namespace.c 44.0 KB
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/*
 *  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/config.h>
#include <linux/syscalls.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/quotaops.h>
#include <linux/acct.h>
#include <linux/module.h>
#include <linux/seq_file.h>
#include <linux/namespace.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
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#include "pnode.h"
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extern int __init init_rootfs(void);

#ifdef CONFIG_SYSFS
extern int __init sysfs_init(void);
#else
static inline int sysfs_init(void)
{
	return 0;
}
#endif

/* spinlock for vfsmount related operations, inplace of dcache_lock */
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__cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock);

static int event;
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static struct list_head *mount_hashtable;
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static int hash_mask __read_mostly, hash_bits __read_mostly;
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static kmem_cache_t *mnt_cache;
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static struct rw_semaphore namespace_sem;
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static inline unsigned long hash(struct vfsmount *mnt, struct dentry *dentry)
{
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	unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES);
	tmp += ((unsigned long)dentry / L1_CACHE_BYTES);
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	tmp = tmp + (tmp >> hash_bits);
	return tmp & hash_mask;
}

struct vfsmount *alloc_vfsmnt(const char *name)
{
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	struct vfsmount *mnt = kmem_cache_alloc(mnt_cache, GFP_KERNEL);
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	if (mnt) {
		memset(mnt, 0, sizeof(struct vfsmount));
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		atomic_set(&mnt->mnt_count, 1);
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		INIT_LIST_HEAD(&mnt->mnt_hash);
		INIT_LIST_HEAD(&mnt->mnt_child);
		INIT_LIST_HEAD(&mnt->mnt_mounts);
		INIT_LIST_HEAD(&mnt->mnt_list);
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		INIT_LIST_HEAD(&mnt->mnt_expire);
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		INIT_LIST_HEAD(&mnt->mnt_share);
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		INIT_LIST_HEAD(&mnt->mnt_slave_list);
		INIT_LIST_HEAD(&mnt->mnt_slave);
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		if (name) {
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			int size = strlen(name) + 1;
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			char *newname = kmalloc(size, GFP_KERNEL);
			if (newname) {
				memcpy(newname, name, size);
				mnt->mnt_devname = newname;
			}
		}
	}
	return mnt;
}

void free_vfsmnt(struct vfsmount *mnt)
{
	kfree(mnt->mnt_devname);
	kmem_cache_free(mnt_cache, mnt);
}

/*
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 * 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.
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 */
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struct vfsmount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry,
			      int dir)
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{
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	struct list_head *head = mount_hashtable + hash(mnt, dentry);
	struct list_head *tmp = head;
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	struct vfsmount *p, *found = NULL;

	for (;;) {
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		tmp = dir ? tmp->next : tmp->prev;
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		p = NULL;
		if (tmp == head)
			break;
		p = list_entry(tmp, struct vfsmount, mnt_hash);
		if (p->mnt_parent == mnt && p->mnt_mountpoint == dentry) {
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			found = p;
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			break;
		}
	}
	return found;
}

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/*
 * 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;
}

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static inline int check_mnt(struct vfsmount *mnt)
{
	return mnt->mnt_namespace == current->namespace;
}

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static void touch_namespace(struct namespace *ns)
{
	if (ns) {
		ns->event = ++event;
		wake_up_interruptible(&ns->poll);
	}
}

static void __touch_namespace(struct namespace *ns)
{
	if (ns && ns->event != event) {
		ns->event = event;
		wake_up_interruptible(&ns->poll);
	}
}

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static void detach_mnt(struct vfsmount *mnt, struct nameidata *old_nd)
{
	old_nd->dentry = mnt->mnt_mountpoint;
	old_nd->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_nd->dentry->d_mounted--;
}

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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++;
}

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static void attach_mnt(struct vfsmount *mnt, struct nameidata *nd)
{
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	mnt_set_mountpoint(nd->mnt, nd->dentry, mnt);
	list_add_tail(&mnt->mnt_hash, mount_hashtable +
			hash(nd->mnt, nd->dentry));
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	list_add_tail(&mnt->mnt_child, &nd->mnt->mnt_mounts);
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}

/*
 * 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 namespace *n = parent->mnt_namespace;

	BUG_ON(parent == mnt);

	list_add_tail(&head, &mnt->mnt_list);
	list_for_each_entry(m, &head, mnt_list)
		m->mnt_namespace = 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_namespace(n);
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}

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);
}

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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;
}

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static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
					int flag)
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{
	struct super_block *sb = old->mnt_sb;
	struct vfsmount *mnt = alloc_vfsmnt(old->mnt_devname);

	if (mnt) {
		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;
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		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_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;
		}
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		if (flag & CL_MAKE_SHARED)
			set_mnt_shared(mnt);
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		/* stick the duplicate mount on the same expiry list
		 * as the original if that was on one */
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		if (flag & CL_EXPIRE) {
			spin_lock(&vfsmount_lock);
			if (!list_empty(&old->mnt_expire))
				list_add(&mnt->mnt_expire, &old->mnt_expire);
			spin_unlock(&vfsmount_lock);
		}
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	}
	return mnt;
}

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static inline void __mntput(struct vfsmount *mnt)
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{
	struct super_block *sb = mnt->mnt_sb;
	dput(mnt->mnt_root);
	free_vfsmnt(mnt);
	deactivate_super(sb);
}

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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);
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/* iterator */
static void *m_start(struct seq_file *m, loff_t *pos)
{
	struct namespace *n = m->private;
	struct list_head *p;
	loff_t l = *pos;

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	down_read(&namespace_sem);
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	list_for_each(p, &n->list)
		if (!l--)
			return list_entry(p, struct vfsmount, mnt_list);
	return NULL;
}

static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
	struct namespace *n = m->private;
	struct list_head *p = ((struct vfsmount *)v)->mnt_list.next;
	(*pos)++;
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	return p == &n->list ? NULL : list_entry(p, struct vfsmount, mnt_list);
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}

static void m_stop(struct seq_file *m, void *v)
{
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	up_read(&namespace_sem);
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}

static inline void mangle(struct seq_file *m, const char *s)
{
	seq_escape(m, s, " \t\n\\");
}

static int show_vfsmnt(struct seq_file *m, void *v)
{
	struct vfsmount *mnt = v;
	int err = 0;
	static struct proc_fs_info {
		int flag;
		char *str;
	} fs_info[] = {
		{ MS_SYNCHRONOUS, ",sync" },
		{ MS_DIRSYNC, ",dirsync" },
		{ MS_MANDLOCK, ",mand" },
		{ 0, NULL }
	};
	static struct proc_fs_info mnt_info[] = {
		{ MNT_NOSUID, ",nosuid" },
		{ MNT_NODEV, ",nodev" },
		{ MNT_NOEXEC, ",noexec" },
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		{ MNT_NOATIME, ",noatime" },
		{ MNT_NODIRATIME, ",nodiratime" },
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		{ 0, NULL }
	};
	struct proc_fs_info *fs_infop;

	mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
	seq_putc(m, ' ');
	seq_path(m, mnt, mnt->mnt_root, " \t\n\\");
	seq_putc(m, ' ');
	mangle(m, mnt->mnt_sb->s_type->name);
	seq_puts(m, mnt->mnt_sb->s_flags & MS_RDONLY ? " ro" : " rw");
	for (fs_infop = fs_info; fs_infop->flag; fs_infop++) {
		if (mnt->mnt_sb->s_flags & fs_infop->flag)
			seq_puts(m, fs_infop->str);
	}
	for (fs_infop = mnt_info; fs_infop->flag; fs_infop++) {
		if (mnt->mnt_flags & fs_infop->flag)
			seq_puts(m, fs_infop->str);
	}
	if (mnt->mnt_sb->s_op->show_options)
		err = mnt->mnt_sb->s_op->show_options(m, mnt);
	seq_puts(m, " 0 0\n");
	return err;
}

struct seq_operations mounts_op = {
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_vfsmnt
};

/**
 * 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)
{
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	int actual_refs = 0;
	int minimum_refs = 0;
	struct vfsmount *p;
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	spin_lock(&vfsmount_lock);
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	for (p = mnt; p; p = next_mnt(p, mnt)) {
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		actual_refs += atomic_read(&p->mnt_count);
		minimum_refs += 2;
	}
	spin_unlock(&vfsmount_lock);

	if (actual_refs > minimum_refs)
		return -EBUSY;

	return 0;
}

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)
{
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	int ret = 0;
	spin_lock(&vfsmount_lock);
	if (propagate_mount_busy(mnt, 2))
		ret = -EBUSY;
	spin_unlock(&vfsmount_lock);
	return ret;
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}

EXPORT_SYMBOL(may_umount);

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void release_mounts(struct list_head *head)
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{
	struct vfsmount *mnt;
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	while (!list_empty(head)) {
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		mnt = list_entry(head->next, 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;
			spin_unlock(&vfsmount_lock);
			dput(dentry);
			mntput(m);
		}
		mntput(mnt);
	}
}

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void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
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{
	struct vfsmount *p;

	for (p = mnt; p; p = next_mnt(p, mnt)) {
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		list_del(&p->mnt_hash);
		list_add(&p->mnt_hash, kill);
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	}

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	if (propagate)
		propagate_umount(kill);

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	list_for_each_entry(p, kill, mnt_hash) {
		list_del_init(&p->mnt_expire);
		list_del_init(&p->mnt_list);
		__touch_namespace(p->mnt_namespace);
		p->mnt_namespace = NULL;
		list_del_init(&p->mnt_child);
		if (p->mnt_parent != p)
			mnt->mnt_mountpoint->d_mounted--;
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		change_mnt_propagation(p, MS_PRIVATE);
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	}
}

static int do_umount(struct vfsmount *mnt, int flags)
{
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	struct super_block *sb = mnt->mnt_sb;
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	int retval;
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	LIST_HEAD(umount_list);
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	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->rootmnt ||
		    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.
	 */

	lock_kernel();
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	if ((flags & MNT_FORCE) && sb->s_op->umount_begin)
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		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->rootmnt && !(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();
			DQUOT_OFF(sb);
			retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
			unlock_kernel();
		}
		up_write(&sb->s_umount);
		return retval;
	}

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	down_write(&namespace_sem);
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	spin_lock(&vfsmount_lock);
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	event++;
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	retval = -EBUSY;
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	if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
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		if (!list_empty(&mnt->mnt_list))
R
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			umount_tree(mnt, 1, &umount_list);
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		retval = 0;
	}
	spin_unlock(&vfsmount_lock);
	if (retval)
		security_sb_umount_busy(mnt);
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	up_write(&namespace_sem);
R
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	release_mounts(&umount_list);
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	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 nameidata nd;
	int retval;

	retval = __user_walk(name, LOOKUP_FOLLOW, &nd);
	if (retval)
		goto out;
	retval = -EINVAL;
	if (nd.dentry != nd.mnt->mnt_root)
		goto dput_and_out;
	if (!check_mnt(nd.mnt))
		goto dput_and_out;

	retval = -EPERM;
	if (!capable(CAP_SYS_ADMIN))
		goto dput_and_out;

	retval = do_umount(nd.mnt, flags);
dput_and_out:
	path_release_on_umount(&nd);
out:
	return retval;
}

#ifdef __ARCH_WANT_SYS_OLDUMOUNT

/*
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 *	The 2.0 compatible umount. No flags.
L
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 */
asmlinkage long sys_oldumount(char __user * name)
{
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	return sys_umount(name, 0);
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}

#endif

static int mount_is_safe(struct nameidata *nd)
{
	if (capable(CAP_SYS_ADMIN))
		return 0;
	return -EPERM;
#ifdef notyet
	if (S_ISLNK(nd->dentry->d_inode->i_mode))
		return -EPERM;
	if (nd->dentry->d_inode->i_mode & S_ISVTX) {
		if (current->uid != nd->dentry->d_inode->i_uid)
			return -EPERM;
	}
640
	if (vfs_permission(nd, MAY_WRITE))
L
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		return -EPERM;
	return 0;
#endif
}

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static int lives_below_in_same_fs(struct dentry *d, struct dentry *dentry)
L
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{
	while (1) {
		if (d == dentry)
			return 1;
		if (d == NULL || d == d->d_parent)
			return 0;
		d = d->d_parent;
	}
}

657
struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
R
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					int flag)
L
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659 660 661 662
{
	struct vfsmount *res, *p, *q, *r, *s;
	struct nameidata nd;

R
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	if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
		return NULL;

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	res = q = clone_mnt(mnt, dentry, flag);
L
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667 668 669 670 671
	if (!q)
		goto Enomem;
	q->mnt_mountpoint = mnt->mnt_mountpoint;

	p = mnt;
672
	list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
L
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		if (!lives_below_in_same_fs(r->mnt_mountpoint, dentry))
			continue;

		for (s = r; s; s = next_mnt(s, r)) {
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			if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
				s = skip_mnt_tree(s);
				continue;
			}
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			while (p != s->mnt_parent) {
				p = p->mnt_parent;
				q = q->mnt_parent;
			}
			p = s;
			nd.mnt = q;
			nd.dentry = p->mnt_mountpoint;
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			q = clone_mnt(p, p->mnt_root, flag);
L
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			if (!q)
				goto Enomem;
			spin_lock(&vfsmount_lock);
			list_add_tail(&q->mnt_list, &res->mnt_list);
			attach_mnt(q, &nd);
			spin_unlock(&vfsmount_lock);
		}
	}
	return res;
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Enomem:
L
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	if (res) {
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		LIST_HEAD(umount_list);
L
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		spin_lock(&vfsmount_lock);
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		umount_tree(res, 0, &umount_list);
L
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		spin_unlock(&vfsmount_lock);
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		release_mounts(&umount_list);
L
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705 706 707 708
	}
	return NULL;
}

709 710
/*
 *  @source_mnt : mount tree to be attached
R
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 *  @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)
715 716 717
 *
 *  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.
R
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 * ---------------------------------------------------------------------------
 * |         BIND MOUNT OPERATION                                            |
 * |**************************************************************************
 * | source-->| shared        |       private  |       slave    | unbindable |
 * | dest     |               |                |                |            |
 * |   |      |               |                |                |            |
 * |   v      |               |                |                |            |
 * |**************************************************************************
 * |  shared  | shared (++)   |     shared (+) |     shared(+++)|  invalid   |
 * |          |               |                |                |            |
 * |non-shared| shared (+)    |      private   |      slave (*) |  invalid   |
 * ***************************************************************************
730 731 732 733 734 735 736 737 738
 * 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.
R
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 * (+++) 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.
 *
R
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746 747 748 749 750 751 752 753 754 755 756 757
 * ---------------------------------------------------------------------------
 * |         		MOVE MOUNT OPERATION                                 |
 * |**************************************************************************
 * | source-->| shared        |       private  |       slave    | unbindable |
 * | dest     |               |                |                |            |
 * |   |      |               |                |                |            |
 * |   v      |               |                |                |            |
 * |**************************************************************************
 * |  shared  | shared (+)    |     shared (+) |    shared(+++) |  invalid   |
 * |          |               |                |                |            |
 * |non-shared| shared (+*)   |      private   |    slave (*)   | unbindable |
 * ***************************************************************************
R
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758 759 760
 *
 * (+)  the mount is moved to the destination. And is then propagated to
 * 	all the mounts in the propagation tree of the destination mount.
R
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761
 * (+*)  the mount is moved to the destination.
R
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 * (+++)  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.
766 767 768 769 770 771 772
 *
 * 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,
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			struct nameidata *nd, struct nameidata *parent_nd)
774 775 776 777 778 779 780 781 782 783 784 785 786 787 788
{
	LIST_HEAD(tree_list);
	struct vfsmount *dest_mnt = nd->mnt;
	struct dentry *dest_dentry = nd->dentry;
	struct vfsmount *child, *p;

	if (propagate_mnt(dest_mnt, dest_dentry, source_mnt, &tree_list))
		return -EINVAL;

	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);
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789 790 791 792 793 794 795 796
	if (parent_nd) {
		detach_mnt(source_mnt, parent_nd);
		attach_mnt(source_mnt, nd);
		touch_namespace(current->namespace);
	} else {
		mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
		commit_tree(source_mnt);
	}
797 798 799 800 801 802 803 804 805

	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;
}

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static int graft_tree(struct vfsmount *mnt, struct nameidata *nd)
{
	int err;
	if (mnt->mnt_sb->s_flags & MS_NOUSER)
		return -EINVAL;

	if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
	      S_ISDIR(mnt->mnt_root->d_inode->i_mode))
		return -ENOTDIR;

	err = -ENOENT;
817
	mutex_lock(&nd->dentry->d_inode->i_mutex);
L
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	if (IS_DEADDIR(nd->dentry->d_inode))
		goto out_unlock;

	err = security_sb_check_sb(mnt, nd);
	if (err)
		goto out_unlock;

	err = -ENOENT;
826
	if (IS_ROOT(nd->dentry) || !d_unhashed(nd->dentry))
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		err = attach_recursive_mnt(mnt, nd, NULL);
L
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out_unlock:
829
	mutex_unlock(&nd->dentry->d_inode->i_mutex);
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	if (!err)
		security_sb_post_addmount(mnt, nd);
	return err;
}

835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855
/*
 * recursively change the type of the mountpoint.
 */
static int do_change_type(struct nameidata *nd, int flag)
{
	struct vfsmount *m, *mnt = nd->mnt;
	int recurse = flag & MS_REC;
	int type = flag & ~MS_REC;

	if (nd->dentry != nd->mnt->mnt_root)
		return -EINVAL;

	down_write(&namespace_sem);
	spin_lock(&vfsmount_lock);
	for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
		change_mnt_propagation(m, type);
	spin_unlock(&vfsmount_lock);
	up_write(&namespace_sem);
	return 0;
}

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856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871
/*
 * do loopback mount.
 */
static 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;

R
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	down_write(&namespace_sem);
L
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873
	err = -EINVAL;
R
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	if (IS_MNT_UNBINDABLE(old_nd.mnt))
 		goto out;

877 878
	if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
		goto out;
L
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879

880 881
	err = -ENOMEM;
	if (recurse)
R
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		mnt = copy_tree(old_nd.mnt, old_nd.dentry, 0);
883
	else
R
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884
		mnt = clone_mnt(old_nd.mnt, old_nd.dentry, 0);
885 886 887 888 889 890

	if (!mnt)
		goto out;

	err = graft_tree(mnt, nd);
	if (err) {
R
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891
		LIST_HEAD(umount_list);
L
Linus Torvalds 已提交
892
		spin_lock(&vfsmount_lock);
R
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893
		umount_tree(mnt, 0, &umount_list);
L
Linus Torvalds 已提交
894
		spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
895
		release_mounts(&umount_list);
896
	}
L
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897

898
out:
R
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899
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
900 901 902 903 904 905 906 907 908 909 910 911 912
	path_release(&old_nd);
	return err;
}

/*
 * 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 nameidata *nd, int flags, int mnt_flags,
		      void *data)
{
	int err;
R
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913
	struct super_block *sb = nd->mnt->mnt_sb;
L
Linus Torvalds 已提交
914 915 916 917 918 919 920 921 922 923 924 925 926

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	if (!check_mnt(nd->mnt))
		return -EINVAL;

	if (nd->dentry != nd->mnt->mnt_root)
		return -EINVAL;

	down_write(&sb->s_umount);
	err = do_remount_sb(sb, flags, data, 0);
	if (!err)
R
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927
		nd->mnt->mnt_flags = mnt_flags;
L
Linus Torvalds 已提交
928 929 930 931 932 933
	up_write(&sb->s_umount);
	if (!err)
		security_sb_post_remount(nd->mnt, flags, data);
	return err;
}

R
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934 935 936 937 938 939 940 941 942 943
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;
}

L
Linus Torvalds 已提交
944 945 946 947 948 949 950 951 952 953 954 955 956
static int do_move_mount(struct nameidata *nd, char *old_name)
{
	struct nameidata old_nd, parent_nd;
	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;

R
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	down_write(&namespace_sem);
R
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958
	while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
L
Linus Torvalds 已提交
959 960 961 962 963 964
		;
	err = -EINVAL;
	if (!check_mnt(nd->mnt) || !check_mnt(old_nd.mnt))
		goto out;

	err = -ENOENT;
965
	mutex_lock(&nd->dentry->d_inode->i_mutex);
L
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966 967 968 969
	if (IS_DEADDIR(nd->dentry->d_inode))
		goto out1;

	if (!IS_ROOT(nd->dentry) && d_unhashed(nd->dentry))
R
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970
		goto out1;
L
Linus Torvalds 已提交
971 972 973

	err = -EINVAL;
	if (old_nd.dentry != old_nd.mnt->mnt_root)
R
Ram Pai 已提交
974
		goto out1;
L
Linus Torvalds 已提交
975 976

	if (old_nd.mnt == old_nd.mnt->mnt_parent)
R
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977
		goto out1;
L
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978 979 980

	if (S_ISDIR(nd->dentry->d_inode->i_mode) !=
	      S_ISDIR(old_nd.dentry->d_inode->i_mode))
R
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981 982 983 984 985 986
		goto out1;
	/*
	 * Don't move a mount residing in a shared parent.
	 */
	if (old_nd.mnt->mnt_parent && IS_MNT_SHARED(old_nd.mnt->mnt_parent))
		goto out1;
R
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987 988 989 990 991 992
	/*
	 * Don't move a mount tree containing unbindable mounts to a destination
	 * mount which is shared.
	 */
	if (IS_MNT_SHARED(nd->mnt) && tree_contains_unbindable(old_nd.mnt))
		goto out1;
L
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993
	err = -ELOOP;
R
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994
	for (p = nd->mnt; p->mnt_parent != p; p = p->mnt_parent)
L
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995
		if (p == old_nd.mnt)
R
Ram Pai 已提交
996
			goto out1;
L
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997

R
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998 999
	if ((err = attach_recursive_mnt(old_nd.mnt, nd, &parent_nd)))
		goto out1;
L
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1000

R
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1001
	spin_lock(&vfsmount_lock);
L
Linus Torvalds 已提交
1002 1003
	/* if the mount is moved, it should no longer be expire
	 * automatically */
1004
	list_del_init(&old_nd.mnt->mnt_expire);
L
Linus Torvalds 已提交
1005 1006
	spin_unlock(&vfsmount_lock);
out1:
1007
	mutex_unlock(&nd->dentry->d_inode->i_mutex);
L
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1008
out:
R
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1009
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047
	if (!err)
		path_release(&parent_nd);
	path_release(&old_nd);
	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 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, 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 nameidata *nd,
		 int mnt_flags, struct list_head *fslist)
{
	int err;

R
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1048
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
1049
	/* Something was mounted here while we slept */
R
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1050
	while (d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
L
Linus Torvalds 已提交
1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066
		;
	err = -EINVAL;
	if (!check_mnt(nd->mnt))
		goto unlock;

	/* Refuse the same filesystem on the same mount point */
	err = -EBUSY;
	if (nd->mnt->mnt_sb == newmnt->mnt_sb &&
	    nd->mnt->mnt_root == nd->dentry)
		goto unlock;

	err = -EINVAL;
	if (S_ISLNK(newmnt->mnt_root->d_inode->i_mode))
		goto unlock;

	newmnt->mnt_flags = mnt_flags;
1067 1068
	if ((err = graft_tree(newmnt, nd)))
		goto unlock;
L
Linus Torvalds 已提交
1069

1070
	if (fslist) {
L
Linus Torvalds 已提交
1071 1072
		/* add to the specified expiration list */
		spin_lock(&vfsmount_lock);
1073
		list_add_tail(&newmnt->mnt_expire, fslist);
L
Linus Torvalds 已提交
1074 1075
		spin_unlock(&vfsmount_lock);
	}
R
Ram Pai 已提交
1076
	up_write(&namespace_sem);
1077
	return 0;
L
Linus Torvalds 已提交
1078 1079

unlock:
R
Ram Pai 已提交
1080
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1081 1082 1083 1084 1085 1086
	mntput(newmnt);
	return err;
}

EXPORT_SYMBOL_GPL(do_add_mount);

R
Ram Pai 已提交
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static void expire_mount(struct vfsmount *mnt, struct list_head *mounts,
				struct list_head *umounts)
1089 1090 1091
{
	spin_lock(&vfsmount_lock);

1092 1093 1094 1095 1096 1097 1098 1099 1100
	/*
	 * Check if mount is still attached, if not, let whoever holds it deal
	 * with the sucker
	 */
	if (mnt->mnt_parent == mnt) {
		spin_unlock(&vfsmount_lock);
		return;
	}

1101 1102 1103 1104
	/*
	 * Check that it is still dead: the count should now be 2 - as
	 * contributed by the vfsmount parent and the mntget above
	 */
R
Ram Pai 已提交
1105
	if (!propagate_mount_busy(mnt, 2)) {
1106
		/* delete from the namespace */
A
Al Viro 已提交
1107
		touch_namespace(mnt->mnt_namespace);
1108
		list_del_init(&mnt->mnt_list);
1109
		mnt->mnt_namespace = NULL;
R
Ram Pai 已提交
1110
		umount_tree(mnt, 1, umounts);
1111 1112 1113 1114 1115 1116
		spin_unlock(&vfsmount_lock);
	} else {
		/*
		 * Someone brought it back to life whilst we didn't have any
		 * locks held so return it to the expiration list
		 */
1117
		list_add_tail(&mnt->mnt_expire, mounts);
1118 1119 1120 1121
		spin_unlock(&vfsmount_lock);
	}
}

L
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1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143
/*
 * 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 namespace *namespace;
	struct vfsmount *mnt, *next;
	LIST_HEAD(graveyard);

	if (list_empty(mounts))
		return;

	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())
	 */
1144
	list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
L
Linus Torvalds 已提交
1145 1146 1147 1148 1149
		if (!xchg(&mnt->mnt_expiry_mark, 1) ||
		    atomic_read(&mnt->mnt_count) != 1)
			continue;

		mntget(mnt);
1150
		list_move(&mnt->mnt_expire, &graveyard);
L
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1151 1152 1153 1154 1155 1156 1157 1158 1159
	}

	/*
	 * go through the vfsmounts we've just consigned to the graveyard to
	 * - check that they're still dead
	 * - delete the vfsmount from the appropriate namespace under lock
	 * - dispose of the corpse
	 */
	while (!list_empty(&graveyard)) {
R
Ram Pai 已提交
1160
		LIST_HEAD(umounts);
1161 1162
		mnt = list_entry(graveyard.next, struct vfsmount, mnt_expire);
		list_del_init(&mnt->mnt_expire);
L
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1163 1164 1165 1166

		/* don't do anything if the namespace is dead - all the
		 * vfsmounts from it are going away anyway */
		namespace = mnt->mnt_namespace;
1167
		if (!namespace || !namespace->root)
L
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1168 1169 1170 1171
			continue;
		get_namespace(namespace);

		spin_unlock(&vfsmount_lock);
R
Ram Pai 已提交
1172
		down_write(&namespace_sem);
R
Ram Pai 已提交
1173
		expire_mount(mnt, mounts, &umounts);
R
Ram Pai 已提交
1174
		up_write(&namespace_sem);
R
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1175
		release_mounts(&umounts);
L
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1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191
		mntput(mnt);
		put_namespace(namespace);
		spin_lock(&vfsmount_lock);
	}

	spin_unlock(&vfsmount_lock);
}

EXPORT_SYMBOL_GPL(mark_mounts_for_expiry);

/*
 * 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.
 */
R
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1192 1193
static long exact_copy_from_user(void *to, const void __user * from,
				 unsigned long n)
L
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1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213
{
	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;
}

R
Ram Pai 已提交
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int copy_mount_options(const void __user * data, unsigned long *where)
L
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1215 1216 1217 1218
{
	int i;
	unsigned long page;
	unsigned long size;
R
Ram Pai 已提交
1219

L
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1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237
	*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) {
R
Ram Pai 已提交
1238
		free_page(page);
L
Linus Torvalds 已提交
1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260
		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.
 */
R
Ram Pai 已提交
1261
long do_mount(char *dev_name, char *dir_name, char *type_page,
L
Linus Torvalds 已提交
1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288
		  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;
1289 1290 1291 1292 1293 1294 1295
	if (flags & MS_NOATIME)
		mnt_flags |= MNT_NOATIME;
	if (flags & MS_NODIRATIME)
		mnt_flags |= MNT_NODIRATIME;

	flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE |
		   MS_NOATIME | MS_NODIRATIME);
L
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1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310

	/* ... and get the mountpoint */
	retval = path_lookup(dir_name, LOOKUP_FOLLOW, &nd);
	if (retval)
		return retval;

	retval = security_sb_mount(dev_name, &nd, 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);
R
Ram Pai 已提交
1311
	else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
1312
		retval = do_change_type(&nd, flags);
L
Linus Torvalds 已提交
1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349
	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_release(&nd);
	return retval;
}

int copy_namespace(int flags, struct task_struct *tsk)
{
	struct namespace *namespace = tsk->namespace;
	struct namespace *new_ns;
	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL, *altrootmnt = NULL;
	struct fs_struct *fs = tsk->fs;
	struct vfsmount *p, *q;

	if (!namespace)
		return 0;

	get_namespace(namespace);

	if (!(flags & CLONE_NEWNS))
		return 0;

	if (!capable(CAP_SYS_ADMIN)) {
		put_namespace(namespace);
		return -EPERM;
	}

	new_ns = kmalloc(sizeof(struct namespace), GFP_KERNEL);
	if (!new_ns)
		goto out;

	atomic_set(&new_ns->count, 1);
	INIT_LIST_HEAD(&new_ns->list);
A
Al Viro 已提交
1350 1351
	init_waitqueue_head(&new_ns->poll);
	new_ns->event = 0;
L
Linus Torvalds 已提交
1352

R
Ram Pai 已提交
1353
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
1354
	/* First pass: copy the tree topology */
R
Ram Pai 已提交
1355
	new_ns->root = copy_tree(namespace->root, namespace->root->mnt_root,
R
Ram Pai 已提交
1356
					CL_COPY_ALL | CL_EXPIRE);
L
Linus Torvalds 已提交
1357
	if (!new_ns->root) {
R
Ram Pai 已提交
1358
		up_write(&namespace_sem);
L
Linus Torvalds 已提交
1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391
		kfree(new_ns);
		goto out;
	}
	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 = namespace->root;
	q = new_ns->root;
	while (p) {
		q->mnt_namespace = new_ns;
		if (fs) {
			if (p == fs->rootmnt) {
				rootmnt = p;
				fs->rootmnt = mntget(q);
			}
			if (p == fs->pwdmnt) {
				pwdmnt = p;
				fs->pwdmnt = mntget(q);
			}
			if (p == fs->altrootmnt) {
				altrootmnt = p;
				fs->altrootmnt = mntget(q);
			}
		}
		p = next_mnt(p, namespace->root);
		q = next_mnt(q, new_ns->root);
	}
R
Ram Pai 已提交
1392
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420

	tsk->namespace = new_ns;

	if (rootmnt)
		mntput(rootmnt);
	if (pwdmnt)
		mntput(pwdmnt);
	if (altrootmnt)
		mntput(altrootmnt);

	put_namespace(namespace);
	return 0;

out:
	put_namespace(namespace);
	return -ENOMEM;
}

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;

R
Ram Pai 已提交
1421
	retval = copy_mount_options(type, &type_page);
L
Linus Torvalds 已提交
1422 1423 1424 1425 1426 1427 1428 1429
	if (retval < 0)
		return retval;

	dir_page = getname(dir_name);
	retval = PTR_ERR(dir_page);
	if (IS_ERR(dir_page))
		goto out1;

R
Ram Pai 已提交
1430
	retval = copy_mount_options(dev_name, &dev_page);
L
Linus Torvalds 已提交
1431 1432 1433
	if (retval < 0)
		goto out2;

R
Ram Pai 已提交
1434
	retval = copy_mount_options(data, &data_page);
L
Linus Torvalds 已提交
1435 1436 1437 1438
	if (retval < 0)
		goto out3;

	lock_kernel();
R
Ram Pai 已提交
1439 1440
	retval = do_mount((char *)dev_page, dir_page, (char *)type_page,
			  flags, (void *)data_page);
L
Linus Torvalds 已提交
1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508
	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 vfsmount *mnt,
		 struct dentry *dentry)
{
	struct dentry *old_root;
	struct vfsmount *old_rootmnt;
	write_lock(&fs->lock);
	old_root = fs->root;
	old_rootmnt = fs->rootmnt;
	fs->rootmnt = mntget(mnt);
	fs->root = dget(dentry);
	write_unlock(&fs->lock);
	if (old_root) {
		dput(old_root);
		mntput(old_rootmnt);
	}
}

/*
 * 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 vfsmount *mnt,
		struct dentry *dentry)
{
	struct dentry *old_pwd;
	struct vfsmount *old_pwdmnt;

	write_lock(&fs->lock);
	old_pwd = fs->pwd;
	old_pwdmnt = fs->pwdmnt;
	fs->pwdmnt = mntget(mnt);
	fs->pwd = dget(dentry);
	write_unlock(&fs->lock);

	if (old_pwd) {
		dput(old_pwd);
		mntput(old_pwdmnt);
	}
}

static void chroot_fs_refs(struct nameidata *old_nd, struct nameidata *new_nd)
{
	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);
R
Ram Pai 已提交
1509 1510
			if (fs->root == old_nd->dentry
			    && fs->rootmnt == old_nd->mnt)
L
Linus Torvalds 已提交
1511
				set_fs_root(fs, new_nd->mnt, new_nd->dentry);
R
Ram Pai 已提交
1512 1513
			if (fs->pwd == old_nd->dentry
			    && fs->pwdmnt == old_nd->mnt)
L
Linus Torvalds 已提交
1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534
				set_fs_pwd(fs, new_nd->mnt, new_nd->dentry);
			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.
 *
N
Neil Brown 已提交
1535 1536 1537 1538
 * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem.
 * See Documentation/filesystems/ramfs-rootfs-initramfs.txt for alternatives
 * in this situation.
 *
L
Linus Torvalds 已提交
1539 1540 1541 1542 1543 1544 1545 1546
 * 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.
 */
R
Ram Pai 已提交
1547 1548
asmlinkage long sys_pivot_root(const char __user * new_root,
			       const char __user * put_old)
L
Linus Torvalds 已提交
1549 1550 1551 1552 1553 1554 1555 1556 1557 1558
{
	struct vfsmount *tmp;
	struct nameidata new_nd, old_nd, parent_nd, root_parent, user_nd;
	int error;

	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

	lock_kernel();

R
Ram Pai 已提交
1559 1560
	error = __user_walk(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY,
			    &new_nd);
L
Linus Torvalds 已提交
1561 1562 1563 1564 1565 1566
	if (error)
		goto out0;
	error = -EINVAL;
	if (!check_mnt(new_nd.mnt))
		goto out1;

R
Ram Pai 已提交
1567
	error = __user_walk(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_nd);
L
Linus Torvalds 已提交
1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580
	if (error)
		goto out1;

	error = security_sb_pivotroot(&old_nd, &new_nd);
	if (error) {
		path_release(&old_nd);
		goto out1;
	}

	read_lock(&current->fs->lock);
	user_nd.mnt = mntget(current->fs->rootmnt);
	user_nd.dentry = dget(current->fs->root);
	read_unlock(&current->fs->lock);
R
Ram Pai 已提交
1581
	down_write(&namespace_sem);
1582
	mutex_lock(&old_nd.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
1583
	error = -EINVAL;
R
Ram Pai 已提交
1584 1585 1586 1587
	if (IS_MNT_SHARED(old_nd.mnt) ||
		IS_MNT_SHARED(new_nd.mnt->mnt_parent) ||
		IS_MNT_SHARED(user_nd.mnt->mnt_parent))
		goto out2;
L
Linus Torvalds 已提交
1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602
	if (!check_mnt(user_nd.mnt))
		goto out2;
	error = -ENOENT;
	if (IS_DEADDIR(new_nd.dentry->d_inode))
		goto out2;
	if (d_unhashed(new_nd.dentry) && !IS_ROOT(new_nd.dentry))
		goto out2;
	if (d_unhashed(old_nd.dentry) && !IS_ROOT(old_nd.dentry))
		goto out2;
	error = -EBUSY;
	if (new_nd.mnt == user_nd.mnt || old_nd.mnt == user_nd.mnt)
		goto out2; /* loop, on the same file system  */
	error = -EINVAL;
	if (user_nd.mnt->mnt_root != user_nd.dentry)
		goto out2; /* not a mountpoint */
1603 1604
	if (user_nd.mnt->mnt_parent == user_nd.mnt)
		goto out2; /* not attached */
L
Linus Torvalds 已提交
1605 1606
	if (new_nd.mnt->mnt_root != new_nd.dentry)
		goto out2; /* not a mountpoint */
1607 1608
	if (new_nd.mnt->mnt_parent == new_nd.mnt)
		goto out2; /* not attached */
L
Linus Torvalds 已提交
1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626
	tmp = old_nd.mnt; /* make sure we can reach put_old from new_root */
	spin_lock(&vfsmount_lock);
	if (tmp != new_nd.mnt) {
		for (;;) {
			if (tmp->mnt_parent == tmp)
				goto out3; /* already mounted on put_old */
			if (tmp->mnt_parent == new_nd.mnt)
				break;
			tmp = tmp->mnt_parent;
		}
		if (!is_subdir(tmp->mnt_mountpoint, new_nd.dentry))
			goto out3;
	} else if (!is_subdir(old_nd.dentry, new_nd.dentry))
		goto out3;
	detach_mnt(new_nd.mnt, &parent_nd);
	detach_mnt(user_nd.mnt, &root_parent);
	attach_mnt(user_nd.mnt, &old_nd);     /* mount old root on put_old */
	attach_mnt(new_nd.mnt, &root_parent); /* mount new_root on / */
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	touch_namespace(current->namespace);
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	spin_unlock(&vfsmount_lock);
	chroot_fs_refs(&user_nd, &new_nd);
	security_sb_post_pivotroot(&user_nd, &new_nd);
	error = 0;
	path_release(&root_parent);
	path_release(&parent_nd);
out2:
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	mutex_unlock(&old_nd.dentry->d_inode->i_mutex);
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	up_write(&namespace_sem);
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	path_release(&user_nd);
	path_release(&old_nd);
out1:
	path_release(&new_nd);
out0:
	unlock_kernel();
	return error;
out3:
	spin_unlock(&vfsmount_lock);
	goto out2;
}

static void __init init_mount_tree(void)
{
	struct vfsmount *mnt;
	struct namespace *namespace;
	struct task_struct *g, *p;

	mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
	if (IS_ERR(mnt))
		panic("Can't create rootfs");
	namespace = kmalloc(sizeof(*namespace), GFP_KERNEL);
	if (!namespace)
		panic("Can't allocate initial namespace");
	atomic_set(&namespace->count, 1);
	INIT_LIST_HEAD(&namespace->list);
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	init_waitqueue_head(&namespace->poll);
	namespace->event = 0;
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	list_add(&mnt->mnt_list, &namespace->list);
	namespace->root = mnt;
	mnt->mnt_namespace = namespace;

	init_task.namespace = namespace;
	read_lock(&tasklist_lock);
	do_each_thread(g, p) {
		get_namespace(namespace);
		p->namespace = namespace;
	} while_each_thread(g, p);
	read_unlock(&tasklist_lock);

	set_fs_pwd(current->fs, namespace->root, namespace->root->mnt_root);
	set_fs_root(current->fs, namespace->root, namespace->root->mnt_root);
}

void __init mnt_init(unsigned long mempages)
{
	struct list_head *d;
	unsigned int nr_hash;
	int i;

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	init_rwsem(&namespace_sem);

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	mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
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			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL, NULL);
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	mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
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	if (!mount_hashtable)
		panic("Failed to allocate mount hash table\n");

	/*
	 * Find the power-of-two list-heads that can fit into the allocation..
	 * We don't guarantee that "sizeof(struct list_head)" is necessarily
	 * a power-of-two.
	 */
	nr_hash = PAGE_SIZE / sizeof(struct list_head);
	hash_bits = 0;
	do {
		hash_bits++;
	} while ((nr_hash >> hash_bits) != 0);
	hash_bits--;

	/*
	 * Re-calculate the actual number of entries and the mask
	 * from the number of bits we can fit.
	 */
	nr_hash = 1UL << hash_bits;
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	hash_mask = nr_hash - 1;
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	printk("Mount-cache hash table entries: %d\n", nr_hash);

	/* And initialize the newly allocated array */
	d = mount_hashtable;
	i = nr_hash;
	do {
		INIT_LIST_HEAD(d);
		d++;
		i--;
	} while (i);
	sysfs_init();
	init_rootfs();
	init_mount_tree();
}

void __put_namespace(struct namespace *namespace)
{
1733
	struct vfsmount *root = namespace->root;
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	LIST_HEAD(umount_list);
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	namespace->root = NULL;
	spin_unlock(&vfsmount_lock);
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	down_write(&namespace_sem);
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	spin_lock(&vfsmount_lock);
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	umount_tree(root, 0, &umount_list);
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	spin_unlock(&vfsmount_lock);
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	up_write(&namespace_sem);
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	release_mounts(&umount_list);
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	kfree(namespace);
}