt_namespace *ns;
2506 struct super_block *s;
2510 ns = create_mnt_ns(mnt);
2512 return ERR_CAST(ns);
2514 err = vfs_path_lookup(mnt->mnt_root, mnt,
2515 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
2520 return ERR_PTR(err);
2522 /* trade a vfsmount reference for active sb one */
2523 s = path.mnt->mnt_sb;
2524 atomic_inc(&s->s_active);
2526 /* lock the sucker */
2527 down_write(&s->s_umount);
2528 /* ... and return the root of (sub)tree on it */
2531 EXPORT_SYMBOL(mount_subtree);
2533 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2534 char __user *, type, unsigned long, flags, void __user *, data)
2538 struct filename *kernel_dir;
2540 unsigned long data_page;
2542 ret = copy_mount_string(type, &kernel_type);
2546 kernel_dir = getname(dir_name);
2547 if (IS_ERR(kernel_dir)) {
2548 ret = PTR_ERR(kernel_dir);
2552 ret = copy_mount_string(dev_name, &kernel_dev);
2556 ret = copy_mount_options(data, &data_page);
2560 ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
2561 (void *) data_page);
2563 free_page(data_page);
2567 putname(kernel_dir);
2575 * Return true if path is reachable from root
2577 * namespace_sem or vfsmount_lock is held
2579 bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
2580 const struct path *root)
2582 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
2583 dentry = mnt->mnt_mountpoint;
2584 mnt = mnt->mnt_parent;
2586 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
2589 int path_is_under(struct path *path1, struct path *path2)
2592 br_read_lock(&vfsmount_lock);
2593 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
2594 br_read_unlock(&vfsmount_lock);
2597 EXPORT_SYMBOL(path_is_under);
2600 * pivot_root Semantics:
2601 * Moves the root file system of the current process to the directory put_old,
2602 * makes new_root as the new root file system of the current process, and sets
2603 * root/cwd of all processes which had them on the current root to new_root.
2606 * The new_root and put_old must be directories, and must not be on the
2607 * same file system as the current process root. The put_old must be
2608 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2609 * pointed to by put_old must yield the same directory as new_root. No other
2610 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2612 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2613 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2614 * in this situation.
2617 * - we don't move root/cwd if they are not at the root (reason: if something
2618 * cared enough to change them, it's probably wrong to force them elsewhere)
2619 * - it's okay to pick a root that isn't the root of a file system, e.g.
2620 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2621 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2624 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2625 const char __user *, put_old)
2627 struct path new, old, parent_path, root_parent, root;
2628 struct mount *new_mnt, *root_mnt, *old_mnt;
2629 struct mountpoint *old_mp, *root_mp;
2635 error = user_path_dir(new_root, &new);
2639 error = user_path_dir(put_old, &old);
2643 error = security_sb_pivotroot(&old, &new);
2647 get_fs_root(current->fs, &root);
2648 old_mp = lock_mount(&old);
2649 error = PTR_ERR(old_mp);
2654 new_mnt = real_mount(new.mnt);
2655 root_mnt = real_mount(root.mnt);
2656 old_mnt = real_mount(old.mnt);
2657 if (IS_MNT_SHARED(old_mnt) ||
2658 IS_MNT_SHARED(new_mnt->mnt_parent) ||
2659 IS_MNT_SHARED(root_mnt->mnt_parent))
2661 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
2663 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
2666 if (d_unlinked(new.dentry))
2669 if (new_mnt == root_mnt || old_mnt == root_mnt)
2670 goto out4; /* loop, on the same file system */
2672 if (root.mnt->mnt_root != root.dentry)
2673 goto out4; /* not a mountpoint */
2674 if (!mnt_has_parent(root_mnt))
2675 goto out4; /* not attached */
2676 root_mp = root_mnt->mnt_mp;
2677 if (new.mnt->mnt_root != new.dentry)
2678 goto out4; /* not a mountpoint */
2679 if (!mnt_has_parent(new_mnt))
2680 goto out4; /* not attached */
2681 /* make sure we can reach put_old from new_root */
2682 if (!is_path_reachable(old_mnt, old.dentry, &new))
2684 root_mp->m_count++; /* pin it so it won't go away */
2685 br_write_lock(&vfsmount_lock);
2686 detach_mnt(new_mnt, &parent_path);
2687 detach_mnt(root_mnt, &root_parent);
2688 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
2689 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
2690 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2692 /* mount old root on put_old */
2693 attach_mnt(root_mnt, old_mnt, old_mp);
2694 /* mount new_root on / */
2695 attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
2696 touch_mnt_namespace(current->nsproxy->mnt_ns);
2697 br_write_unlock(&vfsmount_lock);
2698 chroot_fs_refs(&root, &new);
2699 put_mountpoint(root_mp);
2702 unlock_mount(old_mp);
2704 path_put(&root_parent);
2705 path_put(&parent_path);
2717 static void __init init_mount_tree(void)
2719 struct vfsmount *mnt;
2720 struct mnt_namespace *ns;
2722 struct file_system_type *type;
2724 type = get_fs_type("rootfs");
2726 panic("Can't find rootfs type");
2727 mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
2728 put_filesystem(type);
2730 panic("Can't create rootfs");
2732 ns = create_mnt_ns(mnt);
2734 panic("Can't allocate initial namespace");
2736 init_task.nsproxy->mnt_ns = ns;
2740 root.dentry = mnt->mnt_root;
2742 set_fs_pwd(current->fs, &root);
2743 set_fs_root(current->fs, &root);
2746 void __init mnt_init(void)
2751 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
2752 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2754 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2755 mountpoint_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2757 if (!mount_hashtable || !mountpoint_hashtable)
2758 panic("Failed to allocate mount hash table\n");
2760 printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);
2762 for (u = 0; u < HASH_SIZE; u++)
2763 INIT_LIST_HEAD(&mount_hashtable[u]);
2764 for (u = 0; u < HASH_SIZE; u++)
2765 INIT_LIST_HEAD(&mountpoint_hashtable[u]);
2767 br_lock_init(&vfsmount_lock);
2771 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2773 fs_kobj = kobject_create_and_add("fs", NULL);
2775 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2780 void put_mnt_ns(struct mnt_namespace *ns)
2782 if (!atomic_dec_and_test(&ns->count))
2784 drop_collected_mounts(&ns->root->mnt);
2788 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2790 struct vfsmount *mnt;
2791 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2794 * it is a longterm mount, don't release mnt until
2795 * we unmount before file sys is unregistered
2797 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
2801 EXPORT_SYMBOL_GPL(kern_mount_data);
2803 void kern_unmount(struct vfsmount *mnt)
2805 /* release long term mount so mount point can be released */
2806 if (!IS_ERR_OR_NULL(mnt)) {
2807 br_write_lock(&vfsmount_lock);
2808 real_mount(mnt)->mnt_ns = NULL;
2809 br_write_unlock(&vfsmount_lock);
2813 EXPORT_SYMBOL(kern_unmount);
2815 bool our_mnt(struct vfsmount *mnt)
2817 return check_mnt(real_mount(mnt));
2820 bool current_chrooted(void)
2822 /* Does the current process have a non-standard root */
2823 struct path ns_root;
2824 struct path fs_root;
2827 /* Find the namespace root */
2828 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
2829 ns_root.dentry = ns_root.mnt->mnt_root;
2831 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
2834 get_fs_root(current->fs, &fs_root);
2836 chrooted = !path_equal(&fs_root, &ns_root);
2844 bool fs_fully_visible(struct file_system_type *type)
2846 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
2848 bool visible = false;
2853 down_read(&namespace_sem);
2854 list_for_each_entry(mnt, &ns->list, mnt_list) {
2855 struct mount *child;
2856 if (mnt->mnt.mnt_sb->s_type != type)
2859 /* This mount is not fully visible if there are any child mounts
2860 * that cover anything except for empty directories.
2862 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2863 struct inode *inode = child->mnt_mountpoint->d_inode;
2864 if (!S_ISDIR(inode->i_mode))
2866 if (inode->i_nlink != 2)
2874 up_read(&namespace_sem);
2878 static void *mntns_get(struct task_struct *task)
2880 struct mnt_namespace *ns = NULL;
2881 struct nsproxy *nsproxy;
2884 nsproxy = task_nsproxy(task);
2886 ns = nsproxy->mnt_ns;
2894 static void mntns_put(void *ns)
2899 static int mntns_install(struct nsproxy *nsproxy, void *ns)
2901 struct fs_struct *fs = current->fs;
2902 struct mnt_namespace *mnt_ns = ns;
2905 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
2906 !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
2907 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
2914 put_mnt_ns(nsproxy->mnt_ns);
2915 nsproxy->mnt_ns = mnt_ns;
2918 root.mnt = &mnt_ns->root->mnt;
2919 root.dentry = mnt_ns->root->mnt.mnt_root;
2921 while(d_mountpoint(root.dentry) && follow_down_one(&root))
2924 /* Update the pwd and root */
2925 set_fs_pwd(fs, &root);
2926 set_fs_root(fs, &root);
2932 static unsigned int mntns_inum(void *ns)
2934 struct mnt_namespace *mnt_ns = ns;
2935 return mnt_ns->proc_inum;
2938 const struct proc_ns_operations mntns_operations = {
2940 .type = CLONE_NEWNS,
2943 .install = mntns_install,