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);
781 static void attach_shadowed(struct mount *mnt,
782 struct mount *parent,
783 struct mount *shadows)
786 hlist_add_after_rcu(&shadows->mnt_hash, &mnt->mnt_hash);
787 list_add(&mnt->mnt_child, &shadows->mnt_child);
789 hlist_add_head_rcu(&mnt->mnt_hash,
790 m_hash(&parent->mnt, mnt->mnt_mountpoint));
791 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
796 * vfsmount lock must be held for write
798 static void commit_tree(struct mount *mnt, struct mount *shadows)
800 struct mount *parent = mnt->mnt_parent;
803 struct mnt_namespace *n = parent->mnt_ns;
805 BUG_ON(parent == mnt);
807 list_add_tail(&head, &mnt->mnt_list);
808 list_for_each_entry(m, &head, mnt_list)
811 list_splice(&head, n->list.prev);
813 attach_shadowed(mnt, parent, shadows);
814 touch_mnt_namespace(n);
817 static struct mount *next_mnt(struct mount *p, struct mount *root)
819 struct list_head *next = p->mnt_mounts.next;
820 if (next == &p->mnt_mounts) {
824 next = p->mnt_child.next;
825 if (next != &p->mnt_parent->mnt_mounts)
830 return list_entry(next, struct mount, mnt_child);
833 static struct mount *skip_mnt_tree(struct mount *p)
835 struct list_head *prev = p->mnt_mounts.prev;
836 while (prev != &p->mnt_mounts) {
837 p = list_entry(prev, struct mount, mnt_child);
838 prev = p->mnt_mounts.prev;
844 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
850 return ERR_PTR(-ENODEV);
852 mnt = alloc_vfsmnt(name);
854 return ERR_PTR(-ENOMEM);
856 if (flags & MS_KERNMOUNT)
857 mnt->mnt.mnt_flags = MNT_INTERNAL;
859 root = mount_fs(type, flags, name, data);
863 return ERR_CAST(root);
866 mnt->mnt.mnt_root = root;
867 mnt->mnt.mnt_sb = root->d_sb;
868 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
869 mnt->mnt_parent = mnt;
871 list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
875 EXPORT_SYMBOL_GPL(vfs_kern_mount);
877 static struct mount *clone_mnt(struct mount *old, struct dentry *root,
880 struct super_block *sb = old->mnt.mnt_sb;
884 mnt = alloc_vfsmnt(old->mnt_devname);
886 return ERR_PTR(-ENOMEM);
888 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
889 mnt->mnt_group_id = 0; /* not a peer of original */
891 mnt->mnt_group_id = old->mnt_group_id;
893 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
894 err = mnt_alloc_group_id(mnt);
899 mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~(MNT_WRITE_HOLD|MNT_MARKED);
900 /* Don't allow unprivileged users to change mount flags */
901 if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
902 mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
904 /* Don't allow unprivileged users to reveal what is under a mount */
905 if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
906 mnt->mnt.mnt_flags |= MNT_LOCKED;
908 atomic_inc(&sb->s_active);
909 mnt->mnt.mnt_sb = sb;
910 mnt->mnt.mnt_root = dget(root);
911 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
912 mnt->mnt_parent = mnt;
914 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
917 if ((flag & CL_SLAVE) ||
918 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
919 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
920 mnt->mnt_master = old;
921 CLEAR_MNT_SHARED(mnt);
922 } else if (!(flag & CL_PRIVATE)) {
923 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
924 list_add(&mnt->mnt_share, &old->mnt_share);
925 if (IS_MNT_SLAVE(old))
926 list_add(&mnt->mnt_slave, &old->mnt_slave);
927 mnt->mnt_master = old->mnt_master;
929 if (flag & CL_MAKE_SHARED)
932 /* stick the duplicate mount on the same expiry list
933 * as the original if that was on one */
934 if (flag & CL_EXPIRE) {
935 if (!list_empty(&old->mnt_expire))
936 list_add(&mnt->mnt_expire, &old->mnt_expire);
947 static void mntput_no_expire(struct mount *mnt)
950 mnt_add_count(mnt, -1);
951 if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */
956 if (mnt_get_count(mnt)) {
961 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
966 mnt->mnt.mnt_flags |= MNT_DOOMED;
969 list_del(&mnt->mnt_instance);
973 * This probably indicates that somebody messed
974 * up a mnt_want/drop_write() pair. If this
975 * happens, the filesystem was probably unable
976 * to make r/w->r/o transitions.
979 * The locking used to deal with mnt_count decrement provides barriers,
980 * so mnt_get_writers() below is safe.
982 WARN_ON(mnt_get_writers(mnt));
983 if (unlikely(mnt->mnt_pins.first))
985 fsnotify_vfsmount_delete(&mnt->mnt);
986 dput(mnt->mnt.mnt_root);
987 deactivate_super(mnt->mnt.mnt_sb);
989 call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt);
992 void mntput(struct vfsmount *mnt)
995 struct mount *m = real_mount(mnt);
996 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
997 if (unlikely(m->mnt_expiry_mark))
998 m->mnt_expiry_mark = 0;
1002 EXPORT_SYMBOL(mntput);
1004 struct vfsmount *mntget(struct vfsmount *mnt)
1007 mnt_add_count(real_mount(mnt), 1);
1010 EXPORT_SYMBOL(mntget);
1012 struct vfsmount *mnt_clone_internal(struct path *path)
1015 p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE);
1018 p->mnt.mnt_flags |= MNT_INTERNAL;
1022 static inline void mangle(struct seq_file *m, const char *s)
1024 seq_escape(m, s, " \t\n\\");
1028 * Simple .show_options callback for filesystems which don't want to
1029 * implement more complex mount option showing.
1031 * See also save_mount_options().
1033 int generic_show_options(struct seq_file *m, struct dentry *root)
1035 const char *options;
1038 options = rcu_dereference(root->d_sb->s_options);
1040 if (options != NULL && options[0]) {
1048 EXPORT_SYMBOL(generic_show_options);
1051 * If filesystem uses generic_show_options(), this function should be
1052 * called from the fill_super() callback.
1054 * The .remount_fs callback usually needs to be handled in a special
1055 * way, to make sure, that previous options are not overwritten if the
1058 * Also note, that if the filesystem's .remount_fs function doesn't
1059 * reset all options to their default value, but changes only newly
1060 * given options, then the displayed options will not reflect reality
1063 void save_mount_options(struct super_block *sb, char *options)
1065 BUG_ON(sb->s_options);
1066 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
1068 EXPORT_SYMBOL(save_mount_options);
1070 void replace_mount_options(struct super_block *sb, char *options)
1072 char *old = sb->s_options;
1073 rcu_assign_pointer(sb->s_options, options);
1079 EXPORT_SYMBOL(replace_mount_options);
1081 #ifdef CONFIG_PROC_FS
1082 /* iterator; we want it to have access to namespace_sem, thus here... */
1083 static void *m_start(struct seq_file *m, loff_t *pos)
1085 struct proc_mounts *p = proc_mounts(m);
1087 down_read(&namespace_sem);
1088 if (p->cached_event == p->ns->event) {
1089 void *v = p->cached_mount;
1090 if (*pos == p->cached_index)
1092 if (*pos == p->cached_index + 1) {
1093 v = seq_list_next(v, &p->ns->list, &p->cached_index);
1094 return p->cached_mount = v;
1098 p->cached_event = p->ns->event;
1099 p->cached_mount = seq_list_start(&p->ns->list, *pos);
1100 p->cached_index = *pos;
1101 return p->cached_mount;
1104 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1106 struct proc_mounts *p = proc_mounts(m);
1108 p->cached_mount = seq_list_next(v, &p->ns->list, pos);
1109 p->cached_index = *pos;
1110 return p->cached_mount;
1113 static void m_stop(struct seq_file *m, void *v)
1115 up_read(&namespace_sem);
1118 static int m_show(struct seq_file *m, void *v)
1120 struct proc_mounts *p = proc_mounts(m);
1121 struct mount *r = list_entry(v, struct mount, mnt_list);
1122 return p->show(m, &r->mnt);
1125 const struct seq_operations mounts_op = {
1131 #endif /* CONFIG_PROC_FS */
1134 * may_umount_tree - check if a mount tree is busy
1135 * @mnt: root of mount tree
1137 * This is called to check if a tree of mounts has any
1138 * open files, pwds, chroots or sub mounts that are
1141 int may_umount_tree(struct vfsmount *m)
1143 struct mount *mnt = real_mount(m);
1144 int actual_refs = 0;
1145 int minimum_refs = 0;
1149 /* write lock needed for mnt_get_count */
1151 for (p = mnt; p; p = next_mnt(p, mnt)) {
1152 actual_refs += mnt_get_count(p);
1155 unlock_mount_hash();
1157 if (actual_refs > minimum_refs)
1163 EXPORT_SYMBOL(may_umount_tree);
1166 * may_umount - check if a mount point is busy
1167 * @mnt: root of mount
1169 * This is called to check if a mount point has any
1170 * open files, pwds, chroots or sub mounts. If the
1171 * mount has sub mounts this will return busy
1172 * regardless of whether the sub mounts are busy.
1174 * Doesn't take quota and stuff into account. IOW, in some cases it will
1175 * give false negatives. The main reason why it's here is that we need
1176 * a non-destructive way to look for easily umountable filesystems.
1178 int may_umount(struct vfsmount *mnt)
1181 down_read(&namespace_sem);
1183 if (propagate_mount_busy(real_mount(mnt), 2))
1185 unlock_mount_hash();
1186 up_read(&namespace_sem);
1190 EXPORT_SYMBOL(may_umount);
1192 static HLIST_HEAD(unmounted); /* protected by namespace_sem */
1194 static void namespace_unlock(void)
1197 struct hlist_head head = unmounted;
1199 if (likely(hlist_empty(&head))) {
1200 up_write(&namespace_sem);
1204 head.first->pprev = &head.first;
1205 INIT_HLIST_HEAD(&unmounted);
1207 up_write(&namespace_sem);
1211 while (!hlist_empty(&head)) {
1212 mnt = hlist_entry(head.first, struct mount, mnt_hash);
1213 hlist_del_init(&mnt->mnt_hash);
1214 if (mnt->mnt_ex_mountpoint.mnt)
1215 path_put(&mnt->mnt_ex_mountpoint);
1220 static inline void namespace_lock(void)
1222 down_write(&namespace_sem);
1226 * mount_lock must be held
1227 * namespace_sem must be held for write
1228 * how = 0 => just this tree, don't propagate
1229 * how = 1 => propagate; we know that nobody else has reference to any victims
1230 * how = 2 => lazy umount
1232 void umount_tree(struct mount *mnt, int how)
1234 HLIST_HEAD(tmp_list);
1236 struct mount *last = NULL;
1238 for (p = mnt; p; p = next_mnt(p, mnt)) {
1239 hlist_del_init_rcu(&p->mnt_hash);
1240 hlist_add_head(&p->mnt_hash, &tmp_list);
1244 propagate_umount(&tmp_list);
1246 hlist_for_each_entry(p, &tmp_list, mnt_hash) {
1247 list_del_init(&p->mnt_expire);
1248 list_del_init(&p->mnt_list);
1249 __touch_mnt_namespace(p->mnt_ns);
1252 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1253 list_del_init(&p->mnt_child);
1254 if (mnt_has_parent(p)) {
1255 put_mountpoint(p->mnt_mp);
1256 /* move the reference to mountpoint into ->mnt_ex_mountpoint */
1257 p->mnt_ex_mountpoint.dentry = p->mnt_mountpoint;
1258 p->mnt_ex_mountpoint.mnt = &p->mnt_parent->mnt;
1259 p->mnt_mountpoint = p->mnt.mnt_root;
1263 change_mnt_propagation(p, MS_PRIVATE);
1267 last->mnt_hash.next = unmounted.first;
1268 unmounted.first = tmp_list.first;
1269 unmounted.first->pprev = &unmounted.first;
1273 static void shrink_submounts(struct mount *mnt);
1275 static int do_umount(struct mount *mnt, int flags)
1277 struct super_block *sb = mnt->mnt.mnt_sb;
1280 retval = security_sb_umount(&mnt->mnt, flags);
1285 * Allow userspace to request a mountpoint be expired rather than
1286 * unmounting unconditionally. Unmount only happens if:
1287 * (1) the mark is already set (the mark is cleared by mntput())
1288 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1290 if (flags & MNT_EXPIRE) {
1291 if (&mnt->mnt == current->fs->root.mnt ||
1292 flags & (MNT_FORCE | MNT_DETACH))
1296 * probably don't strictly need the lock here if we examined
1297 * all race cases, but it's a slowpath.
1300 if (mnt_get_count(mnt) != 2) {
1301 unlock_mount_hash();
1304 unlock_mount_hash();
1306 if (!xchg(&mnt->mnt_expiry_mark, 1))
1311 * If we may have to abort operations to get out of this
1312 * mount, and they will themselves hold resources we must
1313 * allow the fs to do things. In the Unix tradition of
1314 * 'Gee thats tricky lets do it in userspace' the umount_begin
1315 * might fail to complete on the first run through as other tasks
1316 * must return, and the like. Thats for the mount program to worry
1317 * about for the moment.
1320 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1321 sb->s_op->umount_begin(sb);
1325 * No sense to grab the lock for this test, but test itself looks
1326 * somewhat bogus. Suggestions for better replacement?
1327 * Ho-hum... In principle, we might treat that as umount + switch
1328 * to rootfs. GC would eventually take care of the old vfsmount.
1329 * Actually it makes sense, especially if rootfs would contain a
1330 * /reboot - static binary that would close all descriptors and
1331 * call reboot(9). Then init(8) could umount root and exec /reboot.
1333 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1335 * Special case for "unmounting" root ...
1336 * we just try to remount it readonly.
1338 down_write(&sb->s_umount);
1339 if (!(sb->s_flags & MS_RDONLY))
1340 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1341 up_write(&sb->s_umount);
1349 if (flags & MNT_DETACH) {
1350 if (!list_empty(&mnt->mnt_list))
1351 umount_tree(mnt, 2);
1354 shrink_submounts(mnt);
1356 if (!propagate_mount_busy(mnt, 2)) {
1357 if (!list_empty(&mnt->mnt_list))
1358 umount_tree(mnt, 1);
1362 unlock_mount_hash();
1368 * Is the caller allowed to modify his namespace?
1370 static inline bool may_mount(void)
1372 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1376 * Now umount can handle mount points as well as block devices.
1377 * This is important for filesystems which use unnamed block devices.
1379 * We now support a flag for forced unmount like the other 'big iron'
1380 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1383 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1388 int lookup_flags = 0;
1390 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1396 if (!(flags & UMOUNT_NOFOLLOW))
1397 lookup_flags |= LOOKUP_FOLLOW;
1399 retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
1402 mnt = real_mount(path.mnt);
1404 if (path.dentry != path.mnt->mnt_root)
1406 if (!check_mnt(mnt))
1408 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1411 retval = do_umount(mnt, flags);
1413 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1415 mntput_no_expire(mnt);
1420 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1423 * The 2.0 compatible umount. No flags.
1425 SYSCALL_DEFINE1(oldumount, char __user *, name)
1427 return sys_umount(name, 0);
1432 static bool is_mnt_ns_file(struct dentry *dentry)
1434 /* Is this a proxy for a mount namespace? */
1435 struct inode *inode = dentry->d_inode;
1438 if (!proc_ns_inode(inode))
1441 ei = get_proc_ns(inode);
1442 if (ei->ns_ops != &mntns_operations)
1448 static bool mnt_ns_loop(struct dentry *dentry)
1450 /* Could bind mounting the mount namespace inode cause a
1451 * mount namespace loop?
1453 struct mnt_namespace *mnt_ns;
1454 if (!is_mnt_ns_file(dentry))
1457 mnt_ns = get_proc_ns(dentry->d_inode)->ns;
1458 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1461 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1464 struct mount *res, *p, *q, *r, *parent;
1466 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1467 return ERR_PTR(-EINVAL);
1469 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1470 return ERR_PTR(-EINVAL);
1472 res = q = clone_mnt(mnt, dentry, flag);
1476 q->mnt.mnt_flags &= ~MNT_LOCKED;
1477 q->mnt_mountpoint = mnt->mnt_mountpoint;
1480 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1482 if (!is_subdir(r->mnt_mountpoint, dentry))
1485 for (s = r; s; s = next_mnt(s, r)) {
1486 struct mount *t = NULL;
1487 if (!(flag & CL_COPY_UNBINDABLE) &&
1488 IS_MNT_UNBINDABLE(s)) {
1489 s = skip_mnt_tree(s);
1492 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1493 is_mnt_ns_file(s->mnt.mnt_root)) {
1494 s = skip_mnt_tree(s);
1497 while (p != s->mnt_parent) {
1503 q = clone_mnt(p, p->mnt.mnt_root, flag);
1507 list_add_tail(&q->mnt_list, &res->mnt_list);
1508 mnt_set_mountpoint(parent, p->mnt_mp, q);
1509 if (!list_empty(&parent->mnt_mounts)) {
1510 t = list_last_entry(&parent->mnt_mounts,
1511 struct mount, mnt_child);
1512 if (t->mnt_mp != p->mnt_mp)
1515 attach_shadowed(q, parent, t);
1516 unlock_mount_hash();
1523 umount_tree(res, 0);
1524 unlock_mount_hash();
1529 /* Caller should check returned pointer for errors */
1531 struct vfsmount *collect_mounts(struct path *path)
1535 tree = copy_tree(real_mount(path->mnt), path->dentry,
1536 CL_COPY_ALL | CL_PRIVATE);
1539 return ERR_CAST(tree);
1543 void drop_collected_mounts(struct vfsmount *mnt)
1547 umount_tree(real_mount(mnt), 0);
1548 unlock_mount_hash();
1552 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1553 struct vfsmount *root)
1556 int res = f(root, arg);
1559 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1560 res = f(&mnt->mnt, arg);
1567 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1571 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1572 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1573 mnt_release_group_id(p);
1577 static int invent_group_ids(struct mount *mnt, bool recurse)
1581 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1582 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1583 int err = mnt_alloc_group_id(p);
1585 cleanup_group_ids(mnt, p);
1595 * @source_mnt : mount tree to be attached
1596 * @nd : place the mount tree @source_mnt is attached
1597 * @parent_nd : if non-null, detach the source_mnt from its parent and
1598 * store the parent mount and mountpoint dentry.
1599 * (done when source_mnt is moved)
1601 * NOTE: in the table below explains the semantics when a source mount
1602 * of a given type is attached to a destination mount of a given type.
1603 * ---------------------------------------------------------------------------
1604 * | BIND MOUNT OPERATION |
1605 * |**************************************************************************
1606 * | source-->| shared | private | slave | unbindable |
1610 * |**************************************************************************
1611 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1613 * |non-shared| shared (+) | private | slave (*) | invalid |
1614 * ***************************************************************************
1615 * A bind operation clones the source mount and mounts the clone on the
1616 * destination mount.
1618 * (++) the cloned mount is propagated to all the mounts in the propagation
1619 * tree of the destination mount and the cloned mount is added to
1620 * the peer group of the source mount.
1621 * (+) the cloned mount is created under the destination mount and is marked
1622 * as shared. The cloned mount is added to the peer group of the source
1624 * (+++) the mount is propagated to all the mounts in the propagation tree
1625 * of the destination mount and the cloned mount is made slave
1626 * of the same master as that of the source mount. The cloned mount
1627 * is marked as 'shared and slave'.
1628 * (*) the cloned mount is made a slave of the same master as that of the
1631 * ---------------------------------------------------------------------------
1632 * | MOVE MOUNT OPERATION |
1633 * |**************************************************************************
1634 * | source-->| shared | private | slave | unbindable |
1638 * |**************************************************************************
1639 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1641 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1642 * ***************************************************************************
1644 * (+) the mount is moved to the destination. And is then propagated to
1645 * all the mounts in the propagation tree of the destination mount.
1646 * (+*) the mount is moved to the destination.
1647 * (+++) the mount is moved to the destination and is then propagated to
1648 * all the mounts belonging to the destination mount's propagation tree.
1649 * the mount is marked as 'shared and slave'.
1650 * (*) the mount continues to be a slave at the new location.
1652 * if the source mount is a tree, the operations explained above is
1653 * applied to each mount in the tree.
1654 * Must be called without spinlocks held, since this function can sleep
1657 static int attach_recursive_mnt(struct mount *source_mnt,
1658 struct mount *dest_mnt,
1659 struct mountpoint *dest_mp,
1660 struct path *parent_path)
1662 HLIST_HEAD(tree_list);
1663 struct mount *child, *p;
1664 struct hlist_node *n;
1667 if (IS_MNT_SHARED(dest_mnt)) {
1668 err = invent_group_ids(source_mnt, true);
1671 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
1674 goto out_cleanup_ids;
1675 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1681 detach_mnt(source_mnt, parent_path);
1682 attach_mnt(source_mnt, dest_mnt, dest_mp);
1683 touch_mnt_namespace(source_mnt->mnt_ns);
1685 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
1686 commit_tree(source_mnt, NULL);
1689 hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) {
1691 hlist_del_init(&child->mnt_hash);
1692 q = __lookup_mnt_last(&child->mnt_parent->mnt,
1693 child->mnt_mountpoint);
1694 commit_tree(child, q);
1696 unlock_mount_hash();
1701 while (!hlist_empty(&tree_list)) {
1702 child = hlist_entry(tree_list.first, struct mount, mnt_hash);
1703 umount_tree(child, 0);
1705 unlock_mount_hash();
1706 cleanup_group_ids(source_mnt, NULL);
1711 static struct mountpoint *lock_mount(struct path *path)
1713 struct vfsmount *mnt;
1714 struct dentry *dentry = path->dentry;
1716 mutex_lock(&dentry->d_inode->i_mutex);
1717 if (unlikely(cant_mount(dentry))) {
1718 mutex_unlock(&dentry->d_inode->i_mutex);
1719 return ERR_PTR(-ENOENT);
1722 mnt = lookup_mnt(path);
1724 struct mountpoint *mp = new_mountpoint(dentry);
1727 mutex_unlock(&dentry->d_inode->i_mutex);
1733 mutex_unlock(&path->dentry->d_inode->i_mutex);
1736 dentry = path->dentry = dget(mnt->mnt_root);
1740 static void unlock_mount(struct mountpoint *where)
1742 struct dentry *dentry = where->m_dentry;
1743 put_mountpoint(where);
1745 mutex_unlock(&dentry->d_inode->i_mutex);
1748 static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
1750 if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
1753 if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
1754 S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
1757 return attach_recursive_mnt(mnt, p, mp, NULL);
1761 * Sanity check the flags to change_mnt_propagation.
1764 static int flags_to_propagation_type(int flags)
1766 int type = flags & ~(MS_REC | MS_SILENT);
1768 /* Fail if any non-propagation flags are set */
1769 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1771 /* Only one propagation flag should be set */
1772 if (!is_power_of_2(type))
1778 * recursively change the type of the mountpoint.
1780 static int do_change_type(struct path *path, int flag)
1783 struct mount *mnt = real_mount(path->mnt);
1784 int recurse = flag & MS_REC;
1788 if (path->dentry != path->mnt->mnt_root)
1791 type = flags_to_propagation_type(flag);
1796 if (type == MS_SHARED) {
1797 err = invent_group_ids(mnt, recurse);
1803 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1804 change_mnt_propagation(m, type);
1805 unlock_mount_hash();
1812 static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
1814 struct mount *child;
1815 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
1816 if (!is_subdir(child->mnt_mountpoint, dentry))
1819 if (child->mnt.mnt_flags & MNT_LOCKED)
1826 * do loopback mount.
1828 static int do_loopback(struct path *path, const char *old_name,
1831 struct path old_path;
1832 struct mount *mnt = NULL, *old, *parent;
1833 struct mountpoint *mp;
1835 if (!old_name || !*old_name)
1837 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1842 if (mnt_ns_loop(old_path.dentry))
1845 mp = lock_mount(path);
1850 old = real_mount(old_path.mnt);
1851 parent = real_mount(path->mnt);
1854 if (IS_MNT_UNBINDABLE(old))
1857 if (!check_mnt(parent) || !check_mnt(old))
1860 if (!recurse && has_locked_children(old, old_path.dentry))
1864 mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
1866 mnt = clone_mnt(old, old_path.dentry, 0);
1873 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
1875 err = graft_tree(mnt, parent, mp);
1878 umount_tree(mnt, 0);
1879 unlock_mount_hash();
1884 path_put(&old_path);
1888 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1891 int readonly_request = 0;
1893 if (ms_flags & MS_RDONLY)
1894 readonly_request = 1;
1895 if (readonly_request == __mnt_is_readonly(mnt))
1898 if (mnt->mnt_flags & MNT_LOCK_READONLY)
1901 if (readonly_request)
1902 error = mnt_make_readonly(real_mount(mnt));
1904 __mnt_unmake_readonly(real_mount(mnt));
1909 * change filesystem flags. dir should be a physical root of filesystem.
1910 * If you've mounted a non-root directory somewhere and want to do remount
1911 * on it - tough luck.
1913 static int do_remount(struct path *path, int flags, int mnt_flags,
1917 struct super_block *sb = path->mnt->mnt_sb;
1918 struct mount *mnt = real_mount(path->mnt);
1920 if (!check_mnt(mnt))
1923 if (path->dentry != path->mnt->mnt_root)
1926 err = security_sb_remount(sb, data);
1930 down_write(&sb->s_umount);
1931 if (flags & MS_BIND)
1932 err = change_mount_flags(path->mnt, flags);
1933 else if (!capable(CAP_SYS_ADMIN))
1936 err = do_remount_sb(sb, flags, data, 0);
1939 mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
1940 mnt->mnt.mnt_flags = mnt_flags;
1941 touch_mnt_namespace(mnt->mnt_ns);
1942 unlock_mount_hash();
1944 up_write(&sb->s_umount);
1948 static inline int tree_contains_unbindable(struct mount *mnt)
1951 for (p = mnt; p; p = next_mnt(p, mnt)) {
1952 if (IS_MNT_UNBINDABLE(p))
1958 static int do_move_mount(struct path *path, const char *old_name)
1960 struct path old_path, parent_path;
1963 struct mountpoint *mp;
1965 if (!old_name || !*old_name)
1967 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1971 mp = lock_mount(path);
1976 old = real_mount(old_path.mnt);
1977 p = real_mount(path->mnt);
1980 if (!check_mnt(p) || !check_mnt(old))
1983 if (old->mnt.mnt_flags & MNT_LOCKED)
1987 if (old_path.dentry != old_path.mnt->mnt_root)
1990 if (!mnt_has_parent(old))
1993 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1994 S_ISDIR(old_path.dentry->d_inode->i_mode))
1997 * Don't move a mount residing in a shared parent.
1999 if (IS_MNT_SHARED(old->mnt_parent))
2002 * Don't move a mount tree containing unbindable mounts to a destination
2003 * mount which is shared.
2005 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
2008 for (; mnt_has_parent(p); p = p->mnt_parent)
2012 err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
2016 /* if the mount is moved, it should no longer be expire
2018 list_del_init(&old->mnt_expire);
2023 path_put(&parent_path);
2024 path_put(&old_path);
2028 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
2031 const char *subtype = strchr(fstype, '.');
2040 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
2042 if (!mnt->mnt_sb->s_subtype)
2048 return ERR_PTR(err);
2052 * add a mount into a namespace's mount tree
2054 static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
2056 struct mountpoint *mp;
2057 struct mount *parent;
2060 mnt_flags &= ~MNT_INTERNAL_FLAGS;
2062 mp = lock_mount(path);
2066 parent = real_mount(path->mnt);
2068 if (unlikely(!check_mnt(parent))) {
2069 /* that's acceptable only for automounts done in private ns */
2070 if (!(mnt_flags & MNT_SHRINKABLE))
2072 /* ... and for those we'd better have mountpoint still alive */
2073 if (!parent->mnt_ns)
2077 /* Refuse the same filesystem on the same mount point */
2079 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
2080 path->mnt->mnt_root == path->dentry)
2084 if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
2087 newmnt->mnt.mnt_flags = mnt_flags;
2088 err = graft_tree(newmnt, parent, mp);
2096 * create a new mount for userspace and request it to be added into the
2099 static int do_new_mount(struct path *path, const char *fstype, int flags,
2100 int mnt_flags, const char *name, void *data)
2102 struct file_system_type *type;
2103 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2104 struct vfsmount *mnt;
2110 type = get_fs_type(fstype);
2114 if (user_ns != &init_user_ns) {
2115 if (!(type->fs_flags & FS_USERNS_MOUNT)) {
2116 put_filesystem(type);
2119 /* Only in special cases allow devices from mounts
2120 * created outside the initial user namespace.
2122 if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
2124 mnt_flags |= MNT_NODEV;
2128 mnt = vfs_kern_mount(type, flags, name, data);
2129 if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
2130 !mnt->mnt_sb->s_subtype)
2131 mnt = fs_set_subtype(mnt, fstype);
2133 put_filesystem(type);
2135 return PTR_ERR(mnt);
2137 err = do_add_mount(real_mount(mnt), path, mnt_flags);
2143 int finish_automount(struct vfsmount *m, struct path *path)
2145 struct mount *mnt = real_mount(m);
2147 /* The new mount record should have at least 2 refs to prevent it being
2148 * expired before we get a chance to add it
2150 BUG_ON(mnt_get_count(mnt) < 2);
2152 if (m->mnt_sb == path->mnt->mnt_sb &&
2153 m->mnt_root == path->dentry) {
2158 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2162 /* remove m from any expiration list it may be on */
2163 if (!list_empty(&mnt->mnt_expire)) {
2165 list_del_init(&mnt->mnt_expire);
2174 * mnt_set_expiry - Put a mount on an expiration list
2175 * @mnt: The mount to list.
2176 * @expiry_list: The list to add the mount to.
2178 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2182 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2186 EXPORT_SYMBOL(mnt_set_expiry);
2189 * process a list of expirable mountpoints with the intent of discarding any
2190 * mountpoints that aren't in use and haven't been touched since last we came
2193 void mark_mounts_for_expiry(struct list_head *mounts)
2195 struct mount *mnt, *next;
2196 LIST_HEAD(graveyard);
2198 if (list_empty(mounts))
2204 /* extract from the expiration list every vfsmount that matches the
2205 * following criteria:
2206 * - only referenced by its parent vfsmount
2207 * - still marked for expiry (marked on the last call here; marks are
2208 * cleared by mntput())
2210 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2211 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2212 propagate_mount_busy(mnt, 1))
2214 list_move(&mnt->mnt_expire, &graveyard);
2216 while (!list_empty(&graveyard)) {
2217 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2218 touch_mnt_namespace(mnt->mnt_ns);
2219 umount_tree(mnt, 1);
2221 unlock_mount_hash();
2225 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2228 * Ripoff of 'select_parent()'
2230 * search the list of submounts for a given mountpoint, and move any
2231 * shrinkable submounts to the 'graveyard' list.
2233 static int select_submounts(struct mount *parent, struct list_head *graveyard)
2235 struct mount *this_parent = parent;
2236 struct list_head *next;
2240 next = this_parent->mnt_mounts.next;
2242 while (next != &this_parent->mnt_mounts) {
2243 struct list_head *tmp = next;
2244 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2247 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2250 * Descend a level if the d_mounts list is non-empty.
2252 if (!list_empty(&mnt->mnt_mounts)) {
2257 if (!propagate_mount_busy(mnt, 1)) {
2258 list_move_tail(&mnt->mnt_expire, graveyard);
2263 * All done at this level ... ascend and resume the search
2265 if (this_parent != parent) {
2266 next = this_parent->mnt_child.next;
2267 this_parent = this_parent->mnt_parent;
2274 * process a list of expirable mountpoints with the intent of discarding any
2275 * submounts of a specific parent mountpoint
2277 * mount_lock must be held for write
2279 static void shrink_submounts(struct mount *mnt)
2281 LIST_HEAD(graveyard);
2284 /* extract submounts of 'mountpoint' from the expiration list */
2285 while (select_submounts(mnt, &graveyard)) {
2286 while (!list_empty(&graveyard)) {
2287 m = list_first_entry(&graveyard, struct mount,
2289 touch_mnt_namespace(m->mnt_ns);
2296 * Some copy_from_user() implementations do not return the exact number of
2297 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2298 * Note that this function differs from copy_from_user() in that it will oops
2299 * on bad values of `to', rather than returning a short copy.
2301 static long exact_copy_from_user(void *to, const void __user * from,
2305 const char __user *f = from;
2308 if (!access_ok(VERIFY_READ, from, n))
2312 if (__get_user(c, f)) {
2323 int copy_mount_options(const void __user * data, unsigned long *where)
2333 if (!(page = __get_free_page(GFP_KERNEL)))
2336 /* We only care that *some* data at the address the user
2337 * gave us is valid. Just in case, we'll zero
2338 * the remainder of the page.
2340 /* copy_from_user cannot cross TASK_SIZE ! */
2341 size = TASK_SIZE - (unsigned long)data;
2342 if (size > PAGE_SIZE)
2345 i = size - exact_copy_from_user((void *)page, data, size);
2351 memset((char *)page + i, 0, PAGE_SIZE - i);
2356 int copy_mount_string(const void __user *data, char **where)
2365 tmp = strndup_user(data, PAGE_SIZE);
2367 return PTR_ERR(tmp);
2374 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2375 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2377 * data is a (void *) that can point to any structure up to
2378 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2379 * information (or be NULL).
2381 * Pre-0.97 versions of mount() didn't have a flags word.
2382 * When the flags word was introduced its top half was required
2383 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2384 * Therefore, if this magic number is present, it carries no information
2385 * and must be discarded.
2387 long do_mount(const char *dev_name, const char *dir_name,
2388 const char *type_page, unsigned long flags, void *data_page)
2395 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2396 flags &= ~MS_MGC_MSK;
2398 /* Basic sanity checks */
2400 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2404 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2406 /* ... and get the mountpoint */
2407 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2411 retval = security_sb_mount(dev_name, &path,
2412 type_page, flags, data_page);
2413 if (!retval && !may_mount())
2418 /* Default to relatime unless overriden */
2419 if (!(flags & MS_NOATIME))
2420 mnt_flags |= MNT_RELATIME;
2422 /* Separate the per-mountpoint flags */
2423 if (flags & MS_NOSUID)
2424 mnt_flags |= MNT_NOSUID;
2425 if (flags & MS_NODEV)
2426 mnt_flags |= MNT_NODEV;
2427 if (flags & MS_NOEXEC)
2428 mnt_flags |= MNT_NOEXEC;
2429 if (flags & MS_NOATIME)
2430 mnt_flags |= MNT_NOATIME;
2431 if (flags & MS_NODIRATIME)
2432 mnt_flags |= MNT_NODIRATIME;
2433 if (flags & MS_STRICTATIME)
2434 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2435 if (flags & MS_RDONLY)
2436 mnt_flags |= MNT_READONLY;
2438 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2439 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2442 if (flags & MS_REMOUNT)
2443 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2445 else if (flags & MS_BIND)
2446 retval = do_loopback(&path, dev_name, flags & MS_REC);
2447 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2448 retval = do_change_type(&path, flags);
2449 else if (flags & MS_MOVE)
2450 retval = do_move_mount(&path, dev_name);
2452 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2453 dev_name, data_page);
2459 static void free_mnt_ns(struct mnt_namespace *ns)
2461 proc_free_inum(ns->proc_inum);
2462 put_user_ns(ns->user_ns);
2467 * Assign a sequence number so we can detect when we attempt to bind
2468 * mount a reference to an older mount namespace into the current
2469 * mount namespace, preventing reference counting loops. A 64bit
2470 * number incrementing at 10Ghz will take 12,427 years to wrap which
2471 * is effectively never, so we can ignore the possibility.
2473 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
2475 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
2477 struct mnt_namespace *new_ns;
2480 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2482 return ERR_PTR(-ENOMEM);
2483 ret = proc_alloc_inum(&new_ns->proc_inum);
2486 return ERR_PTR(ret);
2488 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
2489 atomic_set(&new_ns->count, 1);
2490 new_ns->root = NULL;
2491 INIT_LIST_HEAD(&new_ns->list);
2492 init_waitqueue_head(&new_ns->poll);
2494 new_ns->user_ns = get_user_ns(user_ns);
2498 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2499 struct user_namespace *user_ns, struct fs_struct *new_fs)
2501 struct mnt_namespace *new_ns;
2502 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2503 struct mount *p, *q;
2510 if (likely(!(flags & CLONE_NEWNS))) {
2517 new_ns = alloc_mnt_ns(user_ns);
2522 /* First pass: copy the tree topology */
2523 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
2524 if (user_ns != ns->user_ns)
2525 copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
2526 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
2529 free_mnt_ns(new_ns);
2530 return ERR_CAST(new);
2533 list_add_tail(&new_ns->list, &new->mnt_list);
2536 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2537 * as belonging to new namespace. We have already acquired a private
2538 * fs_struct, so tsk->fs->lock is not needed.
2545 if (&p->mnt == new_fs->root.mnt) {
2546 new_fs->root.mnt = mntget(&q->mnt);
2549 if (&p->mnt == new_fs->pwd.mnt) {
2550 new_fs->pwd.mnt = mntget(&q->mnt);
2554 p = next_mnt(p, old);
2555 q = next_mnt(q, new);
2558 while (p->mnt.mnt_root != q->mnt.mnt_root)
2559 p = next_mnt(p, old);
2572 * create_mnt_ns - creates a private namespace and adds a root filesystem
2573 * @mnt: pointer to the new root filesystem mountpoint
2575 static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
2577 struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
2578 if (!IS_ERR(new_ns)) {
2579 struct mount *mnt = real_mount(m);
2580 mnt->mnt_ns = new_ns;
2582 list_add(&mnt->mnt_list, &new_ns->list);
2589 struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
2591 struct mnt_namespace *ns;
2592 struct super_block *s;
2596 ns = create_mnt_ns(mnt);
2598 return ERR_CAST(ns);
2600 err = vfs_path_lookup(mnt->mnt_root, mnt,
2601 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
2606 return ERR_PTR(err);
2608 /* trade a vfsmount reference for active sb one */
2609 s = path.mnt->mnt_sb;
2610 atomic_inc(&s->s_active);
2612 /* lock the sucker */
2613 down_write(&s->s_umount);
2614 /* ... and return the root of (sub)tree on it */
2617 EXPORT_SYMBOL(mount_subtree);
2619 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2620 char __user *, type, unsigned long, flags, void __user *, data)
2624 struct filename *kernel_dir;
2626 unsigned long data_page;
2628 ret = copy_mount_string(type, &kernel_type);
2632 kernel_dir = getname(dir_name);
2633 if (IS_ERR(kernel_dir)) {
2634 ret = PTR_ERR(kernel_dir);
2638 ret = copy_mount_string(dev_name, &kernel_dev);
2642 ret = copy_mount_options(data, &data_page);
2646 ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
2647 (void *) data_page);
2649 free_page(data_page);
2653 putname(kernel_dir);
2661 * Return true if path is reachable from root
2663 * namespace_sem or mount_lock is held
2665 bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
2666 const struct path *root)
2668 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
2669 dentry = mnt->mnt_mountpoint;
2670 mnt = mnt->mnt_parent;
2672 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
2675 int path_is_under(struct path *path1, struct path *path2)
2678 read_seqlock_excl(&mount_lock);
2679 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
2680 read_sequnlock_excl(&mount_lock);
2683 EXPORT_SYMBOL(path_is_under);
2686 * pivot_root Semantics:
2687 * Moves the root file system of the current process to the directory put_old,
2688 * makes new_root as the new root file system of the current process, and sets
2689 * root/cwd of all processes which had them on the current root to new_root.
2692 * The new_root and put_old must be directories, and must not be on the
2693 * same file system as the current process root. The put_old must be
2694 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2695 * pointed to by put_old must yield the same directory as new_root. No other
2696 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2698 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2699 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2700 * in this situation.
2703 * - we don't move root/cwd if they are not at the root (reason: if something
2704 * cared enough to change them, it's probably wrong to force them elsewhere)
2705 * - it's okay to pick a root that isn't the root of a file system, e.g.
2706 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2707 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2710 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2711 const char __user *, put_old)
2713 struct path new, old, parent_path, root_parent, root;
2714 struct mount *new_mnt, *root_mnt, *old_mnt;
2715 struct mountpoint *old_mp, *root_mp;
2721 error = user_path_dir(new_root, &new);
2725 error = user_path_dir(put_old, &old);
2729 error = security_sb_pivotroot(&old, &new);
2733 get_fs_root(current->fs, &root);
2734 old_mp = lock_mount(&old);
2735 error = PTR_ERR(old_mp);
2740 new_mnt = real_mount(new.mnt);
2741 root_mnt = real_mount(root.mnt);
2742 old_mnt = real_mount(old.mnt);
2743 if (IS_MNT_SHARED(old_mnt) ||
2744 IS_MNT_SHARED(new_mnt->mnt_parent) ||
2745 IS_MNT_SHARED(root_mnt->mnt_parent))
2747 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
2749 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
2752 if (d_unlinked(new.dentry))
2755 if (new_mnt == root_mnt || old_mnt == root_mnt)
2756 goto out4; /* loop, on the same file system */
2758 if (root.mnt->mnt_root != root.dentry)
2759 goto out4; /* not a mountpoint */
2760 if (!mnt_has_parent(root_mnt))
2761 goto out4; /* not attached */
2762 root_mp = root_mnt->mnt_mp;
2763 if (new.mnt->mnt_root != new.dentry)
2764 goto out4; /* not a mountpoint */
2765 if (!mnt_has_parent(new_mnt))
2766 goto out4; /* not attached */
2767 /* make sure we can reach put_old from new_root */
2768 if (!is_path_reachable(old_mnt, old.dentry, &new))
2770 root_mp->m_count++; /* pin it so it won't go away */
2772 detach_mnt(new_mnt, &parent_path);
2773 detach_mnt(root_mnt, &root_parent);
2774 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
2775 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
2776 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2778 /* mount old root on put_old */
2779 attach_mnt(root_mnt, old_mnt, old_mp);
2780 /* mount new_root on / */
2781 attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
2782 touch_mnt_namespace(current->nsproxy->mnt_ns);
2783 unlock_mount_hash();
2784 chroot_fs_refs(&root, &new);
2785 put_mountpoint(root_mp);
2788 unlock_mount(old_mp);
2790 path_put(&root_parent);
2791 path_put(&parent_path);
2803 static void __init init_mount_tree(void)
2805 struct vfsmount *mnt;
2806 struct mnt_namespace *ns;
2808 struct file_system_type *type;
2810 type = get_fs_type("rootfs");
2812 panic("Can't find rootfs type");
2813 mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
2814 put_filesystem(type);
2816 panic("Can't create rootfs");
2818 ns = create_mnt_ns(mnt);
2820 panic("Can't allocate initial namespace");
2822 init_task.nsproxy->mnt_ns = ns;
2826 root.dentry = mnt->mnt_root;
2828 set_fs_pwd(current->fs, &root);
2829 set_fs_root(current->fs, &root);
2832 void __init mnt_init(void)
2837 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
2838 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2840 mount_hashtable = alloc_large_system_hash("Mount-cache",
2841 sizeof(struct hlist_head),
2844 &m_hash_shift, &m_hash_mask, 0, 0);
2845 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
2846 sizeof(struct hlist_head),
2849 &mp_hash_shift, &mp_hash_mask, 0, 0);
2851 if (!mount_hashtable || !mountpoint_hashtable)
2852 panic("Failed to allocate mount hash table\n");
2854 for (u = 0; u <= m_hash_mask; u++)
2855 INIT_HLIST_HEAD(&mount_hashtable[u]);
2856 for (u = 0; u <= mp_hash_mask; u++)
2857 INIT_HLIST_HEAD(&mountpoint_hashtable[u]);
2863 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2865 fs_kobj = kobject_create_and_add("fs", NULL);
2867 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2872 void put_mnt_ns(struct mnt_namespace *ns)
2874 if (!atomic_dec_and_test(&ns->count))
2876 drop_collected_mounts(&ns->root->mnt);
2880 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2882 struct vfsmount *mnt;
2883 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2886 * it is a longterm mount, don't release mnt until
2887 * we unmount before file sys is unregistered
2889 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
2893 EXPORT_SYMBOL_GPL(kern_mount_data);
2895 void kern_unmount(struct vfsmount *mnt)
2897 /* release long term mount so mount point can be released */
2898 if (!IS_ERR_OR_NULL(mnt)) {
2899 real_mount(mnt)->mnt_ns = NULL;
2900 synchronize_rcu(); /* yecchhh... */
2904 EXPORT_SYMBOL(kern_unmount);
2906 bool our_mnt(struct vfsmount *mnt)
2908 return check_mnt(real_mount(mnt));
2911 bool current_chrooted(void)
2913 /* Does the current process have a non-standard root */
2914 struct path ns_root;
2915 struct path fs_root;
2918 /* Find the namespace root */
2919 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
2920 ns_root.dentry = ns_root.mnt->mnt_root;
2922 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
2925 get_fs_root(current->fs, &fs_root);
2927 chrooted = !path_equal(&fs_root, &ns_root);
2935 bool fs_fully_visible(struct file_system_type *type)
2937 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
2939 bool visible = false;
2944 down_read(&namespace_sem);
2945 list_for_each_entry(mnt, &ns->list, mnt_list) {
2946 struct mount *child;
2947 if (mnt->mnt.mnt_sb->s_type != type)
2950 /* This mount is not fully visible if there are any child mounts
2951 * that cover anything except for empty directories.
2953 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2954 struct inode *inode = child->mnt_mountpoint->d_inode;
2955 if (!S_ISDIR(inode->i_mode))
2957 if (inode->i_nlink > 2)
2965 up_read(&namespace_sem);
2969 static void *mntns_get(struct task_struct *task)
2971 struct mnt_namespace *ns = NULL;
2972 struct nsproxy *nsproxy;
2975 nsproxy = task_nsproxy(task);
2977 ns = nsproxy->mnt_ns;
2985 static void mntns_put(void *ns)
2990 static int mntns_install(struct nsproxy *nsproxy, void *ns)
2992 struct fs_struct *fs = current->fs;
2993 struct mnt_namespace *mnt_ns = ns;
2996 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
2997 !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
2998 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
3005 put_mnt_ns(nsproxy->mnt_ns);
3006 nsproxy->mnt_ns = mnt_ns;
3009 root.mnt = &mnt_ns->root->mnt;
3010 root.dentry = mnt_ns->root->mnt.mnt_root;
3012 while(d_mountpoint(root.dentry) && follow_down_one(&root))
3015 /* Update the pwd and root */
3016 set_fs_pwd(fs, &root);
3017 set_fs_root(fs, &root);
3023 static unsigned int mntns_inum(void *ns)
3025 struct mnt_namespace *mnt_ns = ns;
3026 return mnt_ns->proc_inum;
3029 const struct proc_ns_operations mntns_operations = {
3031 .type = CLONE_NEWNS,
3034 .install = mntns_install,