diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 2340 |
1 files changed, 2340 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c new file mode 100644 index 00000000000..bf6b6febc7e --- /dev/null +++ b/fs/namespace.c @@ -0,0 +1,2340 @@ +/* + * 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 <linux/syscalls.h> +#include <linux/slab.h> +#include <linux/sched.h> +#include <linux/smp_lock.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/acct.h> +#include <linux/capability.h> +#include <linux/cpumask.h> +#include <linux/module.h> +#include <linux/sysfs.h> +#include <linux/seq_file.h> +#include <linux/mnt_namespace.h> +#include <linux/namei.h> +#include <linux/nsproxy.h> +#include <linux/security.h> +#include <linux/mount.h> +#include <linux/ramfs.h> +#include <linux/log2.h> +#include <linux/idr.h> +#include <linux/fs_struct.h> +#include <asm/uaccess.h> +#include <asm/unistd.h> +#include "pnode.h" +#include "internal.h" + +#define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) +#define HASH_SIZE (1UL << HASH_SHIFT) + +/* spinlock for vfsmount related operations, inplace of dcache_lock */ +__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); + +static int event; +static DEFINE_IDA(mnt_id_ida); +static DEFINE_IDA(mnt_group_ida); +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); + +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 */ +static int mnt_alloc_id(struct vfsmount *mnt) +{ + int res; + +retry: + ida_pre_get(&mnt_id_ida, GFP_KERNEL); + spin_lock(&vfsmount_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(&vfsmount_lock); + if (res == -EAGAIN) + goto retry; + + return res; +} + +static void mnt_free_id(struct vfsmount *mnt) +{ + int id = mnt->mnt_id; + spin_lock(&vfsmount_lock); + ida_remove(&mnt_id_ida, id); + if (mnt_id_start > id) + mnt_id_start = id; + spin_unlock(&vfsmount_lock); +} + +/* + * Allocate a new peer group ID + * + * mnt_group_ida is protected by namespace_sem + */ +static int mnt_alloc_group_id(struct vfsmount *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 vfsmount *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; +} + +struct vfsmount *alloc_vfsmnt(const char *name) +{ + struct vfsmount *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; + } + + atomic_set(&mnt->mnt_count, 1); + 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_SMP + mnt->mnt_writers = alloc_percpu(int); + if (!mnt->mnt_writers) + goto out_free_devname; +#else + mnt->mnt_writers = 0; +#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 inc_mnt_writers(struct vfsmount *mnt) +{ +#ifdef CONFIG_SMP + (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))++; +#else + mnt->mnt_writers++; +#endif +} + +static inline void dec_mnt_writers(struct vfsmount *mnt) +{ +#ifdef CONFIG_SMP + (*per_cpu_ptr(mnt->mnt_writers, smp_processor_id()))--; +#else + mnt->mnt_writers--; +#endif +} + +static unsigned int count_mnt_writers(struct vfsmount *mnt) +{ +#ifdef CONFIG_SMP + unsigned int count = 0; + int cpu; + + for_each_possible_cpu(cpu) { + count += *per_cpu_ptr(mnt->mnt_writers, cpu); + } + + return count; +#else + return mnt->mnt_writers; +#endif +} + +/* + * 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_want_write - get write access to a mount + * @mnt: 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 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 *mnt) +{ + int ret = 0; + + preempt_disable(); + inc_mnt_writers(mnt); + /* + * The store to inc_mnt_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_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(mnt)) { + dec_mnt_writers(mnt); + ret = -EROFS; + goto out; + } +out: + preempt_enable(); + 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(); + inc_mnt_writers(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); +} +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(); + dec_mnt_writers(mnt); + preempt_enable(); +} +EXPORT_SYMBOL_GPL(mnt_drop_write); + +static int mnt_make_readonly(struct vfsmount *mnt) +{ + int ret = 0; + + spin_lock(&vfsmount_lock); + 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 (count_mnt_writers(mnt) > 0) + ret = -EBUSY; + else + 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_flags &= ~MNT_WRITE_HOLD; + spin_unlock(&vfsmount_lock); + return ret; +} + +static void __mnt_unmake_readonly(struct vfsmount *mnt) +{ + spin_lock(&vfsmount_lock); + mnt->mnt_flags &= ~MNT_READONLY; + spin_unlock(&vfsmount_lock); +} + +void simple_set_mnt(struct vfsmount *mnt, struct super_block *sb) +{ + mnt->mnt_sb = sb; + mnt->mnt_root = dget(sb->s_root); +} + +EXPORT_SYMBOL(simple_set_mnt); + +void free_vfsmnt(struct vfsmount *mnt) +{ + kfree(mnt->mnt_devname); + mnt_free_id(mnt); +#ifdef CONFIG_SMP + free_percpu(mnt->mnt_writers); +#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. + */ +struct vfsmount *__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 vfsmount *p, *found = NULL; + + for (;;) { + tmp = dir ? tmp->next : tmp->prev; + p = NULL; + if (tmp == head) + break; + p = list_entry(tmp, struct vfsmount, mnt_hash); + if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) { + found = p; + break; + } + } + return found; +} + +/* + * lookup_mnt increments the ref count before returning + * the vfsmount struct. + */ +struct vfsmount *lookup_mnt(struct path *path) +{ + struct vfsmount *child_mnt; + spin_lock(&vfsmount_lock); + if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1))) + mntget(child_mnt); + spin_unlock(&vfsmount_lock); + return child_mnt; +} + +static inline int check_mnt(struct vfsmount *mnt) +{ + return mnt->mnt_ns == current->nsproxy->mnt_ns; +} + +static void touch_mnt_namespace(struct mnt_namespace *ns) +{ + if (ns) { + ns->event = ++event; + wake_up_interruptible(&ns->poll); + } +} + +static void __touch_mnt_namespace(struct mnt_namespace *ns) +{ + if (ns && ns->event != event) { + ns->event = event; + wake_up_interruptible(&ns->poll); + } +} + +static void detach_mnt(struct vfsmount *mnt, struct path *old_path) +{ + old_path->dentry = mnt->mnt_mountpoint; + old_path->mnt = mnt->mnt_parent; + mnt->mnt_parent = mnt; + mnt->mnt_mountpoint = mnt->mnt_root; + list_del_init(&mnt->mnt_child); + list_del_init(&mnt->mnt_hash); + old_path->dentry->d_mounted--; +} + +void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry, + struct vfsmount *child_mnt) +{ + child_mnt->mnt_parent = mntget(mnt); + child_mnt->mnt_mountpoint = dget(dentry); + dentry->d_mounted++; +} + +static void attach_mnt(struct vfsmount *mnt, struct path *path) +{ + mnt_set_mountpoint(path->mnt, path->dentry, mnt); + list_add_tail(&mnt->mnt_hash, mount_hashtable + + hash(path->mnt, path->dentry)); + list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts); +} + +/* + * the caller must hold vfsmount_lock + */ +static void commit_tree(struct vfsmount *mnt) +{ + struct vfsmount *parent = mnt->mnt_parent; + struct vfsmount *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_mountpoint)); + list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); + touch_mnt_namespace(n); +} + +static struct vfsmount *next_mnt(struct vfsmount *p, struct vfsmount *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 vfsmount, mnt_child); +} + +static struct vfsmount *skip_mnt_tree(struct vfsmount *p) +{ + struct list_head *prev = p->mnt_mounts.prev; + while (prev != &p->mnt_mounts) { + p = list_entry(prev, struct vfsmount, mnt_child); + prev = p->mnt_mounts.prev; + } + return p; +} + +static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root, + int flag) +{ + struct super_block *sb = old->mnt_sb; + struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname); + + if (mnt) { + 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) { + int err = mnt_alloc_group_id(mnt); + if (err) + goto out_free; + } + + mnt->mnt_flags = old->mnt_flags; + atomic_inc(&sb->s_active); + mnt->mnt_sb = sb; + mnt->mnt_root = dget(root); + mnt->mnt_mountpoint = mnt->mnt_root; + mnt->mnt_parent = mnt; + + 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_PROPAGATION) || 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 NULL; +} + +static inline void __mntput(struct vfsmount *mnt) +{ + struct super_block *sb = mnt->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. + */ + /* + * atomic_dec_and_lock() used to deal with ->mnt_count decrements + * provides barriers, so count_mnt_writers() below is safe. AV + */ + WARN_ON(count_mnt_writers(mnt)); + dput(mnt->mnt_root); + free_vfsmnt(mnt); + deactivate_super(sb); +} + +void mntput_no_expire(struct vfsmount *mnt) +{ +repeat: + if (atomic_dec_and_lock(&mnt->mnt_count, &vfsmount_lock)) { + if (likely(!mnt->mnt_pinned)) { + spin_unlock(&vfsmount_lock); + __mntput(mnt); + return; + } + atomic_add(mnt->mnt_pinned + 1, &mnt->mnt_count); + mnt->mnt_pinned = 0; + spin_unlock(&vfsmount_lock); + acct_auto_close_mnt(mnt); + security_sb_umount_close(mnt); + goto repeat; + } +} + +EXPORT_SYMBOL(mntput_no_expire); + +void mnt_pin(struct vfsmount *mnt) +{ + spin_lock(&vfsmount_lock); + mnt->mnt_pinned++; + spin_unlock(&vfsmount_lock); +} + +EXPORT_SYMBOL(mnt_pin); + +void mnt_unpin(struct vfsmount *mnt) +{ + spin_lock(&vfsmount_lock); + if (mnt->mnt_pinned) { + atomic_inc(&mnt->mnt_count); + mnt->mnt_pinned--; + } + spin_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 vfsmount *mnt) +{ + const char *options; + + rcu_read_lock(); + options = rcu_dereference(mnt->mnt_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 */ +static void *m_start(struct seq_file *m, loff_t *pos) +{ + struct proc_mounts *p = m->private; + + 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 = m->private; + + return seq_list_next(v, &p->ns->list, pos); +} + +static void m_stop(struct seq_file *m, void *v) +{ + up_read(&namespace_sem); +} + +struct proc_fs_info { + int flag; + const char *str; +}; + +static int show_sb_opts(struct seq_file *m, struct super_block *sb) +{ + static const struct proc_fs_info fs_info[] = { + { MS_SYNCHRONOUS, ",sync" }, + { MS_DIRSYNC, ",dirsync" }, + { MS_MANDLOCK, ",mand" }, + { 0, NULL } + }; + const struct proc_fs_info *fs_infop; + + for (fs_infop = fs_info; fs_infop->flag; fs_infop++) { + if (sb->s_flags & fs_infop->flag) + seq_puts(m, fs_infop->str); + } + + return security_sb_show_options(m, sb); +} + +static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt) +{ + static const struct proc_fs_info mnt_info[] = { + { MNT_NOSUID, ",nosuid" }, + { MNT_NODEV, ",nodev" }, + { MNT_NOEXEC, ",noexec" }, + { MNT_NOATIME, ",noatime" }, + { MNT_NODIRATIME, ",nodiratime" }, + { MNT_RELATIME, ",relatime" }, + { MNT_STRICTATIME, ",strictatime" }, + { 0, NULL } + }; + const struct proc_fs_info *fs_infop; + + for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) { + if (mnt->mnt_flags & fs_infop->flag) + seq_puts(m, fs_infop->str); + } +} + +static void show_type(struct seq_file *m, struct super_block *sb) +{ + mangle(m, sb->s_type->name); + if (sb->s_subtype && sb->s_subtype[0]) { + seq_putc(m, '.'); + mangle(m, sb->s_subtype); + } +} + +static int show_vfsmnt(struct seq_file *m, void *v) +{ + struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); + int err = 0; + struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; + + mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); + seq_putc(m, ' '); + seq_path(m, &mnt_path, " \t\n\\"); + seq_putc(m, ' '); + show_type(m, mnt->mnt_sb); + seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw"); + err = show_sb_opts(m, mnt->mnt_sb); + if (err) + goto out; + show_mnt_opts(m, mnt); + if (mnt->mnt_sb->s_op->show_options) + err = mnt->mnt_sb->s_op->show_options(m, mnt); + seq_puts(m, " 0 0\n"); +out: + return err; +} + +const struct seq_operations mounts_op = { + .start = m_start, + .next = m_next, + .stop = m_stop, + .show = show_vfsmnt +}; + +static int show_mountinfo(struct seq_file *m, void *v) +{ + struct proc_mounts *p = m->private; + struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); + struct super_block *sb = mnt->mnt_sb; + struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; + struct path root = p->root; + int err = 0; + + seq_printf(m, "%i %i %u:%u ", mnt->mnt_id, mnt->mnt_parent->mnt_id, + MAJOR(sb->s_dev), MINOR(sb->s_dev)); + seq_dentry(m, mnt->mnt_root, " \t\n\\"); + seq_putc(m, ' '); + seq_path_root(m, &mnt_path, &root, " \t\n\\"); + if (root.mnt != p->root.mnt || root.dentry != p->root.dentry) { + /* + * Mountpoint is outside root, discard that one. Ugly, + * but less so than trying to do that in iterator in a + * race-free way (due to renames). + */ + return SEQ_SKIP; + } + seq_puts(m, mnt->mnt_flags & MNT_READONLY ? " ro" : " rw"); + show_mnt_opts(m, mnt); + + /* Tagged fields ("foo:X" or "bar") */ + if (IS_MNT_SHARED(mnt)) + seq_printf(m, " shared:%i", mnt->mnt_group_id); + if (IS_MNT_SLAVE(mnt)) { + int master = mnt->mnt_master->mnt_group_id; + int dom = get_dominating_id(mnt, &p->root); + seq_printf(m, " master:%i", master); + if (dom && dom != master) + seq_printf(m, " propagate_from:%i", dom); + } + if (IS_MNT_UNBINDABLE(mnt)) + seq_puts(m, " unbindable"); + + /* Filesystem specific data */ + seq_puts(m, " - "); + show_type(m, sb); + seq_putc(m, ' '); + mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none"); + seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw"); + err = show_sb_opts(m, sb); + if (err) + goto out; + if (sb->s_op->show_options) + err = sb->s_op->show_options(m, mnt); + seq_putc(m, '\n'); +out: + return err; +} + +const struct seq_operations mountinfo_op = { + .start = m_start, + .next = m_next, + .stop = m_stop, + .show = show_mountinfo, +}; + +static int show_vfsstat(struct seq_file *m, void *v) +{ + struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list); + struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt }; + int err = 0; + + /* device */ + if (mnt->mnt_devname) { + seq_puts(m, "device "); + mangle(m, mnt->mnt_devname); + } else + seq_puts(m, "no device"); + + /* mount point */ + seq_puts(m, " mounted on "); + seq_path(m, &mnt_path, " \t\n\\"); + seq_putc(m, ' '); + + /* file system type */ + seq_puts(m, "with fstype "); + show_type(m, mnt->mnt_sb); + + /* optional statistics */ + if (mnt->mnt_sb->s_op->show_stats) { + seq_putc(m, ' '); + err = mnt->mnt_sb->s_op->show_stats(m, mnt); + } + + seq_putc(m, '\n'); + return err; +} + +const struct seq_operations mountstats_op = { + .start = m_start, + .next = m_next, + .stop = m_stop, + .show = show_vfsstat, +}; +#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 *mnt) +{ + int actual_refs = 0; + int minimum_refs = 0; + struct vfsmount *p; + + spin_lock(&vfsmount_lock); + for (p = mnt; p; p = next_mnt(p, mnt)) { + actual_refs += atomic_read(&p->mnt_count); + minimum_refs += 2; + } + spin_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); + spin_lock(&vfsmount_lock); + if (propagate_mount_busy(mnt, 2)) + ret = 0; + spin_unlock(&vfsmount_lock); + up_read(&namespace_sem); + return ret; +} + +EXPORT_SYMBOL(may_umount); + +void release_mounts(struct list_head *head) +{ + struct vfsmount *mnt; + while (!list_empty(head)) { + mnt = list_first_entry(head, struct vfsmount, mnt_hash); + list_del_init(&mnt->mnt_hash); + if (mnt->mnt_parent != mnt) { + struct dentry *dentry; + struct vfsmount *m; + spin_lock(&vfsmount_lock); + dentry = mnt->mnt_mountpoint; + m = mnt->mnt_parent; + mnt->mnt_mountpoint = mnt->mnt_root; + mnt->mnt_parent = mnt; + m->mnt_ghosts--; + spin_unlock(&vfsmount_lock); + dput(dentry); + mntput(m); + } + mntput(mnt); + } +} + +void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill) +{ + struct vfsmount *p; + + for (p = mnt; p; p = next_mnt(p, mnt)) + list_move(&p->mnt_hash, kill); + + if (propagate) + propagate_umount(kill); + + list_for_each_entry(p, kill, 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 (p->mnt_parent != p) { + p->mnt_parent->mnt_ghosts++; + p->mnt_mountpoint->d_mounted--; + } + change_mnt_propagation(p, MS_PRIVATE); + } +} + +static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts); + +static int do_umount(struct vfsmount *mnt, int flags) +{ + struct super_block *sb = mnt->mnt_sb; + int retval; + LIST_HEAD(umount_list); + + retval = security_sb_umount(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 == current->fs->root.mnt || + flags & (MNT_FORCE | MNT_DETACH)) + return -EINVAL; + + if (atomic_read(&mnt->mnt_count) != 2) + return -EBUSY; + + 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 == 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); + spin_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; + } + spin_unlock(&vfsmount_lock); + if (retval) + security_sb_umount_busy(mnt); + 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; + 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; + retval = -EINVAL; + if (path.dentry != path.mnt->mnt_root) + goto dput_and_out; + if (!check_mnt(path.mnt)) + goto dput_and_out; + + retval = -EPERM; + if (!capable(CAP_SYS_ADMIN)) + goto dput_and_out; + + retval = do_umount(path.mnt, flags); +dput_and_out: + /* we mustn't call path_put() as that would clear mnt_expiry_mark */ + dput(path.dentry); + mntput_no_expire(path.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 +} + +struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry, + int flag) +{ + struct vfsmount *res, *p, *q, *r, *s; + struct path path; + + if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt)) + return NULL; + + res = q = clone_mnt(mnt, dentry, flag); + if (!q) + goto Enomem; + q->mnt_mountpoint = mnt->mnt_mountpoint; + + p = mnt; + list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { + 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; + path.dentry = p->mnt_mountpoint; + q = clone_mnt(p, p->mnt_root, flag); + if (!q) + goto Enomem; + spin_lock(&vfsmount_lock); + list_add_tail(&q->mnt_list, &res->mnt_list); + attach_mnt(q, &path); + spin_unlock(&vfsmount_lock); + } + } + return res; +Enomem: + if (res) { + LIST_HEAD(umount_list); + spin_lock(&vfsmount_lock); + umount_tree(res, 0, &umount_list); + spin_unlock(&vfsmount_lock); + release_mounts(&umount_list); + } + return NULL; +} + +struct vfsmount *collect_mounts(struct path *path) +{ + struct vfsmount *tree; + down_write(&namespace_sem); + tree = copy_tree(path->mnt, path->dentry, CL_COPY_ALL | CL_PRIVATE); + up_write(&namespace_sem); + return tree; +} + +void drop_collected_mounts(struct vfsmount *mnt) +{ + LIST_HEAD(umount_list); + down_write(&namespace_sem); + spin_lock(&vfsmount_lock); + umount_tree(mnt, 0, &umount_list); + spin_unlock(&vfsmount_lock); + up_write(&namespace_sem); + release_mounts(&umount_list); +} + +static void cleanup_group_ids(struct vfsmount *mnt, struct vfsmount *end) +{ + struct vfsmount *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 vfsmount *mnt, bool recurse) +{ + struct vfsmount *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 vfsmount *source_mnt, + struct path *path, struct path *parent_path) +{ + LIST_HEAD(tree_list); + struct vfsmount *dest_mnt = path->mnt; + struct dentry *dest_dentry = path->dentry; + struct vfsmount *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; + + spin_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(parent_path->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); + } + spin_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 graft_tree(struct vfsmount *mnt, struct path *path) +{ + int err; + if (mnt->mnt_sb->s_flags & MS_NOUSER) + return -EINVAL; + + if (S_ISDIR(path->dentry->d_inode->i_mode) != + S_ISDIR(mnt->mnt_root->d_inode->i_mode)) + return -ENOTDIR; + + err = -ENOENT; + mutex_lock(&path->dentry->d_inode->i_mutex); + if (IS_DEADDIR(path->dentry->d_inode)) + goto out_unlock; + + err = security_sb_check_sb(mnt, path); + if (err) + goto out_unlock; + + err = -ENOENT; + if (!d_unlinked(path->dentry)) + err = attach_recursive_mnt(mnt, path, NULL); +out_unlock: + mutex_unlock(&path->dentry->d_inode->i_mutex); + if (!err) + security_sb_post_addmount(mnt, path); + return err; +} + +/* + * recursively change the type of the mountpoint. + */ +static int do_change_type(struct path *path, int flag) +{ + struct vfsmount *m, *mnt = path->mnt; + int recurse = flag & MS_REC; + int type = flag & ~MS_REC; + int err = 0; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (path->dentry != path->mnt->mnt_root) + return -EINVAL; + + down_write(&namespace_sem); + if (type == MS_SHARED) { + err = invent_group_ids(mnt, recurse); + if (err) + goto out_unlock; + } + + spin_lock(&vfsmount_lock); + for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) + change_mnt_propagation(m, type); + spin_unlock(&vfsmount_lock); + + out_unlock: + up_write(&namespace_sem); + return err; +} + +/* + * do loopback mount. + */ +static int do_loopback(struct path *path, char *old_name, + int recurse) +{ + struct path old_path; + struct vfsmount *mnt = NULL; + int err = mount_is_safe(path); + if (err) + return err; + if (!old_name || !*old_name) + return -EINVAL; + err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); + if (err) + return err; + + down_write(&namespace_sem); + err = -EINVAL; + if (IS_MNT_UNBINDABLE(old_path.mnt)) + goto out; + + if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) + goto out; + + err = -ENOMEM; + if (recurse) + mnt = copy_tree(old_path.mnt, old_path.dentry, 0); + else + mnt = clone_mnt(old_path.mnt, old_path.dentry, 0); + + if (!mnt) + goto out; + + err = graft_tree(mnt, path); + if (err) { + LIST_HEAD(umount_list); + spin_lock(&vfsmount_lock); + umount_tree(mnt, 0, &umount_list); + spin_unlock(&vfsmount_lock); + release_mounts(&umount_list); + } + +out: + up_write(&namespace_sem); + 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(mnt); + else + __mnt_unmake_readonly(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; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + if (!check_mnt(path->mnt)) + return -EINVAL; + + if (path->dentry != path->mnt->mnt_root) + return -EINVAL; + + 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) { + spin_lock(&vfsmount_lock); + mnt_flags |= path->mnt->mnt_flags & MNT_PNODE_MASK; + path->mnt->mnt_flags = mnt_flags; + spin_unlock(&vfsmount_lock); + } + up_write(&sb->s_umount); + if (!err) { + security_sb_post_remount(path->mnt, flags, data); + + spin_lock(&vfsmount_lock); + touch_mnt_namespace(path->mnt->mnt_ns); + spin_unlock(&vfsmount_lock); + } + return err; +} + +static inline int tree_contains_unbindable(struct vfsmount *mnt) +{ + struct vfsmount *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, char *old_name) +{ + struct path old_path, parent_path; + struct vfsmount *p; + 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; + + down_write(&namespace_sem); + while (d_mountpoint(path->dentry) && + follow_down(path)) + ; + err = -EINVAL; + if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt)) + goto out; + + err = -ENOENT; + mutex_lock(&path->dentry->d_inode->i_mutex); + if (IS_DEADDIR(path->dentry->d_inode)) + goto out1; + + if (d_unlinked(path->dentry)) + goto out1; + + err = -EINVAL; + if (old_path.dentry != old_path.mnt->mnt_root) + goto out1; + + if (old_path.mnt == old_path.mnt->mnt_parent) + 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 (old_path.mnt->mnt_parent && + IS_MNT_SHARED(old_path.mnt->mnt_parent)) + goto out1; + /* + * Don't move a mount tree containing unbindable mounts to a destination + * mount which is shared. + */ + if (IS_MNT_SHARED(path->mnt) && + tree_contains_unbindable(old_path.mnt)) + goto out1; + err = -ELOOP; + for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent) + if (p == old_path.mnt) + goto out1; + + err = attach_recursive_mnt(old_path.mnt, path, &parent_path); + if (err) + goto out1; + + /* if the mount is moved, it should no longer be expire + * automatically */ + list_del_init(&old_path.mnt->mnt_expire); +out1: + mutex_unlock(&path->dentry->d_inode->i_mutex); +out: + up_write(&namespace_sem); + if (!err) + path_put(&parent_path); + path_put(&old_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, char *type, int flags, + int mnt_flags, char *name, void *data) +{ + struct vfsmount *mnt; + + if (!type) + return -EINVAL; + + /* we need capabilities... */ + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + lock_kernel(); + mnt = do_kern_mount(type, flags, name, data); + unlock_kernel(); + if (IS_ERR(mnt)) + return PTR_ERR(mnt); + + return do_add_mount(mnt, path, mnt_flags, NULL); +} + +/* + * add a mount into a namespace's mount tree + * - provide the option of adding the new mount to an expiration list + */ +int do_add_mount(struct vfsmount *newmnt, struct path *path, + int mnt_flags, struct list_head *fslist) +{ + int err; + + mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD); + + down_write(&namespace_sem); + /* Something was mounted here while we slept */ + while (d_mountpoint(path->dentry) && + follow_down(path)) + ; + err = -EINVAL; + if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt)) + goto unlock; + + /* Refuse the same filesystem on the same mount point */ + err = -EBUSY; + if (path->mnt->mnt_sb == newmnt->mnt_sb && + path->mnt->mnt_root == path->dentry) + goto unlock; + + err = -EINVAL; + if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode)) + goto unlock; + + newmnt->mnt_flags = mnt_flags; + if ((err = graft_tree(newmnt, path))) + goto unlock; + + if (fslist) /* add to the specified expiration list */ + list_add_tail(&newmnt->mnt_expire, fslist); + + up_write(&namespace_sem); + return 0; + +unlock: + up_write(&namespace_sem); + mntput(newmnt); + return err; +} + +EXPORT_SYMBOL_GPL(do_add_mount); + +/* + * 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 vfsmount *mnt, *next; + LIST_HEAD(graveyard); + LIST_HEAD(umounts); + + if (list_empty(mounts)) + return; + + down_write(&namespace_sem); + spin_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 vfsmount, mnt_expire); + touch_mnt_namespace(mnt->mnt_ns); + umount_tree(mnt, 1, &umounts); + } + spin_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 vfsmount *parent, struct list_head *graveyard) +{ + struct vfsmount *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 vfsmount *mnt = list_entry(tmp, struct vfsmount, mnt_child); + + next = tmp->next; + if (!(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 + */ +static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts) +{ + LIST_HEAD(graveyard); + struct vfsmount *m; + + /* extract submounts of 'mountpoint' from the expiration list */ + while (select_submounts(mnt, &graveyard)) { + while (!list_empty(&graveyard)) { + m = list_first_entry(&graveyard, struct vfsmount, + 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(char *dev_name, char *dir_name, 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_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; +} + +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); + 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 vfsmount *p, *q; + + new_ns = alloc_mnt_ns(); + if (IS_ERR(new_ns)) + return new_ns; + + down_write(&namespace_sem); + /* First pass: copy the tree topology */ + new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root, + CL_COPY_ALL | CL_EXPIRE); + if (!new_ns->root) { + up_write(&namespace_sem); + kfree(new_ns); + return ERR_PTR(-ENOMEM); + } + spin_lock(&vfsmount_lock); + list_add_tail(&new_ns->list, &new_ns->root->mnt_list); + spin_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 = mnt_ns->root; + q = new_ns->root; + while (p) { + q->mnt_ns = new_ns; + if (fs) { + if (p == fs->root.mnt) { + rootmnt = p; + fs->root.mnt = mntget(q); + } + if (p == fs->pwd.mnt) { + pwdmnt = p; + fs->pwd.mnt = mntget(q); + } + } + p = next_mnt(p, mnt_ns->root); + q = next_mnt(q, new_ns->root); + } + 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 + */ +struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt) +{ + struct mnt_namespace *new_ns; + + new_ns = alloc_mnt_ns(); + if (!IS_ERR(new_ns)) { + mnt->mnt_ns = new_ns; + new_ns->root = mnt; + list_add(&new_ns->list, &new_ns->root->mnt_list); + } + return new_ns; +} +EXPORT_SYMBOL(create_mnt_ns); + +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; + char *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, 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; +} + +/* + * 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 vfsmount *tmp; + struct path new, old, parent_path, root_parent, root; + int error; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + error = user_path_dir(new_root, &new); + if (error) + goto out0; + error = -EINVAL; + if (!check_mnt(new.mnt)) + goto out1; + + error = user_path_dir(put_old, &old); + if (error) + goto out1; + + error = security_sb_pivotroot(&old, &new); + if (error) { + path_put(&old); + goto out1; + } + + read_lock(¤t->fs->lock); + root = current->fs->root; + path_get(¤t->fs->root); + read_unlock(¤t->fs->lock); + down_write(&namespace_sem); + mutex_lock(&old.dentry->d_inode->i_mutex); + error = -EINVAL; + if (IS_MNT_SHARED(old.mnt) || + IS_MNT_SHARED(new.mnt->mnt_parent) || + IS_MNT_SHARED(root.mnt->mnt_parent)) + goto out2; + if (!check_mnt(root.mnt)) + goto out2; + error = -ENOENT; + if (IS_DEADDIR(new.dentry->d_inode)) + goto out2; + if (d_unlinked(new.dentry)) + goto out2; + if (d_unlinked(old.dentry)) + goto out2; + error = -EBUSY; + if (new.mnt == root.mnt || + old.mnt == root.mnt) + goto out2; /* loop, on the same file system */ + error = -EINVAL; + if (root.mnt->mnt_root != root.dentry) + goto out2; /* not a mountpoint */ + if (root.mnt->mnt_parent == root.mnt) + goto out2; /* not attached */ + if (new.mnt->mnt_root != new.dentry) + goto out2; /* not a mountpoint */ + if (new.mnt->mnt_parent == new.mnt) + goto out2; /* not attached */ + /* make sure we can reach put_old from new_root */ + tmp = old.mnt; + spin_lock(&vfsmount_lock); + if (tmp != new.mnt) { + for (;;) { + if (tmp->mnt_parent == tmp) + goto out3; /* already mounted on put_old */ + if (tmp->mnt_parent == new.mnt) + break; + tmp = tmp->mnt_parent; + } + if (!is_subdir(tmp->mnt_mountpoint, new.dentry)) + goto out3; + } else if (!is_subdir(old.dentry, new.dentry)) + goto out3; + 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); + spin_unlock(&vfsmount_lock); + chroot_fs_refs(&root, &new); + security_sb_post_pivotroot(&root, &new); + error = 0; + path_put(&root_parent); + path_put(&parent_path); +out2: + mutex_unlock(&old.dentry->d_inode->i_mutex); + up_write(&namespace_sem); + path_put(&root); + path_put(&old); +out1: + path_put(&new); +out0: + return error; +out3: + spin_unlock(&vfsmount_lock); + goto out2; +} + +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 = ns->root; + root.dentry = ns->root->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 vfsmount), + 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("Mount-cache hash table entries: %lu\n", HASH_SIZE); + + for (u = 0; u < HASH_SIZE; u++) + INIT_LIST_HEAD(&mount_hashtable[u]); + + 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) +{ + struct vfsmount *root; + LIST_HEAD(umount_list); + + if (!atomic_dec_and_lock(&ns->count, &vfsmount_lock)) + return; + root = ns->root; + ns->root = NULL; + spin_unlock(&vfsmount_lock); + down_write(&namespace_sem); + spin_lock(&vfsmount_lock); + umount_tree(root, 0, &umount_list); + spin_unlock(&vfsmount_lock); + up_write(&namespace_sem); + release_mounts(&umount_list); + kfree(ns); +} +EXPORT_SYMBOL(put_mnt_ns); |