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/ramfs.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 struct rw_semaphore 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);
66 #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)
69 * allocation is serialized by namespace_sem, but we need the spinlock to
70 * serialize with freeing.
72 static int mnt_alloc_id(struct mount *mnt)
77 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
78 spin_lock(&mnt_id_lock);
79 res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
81 mnt_id_start = mnt->mnt_id + 1;
82 spin_unlock(&mnt_id_lock);
89 static void mnt_free_id(struct mount *mnt)
92 spin_lock(&mnt_id_lock);
93 ida_remove(&mnt_id_ida, id);
94 if (mnt_id_start > id)
96 spin_unlock(&mnt_id_lock);
100 * Allocate a new peer group ID
102 * mnt_group_ida is protected by namespace_sem
104 static int mnt_alloc_group_id(struct mount *mnt)
108 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
111 res = ida_get_new_above(&mnt_group_ida,
115 mnt_group_start = mnt->mnt_group_id + 1;
121 * Release a peer group ID
123 void mnt_release_group_id(struct mount *mnt)
125 int id = mnt->mnt_group_id;
126 ida_remove(&mnt_group_ida, id);
127 if (mnt_group_start > id)
128 mnt_group_start = id;
129 mnt->mnt_group_id = 0;
133 * vfsmount lock must be held for read
135 static inline void mnt_add_count(struct mount *mnt, int n)
138 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
147 * vfsmount lock must be held for write
149 unsigned int mnt_get_count(struct mount *mnt)
152 unsigned int count = 0;
155 for_each_possible_cpu(cpu) {
156 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
161 return mnt->mnt_count;
165 static struct mount *alloc_vfsmnt(const char *name)
167 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
171 err = mnt_alloc_id(mnt);
176 mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
177 if (!mnt->mnt_devname)
182 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
184 goto out_free_devname;
186 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
189 mnt->mnt_writers = 0;
192 INIT_LIST_HEAD(&mnt->mnt_hash);
193 INIT_LIST_HEAD(&mnt->mnt_child);
194 INIT_LIST_HEAD(&mnt->mnt_mounts);
195 INIT_LIST_HEAD(&mnt->mnt_list);
196 INIT_LIST_HEAD(&mnt->mnt_expire);
197 INIT_LIST_HEAD(&mnt->mnt_share);
198 INIT_LIST_HEAD(&mnt->mnt_slave_list);
199 INIT_LIST_HEAD(&mnt->mnt_slave);
200 #ifdef CONFIG_FSNOTIFY
201 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
208 kfree(mnt->mnt_devname);
213 kmem_cache_free(mnt_cache, mnt);
218 * Most r/o checks on a fs are for operations that take
219 * discrete amounts of time, like a write() or unlink().
220 * We must keep track of when those operations start
221 * (for permission checks) and when they end, so that
222 * we can determine when writes are able to occur to
226 * __mnt_is_readonly: check whether a mount is read-only
227 * @mnt: the mount to check for its write status
229 * This shouldn't be used directly ouside of the VFS.
230 * It does not guarantee that the filesystem will stay
231 * r/w, just that it is right *now*. This can not and
232 * should not be used in place of IS_RDONLY(inode).
233 * mnt_want/drop_write() will _keep_ the filesystem
236 int __mnt_is_readonly(struct vfsmount *mnt)
238 if (mnt->mnt_flags & MNT_READONLY)
240 if (mnt->mnt_sb->s_flags & MS_RDONLY)
244 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
246 static inline void mnt_inc_writers(struct mount *mnt)
249 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
255 static inline void mnt_dec_writers(struct mount *mnt)
258 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
264 static unsigned int mnt_get_writers(struct mount *mnt)
267 unsigned int count = 0;
270 for_each_possible_cpu(cpu) {
271 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
276 return mnt->mnt_writers;
280 static int mnt_is_readonly(struct vfsmount *mnt)
282 if (mnt->mnt_sb->s_readonly_remount)
284 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
286 return __mnt_is_readonly(mnt);
290 * Most r/o & frozen checks on a fs are for operations that take discrete
291 * amounts of time, like a write() or unlink(). We must keep track of when
292 * those operations start (for permission checks) and when they end, so that we
293 * can determine when writes are able to occur to a filesystem.
296 * __mnt_want_write - get write access to a mount without freeze protection
297 * @m: the mount on which to take a write
299 * This tells the low-level filesystem that a write is about to be performed to
300 * it, and makes sure that writes are allowed (mnt it read-write) before
301 * returning success. This operation does not protect against filesystem being
302 * frozen. When the write operation is finished, __mnt_drop_write() must be
303 * called. This is effectively a refcount.
305 int __mnt_want_write(struct vfsmount *m)
307 struct mount *mnt = real_mount(m);
311 mnt_inc_writers(mnt);
313 * The store to mnt_inc_writers must be visible before we pass
314 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
315 * incremented count after it has set MNT_WRITE_HOLD.
318 while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
321 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
322 * be set to match its requirements. So we must not load that until
323 * MNT_WRITE_HOLD is cleared.
326 if (mnt_is_readonly(m)) {
327 mnt_dec_writers(mnt);
336 * mnt_want_write - get write access to a mount
337 * @m: the mount on which to take a write
339 * This tells the low-level filesystem that a write is about to be performed to
340 * it, and makes sure that writes are allowed (mount is read-write, filesystem
341 * is not frozen) before returning success. When the write operation is
342 * finished, mnt_drop_write() must be called. This is effectively a refcount.
344 int mnt_want_write(struct vfsmount *m)
348 sb_start_write(m->mnt_sb);
349 ret = __mnt_want_write(m);
351 sb_end_write(m->mnt_sb);
354 EXPORT_SYMBOL_GPL(mnt_want_write);
357 * mnt_clone_write - get write access to a mount
358 * @mnt: the mount on which to take a write
360 * This is effectively like mnt_want_write, except
361 * it must only be used to take an extra write reference
362 * on a mountpoint that we already know has a write reference
363 * on it. This allows some optimisation.
365 * After finished, mnt_drop_write must be called as usual to
366 * drop the reference.
368 int mnt_clone_write(struct vfsmount *mnt)
370 /* superblock may be r/o */
371 if (__mnt_is_readonly(mnt))
374 mnt_inc_writers(real_mount(mnt));
378 EXPORT_SYMBOL_GPL(mnt_clone_write);
381 * __mnt_want_write_file - get write access to a file's mount
382 * @file: the file who's mount on which to take a write
384 * This is like __mnt_want_write, but it takes a file and can
385 * do some optimisations if the file is open for write already
387 int __mnt_want_write_file(struct file *file)
389 struct inode *inode = file_inode(file);
391 if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
392 return __mnt_want_write(file->f_path.mnt);
394 return mnt_clone_write(file->f_path.mnt);
398 * mnt_want_write_file - get write access to a file's mount
399 * @file: the file who's mount on which to take a write
401 * This is like mnt_want_write, but it takes a file and can
402 * do some optimisations if the file is open for write already
404 int mnt_want_write_file(struct file *file)
408 sb_start_write(file->f_path.mnt->mnt_sb);
409 ret = __mnt_want_write_file(file);
411 sb_end_write(file->f_path.mnt->mnt_sb);
414 EXPORT_SYMBOL_GPL(mnt_want_write_file);
417 * __mnt_drop_write - give up write access to a mount
418 * @mnt: the mount on which to give up write access
420 * Tells the low-level filesystem that we are done
421 * performing writes to it. Must be matched with
422 * __mnt_want_write() call above.
424 void __mnt_drop_write(struct vfsmount *mnt)
427 mnt_dec_writers(real_mount(mnt));
432 * mnt_drop_write - give up write access to a mount
433 * @mnt: the mount on which to give up write access
435 * Tells the low-level filesystem that we are done performing writes to it and
436 * also allows filesystem to be frozen again. Must be matched with
437 * mnt_want_write() call above.
439 void mnt_drop_write(struct vfsmount *mnt)
441 __mnt_drop_write(mnt);
442 sb_end_write(mnt->mnt_sb);
444 EXPORT_SYMBOL_GPL(mnt_drop_write);
446 void __mnt_drop_write_file(struct file *file)
448 __mnt_drop_write(file->f_path.mnt);
451 void mnt_drop_write_file(struct file *file)
453 mnt_drop_write(file->f_path.mnt);
455 EXPORT_SYMBOL(mnt_drop_write_file);
457 static int mnt_make_readonly(struct mount *mnt)
461 br_write_lock(&vfsmount_lock);
462 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
464 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
465 * should be visible before we do.
470 * With writers on hold, if this value is zero, then there are
471 * definitely no active writers (although held writers may subsequently
472 * increment the count, they'll have to wait, and decrement it after
473 * seeing MNT_READONLY).
475 * It is OK to have counter incremented on one CPU and decremented on
476 * another: the sum will add up correctly. The danger would be when we
477 * sum up each counter, if we read a counter before it is incremented,
478 * but then read another CPU's count which it has been subsequently
479 * decremented from -- we would see more decrements than we should.
480 * MNT_WRITE_HOLD protects against this scenario, because
481 * mnt_want_write first increments count, then smp_mb, then spins on
482 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
483 * we're counting up here.
485 if (mnt_get_writers(mnt) > 0)
488 mnt->mnt.mnt_flags |= MNT_READONLY;
490 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
491 * that become unheld will see MNT_READONLY.
494 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
495 br_write_unlock(&vfsmount_lock);
499 static void __mnt_unmake_readonly(struct mount *mnt)
501 br_write_lock(&vfsmount_lock);
502 mnt->mnt.mnt_flags &= ~MNT_READONLY;
503 br_write_unlock(&vfsmount_lock);
506 int sb_prepare_remount_readonly(struct super_block *sb)
511 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
512 if (atomic_long_read(&sb->s_remove_count))
515 br_write_lock(&vfsmount_lock);
516 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
517 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
518 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
520 if (mnt_get_writers(mnt) > 0) {
526 if (!err && atomic_long_read(&sb->s_remove_count))
530 sb->s_readonly_remount = 1;
533 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
534 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
535 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
537 br_write_unlock(&vfsmount_lock);
542 static void free_vfsmnt(struct mount *mnt)
544 kfree(mnt->mnt_devname);
547 free_percpu(mnt->mnt_pcp);
549 kmem_cache_free(mnt_cache, mnt);
553 * find the first or last mount at @dentry on vfsmount @mnt depending on
554 * @dir. If @dir is set return the first mount else return the last mount.
555 * vfsmount_lock must be held for read or write.
557 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
560 struct list_head *head = mount_hashtable + hash(mnt, dentry);
561 struct list_head *tmp = head;
562 struct mount *p, *found = NULL;
565 tmp = dir ? tmp->next : tmp->prev;
569 p = list_entry(tmp, struct mount, mnt_hash);
570 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) {
579 * lookup_mnt - Return the first child mount mounted at path
581 * "First" means first mounted chronologically. If you create the
584 * mount /dev/sda1 /mnt
585 * mount /dev/sda2 /mnt
586 * mount /dev/sda3 /mnt
588 * Then lookup_mnt() on the base /mnt dentry in the root mount will
589 * return successively the root dentry and vfsmount of /dev/sda1, then
590 * /dev/sda2, then /dev/sda3, then NULL.
592 * lookup_mnt takes a reference to the found vfsmount.
594 struct vfsmount *lookup_mnt(struct path *path)
596 struct mount *child_mnt;
598 br_read_lock(&vfsmount_lock);
599 child_mnt = __lookup_mnt(path->mnt, path->dentry, 1);
601 mnt_add_count(child_mnt, 1);
602 br_read_unlock(&vfsmount_lock);
603 return &child_mnt->mnt;
605 br_read_unlock(&vfsmount_lock);
610 static struct mountpoint *new_mountpoint(struct dentry *dentry)
612 struct list_head *chain = mountpoint_hashtable + hash(NULL, dentry);
613 struct mountpoint *mp;
615 list_for_each_entry(mp, chain, m_hash) {
616 if (mp->m_dentry == dentry) {
617 /* might be worth a WARN_ON() */
618 if (d_unlinked(dentry))
619 return ERR_PTR(-ENOENT);
625 mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
627 return ERR_PTR(-ENOMEM);
629 spin_lock(&dentry->d_lock);
630 if (d_unlinked(dentry)) {
631 spin_unlock(&dentry->d_lock);
633 return ERR_PTR(-ENOENT);
635 dentry->d_flags |= DCACHE_MOUNTED;
636 spin_unlock(&dentry->d_lock);
637 mp->m_dentry = dentry;
639 list_add(&mp->m_hash, chain);
643 static void put_mountpoint(struct mountpoint *mp)
645 if (!--mp->m_count) {
646 struct dentry *dentry = mp->m_dentry;
647 spin_lock(&dentry->d_lock);
648 dentry->d_flags &= ~DCACHE_MOUNTED;
649 spin_unlock(&dentry->d_lock);
650 list_del(&mp->m_hash);
655 static inline int check_mnt(struct mount *mnt)
657 return mnt->mnt_ns == current->nsproxy->mnt_ns;
661 * vfsmount lock must be held for write
663 static void touch_mnt_namespace(struct mnt_namespace *ns)
667 wake_up_interruptible(&ns->poll);
672 * vfsmount lock must be held for write
674 static void __touch_mnt_namespace(struct mnt_namespace *ns)
676 if (ns && ns->event != event) {
678 wake_up_interruptible(&ns->poll);
683 * vfsmount lock must be held for write
685 static void detach_mnt(struct mount *mnt, struct path *old_path)
687 old_path->dentry = mnt->mnt_mountpoint;
688 old_path->mnt = &mnt->mnt_parent->mnt;
689 mnt->mnt_parent = mnt;
690 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
691 list_del_init(&mnt->mnt_child);
692 list_del_init(&mnt->mnt_hash);
693 put_mountpoint(mnt->mnt_mp);
698 * vfsmount lock must be held for write
700 void mnt_set_mountpoint(struct mount *mnt,
701 struct mountpoint *mp,
702 struct mount *child_mnt)
705 mnt_add_count(mnt, 1); /* essentially, that's mntget */
706 child_mnt->mnt_mountpoint = dget(mp->m_dentry);
707 child_mnt->mnt_parent = mnt;
708 child_mnt->mnt_mp = mp;
712 * vfsmount lock must be held for write
714 static void attach_mnt(struct mount *mnt,
715 struct mount *parent,
716 struct mountpoint *mp)
718 mnt_set_mountpoint(parent, mp, mnt);
719 list_add_tail(&mnt->mnt_hash, mount_hashtable +
720 hash(&parent->mnt, mp->m_dentry));
721 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
725 * vfsmount lock must be held for write
727 static void commit_tree(struct mount *mnt)
729 struct mount *parent = mnt->mnt_parent;
732 struct mnt_namespace *n = parent->mnt_ns;
734 BUG_ON(parent == mnt);
736 list_add_tail(&head, &mnt->mnt_list);
737 list_for_each_entry(m, &head, mnt_list)
740 list_splice(&head, n->list.prev);
742 list_add_tail(&mnt->mnt_hash, mount_hashtable +
743 hash(&parent->mnt, mnt->mnt_mountpoint));
744 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
745 touch_mnt_namespace(n);
748 static struct mount *next_mnt(struct mount *p, struct mount *root)
750 struct list_head *next = p->mnt_mounts.next;
751 if (next == &p->mnt_mounts) {
755 next = p->mnt_child.next;
756 if (next != &p->mnt_parent->mnt_mounts)
761 return list_entry(next, struct mount, mnt_child);
764 static struct mount *skip_mnt_tree(struct mount *p)
766 struct list_head *prev = p->mnt_mounts.prev;
767 while (prev != &p->mnt_mounts) {
768 p = list_entry(prev, struct mount, mnt_child);
769 prev = p->mnt_mounts.prev;
775 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
781 return ERR_PTR(-ENODEV);
783 mnt = alloc_vfsmnt(name);
785 return ERR_PTR(-ENOMEM);
787 if (flags & MS_KERNMOUNT)
788 mnt->mnt.mnt_flags = MNT_INTERNAL;
790 root = mount_fs(type, flags, name, data);
793 return ERR_CAST(root);
796 mnt->mnt.mnt_root = root;
797 mnt->mnt.mnt_sb = root->d_sb;
798 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
799 mnt->mnt_parent = mnt;
800 br_write_lock(&vfsmount_lock);
801 list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
802 br_write_unlock(&vfsmount_lock);
805 EXPORT_SYMBOL_GPL(vfs_kern_mount);
807 static struct mount *clone_mnt(struct mount *old, struct dentry *root,
810 struct super_block *sb = old->mnt.mnt_sb;
814 mnt = alloc_vfsmnt(old->mnt_devname);
816 return ERR_PTR(-ENOMEM);
818 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
819 mnt->mnt_group_id = 0; /* not a peer of original */
821 mnt->mnt_group_id = old->mnt_group_id;
823 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
824 err = mnt_alloc_group_id(mnt);
829 mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
830 /* Don't allow unprivileged users to change mount flags */
831 if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
832 mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
834 /* Don't allow unprivileged users to reveal what is under a mount */
835 if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
836 mnt->mnt.mnt_flags |= MNT_LOCKED;
838 atomic_inc(&sb->s_active);
839 mnt->mnt.mnt_sb = sb;
840 mnt->mnt.mnt_root = dget(root);
841 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
842 mnt->mnt_parent = mnt;
843 br_write_lock(&vfsmount_lock);
844 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
845 br_write_unlock(&vfsmount_lock);
847 if ((flag & CL_SLAVE) ||
848 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
849 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
850 mnt->mnt_master = old;
851 CLEAR_MNT_SHARED(mnt);
852 } else if (!(flag & CL_PRIVATE)) {
853 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
854 list_add(&mnt->mnt_share, &old->mnt_share);
855 if (IS_MNT_SLAVE(old))
856 list_add(&mnt->mnt_slave, &old->mnt_slave);
857 mnt->mnt_master = old->mnt_master;
859 if (flag & CL_MAKE_SHARED)
862 /* stick the duplicate mount on the same expiry list
863 * as the original if that was on one */
864 if (flag & CL_EXPIRE) {
865 if (!list_empty(&old->mnt_expire))
866 list_add(&mnt->mnt_expire, &old->mnt_expire);
876 static inline void mntfree(struct mount *mnt)
878 struct vfsmount *m = &mnt->mnt;
879 struct super_block *sb = m->mnt_sb;
882 * This probably indicates that somebody messed
883 * up a mnt_want/drop_write() pair. If this
884 * happens, the filesystem was probably unable
885 * to make r/w->r/o transitions.
888 * The locking used to deal with mnt_count decrement provides barriers,
889 * so mnt_get_writers() below is safe.
891 WARN_ON(mnt_get_writers(mnt));
892 fsnotify_vfsmount_delete(m);
895 deactivate_super(sb);
898 static void mntput_no_expire(struct mount *mnt)
902 br_read_lock(&vfsmount_lock);
903 if (likely(mnt->mnt_ns)) {
904 /* shouldn't be the last one */
905 mnt_add_count(mnt, -1);
906 br_read_unlock(&vfsmount_lock);
909 br_read_unlock(&vfsmount_lock);
911 br_write_lock(&vfsmount_lock);
912 mnt_add_count(mnt, -1);
913 if (mnt_get_count(mnt)) {
914 br_write_unlock(&vfsmount_lock);
918 mnt_add_count(mnt, -1);
919 if (likely(mnt_get_count(mnt)))
921 br_write_lock(&vfsmount_lock);
923 if (unlikely(mnt->mnt_pinned)) {
924 mnt_add_count(mnt, mnt->mnt_pinned + 1);
926 br_write_unlock(&vfsmount_lock);
927 acct_auto_close_mnt(&mnt->mnt);
931 list_del(&mnt->mnt_instance);
932 br_write_unlock(&vfsmount_lock);
936 void mntput(struct vfsmount *mnt)
939 struct mount *m = real_mount(mnt);
940 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
941 if (unlikely(m->mnt_expiry_mark))
942 m->mnt_expiry_mark = 0;
946 EXPORT_SYMBOL(mntput);
948 struct vfsmount *mntget(struct vfsmount *mnt)
951 mnt_add_count(real_mount(mnt), 1);
954 EXPORT_SYMBOL(mntget);
956 void mnt_pin(struct vfsmount *mnt)
958 br_write_lock(&vfsmount_lock);
959 real_mount(mnt)->mnt_pinned++;
960 br_write_unlock(&vfsmount_lock);
962 EXPORT_SYMBOL(mnt_pin);
964 void mnt_unpin(struct vfsmount *m)
966 struct mount *mnt = real_mount(m);
967 br_write_lock(&vfsmount_lock);
968 if (mnt->mnt_pinned) {
969 mnt_add_count(mnt, 1);
972 br_write_unlock(&vfsmount_lock);
974 EXPORT_SYMBOL(mnt_unpin);
976 static inline void mangle(struct seq_file *m, const char *s)
978 seq_escape(m, s, " \t\n\\");
982 * Simple .show_options callback for filesystems which don't want to
983 * implement more complex mount option showing.
985 * See also save_mount_options().
987 int generic_show_options(struct seq_file *m, struct dentry *root)
992 options = rcu_dereference(root->d_sb->s_options);
994 if (options != NULL && options[0]) {
1002 EXPORT_SYMBOL(generic_show_options);
1005 * If filesystem uses generic_show_options(), this function should be
1006 * called from the fill_super() callback.
1008 * The .remount_fs callback usually needs to be handled in a special
1009 * way, to make sure, that previous options are not overwritten if the
1012 * Also note, that if the filesystem's .remount_fs function doesn't
1013 * reset all options to their default value, but changes only newly
1014 * given options, then the displayed options will not reflect reality
1017 void save_mount_options(struct super_block *sb, char *options)
1019 BUG_ON(sb->s_options);
1020 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
1022 EXPORT_SYMBOL(save_mount_options);
1024 void replace_mount_options(struct super_block *sb, char *options)
1026 char *old = sb->s_options;
1027 rcu_assign_pointer(sb->s_options, options);
1033 EXPORT_SYMBOL(replace_mount_options);
1035 #ifdef CONFIG_PROC_FS
1036 /* iterator; we want it to have access to namespace_sem, thus here... */
1037 static void *m_start(struct seq_file *m, loff_t *pos)
1039 struct proc_mounts *p = proc_mounts(m);
1041 down_read(&namespace_sem);
1042 return seq_list_start(&p->ns->list, *pos);
1045 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1047 struct proc_mounts *p = proc_mounts(m);
1049 return seq_list_next(v, &p->ns->list, pos);
1052 static void m_stop(struct seq_file *m, void *v)
1054 up_read(&namespace_sem);
1057 static int m_show(struct seq_file *m, void *v)
1059 struct proc_mounts *p = proc_mounts(m);
1060 struct mount *r = list_entry(v, struct mount, mnt_list);
1061 return p->show(m, &r->mnt);
1064 const struct seq_operations mounts_op = {
1070 #endif /* CONFIG_PROC_FS */
1073 * may_umount_tree - check if a mount tree is busy
1074 * @mnt: root of mount tree
1076 * This is called to check if a tree of mounts has any
1077 * open files, pwds, chroots or sub mounts that are
1080 int may_umount_tree(struct vfsmount *m)
1082 struct mount *mnt = real_mount(m);
1083 int actual_refs = 0;
1084 int minimum_refs = 0;
1088 /* write lock needed for mnt_get_count */
1089 br_write_lock(&vfsmount_lock);
1090 for (p = mnt; p; p = next_mnt(p, mnt)) {
1091 actual_refs += mnt_get_count(p);
1094 br_write_unlock(&vfsmount_lock);
1096 if (actual_refs > minimum_refs)
1102 EXPORT_SYMBOL(may_umount_tree);
1105 * may_umount - check if a mount point is busy
1106 * @mnt: root of mount
1108 * This is called to check if a mount point has any
1109 * open files, pwds, chroots or sub mounts. If the
1110 * mount has sub mounts this will return busy
1111 * regardless of whether the sub mounts are busy.
1113 * Doesn't take quota and stuff into account. IOW, in some cases it will
1114 * give false negatives. The main reason why it's here is that we need
1115 * a non-destructive way to look for easily umountable filesystems.
1117 int may_umount(struct vfsmount *mnt)
1120 down_read(&namespace_sem);
1121 br_write_lock(&vfsmount_lock);
1122 if (propagate_mount_busy(real_mount(mnt), 2))
1124 br_write_unlock(&vfsmount_lock);
1125 up_read(&namespace_sem);
1129 EXPORT_SYMBOL(may_umount);
1131 static LIST_HEAD(unmounted); /* protected by namespace_sem */
1133 static void namespace_unlock(void)
1138 if (likely(list_empty(&unmounted))) {
1139 up_write(&namespace_sem);
1143 list_splice_init(&unmounted, &head);
1144 up_write(&namespace_sem);
1146 while (!list_empty(&head)) {
1147 mnt = list_first_entry(&head, struct mount, mnt_hash);
1148 list_del_init(&mnt->mnt_hash);
1149 if (mnt_has_parent(mnt)) {
1150 struct dentry *dentry;
1153 br_write_lock(&vfsmount_lock);
1154 dentry = mnt->mnt_mountpoint;
1155 m = mnt->mnt_parent;
1156 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
1157 mnt->mnt_parent = mnt;
1159 br_write_unlock(&vfsmount_lock);
1167 static inline void namespace_lock(void)
1169 down_write(&namespace_sem);
1173 * vfsmount lock must be held for write
1174 * namespace_sem must be held for write
1176 void umount_tree(struct mount *mnt, int propagate)
1178 LIST_HEAD(tmp_list);
1181 for (p = mnt; p; p = next_mnt(p, mnt))
1182 list_move(&p->mnt_hash, &tmp_list);
1185 propagate_umount(&tmp_list);
1187 list_for_each_entry(p, &tmp_list, mnt_hash) {
1188 list_del_init(&p->mnt_expire);
1189 list_del_init(&p->mnt_list);
1190 __touch_mnt_namespace(p->mnt_ns);
1192 list_del_init(&p->mnt_child);
1193 if (mnt_has_parent(p)) {
1194 p->mnt_parent->mnt_ghosts++;
1195 put_mountpoint(p->mnt_mp);
1198 change_mnt_propagation(p, MS_PRIVATE);
1200 list_splice(&tmp_list, &unmounted);
1203 static void shrink_submounts(struct mount *mnt);
1205 static int do_umount(struct mount *mnt, int flags)
1207 struct super_block *sb = mnt->mnt.mnt_sb;
1210 retval = security_sb_umount(&mnt->mnt, flags);
1215 * Allow userspace to request a mountpoint be expired rather than
1216 * unmounting unconditionally. Unmount only happens if:
1217 * (1) the mark is already set (the mark is cleared by mntput())
1218 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1220 if (flags & MNT_EXPIRE) {
1221 if (&mnt->mnt == current->fs->root.mnt ||
1222 flags & (MNT_FORCE | MNT_DETACH))
1226 * probably don't strictly need the lock here if we examined
1227 * all race cases, but it's a slowpath.
1229 br_write_lock(&vfsmount_lock);
1230 if (mnt_get_count(mnt) != 2) {
1231 br_write_unlock(&vfsmount_lock);
1234 br_write_unlock(&vfsmount_lock);
1236 if (!xchg(&mnt->mnt_expiry_mark, 1))
1241 * If we may have to abort operations to get out of this
1242 * mount, and they will themselves hold resources we must
1243 * allow the fs to do things. In the Unix tradition of
1244 * 'Gee thats tricky lets do it in userspace' the umount_begin
1245 * might fail to complete on the first run through as other tasks
1246 * must return, and the like. Thats for the mount program to worry
1247 * about for the moment.
1250 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1251 sb->s_op->umount_begin(sb);
1255 * No sense to grab the lock for this test, but test itself looks
1256 * somewhat bogus. Suggestions for better replacement?
1257 * Ho-hum... In principle, we might treat that as umount + switch
1258 * to rootfs. GC would eventually take care of the old vfsmount.
1259 * Actually it makes sense, especially if rootfs would contain a
1260 * /reboot - static binary that would close all descriptors and
1261 * call reboot(9). Then init(8) could umount root and exec /reboot.
1263 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1265 * Special case for "unmounting" root ...
1266 * we just try to remount it readonly.
1268 down_write(&sb->s_umount);
1269 if (!(sb->s_flags & MS_RDONLY))
1270 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1271 up_write(&sb->s_umount);
1276 br_write_lock(&vfsmount_lock);
1279 if (!(flags & MNT_DETACH))
1280 shrink_submounts(mnt);
1283 if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
1284 if (!list_empty(&mnt->mnt_list))
1285 umount_tree(mnt, 1);
1288 br_write_unlock(&vfsmount_lock);
1294 * Is the caller allowed to modify his namespace?
1296 static inline bool may_mount(void)
1298 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1302 * Now umount can handle mount points as well as block devices.
1303 * This is important for filesystems which use unnamed block devices.
1305 * We now support a flag for forced unmount like the other 'big iron'
1306 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1309 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1314 int lookup_flags = 0;
1316 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1322 if (!(flags & UMOUNT_NOFOLLOW))
1323 lookup_flags |= LOOKUP_FOLLOW;
1325 retval = user_path_at(AT_FDCWD, name, lookup_flags, &path);
1328 mnt = real_mount(path.mnt);
1330 if (path.dentry != path.mnt->mnt_root)
1332 if (!check_mnt(mnt))
1334 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1337 retval = do_umount(mnt, flags);
1339 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1341 mntput_no_expire(mnt);
1346 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1349 * The 2.0 compatible umount. No flags.
1351 SYSCALL_DEFINE1(oldumount, char __user *, name)
1353 return sys_umount(name, 0);
1358 static bool is_mnt_ns_file(struct dentry *dentry)
1360 /* Is this a proxy for a mount namespace? */
1361 struct inode *inode = dentry->d_inode;
1364 if (!proc_ns_inode(inode))
1367 ei = get_proc_ns(inode);
1368 if (ei->ns_ops != &mntns_operations)
1374 static bool mnt_ns_loop(struct dentry *dentry)
1376 /* Could bind mounting the mount namespace inode cause a
1377 * mount namespace loop?
1379 struct mnt_namespace *mnt_ns;
1380 if (!is_mnt_ns_file(dentry))
1383 mnt_ns = get_proc_ns(dentry->d_inode)->ns;
1384 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1387 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1390 struct mount *res, *p, *q, *r, *parent;
1392 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1393 return ERR_PTR(-EINVAL);
1395 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1396 return ERR_PTR(-EINVAL);
1398 res = q = clone_mnt(mnt, dentry, flag);
1402 q->mnt.mnt_flags &= ~MNT_LOCKED;
1403 q->mnt_mountpoint = mnt->mnt_mountpoint;
1406 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1408 if (!is_subdir(r->mnt_mountpoint, dentry))
1411 for (s = r; s; s = next_mnt(s, r)) {
1412 if (!(flag & CL_COPY_UNBINDABLE) &&
1413 IS_MNT_UNBINDABLE(s)) {
1414 s = skip_mnt_tree(s);
1417 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1418 is_mnt_ns_file(s->mnt.mnt_root)) {
1419 s = skip_mnt_tree(s);
1422 while (p != s->mnt_parent) {
1428 q = clone_mnt(p, p->mnt.mnt_root, flag);
1431 br_write_lock(&vfsmount_lock);
1432 list_add_tail(&q->mnt_list, &res->mnt_list);
1433 attach_mnt(q, parent, p->mnt_mp);
1434 br_write_unlock(&vfsmount_lock);
1440 br_write_lock(&vfsmount_lock);
1441 umount_tree(res, 0);
1442 br_write_unlock(&vfsmount_lock);
1447 /* Caller should check returned pointer for errors */
1449 struct vfsmount *collect_mounts(struct path *path)
1453 tree = copy_tree(real_mount(path->mnt), path->dentry,
1454 CL_COPY_ALL | CL_PRIVATE);
1461 void drop_collected_mounts(struct vfsmount *mnt)
1464 br_write_lock(&vfsmount_lock);
1465 umount_tree(real_mount(mnt), 0);
1466 br_write_unlock(&vfsmount_lock);
1470 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1471 struct vfsmount *root)
1474 int res = f(root, arg);
1477 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1478 res = f(&mnt->mnt, arg);
1485 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1489 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1490 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1491 mnt_release_group_id(p);
1495 static int invent_group_ids(struct mount *mnt, bool recurse)
1499 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1500 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1501 int err = mnt_alloc_group_id(p);
1503 cleanup_group_ids(mnt, p);
1513 * @source_mnt : mount tree to be attached
1514 * @nd : place the mount tree @source_mnt is attached
1515 * @parent_nd : if non-null, detach the source_mnt from its parent and
1516 * store the parent mount and mountpoint dentry.
1517 * (done when source_mnt is moved)
1519 * NOTE: in the table below explains the semantics when a source mount
1520 * of a given type is attached to a destination mount of a given type.
1521 * ---------------------------------------------------------------------------
1522 * | BIND MOUNT OPERATION |
1523 * |**************************************************************************
1524 * | source-->| shared | private | slave | unbindable |
1528 * |**************************************************************************
1529 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1531 * |non-shared| shared (+) | private | slave (*) | invalid |
1532 * ***************************************************************************
1533 * A bind operation clones the source mount and mounts the clone on the
1534 * destination mount.
1536 * (++) the cloned mount is propagated to all the mounts in the propagation
1537 * tree of the destination mount and the cloned mount is added to
1538 * the peer group of the source mount.
1539 * (+) the cloned mount is created under the destination mount and is marked
1540 * as shared. The cloned mount is added to the peer group of the source
1542 * (+++) the mount is propagated to all the mounts in the propagation tree
1543 * of the destination mount and the cloned mount is made slave
1544 * of the same master as that of the source mount. The cloned mount
1545 * is marked as 'shared and slave'.
1546 * (*) the cloned mount is made a slave of the same master as that of the
1549 * ---------------------------------------------------------------------------
1550 * | MOVE MOUNT OPERATION |
1551 * |**************************************************************************
1552 * | source-->| shared | private | slave | unbindable |
1556 * |**************************************************************************
1557 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1559 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1560 * ***************************************************************************
1562 * (+) the mount is moved to the destination. And is then propagated to
1563 * all the mounts in the propagation tree of the destination mount.
1564 * (+*) the mount is moved to the destination.
1565 * (+++) the mount is moved to the destination and is then propagated to
1566 * all the mounts belonging to the destination mount's propagation tree.
1567 * the mount is marked as 'shared and slave'.
1568 * (*) the mount continues to be a slave at the new location.
1570 * if the source mount is a tree, the operations explained above is
1571 * applied to each mount in the tree.
1572 * Must be called without spinlocks held, since this function can sleep
1575 static int attach_recursive_mnt(struct mount *source_mnt,
1576 struct mount *dest_mnt,
1577 struct mountpoint *dest_mp,
1578 struct path *parent_path)
1580 LIST_HEAD(tree_list);
1581 struct mount *child, *p;
1584 if (IS_MNT_SHARED(dest_mnt)) {
1585 err = invent_group_ids(source_mnt, true);
1589 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
1591 goto out_cleanup_ids;
1593 br_write_lock(&vfsmount_lock);
1595 if (IS_MNT_SHARED(dest_mnt)) {
1596 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1600 detach_mnt(source_mnt, parent_path);
1601 attach_mnt(source_mnt, dest_mnt, dest_mp);
1602 touch_mnt_namespace(source_mnt->mnt_ns);
1604 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
1605 commit_tree(source_mnt);
1608 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
1609 list_del_init(&child->mnt_hash);
1612 br_write_unlock(&vfsmount_lock);
1617 if (IS_MNT_SHARED(dest_mnt))
1618 cleanup_group_ids(source_mnt, NULL);
1623 static struct mountpoint *lock_mount(struct path *path)
1625 struct vfsmount *mnt;
1626 struct dentry *dentry = path->dentry;
1628 mutex_lock(&dentry->d_inode->i_mutex);
1629 if (unlikely(cant_mount(dentry))) {
1630 mutex_unlock(&dentry->d_inode->i_mutex);
1631 return ERR_PTR(-ENOENT);
1634 mnt = lookup_mnt(path);
1636 struct mountpoint *mp = new_mountpoint(dentry);
1639 mutex_unlock(&dentry->d_inode->i_mutex);
1645 mutex_unlock(&path->dentry->d_inode->i_mutex);
1648 dentry = path->dentry = dget(mnt->mnt_root);
1652 static void unlock_mount(struct mountpoint *where)
1654 struct dentry *dentry = where->m_dentry;
1655 put_mountpoint(where);
1657 mutex_unlock(&dentry->d_inode->i_mutex);
1660 static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
1662 if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
1665 if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
1666 S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
1669 return attach_recursive_mnt(mnt, p, mp, NULL);
1673 * Sanity check the flags to change_mnt_propagation.
1676 static int flags_to_propagation_type(int flags)
1678 int type = flags & ~(MS_REC | MS_SILENT);
1680 /* Fail if any non-propagation flags are set */
1681 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1683 /* Only one propagation flag should be set */
1684 if (!is_power_of_2(type))
1690 * recursively change the type of the mountpoint.
1692 static int do_change_type(struct path *path, int flag)
1695 struct mount *mnt = real_mount(path->mnt);
1696 int recurse = flag & MS_REC;
1700 if (path->dentry != path->mnt->mnt_root)
1703 type = flags_to_propagation_type(flag);
1708 if (type == MS_SHARED) {
1709 err = invent_group_ids(mnt, recurse);
1714 br_write_lock(&vfsmount_lock);
1715 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1716 change_mnt_propagation(m, type);
1717 br_write_unlock(&vfsmount_lock);
1724 static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
1726 struct mount *child;
1727 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
1728 if (!is_subdir(child->mnt_mountpoint, dentry))
1731 if (child->mnt.mnt_flags & MNT_LOCKED)
1738 * do loopback mount.
1740 static int do_loopback(struct path *path, const char *old_name,
1743 struct path old_path;
1744 struct mount *mnt = NULL, *old, *parent;
1745 struct mountpoint *mp;
1747 if (!old_name || !*old_name)
1749 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1754 if (mnt_ns_loop(old_path.dentry))
1757 mp = lock_mount(path);
1762 old = real_mount(old_path.mnt);
1763 parent = real_mount(path->mnt);
1766 if (IS_MNT_UNBINDABLE(old))
1769 if (!check_mnt(parent) || !check_mnt(old))
1772 if (!recurse && has_locked_children(old, old_path.dentry))
1776 mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
1778 mnt = clone_mnt(old, old_path.dentry, 0);
1785 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
1787 err = graft_tree(mnt, parent, mp);
1789 br_write_lock(&vfsmount_lock);
1790 umount_tree(mnt, 0);
1791 br_write_unlock(&vfsmount_lock);
1796 path_put(&old_path);
1800 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1803 int readonly_request = 0;
1805 if (ms_flags & MS_RDONLY)
1806 readonly_request = 1;
1807 if (readonly_request == __mnt_is_readonly(mnt))
1810 if (mnt->mnt_flags & MNT_LOCK_READONLY)
1813 if (readonly_request)
1814 error = mnt_make_readonly(real_mount(mnt));
1816 __mnt_unmake_readonly(real_mount(mnt));
1821 * change filesystem flags. dir should be a physical root of filesystem.
1822 * If you've mounted a non-root directory somewhere and want to do remount
1823 * on it - tough luck.
1825 static int do_remount(struct path *path, int flags, int mnt_flags,
1829 struct super_block *sb = path->mnt->mnt_sb;
1830 struct mount *mnt = real_mount(path->mnt);
1832 if (!check_mnt(mnt))
1835 if (path->dentry != path->mnt->mnt_root)
1838 err = security_sb_remount(sb, data);
1842 down_write(&sb->s_umount);
1843 if (flags & MS_BIND)
1844 err = change_mount_flags(path->mnt, flags);
1845 else if (!capable(CAP_SYS_ADMIN))
1848 err = do_remount_sb(sb, flags, data, 0);
1850 br_write_lock(&vfsmount_lock);
1851 mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
1852 mnt->mnt.mnt_flags = mnt_flags;
1853 br_write_unlock(&vfsmount_lock);
1855 up_write(&sb->s_umount);
1857 br_write_lock(&vfsmount_lock);
1858 touch_mnt_namespace(mnt->mnt_ns);
1859 br_write_unlock(&vfsmount_lock);
1864 static inline int tree_contains_unbindable(struct mount *mnt)
1867 for (p = mnt; p; p = next_mnt(p, mnt)) {
1868 if (IS_MNT_UNBINDABLE(p))
1874 static int do_move_mount(struct path *path, const char *old_name)
1876 struct path old_path, parent_path;
1879 struct mountpoint *mp;
1881 if (!old_name || !*old_name)
1883 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1887 mp = lock_mount(path);
1892 old = real_mount(old_path.mnt);
1893 p = real_mount(path->mnt);
1896 if (!check_mnt(p) || !check_mnt(old))
1899 if (old->mnt.mnt_flags & MNT_LOCKED)
1903 if (old_path.dentry != old_path.mnt->mnt_root)
1906 if (!mnt_has_parent(old))
1909 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1910 S_ISDIR(old_path.dentry->d_inode->i_mode))
1913 * Don't move a mount residing in a shared parent.
1915 if (IS_MNT_SHARED(old->mnt_parent))
1918 * Don't move a mount tree containing unbindable mounts to a destination
1919 * mount which is shared.
1921 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
1924 for (; mnt_has_parent(p); p = p->mnt_parent)
1928 err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
1932 /* if the mount is moved, it should no longer be expire
1934 list_del_init(&old->mnt_expire);
1939 path_put(&parent_path);
1940 path_put(&old_path);
1944 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
1947 const char *subtype = strchr(fstype, '.');
1956 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
1958 if (!mnt->mnt_sb->s_subtype)
1964 return ERR_PTR(err);
1968 * add a mount into a namespace's mount tree
1970 static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
1972 struct mountpoint *mp;
1973 struct mount *parent;
1976 mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);
1978 mp = lock_mount(path);
1982 parent = real_mount(path->mnt);
1984 if (unlikely(!check_mnt(parent))) {
1985 /* that's acceptable only for automounts done in private ns */
1986 if (!(mnt_flags & MNT_SHRINKABLE))
1988 /* ... and for those we'd better have mountpoint still alive */
1989 if (!parent->mnt_ns)
1993 /* Refuse the same filesystem on the same mount point */
1995 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
1996 path->mnt->mnt_root == path->dentry)
2000 if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
2003 newmnt->mnt.mnt_flags = mnt_flags;
2004 err = graft_tree(newmnt, parent, mp);
2012 * create a new mount for userspace and request it to be added into the
2015 static int do_new_mount(struct path *path, const char *fstype, int flags,
2016 int mnt_flags, const char *name, void *data)
2018 struct file_system_type *type;
2019 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2020 struct vfsmount *mnt;
2026 type = get_fs_type(fstype);
2030 if (user_ns != &init_user_ns) {
2031 if (!(type->fs_flags & FS_USERNS_MOUNT)) {
2032 put_filesystem(type);
2035 /* Only in special cases allow devices from mounts
2036 * created outside the initial user namespace.
2038 if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
2040 mnt_flags |= MNT_NODEV;
2044 mnt = vfs_kern_mount(type, flags, name, data);
2045 if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
2046 !mnt->mnt_sb->s_subtype)
2047 mnt = fs_set_subtype(mnt, fstype);
2049 put_filesystem(type);
2051 return PTR_ERR(mnt);
2053 err = do_add_mount(real_mount(mnt), path, mnt_flags);
2059 int finish_automount(struct vfsmount *m, struct path *path)
2061 struct mount *mnt = real_mount(m);
2063 /* The new mount record should have at least 2 refs to prevent it being
2064 * expired before we get a chance to add it
2066 BUG_ON(mnt_get_count(mnt) < 2);
2068 if (m->mnt_sb == path->mnt->mnt_sb &&
2069 m->mnt_root == path->dentry) {
2074 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2078 /* remove m from any expiration list it may be on */
2079 if (!list_empty(&mnt->mnt_expire)) {
2081 br_write_lock(&vfsmount_lock);
2082 list_del_init(&mnt->mnt_expire);
2083 br_write_unlock(&vfsmount_lock);
2092 * mnt_set_expiry - Put a mount on an expiration list
2093 * @mnt: The mount to list.
2094 * @expiry_list: The list to add the mount to.
2096 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2099 br_write_lock(&vfsmount_lock);
2101 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2103 br_write_unlock(&vfsmount_lock);
2106 EXPORT_SYMBOL(mnt_set_expiry);
2109 * process a list of expirable mountpoints with the intent of discarding any
2110 * mountpoints that aren't in use and haven't been touched since last we came
2113 void mark_mounts_for_expiry(struct list_head *mounts)
2115 struct mount *mnt, *next;
2116 LIST_HEAD(graveyard);
2118 if (list_empty(mounts))
2122 br_write_lock(&vfsmount_lock);
2124 /* extract from the expiration list every vfsmount that matches the
2125 * following criteria:
2126 * - only referenced by its parent vfsmount
2127 * - still marked for expiry (marked on the last call here; marks are
2128 * cleared by mntput())
2130 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2131 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2132 propagate_mount_busy(mnt, 1))
2134 list_move(&mnt->mnt_expire, &graveyard);
2136 while (!list_empty(&graveyard)) {
2137 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2138 touch_mnt_namespace(mnt->mnt_ns);
2139 umount_tree(mnt, 1);
2141 br_write_unlock(&vfsmount_lock);
2145 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2148 * Ripoff of 'select_parent()'
2150 * search the list of submounts for a given mountpoint, and move any
2151 * shrinkable submounts to the 'graveyard' list.
2153 static int select_submounts(struct mount *parent, struct list_head *graveyard)
2155 struct mount *this_parent = parent;
2156 struct list_head *next;
2160 next = this_parent->mnt_mounts.next;
2162 while (next != &this_parent->mnt_mounts) {
2163 struct list_head *tmp = next;
2164 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2167 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2170 * Descend a level if the d_mounts list is non-empty.
2172 if (!list_empty(&mnt->mnt_mounts)) {
2177 if (!propagate_mount_busy(mnt, 1)) {
2178 list_move_tail(&mnt->mnt_expire, graveyard);
2183 * All done at this level ... ascend and resume the search
2185 if (this_parent != parent) {
2186 next = this_parent->mnt_child.next;
2187 this_parent = this_parent->mnt_parent;
2194 * process a list of expirable mountpoints with the intent of discarding any
2195 * submounts of a specific parent mountpoint
2197 * vfsmount_lock must be held for write
2199 static void shrink_submounts(struct mount *mnt)
2201 LIST_HEAD(graveyard);
2204 /* extract submounts of 'mountpoint' from the expiration list */
2205 while (select_submounts(mnt, &graveyard)) {
2206 while (!list_empty(&graveyard)) {
2207 m = list_first_entry(&graveyard, struct mount,
2209 touch_mnt_namespace(m->mnt_ns);
2216 * Some copy_from_user() implementations do not return the exact number of
2217 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2218 * Note that this function differs from copy_from_user() in that it will oops
2219 * on bad values of `to', rather than returning a short copy.
2221 static long exact_copy_from_user(void *to, const void __user * from,
2225 const char __user *f = from;
2228 if (!access_ok(VERIFY_READ, from, n))
2232 if (__get_user(c, f)) {
2243 int copy_mount_options(const void __user * data, unsigned long *where)
2253 if (!(page = __get_free_page(GFP_KERNEL)))
2256 /* We only care that *some* data at the address the user
2257 * gave us is valid. Just in case, we'll zero
2258 * the remainder of the page.
2260 /* copy_from_user cannot cross TASK_SIZE ! */
2261 size = TASK_SIZE - (unsigned long)data;
2262 if (size > PAGE_SIZE)
2265 i = size - exact_copy_from_user((void *)page, data, size);
2271 memset((char *)page + i, 0, PAGE_SIZE - i);
2276 int copy_mount_string(const void __user *data, char **where)
2285 tmp = strndup_user(data, PAGE_SIZE);
2287 return PTR_ERR(tmp);
2294 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2295 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2297 * data is a (void *) that can point to any structure up to
2298 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2299 * information (or be NULL).
2301 * Pre-0.97 versions of mount() didn't have a flags word.
2302 * When the flags word was introduced its top half was required
2303 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2304 * Therefore, if this magic number is present, it carries no information
2305 * and must be discarded.
2307 long do_mount(const char *dev_name, const char *dir_name,
2308 const char *type_page, unsigned long flags, void *data_page)
2315 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2316 flags &= ~MS_MGC_MSK;
2318 /* Basic sanity checks */
2320 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2324 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2326 /* ... and get the mountpoint */
2327 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2331 retval = security_sb_mount(dev_name, &path,
2332 type_page, flags, data_page);
2333 if (!retval && !may_mount())
2338 /* Default to relatime unless overriden */
2339 if (!(flags & MS_NOATIME))
2340 mnt_flags |= MNT_RELATIME;
2342 /* Separate the per-mountpoint flags */
2343 if (flags & MS_NOSUID)
2344 mnt_flags |= MNT_NOSUID;
2345 if (flags & MS_NODEV)
2346 mnt_flags |= MNT_NODEV;
2347 if (flags & MS_NOEXEC)
2348 mnt_flags |= MNT_NOEXEC;
2349 if (flags & MS_NOATIME)
2350 mnt_flags |= MNT_NOATIME;
2351 if (flags & MS_NODIRATIME)
2352 mnt_flags |= MNT_NODIRATIME;
2353 if (flags & MS_STRICTATIME)
2354 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2355 if (flags & MS_RDONLY)
2356 mnt_flags |= MNT_READONLY;
2358 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2359 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2362 if (flags & MS_REMOUNT)
2363 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2365 else if (flags & MS_BIND)
2366 retval = do_loopback(&path, dev_name, flags & MS_REC);
2367 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2368 retval = do_change_type(&path, flags);
2369 else if (flags & MS_MOVE)
2370 retval = do_move_mount(&path, dev_name);
2372 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2373 dev_name, data_page);
2379 static void free_mnt_ns(struct mnt_namespace *ns)
2381 proc_free_inum(ns->proc_inum);
2382 put_user_ns(ns->user_ns);
2387 * Assign a sequence number so we can detect when we attempt to bind
2388 * mount a reference to an older mount namespace into the current
2389 * mount namespace, preventing reference counting loops. A 64bit
2390 * number incrementing at 10Ghz will take 12,427 years to wrap which
2391 * is effectively never, so we can ignore the possibility.
2393 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
2395 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
2397 struct mnt_namespace *new_ns;
2400 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2402 return ERR_PTR(-ENOMEM);
2403 ret = proc_alloc_inum(&new_ns->proc_inum);
2406 return ERR_PTR(ret);
2408 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
2409 atomic_set(&new_ns->count, 1);
2410 new_ns->root = NULL;
2411 INIT_LIST_HEAD(&new_ns->list);
2412 init_waitqueue_head(&new_ns->poll);
2414 new_ns->user_ns = get_user_ns(user_ns);
2419 * Allocate a new namespace structure and populate it with contents
2420 * copied from the namespace of the passed in task structure.
2422 static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
2423 struct user_namespace *user_ns, struct fs_struct *fs)
2425 struct mnt_namespace *new_ns;
2426 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2427 struct mount *p, *q;
2428 struct mount *old = mnt_ns->root;
2432 new_ns = alloc_mnt_ns(user_ns);
2437 /* First pass: copy the tree topology */
2438 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
2439 if (user_ns != mnt_ns->user_ns)
2440 copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
2441 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
2444 free_mnt_ns(new_ns);
2445 return ERR_CAST(new);
2448 br_write_lock(&vfsmount_lock);
2449 list_add_tail(&new_ns->list, &new->mnt_list);
2450 br_write_unlock(&vfsmount_lock);
2453 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2454 * as belonging to new namespace. We have already acquired a private
2455 * fs_struct, so tsk->fs->lock is not needed.
2462 if (&p->mnt == fs->root.mnt) {
2463 fs->root.mnt = mntget(&q->mnt);
2466 if (&p->mnt == fs->pwd.mnt) {
2467 fs->pwd.mnt = mntget(&q->mnt);
2471 p = next_mnt(p, old);
2472 q = next_mnt(q, new);
2475 while (p->mnt.mnt_root != q->mnt.mnt_root)
2476 p = next_mnt(p, old);
2488 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2489 struct user_namespace *user_ns, struct fs_struct *new_fs)
2491 struct mnt_namespace *new_ns;
2496 if (!(flags & CLONE_NEWNS))
2499 new_ns = dup_mnt_ns(ns, user_ns, new_fs);
2506 * create_mnt_ns - creates a private namespace and adds a root filesystem
2507 * @mnt: pointer to the new root filesystem mountpoint
2509 static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
2511 struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
2512 if (!IS_ERR(new_ns)) {
2513 struct mount *mnt = real_mount(m);
2514 mnt->mnt_ns = new_ns;
2516 list_add(&mnt->mnt_list, &new_ns->list);
2523 struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
2525 struct mnt_namespace *ns;
2526 struct super_block *s;
2530 ns = create_mnt_ns(mnt);
2532 return ERR_CAST(ns);
2534 err = vfs_path_lookup(mnt->mnt_root, mnt,
2535 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
2540 return ERR_PTR(err);
2542 /* trade a vfsmount reference for active sb one */
2543 s = path.mnt->mnt_sb;
2544 atomic_inc(&s->s_active);
2546 /* lock the sucker */
2547 down_write(&s->s_umount);
2548 /* ... and return the root of (sub)tree on it */
2551 EXPORT_SYMBOL(mount_subtree);
2553 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2554 char __user *, type, unsigned long, flags, void __user *, data)
2558 struct filename *kernel_dir;
2560 unsigned long data_page;
2562 ret = copy_mount_string(type, &kernel_type);
2566 kernel_dir = getname(dir_name);
2567 if (IS_ERR(kernel_dir)) {
2568 ret = PTR_ERR(kernel_dir);
2572 ret = copy_mount_string(dev_name, &kernel_dev);
2576 ret = copy_mount_options(data, &data_page);
2580 ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
2581 (void *) data_page);
2583 free_page(data_page);
2587 putname(kernel_dir);
2595 * Return true if path is reachable from root
2597 * namespace_sem or vfsmount_lock is held
2599 bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
2600 const struct path *root)
2602 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
2603 dentry = mnt->mnt_mountpoint;
2604 mnt = mnt->mnt_parent;
2606 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
2609 int path_is_under(struct path *path1, struct path *path2)
2612 br_read_lock(&vfsmount_lock);
2613 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
2614 br_read_unlock(&vfsmount_lock);
2617 EXPORT_SYMBOL(path_is_under);
2620 * pivot_root Semantics:
2621 * Moves the root file system of the current process to the directory put_old,
2622 * makes new_root as the new root file system of the current process, and sets
2623 * root/cwd of all processes which had them on the current root to new_root.
2626 * The new_root and put_old must be directories, and must not be on the
2627 * same file system as the current process root. The put_old must be
2628 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2629 * pointed to by put_old must yield the same directory as new_root. No other
2630 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2632 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2633 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2634 * in this situation.
2637 * - we don't move root/cwd if they are not at the root (reason: if something
2638 * cared enough to change them, it's probably wrong to force them elsewhere)
2639 * - it's okay to pick a root that isn't the root of a file system, e.g.
2640 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2641 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2644 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2645 const char __user *, put_old)
2647 struct path new, old, parent_path, root_parent, root;
2648 struct mount *new_mnt, *root_mnt, *old_mnt;
2649 struct mountpoint *old_mp, *root_mp;
2655 error = user_path_dir(new_root, &new);
2659 error = user_path_dir(put_old, &old);
2663 error = security_sb_pivotroot(&old, &new);
2667 get_fs_root(current->fs, &root);
2668 old_mp = lock_mount(&old);
2669 error = PTR_ERR(old_mp);
2674 new_mnt = real_mount(new.mnt);
2675 root_mnt = real_mount(root.mnt);
2676 old_mnt = real_mount(old.mnt);
2677 if (IS_MNT_SHARED(old_mnt) ||
2678 IS_MNT_SHARED(new_mnt->mnt_parent) ||
2679 IS_MNT_SHARED(root_mnt->mnt_parent))
2681 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
2683 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
2686 if (d_unlinked(new.dentry))
2689 if (new_mnt == root_mnt || old_mnt == root_mnt)
2690 goto out4; /* loop, on the same file system */
2692 if (root.mnt->mnt_root != root.dentry)
2693 goto out4; /* not a mountpoint */
2694 if (!mnt_has_parent(root_mnt))
2695 goto out4; /* not attached */
2696 root_mp = root_mnt->mnt_mp;
2697 if (new.mnt->mnt_root != new.dentry)
2698 goto out4; /* not a mountpoint */
2699 if (!mnt_has_parent(new_mnt))
2700 goto out4; /* not attached */
2701 /* make sure we can reach put_old from new_root */
2702 if (!is_path_reachable(old_mnt, old.dentry, &new))
2704 root_mp->m_count++; /* pin it so it won't go away */
2705 br_write_lock(&vfsmount_lock);
2706 detach_mnt(new_mnt, &parent_path);
2707 detach_mnt(root_mnt, &root_parent);
2708 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
2709 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
2710 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2712 /* mount old root on put_old */
2713 attach_mnt(root_mnt, old_mnt, old_mp);
2714 /* mount new_root on / */
2715 attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
2716 touch_mnt_namespace(current->nsproxy->mnt_ns);
2717 br_write_unlock(&vfsmount_lock);
2718 chroot_fs_refs(&root, &new);
2719 put_mountpoint(root_mp);
2722 unlock_mount(old_mp);
2724 path_put(&root_parent);
2725 path_put(&parent_path);
2737 static void __init init_mount_tree(void)
2739 struct vfsmount *mnt;
2740 struct mnt_namespace *ns;
2742 struct file_system_type *type;
2744 type = get_fs_type("rootfs");
2746 panic("Can't find rootfs type");
2747 mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
2748 put_filesystem(type);
2750 panic("Can't create rootfs");
2752 ns = create_mnt_ns(mnt);
2754 panic("Can't allocate initial namespace");
2756 init_task.nsproxy->mnt_ns = ns;
2760 root.dentry = mnt->mnt_root;
2762 set_fs_pwd(current->fs, &root);
2763 set_fs_root(current->fs, &root);
2766 void __init mnt_init(void)
2771 init_rwsem(&namespace_sem);
2773 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
2774 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2776 mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2777 mountpoint_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
2779 if (!mount_hashtable || !mountpoint_hashtable)
2780 panic("Failed to allocate mount hash table\n");
2782 printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE);
2784 for (u = 0; u < HASH_SIZE; u++)
2785 INIT_LIST_HEAD(&mount_hashtable[u]);
2786 for (u = 0; u < HASH_SIZE; u++)
2787 INIT_LIST_HEAD(&mountpoint_hashtable[u]);
2789 br_lock_init(&vfsmount_lock);
2793 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2795 fs_kobj = kobject_create_and_add("fs", NULL);
2797 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2802 void put_mnt_ns(struct mnt_namespace *ns)
2804 if (!atomic_dec_and_test(&ns->count))
2807 br_write_lock(&vfsmount_lock);
2808 umount_tree(ns->root, 0);
2809 br_write_unlock(&vfsmount_lock);
2814 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2816 struct vfsmount *mnt;
2817 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2820 * it is a longterm mount, don't release mnt until
2821 * we unmount before file sys is unregistered
2823 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
2827 EXPORT_SYMBOL_GPL(kern_mount_data);
2829 void kern_unmount(struct vfsmount *mnt)
2831 /* release long term mount so mount point can be released */
2832 if (!IS_ERR_OR_NULL(mnt)) {
2833 br_write_lock(&vfsmount_lock);
2834 real_mount(mnt)->mnt_ns = NULL;
2835 br_write_unlock(&vfsmount_lock);
2839 EXPORT_SYMBOL(kern_unmount);
2841 bool our_mnt(struct vfsmount *mnt)
2843 return check_mnt(real_mount(mnt));
2846 bool current_chrooted(void)
2848 /* Does the current process have a non-standard root */
2849 struct path ns_root;
2850 struct path fs_root;
2853 /* Find the namespace root */
2854 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
2855 ns_root.dentry = ns_root.mnt->mnt_root;
2857 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
2860 get_fs_root(current->fs, &fs_root);
2862 chrooted = !path_equal(&fs_root, &ns_root);
2870 bool fs_fully_visible(struct file_system_type *type)
2872 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
2874 bool visible = false;
2880 list_for_each_entry(mnt, &ns->list, mnt_list) {
2881 struct mount *child;
2882 if (mnt->mnt.mnt_sb->s_type != type)
2885 /* This mount is not fully visible if there are any child mounts
2886 * that cover anything except for empty directories.
2888 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2889 struct inode *inode = child->mnt_mountpoint->d_inode;
2890 if (!S_ISDIR(inode->i_mode))
2892 if (inode->i_nlink != 2)
2904 static void *mntns_get(struct task_struct *task)
2906 struct mnt_namespace *ns = NULL;
2907 struct nsproxy *nsproxy;
2910 nsproxy = task_nsproxy(task);
2912 ns = nsproxy->mnt_ns;
2920 static void mntns_put(void *ns)
2925 static int mntns_install(struct nsproxy *nsproxy, void *ns)
2927 struct fs_struct *fs = current->fs;
2928 struct mnt_namespace *mnt_ns = ns;
2931 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
2932 !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
2933 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
2940 put_mnt_ns(nsproxy->mnt_ns);
2941 nsproxy->mnt_ns = mnt_ns;
2944 root.mnt = &mnt_ns->root->mnt;
2945 root.dentry = mnt_ns->root->mnt.mnt_root;
2947 while(d_mountpoint(root.dentry) && follow_down_one(&root))
2950 /* Update the pwd and root */
2951 set_fs_pwd(fs, &root);
2952 set_fs_root(fs, &root);
2958 static unsigned int mntns_inum(void *ns)
2960 struct mnt_namespace *mnt_ns = ns;
2961 return mnt_ns->proc_inum;
2964 const struct proc_ns_operations mntns_operations = {
2966 .type = CLONE_NEWNS,
2969 .install = mntns_install,