4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
11 #include <linux/syscalls.h>
12 #include <linux/export.h>
13 #include <linux/capability.h>
14 #include <linux/mnt_namespace.h>
15 #include <linux/user_namespace.h>
16 #include <linux/namei.h>
17 #include <linux/security.h>
18 #include <linux/idr.h>
19 #include <linux/init.h> /* init_rootfs */
20 #include <linux/fs_struct.h> /* get_fs_root et.al. */
21 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
22 #include <linux/uaccess.h>
23 #include <linux/proc_ns.h>
24 #include <linux/magic.h>
25 #include <linux/bootmem.h>
29 static unsigned int m_hash_mask __read_mostly;
30 static unsigned int m_hash_shift __read_mostly;
31 static unsigned int mp_hash_mask __read_mostly;
32 static unsigned int mp_hash_shift __read_mostly;
34 static __initdata unsigned long mhash_entries;
35 static int __init set_mhash_entries(char *str)
39 mhash_entries = simple_strtoul(str, &str, 0);
42 __setup("mhash_entries=", set_mhash_entries);
44 static __initdata unsigned long mphash_entries;
45 static int __init set_mphash_entries(char *str)
49 mphash_entries = simple_strtoul(str, &str, 0);
52 __setup("mphash_entries=", set_mphash_entries);
55 static DEFINE_IDA(mnt_id_ida);
56 static DEFINE_IDA(mnt_group_ida);
57 static DEFINE_SPINLOCK(mnt_id_lock);
58 static int mnt_id_start = 0;
59 static int mnt_group_start = 1;
61 static struct hlist_head *mount_hashtable __read_mostly;
62 static struct hlist_head *mountpoint_hashtable __read_mostly;
63 static struct kmem_cache *mnt_cache __read_mostly;
64 static DECLARE_RWSEM(namespace_sem);
67 struct kobject *fs_kobj;
68 EXPORT_SYMBOL_GPL(fs_kobj);
71 * vfsmount lock may be taken for read to prevent changes to the
72 * vfsmount hash, ie. during mountpoint lookups or walking back
75 * It should be taken for write in all cases where the vfsmount
76 * tree or hash is modified or when a vfsmount structure is modified.
78 __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
80 static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
82 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
83 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
84 tmp = tmp + (tmp >> m_hash_shift);
85 return &mount_hashtable[tmp & m_hash_mask];
88 static inline struct hlist_head *mp_hash(struct dentry *dentry)
90 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
91 tmp = tmp + (tmp >> mp_hash_shift);
92 return &mountpoint_hashtable[tmp & mp_hash_mask];
96 * allocation is serialized by namespace_sem, but we need the spinlock to
97 * serialize with freeing.
99 static int mnt_alloc_id(struct mount *mnt)
104 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
105 spin_lock(&mnt_id_lock);
106 res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
108 mnt_id_start = mnt->mnt_id + 1;
109 spin_unlock(&mnt_id_lock);
116 static void mnt_free_id(struct mount *mnt)
118 int id = mnt->mnt_id;
119 spin_lock(&mnt_id_lock);
120 ida_remove(&mnt_id_ida, id);
121 if (mnt_id_start > id)
123 spin_unlock(&mnt_id_lock);
127 * Allocate a new peer group ID
129 * mnt_group_ida is protected by namespace_sem
131 static int mnt_alloc_group_id(struct mount *mnt)
135 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
138 res = ida_get_new_above(&mnt_group_ida,
142 mnt_group_start = mnt->mnt_group_id + 1;
148 * Release a peer group ID
150 void mnt_release_group_id(struct mount *mnt)
152 int id = mnt->mnt_group_id;
153 ida_remove(&mnt_group_ida, id);
154 if (mnt_group_start > id)
155 mnt_group_start = id;
156 mnt->mnt_group_id = 0;
160 * vfsmount lock must be held for read
162 static inline void mnt_add_count(struct mount *mnt, int n)
165 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
174 * vfsmount lock must be held for write
176 unsigned int mnt_get_count(struct mount *mnt)
179 unsigned int count = 0;
182 for_each_possible_cpu(cpu) {
183 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
188 return mnt->mnt_count;
192 static struct mount *alloc_vfsmnt(const char *name)
194 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
198 err = mnt_alloc_id(mnt);
203 mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
204 if (!mnt->mnt_devname)
209 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
211 goto out_free_devname;
213 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
216 mnt->mnt_writers = 0;
219 INIT_HLIST_NODE(&mnt->mnt_hash);
220 INIT_LIST_HEAD(&mnt->mnt_child);
221 INIT_LIST_HEAD(&mnt->mnt_mounts);
222 INIT_LIST_HEAD(&mnt->mnt_list);
223 INIT_LIST_HEAD(&mnt->mnt_expire);
224 INIT_LIST_HEAD(&mnt->mnt_share);
225 INIT_LIST_HEAD(&mnt->mnt_slave_list);
226 INIT_LIST_HEAD(&mnt->mnt_slave);
227 #ifdef CONFIG_FSNOTIFY
228 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
235 kfree(mnt->mnt_devname);
240 kmem_cache_free(mnt_cache, mnt);
245 * Most r/o checks on a fs are for operations that take
246 * discrete amounts of time, like a write() or unlink().
247 * We must keep track of when those operations start
248 * (for permission checks) and when they end, so that
249 * we can determine when writes are able to occur to
253 * __mnt_is_readonly: check whether a mount is read-only
254 * @mnt: the mount to check for its write status
256 * This shouldn't be used directly ouside of the VFS.
257 * It does not guarantee that the filesystem will stay
258 * r/w, just that it is right *now*. This can not and
259 * should not be used in place of IS_RDONLY(inode).
260 * mnt_want/drop_write() will _keep_ the filesystem
263 int __mnt_is_readonly(struct vfsmount *mnt)
265 if (mnt->mnt_flags & MNT_READONLY)
267 if (mnt->mnt_sb->s_flags & MS_RDONLY)
271 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
273 static inline void mnt_inc_writers(struct mount *mnt)
276 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
282 static inline void mnt_dec_writers(struct mount *mnt)
285 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
291 static unsigned int mnt_get_writers(struct mount *mnt)
294 unsigned int count = 0;
297 for_each_possible_cpu(cpu) {
298 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
303 return mnt->mnt_writers;
307 static int mnt_is_readonly(struct vfsmount *mnt)
309 if (mnt->mnt_sb->s_readonly_remount)
311 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
313 return __mnt_is_readonly(mnt);
317 * Most r/o & frozen checks on a fs are for operations that take discrete
318 * amounts of time, like a write() or unlink(). We must keep track of when
319 * those operations start (for permission checks) and when they end, so that we
320 * can determine when writes are able to occur to a filesystem.
323 * __mnt_want_write - get write access to a mount without freeze protection
324 * @m: the mount on which to take a write
326 * This tells the low-level filesystem that a write is about to be performed to
327 * it, and makes sure that writes are allowed (mnt it read-write) before
328 * returning success. This operation does not protect against filesystem being
329 * frozen. When the write operation is finished, __mnt_drop_write() must be
330 * called. This is effectively a refcount.
332 int __mnt_want_write(struct vfsmount *m)
334 struct mount *mnt = real_mount(m);
338 mnt_inc_writers(mnt);
340 * The store to mnt_inc_writers must be visible before we pass
341 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
342 * incremented count after it has set MNT_WRITE_HOLD.
345 while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
348 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
349 * be set to match its requirements. So we must not load that until
350 * MNT_WRITE_HOLD is cleared.
353 if (mnt_is_readonly(m)) {
354 mnt_dec_writers(mnt);
363 * mnt_want_write - get write access to a mount
364 * @m: the mount on which to take a write
366 * This tells the low-level filesystem that a write is about to be performed to
367 * it, and makes sure that writes are allowed (mount is read-write, filesystem
368 * is not frozen) before returning success. When the write operation is
369 * finished, mnt_drop_write() must be called. This is effectively a refcount.
371 int mnt_want_write(struct vfsmount *m)
375 sb_start_write(m->mnt_sb);
376 ret = __mnt_want_write(m);
378 sb_end_write(m->mnt_sb);
381 EXPORT_SYMBOL_GPL(mnt_want_write);
384 * mnt_clone_write - get write access to a mount
385 * @mnt: the mount on which to take a write
387 * This is effectively like mnt_want_write, except
388 * it must only be used to take an extra write reference
389 * on a mountpoint that we already know has a write reference
390 * on it. This allows some optimisation.
392 * After finished, mnt_drop_write must be called as usual to
393 * drop the reference.
395 int mnt_clone_write(struct vfsmount *mnt)
397 /* superblock may be r/o */
398 if (__mnt_is_readonly(mnt))
401 mnt_inc_writers(real_mount(mnt));
405 EXPORT_SYMBOL_GPL(mnt_clone_write);
408 * __mnt_want_write_file - get write access to a file's mount
409 * @file: the file who's mount on which to take a write
411 * This is like __mnt_want_write, but it takes a file and can
412 * do some optimisations if the file is open for write already
414 int __mnt_want_write_file(struct file *file)
416 if (!(file->f_mode & FMODE_WRITER))
417 return __mnt_want_write(file->f_path.mnt);
419 return mnt_clone_write(file->f_path.mnt);
423 * mnt_want_write_file - get write access to a file's mount
424 * @file: the file who's mount on which to take a write
426 * This is like mnt_want_write, but it takes a file and can
427 * do some optimisations if the file is open for write already
429 int mnt_want_write_file(struct file *file)
433 sb_start_write(file->f_path.mnt->mnt_sb);
434 ret = __mnt_want_write_file(file);
436 sb_end_write(file->f_path.mnt->mnt_sb);
439 EXPORT_SYMBOL_GPL(mnt_want_write_file);
442 * __mnt_drop_write - give up write access to a mount
443 * @mnt: the mount on which to give up write access
445 * Tells the low-level filesystem that we are done
446 * performing writes to it. Must be matched with
447 * __mnt_want_write() call above.
449 void __mnt_drop_write(struct vfsmount *mnt)
452 mnt_dec_writers(real_mount(mnt));
457 * mnt_drop_write - give up write access to a mount
458 * @mnt: the mount on which to give up write access
460 * Tells the low-level filesystem that we are done performing writes to it and
461 * also allows filesystem to be frozen again. Must be matched with
462 * mnt_want_write() call above.
464 void mnt_drop_write(struct vfsmount *mnt)
466 __mnt_drop_write(mnt);
467 sb_end_write(mnt->mnt_sb);
469 EXPORT_SYMBOL_GPL(mnt_drop_write);
471 void __mnt_drop_write_file(struct file *file)
473 __mnt_drop_write(file->f_path.mnt);
476 void mnt_drop_write_file(struct file *file)
478 mnt_drop_write(file->f_path.mnt);
480 EXPORT_SYMBOL(mnt_drop_write_file);
482 static int mnt_make_readonly(struct mount *mnt)
487 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
489 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
490 * should be visible before we do.
495 * With writers on hold, if this value is zero, then there are
496 * definitely no active writers (although held writers may subsequently
497 * increment the count, they'll have to wait, and decrement it after
498 * seeing MNT_READONLY).
500 * It is OK to have counter incremented on one CPU and decremented on
501 * another: the sum will add up correctly. The danger would be when we
502 * sum up each counter, if we read a counter before it is incremented,
503 * but then read another CPU's count which it has been subsequently
504 * decremented from -- we would see more decrements than we should.
505 * MNT_WRITE_HOLD protects against this scenario, because
506 * mnt_want_write first increments count, then smp_mb, then spins on
507 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
508 * we're counting up here.
510 if (mnt_get_writers(mnt) > 0)
513 mnt->mnt.mnt_flags |= MNT_READONLY;
515 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
516 * that become unheld will see MNT_READONLY.
519 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
524 static void __mnt_unmake_readonly(struct mount *mnt)
527 mnt->mnt.mnt_flags &= ~MNT_READONLY;
531 int sb_prepare_remount_readonly(struct super_block *sb)
536 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
537 if (atomic_long_read(&sb->s_remove_count))
541 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
542 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
543 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
545 if (mnt_get_writers(mnt) > 0) {
551 if (!err && atomic_long_read(&sb->s_remove_count))
555 sb->s_readonly_remount = 1;
558 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
559 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
560 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
567 static void free_vfsmnt(struct mount *mnt)
569 kfree(mnt->mnt_devname);
571 free_percpu(mnt->mnt_pcp);
573 kmem_cache_free(mnt_cache, mnt);
576 static void delayed_free_vfsmnt(struct rcu_head *head)
578 free_vfsmnt(container_of(head, struct mount, mnt_rcu));
581 /* call under rcu_read_lock */
582 bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
585 if (read_seqretry(&mount_lock, seq))
589 mnt = real_mount(bastard);
590 mnt_add_count(mnt, 1);
591 if (likely(!read_seqretry(&mount_lock, seq)))
593 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
594 mnt_add_count(mnt, -1);
604 * find the first mount at @dentry on vfsmount @mnt.
605 * call under rcu_read_lock()
607 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
609 struct hlist_head *head = m_hash(mnt, dentry);
612 hlist_for_each_entry_rcu(p, head, mnt_hash)
613 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
619 * find the last mount at @dentry on vfsmount @mnt.
620 * mount_lock must be held.
622 struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)
624 struct mount *p, *res;
625 res = p = __lookup_mnt(mnt, dentry);
628 hlist_for_each_entry_continue(p, mnt_hash) {
629 if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry)
638 * lookup_mnt - Return the first child mount mounted at path
640 * "First" means first mounted chronologically. If you create the
643 * mount /dev/sda1 /mnt
644 * mount /dev/sda2 /mnt
645 * mount /dev/sda3 /mnt
647 * Then lookup_mnt() on the base /mnt dentry in the root mount will
648 * return successively the root dentry and vfsmount of /dev/sda1, then
649 * /dev/sda2, then /dev/sda3, then NULL.
651 * lookup_mnt takes a reference to the found vfsmount.
653 struct vfsmount *lookup_mnt(struct path *path)
655 struct mount *child_mnt;
661 seq = read_seqbegin(&mount_lock);
662 child_mnt = __lookup_mnt(path->mnt, path->dentry);
663 m = child_mnt ? &child_mnt->mnt : NULL;
664 } while (!legitimize_mnt(m, seq));
669 static struct mountpoint *new_mountpoint(struct dentry *dentry)
671 struct hlist_head *chain = mp_hash(dentry);
672 struct mountpoint *mp;
675 hlist_for_each_entry(mp, chain, m_hash) {
676 if (mp->m_dentry == dentry) {
677 /* might be worth a WARN_ON() */
678 if (d_unlinked(dentry))
679 return ERR_PTR(-ENOENT);
685 mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
687 return ERR_PTR(-ENOMEM);
689 ret = d_set_mounted(dentry);
695 mp->m_dentry = dentry;
697 hlist_add_head(&mp->m_hash, chain);
701 static void put_mountpoint(struct mountpoint *mp)
703 if (!--mp->m_count) {
704 struct dentry *dentry = mp->m_dentry;
705 spin_lock(&dentry->d_lock);
706 dentry->d_flags &= ~DCACHE_MOUNTED;
707 spin_unlock(&dentry->d_lock);
708 hlist_del(&mp->m_hash);
713 static inline int check_mnt(struct mount *mnt)
715 return mnt->mnt_ns == current->nsproxy->mnt_ns;
719 * vfsmount lock must be held for write
721 static void touch_mnt_namespace(struct mnt_namespace *ns)
725 wake_up_interruptible(&ns->poll);
730 * vfsmount lock must be held for write
732 static void __touch_mnt_namespace(struct mnt_namespace *ns)
734 if (ns && ns->event != event) {
736 wake_up_interruptible(&ns->poll);
741 * vfsmount lock must be held for write
743 static void detach_mnt(struct mount *mnt, struct path *old_path)
745 old_path->dentry = mnt->mnt_mountpoint;
746 old_path->mnt = &mnt->mnt_parent->mnt;
747 mnt->mnt_parent = mnt;
748 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
749 list_del_init(&mnt->mnt_child);
750 hlist_del_init_rcu(&mnt->mnt_hash);
751 put_mountpoint(mnt->mnt_mp);
756 * vfsmount lock must be held for write
758 void mnt_set_mountpoint(struct mount *mnt,
759 struct mountpoint *mp,
760 struct mount *child_mnt)
763 mnt_add_count(mnt, 1); /* essentially, that's mntget */
764 child_mnt->mnt_mountpoint = dget(mp->m_dentry);
765 child_mnt->mnt_parent = mnt;
766 child_mnt->mnt_mp = mp;
770 * vfsmount lock must be held for write
772 static void attach_mnt(struct mount *mnt,
773 struct mount *parent,
774 struct mountpoint *mp)
776 mnt_set_mountpoint(parent, mp, mnt);
777 hlist_add_head_rcu(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
778 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
782 * vfsmount lock must be held for write
784 static void commit_tree(struct mount *mnt, struct mount *shadows)
786 struct mount *parent = mnt->mnt_parent;
789 struct mnt_namespace *n = parent->mnt_ns;
791 BUG_ON(parent == mnt);
793 list_add_tail(&head, &mnt->mnt_list);
794 list_for_each_entry(m, &head, mnt_list)
797 list_splice(&head, n->list.prev);
800 hlist_add_after_rcu(&shadows->mnt_hash, &mnt->mnt_hash);
802 hlist_add_head_rcu(&mnt->mnt_hash,
803 m_hash(&parent->mnt, mnt->mnt_mountpoint));
804 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
805 touch_mnt_namespace(n);
808 static struct mount *next_mnt(struct mount *p, struct mount *root)
810 struct list_head *next = p->mnt_mounts.next;
811 if (next == &p->mnt_mounts) {
815 next = p->mnt_child.next;
816 if (next != &p->mnt_parent->mnt_mounts)
821 return list_entry(next, struct mount, mnt_child);
824 static struct mount *skip_mnt_tree(struct mount *p)
826 struct list_head *prev = p->mnt_mounts.prev;
827 while (prev != &p->mnt_mounts) {
828 p = list_entry(prev, struct mount, mnt_child);
829 prev = p->mnt_mounts.prev;
835 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
841 return ERR_PTR(-ENODEV);
843 mnt = alloc_vfsmnt(name);
845 return ERR_PTR(-ENOMEM);
847 if (flags & MS_KERNMOUNT)
848 mnt->mnt.mnt_flags = MNT_INTERNAL;
850 root = mount_fs(type, flags, name, data);
854 return ERR_CAST(root);
857 mnt->mnt.mnt_root = root;
858 mnt->mnt.mnt_sb = root->d_sb;
859 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
860 mnt->mnt_parent = mnt;
862 list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
866 EXPORT_SYMBOL_GPL(vfs_kern_mount);
868 static struct mount *clone_mnt(struct mount *old, struct dentry *root,
871 struct super_block *sb = old->mnt.mnt_sb;
875 mnt = alloc_vfsmnt(old->mnt_devname);
877 return ERR_PTR(-ENOMEM);
879 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
880 mnt->mnt_group_id = 0; /* not a peer of original */
882 mnt->mnt_group_id = old->mnt_group_id;
884 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
885 err = mnt_alloc_group_id(mnt);
890 mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~(MNT_WRITE_HOLD|MNT_MARKED);
891 /* Don't allow unprivileged users to change mount flags */
892 if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
893 mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
895 /* Don't allow unprivileged users to reveal what is under a mount */
896 if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
897 mnt->mnt.mnt_flags |= MNT_LOCKED;
899 atomic_inc(&sb->s_active);
900 mnt->mnt.mnt_sb = sb;
901 mnt->mnt.mnt_root = dget(root);
902 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
903 mnt->mnt_parent = mnt;
905 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
908 if ((flag & CL_SLAVE) ||
909 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
910 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
911 mnt->mnt_master = old;
912 CLEAR_MNT_SHARED(mnt);
913 } else if (!(flag & CL_PRIVATE)) {
914 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
915 list_add(&mnt->mnt_share, &old->mnt_share);
916 if (IS_MNT_SLAVE(old))
917 list_add(&mnt->mnt_slave, &old->mnt_slave);
918 mnt->mnt_master = old->mnt_master;
920 if (flag & CL_MAKE_SHARED)
923 /* stick the duplicate mount on the same expiry list
924 * as the original if that was on one */
925 if (flag & CL_EXPIRE) {
926 if (!list_empty(&old->mnt_expire))
927 list_add(&mnt->mnt_expire, &old->mnt_expire);
938 static void mntput_no_expire(struct mount *mnt)
941 mnt_add_count(mnt, -1);
942 if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */
947 if (mnt_get_count(mnt)) {
952 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
957 mnt->mnt.mnt_flags |= MNT_DOOMED;
960 list_del(&mnt->mnt_instance);
964 * This probably indicates that somebody messed
965 * up a mnt_want/drop_write() pair. If this
966 * happens, the filesystem was probably unable
967 * to make r/w->r/o transitions.
970 * The locking used to deal with mnt_count decrement provides barriers,
971 * so mnt_get_writers() below is safe.
973 WARN_ON(mnt_get_writers(mnt));
974 if (unlikely(mnt->mnt_pins.first))
976 fsnotify_vfsmount_delete(&mnt->mnt);
977 dput(mnt->mnt.mnt_root);
978 deactivate_super(mnt->mnt.mnt_sb);
980 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
983 void mntput(struct vfsmount *mnt)
986 struct mount *m = real_mount(mnt);
987 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
988 if (unlikely(m->mnt_expiry_mark))
989 m->mnt_expiry_mark = 0;
993 EXPORT_SYMBOL(mntput);
995 struct vfsmount *mntget(struct vfsmount *mnt)
998 mnt_add_count(real_mount(mnt), 1);
1001 EXPORT_SYMBOL(mntget);
1003 struct vfsmount *mnt_clone_internal(struct path *path)
1006 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
1009 p->mnt.mnt_flags |= MNT_INTERNAL;
1013 static inline void mangle(struct seq_file *m, const char *s)
1015 seq_escape(m, s, " \t\n\\");
1019 * Simple .show_options callback for filesystems which don't want to
1020 * implement more complex mount option showing.
1022 * See also save_mount_options().
1024 int generic_show_options(struct seq_file *m, struct dentry *root)
1026 const char *options;
1029 options = rcu_dereference(root->d_sb->s_options);
1031 if (options != NULL && options[0]) {
1039 EXPORT_SYMBOL(generic_show_options);
1042 * If filesystem uses generic_show_options(), this function should be
1043 * called from the fill_super() callback.
1045 * The .remount_fs callback usually needs to be handled in a special
1046 * way, to make sure, that previous options are not overwritten if the
1049 * Also note, that if the filesystem's .remount_fs function doesn't
1050 * reset all options to their default value, but changes only newly
1051 * given options, then the displayed options will not reflect reality
1054 void save_mount_options(struct super_block *sb, char *options)
1056 BUG_ON(sb->s_options);
1057 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
1059 EXPORT_SYMBOL(save_mount_options);
1061 void replace_mount_options(struct super_block *sb, char *options)
1063 char *old = sb->s_options;
1064 rcu_assign_pointer(sb->s_options, options);
1070 EXPORT_SYMBOL(replace_mount_options);
1072 #ifdef CONFIG_PROC_FS
1073 /* iterator; we want it to have access to namespace_sem, thus here... */
1074 static void *m_start(struct seq_file *m, loff_t *pos)
1076 struct proc_mounts *p = proc_mounts(m);
1078 down_read(&namespace_sem);
1079 if (p->cached_event == p->ns->event) {
1080 void *v = p->cached_mount;
1081 if (*pos == p->cached_index)
1083 if (*pos == p->cached_index + 1) {
1084 v = seq_list_next(v, &p->ns->list, &p->cached_index);
1085 return p->cached_mount = v;
1089 p->cached_event = p->ns->event;
1090 p->cached_mount = seq_list_start(&p->ns->list, *pos);
1091 p->cached_index = *pos;
1092 return p->cached_mount;
1095 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1097 struct proc_mounts *p = proc_mounts(m);
1099 p->cached_mount = seq_list_next(v, &p->ns->list, pos);
1100 p->cached_index = *pos;
1101 return p->cached_mount;
1104 static void m_stop(struct seq_file *m, void *v)
1106 up_read(&namespace_sem);
1109 static int m_show(struct seq_file *m, void *v)
1111 struct proc_mounts *p = proc_mounts(m);
1112 struct mount *r = list_entry(v, struct mount, mnt_list);
1113 return p->show(m, &r->mnt);
1116 const struct seq_operations mounts_op = {
1122 #endif /* CONFIG_PROC_FS */
1125 * may_umount_tree - check if a mount tree is busy
1126 * @mnt: root of mount tree
1128 * This is called to check if a tree of mounts has any
1129 * open files, pwds, chroots or sub mounts that are
1132 int may_umount_tree(struct vfsmount *m)
1134 struct mount *mnt = real_mount(m);
1135 int actual_refs = 0;
1136 int minimum_refs = 0;
1140 /* write lock needed for mnt_get_count */
1142 for (p = mnt; p; p = next_mnt(p, mnt)) {
1143 actual_refs += mnt_get_count(p);
1146 unlock_mount_hash();
1148 if (actual_refs > minimum_refs)
1154 EXPORT_SYMBOL(may_umount_tree);
1157 * may_umount - check if a mount point is busy
1158 * @mnt: root of mount
1160 * This is called to check if a mount point has any
1161 * open files, pwds, chroots or sub mounts. If the
1162 * mount has sub mounts this will return busy
1163 * regardless of whether the sub mounts are busy.
1165 * Doesn't take quota and stuff into account. IOW, in some cases it will
1166 * give false negatives. The main reason why it's here is that we need
1167 * a non-destructive way to look for easily umountable filesystems.
1169 int may_umount(struct vfsmount *mnt)
1172 down_read(&namespace_sem);
1174 if (propagate_mount_busy(real_mount(mnt), 2))
1176 unlock_mount_hash();
1177 up_read(&namespace_sem);
1181 EXPORT_SYMBOL(may_umount);
1183 static HLIST_HEAD(unmounted); /* protected by namespace_sem */
1185 static void namespace_unlock(void)
1188 struct hlist_head head = unmounted;
1190 if (likely(hlist_empty(&head))) {
1191 up_write(&namespace_sem);
1195 head.first->pprev = &head.first;
1196 INIT_HLIST_HEAD(&unmounted);
1198 up_write(&namespace_sem);
1202 while (!hlist_empty(&head)) {
1203 mnt = hlist_entry(head.first, struct mount, mnt_hash);
1204 hlist_del_init(&mnt->mnt_hash);
1205 if (mnt->mnt_ex_mountpoint.mnt)
1206 path_put(&mnt->mnt_ex_mountpoint);
1211 static inline void namespace_lock(void)
1213 down_write(&namespace_sem);
1217 * mount_lock must be held
1218 * namespace_sem must be held for write
1219 * how = 0 => just this tree, don't propagate
1220 * how = 1 => propagate; we know that nobody else has reference to any victims
1221 * how = 2 => lazy umount
1223 void umount_tree(struct mount *mnt, int how)
1225 HLIST_HEAD(tmp_list);
1227 struct mount *last = NULL;
1229 for (p = mnt; p; p = next_mnt(p, mnt)) {
1230 hlist_del_init_rcu(&p->mnt_hash);
1231 hlist_add_head(&p->mnt_hash, &tmp_list);
1235 propagate_umount(&tmp_list);
1237 hlist_for_each_entry(p, &tmp_list, mnt_hash) {
1238 list_del_init(&p->mnt_expire);
1239 list_del_init(&p->mnt_list);
1240 __touch_mnt_namespace(p->mnt_ns);
1243 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1244 list_del_init(&p->mnt_child);
1245 if (mnt_has_parent(p)) {
1246 put_mountpoint(p->mnt_mp);
1247 /* move the reference to mountpoint into ->mnt_ex_mountpoint */
1248 p->mnt_ex_mountpoint.dentry = p->mnt_mountpoint;
1249 p->mnt_ex_mountpoint.mnt = &p->mnt_parent->mnt;
1250 p->mnt_mountpoint = p->mnt.mnt_root;
1254 change_mnt_propagation(p, MS_PRIVATE);
1258 last->mnt_hash.next = unmounted.first;
1259 unmounted.first = tmp_list.first;
1260 unmounted.first->pprev = &unmounted.first;
1264 static void shrink_submounts(struct mount *mnt);
1266 static int do_umount(struct mount *mnt, int flags)
1268 struct super_block *sb = mnt->mnt.mnt_sb;
1271 retval = security_sb_umount(&mnt->mnt, flags);
1276 * Allow userspace to request a mountpoint be expired rather than
1277 * unmounting unconditionally. Unmount only happens if:
1278 * (1) the mark is already set (the mark is cleared by mntput())
1279 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1281 if (flags & MNT_EXPIRE) {
1282 if (&mnt->mnt == current->fs->root.mnt ||
1283 flags & (MNT_FORCE | MNT_DETACH))
1287 * probably don't strictly need the lock here if we examined
1288 * all race cases, but it's a slowpath.
1291 if (mnt_get_count(mnt) != 2) {
1292 unlock_mount_hash();
1295 unlock_mount_hash();
1297 if (!xchg(&mnt->mnt_expiry_mark, 1))
1302 * If we may have to abort operations to get out of this
1303 * mount, and they will themselves hold resources we must
1304 * allow the fs to do things. In the Unix tradition of
1305 * 'Gee thats tricky lets do it in userspace' the umount_begin
1306 * might fail to complete on the first run through as other tasks
1307 * must return, and the like. Thats for the mount program to worry
1308 * about for the moment.
1311 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1312 sb->s_op->umount_begin(sb);
1316 * No sense to grab the lock for this test, but test itself looks
1317 * somewhat bogus. Suggestions for better replacement?
1318 * Ho-hum... In principle, we might treat that as umount + switch
1319 * to rootfs. GC would eventually take care of the old vfsmount.
1320 * Actually it makes sense, especially if rootfs would contain a
1321 * /reboot - static binary that would close all descriptors and
1322 * call reboot(9). Then init(8) could umount root and exec /reboot.
1324 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1326 * Special case for "unmounting" root ...
1327 * we just try to remount it readonly.
1329 down_write(&sb->s_umount);
1330 if (!(sb->s_flags & MS_RDONLY))
1331 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1332 up_write(&sb->s_umount);
1340 if (flags & MNT_DETACH) {
1341 if (!list_empty(&mnt->mnt_list))
1342 umount_tree(mnt, 2);
1345 shrink_submounts(mnt);
1347 if (!propagate_mount_busy(mnt, 2)) {
1348 if (!list_empty(&mnt->mnt_list))
1349 umount_tree(mnt, 1);
1353 unlock_mount_hash();
1359 * Is the caller allowed to modify his namespace?
1361 static inline bool may_mount(void)
1363 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1367 * Now umount can handle mount points as well as block devices.
1368 * This is important for filesystems which use unnamed block devices.
1370 * We now support a flag for forced unmount like the other 'big iron'
1371 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1374 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1379 int lookup_flags = 0;
1381 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1387 if (!(flags & UMOUNT_NOFOLLOW))
1388 lookup_flags |= LOOKUP_FOLLOW;
1390 retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
1393 mnt = real_mount(path.mnt);
1395 if (path.dentry != path.mnt->mnt_root)
1397 if (!check_mnt(mnt))
1399 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1402 retval = do_umount(mnt, flags);
1404 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1406 mntput_no_expire(mnt);
1411 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1414 * The 2.0 compatible umount. No flags.
1416 SYSCALL_DEFINE1(oldumount, char __user *, name)
1418 return sys_umount(name, 0);
1423 static bool is_mnt_ns_file(struct dentry *dentry)
1425 /* Is this a proxy for a mount namespace? */
1426 struct inode *inode = dentry->d_inode;
1429 if (!proc_ns_inode(inode))
1432 ei = get_proc_ns(inode);
1433 if (ei->ns_ops != &mntns_operations)
1439 static bool mnt_ns_loop(struct dentry *dentry)
1441 /* Could bind mounting the mount namespace inode cause a
1442 * mount namespace loop?
1444 struct mnt_namespace *mnt_ns;
1445 if (!is_mnt_ns_file(dentry))
1448 mnt_ns = get_proc_ns(dentry->d_inode)->ns;
1449 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1452 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1455 struct mount *res, *p, *q, *r, *parent;
1457 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1458 return ERR_PTR(-EINVAL);
1460 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1461 return ERR_PTR(-EINVAL);
1463 res = q = clone_mnt(mnt, dentry, flag);
1467 q->mnt.mnt_flags &= ~MNT_LOCKED;
1468 q->mnt_mountpoint = mnt->mnt_mountpoint;
1471 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1473 if (!is_subdir(r->mnt_mountpoint, dentry))
1476 for (s = r; s; s = next_mnt(s, r)) {
1477 if (!(flag & CL_COPY_UNBINDABLE) &&
1478 IS_MNT_UNBINDABLE(s)) {
1479 s = skip_mnt_tree(s);
1482 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1483 is_mnt_ns_file(s->mnt.mnt_root)) {
1484 s = skip_mnt_tree(s);
1487 while (p != s->mnt_parent) {
1493 q = clone_mnt(p, p->mnt.mnt_root, flag);
1497 list_add_tail(&q->mnt_list, &res->mnt_list);
1498 attach_mnt(q, parent, p->mnt_mp);
1499 unlock_mount_hash();
1506 umount_tree(res, 0);
1507 unlock_mount_hash();
1512 /* Caller should check returned pointer for errors */
1514 struct vfsmount *collect_mounts(struct path *path)
1518 tree = copy_tree(real_mount(path->mnt), path->dentry,
1519 CL_COPY_ALL | CL_PRIVATE);
1522 return ERR_CAST(tree);
1526 void drop_collected_mounts(struct vfsmount *mnt)
1530 umount_tree(real_mount(mnt), 0);
1531 unlock_mount_hash();
1535 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1536 struct vfsmount *root)
1539 int res = f(root, arg);
1542 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1543 res = f(&mnt->mnt, arg);
1550 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1554 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1555 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1556 mnt_release_group_id(p);
1560 static int invent_group_ids(struct mount *mnt, bool recurse)
1564 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1565 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1566 int err = mnt_alloc_group_id(p);
1568 cleanup_group_ids(mnt, p);
1578 * @source_mnt : mount tree to be attached
1579 * @nd : place the mount tree @source_mnt is attached
1580 * @parent_nd : if non-null, detach the source_mnt from its parent and
1581 * store the parent mount and mountpoint dentry.
1582 * (done when source_mnt is moved)
1584 * NOTE: in the table below explains the semantics when a source mount
1585 * of a given type is attached to a destination mount of a given type.
1586 * ---------------------------------------------------------------------------
1587 * | BIND MOUNT OPERATION |
1588 * |**************************************************************************
1589 * | source-->| shared | private | slave | unbindable |
1593 * |**************************************************************************
1594 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1596 * |non-shared| shared (+) | private | slave (*) | invalid |
1597 * ***************************************************************************
1598 * A bind operation clones the source mount and mounts the clone on the
1599 * destination mount.
1601 * (++) the cloned mount is propagated to all the mounts in the propagation
1602 * tree of the destination mount and the cloned mount is added to
1603 * the peer group of the source mount.
1604 * (+) the cloned mount is created under the destination mount and is marked
1605 * as shared. The cloned mount is added to the peer group of the source
1607 * (+++) the mount is propagated to all the mounts in the propagation tree
1608 * of the destination mount and the cloned mount is made slave
1609 * of the same master as that of the source mount. The cloned mount
1610 * is marked as 'shared and slave'.
1611 * (*) the cloned mount is made a slave of the same master as that of the
1614 * ---------------------------------------------------------------------------
1615 * | MOVE MOUNT OPERATION |
1616 * |**************************************************************************
1617 * | source-->| shared | private | slave | unbindable |
1621 * |**************************************************************************
1622 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1624 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1625 * ***************************************************************************
1627 * (+) the mount is moved to the destination. And is then propagated to
1628 * all the mounts in the propagation tree of the destination mount.
1629 * (+*) the mount is moved to the destination.
1630 * (+++) the mount is moved to the destination and is then propagated to
1631 * all the mounts belonging to the destination mount's propagation tree.
1632 * the mount is marked as 'shared and slave'.
1633 * (*) the mount continues to be a slave at the new location.
1635 * if the source mount is a tree, the operations explained above is
1636 * applied to each mount in the tree.
1637 * Must be called without spinlocks held, since this function can sleep
1640 static int attach_recursive_mnt(struct mount *source_mnt,
1641 struct mount *dest_mnt,
1642 struct mountpoint *dest_mp,
1643 struct path *parent_path)
1645 HLIST_HEAD(tree_list);
1646 struct mount *child, *p;
1647 struct hlist_node *n;
1650 if (IS_MNT_SHARED(dest_mnt)) {
1651 err = invent_group_ids(source_mnt, true);
1654 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
1657 goto out_cleanup_ids;
1658 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1664 detach_mnt(source_mnt, parent_path);
1665 attach_mnt(source_mnt, dest_mnt, dest_mp);
1666 touch_mnt_namespace(source_mnt->mnt_ns);
1668 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
1669 commit_tree(source_mnt, NULL);
1672 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
1674 hlist_del_init(&child->mnt_hash);
1675 q = __lookup_mnt_last(&child->mnt_parent->mnt,
1676 child->mnt_mountpoint);
1677 commit_tree(child, q);
1679 unlock_mount_hash();
1684 while (!hlist_empty(&tree_list)) {
1685 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
1686 umount_tree(child, 0);
1688 unlock_mount_hash();
1689 cleanup_group_ids(source_mnt, NULL);
1694 static struct mountpoint *lock_mount(struct path *path)
1696 struct vfsmount *mnt;
1697 struct dentry *dentry = path->dentry;
1699 mutex_lock(&dentry->d_inode->i_mutex);
1700 if (unlikely(cant_mount(dentry))) {
1701 mutex_unlock(&dentry->d_inode->i_mutex);
1702 return ERR_PTR(-ENOENT);
1705 mnt = lookup_mnt(path);
1707 struct mountpoint *mp = new_mountpoint(dentry);
1710 mutex_unlock(&dentry->d_inode->i_mutex);
1716 mutex_unlock(&path->dentry->d_inode->i_mutex);
1719 dentry = path->dentry = dget(mnt->mnt_root);
1723 static void unlock_mount(struct mountpoint *where)
1725 struct dentry *dentry = where->m_dentry;
1726 put_mountpoint(where);
1728 mutex_unlock(&dentry->d_inode->i_mutex);
1731 static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
1733 if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
1736 if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
1737 S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
1740 return attach_recursive_mnt(mnt, p, mp, NULL);
1744 * Sanity check the flags to change_mnt_propagation.
1747 static int flags_to_propagation_type(int flags)
1749 int type = flags & ~(MS_REC | MS_SILENT);
1751 /* Fail if any non-propagation flags are set */
1752 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1754 /* Only one propagation flag should be set */
1755 if (!is_power_of_2(type))
1761 * recursively change the type of the mountpoint.
1763 static int do_change_type(struct path *path, int flag)
1766 struct mount *mnt = real_mount(path->mnt);
1767 int recurse = flag & MS_REC;
1771 if (path->dentry != path->mnt->mnt_root)
1774 type = flags_to_propagation_type(flag);
1779 if (type == MS_SHARED) {
1780 err = invent_group_ids(mnt, recurse);
1786 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1787 change_mnt_propagation(m, type);
1788 unlock_mount_hash();
1795 static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
1797 struct mount *child;
1798 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
1799 if (!is_subdir(child->mnt_mountpoint, dentry))
1802 if (child->mnt.mnt_flags & MNT_LOCKED)
1809 * do loopback mount.
1811 static int do_loopback(struct path *path, const char *old_name,
1814 struct path old_path;
1815 struct mount *mnt = NULL, *old, *parent;
1816 struct mountpoint *mp;
1818 if (!old_name || !*old_name)
1820 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1825 if (mnt_ns_loop(old_path.dentry))
1828 mp = lock_mount(path);
1833 old = real_mount(old_path.mnt);
1834 parent = real_mount(path->mnt);
1837 if (IS_MNT_UNBINDABLE(old))
1840 if (!check_mnt(parent) || !check_mnt(old))
1843 if (!recurse && has_locked_children(old, old_path.dentry))
1847 mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
1849 mnt = clone_mnt(old, old_path.dentry, 0);
1856 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
1858 err = graft_tree(mnt, parent, mp);
1861 umount_tree(mnt, 0);
1862 unlock_mount_hash();
1867 path_put(&old_path);
1871 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1874 int readonly_request = 0;
1876 if (ms_flags & MS_RDONLY)
1877 readonly_request = 1;
1878 if (readonly_request == __mnt_is_readonly(mnt))
1881 if (mnt->mnt_flags & MNT_LOCK_READONLY)
1884 if (readonly_request)
1885 error = mnt_make_readonly(real_mount(mnt));
1887 __mnt_unmake_readonly(real_mount(mnt));
1892 * change filesystem flags. dir should be a physical root of filesystem.
1893 * If you've mounted a non-root directory somewhere and want to do remount
1894 * on it - tough luck.
1896 static int do_remount(struct path *path, int flags, int mnt_flags,
1900 struct super_block *sb = path->mnt->mnt_sb;
1901 struct mount *mnt = real_mount(path->mnt);
1903 if (!check_mnt(mnt))
1906 if (path->dentry != path->mnt->mnt_root)
1909 err = security_sb_remount(sb, data);
1913 down_write(&sb->s_umount);
1914 if (flags & MS_BIND)
1915 err = change_mount_flags(path->mnt, flags);
1916 else if (!capable(CAP_SYS_ADMIN))
1919 err = do_remount_sb(sb, flags, data, 0);
1922 mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
1923 mnt->mnt.mnt_flags = mnt_flags;
1924 touch_mnt_namespace(mnt->mnt_ns);
1925 unlock_mount_hash();
1927 up_write(&sb->s_umount);
1931 static inline int tree_contains_unbindable(struct mount *mnt)
1934 for (p = mnt; p; p = next_mnt(p, mnt)) {
1935 if (IS_MNT_UNBINDABLE(p))
1941 static int do_move_mount(struct path *path, const char *old_name)
1943 struct path old_path, parent_path;
1946 struct mountpoint *mp;
1948 if (!old_name || !*old_name)
1950 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1954 mp = lock_mount(path);
1959 old = real_mount(old_path.mnt);
1960 p = real_mount(path->mnt);
1963 if (!check_mnt(p) || !check_mnt(old))
1966 if (old->mnt.mnt_flags & MNT_LOCKED)
1970 if (old_path.dentry != old_path.mnt->mnt_root)
1973 if (!mnt_has_parent(old))
1976 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1977 S_ISDIR(old_path.dentry->d_inode->i_mode))
1980 * Don't move a mount residing in a shared parent.
1982 if (IS_MNT_SHARED(old->mnt_parent))
1985 * Don't move a mount tree containing unbindable mounts to a destination
1986 * mount which is shared.
1988 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
1991 for (; mnt_has_parent(p); p = p->mnt_parent)
1995 err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
1999 /* if the mount is moved, it should no longer be expire
2001 list_del_init(&old->mnt_expire);
2006 path_put(&parent_path);
2007 path_put(&old_path);
2011 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
2014 const char *subtype = strchr(fstype, '.');
2023 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
2025 if (!mnt->mnt_sb->s_subtype)
2031 return ERR_PTR(err);
2035 * add a mount into a namespace's mount tree
2037 static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
2039 struct mountpoint *mp;
2040 struct mount *parent;
2043 mnt_flags &= ~MNT_INTERNAL_FLAGS;
2045 mp = lock_mount(path);
2049 parent = real_mount(path->mnt);
2051 if (unlikely(!check_mnt(parent))) {
2052 /* that's acceptable only for automounts done in private ns */
2053 if (!(mnt_flags & MNT_SHRINKABLE))
2055 /* ... and for those we'd better have mountpoint still alive */
2056 if (!parent->mnt_ns)
2060 /* Refuse the same filesystem on the same mount point */
2062 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
2063 path->mnt->mnt_root == path->dentry)
2067 if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
2070 newmnt->mnt.mnt_flags = mnt_flags;
2071 err = graft_tree(newmnt, parent, mp);
2079 * create a new mount for userspace and request it to be added into the
2082 static int do_new_mount(struct path *path, const char *fstype, int flags,
2083 int mnt_flags, const char *name, void *data)
2085 struct file_system_type *type;
2086 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2087 struct vfsmount *mnt;
2093 type = get_fs_type(fstype);
2097 if (user_ns != &init_user_ns) {
2098 if (!(type->fs_flags & FS_USERNS_MOUNT)) {
2099 put_filesystem(type);
2102 /* Only in special cases allow devices from mounts
2103 * created outside the initial user namespace.
2105 if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
2107 mnt_flags |= MNT_NODEV;
2111 mnt = vfs_kern_mount(type, flags, name, data);
2112 if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
2113 !mnt->mnt_sb->s_subtype)
2114 mnt = fs_set_subtype(mnt, fstype);
2116 put_filesystem(type);
2118 return PTR_ERR(mnt);
2120 err = do_add_mount(real_mount(mnt), path, mnt_flags);
2126 int finish_automount(struct vfsmount *m, struct path *path)
2128 struct mount *mnt = real_mount(m);
2130 /* The new mount record should have at least 2 refs to prevent it being
2131 * expired before we get a chance to add it
2133 BUG_ON(mnt_get_count(mnt) < 2);
2135 if (m->mnt_sb == path->mnt->mnt_sb &&
2136 m->mnt_root == path->dentry) {
2141 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2145 /* remove m from any expiration list it may be on */
2146 if (!list_empty(&mnt->mnt_expire)) {
2148 list_del_init(&mnt->mnt_expire);
2157 * mnt_set_expiry - Put a mount on an expiration list
2158 * @mnt: The mount to list.
2159 * @expiry_list: The list to add the mount to.
2161 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2165 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2169 EXPORT_SYMBOL(mnt_set_expiry);
2172 * process a list of expirable mountpoints with the intent of discarding any
2173 * mountpoints that aren't in use and haven't been touched since last we came
2176 void mark_mounts_for_expiry(struct list_head *mounts)
2178 struct mount *mnt, *next;
2179 LIST_HEAD(graveyard);
2181 if (list_empty(mounts))
2187 /* extract from the expiration list every vfsmount that matches the
2188 * following criteria:
2189 * - only referenced by its parent vfsmount
2190 * - still marked for expiry (marked on the last call here; marks are
2191 * cleared by mntput())
2193 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2194 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2195 propagate_mount_busy(mnt, 1))
2197 list_move(&mnt->mnt_expire, &graveyard);
2199 while (!list_empty(&graveyard)) {
2200 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2201 touch_mnt_namespace(mnt->mnt_ns);
2202 umount_tree(mnt, 1);
2204 unlock_mount_hash();
2208 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2211 * Ripoff of 'select_parent()'
2213 * search the list of submounts for a given mountpoint, and move any
2214 * shrinkable submounts to the 'graveyard' list.
2216 static int select_submounts(struct mount *parent, struct list_head *graveyard)
2218 struct mount *this_parent = parent;
2219 struct list_head *next;
2223 next = this_parent->mnt_mounts.next;
2225 while (next != &this_parent->mnt_mounts) {
2226 struct list_head *tmp = next;
2227 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2230 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2233 * Descend a level if the d_mounts list is non-empty.
2235 if (!list_empty(&mnt->mnt_mounts)) {
2240 if (!propagate_mount_busy(mnt, 1)) {
2241 list_move_tail(&mnt->mnt_expire, graveyard);
2246 * All done at this level ... ascend and resume the search
2248 if (this_parent != parent) {
2249 next = this_parent->mnt_child.next;
2250 this_parent = this_parent->mnt_parent;
2257 * process a list of expirable mountpoints with the intent of discarding any
2258 * submounts of a specific parent mountpoint
2260 * mount_lock must be held for write
2262 static void shrink_submounts(struct mount *mnt)
2264 LIST_HEAD(graveyard);
2267 /* extract submounts of 'mountpoint' from the expiration list */
2268 while (select_submounts(mnt, &graveyard)) {
2269 while (!list_empty(&graveyard)) {
2270 m = list_first_entry(&graveyard, struct mount,
2272 touch_mnt_namespace(m->mnt_ns);
2279 * Some copy_from_user() implementations do not return the exact number of
2280 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2281 * Note that this function differs from copy_from_user() in that it will oops
2282 * on bad values of `to', rather than returning a short copy.
2284 static long exact_copy_from_user(void *to, const void __user * from,
2288 const char __user *f = from;
2291 if (!access_ok(VERIFY_READ, from, n))
2295 if (__get_user(c, f)) {
2306 int copy_mount_options(const void __user * data, unsigned long *where)
2316 if (!(page = __get_free_page(GFP_KERNEL)))
2319 /* We only care that *some* data at the address the user
2320 * gave us is valid. Just in case, we'll zero
2321 * the remainder of the page.
2323 /* copy_from_user cannot cross TASK_SIZE ! */
2324 size = TASK_SIZE - (unsigned long)data;
2325 if (size > PAGE_SIZE)
2328 i = size - exact_copy_from_user((void *)page, data, size);
2334 memset((char *)page + i, 0, PAGE_SIZE - i);
2339 int copy_mount_string(const void __user *data, char **where)
2348 tmp = strndup_user(data, PAGE_SIZE);
2350 return PTR_ERR(tmp);
2357 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2358 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2360 * data is a (void *) that can point to any structure up to
2361 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2362 * information (or be NULL).
2364 * Pre-0.97 versions of mount() didn't have a flags word.
2365 * When the flags word was introduced its top half was required
2366 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2367 * Therefore, if this magic number is present, it carries no information
2368 * and must be discarded.
2370 long do_mount(const char *dev_name, const char *dir_name,
2371 const char *type_page, unsigned long flags, void *data_page)
2378 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2379 flags &= ~MS_MGC_MSK;
2381 /* Basic sanity checks */
2383 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2387 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2389 /* ... and get the mountpoint */
2390 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2394 retval = security_sb_mount(dev_name, &path,
2395 type_page, flags, data_page);
2396 if (!retval && !may_mount())
2401 /* Default to relatime unless overriden */
2402 if (!(flags & MS_NOATIME))
2403 mnt_flags |= MNT_RELATIME;
2405 /* Separate the per-mountpoint flags */
2406 if (flags & MS_NOSUID)
2407 mnt_flags |= MNT_NOSUID;
2408 if (flags & MS_NODEV)
2409 mnt_flags |= MNT_NODEV;
2410 if (flags & MS_NOEXEC)
2411 mnt_flags |= MNT_NOEXEC;
2412 if (flags & MS_NOATIME)
2413 mnt_flags |= MNT_NOATIME;
2414 if (flags & MS_NODIRATIME)
2415 mnt_flags |= MNT_NODIRATIME;
2416 if (flags & MS_STRICTATIME)
2417 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2418 if (flags & MS_RDONLY)
2419 mnt_flags |= MNT_READONLY;
2421 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2422 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2425 if (flags & MS_REMOUNT)
2426 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2428 else if (flags & MS_BIND)
2429 retval = do_loopback(&path, dev_name, flags & MS_REC);
2430 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2431 retval = do_change_type(&path, flags);
2432 else if (flags & MS_MOVE)
2433 retval = do_move_mount(&path, dev_name);
2435 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2436 dev_name, data_page);
2442 static void free_mnt_ns(struct mnt_namespace *ns)
2444 proc_free_inum(ns->proc_inum);
2445 put_user_ns(ns->user_ns);
2450 * Assign a sequence number so we can detect when we attempt to bind
2451 * mount a reference to an older mount namespace into the current
2452 * mount namespace, preventing reference counting loops. A 64bit
2453 * number incrementing at 10Ghz will take 12,427 years to wrap which
2454 * is effectively never, so we can ignore the possibility.
2456 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
2458 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
2460 struct mnt_namespace *new_ns;
2463 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2465 return ERR_PTR(-ENOMEM);
2466 ret = proc_alloc_inum(&new_ns->proc_inum);
2469 return ERR_PTR(ret);
2471 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
2472 atomic_set(&new_ns->count, 1);
2473 new_ns->root = NULL;
2474 INIT_LIST_HEAD(&new_ns->list);
2475 init_waitqueue_head(&new_ns->poll);
2477 new_ns->user_ns = get_user_ns(user_ns);
2481 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2482 struct user_namespace *user_ns, struct fs_struct *new_fs)
2484 struct mnt_namespace *new_ns;
2485 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2486 struct mount *p, *q;
2493 if (likely(!(flags & CLONE_NEWNS))) {
2500 new_ns = alloc_mnt_ns(user_ns);
2505 /* First pass: copy the tree topology */
2506 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
2507 if (user_ns != ns->user_ns)
2508 copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
2509 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
2512 free_mnt_ns(new_ns);
2513 return ERR_CAST(new);
2516 list_add_tail(&new_ns->list, &new->mnt_list);
2519 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2520 * as belonging to new namespace. We have already acquired a private
2521 * fs_struct, so tsk->fs->lock is not needed.
2528 if (&p->mnt == new_fs->root.mnt) {
2529 new_fs->root.mnt = mntget(&q->mnt);
2532 if (&p->mnt == new_fs->pwd.mnt) {
2533 new_fs->pwd.mnt = mntget(&q->mnt);
2537 p = next_mnt(p, old);
2538 q = next_mnt(q, new);
2541 while (p->mnt.mnt_root != q->mnt.mnt_root)
2542 p = next_mnt(p, old);
2555 * create_mnt_ns - creates a private namespace and adds a root filesystem
2556 * @mnt: pointer to the new root filesystem mountpoint
2558 static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
2560 struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
2561 if (!IS_ERR(new_ns)) {
2562 struct mount *mnt = real_mount(m);
2563 mnt->mnt_ns = new_ns;
2565 list_add(&mnt->mnt_list, &new_ns->list);
2572 struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
2574 struct mnt_namespace *ns;
2575 struct super_block *s;
2579 ns = create_mnt_ns(mnt);
2581 return ERR_CAST(ns);
2583 err = vfs_path_lookup(mnt->mnt_root, mnt,
2584 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
2589 return ERR_PTR(err);
2591 /* trade a vfsmount reference for active sb one */
2592 s = path.mnt->mnt_sb;
2593 atomic_inc(&s->s_active);
2595 /* lock the sucker */
2596 down_write(&s->s_umount);
2597 /* ... and return the root of (sub)tree on it */
2600 EXPORT_SYMBOL(mount_subtree);
2602 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2603 char __user *, type, unsigned long, flags, void __user *, data)
2607 struct filename *kernel_dir;
2609 unsigned long data_page;
2611 ret = copy_mount_string(type, &kernel_type);
2615 kernel_dir = getname(dir_name);
2616 if (IS_ERR(kernel_dir)) {
2617 ret = PTR_ERR(kernel_dir);
2621 ret = copy_mount_string(dev_name, &kernel_dev);
2625 ret = copy_mount_options(data, &data_page);
2629 ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
2630 (void *) data_page);
2632 free_page(data_page);
2636 putname(kernel_dir);
2644 * Return true if path is reachable from root
2646 * namespace_sem or mount_lock is held
2648 bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
2649 const struct path *root)
2651 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
2652 dentry = mnt->mnt_mountpoint;
2653 mnt = mnt->mnt_parent;
2655 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
2658 int path_is_under(struct path *path1, struct path *path2)
2661 read_seqlock_excl(&mount_lock);
2662 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
2663 read_sequnlock_excl(&mount_lock);
2666 EXPORT_SYMBOL(path_is_under);
2669 * pivot_root Semantics:
2670 * Moves the root file system of the current process to the directory put_old,
2671 * makes new_root as the new root file system of the current process, and sets
2672 * root/cwd of all processes which had them on the current root to new_root.
2675 * The new_root and put_old must be directories, and must not be on the
2676 * same file system as the current process root. The put_old must be
2677 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2678 * pointed to by put_old must yield the same directory as new_root. No other
2679 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2681 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2682 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2683 * in this situation.
2686 * - we don't move root/cwd if they are not at the root (reason: if something
2687 * cared enough to change them, it's probably wrong to force them elsewhere)
2688 * - it's okay to pick a root that isn't the root of a file system, e.g.
2689 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2690 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2693 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2694 const char __user *, put_old)
2696 struct path new, old, parent_path, root_parent, root;
2697 struct mount *new_mnt, *root_mnt, *old_mnt;
2698 struct mountpoint *old_mp, *root_mp;
2704 error = user_path_dir(new_root, &new);
2708 error = user_path_dir(put_old, &old);
2712 error = security_sb_pivotroot(&old, &new);
2716 get_fs_root(current->fs, &root);
2717 old_mp = lock_mount(&old);
2718 error = PTR_ERR(old_mp);
2723 new_mnt = real_mount(new.mnt);
2724 root_mnt = real_mount(root.mnt);
2725 old_mnt = real_mount(old.mnt);
2726 if (IS_MNT_SHARED(old_mnt) ||
2727 IS_MNT_SHARED(new_mnt->mnt_parent) ||
2728 IS_MNT_SHARED(root_mnt->mnt_parent))
2730 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
2732 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
2735 if (d_unlinked(new.dentry))
2738 if (new_mnt == root_mnt || old_mnt == root_mnt)
2739 goto out4; /* loop, on the same file system */
2741 if (root.mnt->mnt_root != root.dentry)
2742 goto out4; /* not a mountpoint */
2743 if (!mnt_has_parent(root_mnt))
2744 goto out4; /* not attached */
2745 root_mp = root_mnt->mnt_mp;
2746 if (new.mnt->mnt_root != new.dentry)
2747 goto out4; /* not a mountpoint */
2748 if (!mnt_has_parent(new_mnt))
2749 goto out4; /* not attached */
2750 /* make sure we can reach put_old from new_root */
2751 if (!is_path_reachable(old_mnt, old.dentry, &new))
2753 root_mp->m_count++; /* pin it so it won't go away */
2755 detach_mnt(new_mnt, &parent_path);
2756 detach_mnt(root_mnt, &root_parent);
2757 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
2758 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
2759 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2761 /* mount old root on put_old */
2762 attach_mnt(root_mnt, old_mnt, old_mp);
2763 /* mount new_root on / */
2764 attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
2765 touch_mnt_namespace(current->nsproxy->mnt_ns);
2766 unlock_mount_hash();
2767 chroot_fs_refs(&root, &new);
2768 put_mountpoint(root_mp);
2771 unlock_mount(old_mp);
2773 path_put(&root_parent);
2774 path_put(&parent_path);
2786 static void __init init_mount_tree(void)
2788 struct vfsmount *mnt;
2789 struct mnt_namespace *ns;
2791 struct file_system_type *type;
2793 type = get_fs_type("rootfs");
2795 panic("Can't find rootfs type");
2796 mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
2797 put_filesystem(type);
2799 panic("Can't create rootfs");
2801 ns = create_mnt_ns(mnt);
2803 panic("Can't allocate initial namespace");
2805 init_task.nsproxy->mnt_ns = ns;
2809 root.dentry = mnt->mnt_root;
2811 set_fs_pwd(current->fs, &root);
2812 set_fs_root(current->fs, &root);
2815 void __init mnt_init(void)
2820 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
2821 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2823 mount_hashtable = alloc_large_system_hash("Mount-cache",
2824 sizeof(struct hlist_head),
2827 &m_hash_shift, &m_hash_mask, 0, 0);
2828 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
2829 sizeof(struct hlist_head),
2832 &mp_hash_shift, &mp_hash_mask, 0, 0);
2834 if (!mount_hashtable || !mountpoint_hashtable)
2835 panic("Failed to allocate mount hash table\n");
2837 for (u = 0; u <= m_hash_mask; u++)
2838 INIT_HLIST_HEAD(&mount_hashtable[u]);
2839 for (u = 0; u <= mp_hash_mask; u++)
2840 INIT_HLIST_HEAD(&mountpoint_hashtable[u]);
2846 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2848 fs_kobj = kobject_create_and_add("fs", NULL);
2850 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2855 void put_mnt_ns(struct mnt_namespace *ns)
2857 if (!atomic_dec_and_test(&ns->count))
2859 drop_collected_mounts(&ns->root->mnt);
2863 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2865 struct vfsmount *mnt;
2866 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2869 * it is a longterm mount, don't release mnt until
2870 * we unmount before file sys is unregistered
2872 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
2876 EXPORT_SYMBOL_GPL(kern_mount_data);
2878 void kern_unmount(struct vfsmount *mnt)
2880 /* release long term mount so mount point can be released */
2881 if (!IS_ERR_OR_NULL(mnt)) {
2882 real_mount(mnt)->mnt_ns = NULL;
2883 synchronize_rcu(); /* yecchhh... */
2887 EXPORT_SYMBOL(kern_unmount);
2889 bool our_mnt(struct vfsmount *mnt)
2891 return check_mnt(real_mount(mnt));
2894 bool current_chrooted(void)
2896 /* Does the current process have a non-standard root */
2897 struct path ns_root;
2898 struct path fs_root;
2901 /* Find the namespace root */
2902 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
2903 ns_root.dentry = ns_root.mnt->mnt_root;
2905 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
2908 get_fs_root(current->fs, &fs_root);
2910 chrooted = !path_equal(&fs_root, &ns_root);
2918 bool fs_fully_visible(struct file_system_type *type)
2920 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
2922 bool visible = false;
2927 down_read(&namespace_sem);
2928 list_for_each_entry(mnt, &ns->list, mnt_list) {
2929 struct mount *child;
2930 if (mnt->mnt.mnt_sb->s_type != type)
2933 /* This mount is not fully visible if there are any child mounts
2934 * that cover anything except for empty directories.
2936 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2937 struct inode *inode = child->mnt_mountpoint->d_inode;
2938 if (!S_ISDIR(inode->i_mode))
2940 if (inode->i_nlink > 2)
2948 up_read(&namespace_sem);
2952 static void *mntns_get(struct task_struct *task)
2954 struct mnt_namespace *ns = NULL;
2955 struct nsproxy *nsproxy;
2958 nsproxy = task_nsproxy(task);
2960 ns = nsproxy->mnt_ns;
2968 static void mntns_put(void *ns)
2973 static int mntns_install(struct nsproxy *nsproxy, void *ns)
2975 struct fs_struct *fs = current->fs;
2976 struct mnt_namespace *mnt_ns = ns;
2979 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
2980 !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
2981 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
2988 put_mnt_ns(nsproxy->mnt_ns);
2989 nsproxy->mnt_ns = mnt_ns;
2992 root.mnt = &mnt_ns->root->mnt;
2993 root.dentry = mnt_ns->root->mnt.mnt_root;
2995 while(d_mountpoint(root.dentry) && follow_down_one(&root))
2998 /* Update the pwd and root */
2999 set_fs_pwd(fs, &root);
3000 set_fs_root(fs, &root);
3006 static unsigned int mntns_inum(void *ns)
3008 struct mnt_namespace *mnt_ns = ns;
3009 return mnt_ns->proc_inum;
3012 const struct proc_ns_operations mntns_operations = {
3014 .type = CLONE_NEWNS,
3017 .install = mntns_install,