4 * (C) Copyright Al Viro 2000, 2001
5 * Released under GPL v2.
7 * Based on code from fs/super.c, copyright Linus Torvalds and others.
11 #include <linux/syscalls.h>
12 #include <linux/export.h>
13 #include <linux/capability.h>
14 #include <linux/mnt_namespace.h>
15 #include <linux/user_namespace.h>
16 #include <linux/namei.h>
17 #include <linux/security.h>
18 #include <linux/idr.h>
19 #include <linux/acct.h> /* acct_auto_close_mnt */
20 #include <linux/init.h> /* init_rootfs */
21 #include <linux/fs_struct.h> /* get_fs_root et.al. */
22 #include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */
23 #include <linux/uaccess.h>
24 #include <linux/proc_ns.h>
25 #include <linux/magic.h>
26 #include <linux/bootmem.h>
30 static unsigned int m_hash_mask __read_mostly;
31 static unsigned int m_hash_shift __read_mostly;
32 static unsigned int mp_hash_mask __read_mostly;
33 static unsigned int mp_hash_shift __read_mostly;
35 static __initdata unsigned long mhash_entries;
36 static int __init set_mhash_entries(char *str)
40 mhash_entries = simple_strtoul(str, &str, 0);
43 __setup("mhash_entries=", set_mhash_entries);
45 static __initdata unsigned long mphash_entries;
46 static int __init set_mphash_entries(char *str)
50 mphash_entries = simple_strtoul(str, &str, 0);
53 __setup("mphash_entries=", set_mphash_entries);
56 static DEFINE_IDA(mnt_id_ida);
57 static DEFINE_IDA(mnt_group_ida);
58 static DEFINE_SPINLOCK(mnt_id_lock);
59 static int mnt_id_start = 0;
60 static int mnt_group_start = 1;
62 static struct list_head *mount_hashtable __read_mostly;
63 static struct hlist_head *mountpoint_hashtable __read_mostly;
64 static struct kmem_cache *mnt_cache __read_mostly;
65 static DECLARE_RWSEM(namespace_sem);
68 struct kobject *fs_kobj;
69 EXPORT_SYMBOL_GPL(fs_kobj);
72 * vfsmount lock may be taken for read to prevent changes to the
73 * vfsmount hash, ie. during mountpoint lookups or walking back
76 * It should be taken for write in all cases where the vfsmount
77 * tree or hash is modified or when a vfsmount structure is modified.
79 __cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock);
81 static inline struct list_head *m_hash(struct vfsmount *mnt, struct dentry *dentry)
83 unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
84 tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
85 tmp = tmp + (tmp >> m_hash_shift);
86 return &mount_hashtable[tmp & m_hash_mask];
89 static inline struct hlist_head *mp_hash(struct dentry *dentry)
91 unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES);
92 tmp = tmp + (tmp >> mp_hash_shift);
93 return &mountpoint_hashtable[tmp & mp_hash_mask];
97 * allocation is serialized by namespace_sem, but we need the spinlock to
98 * serialize with freeing.
100 static int mnt_alloc_id(struct mount *mnt)
105 ida_pre_get(&mnt_id_ida, GFP_KERNEL);
106 spin_lock(&mnt_id_lock);
107 res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
109 mnt_id_start = mnt->mnt_id + 1;
110 spin_unlock(&mnt_id_lock);
117 static void mnt_free_id(struct mount *mnt)
119 int id = mnt->mnt_id;
120 spin_lock(&mnt_id_lock);
121 ida_remove(&mnt_id_ida, id);
122 if (mnt_id_start > id)
124 spin_unlock(&mnt_id_lock);
128 * Allocate a new peer group ID
130 * mnt_group_ida is protected by namespace_sem
132 static int mnt_alloc_group_id(struct mount *mnt)
136 if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
139 res = ida_get_new_above(&mnt_group_ida,
143 mnt_group_start = mnt->mnt_group_id + 1;
149 * Release a peer group ID
151 void mnt_release_group_id(struct mount *mnt)
153 int id = mnt->mnt_group_id;
154 ida_remove(&mnt_group_ida, id);
155 if (mnt_group_start > id)
156 mnt_group_start = id;
157 mnt->mnt_group_id = 0;
161 * vfsmount lock must be held for read
163 static inline void mnt_add_count(struct mount *mnt, int n)
166 this_cpu_add(mnt->mnt_pcp->mnt_count, n);
175 * vfsmount lock must be held for write
177 unsigned int mnt_get_count(struct mount *mnt)
180 unsigned int count = 0;
183 for_each_possible_cpu(cpu) {
184 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
189 return mnt->mnt_count;
193 static struct mount *alloc_vfsmnt(const char *name)
195 struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
199 err = mnt_alloc_id(mnt);
204 mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
205 if (!mnt->mnt_devname)
210 mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
212 goto out_free_devname;
214 this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
217 mnt->mnt_writers = 0;
220 INIT_LIST_HEAD(&mnt->mnt_hash);
221 INIT_LIST_HEAD(&mnt->mnt_child);
222 INIT_LIST_HEAD(&mnt->mnt_mounts);
223 INIT_LIST_HEAD(&mnt->mnt_list);
224 INIT_LIST_HEAD(&mnt->mnt_expire);
225 INIT_LIST_HEAD(&mnt->mnt_share);
226 INIT_LIST_HEAD(&mnt->mnt_slave_list);
227 INIT_LIST_HEAD(&mnt->mnt_slave);
228 #ifdef CONFIG_FSNOTIFY
229 INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
236 kfree(mnt->mnt_devname);
241 kmem_cache_free(mnt_cache, mnt);
246 * Most r/o checks on a fs are for operations that take
247 * discrete amounts of time, like a write() or unlink().
248 * We must keep track of when those operations start
249 * (for permission checks) and when they end, so that
250 * we can determine when writes are able to occur to
254 * __mnt_is_readonly: check whether a mount is read-only
255 * @mnt: the mount to check for its write status
257 * This shouldn't be used directly ouside of the VFS.
258 * It does not guarantee that the filesystem will stay
259 * r/w, just that it is right *now*. This can not and
260 * should not be used in place of IS_RDONLY(inode).
261 * mnt_want/drop_write() will _keep_ the filesystem
264 int __mnt_is_readonly(struct vfsmount *mnt)
266 if (mnt->mnt_flags & MNT_READONLY)
268 if (mnt->mnt_sb->s_flags & MS_RDONLY)
272 EXPORT_SYMBOL_GPL(__mnt_is_readonly);
274 static inline void mnt_inc_writers(struct mount *mnt)
277 this_cpu_inc(mnt->mnt_pcp->mnt_writers);
283 static inline void mnt_dec_writers(struct mount *mnt)
286 this_cpu_dec(mnt->mnt_pcp->mnt_writers);
292 static unsigned int mnt_get_writers(struct mount *mnt)
295 unsigned int count = 0;
298 for_each_possible_cpu(cpu) {
299 count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
304 return mnt->mnt_writers;
308 static int mnt_is_readonly(struct vfsmount *mnt)
310 if (mnt->mnt_sb->s_readonly_remount)
312 /* Order wrt setting s_flags/s_readonly_remount in do_remount() */
314 return __mnt_is_readonly(mnt);
318 * Most r/o & frozen checks on a fs are for operations that take discrete
319 * amounts of time, like a write() or unlink(). We must keep track of when
320 * those operations start (for permission checks) and when they end, so that we
321 * can determine when writes are able to occur to a filesystem.
324 * __mnt_want_write - get write access to a mount without freeze protection
325 * @m: the mount on which to take a write
327 * This tells the low-level filesystem that a write is about to be performed to
328 * it, and makes sure that writes are allowed (mnt it read-write) before
329 * returning success. This operation does not protect against filesystem being
330 * frozen. When the write operation is finished, __mnt_drop_write() must be
331 * called. This is effectively a refcount.
333 int __mnt_want_write(struct vfsmount *m)
335 struct mount *mnt = real_mount(m);
339 mnt_inc_writers(mnt);
341 * The store to mnt_inc_writers must be visible before we pass
342 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
343 * incremented count after it has set MNT_WRITE_HOLD.
346 while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
349 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
350 * be set to match its requirements. So we must not load that until
351 * MNT_WRITE_HOLD is cleared.
354 if (mnt_is_readonly(m)) {
355 mnt_dec_writers(mnt);
364 * mnt_want_write - get write access to a mount
365 * @m: the mount on which to take a write
367 * This tells the low-level filesystem that a write is about to be performed to
368 * it, and makes sure that writes are allowed (mount is read-write, filesystem
369 * is not frozen) before returning success. When the write operation is
370 * finished, mnt_drop_write() must be called. This is effectively a refcount.
372 int mnt_want_write(struct vfsmount *m)
376 sb_start_write(m->mnt_sb);
377 ret = __mnt_want_write(m);
379 sb_end_write(m->mnt_sb);
382 EXPORT_SYMBOL_GPL(mnt_want_write);
385 * mnt_clone_write - get write access to a mount
386 * @mnt: the mount on which to take a write
388 * This is effectively like mnt_want_write, except
389 * it must only be used to take an extra write reference
390 * on a mountpoint that we already know has a write reference
391 * on it. This allows some optimisation.
393 * After finished, mnt_drop_write must be called as usual to
394 * drop the reference.
396 int mnt_clone_write(struct vfsmount *mnt)
398 /* superblock may be r/o */
399 if (__mnt_is_readonly(mnt))
402 mnt_inc_writers(real_mount(mnt));
406 EXPORT_SYMBOL_GPL(mnt_clone_write);
409 * __mnt_want_write_file - get write access to a file's mount
410 * @file: the file who's mount on which to take a write
412 * This is like __mnt_want_write, but it takes a file and can
413 * do some optimisations if the file is open for write already
415 int __mnt_want_write_file(struct file *file)
417 struct inode *inode = file_inode(file);
419 if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
420 return __mnt_want_write(file->f_path.mnt);
422 return mnt_clone_write(file->f_path.mnt);
426 * mnt_want_write_file - get write access to a file's mount
427 * @file: the file who's mount on which to take a write
429 * This is like mnt_want_write, but it takes a file and can
430 * do some optimisations if the file is open for write already
432 int mnt_want_write_file(struct file *file)
436 sb_start_write(file->f_path.mnt->mnt_sb);
437 ret = __mnt_want_write_file(file);
439 sb_end_write(file->f_path.mnt->mnt_sb);
442 EXPORT_SYMBOL_GPL(mnt_want_write_file);
445 * __mnt_drop_write - give up write access to a mount
446 * @mnt: the mount on which to give up write access
448 * Tells the low-level filesystem that we are done
449 * performing writes to it. Must be matched with
450 * __mnt_want_write() call above.
452 void __mnt_drop_write(struct vfsmount *mnt)
455 mnt_dec_writers(real_mount(mnt));
460 * mnt_drop_write - give up write access to a mount
461 * @mnt: the mount on which to give up write access
463 * Tells the low-level filesystem that we are done performing writes to it and
464 * also allows filesystem to be frozen again. Must be matched with
465 * mnt_want_write() call above.
467 void mnt_drop_write(struct vfsmount *mnt)
469 __mnt_drop_write(mnt);
470 sb_end_write(mnt->mnt_sb);
472 EXPORT_SYMBOL_GPL(mnt_drop_write);
474 void __mnt_drop_write_file(struct file *file)
476 __mnt_drop_write(file->f_path.mnt);
479 void mnt_drop_write_file(struct file *file)
481 mnt_drop_write(file->f_path.mnt);
483 EXPORT_SYMBOL(mnt_drop_write_file);
485 static int mnt_make_readonly(struct mount *mnt)
490 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
492 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
493 * should be visible before we do.
498 * With writers on hold, if this value is zero, then there are
499 * definitely no active writers (although held writers may subsequently
500 * increment the count, they'll have to wait, and decrement it after
501 * seeing MNT_READONLY).
503 * It is OK to have counter incremented on one CPU and decremented on
504 * another: the sum will add up correctly. The danger would be when we
505 * sum up each counter, if we read a counter before it is incremented,
506 * but then read another CPU's count which it has been subsequently
507 * decremented from -- we would see more decrements than we should.
508 * MNT_WRITE_HOLD protects against this scenario, because
509 * mnt_want_write first increments count, then smp_mb, then spins on
510 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
511 * we're counting up here.
513 if (mnt_get_writers(mnt) > 0)
516 mnt->mnt.mnt_flags |= MNT_READONLY;
518 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
519 * that become unheld will see MNT_READONLY.
522 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
527 static void __mnt_unmake_readonly(struct mount *mnt)
530 mnt->mnt.mnt_flags &= ~MNT_READONLY;
534 int sb_prepare_remount_readonly(struct super_block *sb)
539 /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
540 if (atomic_long_read(&sb->s_remove_count))
544 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
545 if (!(mnt->mnt.mnt_flags & MNT_READONLY)) {
546 mnt->mnt.mnt_flags |= MNT_WRITE_HOLD;
548 if (mnt_get_writers(mnt) > 0) {
554 if (!err && atomic_long_read(&sb->s_remove_count))
558 sb->s_readonly_remount = 1;
561 list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
562 if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD)
563 mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD;
570 static void free_vfsmnt(struct mount *mnt)
572 kfree(mnt->mnt_devname);
575 free_percpu(mnt->mnt_pcp);
577 kmem_cache_free(mnt_cache, mnt);
580 /* call under rcu_read_lock */
581 bool legitimize_mnt(struct vfsmount *bastard, unsigned seq)
584 if (read_seqretry(&mount_lock, seq))
588 mnt = real_mount(bastard);
589 mnt_add_count(mnt, 1);
590 if (likely(!read_seqretry(&mount_lock, seq)))
592 if (bastard->mnt_flags & MNT_SYNC_UMOUNT) {
593 mnt_add_count(mnt, -1);
603 * find the first mount at @dentry on vfsmount @mnt.
604 * call under rcu_read_lock()
606 struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry)
608 struct list_head *head = m_hash(mnt, dentry);
611 list_for_each_entry_rcu(p, head, mnt_hash)
612 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
618 * find the last mount at @dentry on vfsmount @mnt.
619 * mount_lock must be held.
621 struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)
623 struct list_head *head = m_hash(mnt, dentry);
624 struct mount *p, *res = NULL;
626 list_for_each_entry(p, head, mnt_hash)
627 if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry)
632 list_for_each_entry_continue(p, head, mnt_hash) {
633 if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry)
641 * lookup_mnt - Return the first child mount mounted at path
643 * "First" means first mounted chronologically. If you create the
646 * mount /dev/sda1 /mnt
647 * mount /dev/sda2 /mnt
648 * mount /dev/sda3 /mnt
650 * Then lookup_mnt() on the base /mnt dentry in the root mount will
651 * return successively the root dentry and vfsmount of /dev/sda1, then
652 * /dev/sda2, then /dev/sda3, then NULL.
654 * lookup_mnt takes a reference to the found vfsmount.
656 struct vfsmount *lookup_mnt(struct path *path)
658 struct mount *child_mnt;
664 seq = read_seqbegin(&mount_lock);
665 child_mnt = __lookup_mnt(path->mnt, path->dentry);
666 m = child_mnt ? &child_mnt->mnt : NULL;
667 } while (!legitimize_mnt(m, seq));
672 static struct mountpoint *new_mountpoint(struct dentry *dentry)
674 struct hlist_head *chain = mp_hash(dentry);
675 struct mountpoint *mp;
678 hlist_for_each_entry(mp, chain, m_hash) {
679 if (mp->m_dentry == dentry) {
680 /* might be worth a WARN_ON() */
681 if (d_unlinked(dentry))
682 return ERR_PTR(-ENOENT);
688 mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
690 return ERR_PTR(-ENOMEM);
692 ret = d_set_mounted(dentry);
698 mp->m_dentry = dentry;
700 hlist_add_head(&mp->m_hash, chain);
704 static void put_mountpoint(struct mountpoint *mp)
706 if (!--mp->m_count) {
707 struct dentry *dentry = mp->m_dentry;
708 spin_lock(&dentry->d_lock);
709 dentry->d_flags &= ~DCACHE_MOUNTED;
710 spin_unlock(&dentry->d_lock);
711 hlist_del(&mp->m_hash);
716 static inline int check_mnt(struct mount *mnt)
718 return mnt->mnt_ns == current->nsproxy->mnt_ns;
722 * vfsmount lock must be held for write
724 static void touch_mnt_namespace(struct mnt_namespace *ns)
728 wake_up_interruptible(&ns->poll);
733 * vfsmount lock must be held for write
735 static void __touch_mnt_namespace(struct mnt_namespace *ns)
737 if (ns && ns->event != event) {
739 wake_up_interruptible(&ns->poll);
744 * vfsmount lock must be held for write
746 static void detach_mnt(struct mount *mnt, struct path *old_path)
748 old_path->dentry = mnt->mnt_mountpoint;
749 old_path->mnt = &mnt->mnt_parent->mnt;
750 mnt->mnt_parent = mnt;
751 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
752 list_del_init(&mnt->mnt_child);
753 list_del_init(&mnt->mnt_hash);
754 put_mountpoint(mnt->mnt_mp);
759 * vfsmount lock must be held for write
761 void mnt_set_mountpoint(struct mount *mnt,
762 struct mountpoint *mp,
763 struct mount *child_mnt)
766 mnt_add_count(mnt, 1); /* essentially, that's mntget */
767 child_mnt->mnt_mountpoint = dget(mp->m_dentry);
768 child_mnt->mnt_parent = mnt;
769 child_mnt->mnt_mp = mp;
773 * vfsmount lock must be held for write
775 static void attach_mnt(struct mount *mnt,
776 struct mount *parent,
777 struct mountpoint *mp)
779 mnt_set_mountpoint(parent, mp, mnt);
780 list_add(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
781 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
785 * vfsmount lock must be held for write
787 static void commit_tree(struct mount *mnt, struct mount *shadows)
789 struct mount *parent = mnt->mnt_parent;
792 struct mnt_namespace *n = parent->mnt_ns;
794 BUG_ON(parent == mnt);
796 list_add_tail(&head, &mnt->mnt_list);
797 list_for_each_entry(m, &head, mnt_list)
800 list_splice(&head, n->list.prev);
803 list_add(&mnt->mnt_hash, &shadows->mnt_hash);
805 list_add(&mnt->mnt_hash,
806 m_hash(&parent->mnt, mnt->mnt_mountpoint));
807 list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
808 touch_mnt_namespace(n);
811 static struct mount *next_mnt(struct mount *p, struct mount *root)
813 struct list_head *next = p->mnt_mounts.next;
814 if (next == &p->mnt_mounts) {
818 next = p->mnt_child.next;
819 if (next != &p->mnt_parent->mnt_mounts)
824 return list_entry(next, struct mount, mnt_child);
827 static struct mount *skip_mnt_tree(struct mount *p)
829 struct list_head *prev = p->mnt_mounts.prev;
830 while (prev != &p->mnt_mounts) {
831 p = list_entry(prev, struct mount, mnt_child);
832 prev = p->mnt_mounts.prev;
838 vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
844 return ERR_PTR(-ENODEV);
846 mnt = alloc_vfsmnt(name);
848 return ERR_PTR(-ENOMEM);
850 if (flags & MS_KERNMOUNT)
851 mnt->mnt.mnt_flags = MNT_INTERNAL;
853 root = mount_fs(type, flags, name, data);
856 return ERR_CAST(root);
859 mnt->mnt.mnt_root = root;
860 mnt->mnt.mnt_sb = root->d_sb;
861 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
862 mnt->mnt_parent = mnt;
864 list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts);
868 EXPORT_SYMBOL_GPL(vfs_kern_mount);
870 static struct mount *clone_mnt(struct mount *old, struct dentry *root,
873 struct super_block *sb = old->mnt.mnt_sb;
877 mnt = alloc_vfsmnt(old->mnt_devname);
879 return ERR_PTR(-ENOMEM);
881 if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE))
882 mnt->mnt_group_id = 0; /* not a peer of original */
884 mnt->mnt_group_id = old->mnt_group_id;
886 if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) {
887 err = mnt_alloc_group_id(mnt);
892 mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD;
893 /* Don't allow unprivileged users to change mount flags */
894 if ((flag & CL_UNPRIVILEGED) && (mnt->mnt.mnt_flags & MNT_READONLY))
895 mnt->mnt.mnt_flags |= MNT_LOCK_READONLY;
897 /* Don't allow unprivileged users to reveal what is under a mount */
898 if ((flag & CL_UNPRIVILEGED) && list_empty(&old->mnt_expire))
899 mnt->mnt.mnt_flags |= MNT_LOCKED;
901 atomic_inc(&sb->s_active);
902 mnt->mnt.mnt_sb = sb;
903 mnt->mnt.mnt_root = dget(root);
904 mnt->mnt_mountpoint = mnt->mnt.mnt_root;
905 mnt->mnt_parent = mnt;
907 list_add_tail(&mnt->mnt_instance, &sb->s_mounts);
910 if ((flag & CL_SLAVE) ||
911 ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) {
912 list_add(&mnt->mnt_slave, &old->mnt_slave_list);
913 mnt->mnt_master = old;
914 CLEAR_MNT_SHARED(mnt);
915 } else if (!(flag & CL_PRIVATE)) {
916 if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
917 list_add(&mnt->mnt_share, &old->mnt_share);
918 if (IS_MNT_SLAVE(old))
919 list_add(&mnt->mnt_slave, &old->mnt_slave);
920 mnt->mnt_master = old->mnt_master;
922 if (flag & CL_MAKE_SHARED)
925 /* stick the duplicate mount on the same expiry list
926 * as the original if that was on one */
927 if (flag & CL_EXPIRE) {
928 if (!list_empty(&old->mnt_expire))
929 list_add(&mnt->mnt_expire, &old->mnt_expire);
939 static void delayed_free(struct rcu_head *head)
941 struct mount *mnt = container_of(head, struct mount, mnt_rcu);
942 kfree(mnt->mnt_devname);
944 free_percpu(mnt->mnt_pcp);
946 kmem_cache_free(mnt_cache, mnt);
949 static void mntput_no_expire(struct mount *mnt)
953 mnt_add_count(mnt, -1);
954 if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */
959 if (mnt_get_count(mnt)) {
964 if (unlikely(mnt->mnt_pinned)) {
965 mnt_add_count(mnt, mnt->mnt_pinned + 1);
969 acct_auto_close_mnt(&mnt->mnt);
972 if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) {
977 mnt->mnt.mnt_flags |= MNT_DOOMED;
980 list_del(&mnt->mnt_instance);
984 * This probably indicates that somebody messed
985 * up a mnt_want/drop_write() pair. If this
986 * happens, the filesystem was probably unable
987 * to make r/w->r/o transitions.
990 * The locking used to deal with mnt_count decrement provides barriers,
991 * so mnt_get_writers() below is safe.
993 WARN_ON(mnt_get_writers(mnt));
994 fsnotify_vfsmount_delete(&mnt->mnt);
995 dput(mnt->mnt.mnt_root);
996 deactivate_super(mnt->mnt.mnt_sb);
998 call_rcu(&mnt->mnt_rcu, delayed_free);
1001 void mntput(struct vfsmount *mnt)
1004 struct mount *m = real_mount(mnt);
1005 /* avoid cacheline pingpong, hope gcc doesn't get "smart" */
1006 if (unlikely(m->mnt_expiry_mark))
1007 m->mnt_expiry_mark = 0;
1008 mntput_no_expire(m);
1011 EXPORT_SYMBOL(mntput);
1013 struct vfsmount *mntget(struct vfsmount *mnt)
1016 mnt_add_count(real_mount(mnt), 1);
1019 EXPORT_SYMBOL(mntget);
1021 void mnt_pin(struct vfsmount *mnt)
1024 real_mount(mnt)->mnt_pinned++;
1025 unlock_mount_hash();
1027 EXPORT_SYMBOL(mnt_pin);
1029 void mnt_unpin(struct vfsmount *m)
1031 struct mount *mnt = real_mount(m);
1033 if (mnt->mnt_pinned) {
1034 mnt_add_count(mnt, 1);
1037 unlock_mount_hash();
1039 EXPORT_SYMBOL(mnt_unpin);
1041 static inline void mangle(struct seq_file *m, const char *s)
1043 seq_escape(m, s, " \t\n\\");
1047 * Simple .show_options callback for filesystems which don't want to
1048 * implement more complex mount option showing.
1050 * See also save_mount_options().
1052 int generic_show_options(struct seq_file *m, struct dentry *root)
1054 const char *options;
1057 options = rcu_dereference(root->d_sb->s_options);
1059 if (options != NULL && options[0]) {
1067 EXPORT_SYMBOL(generic_show_options);
1070 * If filesystem uses generic_show_options(), this function should be
1071 * called from the fill_super() callback.
1073 * The .remount_fs callback usually needs to be handled in a special
1074 * way, to make sure, that previous options are not overwritten if the
1077 * Also note, that if the filesystem's .remount_fs function doesn't
1078 * reset all options to their default value, but changes only newly
1079 * given options, then the displayed options will not reflect reality
1082 void save_mount_options(struct super_block *sb, char *options)
1084 BUG_ON(sb->s_options);
1085 rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
1087 EXPORT_SYMBOL(save_mount_options);
1089 void replace_mount_options(struct super_block *sb, char *options)
1091 char *old = sb->s_options;
1092 rcu_assign_pointer(sb->s_options, options);
1098 EXPORT_SYMBOL(replace_mount_options);
1100 #ifdef CONFIG_PROC_FS
1101 /* iterator; we want it to have access to namespace_sem, thus here... */
1102 static void *m_start(struct seq_file *m, loff_t *pos)
1104 struct proc_mounts *p = proc_mounts(m);
1106 down_read(&namespace_sem);
1107 return seq_list_start(&p->ns->list, *pos);
1110 static void *m_next(struct seq_file *m, void *v, loff_t *pos)
1112 struct proc_mounts *p = proc_mounts(m);
1114 return seq_list_next(v, &p->ns->list, pos);
1117 static void m_stop(struct seq_file *m, void *v)
1119 up_read(&namespace_sem);
1122 static int m_show(struct seq_file *m, void *v)
1124 struct proc_mounts *p = proc_mounts(m);
1125 struct mount *r = list_entry(v, struct mount, mnt_list);
1126 return p->show(m, &r->mnt);
1129 const struct seq_operations mounts_op = {
1135 #endif /* CONFIG_PROC_FS */
1138 * may_umount_tree - check if a mount tree is busy
1139 * @mnt: root of mount tree
1141 * This is called to check if a tree of mounts has any
1142 * open files, pwds, chroots or sub mounts that are
1145 int may_umount_tree(struct vfsmount *m)
1147 struct mount *mnt = real_mount(m);
1148 int actual_refs = 0;
1149 int minimum_refs = 0;
1153 /* write lock needed for mnt_get_count */
1155 for (p = mnt; p; p = next_mnt(p, mnt)) {
1156 actual_refs += mnt_get_count(p);
1159 unlock_mount_hash();
1161 if (actual_refs > minimum_refs)
1167 EXPORT_SYMBOL(may_umount_tree);
1170 * may_umount - check if a mount point is busy
1171 * @mnt: root of mount
1173 * This is called to check if a mount point has any
1174 * open files, pwds, chroots or sub mounts. If the
1175 * mount has sub mounts this will return busy
1176 * regardless of whether the sub mounts are busy.
1178 * Doesn't take quota and stuff into account. IOW, in some cases it will
1179 * give false negatives. The main reason why it's here is that we need
1180 * a non-destructive way to look for easily umountable filesystems.
1182 int may_umount(struct vfsmount *mnt)
1185 down_read(&namespace_sem);
1187 if (propagate_mount_busy(real_mount(mnt), 2))
1189 unlock_mount_hash();
1190 up_read(&namespace_sem);
1194 EXPORT_SYMBOL(may_umount);
1196 static LIST_HEAD(unmounted); /* protected by namespace_sem */
1198 static void namespace_unlock(void)
1203 if (likely(list_empty(&unmounted))) {
1204 up_write(&namespace_sem);
1208 list_splice_init(&unmounted, &head);
1209 up_write(&namespace_sem);
1213 while (!list_empty(&head)) {
1214 mnt = list_first_entry(&head, struct mount, mnt_hash);
1215 list_del_init(&mnt->mnt_hash);
1216 if (mnt->mnt_ex_mountpoint.mnt)
1217 path_put(&mnt->mnt_ex_mountpoint);
1222 static inline void namespace_lock(void)
1224 down_write(&namespace_sem);
1228 * mount_lock must be held
1229 * namespace_sem must be held for write
1230 * how = 0 => just this tree, don't propagate
1231 * how = 1 => propagate; we know that nobody else has reference to any victims
1232 * how = 2 => lazy umount
1234 void umount_tree(struct mount *mnt, int how)
1236 LIST_HEAD(tmp_list);
1239 for (p = mnt; p; p = next_mnt(p, mnt))
1240 list_move(&p->mnt_hash, &tmp_list);
1243 propagate_umount(&tmp_list);
1245 list_for_each_entry(p, &tmp_list, mnt_hash) {
1246 list_del_init(&p->mnt_expire);
1247 list_del_init(&p->mnt_list);
1248 __touch_mnt_namespace(p->mnt_ns);
1251 p->mnt.mnt_flags |= MNT_SYNC_UMOUNT;
1252 list_del_init(&p->mnt_child);
1253 if (mnt_has_parent(p)) {
1254 put_mountpoint(p->mnt_mp);
1255 /* move the reference to mountpoint into ->mnt_ex_mountpoint */
1256 p->mnt_ex_mountpoint.dentry = p->mnt_mountpoint;
1257 p->mnt_ex_mountpoint.mnt = &p->mnt_parent->mnt;
1258 p->mnt_mountpoint = p->mnt.mnt_root;
1262 change_mnt_propagation(p, MS_PRIVATE);
1264 list_splice(&tmp_list, &unmounted);
1267 static void shrink_submounts(struct mount *mnt);
1269 static int do_umount(struct mount *mnt, int flags)
1271 struct super_block *sb = mnt->mnt.mnt_sb;
1274 retval = security_sb_umount(&mnt->mnt, flags);
1279 * Allow userspace to request a mountpoint be expired rather than
1280 * unmounting unconditionally. Unmount only happens if:
1281 * (1) the mark is already set (the mark is cleared by mntput())
1282 * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount]
1284 if (flags & MNT_EXPIRE) {
1285 if (&mnt->mnt == current->fs->root.mnt ||
1286 flags & (MNT_FORCE | MNT_DETACH))
1290 * probably don't strictly need the lock here if we examined
1291 * all race cases, but it's a slowpath.
1294 if (mnt_get_count(mnt) != 2) {
1295 unlock_mount_hash();
1298 unlock_mount_hash();
1300 if (!xchg(&mnt->mnt_expiry_mark, 1))
1305 * If we may have to abort operations to get out of this
1306 * mount, and they will themselves hold resources we must
1307 * allow the fs to do things. In the Unix tradition of
1308 * 'Gee thats tricky lets do it in userspace' the umount_begin
1309 * might fail to complete on the first run through as other tasks
1310 * must return, and the like. Thats for the mount program to worry
1311 * about for the moment.
1314 if (flags & MNT_FORCE && sb->s_op->umount_begin) {
1315 sb->s_op->umount_begin(sb);
1319 * No sense to grab the lock for this test, but test itself looks
1320 * somewhat bogus. Suggestions for better replacement?
1321 * Ho-hum... In principle, we might treat that as umount + switch
1322 * to rootfs. GC would eventually take care of the old vfsmount.
1323 * Actually it makes sense, especially if rootfs would contain a
1324 * /reboot - static binary that would close all descriptors and
1325 * call reboot(9). Then init(8) could umount root and exec /reboot.
1327 if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
1329 * Special case for "unmounting" root ...
1330 * we just try to remount it readonly.
1332 down_write(&sb->s_umount);
1333 if (!(sb->s_flags & MS_RDONLY))
1334 retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
1335 up_write(&sb->s_umount);
1343 if (flags & MNT_DETACH) {
1344 if (!list_empty(&mnt->mnt_list))
1345 umount_tree(mnt, 2);
1348 shrink_submounts(mnt);
1350 if (!propagate_mount_busy(mnt, 2)) {
1351 if (!list_empty(&mnt->mnt_list))
1352 umount_tree(mnt, 1);
1356 unlock_mount_hash();
1362 * Is the caller allowed to modify his namespace?
1364 static inline bool may_mount(void)
1366 return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN);
1370 * Now umount can handle mount points as well as block devices.
1371 * This is important for filesystems which use unnamed block devices.
1373 * We now support a flag for forced unmount like the other 'big iron'
1374 * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD
1377 SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
1382 int lookup_flags = 0;
1384 if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
1390 if (!(flags & UMOUNT_NOFOLLOW))
1391 lookup_flags |= LOOKUP_FOLLOW;
1393 retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path);
1396 mnt = real_mount(path.mnt);
1398 if (path.dentry != path.mnt->mnt_root)
1400 if (!check_mnt(mnt))
1402 if (mnt->mnt.mnt_flags & MNT_LOCKED)
1405 retval = do_umount(mnt, flags);
1407 /* we mustn't call path_put() as that would clear mnt_expiry_mark */
1409 mntput_no_expire(mnt);
1414 #ifdef __ARCH_WANT_SYS_OLDUMOUNT
1417 * The 2.0 compatible umount. No flags.
1419 SYSCALL_DEFINE1(oldumount, char __user *, name)
1421 return sys_umount(name, 0);
1426 static bool is_mnt_ns_file(struct dentry *dentry)
1428 /* Is this a proxy for a mount namespace? */
1429 struct inode *inode = dentry->d_inode;
1432 if (!proc_ns_inode(inode))
1435 ei = get_proc_ns(inode);
1436 if (ei->ns_ops != &mntns_operations)
1442 static bool mnt_ns_loop(struct dentry *dentry)
1444 /* Could bind mounting the mount namespace inode cause a
1445 * mount namespace loop?
1447 struct mnt_namespace *mnt_ns;
1448 if (!is_mnt_ns_file(dentry))
1451 mnt_ns = get_proc_ns(dentry->d_inode)->ns;
1452 return current->nsproxy->mnt_ns->seq >= mnt_ns->seq;
1455 struct mount *copy_tree(struct mount *mnt, struct dentry *dentry,
1458 struct mount *res, *p, *q, *r, *parent;
1460 if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt))
1461 return ERR_PTR(-EINVAL);
1463 if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry))
1464 return ERR_PTR(-EINVAL);
1466 res = q = clone_mnt(mnt, dentry, flag);
1470 q->mnt.mnt_flags &= ~MNT_LOCKED;
1471 q->mnt_mountpoint = mnt->mnt_mountpoint;
1474 list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1476 if (!is_subdir(r->mnt_mountpoint, dentry))
1479 for (s = r; s; s = next_mnt(s, r)) {
1480 if (!(flag & CL_COPY_UNBINDABLE) &&
1481 IS_MNT_UNBINDABLE(s)) {
1482 s = skip_mnt_tree(s);
1485 if (!(flag & CL_COPY_MNT_NS_FILE) &&
1486 is_mnt_ns_file(s->mnt.mnt_root)) {
1487 s = skip_mnt_tree(s);
1490 while (p != s->mnt_parent) {
1496 q = clone_mnt(p, p->mnt.mnt_root, flag);
1500 list_add_tail(&q->mnt_list, &res->mnt_list);
1501 attach_mnt(q, parent, p->mnt_mp);
1502 unlock_mount_hash();
1509 umount_tree(res, 0);
1510 unlock_mount_hash();
1515 /* Caller should check returned pointer for errors */
1517 struct vfsmount *collect_mounts(struct path *path)
1521 tree = copy_tree(real_mount(path->mnt), path->dentry,
1522 CL_COPY_ALL | CL_PRIVATE);
1525 return ERR_CAST(tree);
1529 void drop_collected_mounts(struct vfsmount *mnt)
1533 umount_tree(real_mount(mnt), 0);
1534 unlock_mount_hash();
1538 int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
1539 struct vfsmount *root)
1542 int res = f(root, arg);
1545 list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) {
1546 res = f(&mnt->mnt, arg);
1553 static void cleanup_group_ids(struct mount *mnt, struct mount *end)
1557 for (p = mnt; p != end; p = next_mnt(p, mnt)) {
1558 if (p->mnt_group_id && !IS_MNT_SHARED(p))
1559 mnt_release_group_id(p);
1563 static int invent_group_ids(struct mount *mnt, bool recurse)
1567 for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) {
1568 if (!p->mnt_group_id && !IS_MNT_SHARED(p)) {
1569 int err = mnt_alloc_group_id(p);
1571 cleanup_group_ids(mnt, p);
1581 * @source_mnt : mount tree to be attached
1582 * @nd : place the mount tree @source_mnt is attached
1583 * @parent_nd : if non-null, detach the source_mnt from its parent and
1584 * store the parent mount and mountpoint dentry.
1585 * (done when source_mnt is moved)
1587 * NOTE: in the table below explains the semantics when a source mount
1588 * of a given type is attached to a destination mount of a given type.
1589 * ---------------------------------------------------------------------------
1590 * | BIND MOUNT OPERATION |
1591 * |**************************************************************************
1592 * | source-->| shared | private | slave | unbindable |
1596 * |**************************************************************************
1597 * | shared | shared (++) | shared (+) | shared(+++)| invalid |
1599 * |non-shared| shared (+) | private | slave (*) | invalid |
1600 * ***************************************************************************
1601 * A bind operation clones the source mount and mounts the clone on the
1602 * destination mount.
1604 * (++) the cloned mount is propagated to all the mounts in the propagation
1605 * tree of the destination mount and the cloned mount is added to
1606 * the peer group of the source mount.
1607 * (+) the cloned mount is created under the destination mount and is marked
1608 * as shared. The cloned mount is added to the peer group of the source
1610 * (+++) the mount is propagated to all the mounts in the propagation tree
1611 * of the destination mount and the cloned mount is made slave
1612 * of the same master as that of the source mount. The cloned mount
1613 * is marked as 'shared and slave'.
1614 * (*) the cloned mount is made a slave of the same master as that of the
1617 * ---------------------------------------------------------------------------
1618 * | MOVE MOUNT OPERATION |
1619 * |**************************************************************************
1620 * | source-->| shared | private | slave | unbindable |
1624 * |**************************************************************************
1625 * | shared | shared (+) | shared (+) | shared(+++) | invalid |
1627 * |non-shared| shared (+*) | private | slave (*) | unbindable |
1628 * ***************************************************************************
1630 * (+) the mount is moved to the destination. And is then propagated to
1631 * all the mounts in the propagation tree of the destination mount.
1632 * (+*) the mount is moved to the destination.
1633 * (+++) the mount is moved to the destination and is then propagated to
1634 * all the mounts belonging to the destination mount's propagation tree.
1635 * the mount is marked as 'shared and slave'.
1636 * (*) the mount continues to be a slave at the new location.
1638 * if the source mount is a tree, the operations explained above is
1639 * applied to each mount in the tree.
1640 * Must be called without spinlocks held, since this function can sleep
1643 static int attach_recursive_mnt(struct mount *source_mnt,
1644 struct mount *dest_mnt,
1645 struct mountpoint *dest_mp,
1646 struct path *parent_path)
1648 LIST_HEAD(tree_list);
1649 struct mount *child, *p;
1652 if (IS_MNT_SHARED(dest_mnt)) {
1653 err = invent_group_ids(source_mnt, true);
1656 err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list);
1658 goto out_cleanup_ids;
1660 for (p = source_mnt; p; p = next_mnt(p, source_mnt))
1666 detach_mnt(source_mnt, parent_path);
1667 attach_mnt(source_mnt, dest_mnt, dest_mp);
1668 touch_mnt_namespace(source_mnt->mnt_ns);
1670 mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
1671 commit_tree(source_mnt, NULL);
1674 list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
1676 list_del_init(&child->mnt_hash);
1677 q = __lookup_mnt_last(&child->mnt_parent->mnt,
1678 child->mnt_mountpoint);
1679 commit_tree(child, q);
1681 unlock_mount_hash();
1686 cleanup_group_ids(source_mnt, NULL);
1691 static struct mountpoint *lock_mount(struct path *path)
1693 struct vfsmount *mnt;
1694 struct dentry *dentry = path->dentry;
1696 mutex_lock(&dentry->d_inode->i_mutex);
1697 if (unlikely(cant_mount(dentry))) {
1698 mutex_unlock(&dentry->d_inode->i_mutex);
1699 return ERR_PTR(-ENOENT);
1702 mnt = lookup_mnt(path);
1704 struct mountpoint *mp = new_mountpoint(dentry);
1707 mutex_unlock(&dentry->d_inode->i_mutex);
1713 mutex_unlock(&path->dentry->d_inode->i_mutex);
1716 dentry = path->dentry = dget(mnt->mnt_root);
1720 static void unlock_mount(struct mountpoint *where)
1722 struct dentry *dentry = where->m_dentry;
1723 put_mountpoint(where);
1725 mutex_unlock(&dentry->d_inode->i_mutex);
1728 static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp)
1730 if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER)
1733 if (S_ISDIR(mp->m_dentry->d_inode->i_mode) !=
1734 S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode))
1737 return attach_recursive_mnt(mnt, p, mp, NULL);
1741 * Sanity check the flags to change_mnt_propagation.
1744 static int flags_to_propagation_type(int flags)
1746 int type = flags & ~(MS_REC | MS_SILENT);
1748 /* Fail if any non-propagation flags are set */
1749 if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1751 /* Only one propagation flag should be set */
1752 if (!is_power_of_2(type))
1758 * recursively change the type of the mountpoint.
1760 static int do_change_type(struct path *path, int flag)
1763 struct mount *mnt = real_mount(path->mnt);
1764 int recurse = flag & MS_REC;
1768 if (path->dentry != path->mnt->mnt_root)
1771 type = flags_to_propagation_type(flag);
1776 if (type == MS_SHARED) {
1777 err = invent_group_ids(mnt, recurse);
1783 for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
1784 change_mnt_propagation(m, type);
1785 unlock_mount_hash();
1792 static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
1794 struct mount *child;
1795 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
1796 if (!is_subdir(child->mnt_mountpoint, dentry))
1799 if (child->mnt.mnt_flags & MNT_LOCKED)
1806 * do loopback mount.
1808 static int do_loopback(struct path *path, const char *old_name,
1811 struct path old_path;
1812 struct mount *mnt = NULL, *old, *parent;
1813 struct mountpoint *mp;
1815 if (!old_name || !*old_name)
1817 err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path);
1822 if (mnt_ns_loop(old_path.dentry))
1825 mp = lock_mount(path);
1830 old = real_mount(old_path.mnt);
1831 parent = real_mount(path->mnt);
1834 if (IS_MNT_UNBINDABLE(old))
1837 if (!check_mnt(parent) || !check_mnt(old))
1840 if (!recurse && has_locked_children(old, old_path.dentry))
1844 mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
1846 mnt = clone_mnt(old, old_path.dentry, 0);
1853 mnt->mnt.mnt_flags &= ~MNT_LOCKED;
1855 err = graft_tree(mnt, parent, mp);
1858 umount_tree(mnt, 0);
1859 unlock_mount_hash();
1864 path_put(&old_path);
1868 static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
1871 int readonly_request = 0;
1873 if (ms_flags & MS_RDONLY)
1874 readonly_request = 1;
1875 if (readonly_request == __mnt_is_readonly(mnt))
1878 if (mnt->mnt_flags & MNT_LOCK_READONLY)
1881 if (readonly_request)
1882 error = mnt_make_readonly(real_mount(mnt));
1884 __mnt_unmake_readonly(real_mount(mnt));
1889 * change filesystem flags. dir should be a physical root of filesystem.
1890 * If you've mounted a non-root directory somewhere and want to do remount
1891 * on it - tough luck.
1893 static int do_remount(struct path *path, int flags, int mnt_flags,
1897 struct super_block *sb = path->mnt->mnt_sb;
1898 struct mount *mnt = real_mount(path->mnt);
1900 if (!check_mnt(mnt))
1903 if (path->dentry != path->mnt->mnt_root)
1906 err = security_sb_remount(sb, data);
1910 down_write(&sb->s_umount);
1911 if (flags & MS_BIND)
1912 err = change_mount_flags(path->mnt, flags);
1913 else if (!capable(CAP_SYS_ADMIN))
1916 err = do_remount_sb(sb, flags, data, 0);
1919 mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK;
1920 mnt->mnt.mnt_flags = mnt_flags;
1921 touch_mnt_namespace(mnt->mnt_ns);
1922 unlock_mount_hash();
1924 up_write(&sb->s_umount);
1928 static inline int tree_contains_unbindable(struct mount *mnt)
1931 for (p = mnt; p; p = next_mnt(p, mnt)) {
1932 if (IS_MNT_UNBINDABLE(p))
1938 static int do_move_mount(struct path *path, const char *old_name)
1940 struct path old_path, parent_path;
1943 struct mountpoint *mp;
1945 if (!old_name || !*old_name)
1947 err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
1951 mp = lock_mount(path);
1956 old = real_mount(old_path.mnt);
1957 p = real_mount(path->mnt);
1960 if (!check_mnt(p) || !check_mnt(old))
1963 if (old->mnt.mnt_flags & MNT_LOCKED)
1967 if (old_path.dentry != old_path.mnt->mnt_root)
1970 if (!mnt_has_parent(old))
1973 if (S_ISDIR(path->dentry->d_inode->i_mode) !=
1974 S_ISDIR(old_path.dentry->d_inode->i_mode))
1977 * Don't move a mount residing in a shared parent.
1979 if (IS_MNT_SHARED(old->mnt_parent))
1982 * Don't move a mount tree containing unbindable mounts to a destination
1983 * mount which is shared.
1985 if (IS_MNT_SHARED(p) && tree_contains_unbindable(old))
1988 for (; mnt_has_parent(p); p = p->mnt_parent)
1992 err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path);
1996 /* if the mount is moved, it should no longer be expire
1998 list_del_init(&old->mnt_expire);
2003 path_put(&parent_path);
2004 path_put(&old_path);
2008 static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
2011 const char *subtype = strchr(fstype, '.');
2020 mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
2022 if (!mnt->mnt_sb->s_subtype)
2028 return ERR_PTR(err);
2032 * add a mount into a namespace's mount tree
2034 static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags)
2036 struct mountpoint *mp;
2037 struct mount *parent;
2040 mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL | MNT_DOOMED | MNT_SYNC_UMOUNT);
2042 mp = lock_mount(path);
2046 parent = real_mount(path->mnt);
2048 if (unlikely(!check_mnt(parent))) {
2049 /* that's acceptable only for automounts done in private ns */
2050 if (!(mnt_flags & MNT_SHRINKABLE))
2052 /* ... and for those we'd better have mountpoint still alive */
2053 if (!parent->mnt_ns)
2057 /* Refuse the same filesystem on the same mount point */
2059 if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb &&
2060 path->mnt->mnt_root == path->dentry)
2064 if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode))
2067 newmnt->mnt.mnt_flags = mnt_flags;
2068 err = graft_tree(newmnt, parent, mp);
2076 * create a new mount for userspace and request it to be added into the
2079 static int do_new_mount(struct path *path, const char *fstype, int flags,
2080 int mnt_flags, const char *name, void *data)
2082 struct file_system_type *type;
2083 struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
2084 struct vfsmount *mnt;
2090 type = get_fs_type(fstype);
2094 if (user_ns != &init_user_ns) {
2095 if (!(type->fs_flags & FS_USERNS_MOUNT)) {
2096 put_filesystem(type);
2099 /* Only in special cases allow devices from mounts
2100 * created outside the initial user namespace.
2102 if (!(type->fs_flags & FS_USERNS_DEV_MOUNT)) {
2104 mnt_flags |= MNT_NODEV;
2108 mnt = vfs_kern_mount(type, flags, name, data);
2109 if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
2110 !mnt->mnt_sb->s_subtype)
2111 mnt = fs_set_subtype(mnt, fstype);
2113 put_filesystem(type);
2115 return PTR_ERR(mnt);
2117 err = do_add_mount(real_mount(mnt), path, mnt_flags);
2123 int finish_automount(struct vfsmount *m, struct path *path)
2125 struct mount *mnt = real_mount(m);
2127 /* The new mount record should have at least 2 refs to prevent it being
2128 * expired before we get a chance to add it
2130 BUG_ON(mnt_get_count(mnt) < 2);
2132 if (m->mnt_sb == path->mnt->mnt_sb &&
2133 m->mnt_root == path->dentry) {
2138 err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
2142 /* remove m from any expiration list it may be on */
2143 if (!list_empty(&mnt->mnt_expire)) {
2145 list_del_init(&mnt->mnt_expire);
2154 * mnt_set_expiry - Put a mount on an expiration list
2155 * @mnt: The mount to list.
2156 * @expiry_list: The list to add the mount to.
2158 void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
2162 list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list);
2166 EXPORT_SYMBOL(mnt_set_expiry);
2169 * process a list of expirable mountpoints with the intent of discarding any
2170 * mountpoints that aren't in use and haven't been touched since last we came
2173 void mark_mounts_for_expiry(struct list_head *mounts)
2175 struct mount *mnt, *next;
2176 LIST_HEAD(graveyard);
2178 if (list_empty(mounts))
2184 /* extract from the expiration list every vfsmount that matches the
2185 * following criteria:
2186 * - only referenced by its parent vfsmount
2187 * - still marked for expiry (marked on the last call here; marks are
2188 * cleared by mntput())
2190 list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
2191 if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2192 propagate_mount_busy(mnt, 1))
2194 list_move(&mnt->mnt_expire, &graveyard);
2196 while (!list_empty(&graveyard)) {
2197 mnt = list_first_entry(&graveyard, struct mount, mnt_expire);
2198 touch_mnt_namespace(mnt->mnt_ns);
2199 umount_tree(mnt, 1);
2201 unlock_mount_hash();
2205 EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);
2208 * Ripoff of 'select_parent()'
2210 * search the list of submounts for a given mountpoint, and move any
2211 * shrinkable submounts to the 'graveyard' list.
2213 static int select_submounts(struct mount *parent, struct list_head *graveyard)
2215 struct mount *this_parent = parent;
2216 struct list_head *next;
2220 next = this_parent->mnt_mounts.next;
2222 while (next != &this_parent->mnt_mounts) {
2223 struct list_head *tmp = next;
2224 struct mount *mnt = list_entry(tmp, struct mount, mnt_child);
2227 if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE))
2230 * Descend a level if the d_mounts list is non-empty.
2232 if (!list_empty(&mnt->mnt_mounts)) {
2237 if (!propagate_mount_busy(mnt, 1)) {
2238 list_move_tail(&mnt->mnt_expire, graveyard);
2243 * All done at this level ... ascend and resume the search
2245 if (this_parent != parent) {
2246 next = this_parent->mnt_child.next;
2247 this_parent = this_parent->mnt_parent;
2254 * process a list of expirable mountpoints with the intent of discarding any
2255 * submounts of a specific parent mountpoint
2257 * mount_lock must be held for write
2259 static void shrink_submounts(struct mount *mnt)
2261 LIST_HEAD(graveyard);
2264 /* extract submounts of 'mountpoint' from the expiration list */
2265 while (select_submounts(mnt, &graveyard)) {
2266 while (!list_empty(&graveyard)) {
2267 m = list_first_entry(&graveyard, struct mount,
2269 touch_mnt_namespace(m->mnt_ns);
2276 * Some copy_from_user() implementations do not return the exact number of
2277 * bytes remaining to copy on a fault. But copy_mount_options() requires that.
2278 * Note that this function differs from copy_from_user() in that it will oops
2279 * on bad values of `to', rather than returning a short copy.
2281 static long exact_copy_from_user(void *to, const void __user * from,
2285 const char __user *f = from;
2288 if (!access_ok(VERIFY_READ, from, n))
2292 if (__get_user(c, f)) {
2303 int copy_mount_options(const void __user * data, unsigned long *where)
2313 if (!(page = __get_free_page(GFP_KERNEL)))
2316 /* We only care that *some* data at the address the user
2317 * gave us is valid. Just in case, we'll zero
2318 * the remainder of the page.
2320 /* copy_from_user cannot cross TASK_SIZE ! */
2321 size = TASK_SIZE - (unsigned long)data;
2322 if (size > PAGE_SIZE)
2325 i = size - exact_copy_from_user((void *)page, data, size);
2331 memset((char *)page + i, 0, PAGE_SIZE - i);
2336 int copy_mount_string(const void __user *data, char **where)
2345 tmp = strndup_user(data, PAGE_SIZE);
2347 return PTR_ERR(tmp);
2354 * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to
2355 * be given to the mount() call (ie: read-only, no-dev, no-suid etc).
2357 * data is a (void *) that can point to any structure up to
2358 * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent
2359 * information (or be NULL).
2361 * Pre-0.97 versions of mount() didn't have a flags word.
2362 * When the flags word was introduced its top half was required
2363 * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9.
2364 * Therefore, if this magic number is present, it carries no information
2365 * and must be discarded.
2367 long do_mount(const char *dev_name, const char *dir_name,
2368 const char *type_page, unsigned long flags, void *data_page)
2375 if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
2376 flags &= ~MS_MGC_MSK;
2378 /* Basic sanity checks */
2380 if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
2384 ((char *)data_page)[PAGE_SIZE - 1] = 0;
2386 /* ... and get the mountpoint */
2387 retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
2391 retval = security_sb_mount(dev_name, &path,
2392 type_page, flags, data_page);
2393 if (!retval && !may_mount())
2398 /* Default to relatime unless overriden */
2399 if (!(flags & MS_NOATIME))
2400 mnt_flags |= MNT_RELATIME;
2402 /* Separate the per-mountpoint flags */
2403 if (flags & MS_NOSUID)
2404 mnt_flags |= MNT_NOSUID;
2405 if (flags & MS_NODEV)
2406 mnt_flags |= MNT_NODEV;
2407 if (flags & MS_NOEXEC)
2408 mnt_flags |= MNT_NOEXEC;
2409 if (flags & MS_NOATIME)
2410 mnt_flags |= MNT_NOATIME;
2411 if (flags & MS_NODIRATIME)
2412 mnt_flags |= MNT_NODIRATIME;
2413 if (flags & MS_STRICTATIME)
2414 mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2415 if (flags & MS_RDONLY)
2416 mnt_flags |= MNT_READONLY;
2418 flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
2419 MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
2422 if (flags & MS_REMOUNT)
2423 retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
2425 else if (flags & MS_BIND)
2426 retval = do_loopback(&path, dev_name, flags & MS_REC);
2427 else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2428 retval = do_change_type(&path, flags);
2429 else if (flags & MS_MOVE)
2430 retval = do_move_mount(&path, dev_name);
2432 retval = do_new_mount(&path, type_page, flags, mnt_flags,
2433 dev_name, data_page);
2439 static void free_mnt_ns(struct mnt_namespace *ns)
2441 proc_free_inum(ns->proc_inum);
2442 put_user_ns(ns->user_ns);
2447 * Assign a sequence number so we can detect when we attempt to bind
2448 * mount a reference to an older mount namespace into the current
2449 * mount namespace, preventing reference counting loops. A 64bit
2450 * number incrementing at 10Ghz will take 12,427 years to wrap which
2451 * is effectively never, so we can ignore the possibility.
2453 static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1);
2455 static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns)
2457 struct mnt_namespace *new_ns;
2460 new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
2462 return ERR_PTR(-ENOMEM);
2463 ret = proc_alloc_inum(&new_ns->proc_inum);
2466 return ERR_PTR(ret);
2468 new_ns->seq = atomic64_add_return(1, &mnt_ns_seq);
2469 atomic_set(&new_ns->count, 1);
2470 new_ns->root = NULL;
2471 INIT_LIST_HEAD(&new_ns->list);
2472 init_waitqueue_head(&new_ns->poll);
2474 new_ns->user_ns = get_user_ns(user_ns);
2478 struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2479 struct user_namespace *user_ns, struct fs_struct *new_fs)
2481 struct mnt_namespace *new_ns;
2482 struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
2483 struct mount *p, *q;
2490 if (likely(!(flags & CLONE_NEWNS))) {
2497 new_ns = alloc_mnt_ns(user_ns);
2502 /* First pass: copy the tree topology */
2503 copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE;
2504 if (user_ns != ns->user_ns)
2505 copy_flags |= CL_SHARED_TO_SLAVE | CL_UNPRIVILEGED;
2506 new = copy_tree(old, old->mnt.mnt_root, copy_flags);
2509 free_mnt_ns(new_ns);
2510 return ERR_CAST(new);
2513 list_add_tail(&new_ns->list, &new->mnt_list);
2516 * Second pass: switch the tsk->fs->* elements and mark new vfsmounts
2517 * as belonging to new namespace. We have already acquired a private
2518 * fs_struct, so tsk->fs->lock is not needed.
2525 if (&p->mnt == new_fs->root.mnt) {
2526 new_fs->root.mnt = mntget(&q->mnt);
2529 if (&p->mnt == new_fs->pwd.mnt) {
2530 new_fs->pwd.mnt = mntget(&q->mnt);
2534 p = next_mnt(p, old);
2535 q = next_mnt(q, new);
2538 while (p->mnt.mnt_root != q->mnt.mnt_root)
2539 p = next_mnt(p, old);
2552 * create_mnt_ns - creates a private namespace and adds a root filesystem
2553 * @mnt: pointer to the new root filesystem mountpoint
2555 static struct mnt_namespace *create_mnt_ns(struct vfsmount *m)
2557 struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns);
2558 if (!IS_ERR(new_ns)) {
2559 struct mount *mnt = real_mount(m);
2560 mnt->mnt_ns = new_ns;
2562 list_add(&mnt->mnt_list, &new_ns->list);
2569 struct dentry *mount_subtree(struct vfsmount *mnt, const char *name)
2571 struct mnt_namespace *ns;
2572 struct super_block *s;
2576 ns = create_mnt_ns(mnt);
2578 return ERR_CAST(ns);
2580 err = vfs_path_lookup(mnt->mnt_root, mnt,
2581 name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path);
2586 return ERR_PTR(err);
2588 /* trade a vfsmount reference for active sb one */
2589 s = path.mnt->mnt_sb;
2590 atomic_inc(&s->s_active);
2592 /* lock the sucker */
2593 down_write(&s->s_umount);
2594 /* ... and return the root of (sub)tree on it */
2597 EXPORT_SYMBOL(mount_subtree);
2599 SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
2600 char __user *, type, unsigned long, flags, void __user *, data)
2604 struct filename *kernel_dir;
2606 unsigned long data_page;
2608 ret = copy_mount_string(type, &kernel_type);
2612 kernel_dir = getname(dir_name);
2613 if (IS_ERR(kernel_dir)) {
2614 ret = PTR_ERR(kernel_dir);
2618 ret = copy_mount_string(dev_name, &kernel_dev);
2622 ret = copy_mount_options(data, &data_page);
2626 ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags,
2627 (void *) data_page);
2629 free_page(data_page);
2633 putname(kernel_dir);
2641 * Return true if path is reachable from root
2643 * namespace_sem or mount_lock is held
2645 bool is_path_reachable(struct mount *mnt, struct dentry *dentry,
2646 const struct path *root)
2648 while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) {
2649 dentry = mnt->mnt_mountpoint;
2650 mnt = mnt->mnt_parent;
2652 return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry);
2655 int path_is_under(struct path *path1, struct path *path2)
2658 read_seqlock_excl(&mount_lock);
2659 res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2);
2660 read_sequnlock_excl(&mount_lock);
2663 EXPORT_SYMBOL(path_is_under);
2666 * pivot_root Semantics:
2667 * Moves the root file system of the current process to the directory put_old,
2668 * makes new_root as the new root file system of the current process, and sets
2669 * root/cwd of all processes which had them on the current root to new_root.
2672 * The new_root and put_old must be directories, and must not be on the
2673 * same file system as the current process root. The put_old must be
2674 * underneath new_root, i.e. adding a non-zero number of /.. to the string
2675 * pointed to by put_old must yield the same directory as new_root. No other
2676 * file system may be mounted on put_old. After all, new_root is a mountpoint.
2678 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
2679 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
2680 * in this situation.
2683 * - we don't move root/cwd if they are not at the root (reason: if something
2684 * cared enough to change them, it's probably wrong to force them elsewhere)
2685 * - it's okay to pick a root that isn't the root of a file system, e.g.
2686 * /nfs/my_root where /nfs is the mount point. It must be a mountpoint,
2687 * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root
2690 SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
2691 const char __user *, put_old)
2693 struct path new, old, parent_path, root_parent, root;
2694 struct mount *new_mnt, *root_mnt, *old_mnt;
2695 struct mountpoint *old_mp, *root_mp;
2701 error = user_path_dir(new_root, &new);
2705 error = user_path_dir(put_old, &old);
2709 error = security_sb_pivotroot(&old, &new);
2713 get_fs_root(current->fs, &root);
2714 old_mp = lock_mount(&old);
2715 error = PTR_ERR(old_mp);
2720 new_mnt = real_mount(new.mnt);
2721 root_mnt = real_mount(root.mnt);
2722 old_mnt = real_mount(old.mnt);
2723 if (IS_MNT_SHARED(old_mnt) ||
2724 IS_MNT_SHARED(new_mnt->mnt_parent) ||
2725 IS_MNT_SHARED(root_mnt->mnt_parent))
2727 if (!check_mnt(root_mnt) || !check_mnt(new_mnt))
2729 if (new_mnt->mnt.mnt_flags & MNT_LOCKED)
2732 if (d_unlinked(new.dentry))
2735 if (new_mnt == root_mnt || old_mnt == root_mnt)
2736 goto out4; /* loop, on the same file system */
2738 if (root.mnt->mnt_root != root.dentry)
2739 goto out4; /* not a mountpoint */
2740 if (!mnt_has_parent(root_mnt))
2741 goto out4; /* not attached */
2742 root_mp = root_mnt->mnt_mp;
2743 if (new.mnt->mnt_root != new.dentry)
2744 goto out4; /* not a mountpoint */
2745 if (!mnt_has_parent(new_mnt))
2746 goto out4; /* not attached */
2747 /* make sure we can reach put_old from new_root */
2748 if (!is_path_reachable(old_mnt, old.dentry, &new))
2750 root_mp->m_count++; /* pin it so it won't go away */
2752 detach_mnt(new_mnt, &parent_path);
2753 detach_mnt(root_mnt, &root_parent);
2754 if (root_mnt->mnt.mnt_flags & MNT_LOCKED) {
2755 new_mnt->mnt.mnt_flags |= MNT_LOCKED;
2756 root_mnt->mnt.mnt_flags &= ~MNT_LOCKED;
2758 /* mount old root on put_old */
2759 attach_mnt(root_mnt, old_mnt, old_mp);
2760 /* mount new_root on / */
2761 attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp);
2762 touch_mnt_namespace(current->nsproxy->mnt_ns);
2763 unlock_mount_hash();
2764 chroot_fs_refs(&root, &new);
2765 put_mountpoint(root_mp);
2768 unlock_mount(old_mp);
2770 path_put(&root_parent);
2771 path_put(&parent_path);
2783 static void __init init_mount_tree(void)
2785 struct vfsmount *mnt;
2786 struct mnt_namespace *ns;
2788 struct file_system_type *type;
2790 type = get_fs_type("rootfs");
2792 panic("Can't find rootfs type");
2793 mnt = vfs_kern_mount(type, 0, "rootfs", NULL);
2794 put_filesystem(type);
2796 panic("Can't create rootfs");
2798 ns = create_mnt_ns(mnt);
2800 panic("Can't allocate initial namespace");
2802 init_task.nsproxy->mnt_ns = ns;
2806 root.dentry = mnt->mnt_root;
2808 set_fs_pwd(current->fs, &root);
2809 set_fs_root(current->fs, &root);
2812 void __init mnt_init(void)
2817 mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount),
2818 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2820 mount_hashtable = alloc_large_system_hash("Mount-cache",
2821 sizeof(struct list_head),
2824 &m_hash_shift, &m_hash_mask, 0, 0);
2825 mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache",
2826 sizeof(struct hlist_head),
2829 &mp_hash_shift, &mp_hash_mask, 0, 0);
2831 if (!mount_hashtable || !mountpoint_hashtable)
2832 panic("Failed to allocate mount hash table\n");
2834 for (u = 0; u <= m_hash_mask; u++)
2835 INIT_LIST_HEAD(&mount_hashtable[u]);
2836 for (u = 0; u <= mp_hash_mask; u++)
2837 INIT_HLIST_HEAD(&mountpoint_hashtable[u]);
2843 printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2845 fs_kobj = kobject_create_and_add("fs", NULL);
2847 printk(KERN_WARNING "%s: kobj create error\n", __func__);
2852 void put_mnt_ns(struct mnt_namespace *ns)
2854 if (!atomic_dec_and_test(&ns->count))
2856 drop_collected_mounts(&ns->root->mnt);
2860 struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
2862 struct vfsmount *mnt;
2863 mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
2866 * it is a longterm mount, don't release mnt until
2867 * we unmount before file sys is unregistered
2869 real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL;
2873 EXPORT_SYMBOL_GPL(kern_mount_data);
2875 void kern_unmount(struct vfsmount *mnt)
2877 /* release long term mount so mount point can be released */
2878 if (!IS_ERR_OR_NULL(mnt)) {
2879 real_mount(mnt)->mnt_ns = NULL;
2880 synchronize_rcu(); /* yecchhh... */
2884 EXPORT_SYMBOL(kern_unmount);
2886 bool our_mnt(struct vfsmount *mnt)
2888 return check_mnt(real_mount(mnt));
2891 bool current_chrooted(void)
2893 /* Does the current process have a non-standard root */
2894 struct path ns_root;
2895 struct path fs_root;
2898 /* Find the namespace root */
2899 ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt;
2900 ns_root.dentry = ns_root.mnt->mnt_root;
2902 while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root))
2905 get_fs_root(current->fs, &fs_root);
2907 chrooted = !path_equal(&fs_root, &ns_root);
2915 bool fs_fully_visible(struct file_system_type *type)
2917 struct mnt_namespace *ns = current->nsproxy->mnt_ns;
2919 bool visible = false;
2924 down_read(&namespace_sem);
2925 list_for_each_entry(mnt, &ns->list, mnt_list) {
2926 struct mount *child;
2927 if (mnt->mnt.mnt_sb->s_type != type)
2930 /* This mount is not fully visible if there are any child mounts
2931 * that cover anything except for empty directories.
2933 list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) {
2934 struct inode *inode = child->mnt_mountpoint->d_inode;
2935 if (!S_ISDIR(inode->i_mode))
2937 if (inode->i_nlink > 2)
2945 up_read(&namespace_sem);
2949 static void *mntns_get(struct task_struct *task)
2951 struct mnt_namespace *ns = NULL;
2952 struct nsproxy *nsproxy;
2955 nsproxy = task_nsproxy(task);
2957 ns = nsproxy->mnt_ns;
2965 static void mntns_put(void *ns)
2970 static int mntns_install(struct nsproxy *nsproxy, void *ns)
2972 struct fs_struct *fs = current->fs;
2973 struct mnt_namespace *mnt_ns = ns;
2976 if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
2977 !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
2978 !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
2985 put_mnt_ns(nsproxy->mnt_ns);
2986 nsproxy->mnt_ns = mnt_ns;
2989 root.mnt = &mnt_ns->root->mnt;
2990 root.dentry = mnt_ns->root->mnt.mnt_root;
2992 while(d_mountpoint(root.dentry) && follow_down_one(&root))
2995 /* Update the pwd and root */
2996 set_fs_pwd(fs, &root);
2997 set_fs_root(fs, &root);
3003 static unsigned int mntns_inum(void *ns)
3005 struct mnt_namespace *mnt_ns = ns;
3006 return mnt_ns->proc_inum;
3009 const struct proc_ns_operations mntns_operations = {
3011 .type = CLONE_NEWNS,
3014 .install = mntns_install,