root/fs/namespace.c
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DEFINITIONS
This source file includes following definitions.
- hash
- mnt_alloc_id
- mnt_free_id
- mnt_alloc_group_id
- mnt_release_group_id
- alloc_vfsmnt
- __mnt_is_readonly
- init_mnt_writers
- unlock_mnt_writers
- __clear_mnt_count
- use_cpu_writer_for_mount
- mnt_want_write
- lock_mnt_writers
- handle_write_count_underflow
- mnt_drop_write
- mnt_make_readonly
- __mnt_unmake_readonly
- simple_set_mnt
- free_vfsmnt
- __lookup_mnt
- lookup_mnt
- check_mnt
- touch_mnt_namespace
- __touch_mnt_namespace
- detach_mnt
- mnt_set_mountpoint
- attach_mnt
- commit_tree
- next_mnt
- skip_mnt_tree
- clone_mnt
- __mntput
- mntput_no_expire
- mnt_pin
- mnt_unpin
- mangle
- generic_show_options
- save_mount_options
- m_start
- m_next
- m_stop
- show_sb_opts
- show_mnt_opts
- show_type
- show_vfsmnt
- show_mountinfo
- show_vfsstat
- may_umount_tree
- may_umount
- release_mounts
- umount_tree
- do_umount
- sys_umount
- sys_oldumount
- mount_is_safe
- copy_tree
- collect_mounts
- drop_collected_mounts
- cleanup_group_ids
- invent_group_ids
- attach_recursive_mnt
- graft_tree
- do_change_type
- do_loopback
- change_mount_flags
- do_remount
- tree_contains_unbindable
- do_move_mount
- do_new_mount
- do_add_mount
- mark_mounts_for_expiry
- select_submounts
- shrink_submounts
- exact_copy_from_user
- copy_mount_options
- do_mount
- dup_mnt_ns
- copy_mnt_ns
- sys_mount
- set_fs_root
- set_fs_pwd
- chroot_fs_refs
- sys_pivot_root
- init_mount_tree
- mnt_init
- __put_mnt_ns
/*
* 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/security.h>
#include <linux/mount.h>
#include <linux/ramfs.h>
#include <linux/log2.h>
#include <linux/idr.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 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(&mnt_id_ida, &mnt->mnt_id);
spin_unlock(&vfsmount_lock);
if (res == -EAGAIN)
goto retry;
return res;
}
static void mnt_free_id(struct vfsmount *mnt)
{
spin_lock(&vfsmount_lock);
ida_remove(&mnt_id_ida, mnt->mnt_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)
{
if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
return -ENOMEM;
return ida_get_new_above(&mnt_group_ida, 1, &mnt->mnt_group_id);
}
/*
* Release a peer group ID
*/
void mnt_release_group_id(struct vfsmount *mnt)
{
ida_remove(&mnt_group_ida, mnt->mnt_group_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);
atomic_set(&mnt->__mnt_writers, 0);
}
return mnt;
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);
struct mnt_writer {
/*
* If holding multiple instances of this lock, they
* must be ordered by cpu number.
*/
spinlock_t lock;
struct lock_class_key lock_class; /* compiles out with !lockdep */
unsigned long count;
struct vfsmount *mnt;
} ____cacheline_aligned_in_smp;
static DEFINE_PER_CPU(struct mnt_writer, mnt_writers);
static int __init init_mnt_writers(void)
{
int cpu;
for_each_possible_cpu(cpu) {
struct mnt_writer *writer = &per_cpu(mnt_writers, cpu);
spin_lock_init(&writer->lock);
lockdep_set_class(&writer->lock, &writer->lock_class);
writer->count = 0;
}
return 0;
}
fs_initcall(init_mnt_writers);
static void unlock_mnt_writers(void)
{
int cpu;
struct mnt_writer *cpu_writer;
for_each_possible_cpu(cpu) {
cpu_writer = &per_cpu(mnt_writers, cpu);
spin_unlock(&cpu_writer->lock);
}
}
static inline void __clear_mnt_count(struct mnt_writer *cpu_writer)
{
if (!cpu_writer->mnt)
return;
/*
* This is in case anyone ever leaves an invalid,
* old ->mnt and a count of 0.
*/
if (!cpu_writer->count)
return;
atomic_add(cpu_writer->count, &cpu_writer->mnt->__mnt_writers);
cpu_writer->count = 0;
}
/*
* must hold cpu_writer->lock
*/
static inline void use_cpu_writer_for_mount(struct mnt_writer *cpu_writer,
struct vfsmount *mnt)
{
if (cpu_writer->mnt == mnt)
return;
__clear_mnt_count(cpu_writer);
cpu_writer->mnt = mnt;
}
/*
* 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;
struct mnt_writer *cpu_writer;
cpu_writer = &get_cpu_var(mnt_writers);
spin_lock(&cpu_writer->lock);
if (__mnt_is_readonly(mnt)) {
ret = -EROFS;
goto out;
}
use_cpu_writer_for_mount(cpu_writer, mnt);
cpu_writer->count++;
out:
spin_unlock(&cpu_writer->lock);
put_cpu_var(mnt_writers);
return ret;
}
EXPORT_SYMBOL_GPL(mnt_want_write);
static void lock_mnt_writers(void)
{
int cpu;
struct mnt_writer *cpu_writer;
for_each_possible_cpu(cpu) {
cpu_writer = &per_cpu(mnt_writers, cpu);
spin_lock(&cpu_writer->lock);
__clear_mnt_count(cpu_writer);
cpu_writer->mnt = NULL;
}
}
/*
* These per-cpu write counts are not guaranteed to have
* matched increments and decrements on any given cpu.
* A file open()ed for write on one cpu and close()d on
* another cpu will imbalance this count. Make sure it
* does not get too far out of whack.
*/
static void handle_write_count_underflow(struct vfsmount *mnt)
{
if (atomic_read(&mnt->__mnt_writers) >=
MNT_WRITER_UNDERFLOW_LIMIT)
return;
/*
* It isn't necessary to hold all of the locks
* at the same time, but doing it this way makes
* us share a lot more code.
*/
lock_mnt_writers();
/*
* vfsmount_lock is for mnt_flags.
*/
spin_lock(&vfsmount_lock);
/*
* If coalescing the per-cpu writer counts did not
* get us back to a positive writer count, we have
* a bug.
*/
if ((atomic_read(&mnt->__mnt_writers) < 0) &&
!(mnt->mnt_flags & MNT_IMBALANCED_WRITE_COUNT)) {
WARN(1, KERN_DEBUG "leak detected on mount(%p) writers "
"count: %d\n",
mnt, atomic_read(&mnt->__mnt_writers));
/* use the flag to keep the dmesg spam down */
mnt->mnt_flags |= MNT_IMBALANCED_WRITE_COUNT;
}
spin_unlock(&vfsmount_lock);
unlock_mnt_writers();
}
/**
* 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)
{
int must_check_underflow = 0;
struct mnt_writer *cpu_writer;
cpu_writer = &get_cpu_var(mnt_writers);
spin_lock(&cpu_writer->lock);
use_cpu_writer_for_mount(cpu_writer, mnt);
if (cpu_writer->count > 0) {
cpu_writer->count--;
} else {
must_check_underflow = 1;
atomic_dec(&mnt->__mnt_writers);
}
spin_unlock(&cpu_writer->lock);
/*
* Logically, we could call this each time,
* but the __mnt_writers cacheline tends to
* be cold, and makes this expensive.
*/
if (must_check_underflow)
handle_write_count_underflow(mnt);
/*
* This could be done right after the spinlock
* is taken because the spinlock keeps us on
* the cpu, and disables preemption. However,
* putting it here bounds the amount that
* __mnt_writers can underflow. Without it,
* we could theoretically wrap __mnt_writers.
*/
put_cpu_var(mnt_writers);
}
EXPORT_SYMBOL_GPL(mnt_drop_write);
static int mnt_make_readonly(struct vfsmount *mnt)
{
int ret = 0;
lock_mnt_writers();
/*
* With all the locks held, this value is stable
*/
if (atomic_read(&mnt->__mnt_writers) > 0) {
ret = -EBUSY;
goto out;
}
/*
* nobody can do a successful mnt_want_write() with all
* of the counts in MNT_DENIED_WRITE and the locks held.
*/
spin_lock(&vfsmount_lock);
if (!ret)
mnt->mnt_flags |= MNT_READONLY;
spin_unlock(&vfsmount_lock);
out:
unlock_mnt_writers();
return ret;
}
static void __mnt_unmake_readonly(struct vfsmount *mnt)
{
spin_lock(&vfsmount_lock);
mnt->mnt_flags &= ~MNT_READONLY;
spin_unlock(&vfsmount_lock);
}
int simple_set_mnt(struct vfsmount *mnt, struct super_block *sb)
{
mnt->mnt_sb = sb;
mnt->mnt_root = dget(sb->s_root);
return 0;
}
EXPORT_SYMBOL(simple_set_mnt);
void free_vfsmnt(struct vfsmount *mnt)
{
kfree(mnt->mnt_devname);
mnt_free_id(mnt);
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 vfsmount *mnt, struct dentry *dentry)
{
struct vfsmount *child_mnt;
spin_lock(&vfsmount_lock);
if ((child_mnt = __lookup_mnt(mnt, 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)
{
int cpu;
struct super_block *sb = mnt->mnt_sb;
/*
* We don't have to hold all of the locks at the
* same time here because we know that we're the
* last reference to mnt and that no new writers
* can come in.
*/
for_each_possible_cpu(cpu) {
struct mnt_writer *cpu_writer = &per_cpu(mnt_writers, cpu);
if (cpu_writer->mnt != mnt)
continue;
spin_lock(&cpu_writer->lock);
atomic_add(cpu_writer->count, &mnt->__mnt_writers);
cpu_writer->count = 0;
/*
* Might as well do this so that no one
* ever sees the pointer and expects
* it to be valid.
*/
cpu_writer->mnt = NULL;
spin_unlock(&cpu_writer->lock);
}
/*
* 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.
*/
WARN_ON(atomic_read(&mnt->__mnt_writers));
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 = mnt->mnt_sb->s_options;
if (options != NULL && options[0]) {
seq_putc(m, ',');
mangle(m, options);
}
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)
{
kfree(sb->s_options);
sb->s_options = kstrdup(options, GFP_KERNEL);
}
EXPORT_SYMBOL(save_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" },
{ 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;
spin_lock(&vfsmount_lock);
if (propagate_mount_busy(mnt, 2))
ret = 0;
spin_unlock(&vfsmount_lock);
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) {
lock_kernel();
sb->s_op->umount_begin(sb);
unlock_kernel();
}
/*
* 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)) {
lock_kernel();
retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
unlock_kernel();
}
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
*/
asmlinkage long sys_umount(char __user * name, int flags)
{
struct path path;
int retval;
retval = user_path(name, &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.
*/
asmlinkage long sys_oldumount(char __user * name)
{
return sys_umount(name, 0);
}
#endif
static int mount_is_safe(struct nameidata *nd)
{
if (capable(CAP_SYS_ADMIN))
return 0;
return -EPERM;
#ifdef notyet
if (S_ISLNK(nd->path.dentry->d_inode->i_mode))
return -EPERM;
if (nd->path.dentry->d_inode->i_mode & S_ISVTX) {
if (current->uid != nd->path.dentry->d_inode->i_uid)
return -EPERM;
}
if (vfs_permission(nd, 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 vfsmount *mnt, struct dentry *dentry)
{
struct vfsmount *tree;
down_write(&namespace_sem);
tree = copy_tree(mnt, 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;
if (IS_MNT_SHARED(dest_mnt)) {
for (p = source_mnt; p; p = next_mnt(p, source_mnt))
set_mnt_shared(p);
}
spin_lock(&vfsmount_lock);
if (parent_path) {
detach_mnt(source_mnt, parent_path);
attach_mnt(source_mnt, path);
touch_mnt_namespace(current->nsproxy->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 (IS_ROOT(path->dentry) || !d_unhashed(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.
* noinline this do_mount helper to save do_mount stack space.
*/
static noinline int do_change_type(struct nameidata *nd, int flag)
{
struct vfsmount *m, *mnt = nd->path.mnt;
int recurse = flag & MS_REC;
int type = flag & ~MS_REC;
int err = 0;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (nd->path.dentry != nd->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.
* noinline this do_mount helper to save do_mount stack space.
*/
static noinline int do_loopback(struct nameidata *nd, char *old_name,
int recurse)
{
struct nameidata old_nd;
struct vfsmount *mnt = NULL;
int err = mount_is_safe(nd);
if (err)
return err;
if (!old_name || !*old_name)
return -EINVAL;
err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
if (err)
return err;
down_write(&namespace_sem);
err = -EINVAL;
if (IS_MNT_UNBINDABLE(old_nd.path.mnt))
goto out;
if (!check_mnt(nd->path.mnt) || !check_mnt(old_nd.path.mnt))
goto out;
err = -ENOMEM;
if (recurse)
mnt = copy_tree(old_nd.path.mnt, old_nd.path.dentry, 0);
else
mnt = clone_mnt(old_nd.path.mnt, old_nd.path.dentry, 0);
if (!mnt)
goto out;
err = graft_tree(mnt, &nd->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_nd.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.
* noinline this do_mount helper to save do_mount stack space.
*/
static noinline int do_remount(struct nameidata *nd, int flags, int mnt_flags,
void *data)
{
int err;
struct super_block *sb = nd->path.mnt->mnt_sb;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (!check_mnt(nd->path.mnt))
return -EINVAL;
if (nd->path.dentry != nd->path.mnt->mnt_root)
return -EINVAL;
down_write(&sb->s_umount);
if (flags & MS_BIND)
err = change_mount_flags(nd->path.mnt, flags);
else
err = do_remount_sb(sb, flags, data, 0);
if (!err)
nd->path.mnt->mnt_flags = mnt_flags;
up_write(&sb->s_umount);
if (!err)
security_sb_post_remount(nd->path.mnt, flags, data);
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;
}
/*
* noinline this do_mount helper to save do_mount stack space.
*/
static noinline int do_move_mount(struct nameidata *nd, char *old_name)
{
struct nameidata old_nd;
struct path parent_path;
struct vfsmount *p;
int err = 0;
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (!old_name || !*old_name)
return -EINVAL;
err = path_lookup(old_name, LOOKUP_FOLLOW, &old_nd);
if (err)
return err;
down_write(&namespace_sem);
while (d_mountpoint(nd->path.dentry) &&
follow_down(&nd->path.mnt, &nd->path.dentry))
;
err = -EINVAL;
if (!check_mnt(nd->path.mnt) || !check_mnt(old_nd.path.mnt))
goto out;
err = -ENOENT;
mutex_lock(&nd->path.dentry->d_inode->i_mutex);
if (IS_DEADDIR(nd->path.dentry->d_inode))
goto out1;
if (!IS_ROOT(nd->path.dentry) && d_unhashed(nd->path.dentry))
goto out1;
err = -EINVAL;
if (old_nd.path.dentry != old_nd.path.mnt->mnt_root)
goto out1;
if (old_nd.path.mnt == old_nd.path.mnt->mnt_parent)
goto out1;
if (S_ISDIR(nd->path.dentry->d_inode->i_mode) !=
S_ISDIR(old_nd.path.dentry->d_inode->i_mode))
goto out1;
/*
* Don't move a mount residing in a shared parent.
*/
if (old_nd.path.mnt->mnt_parent &&
IS_MNT_SHARED(old_nd.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(nd->path.mnt) &&
tree_contains_unbindable(old_nd.path.mnt))
goto out1;
err = -ELOOP;
for (p = nd->path.mnt; p->mnt_parent != p; p = p->mnt_parent)
if (p == old_nd.path.mnt)
goto out1;
err = attach_recursive_mnt(old_nd.path.mnt, &nd->path, &parent_path);
if (err)
goto out1;
/* if the mount is moved, it should no longer be expire
* automatically */
list_del_init(&old_nd.path.mnt->mnt_expire);
out1:
mutex_unlock(&nd->path.dentry->d_inode->i_mutex);
out:
up_write(&namespace_sem);
if (!err)
path_put(&parent_path);
path_put(&old_nd.path);
return err;
}
/*
* create a new mount for userspace and request it to be added into the
* namespace's tree
* noinline this do_mount helper to save do_mount stack space.
*/
static noinline int do_new_mount(struct nameidata *nd, char *type, int flags,
int mnt_flags, char *name, void *data)
{
struct vfsmount *mnt;
if (!type || !memchr(type, 0, PAGE_SIZE))
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);
return do_add_mount(mnt, &nd->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;
down_write(&namespace_sem);
/* Something was mounted here while we slept */
while (d_mountpoint(path->dentry) &&
follow_down(&path->mnt, &path->dentry))
;
err = -EINVAL;
if (!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(mnt->mnt_ns);
umount_tree(mnt, 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;
}
/*
* 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 nameidata nd;
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 (dev_name && !memchr(dev_name, 0, PAGE_SIZE))
return -EINVAL;
if (data_page)
((char *)data_page)[PAGE_SIZE - 1] = 0;
/* 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_RELATIME)
mnt_flags |= MNT_RELATIME;
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);
/* ... and get the mountpoint */
retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
if (retval)
return retval;
retval = security_sb_mount(dev_name, &nd.path,
type_page, flags, data_page);
if (retval)
goto dput_out;
if (flags & MS_REMOUNT)
retval = do_remount(&nd, flags & ~MS_REMOUNT, mnt_flags,
data_page);
else if (flags & MS_BIND)
retval = do_loopback(&nd, dev_name, flags & MS_REC);
else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
retval = do_change_type(&nd, flags);
else if (flags & MS_MOVE)
retval = do_move_mount(&nd, dev_name);
else
retval = do_new_mount(&nd, type_page, flags, mnt_flags,
dev_name, data_page);
dput_out:
path_put(&nd.path);
return retval;
}
/*
* 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 = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
if (!new_ns)
return ERR_PTR(-ENOMEM);
atomic_set(&new_ns->count, 1);
INIT_LIST_HEAD(&new_ns->list);
init_waitqueue_head(&new_ns->poll);
new_ns->event = 0;
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;
}
asmlinkage long sys_mount(char __user * dev_name, char __user * dir_name,
char __user * type, unsigned long flags,
void __user * data)
{
int retval;
unsigned long data_page;
unsigned long type_page;
unsigned long dev_page;
char *dir_page;
retval = copy_mount_options(type, &type_page);
if (retval < 0)
return retval;
dir_page = getname(dir_name);
retval = PTR_ERR(dir_page);
if (IS_ERR(dir_page))
goto out1;
retval = copy_mount_options(dev_name, &dev_page);
if (retval < 0)
goto out2;
retval = copy_mount_options(data, &data_page);
if (retval < 0)
goto out3;
lock_kernel();
retval = do_mount((char *)dev_page, dir_page, (char *)type_page,
flags, (void *)data_page);
unlock_kernel();
free_page(data_page);
out3:
free_page(dev_page);
out2:
putname(dir_page);
out1:
free_page(type_page);
return retval;
}
/*
* Replace the fs->{rootmnt,root} with {mnt,dentry}. Put the old values.
* It can block. Requires the big lock held.
*/
void set_fs_root(struct fs_struct *fs, struct path *path)
{
struct path old_root;
write_lock(&fs->lock);
old_root = fs->root;
fs->root = *path;
path_get(path);
write_unlock(&fs->lock);
if (old_root.dentry)
path_put(&old_root);
}
/*
* Replace the fs->{pwdmnt,pwd} with {mnt,dentry}. Put the old values.
* It can block. Requires the big lock held.
*/
void set_fs_pwd(struct fs_struct *fs, struct path *path)
{
struct path old_pwd;
write_lock(&fs->lock);
old_pwd = fs->pwd;
fs->pwd = *path;
path_get(path);
write_unlock(&fs->lock);
if (old_pwd.dentry)
path_put(&old_pwd);
}
static void chroot_fs_refs(struct path *old_root, struct path *new_root)
{
struct task_struct *g, *p;
struct fs_struct *fs;
read_lock(&tasklist_lock);
do_each_thread(g, p) {
task_lock(p);
fs = p->fs;
if (fs) {
atomic_inc(&fs->count);
task_unlock(p);
if (fs->root.dentry == old_root->dentry
&& fs->root.mnt == old_root->mnt)
set_fs_root(fs, new_root);
if (fs->pwd.dentry == old_root->dentry
&& fs->pwd.mnt == old_root->mnt)
set_fs_pwd(fs, new_root);
put_fs_struct(fs);
} else
task_unlock(p);
} while_each_thread(g, p);
read_unlock(&tasklist_lock);
}
/*
* 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.
*/
asmlinkage long sys_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_unhashed(new.dentry) && !IS_ROOT(new.dentry))
goto out2;
if (d_unhashed(old.dentry) && !IS_ROOT(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 = kmalloc(sizeof(*ns), GFP_KERNEL);
if (!ns)
panic("Can't allocate initial namespace");
atomic_set(&ns->count, 1);
INIT_LIST_HEAD(&ns->list);
init_waitqueue_head(&ns->poll);
ns->event = 0;
list_add(&mnt->mnt_list, &ns->list);
ns->root = mnt;
mnt->mnt_ns = ns;
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 = ns->root;
LIST_HEAD(umount_list);
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);
}