/* * linux/fs/namespace.c * * (C) Copyright Al Viro 2000, 2001 * Released under GPL v2. * * Based on code from fs/super.c, copyright Linus Torvalds and others. * Heavily rewritten. */ #include #include #include #include #include #include #include #include /* acct_auto_close_mnt */ #include /* init_rootfs */ #include /* get_fs_root et.al. */ #include /* fsnotify_vfsmount_delete */ #include #include #include "pnode.h" #include "internal.h" #define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) #define HASH_SIZE (1UL << HASH_SHIFT) static int event; static DEFINE_IDA(mnt_id_ida); static DEFINE_IDA(mnt_group_ida); static DEFINE_SPINLOCK(mnt_id_lock); static int mnt_id_start = 0; static int mnt_group_start = 1; static struct list_head *mount_hashtable __read_mostly; static struct kmem_cache *mnt_cache __read_mostly; static struct rw_semaphore namespace_sem; /* /sys/fs */ struct kobject *fs_kobj; EXPORT_SYMBOL_GPL(fs_kobj); /* * vfsmount lock may be taken for read to prevent changes to the * vfsmount hash, ie. during mountpoint lookups or walking back * up the tree. * * It should be taken for write in all cases where the vfsmount * tree or hash is modified or when a vfsmount structure is modified. */ DEFINE_BRLOCK(vfsmount_lock); static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry) { unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); tmp += ((unsigned long)dentry / L1_CACHE_BYTES); tmp = tmp + (tmp >> HASH_SHIFT); return tmp & (HASH_SIZE - 1); } #define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16) /* * allocation is serialized by namespace_sem, but we need the spinlock to * serialize with freeing. */ static int mnt_alloc_id(struct mount *mnt) { int res; retry: ida_pre_get(&mnt_id_ida, GFP_KERNEL); spin_lock(&mnt_id_lock); res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id); if (!res) mnt_id_start = mnt->mnt_id + 1; spin_unlock(&mnt_id_lock); if (res == -EAGAIN) goto retry; return res; } static void mnt_free_id(struct mount *mnt) { int id = mnt->mnt_id; spin_lock(&mnt_id_lock); ida_remove(&mnt_id_ida, id); if (mnt_id_start > id) mnt_id_start = id; spin_unlock(&mnt_id_lock); } /* * Allocate a new peer group ID * * mnt_group_ida is protected by namespace_sem */ static int mnt_alloc_group_id(struct mount *mnt) { int res; if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL)) return -ENOMEM; res = ida_get_new_above(&mnt_group_ida, mnt_group_start, &mnt->mnt_group_id); if (!res) mnt_group_start = mnt->mnt_group_id + 1; return res; } /* * Release a peer group ID */ void mnt_release_group_id(struct mount *mnt) { int id = mnt->mnt_group_id; ida_remove(&mnt_group_ida, id); if (mnt_group_start > id) mnt_group_start = id; mnt->mnt_group_id = 0; } /* * vfsmount lock must be held for read */ static inline void mnt_add_count(struct mount *mnt, int n) { #ifdef CONFIG_SMP this_cpu_add(mnt->mnt_pcp->mnt_count, n); #else preempt_disable(); mnt->mnt_count += n; preempt_enable(); #endif } /* * vfsmount lock must be held for write */ unsigned int mnt_get_count(struct mount *mnt) { #ifdef CONFIG_SMP unsigned int count = 0; int cpu; for_each_possible_cpu(cpu) { count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; } return count; #else return mnt->mnt_count; #endif } static struct mount *alloc_vfsmnt(const char *name) { struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); if (mnt) { int err; err = mnt_alloc_id(mnt); if (err) goto out_free_cache; if (name) { mnt->mnt_devname = kstrdup(name, GFP_KERNEL); if (!mnt->mnt_devname) goto out_free_id; } #ifdef CONFIG_SMP mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); if (!mnt->mnt_pcp) goto out_free_devname; this_cpu_add(mnt->mnt_pcp->mnt_count, 1); #else mnt->mnt_count = 1; mnt->mnt_writers = 0; #endif INIT_LIST_HEAD(&mnt->mnt_hash); INIT_LIST_HEAD(&mnt->mnt_child); INIT_LIST_HEAD(&mnt->mnt_mounts); INIT_LIST_HEAD(&mnt->mnt_list); INIT_LIST_HEAD(&mnt->mnt_expire); INIT_LIST_HEAD(&mnt->mnt_share); INIT_LIST_HEAD(&mnt->mnt_slave_list); INIT_LIST_HEAD(&mnt->mnt_slave); #ifdef CONFIG_FSNOTIFY INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks); #endif } return mnt; #ifdef CONFIG_SMP out_free_devname: kfree(mnt->mnt_devname); #endif out_free_id: mnt_free_id(mnt); out_free_cache: kmem_cache_free(mnt_cache, mnt); return NULL; } /* * Most r/o checks on a fs are for operations that take * discrete amounts of time, like a write() or unlink(). * We must keep track of when those operations start * (for permission checks) and when they end, so that * we can determine when writes are able to occur to * a filesystem. */ /* * __mnt_is_readonly: check whether a mount is read-only * @mnt: the mount to check for its write status * * This shouldn't be used directly ouside of the VFS. * It does not guarantee that the filesystem will stay * r/w, just that it is right *now*. This can not and * should not be used in place of IS_RDONLY(inode). * mnt_want/drop_write() will _keep_ the filesystem * r/w. */ int __mnt_is_readonly(struct vfsmount *mnt) { if (mnt->mnt_flags & MNT_READONLY) return 1; if (mnt->mnt_sb->s_flags & MS_RDONLY) return 1; return 0; } EXPORT_SYMBOL_GPL(__mnt_is_readonly); static inline void mnt_inc_writers(struct mount *mnt) { #ifdef CONFIG_SMP this_cpu_inc(mnt->mnt_pcp->mnt_writers); #else mnt->mnt_writers++; #endif } static inline void mnt_dec_writers(struct mount *mnt) { #ifdef CONFIG_SMP this_cpu_dec(mnt->mnt_pcp->mnt_writers); #else mnt->mnt_writers--; #endif } static unsigned int mnt_get_writers(struct mount *mnt) { #ifdef CONFIG_SMP unsigned int count = 0; int cpu; for_each_possible_cpu(cpu) { count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; } return count; #else return mnt->mnt_writers; #endif } static int mnt_is_readonly(struct vfsmount *mnt) { if (mnt->mnt_sb->s_readonly_remount) return 1; /* Order wrt setting s_flags/s_readonly_remount in do_remount() */ smp_rmb(); return __mnt_is_readonly(mnt); } /* * Most r/o & frozen checks on a fs are for operations that take discrete * amounts of time, like a write() or unlink(). We must keep track of when * those operations start (for permission checks) and when they end, so that we * can determine when writes are able to occur to a filesystem. */ /** * __mnt_want_write - get write access to a mount without freeze protection * @m: the mount on which to take a write * * This tells the low-level filesystem that a write is about to be performed to * it, and makes sure that writes are allowed (mnt it read-write) before * returning success. This operation does not protect against filesystem being * frozen. When the write operation is finished, __mnt_drop_write() must be * called. This is effectively a refcount. */ int __mnt_want_write(struct vfsmount *m) { struct mount *mnt = real_mount(m); int ret = 0; preempt_disable(); mnt_inc_writers(mnt); /* * The store to mnt_inc_writers must be visible before we pass * MNT_WRITE_HOLD loop below, so that the slowpath can see our * incremented count after it has set MNT_WRITE_HOLD. */ smp_mb(); while (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) cpu_relax(); /* * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will * be set to match its requirements. So we must not load that until * MNT_WRITE_HOLD is cleared. */ smp_rmb(); if (mnt_is_readonly(m)) { mnt_dec_writers(mnt); ret = -EROFS; } preempt_enable(); return ret; } /** * mnt_want_write - get write access to a mount * @m: the mount on which to take a write * * This tells the low-level filesystem that a write is about to be performed to * it, and makes sure that writes are allowed (mount is read-write, filesystem * is not frozen) before returning success. When the write operation is * finished, mnt_drop_write() must be called. This is effectively a refcount. */ int mnt_want_write(struct vfsmount *m) { int ret; sb_start_write(m->mnt_sb); ret = __mnt_want_write(m); if (ret) sb_end_write(m->mnt_sb); return ret; } EXPORT_SYMBOL_GPL(mnt_want_write); /** * mnt_clone_write - get write access to a mount * @mnt: the mount on which to take a write * * This is effectively like mnt_want_write, except * it must only be used to take an extra write reference * on a mountpoint that we already know has a write reference * on it. This allows some optimisation. * * After finished, mnt_drop_write must be called as usual to * drop the reference. */ int mnt_clone_write(struct vfsmount *mnt) { /* superblock may be r/o */ if (__mnt_is_readonly(mnt)) return -EROFS; preempt_disable(); mnt_inc_writers(real_mount(mnt)); preempt_enable(); return 0; } EXPORT_SYMBOL_GPL(mnt_clone_write); /** * __mnt_want_write_file - get write access to a file's mount * @file: the file who's mount on which to take a write * * This is like __mnt_want_write, but it takes a file and can * do some optimisations if the file is open for write already */ int __mnt_want_write_file(struct file *file) { struct inode *inode = file->f_dentry->d_inode; if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode)) return __mnt_want_write(file->f_path.mnt); else return mnt_clone_write(file->f_path.mnt); } /** * mnt_want_write_file - get write access to a file's mount * @file: the file who's mount on which to take a write * * This is like mnt_want_write, but it takes a file and can * do some optimisations if the file is open for write already */ int mnt_want_write_file(struct file *file) { int ret; sb_start_write(file->f_path.mnt->mnt_sb); ret = __mnt_want_write_file(file); if (ret) sb_end_write(file->f_path.mnt->mnt_sb); return ret; } EXPORT_SYMBOL_GPL(mnt_want_write_file); /** * __mnt_drop_write - give up write access to a mount * @mnt: the mount on which to give up write access * * Tells the low-level filesystem that we are done * performing writes to it. Must be matched with * __mnt_want_write() call above. */ void __mnt_drop_write(struct vfsmount *mnt) { preempt_disable(); mnt_dec_writers(real_mount(mnt)); preempt_enable(); } /** * mnt_drop_write - give up write access to a mount * @mnt: the mount on which to give up write access * * Tells the low-level filesystem that we are done performing writes to it and * also allows filesystem to be frozen again. Must be matched with * mnt_want_write() call above. */ void mnt_drop_write(struct vfsmount *mnt) { __mnt_drop_write(mnt); sb_end_write(mnt->mnt_sb); } EXPORT_SYMBOL_GPL(mnt_drop_write); void __mnt_drop_write_file(struct file *file) { __mnt_drop_write(file->f_path.mnt); } void mnt_drop_write_file(struct file *file) { mnt_drop_write(file->f_path.mnt); } EXPORT_SYMBOL(mnt_drop_write_file); static int mnt_make_readonly(struct mount *mnt) { int ret = 0; br_write_lock(&vfsmount_lock); mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; /* * After storing MNT_WRITE_HOLD, we'll read the counters. This store * should be visible before we do. */ smp_mb(); /* * With writers on hold, if this value is zero, then there are * definitely no active writers (although held writers may subsequently * increment the count, they'll have to wait, and decrement it after * seeing MNT_READONLY). * * It is OK to have counter incremented on one CPU and decremented on * another: the sum will add up correctly. The danger would be when we * sum up each counter, if we read a counter before it is incremented, * but then read another CPU's count which it has been subsequently * decremented from -- we would see more decrements than we should. * MNT_WRITE_HOLD protects against this scenario, because * mnt_want_write first increments count, then smp_mb, then spins on * MNT_WRITE_HOLD, so it can't be decremented by another CPU while * we're counting up here. */ if (mnt_get_writers(mnt) > 0) ret = -EBUSY; else mnt->mnt.mnt_flags |= MNT_READONLY; /* * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers * that become unheld will see MNT_READONLY. */ smp_wmb(); mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; br_write_unlock(&vfsmount_lock); return ret; } static void __mnt_unmake_readonly(struct mount *mnt) { br_write_lock(&vfsmount_lock); mnt->mnt.mnt_flags &= ~MNT_READONLY; br_write_unlock(&vfsmount_lock); } int sb_prepare_remount_readonly(struct super_block *sb) { struct mount *mnt; int err = 0; /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ if (atomic_long_read(&sb->s_remove_count)) return -EBUSY; br_write_lock(&vfsmount_lock); list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; smp_mb(); if (mnt_get_writers(mnt) > 0) { err = -EBUSY; break; } } } if (!err && atomic_long_read(&sb->s_remove_count)) err = -EBUSY; if (!err) { sb->s_readonly_remount = 1; smp_wmb(); } list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; } br_write_unlock(&vfsmount_lock); return err; } static void free_vfsmnt(struct mount *mnt) { kfree(mnt->mnt_devname); mnt_free_id(mnt); #ifdef CONFIG_SMP free_percpu(mnt->mnt_pcp); #endif kmem_cache_free(mnt_cache, mnt); } /* * find the first or last mount at @dentry on vfsmount @mnt depending on * @dir. If @dir is set return the first mount else return the last mount. * vfsmount_lock must be held for read or write. */ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry, int dir) { struct list_head *head = mount_hashtable + hash(mnt, dentry); struct list_head *tmp = head; struct mount *p, *found = NULL; for (;;) { tmp = dir ? tmp->next : tmp->prev; p = NULL; if (tmp == head) break; p = list_entry(tmp, struct mount, mnt_hash); if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) { found = p; break; } } return found; } /* * lookup_mnt - Return the first child mount mounted at path * * "First" means first mounted chronologically. If you create the * following mounts: * * mount /dev/sda1 /mnt * mount /dev/sda2 /mnt * mount /dev/sda3 /mnt * * Then lookup_mnt() on the base /mnt dentry in the root mount will * return successively the root dentry and vfsmount of /dev/sda1, then * /dev/sda2, then /dev/sda3, then NULL. * * lookup_mnt takes a reference to the found vfsmount. */ struct vfsmount *lookup_mnt(struct path *path) { struct mount *child_mnt; br_read_lock(&vfsmount_lock); child_mnt = __lookup_mnt(path->mnt, path->dentry, 1); if (child_mnt) { mnt_add_count(child_mnt, 1); br_read_unlock(&vfsmount_lock); return &child_mnt->mnt; } else { br_read_unlock(&vfsmount_lock); return NULL; } } static inline int check_mnt(struct mount *mnt) { return mnt->mnt_ns == current->nsproxy->mnt_ns; } /* * vfsmount lock must be held for write */ static void touch_mnt_namespace(struct mnt_namespace *ns) { if (ns) { ns->event = ++event; wake_up_interruptible(&ns->poll); } } /* * vfsmount lock must be held for write */ static void __touch_mnt_namespace(struct mnt_namespace *ns) { if (ns && ns->event != event) { ns->event = event; wake_up_interruptible(&ns->poll); } } /* * Clear dentry's mounted state if it has no remaining mounts. * vfsmount_lock must be held for write. */ static void dentry_reset_mounted(struct dentry *dentry) { unsigned u; for (u = 0; u < HASH_SIZE; u++) { struct mount *p; list_for_each_entry(p, &mount_hashtable[u], mnt_hash) { if (p->mnt_mountpoint == dentry) return; } } spin_lock(&dentry->d_lock); dentry->d_flags &= ~DCACHE_MOUNTED; spin_unlock(&dentry->d_lock); } /* * vfsmount lock must be held for write */ static void detach_mnt(struct mount *mnt, struct path *old_path) { old_path->dentry = mnt->mnt_mountpoint; old_path->mnt = &mnt->mnt_parent->mnt; mnt->mnt_parent = mnt; mnt->mnt_mountpoint = mnt->mnt.mnt_root; list_del_init(&mnt->mnt_child); list_del_init(&mnt->mnt_hash); dentry_reset_mounted(old_path->dentry); } /* * vfsmount lock must be held for write */ void mnt_set_mountpoint(struct mount *mnt, struct dentry *dentry, struct mount *child_mnt) { mnt_add_count(mnt, 1); /* essentially, that's mntget */ child_mnt->mnt_mountpoint = dget(dentry); child_mnt->mnt_parent = mnt; spin_lock(&dentry->d_lock); dentry->d_flags |= DCACHE_MOUNTED; spin_unlock(&dentry->d_lock); } /* * vfsmount lock must be held for write */ static void attach_mnt(struct mount *mnt, struct path *path) { mnt_set_mountpoint(real_mount(path->mnt), path->dentry, mnt); list_add_tail(&mnt->mnt_hash, mount_hashtable + hash(path->mnt, path->dentry)); list_add_tail(&mnt->mnt_child, &real_mount(path->mnt)->mnt_mounts); } /* * vfsmount lock must be held for write */ static void commit_tree(struct mount *mnt) { struct mount *parent = mnt->mnt_parent; struct mount *m; LIST_HEAD(head); struct mnt_namespace *n = parent->mnt_ns; BUG_ON(parent == mnt); list_add_tail(&head, &mnt->mnt_list); list_for_each_entry(m, &head, mnt_list) m->mnt_ns = n; list_splice(&head, n->list.prev); list_add_tail(&mnt->mnt_hash, mount_hashtable + hash(&parent->mnt, mnt->mnt_mountpoint)); list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); touch_mnt_namespace(n); } static struct mount *next_mnt(struct mount *p, struct mount *root) { struct list_head *next = p->mnt_mounts.next; if (next == &p->mnt_mounts) { while (1) { if (p == root) return NULL; next = p->mnt_child.next; if (next != &p->mnt_parent->mnt_mounts) break; p = p->mnt_parent; } } return list_entry(next, struct mount, mnt_child); } static struct mount *skip_mnt_tree(struct mount *p) { struct list_head *prev = p->mnt_mounts.prev; while (prev != &p->mnt_mounts) { p = list_entry(prev, struct mount, mnt_child); prev = p->mnt_mounts.prev; } return p; } struct vfsmount * vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) { struct mount *mnt; struct dentry *root; if (!type) return ERR_PTR(-ENODEV); mnt = alloc_vfsmnt(name); if (!mnt) return ERR_PTR(-ENOMEM); if (flags & MS_KERNMOUNT) mnt->mnt.mnt_flags = MNT_INTERNAL; root = mount_fs(type, flags, name, data); if (IS_ERR(root)) { free_vfsmnt(mnt); return ERR_CAST(root); } mnt->mnt.mnt_root = root; mnt->mnt.mnt_sb = root->d_sb; mnt->mnt_mountpoint = mnt->mnt.mnt_root; mnt->mnt_parent = mnt; br_write_lock(&vfsmount_lock); list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); br_write_unlock(&vfsmount_lock); return &mnt->mnt; } EXPORT_SYMBOL_GPL(vfs_kern_mount); static struct mount *clone_mnt(struct mount *old, struct dentry *root, int flag) { struct super_block *sb = old->mnt.mnt_sb; struct mount *mnt; int err; mnt = alloc_vfsmnt(old->mnt_devname); if (!mnt) return ERR_PTR(-ENOMEM); if (flag & (CL_SLAVE | CL_PRIVATE)) mnt->mnt_group_id = 0; /* not a peer of original */ else mnt->mnt_group_id = old->mnt_group_id; if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { err = mnt_alloc_group_id(mnt); if (err) goto out_free; } mnt->mnt.mnt_flags = old->mnt.mnt_flags & ~MNT_WRITE_HOLD; atomic_inc(&sb->s_active); mnt->mnt.mnt_sb = sb; mnt->mnt.mnt_root = dget(root); mnt->mnt_mountpoint = mnt->mnt.mnt_root; mnt->mnt_parent = mnt; br_write_lock(&vfsmount_lock); list_add_tail(&mnt->mnt_instance, &sb->s_mounts); br_write_unlock(&vfsmount_lock); if (flag & CL_SLAVE) { list_add(&mnt->mnt_slave, &old->mnt_slave_list); mnt->mnt_master = old; CLEAR_MNT_SHARED(mnt); } else if (!(flag & CL_PRIVATE)) { if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) list_add(&mnt->mnt_share, &old->mnt_share); if (IS_MNT_SLAVE(old)) list_add(&mnt->mnt_slave, &old->mnt_slave); mnt->mnt_master = old->mnt_master; } if (flag & CL_MAKE_SHARED) set_mnt_shared(mnt); /* stick the duplicate mount on the same expiry list * as the original if that was on one */ if (flag & CL_EXPIRE) { if (!list_empty(&old->mnt_expire)) list_add(&mnt->mnt_expire, &old->mnt_expire); } return mnt; out_free: free_vfsmnt(mnt); return ERR_PTR(err); } static inline void mntfree(struct mount *mnt) { struct vfsmount *m = &mnt->mnt; struct super_block *sb = m->mnt_sb; /* * This probably indicates that somebody messed * up a mnt_want/drop_write() pair. If this * happens, the filesystem was probably unable * to make r/w->r/o transitions. */ /* * The locking used to deal with mnt_count decrement provides barriers, * so mnt_get_writers() below is safe. */ WARN_ON(mnt_get_writers(mnt)); fsnotify_vfsmount_delete(m); dput(m->mnt_root); free_vfsmnt(mnt); deactivate_super(sb); } static void mntput_no_expire(struct mount *mnt) { put_again: #ifdef CONFIG_SMP br_read_lock(&vfsmount_lock); if (likely(mnt->mnt_ns)) { /* shouldn't be the last one */ mnt_add_count(mnt, -1); br_read_unlock(&vfsmount_lock); return; } br_read_unlock(&vfsmount_lock); br_write_lock(&vfsmount_lock); mnt_add_count(mnt, -1); if (mnt_get_count(mnt)) { br_write_unlock(&vfsmount_lock); return; } #else mnt_add_count(mnt, -1); if (likely(mnt_get_count(mnt))) return; br_write_lock(&vfsmount_lock); #endif if (unlikely(mnt->mnt_pinned)) { mnt_add_count(mnt, mnt->mnt_pinned + 1); mnt->mnt_pinned = 0; br_write_unlock(&vfsmount_lock); acct_auto_close_mnt(&mnt->mnt); goto put_again; } list_del(&mnt->mnt_instance); br_write_unlock(&vfsmount_lock); mntfree(mnt); } void mntput(struct vfsmount *mnt) { if (mnt) { struct mount *m = real_mount(mnt); /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ if (unlikely(m->mnt_expiry_mark)) m->mnt_expiry_mark = 0; mntput_no_expire(m); } } EXPORT_SYMBOL(mntput); struct vfsmount *mntget(struct vfsmount *mnt) { if (mnt) mnt_add_count(real_mount(mnt), 1); return mnt; } EXPORT_SYMBOL(mntget); void mnt_pin(struct vfsmount *mnt) { br_write_lock(&vfsmount_lock); real_mount(mnt)->mnt_pinned++; br_write_unlock(&vfsmount_lock); } EXPORT_SYMBOL(mnt_pin); void mnt_unpin(struct vfsmount *m) { struct mount *mnt = real_mount(m); br_write_lock(&vfsmount_lock); if (mnt->mnt_pinned) { mnt_add_count(mnt, 1); mnt->mnt_pinned--; } br_write_unlock(&vfsmount_lock); } EXPORT_SYMBOL(mnt_unpin); static inline void mangle(struct seq_file *m, const char *s) { seq_escape(m, s, " \t\n\\"); } /* * Simple .show_options callback for filesystems which don't want to * implement more complex mount option showing. * * See also save_mount_options(). */ int generic_show_options(struct seq_file *m, struct dentry *root) { const char *options; rcu_read_lock(); options = rcu_dereference(root->d_sb->s_options); if (options != NULL && options[0]) { seq_putc(m, ','); mangle(m, options); } rcu_read_unlock(); return 0; } EXPORT_SYMBOL(generic_show_options); /* * If filesystem uses generic_show_options(), this function should be * called from the fill_super() callback. * * The .remount_fs callback usually needs to be handled in a special * way, to make sure, that previous options are not overwritten if the * remount fails. * * Also note, that if the filesystem's .remount_fs function doesn't * reset all options to their default value, but changes only newly * given options, then the displayed options will not reflect reality * any more. */ void save_mount_options(struct super_block *sb, char *options) { BUG_ON(sb->s_options); rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL)); } EXPORT_SYMBOL(save_mount_options); void replace_mount_options(struct super_block *sb, char *options) { char *old = sb->s_options; rcu_assign_pointer(sb->s_options, options); if (old) { synchronize_rcu(); kfree(old); } } EXPORT_SYMBOL(replace_mount_options); #ifdef CONFIG_PROC_FS /* iterator; we want it to have access to namespace_sem, thus here... */ static void *m_start(struct seq_file *m, loff_t *pos) { struct proc_mounts *p = proc_mounts(m); down_read(&namespace_sem); return seq_list_start(&p->ns->list, *pos); } static void *m_next(struct seq_file *m, void *v, loff_t *pos) { struct proc_mounts *p = proc_mounts(m); return seq_list_next(v, &p->ns->list, pos); } static void m_stop(struct seq_file *m, void *v) { up_read(&namespace_sem); } static int m_show(struct seq_file *m, void *v) { struct proc_mounts *p = proc_mounts(m); struct mount *r = list_entry(v, struct mount, mnt_list); return p->show(m, &r->mnt); } const struct seq_operations mounts_op = { .start = m_start, .next = m_next, .stop = m_stop, .show = m_show, }; #endif /* CONFIG_PROC_FS */ /** * may_umount_tree - check if a mount tree is busy * @mnt: root of mount tree * * This is called to check if a tree of mounts has any * open files, pwds, chroots or sub mounts that are * busy. */ int may_umount_tree(struct vfsmount *m) { struct mount *mnt = real_mount(m); int actual_refs = 0; int minimum_refs = 0; struct mount *p; BUG_ON(!m); /* write lock needed for mnt_get_count */ br_write_lock(&vfsmount_lock); for (p = mnt; p; p = next_mnt(p, mnt)) { actual_refs += mnt_get_count(p); minimum_refs += 2; } br_write_unlock(&vfsmount_lock); if (actual_refs > minimum_refs) return 0; return 1; } EXPORT_SYMBOL(may_umount_tree); /** * may_umount - check if a mount point is busy * @mnt: root of mount * * This is called to check if a mount point has any * open files, pwds, chroots or sub mounts. If the * mount has sub mounts this will return busy * regardless of whether the sub mounts are busy. * * Doesn't take quota and stuff into account. IOW, in some cases it will * give false negatives. The main reason why it's here is that we need * a non-destructive way to look for easily umountable filesystems. */ int may_umount(struct vfsmount *mnt) { int ret = 1; down_read(&namespace_sem); br_write_lock(&vfsmount_lock); if (propagate_mount_busy(real_mount(mnt), 2)) ret = 0; br_write_unlock(&vfsmount_lock); up_read(&namespace_sem); return ret; } EXPORT_SYMBOL(may_umount); void release_mounts(struct list_head *head) { struct mount *mnt; while (!list_empty(head)) { mnt = list_first_entry(head, struct mount, mnt_hash); list_del_init(&mnt->mnt_hash); if (mnt_has_parent(mnt)) { struct dentry *dentry; struct mount *m; br_write_lock(&vfsmount_lock); dentry = mnt->mnt_mountpoint; m = mnt->mnt_parent; mnt->mnt_mountpoint = mnt->mnt.mnt_root; mnt->mnt_parent = mnt; m->mnt_ghosts--; br_write_unlock(&vfsmount_lock); dput(dentry); mntput(&m->mnt); } mntput(&mnt->mnt); } } /* * vfsmount lock must be held for write * namespace_sem must be held for write */ void umount_tree(struct mount *mnt, int propagate, struct list_head *kill) { LIST_HEAD(tmp_list); struct mount *p; for (p = mnt; p; p = next_mnt(p, mnt)) list_move(&p->mnt_hash, &tmp_list); if (propagate) propagate_umount(&tmp_list); list_for_each_entry(p, &tmp_list, mnt_hash) { list_del_init(&p->mnt_expire); list_del_init(&p->mnt_list); __touch_mnt_namespace(p->mnt_ns); p->mnt_ns = NULL; list_del_init(&p->mnt_child); if (mnt_has_parent(p)) { p->mnt_parent->mnt_ghosts++; dentry_reset_mounted(p->mnt_mountpoint); } change_mnt_propagation(p, MS_PRIVATE); } list_splice(&tmp_list, kill); } static void shrink_submounts(struct mount *mnt, struct list_head *umounts); static int do_umount(struct mount *mnt, int flags) { struct super_block *sb = mnt->mnt.mnt_sb; int retval; LIST_HEAD(umount_list); retval = security_sb_umount(&mnt->mnt, flags); if (retval) return retval; /* * Allow userspace to request a mountpoint be expired rather than * unmounting unconditionally. Unmount only happens if: * (1) the mark is already set (the mark is cleared by mntput()) * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] */ if (flags & MNT_EXPIRE) { if (&mnt->mnt == current->fs->root.mnt || flags & (MNT_FORCE | MNT_DETACH)) return -EINVAL; /* * probably don't strictly need the lock here if we examined * all race cases, but it's a slowpath. */ br_write_lock(&vfsmount_lock); if (mnt_get_count(mnt) != 2) { br_write_unlock(&vfsmount_lock); return -EBUSY; } br_write_unlock(&vfsmount_lock); if (!xchg(&mnt->mnt_expiry_mark, 1)) return -EAGAIN; } /* * If we may have to abort operations to get out of this * mount, and they will themselves hold resources we must * allow the fs to do things. In the Unix tradition of * 'Gee thats tricky lets do it in userspace' the umount_begin * might fail to complete on the first run through as other tasks * must return, and the like. Thats for the mount program to worry * about for the moment. */ if (flags & MNT_FORCE && sb->s_op->umount_begin) { sb->s_op->umount_begin(sb); } /* * No sense to grab the lock for this test, but test itself looks * somewhat bogus. Suggestions for better replacement? * Ho-hum... In principle, we might treat that as umount + switch * to rootfs. GC would eventually take care of the old vfsmount. * Actually it makes sense, especially if rootfs would contain a * /reboot - static binary that would close all descriptors and * call reboot(9). Then init(8) could umount root and exec /reboot. */ if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { /* * Special case for "unmounting" root ... * we just try to remount it readonly. */ down_write(&sb->s_umount); if (!(sb->s_flags & MS_RDONLY)) retval = do_remount_sb(sb, MS_RDONLY, NULL, 0); up_write(&sb->s_umount); return retval; } down_write(&namespace_sem); br_write_lock(&vfsmount_lock); event++; if (!(flags & MNT_DETACH)) shrink_submounts(mnt, &umount_list); retval = -EBUSY; if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) { if (!list_empty(&mnt->mnt_list)) umount_tree(mnt, 1, &umount_list); retval = 0; } br_write_unlock(&vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); return retval; } /* * Now umount can handle mount points as well as block devices. * This is important for filesystems which use unnamed block devices. * * We now support a flag for forced unmount like the other 'big iron' * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD */ SYSCALL_DEFINE2(umount, char __user *, name, int, flags) { struct path path; struct mount *mnt; int retval; int lookup_flags = 0; if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) return -EINVAL; if (!(flags & UMOUNT_NOFOLLOW)) lookup_flags |= LOOKUP_FOLLOW; retval = user_path_at(AT_FDCWD, name, lookup_flags, &path); if (retval) goto out; mnt = real_mount(path.mnt); retval = -EINVAL; if (path.dentry != path.mnt->mnt_root) goto dput_and_out; if (!check_mnt(mnt)) goto dput_and_out; retval = -EPERM; if (!capable(CAP_SYS_ADMIN)) goto dput_and_out; retval = do_umount(mnt, flags); dput_and_out: /* we mustn't call path_put() as that would clear mnt_expiry_mark */ dput(path.dentry); mntput_no_expire(mnt); out: return retval; } #ifdef __ARCH_WANT_SYS_OLDUMOUNT /* * The 2.0 compatible umount. No flags. */ SYSCALL_DEFINE1(oldumount, char __user *, name) { return sys_umount(name, 0); } #endif static int mount_is_safe(struct path *path) { if (capable(CAP_SYS_ADMIN)) return 0; return -EPERM; #ifdef notyet if (S_ISLNK(path->dentry->d_inode->i_mode)) return -EPERM; if (path->dentry->d_inode->i_mode & S_ISVTX) { if (current_uid() != path->dentry->d_inode->i_uid) return -EPERM; } if (inode_permission(path->dentry->d_inode, MAY_WRITE)) return -EPERM; return 0; #endif } static bool mnt_ns_loop(struct path *path) { /* Could bind mounting the mount namespace inode cause a * mount namespace loop? */ struct inode *inode = path->dentry->d_inode; struct proc_inode *ei; struct mnt_namespace *mnt_ns; if (!proc_ns_inode(inode)) return false; ei = PROC_I(inode); if (ei->ns_ops != &mntns_operations) return false; mnt_ns = ei->ns; return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; } struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, int flag) { struct mount *res, *p, *q, *r; struct path path; if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) return ERR_PTR(-EINVAL); res = q = clone_mnt(mnt, dentry, flag); if (IS_ERR(q)) return q; q->mnt_mountpoint = mnt->mnt_mountpoint; p = mnt; list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { struct mount *s; if (!is_subdir(r->mnt_mountpoint, dentry)) continue; for (s = r; s; s = next_mnt(s, r)) { if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) { s = skip_mnt_tree(s); continue; } while (p != s->mnt_parent) { p = p->mnt_parent; q = q->mnt_parent; } p = s; path.mnt = &q->mnt; path.dentry = p->mnt_mountpoint; q = clone_mnt(p, p->mnt.mnt_root, flag); if (IS_ERR(q)) goto out; br_write_lock(&vfsmount_lock); list_add_tail(&q->mnt_list, &res->mnt_list); attach_mnt(q, &path); br_write_unlock(&vfsmount_lock); } } return res; out: if (res) { LIST_HEAD(umount_list); br_write_lock(&vfsmount_lock); umount_tree(res, 0, &umount_list); br_write_unlock(&vfsmount_lock); release_mounts(&umount_list); } return q; } /* Caller should check returned pointer for errors */ struct vfsmount *collect_mounts(struct path *path) { struct mount *tree; down_write(&namespace_sem); tree = copy_tree(real_mount(path->mnt), path->dentry, CL_COPY_ALL | CL_PRIVATE); up_write(&namespace_sem); if (IS_ERR(tree)) return NULL; return &tree->mnt; } void drop_collected_mounts(struct vfsmount *mnt) { LIST_HEAD(umount_list); down_write(&namespace_sem); br_write_lock(&vfsmount_lock); umount_tree(real_mount(mnt), 0, &umount_list); br_write_unlock(&vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); } int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, struct vfsmount *root) { struct mount *mnt; int res = f(root, arg); if (res) return res; list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { res = f(&mnt->mnt, arg); if (res) return res; } return 0; } static void cleanup_group_ids(struct mount *mnt, struct mount *end) { struct mount *p; for (p = mnt; p != end; p = next_mnt(p, mnt)) { if (p->mnt_group_id && !IS_MNT_SHARED(p)) mnt_release_group_id(p); } } static int invent_group_ids(struct mount *mnt, bool recurse) { struct mount *p; for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { int err = mnt_alloc_group_id(p); if (err) { cleanup_group_ids(mnt, p); return err; } } } return 0; } /* * @source_mnt : mount tree to be attached * @nd : place the mount tree @source_mnt is attached * @parent_nd : if non-null, detach the source_mnt from its parent and * store the parent mount and mountpoint dentry. * (done when source_mnt is moved) * * NOTE: in the table below explains the semantics when a source mount * of a given type is attached to a destination mount of a given type. * --------------------------------------------------------------------------- * | BIND MOUNT OPERATION | * |************************************************************************** * | source-->| shared | private | slave | unbindable | * | dest | | | | | * | | | | | | | * | v | | | | | * |************************************************************************** * | shared | shared (++) | shared (+) | shared(+++)| invalid | * | | | | | | * |non-shared| shared (+) | private | slave (*) | invalid | * *************************************************************************** * A bind operation clones the source mount and mounts the clone on the * destination mount. * * (++) the cloned mount is propagated to all the mounts in the propagation * tree of the destination mount and the cloned mount is added to * the peer group of the source mount. * (+) the cloned mount is created under the destination mount and is marked * as shared. The cloned mount is added to the peer group of the source * mount. * (+++) the mount is propagated to all the mounts in the propagation tree * of the destination mount and the cloned mount is made slave * of the same master as that of the source mount. The cloned mount * is marked as 'shared and slave'. * (*) the cloned mount is made a slave of the same master as that of the * source mount. * * --------------------------------------------------------------------------- * | MOVE MOUNT OPERATION | * |************************************************************************** * | source-->| shared | private | slave | unbindable | * | dest | | | | | * | | | | | | | * | v | | | | | * |************************************************************************** * | shared | shared (+) | shared (+) | shared(+++) | invalid | * | | | | | | * |non-shared| shared (+*) | private | slave (*) | unbindable | * *************************************************************************** * * (+) the mount is moved to the destination. And is then propagated to * all the mounts in the propagation tree of the destination mount. * (+*) the mount is moved to the destination. * (+++) the mount is moved to the destination and is then propagated to * all the mounts belonging to the destination mount's propagation tree. * the mount is marked as 'shared and slave'. * (*) the mount continues to be a slave at the new location. * * if the source mount is a tree, the operations explained above is * applied to each mount in the tree. * Must be called without spinlocks held, since this function can sleep * in allocations. */ static int attach_recursive_mnt(struct mount *source_mnt, struct path *path, struct path *parent_path) { LIST_HEAD(tree_list); struct mount *dest_mnt = real_mount(path->mnt); struct dentry *dest_dentry = path->dentry; struct mount *child, *p; int err; if (IS_MNT_SHARED(dest_mnt)) { err = invent_group_ids(source_mnt, true); if (err) goto out; } err = propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list); if (err) goto out_cleanup_ids; br_write_lock(&vfsmount_lock); if (IS_MNT_SHARED(dest_mnt)) { for (p = source_mnt; p; p = next_mnt(p, source_mnt)) set_mnt_shared(p); } if (parent_path) { detach_mnt(source_mnt, parent_path); attach_mnt(source_mnt, path); touch_mnt_namespace(source_mnt->mnt_ns); } else { mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt); commit_tree(source_mnt); } list_for_each_entry_safe(child, p, &tree_list, mnt_hash) { list_del_init(&child->mnt_hash); commit_tree(child); } br_write_unlock(&vfsmount_lock); return 0; out_cleanup_ids: if (IS_MNT_SHARED(dest_mnt)) cleanup_group_ids(source_mnt, NULL); out: return err; } static int lock_mount(struct path *path) { struct vfsmount *mnt; retry: mutex_lock(&path->dentry->d_inode->i_mutex); if (unlikely(cant_mount(path->dentry))) { mutex_unlock(&path->dentry->d_inode->i_mutex); return -ENOENT; } down_write(&namespace_sem); mnt = lookup_mnt(path); if (likely(!mnt)) return 0; up_write(&namespace_sem); mutex_unlock(&path->dentry->d_inode->i_mutex); path_put(path); path->mnt = mnt; path->dentry = dget(mnt->mnt_root); goto retry; } static void unlock_mount(struct path *path) { up_write(&namespace_sem); mutex_unlock(&path->dentry->d_inode->i_mutex); } static int graft_tree(struct mount *mnt, struct path *path) { if (mnt->mnt.mnt_sb->s_flags & MS_NOUSER) return -EINVAL; if (S_ISDIR(path->dentry->d_inode->i_mode) != S_ISDIR(mnt->mnt.mnt_root->d_inode->i_mode)) return -ENOTDIR; if (d_unlinked(path->dentry)) return -ENOENT; return attach_recursive_mnt(mnt, path, NULL); } /* * Sanity check the flags to change_mnt_propagation. */ static int flags_to_propagation_type(int flags) { int type = flags & ~(MS_REC | MS_SILENT); /* Fail if any non-propagation flags are set */ if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) return 0; /* Only one propagation flag should be set */ if (!is_power_of_2(type)) return 0; return type; } /* * recursively change the type of the mountpoint. */ static int do_change_type(struct path *path, int flag) { struct mount *m; struct mount *mnt = real_mount(path->mnt); int recurse = flag & MS_REC; int type; int err = 0; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (path->dentry != path->mnt->mnt_root) return -EINVAL; type = flags_to_propagation_type(flag); if (!type) return -EINVAL; down_write(&namespace_sem); if (type == MS_SHARED) { err = invent_group_ids(mnt, recurse); if (err) goto out_unlock; } br_write_lock(&vfsmount_lock); for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) change_mnt_propagation(m, type); br_write_unlock(&vfsmount_lock); out_unlock: up_write(&namespace_sem); return err; } /* * do loopback mount. */ static int do_loopback(struct path *path, const char *old_name, int recurse) { LIST_HEAD(umount_list); struct path old_path; struct mount *mnt = NULL, *old; int err = mount_is_safe(path); if (err) return err; if (!old_name || !*old_name) return -EINVAL; err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); if (err) return err; err = -EINVAL; if (mnt_ns_loop(&old_path)) goto out; err = lock_mount(path); if (err) goto out; old = real_mount(old_path.mnt); err = -EINVAL; if (IS_MNT_UNBINDABLE(old)) goto out2; if (!check_mnt(real_mount(path->mnt)) || !check_mnt(old)) goto out2; if (recurse) mnt = copy_tree(old, old_path.dentry, 0); else mnt = clone_mnt(old, old_path.dentry, 0); if (IS_ERR(mnt)) { err = PTR_ERR(mnt); goto out; } err = graft_tree(mnt, path); if (err) { br_write_lock(&vfsmount_lock); umount_tree(mnt, 0, &umount_list); br_write_unlock(&vfsmount_lock); } out2: unlock_mount(path); release_mounts(&umount_list); out: path_put(&old_path); return err; } static int change_mount_flags(struct vfsmount *mnt, int ms_flags) { int error = 0; int readonly_request = 0; if (ms_flags & MS_RDONLY) readonly_request = 1; if (readonly_request == __mnt_is_readonly(mnt)) return 0; if (readonly_request) error = mnt_make_readonly(real_mount(mnt)); else __mnt_unmake_readonly(real_mount(mnt)); return error; } /* * change filesystem flags. dir should be a physical root of filesystem. * If you've mounted a non-root directory somewhere and want to do remount * on it - tough luck. */ static int do_remount(struct path *path, int flags, int mnt_flags, void *data) { int err; struct super_block *sb = path->mnt->mnt_sb; struct mount *mnt = real_mount(path->mnt); if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (!check_mnt(mnt)) return -EINVAL; if (path->dentry != path->mnt->mnt_root) return -EINVAL; err = security_sb_remount(sb, data); if (err) return err; down_write(&sb->s_umount); if (flags & MS_BIND) err = change_mount_flags(path->mnt, flags); else err = do_remount_sb(sb, flags, data, 0); if (!err) { br_write_lock(&vfsmount_lock); mnt_flags |= mnt->mnt.mnt_flags & MNT_PROPAGATION_MASK; mnt->mnt.mnt_flags = mnt_flags; br_write_unlock(&vfsmount_lock); } up_write(&sb->s_umount); if (!err) { br_write_lock(&vfsmount_lock); touch_mnt_namespace(mnt->mnt_ns); br_write_unlock(&vfsmount_lock); } return err; } static inline int tree_contains_unbindable(struct mount *mnt) { struct mount *p; for (p = mnt; p; p = next_mnt(p, mnt)) { if (IS_MNT_UNBINDABLE(p)) return 1; } return 0; } static int do_move_mount(struct path *path, const char *old_name) { struct path old_path, parent_path; struct mount *p; struct mount *old; int err = 0; if (!capable(CAP_SYS_ADMIN)) return -EPERM; if (!old_name || !*old_name) return -EINVAL; err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); if (err) return err; err = lock_mount(path); if (err < 0) goto out; old = real_mount(old_path.mnt); p = real_mount(path->mnt); err = -EINVAL; if (!check_mnt(p) || !check_mnt(old)) goto out1; if (d_unlinked(path->dentry)) goto out1; err = -EINVAL; if (old_path.dentry != old_path.mnt->mnt_root) goto out1; if (!mnt_has_parent(old)) goto out1; if (S_ISDIR(path->dentry->d_inode->i_mode) != S_ISDIR(old_path.dentry->d_inode->i_mode)) goto out1; /* * Don't move a mount residing in a shared parent. */ if (IS_MNT_SHARED(old->mnt_parent)) goto out1; /* * Don't move a mount tree containing unbindable mounts to a destination * mount which is shared. */ if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) goto out1; err = -ELOOP; for (; mnt_has_parent(p); p = p->mnt_parent) if (p == old) goto out1; err = attach_recursive_mnt(old, path, &parent_path); if (err) goto out1; /* if the mount is moved, it should no longer be expire * automatically */ list_del_init(&old->mnt_expire); out1: unlock_mount(path); out: if (!err) path_put(&parent_path); path_put(&old_path); return err; } static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) { int err; const char *subtype = strchr(fstype, '.'); if (subtype) { subtype++; err = -EINVAL; if (!subtype[0]) goto err; } else subtype = ""; mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); err = -ENOMEM; if (!mnt->mnt_sb->s_subtype) goto err; return mnt; err: mntput(mnt); return ERR_PTR(err); } static struct vfsmount * do_kern_mount(const char *fstype, int flags, const char *name, void *data) { struct file_system_type *type = get_fs_type(fstype); struct vfsmount *mnt; if (!type) return ERR_PTR(-ENODEV); mnt = vfs_kern_mount(type, flags, name, data); if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) && !mnt->mnt_sb->s_subtype) mnt = fs_set_subtype(mnt, fstype); put_filesystem(type); return mnt; } /* * add a mount into a namespace's mount tree */ static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) { int err; mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL); err = lock_mount(path); if (err) return err; err = -EINVAL; if (unlikely(!check_mnt(real_mount(path->mnt)))) { /* that's acceptable only for automounts done in private ns */ if (!(mnt_flags & MNT_SHRINKABLE)) goto unlock; /* ... and for those we'd better have mountpoint still alive */ if (!real_mount(path->mnt)->mnt_ns) goto unlock; } /* Refuse the same filesystem on the same mount point */ err = -EBUSY; if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && path->mnt->mnt_root == path->dentry) goto unlock; err = -EINVAL; if (S_ISLNK(newmnt->mnt.mnt_root->d_inode->i_mode)) goto unlock; newmnt->mnt.mnt_flags = mnt_flags; err = graft_tree(newmnt, path); unlock: unlock_mount(path); return err; } /* * create a new mount for userspace and request it to be added into the * namespace's tree */ static int do_new_mount(struct path *path, const char *type, int flags, int mnt_flags, const char *name, void *data) { struct vfsmount *mnt; int err; if (!type) return -EINVAL; /* we need capabilities... */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; mnt = do_kern_mount(type, flags, name, data); if (IS_ERR(mnt)) return PTR_ERR(mnt); err = do_add_mount(real_mount(mnt), path, mnt_flags); if (err) mntput(mnt); return err; } int finish_automount(struct vfsmount *m, struct path *path) { struct mount *mnt = real_mount(m); int err; /* The new mount record should have at least 2 refs to prevent it being * expired before we get a chance to add it */ BUG_ON(mnt_get_count(mnt) < 2); if (m->mnt_sb == path->mnt->mnt_sb && m->mnt_root == path->dentry) { err = -ELOOP; goto fail; } err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); if (!err) return 0; fail: /* remove m from any expiration list it may be on */ if (!list_empty(&mnt->mnt_expire)) { down_write(&namespace_sem); br_write_lock(&vfsmount_lock); list_del_init(&mnt->mnt_expire); br_write_unlock(&vfsmount_lock); up_write(&namespace_sem); } mntput(m); mntput(m); return err; } /** * mnt_set_expiry - Put a mount on an expiration list * @mnt: The mount to list. * @expiry_list: The list to add the mount to. */ void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) { down_write(&namespace_sem); br_write_lock(&vfsmount_lock); list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); br_write_unlock(&vfsmount_lock); up_write(&namespace_sem); } EXPORT_SYMBOL(mnt_set_expiry); /* * process a list of expirable mountpoints with the intent of discarding any * mountpoints that aren't in use and haven't been touched since last we came * here */ void mark_mounts_for_expiry(struct list_head *mounts) { struct mount *mnt, *next; LIST_HEAD(graveyard); LIST_HEAD(umounts); if (list_empty(mounts)) return; down_write(&namespace_sem); br_write_lock(&vfsmount_lock); /* extract from the expiration list every vfsmount that matches the * following criteria: * - only referenced by its parent vfsmount * - still marked for expiry (marked on the last call here; marks are * cleared by mntput()) */ list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { if (!xchg(&mnt->mnt_expiry_mark, 1) || propagate_mount_busy(mnt, 1)) continue; list_move(&mnt->mnt_expire, &graveyard); } while (!list_empty(&graveyard)) { mnt = list_first_entry(&graveyard, struct mount, mnt_expire); touch_mnt_namespace(mnt->mnt_ns); umount_tree(mnt, 1, &umounts); } br_write_unlock(&vfsmount_lock); up_write(&namespace_sem); release_mounts(&umounts); } EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); /* * Ripoff of 'select_parent()' * * search the list of submounts for a given mountpoint, and move any * shrinkable submounts to the 'graveyard' list. */ static int select_submounts(struct mount *parent, struct list_head *graveyard) { struct mount *this_parent = parent; struct list_head *next; int found = 0; repeat: next = this_parent->mnt_mounts.next; resume: while (next != &this_parent->mnt_mounts) { struct list_head *tmp = next; struct mount *mnt = list_entry(tmp, struct mount, mnt_child); next = tmp->next; if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) continue; /* * Descend a level if the d_mounts list is non-empty. */ if (!list_empty(&mnt->mnt_mounts)) { this_parent = mnt; goto repeat; } if (!propagate_mount_busy(mnt, 1)) { list_move_tail(&mnt->mnt_expire, graveyard); found++; } } /* * All done at this level ... ascend and resume the search */ if (this_parent != parent) { next = this_parent->mnt_child.next; this_parent = this_parent->mnt_parent; goto resume; } return found; } /* * process a list of expirable mountpoints with the intent of discarding any * submounts of a specific parent mountpoint * * vfsmount_lock must be held for write */ static void shrink_submounts(struct mount *mnt, struct list_head *umounts) { LIST_HEAD(graveyard); struct mount *m; /* extract submounts of 'mountpoint' from the expiration list */ while (select_submounts(mnt, &graveyard)) { while (!list_empty(&graveyard)) { m = list_first_entry(&graveyard, struct mount, mnt_expire); touch_mnt_namespace(m->mnt_ns); umount_tree(m, 1, umounts); } } } /* * Some copy_from_user() implementations do not return the exact number of * bytes remaining to copy on a fault. But copy_mount_options() requires that. * Note that this function differs from copy_from_user() in that it will oops * on bad values of `to', rather than returning a short copy. */ static long exact_copy_from_user(void *to, const void __user * from, unsigned long n) { char *t = to; const char __user *f = from; char c; if (!access_ok(VERIFY_READ, from, n)) return n; while (n) { if (__get_user(c, f)) { memset(t, 0, n); break; } *t++ = c; f++; n--; } return n; } int copy_mount_options(const void __user * data, unsigned long *where) { int i; unsigned long page; unsigned long size; *where = 0; if (!data) return 0; if (!(page = __get_free_page(GFP_KERNEL))) return -ENOMEM; /* We only care that *some* data at the address the user * gave us is valid. Just in case, we'll zero * the remainder of the page. */ /* copy_from_user cannot cross TASK_SIZE ! */ size = TASK_SIZE - (unsigned long)data; if (size > PAGE_SIZE) size = PAGE_SIZE; i = size - exact_copy_from_user((void *)page, data, size); if (!i) { free_page(page); return -EFAULT; } if (i != PAGE_SIZE) memset((char *)page + i, 0, PAGE_SIZE - i); *where = page; return 0; } int copy_mount_string(const void __user *data, char **where) { char *tmp; if (!data) { *where = NULL; return 0; } tmp = strndup_user(data, PAGE_SIZE); if (IS_ERR(tmp)) return PTR_ERR(tmp); *where = tmp; return 0; } /* * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to * be given to the mount() call (ie: read-only, no-dev, no-suid etc). * * data is a (void *) that can point to any structure up to * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent * information (or be NULL). * * Pre-0.97 versions of mount() didn't have a flags word. * When the flags word was introduced its top half was required * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. * Therefore, if this magic number is present, it carries no information * and must be discarded. */ long do_mount(const char *dev_name, const char *dir_name, const char *type_page, unsigned long flags, void *data_page) { struct path path; int retval = 0; int mnt_flags = 0; /* Discard magic */ if ((flags & MS_MGC_MSK) == MS_MGC_VAL) flags &= ~MS_MGC_MSK; /* Basic sanity checks */ if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE)) return -EINVAL; if (data_page) ((char *)data_page)[PAGE_SIZE - 1] = 0; /* ... and get the mountpoint */ retval = kern_path(dir_name, LOOKUP_FOLLOW, &path); if (retval) return retval; retval = security_sb_mount(dev_name, &path, type_page, flags, data_page); if (retval) goto dput_out; /* Default to relatime unless overriden */ if (!(flags & MS_NOATIME)) mnt_flags |= MNT_RELATIME; /* Separate the per-mountpoint flags */ if (flags & MS_NOSUID) mnt_flags |= MNT_NOSUID; if (flags & MS_NODEV) mnt_flags |= MNT_NODEV; if (flags & MS_NOEXEC) mnt_flags |= MNT_NOEXEC; if (flags & MS_NOATIME) mnt_flags |= MNT_NOATIME; if (flags & MS_NODIRATIME) mnt_flags |= MNT_NODIRATIME; if (flags & MS_STRICTATIME) mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); if (flags & MS_RDONLY) mnt_flags |= MNT_READONLY; flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN | MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT | MS_STRICTATIME); if (flags & MS_REMOUNT) retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags, data_page); else if (flags & MS_BIND) retval = do_loopback(&path, dev_name, flags & MS_REC); else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) retval = do_change_type(&path, flags); else if (flags & MS_MOVE) retval = do_move_mount(&path, dev_name); else retval = do_new_mount(&path, type_page, flags, mnt_flags, dev_name, data_page); dput_out: path_put(&path); return retval; } /* * Assign a sequence number so we can detect when we attempt to bind * mount a reference to an older mount namespace into the current * mount namespace, preventing reference counting loops. A 64bit * number incrementing at 10Ghz will take 12,427 years to wrap which * is effectively never, so we can ignore the possibility. */ static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); static struct mnt_namespace *alloc_mnt_ns(void) { struct mnt_namespace *new_ns; new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); if (!new_ns) return ERR_PTR(-ENOMEM); new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); atomic_set(&new_ns->count, 1); new_ns->root = NULL; INIT_LIST_HEAD(&new_ns->list); init_waitqueue_head(&new_ns->poll); new_ns->event = 0; return new_ns; } /* * Allocate a new namespace structure and populate it with contents * copied from the namespace of the passed in task structure. */ static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns, struct fs_struct *fs) { struct mnt_namespace *new_ns; struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; struct mount *p, *q; struct mount *old = mnt_ns->root; struct mount *new; new_ns = alloc_mnt_ns(); if (IS_ERR(new_ns)) return new_ns; down_write(&namespace_sem); /* First pass: copy the tree topology */ new = copy_tree(old, old->mnt.mnt_root, CL_COPY_ALL | CL_EXPIRE); if (IS_ERR(new)) { up_write(&namespace_sem); kfree(new_ns); return ERR_CAST(new); } new_ns->root = new; br_write_lock(&vfsmount_lock); list_add_tail(&new_ns->list, &new->mnt_list); br_write_unlock(&vfsmount_lock); /* * Second pass: switch the tsk->fs->* elements and mark new vfsmounts * as belonging to new namespace. We have already acquired a private * fs_struct, so tsk->fs->lock is not needed. */ p = old; q = new; while (p) { q->mnt_ns = new_ns; if (fs) { if (&p->mnt == fs->root.mnt) { fs->root.mnt = mntget(&q->mnt); rootmnt = &p->mnt; } if (&p->mnt == fs->pwd.mnt) { fs->pwd.mnt = mntget(&q->mnt); pwdmnt = &p->mnt; } } p = next_mnt(p, old); q = next_mnt(q, new); } up_write(&namespace_sem); if (rootmnt) mntput(rootmnt); if (pwdmnt) mntput(pwdmnt); return new_ns; } struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, struct fs_struct *new_fs) { struct mnt_namespace *new_ns; BUG_ON(!ns); get_mnt_ns(ns); if (!(flags & CLONE_NEWNS)) return ns; new_ns = dup_mnt_ns(ns, new_fs); put_mnt_ns(ns); return new_ns; } /** * create_mnt_ns - creates a private namespace and adds a root filesystem * @mnt: pointer to the new root filesystem mountpoint */ static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) { struct mnt_namespace *new_ns = alloc_mnt_ns(); if (!IS_ERR(new_ns)) { struct mount *mnt = real_mount(m); mnt->mnt_ns = new_ns; new_ns->root = mnt; list_add(&new_ns->list, &mnt->mnt_list); } else { mntput(m); } return new_ns; } struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) { struct mnt_namespace *ns; struct super_block *s; struct path path; int err; ns = create_mnt_ns(mnt); if (IS_ERR(ns)) return ERR_CAST(ns); err = vfs_path_lookup(mnt->mnt_root, mnt, name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); put_mnt_ns(ns); if (err) return ERR_PTR(err); /* trade a vfsmount reference for active sb one */ s = path.mnt->mnt_sb; atomic_inc(&s->s_active); mntput(path.mnt); /* lock the sucker */ down_write(&s->s_umount); /* ... and return the root of (sub)tree on it */ return path.dentry; } EXPORT_SYMBOL(mount_subtree); SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, char __user *, type, unsigned long, flags, void __user *, data) { int ret; char *kernel_type; struct filename *kernel_dir; char *kernel_dev; unsigned long data_page; ret = copy_mount_string(type, &kernel_type); if (ret < 0) goto out_type; kernel_dir = getname(dir_name); if (IS_ERR(kernel_dir)) { ret = PTR_ERR(kernel_dir); goto out_dir; } ret = copy_mount_string(dev_name, &kernel_dev); if (ret < 0) goto out_dev; ret = copy_mount_options(data, &data_page); if (ret < 0) goto out_data; ret = do_mount(kernel_dev, kernel_dir->name, kernel_type, flags, (void *) data_page); free_page(data_page); out_data: kfree(kernel_dev); out_dev: putname(kernel_dir); out_dir: kfree(kernel_type); out_type: return ret; } /* * Return true if path is reachable from root * * namespace_sem or vfsmount_lock is held */ bool is_path_reachable(struct mount *mnt, struct dentry *dentry, const struct path *root) { while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { dentry = mnt->mnt_mountpoint; mnt = mnt->mnt_parent; } return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); } int path_is_under(struct path *path1, struct path *path2) { int res; br_read_lock(&vfsmount_lock); res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); br_read_unlock(&vfsmount_lock); return res; } EXPORT_SYMBOL(path_is_under); /* * pivot_root Semantics: * Moves the root file system of the current process to the directory put_old, * makes new_root as the new root file system of the current process, and sets * root/cwd of all processes which had them on the current root to new_root. * * Restrictions: * The new_root and put_old must be directories, and must not be on the * same file system as the current process root. The put_old must be * underneath new_root, i.e. adding a non-zero number of /.. to the string * pointed to by put_old must yield the same directory as new_root. No other * file system may be mounted on put_old. After all, new_root is a mountpoint. * * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives * in this situation. * * Notes: * - we don't move root/cwd if they are not at the root (reason: if something * cared enough to change them, it's probably wrong to force them elsewhere) * - it's okay to pick a root that isn't the root of a file system, e.g. * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root * first. */ SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, const char __user *, put_old) { struct path new, old, parent_path, root_parent, root; struct mount *new_mnt, *root_mnt; int error; if (!capable(CAP_SYS_ADMIN)) return -EPERM; error = user_path_dir(new_root, &new); if (error) goto out0; error = user_path_dir(put_old, &old); if (error) goto out1; error = security_sb_pivotroot(&old, &new); if (error) goto out2; get_fs_root(current->fs, &root); error = lock_mount(&old); if (error) goto out3; error = -EINVAL; new_mnt = real_mount(new.mnt); root_mnt = real_mount(root.mnt); if (IS_MNT_SHARED(real_mount(old.mnt)) || IS_MNT_SHARED(new_mnt->mnt_parent) || IS_MNT_SHARED(root_mnt->mnt_parent)) goto out4; if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) goto out4; error = -ENOENT; if (d_unlinked(new.dentry)) goto out4; if (d_unlinked(old.dentry)) goto out4; error = -EBUSY; if (new.mnt == root.mnt || old.mnt == root.mnt) goto out4; /* loop, on the same file system */ error = -EINVAL; if (root.mnt->mnt_root != root.dentry) goto out4; /* not a mountpoint */ if (!mnt_has_parent(root_mnt)) goto out4; /* not attached */ if (new.mnt->mnt_root != new.dentry) goto out4; /* not a mountpoint */ if (!mnt_has_parent(new_mnt)) goto out4; /* not attached */ /* make sure we can reach put_old from new_root */ if (!is_path_reachable(real_mount(old.mnt), old.dentry, &new)) goto out4; br_write_lock(&vfsmount_lock); detach_mnt(new_mnt, &parent_path); detach_mnt(root_mnt, &root_parent); /* mount old root on put_old */ attach_mnt(root_mnt, &old); /* mount new_root on / */ attach_mnt(new_mnt, &root_parent); touch_mnt_namespace(current->nsproxy->mnt_ns); br_write_unlock(&vfsmount_lock); chroot_fs_refs(&root, &new); error = 0; out4: unlock_mount(&old); if (!error) { path_put(&root_parent); path_put(&parent_path); } out3: path_put(&root); out2: path_put(&old); out1: path_put(&new); out0: return error; } static void __init init_mount_tree(void) { struct vfsmount *mnt; struct mnt_namespace *ns; struct path root; mnt = do_kern_mount("rootfs", 0, "rootfs", NULL); if (IS_ERR(mnt)) panic("Can't create rootfs"); ns = create_mnt_ns(mnt); if (IS_ERR(ns)) panic("Can't allocate initial namespace"); init_task.nsproxy->mnt_ns = ns; get_mnt_ns(ns); root.mnt = mnt; root.dentry = mnt->mnt_root; set_fs_pwd(current->fs, &root); set_fs_root(current->fs, &root); } void __init mnt_init(void) { unsigned u; int err; init_rwsem(&namespace_sem); mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL); mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC); if (!mount_hashtable) panic("Failed to allocate mount hash table\n"); printk(KERN_INFO "Mount-cache hash table entries: %lu\n", HASH_SIZE); for (u = 0; u < HASH_SIZE; u++) INIT_LIST_HEAD(&mount_hashtable[u]); br_lock_init(&vfsmount_lock); err = sysfs_init(); if (err) printk(KERN_WARNING "%s: sysfs_init error: %d\n", __func__, err); fs_kobj = kobject_create_and_add("fs", NULL); if (!fs_kobj) printk(KERN_WARNING "%s: kobj create error\n", __func__); init_rootfs(); init_mount_tree(); } void put_mnt_ns(struct mnt_namespace *ns) { LIST_HEAD(umount_list); if (!atomic_dec_and_test(&ns->count)) return; down_write(&namespace_sem); br_write_lock(&vfsmount_lock); umount_tree(ns->root, 0, &umount_list); br_write_unlock(&vfsmount_lock); up_write(&namespace_sem); release_mounts(&umount_list); kfree(ns); } struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) { struct vfsmount *mnt; mnt = vfs_kern_mount(type, MS_KERNMOUNT, type->name, data); if (!IS_ERR(mnt)) { /* * it is a longterm mount, don't release mnt until * we unmount before file sys is unregistered */ real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; } return mnt; } EXPORT_SYMBOL_GPL(kern_mount_data); void kern_unmount(struct vfsmount *mnt) { /* release long term mount so mount point can be released */ if (!IS_ERR_OR_NULL(mnt)) { br_write_lock(&vfsmount_lock); real_mount(mnt)->mnt_ns = NULL; br_write_unlock(&vfsmount_lock); mntput(mnt); } } EXPORT_SYMBOL(kern_unmount); bool our_mnt(struct vfsmount *mnt) { return check_mnt(real_mount(mnt)); } static void *mntns_get(struct task_struct *task) { struct mnt_namespace *ns = NULL; struct nsproxy *nsproxy; rcu_read_lock(); nsproxy = task_nsproxy(task); if (nsproxy) { ns = nsproxy->mnt_ns; get_mnt_ns(ns); } rcu_read_unlock(); return ns; } static void mntns_put(void *ns) { put_mnt_ns(ns); } static int mntns_install(struct nsproxy *nsproxy, void *ns) { struct fs_struct *fs = current->fs; struct mnt_namespace *mnt_ns = ns; struct path root; if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_CHROOT)) return -EINVAL; if (fs->users != 1) return -EINVAL; get_mnt_ns(mnt_ns); put_mnt_ns(nsproxy->mnt_ns); nsproxy->mnt_ns = mnt_ns; /* Find the root */ root.mnt = &mnt_ns->root->mnt; root.dentry = mnt_ns->root->mnt.mnt_root; path_get(&root); while(d_mountpoint(root.dentry) && follow_down_one(&root)) ; /* Update the pwd and root */ set_fs_pwd(fs, &root); set_fs_root(fs, &root); path_put(&root); return 0; } const struct proc_ns_operations mntns_operations = { .name = "mnt", .type = CLONE_NEWNS, .get = mntns_get, .put = mntns_put, .install = mntns_install, };