namespace.c 65.2 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/syscalls.h>
#include <linux/slab.h>
#include <linux/sched.h>
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#include <linux/spinlock.h>
#include <linux/percpu.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/acct.h>
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#include <linux/capability.h>
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#include <linux/cpumask.h>
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#include <linux/module.h>
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#include <linux/sysfs.h>
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#include <linux/seq_file.h>
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#include <linux/mnt_namespace.h>
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#include <linux/namei.h>
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#include <linux/nsproxy.h>
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#include <linux/security.h>
#include <linux/mount.h>
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#include <linux/ramfs.h>
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#include <linux/log2.h>
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#include <linux/idr.h>
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#include <linux/fs_struct.h>
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#include <linux/fsnotify.h>
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#include <asm/uaccess.h>
#include <asm/unistd.h>
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#include "pnode.h"
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#include "internal.h"
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#define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head))
#define HASH_SIZE (1UL << HASH_SHIFT)

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static int event;
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static DEFINE_IDA(mnt_id_ida);
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static DEFINE_IDA(mnt_group_ida);
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static DEFINE_SPINLOCK(mnt_id_lock);
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static int mnt_id_start = 0;
static int mnt_group_start = 1;
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static struct list_head *mount_hashtable __read_mostly;
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static struct kmem_cache *mnt_cache __read_mostly;
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static struct rw_semaphore namespace_sem;
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/* /sys/fs */
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struct kobject *fs_kobj;
EXPORT_SYMBOL_GPL(fs_kobj);
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/*
 * vfsmount lock may be taken for read to prevent changes to the
 * vfsmount hash, ie. during mountpoint lookups or walking back
 * up the tree.
 *
 * It should be taken for write in all cases where the vfsmount
 * tree or hash is modified or when a vfsmount structure is modified.
 */
DEFINE_BRLOCK(vfsmount_lock);

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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_SHIFT);
	return tmp & (HASH_SIZE - 1);
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}

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#define MNT_WRITER_UNDERFLOW_LIMIT -(1<<16)

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/*
 * allocation is serialized by namespace_sem, but we need the spinlock to
 * serialize with freeing.
 */
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static int mnt_alloc_id(struct vfsmount *mnt)
{
	int res;

retry:
	ida_pre_get(&mnt_id_ida, GFP_KERNEL);
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	spin_lock(&mnt_id_lock);
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	res = ida_get_new_above(&mnt_id_ida, mnt_id_start, &mnt->mnt_id);
	if (!res)
		mnt_id_start = mnt->mnt_id + 1;
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	spin_unlock(&mnt_id_lock);
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	if (res == -EAGAIN)
		goto retry;

	return res;
}

static void mnt_free_id(struct vfsmount *mnt)
{
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	int id = mnt->mnt_id;
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	spin_lock(&mnt_id_lock);
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	ida_remove(&mnt_id_ida, id);
	if (mnt_id_start > id)
		mnt_id_start = id;
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	spin_unlock(&mnt_id_lock);
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}

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/*
 * Allocate a new peer group ID
 *
 * mnt_group_ida is protected by namespace_sem
 */
static int mnt_alloc_group_id(struct vfsmount *mnt)
{
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	int res;

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	if (!ida_pre_get(&mnt_group_ida, GFP_KERNEL))
		return -ENOMEM;

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	res = ida_get_new_above(&mnt_group_ida,
				mnt_group_start,
				&mnt->mnt_group_id);
	if (!res)
		mnt_group_start = mnt->mnt_group_id + 1;

	return res;
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}

/*
 * Release a peer group ID
 */
void mnt_release_group_id(struct vfsmount *mnt)
{
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	int id = mnt->mnt_group_id;
	ida_remove(&mnt_group_ida, id);
	if (mnt_group_start > id)
		mnt_group_start = id;
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	mnt->mnt_group_id = 0;
}

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/*
 * vfsmount lock must be held for read
 */
static inline void mnt_add_count(struct vfsmount *mnt, int n)
{
#ifdef CONFIG_SMP
	this_cpu_add(mnt->mnt_pcp->mnt_count, n);
#else
	preempt_disable();
	mnt->mnt_count += n;
	preempt_enable();
#endif
}

static inline void mnt_set_count(struct vfsmount *mnt, int n)
{
#ifdef CONFIG_SMP
	this_cpu_write(mnt->mnt_pcp->mnt_count, n);
#else
	mnt->mnt_count = n;
#endif
}

/*
 * vfsmount lock must be held for read
 */
static inline void mnt_inc_count(struct vfsmount *mnt)
{
	mnt_add_count(mnt, 1);
}

/*
 * vfsmount lock must be held for read
 */
static inline void mnt_dec_count(struct vfsmount *mnt)
{
	mnt_add_count(mnt, -1);
}

/*
 * vfsmount lock must be held for write
 */
unsigned int mnt_get_count(struct vfsmount *mnt)
{
#ifdef CONFIG_SMP
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	unsigned int count = 0;
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	int cpu;

	for_each_possible_cpu(cpu) {
		count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count;
	}

	return count;
#else
	return mnt->mnt_count;
#endif
}

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static struct vfsmount *alloc_vfsmnt(const char *name)
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{
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	struct vfsmount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL);
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	if (mnt) {
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		int err;

		err = mnt_alloc_id(mnt);
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		if (err)
			goto out_free_cache;

		if (name) {
			mnt->mnt_devname = kstrdup(name, GFP_KERNEL);
			if (!mnt->mnt_devname)
				goto out_free_id;
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		}

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#ifdef CONFIG_SMP
		mnt->mnt_pcp = alloc_percpu(struct mnt_pcp);
		if (!mnt->mnt_pcp)
			goto out_free_devname;

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		this_cpu_add(mnt->mnt_pcp->mnt_count, 1);
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#else
		mnt->mnt_count = 1;
		mnt->mnt_writers = 0;
#endif

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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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#ifdef CONFIG_FSNOTIFY
		INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
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#endif
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	}
	return mnt;
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#ifdef CONFIG_SMP
out_free_devname:
	kfree(mnt->mnt_devname);
#endif
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out_free_id:
	mnt_free_id(mnt);
out_free_cache:
	kmem_cache_free(mnt_cache, mnt);
	return NULL;
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}

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/*
 * 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)
{
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	if (mnt->mnt_flags & MNT_READONLY)
		return 1;
	if (mnt->mnt_sb->s_flags & MS_RDONLY)
		return 1;
	return 0;
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}
EXPORT_SYMBOL_GPL(__mnt_is_readonly);

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static inline void mnt_inc_writers(struct vfsmount *mnt)
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{
#ifdef CONFIG_SMP
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	this_cpu_inc(mnt->mnt_pcp->mnt_writers);
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#else
	mnt->mnt_writers++;
#endif
}
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static inline void mnt_dec_writers(struct vfsmount *mnt)
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{
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#ifdef CONFIG_SMP
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	this_cpu_dec(mnt->mnt_pcp->mnt_writers);
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#else
	mnt->mnt_writers--;
#endif
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}

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static unsigned int mnt_get_writers(struct vfsmount *mnt)
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{
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#ifdef CONFIG_SMP
	unsigned int count = 0;
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	int cpu;

	for_each_possible_cpu(cpu) {
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		count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers;
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	}

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	return count;
#else
	return mnt->mnt_writers;
#endif
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}

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/*
 * 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)
{
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	int ret = 0;

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	preempt_disable();
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	mnt_inc_writers(mnt);
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	/*
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	 * The store to mnt_inc_writers must be visible before we pass
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	 * MNT_WRITE_HOLD loop below, so that the slowpath can see our
	 * incremented count after it has set MNT_WRITE_HOLD.
	 */
	smp_mb();
	while (mnt->mnt_flags & MNT_WRITE_HOLD)
		cpu_relax();
	/*
	 * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
	 * be set to match its requirements. So we must not load that until
	 * MNT_WRITE_HOLD is cleared.
	 */
	smp_rmb();
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	if (__mnt_is_readonly(mnt)) {
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		mnt_dec_writers(mnt);
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		ret = -EROFS;
		goto out;
	}
out:
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	preempt_enable();
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	return ret;
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}
EXPORT_SYMBOL_GPL(mnt_want_write);

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/**
 * mnt_clone_write - get write access to a mount
 * @mnt: the mount on which to take a write
 *
 * This is effectively like mnt_want_write, except
 * it must only be used to take an extra write reference
 * on a mountpoint that we already know has a write reference
 * on it. This allows some optimisation.
 *
 * After finished, mnt_drop_write must be called as usual to
 * drop the reference.
 */
int mnt_clone_write(struct vfsmount *mnt)
{
	/* superblock may be r/o */
	if (__mnt_is_readonly(mnt))
		return -EROFS;
	preempt_disable();
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	mnt_inc_writers(mnt);
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	preempt_enable();
	return 0;
}
EXPORT_SYMBOL_GPL(mnt_clone_write);

/**
 * mnt_want_write_file - get write access to a file's mount
 * @file: the file who's mount on which to take a write
 *
 * This is like mnt_want_write, but it takes a file and can
 * do some optimisations if the file is open for write already
 */
int mnt_want_write_file(struct file *file)
{
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	struct inode *inode = file->f_dentry->d_inode;
	if (!(file->f_mode & FMODE_WRITE) || special_file(inode->i_mode))
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		return mnt_want_write(file->f_path.mnt);
	else
		return mnt_clone_write(file->f_path.mnt);
}
EXPORT_SYMBOL_GPL(mnt_want_write_file);

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/**
 * 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)
{
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	preempt_disable();
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	mnt_dec_writers(mnt);
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	preempt_enable();
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}
EXPORT_SYMBOL_GPL(mnt_drop_write);

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static int mnt_make_readonly(struct vfsmount *mnt)
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{
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	int ret = 0;

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	br_write_lock(vfsmount_lock);
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	mnt->mnt_flags |= MNT_WRITE_HOLD;
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	/*
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	 * After storing MNT_WRITE_HOLD, we'll read the counters. This store
	 * should be visible before we do.
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	 */
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	smp_mb();

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	/*
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	 * With writers on hold, if this value is zero, then there are
	 * definitely no active writers (although held writers may subsequently
	 * increment the count, they'll have to wait, and decrement it after
	 * seeing MNT_READONLY).
	 *
	 * It is OK to have counter incremented on one CPU and decremented on
	 * another: the sum will add up correctly. The danger would be when we
	 * sum up each counter, if we read a counter before it is incremented,
	 * but then read another CPU's count which it has been subsequently
	 * decremented from -- we would see more decrements than we should.
	 * MNT_WRITE_HOLD protects against this scenario, because
	 * mnt_want_write first increments count, then smp_mb, then spins on
	 * MNT_WRITE_HOLD, so it can't be decremented by another CPU while
	 * we're counting up here.
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	 */
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	if (mnt_get_writers(mnt) > 0)
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		ret = -EBUSY;
	else
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		mnt->mnt_flags |= MNT_READONLY;
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	/*
	 * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers
	 * that become unheld will see MNT_READONLY.
	 */
	smp_wmb();
	mnt->mnt_flags &= ~MNT_WRITE_HOLD;
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	br_write_unlock(vfsmount_lock);
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	return ret;
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}

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static void __mnt_unmake_readonly(struct vfsmount *mnt)
{
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	br_write_lock(vfsmount_lock);
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	mnt->mnt_flags &= ~MNT_READONLY;
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	br_write_unlock(vfsmount_lock);
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}

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static void free_vfsmnt(struct vfsmount *mnt)
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{
	kfree(mnt->mnt_devname);
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	mnt_free_id(mnt);
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#ifdef CONFIG_SMP
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	free_percpu(mnt->mnt_pcp);
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#endif
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	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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 * vfsmount_lock must be held for read or write.
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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.
 */
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struct vfsmount *lookup_mnt(struct path *path)
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{
	struct vfsmount *child_mnt;
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	br_read_lock(vfsmount_lock);
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	if ((child_mnt = __lookup_mnt(path->mnt, path->dentry, 1)))
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		mntget(child_mnt);
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	br_read_unlock(vfsmount_lock);
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	return child_mnt;
}

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

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/*
 * vfsmount lock must be held for write
 */
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static void touch_mnt_namespace(struct mnt_namespace *ns)
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{
	if (ns) {
		ns->event = ++event;
		wake_up_interruptible(&ns->poll);
	}
}

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/*
 * vfsmount lock must be held for write
 */
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static void __touch_mnt_namespace(struct mnt_namespace *ns)
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{
	if (ns && ns->event != event) {
		ns->event = event;
		wake_up_interruptible(&ns->poll);
	}
}

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/*
 * Clear dentry's mounted state if it has no remaining mounts.
 * vfsmount_lock must be held for write.
 */
static void dentry_reset_mounted(struct vfsmount *mnt, struct dentry *dentry)
{
	unsigned u;

	for (u = 0; u < HASH_SIZE; u++) {
		struct vfsmount *p;

		list_for_each_entry(p, &mount_hashtable[u], mnt_hash) {
			if (p->mnt_mountpoint == dentry)
				return;
		}
	}
	spin_lock(&dentry->d_lock);
	dentry->d_flags &= ~DCACHE_MOUNTED;
	spin_unlock(&dentry->d_lock);
}

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/*
 * vfsmount lock must be held for write
 */
571
static void detach_mnt(struct vfsmount *mnt, struct path *old_path)
L
Linus Torvalds 已提交
572
{
573 574
	old_path->dentry = mnt->mnt_mountpoint;
	old_path->mnt = mnt->mnt_parent;
L
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575 576 577 578
	mnt->mnt_parent = mnt;
	mnt->mnt_mountpoint = mnt->mnt_root;
	list_del_init(&mnt->mnt_child);
	list_del_init(&mnt->mnt_hash);
N
Nick Piggin 已提交
579
	dentry_reset_mounted(old_path->mnt, old_path->dentry);
L
Linus Torvalds 已提交
580 581
}

N
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582 583 584
/*
 * vfsmount lock must be held for write
 */
585 586 587 588 589
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);
N
Nick Piggin 已提交
590 591 592
	spin_lock(&dentry->d_lock);
	dentry->d_flags |= DCACHE_MOUNTED;
	spin_unlock(&dentry->d_lock);
593 594
}

N
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595 596 597
/*
 * vfsmount lock must be held for write
 */
598
static void attach_mnt(struct vfsmount *mnt, struct path *path)
L
Linus Torvalds 已提交
599
{
600
	mnt_set_mountpoint(path->mnt, path->dentry, mnt);
601
	list_add_tail(&mnt->mnt_hash, mount_hashtable +
602 603
			hash(path->mnt, path->dentry));
	list_add_tail(&mnt->mnt_child, &path->mnt->mnt_mounts);
604 605
}

606 607 608 609 610 611 612 613 614 615 616 617 618 619 620
static inline void __mnt_make_longterm(struct vfsmount *mnt)
{
#ifdef CONFIG_SMP
	atomic_inc(&mnt->mnt_longterm);
#endif
}

/* needs vfsmount lock for write */
static inline void __mnt_make_shortterm(struct vfsmount *mnt)
{
#ifdef CONFIG_SMP
	atomic_dec(&mnt->mnt_longterm);
#endif
}

621
/*
N
Nick Piggin 已提交
622
 * vfsmount lock must be held for write
623 624 625 626 627 628
 */
static void commit_tree(struct vfsmount *mnt)
{
	struct vfsmount *parent = mnt->mnt_parent;
	struct vfsmount *m;
	LIST_HEAD(head);
629
	struct mnt_namespace *n = parent->mnt_ns;
630 631 632 633

	BUG_ON(parent == mnt);

	list_add_tail(&head, &mnt->mnt_list);
A
Al Viro 已提交
634
	list_for_each_entry(m, &head, mnt_list) {
635
		m->mnt_ns = n;
636
		__mnt_make_longterm(m);
A
Al Viro 已提交
637 638
	}

639 640 641 642 643
	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);
644
	touch_mnt_namespace(n);
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645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662
}

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;
}

673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702
struct vfsmount *
vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data)
{
	struct vfsmount *mnt;
	struct dentry *root;

	if (!type)
		return ERR_PTR(-ENODEV);

	mnt = alloc_vfsmnt(name);
	if (!mnt)
		return ERR_PTR(-ENOMEM);

	if (flags & MS_KERNMOUNT)
		mnt->mnt_flags = MNT_INTERNAL;

	root = mount_fs(type, flags, name, data);
	if (IS_ERR(root)) {
		free_vfsmnt(mnt);
		return ERR_CAST(root);
	}

	mnt->mnt_root = root;
	mnt->mnt_sb = root->d_sb;
	mnt->mnt_mountpoint = mnt->mnt_root;
	mnt->mnt_parent = mnt;
	return mnt;
}
EXPORT_SYMBOL_GPL(vfs_kern_mount);

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

	if (mnt) {
710 711 712 713 714 715 716 717 718 719 720
		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;
		}

721
		mnt->mnt_flags = old->mnt_flags & ~MNT_WRITE_HOLD;
L
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722 723 724 725 726
		atomic_inc(&sb->s_active);
		mnt->mnt_sb = sb;
		mnt->mnt_root = dget(root);
		mnt->mnt_mountpoint = mnt->mnt_root;
		mnt->mnt_parent = mnt;
727

R
Ram Pai 已提交
728 729 730 731
		if (flag & CL_SLAVE) {
			list_add(&mnt->mnt_slave, &old->mnt_slave_list);
			mnt->mnt_master = old;
			CLEAR_MNT_SHARED(mnt);
732
		} else if (!(flag & CL_PRIVATE)) {
733
			if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old))
R
Ram Pai 已提交
734 735 736 737 738
				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;
		}
739 740
		if (flag & CL_MAKE_SHARED)
			set_mnt_shared(mnt);
L
Linus Torvalds 已提交
741 742 743

		/* stick the duplicate mount on the same expiry list
		 * as the original if that was on one */
R
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744 745 746 747
		if (flag & CL_EXPIRE) {
			if (!list_empty(&old->mnt_expire))
				list_add(&mnt->mnt_expire, &old->mnt_expire);
		}
L
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748 749
	}
	return mnt;
750 751 752 753

 out_free:
	free_vfsmnt(mnt);
	return NULL;
L
Linus Torvalds 已提交
754 755
}

N
Nick Piggin 已提交
756
static inline void mntfree(struct vfsmount *mnt)
L
Linus Torvalds 已提交
757 758
{
	struct super_block *sb = mnt->mnt_sb;
N
Nick Piggin 已提交
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760 761 762 763 764 765
	/*
	 * 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.
	 */
N
npiggin@suse.de 已提交
766
	/*
N
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767 768
	 * The locking used to deal with mnt_count decrement provides barriers,
	 * so mnt_get_writers() below is safe.
N
npiggin@suse.de 已提交
769
	 */
770
	WARN_ON(mnt_get_writers(mnt));
771
	fsnotify_vfsmount_delete(mnt);
L
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772 773 774 775 776
	dput(mnt->mnt_root);
	free_vfsmnt(mnt);
	deactivate_super(sb);
}

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Al Viro 已提交
777
static void mntput_no_expire(struct vfsmount *mnt)
N
Nick Piggin 已提交
778 779
{
put_again:
A
Al Viro 已提交
780 781 782 783
#ifdef CONFIG_SMP
	br_read_lock(vfsmount_lock);
	if (likely(atomic_read(&mnt->mnt_longterm))) {
		mnt_dec_count(mnt);
N
Nick Piggin 已提交
784
		br_read_unlock(vfsmount_lock);
A
Al Viro 已提交
785
		return;
N
Nick Piggin 已提交
786
	}
A
Al Viro 已提交
787
	br_read_unlock(vfsmount_lock);
N
Nick Piggin 已提交
788

N
Nick Piggin 已提交
789
	br_write_lock(vfsmount_lock);
A
Al Viro 已提交
790
	mnt_dec_count(mnt);
N
Nick Piggin 已提交
791
	if (mnt_get_count(mnt)) {
N
Nick Piggin 已提交
792 793 794
		br_write_unlock(vfsmount_lock);
		return;
	}
N
Nick Piggin 已提交
795 796 797
#else
	mnt_dec_count(mnt);
	if (likely(mnt_get_count(mnt)))
N
Nick Piggin 已提交
798
		return;
N
Nick Piggin 已提交
799
	br_write_lock(vfsmount_lock);
A
Al Viro 已提交
800
#endif
N
Nick Piggin 已提交
801 802 803 804 805 806
	if (unlikely(mnt->mnt_pinned)) {
		mnt_add_count(mnt, mnt->mnt_pinned + 1);
		mnt->mnt_pinned = 0;
		br_write_unlock(vfsmount_lock);
		acct_auto_close_mnt(mnt);
		goto put_again;
807
	}
N
Nick Piggin 已提交
808
	br_write_unlock(vfsmount_lock);
N
Nick Piggin 已提交
809 810 811 812 813 814 815 816 817
	mntfree(mnt);
}

void mntput(struct vfsmount *mnt)
{
	if (mnt) {
		/* avoid cacheline pingpong, hope gcc doesn't get "smart" */
		if (unlikely(mnt->mnt_expiry_mark))
			mnt->mnt_expiry_mark = 0;
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Al Viro 已提交
818
		mntput_no_expire(mnt);
N
Nick Piggin 已提交
819 820 821 822 823 824 825 826 827 828 829 830
	}
}
EXPORT_SYMBOL(mntput);

struct vfsmount *mntget(struct vfsmount *mnt)
{
	if (mnt)
		mnt_inc_count(mnt);
	return mnt;
}
EXPORT_SYMBOL(mntget);

831 832
void mnt_pin(struct vfsmount *mnt)
{
N
Nick Piggin 已提交
833
	br_write_lock(vfsmount_lock);
834
	mnt->mnt_pinned++;
N
Nick Piggin 已提交
835
	br_write_unlock(vfsmount_lock);
836 837 838 839 840
}
EXPORT_SYMBOL(mnt_pin);

void mnt_unpin(struct vfsmount *mnt)
{
N
Nick Piggin 已提交
841
	br_write_lock(vfsmount_lock);
842
	if (mnt->mnt_pinned) {
N
Nick Piggin 已提交
843
		mnt_inc_count(mnt);
844 845
		mnt->mnt_pinned--;
	}
N
Nick Piggin 已提交
846
	br_write_unlock(vfsmount_lock);
847 848
}
EXPORT_SYMBOL(mnt_unpin);
L
Linus Torvalds 已提交
849

850 851 852 853 854 855 856 857 858 859 860 861 862
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)
{
863 864 865 866
	const char *options;

	rcu_read_lock();
	options = rcu_dereference(mnt->mnt_sb->s_options);
867 868 869 870 871

	if (options != NULL && options[0]) {
		seq_putc(m, ',');
		mangle(m, options);
	}
872
	rcu_read_unlock();
873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892

	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)
{
893 894
	BUG_ON(sb->s_options);
	rcu_assign_pointer(sb->s_options, kstrdup(options, GFP_KERNEL));
895 896 897
}
EXPORT_SYMBOL(save_mount_options);

898 899 900 901 902 903 904 905 906 907 908
void replace_mount_options(struct super_block *sb, char *options)
{
	char *old = sb->s_options;
	rcu_assign_pointer(sb->s_options, options);
	if (old) {
		synchronize_rcu();
		kfree(old);
	}
}
EXPORT_SYMBOL(replace_mount_options);

909
#ifdef CONFIG_PROC_FS
L
Linus Torvalds 已提交
910 911 912
/* iterator */
static void *m_start(struct seq_file *m, loff_t *pos)
{
913
	struct proc_mounts *p = m->private;
L
Linus Torvalds 已提交
914

R
Ram Pai 已提交
915
	down_read(&namespace_sem);
916
	return seq_list_start(&p->ns->list, *pos);
L
Linus Torvalds 已提交
917 918 919 920
}

static void *m_next(struct seq_file *m, void *v, loff_t *pos)
{
921
	struct proc_mounts *p = m->private;
922

923
	return seq_list_next(v, &p->ns->list, pos);
L
Linus Torvalds 已提交
924 925 926 927
}

static void m_stop(struct seq_file *m, void *v)
{
R
Ram Pai 已提交
928
	up_read(&namespace_sem);
L
Linus Torvalds 已提交
929 930
}

931 932 933 934 935
int mnt_had_events(struct proc_mounts *p)
{
	struct mnt_namespace *ns = p->ns;
	int res = 0;

N
Nick Piggin 已提交
936
	br_read_lock(vfsmount_lock);
937 938 939 940
	if (p->event != ns->event) {
		p->event = ns->event;
		res = 1;
	}
N
Nick Piggin 已提交
941
	br_read_unlock(vfsmount_lock);
942 943 944 945

	return res;
}

946 947 948 949 950
struct proc_fs_info {
	int flag;
	const char *str;
};

951
static int show_sb_opts(struct seq_file *m, struct super_block *sb)
L
Linus Torvalds 已提交
952
{
953
	static const struct proc_fs_info fs_info[] = {
L
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954 955 956 957 958
		{ MS_SYNCHRONOUS, ",sync" },
		{ MS_DIRSYNC, ",dirsync" },
		{ MS_MANDLOCK, ",mand" },
		{ 0, NULL }
	};
959 960 961 962 963 964
	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);
	}
965 966

	return security_sb_show_options(m, sb);
967 968 969 970 971
}

static void show_mnt_opts(struct seq_file *m, struct vfsmount *mnt)
{
	static const struct proc_fs_info mnt_info[] = {
L
Linus Torvalds 已提交
972 973 974
		{ MNT_NOSUID, ",nosuid" },
		{ MNT_NODEV, ",nodev" },
		{ MNT_NOEXEC, ",noexec" },
975 976
		{ MNT_NOATIME, ",noatime" },
		{ MNT_NODIRATIME, ",nodiratime" },
V
Valerie Henson 已提交
977
		{ MNT_RELATIME, ",relatime" },
L
Linus Torvalds 已提交
978 979
		{ 0, NULL }
	};
980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000
	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;
1001
	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
L
Linus Torvalds 已提交
1002

1003 1004 1005 1006 1007 1008 1009
	if (mnt->mnt_sb->s_op->show_devname) {
		err = mnt->mnt_sb->s_op->show_devname(m, mnt);
		if (err)
			goto out;
	} else {
		mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
	}
L
Linus Torvalds 已提交
1010
	seq_putc(m, ' ');
1011
	seq_path(m, &mnt_path, " \t\n\\");
L
Linus Torvalds 已提交
1012
	seq_putc(m, ' ');
1013
	show_type(m, mnt->mnt_sb);
1014
	seq_puts(m, __mnt_is_readonly(mnt) ? " ro" : " rw");
1015 1016 1017
	err = show_sb_opts(m, mnt->mnt_sb);
	if (err)
		goto out;
1018
	show_mnt_opts(m, mnt);
L
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1019 1020 1021
	if (mnt->mnt_sb->s_op->show_options)
		err = mnt->mnt_sb->s_op->show_options(m, mnt);
	seq_puts(m, " 0 0\n");
1022
out:
L
Linus Torvalds 已提交
1023 1024 1025
	return err;
}

1026
const struct seq_operations mounts_op = {
L
Linus Torvalds 已提交
1027 1028 1029 1030 1031 1032
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_vfsmnt
};

1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044
static int uuid_is_nil(u8 *uuid)
{
	int i;
	u8  *cp = (u8 *)uuid;

	for (i = 0; i < 16; i++) {
		if (*cp++)
			return 0;
	}
	return 1;
}

1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055
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));
1056 1057 1058 1059 1060 1061
	if (sb->s_op->show_path)
		err = sb->s_op->show_path(m, mnt);
	else
		seq_dentry(m, mnt->mnt_root, " \t\n\\");
	if (err)
		goto out;
1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077
	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);
1078 1079 1080 1081 1082 1083 1084
	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);
	}
1085 1086 1087
	if (IS_MNT_UNBINDABLE(mnt))
		seq_puts(m, " unbindable");

1088 1089 1090 1091
	if (!uuid_is_nil(mnt->mnt_sb->s_uuid))
		/* print the uuid */
		seq_printf(m, " uuid:%pU", mnt->mnt_sb->s_uuid);

1092 1093 1094 1095
	/* Filesystem specific data */
	seq_puts(m, " - ");
	show_type(m, sb);
	seq_putc(m, ' ');
1096 1097 1098 1099 1100 1101
	if (sb->s_op->show_devname)
		err = sb->s_op->show_devname(m, mnt);
	else
		mangle(m, mnt->mnt_devname ? mnt->mnt_devname : "none");
	if (err)
		goto out;
1102
	seq_puts(m, sb->s_flags & MS_RDONLY ? " ro" : " rw");
1103 1104 1105
	err = show_sb_opts(m, sb);
	if (err)
		goto out;
1106 1107 1108
	if (sb->s_op->show_options)
		err = sb->s_op->show_options(m, mnt);
	seq_putc(m, '\n');
1109
out:
1110 1111 1112 1113 1114 1115 1116 1117 1118 1119
	return err;
}

const struct seq_operations mountinfo_op = {
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_mountinfo,
};

1120 1121
static int show_vfsstat(struct seq_file *m, void *v)
{
1122
	struct vfsmount *mnt = list_entry(v, struct vfsmount, mnt_list);
1123
	struct path mnt_path = { .dentry = mnt->mnt_root, .mnt = mnt };
1124 1125 1126
	int err = 0;

	/* device */
1127 1128 1129 1130 1131 1132 1133 1134 1135
	if (mnt->mnt_sb->s_op->show_devname) {
		err = mnt->mnt_sb->s_op->show_devname(m, mnt);
	} else {
		if (mnt->mnt_devname) {
			seq_puts(m, "device ");
			mangle(m, mnt->mnt_devname);
		} else
			seq_puts(m, "no device");
	}
1136 1137 1138

	/* mount point */
	seq_puts(m, " mounted on ");
1139
	seq_path(m, &mnt_path, " \t\n\\");
1140 1141 1142 1143
	seq_putc(m, ' ');

	/* file system type */
	seq_puts(m, "with fstype ");
1144
	show_type(m, mnt->mnt_sb);
1145 1146 1147 1148

	/* optional statistics */
	if (mnt->mnt_sb->s_op->show_stats) {
		seq_putc(m, ' ');
1149 1150
		if (!err)
			err = mnt->mnt_sb->s_op->show_stats(m, mnt);
1151 1152 1153 1154 1155 1156
	}

	seq_putc(m, '\n');
	return err;
}

1157
const struct seq_operations mountstats_op = {
1158 1159 1160 1161 1162
	.start	= m_start,
	.next	= m_next,
	.stop	= m_stop,
	.show	= show_vfsstat,
};
1163
#endif  /* CONFIG_PROC_FS */
1164

L
Linus Torvalds 已提交
1165 1166 1167 1168 1169 1170 1171 1172 1173 1174
/**
 * 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)
{
R
Ram Pai 已提交
1175 1176 1177
	int actual_refs = 0;
	int minimum_refs = 0;
	struct vfsmount *p;
L
Linus Torvalds 已提交
1178

N
Nick Piggin 已提交
1179 1180
	/* write lock needed for mnt_get_count */
	br_write_lock(vfsmount_lock);
R
Ram Pai 已提交
1181
	for (p = mnt; p; p = next_mnt(p, mnt)) {
N
Nick Piggin 已提交
1182
		actual_refs += mnt_get_count(p);
L
Linus Torvalds 已提交
1183 1184
		minimum_refs += 2;
	}
N
Nick Piggin 已提交
1185
	br_write_unlock(vfsmount_lock);
L
Linus Torvalds 已提交
1186 1187

	if (actual_refs > minimum_refs)
1188
		return 0;
L
Linus Torvalds 已提交
1189

1190
	return 1;
L
Linus Torvalds 已提交
1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209
}

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)
{
1210
	int ret = 1;
A
Al Viro 已提交
1211
	down_read(&namespace_sem);
N
Nick Piggin 已提交
1212
	br_write_lock(vfsmount_lock);
R
Ram Pai 已提交
1213
	if (propagate_mount_busy(mnt, 2))
1214
		ret = 0;
N
Nick Piggin 已提交
1215
	br_write_unlock(vfsmount_lock);
A
Al Viro 已提交
1216
	up_read(&namespace_sem);
R
Ram Pai 已提交
1217
	return ret;
L
Linus Torvalds 已提交
1218 1219 1220 1221
}

EXPORT_SYMBOL(may_umount);

1222
void release_mounts(struct list_head *head)
R
Ram Pai 已提交
1223 1224
{
	struct vfsmount *mnt;
M
Miklos Szeredi 已提交
1225
	while (!list_empty(head)) {
1226
		mnt = list_first_entry(head, struct vfsmount, mnt_hash);
R
Ram Pai 已提交
1227 1228 1229 1230
		list_del_init(&mnt->mnt_hash);
		if (mnt->mnt_parent != mnt) {
			struct dentry *dentry;
			struct vfsmount *m;
N
Nick Piggin 已提交
1231 1232

			br_write_lock(vfsmount_lock);
R
Ram Pai 已提交
1233 1234 1235 1236
			dentry = mnt->mnt_mountpoint;
			m = mnt->mnt_parent;
			mnt->mnt_mountpoint = mnt->mnt_root;
			mnt->mnt_parent = mnt;
1237
			m->mnt_ghosts--;
N
Nick Piggin 已提交
1238
			br_write_unlock(vfsmount_lock);
R
Ram Pai 已提交
1239 1240 1241
			dput(dentry);
			mntput(m);
		}
A
Al Viro 已提交
1242
		mntput(mnt);
R
Ram Pai 已提交
1243 1244 1245
	}
}

N
Nick Piggin 已提交
1246 1247 1248 1249
/*
 * vfsmount lock must be held for write
 * namespace_sem must be held for write
 */
R
Ram Pai 已提交
1250
void umount_tree(struct vfsmount *mnt, int propagate, struct list_head *kill)
L
Linus Torvalds 已提交
1251
{
A
Al Viro 已提交
1252
	LIST_HEAD(tmp_list);
L
Linus Torvalds 已提交
1253 1254
	struct vfsmount *p;

A
Akinobu Mita 已提交
1255
	for (p = mnt; p; p = next_mnt(p, mnt))
A
Al Viro 已提交
1256
		list_move(&p->mnt_hash, &tmp_list);
L
Linus Torvalds 已提交
1257

R
Ram Pai 已提交
1258
	if (propagate)
A
Al Viro 已提交
1259
		propagate_umount(&tmp_list);
R
Ram Pai 已提交
1260

A
Al Viro 已提交
1261
	list_for_each_entry(p, &tmp_list, mnt_hash) {
R
Ram Pai 已提交
1262 1263
		list_del_init(&p->mnt_expire);
		list_del_init(&p->mnt_list);
1264 1265
		__touch_mnt_namespace(p->mnt_ns);
		p->mnt_ns = NULL;
1266
		__mnt_make_shortterm(p);
R
Ram Pai 已提交
1267
		list_del_init(&p->mnt_child);
1268 1269
		if (p->mnt_parent != p) {
			p->mnt_parent->mnt_ghosts++;
N
Nick Piggin 已提交
1270
			dentry_reset_mounted(p->mnt_parent, p->mnt_mountpoint);
1271
		}
R
Ram Pai 已提交
1272
		change_mnt_propagation(p, MS_PRIVATE);
L
Linus Torvalds 已提交
1273
	}
A
Al Viro 已提交
1274
	list_splice(&tmp_list, kill);
L
Linus Torvalds 已提交
1275 1276
}

1277 1278
static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts);

L
Linus Torvalds 已提交
1279 1280
static int do_umount(struct vfsmount *mnt, int flags)
{
R
Ram Pai 已提交
1281
	struct super_block *sb = mnt->mnt_sb;
L
Linus Torvalds 已提交
1282
	int retval;
R
Ram Pai 已提交
1283
	LIST_HEAD(umount_list);
L
Linus Torvalds 已提交
1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295

	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) {
J
Jan Blunck 已提交
1296
		if (mnt == current->fs->root.mnt ||
L
Linus Torvalds 已提交
1297 1298 1299
		    flags & (MNT_FORCE | MNT_DETACH))
			return -EINVAL;

N
Nick Piggin 已提交
1300 1301 1302 1303 1304 1305
		/*
		 * probably don't strictly need the lock here if we examined
		 * all race cases, but it's a slowpath.
		 */
		br_write_lock(vfsmount_lock);
		if (mnt_get_count(mnt) != 2) {
1306
			br_write_unlock(vfsmount_lock);
L
Linus Torvalds 已提交
1307
			return -EBUSY;
N
Nick Piggin 已提交
1308 1309
		}
		br_write_unlock(vfsmount_lock);
L
Linus Torvalds 已提交
1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324

		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.
	 */

1325 1326 1327
	if (flags & MNT_FORCE && sb->s_op->umount_begin) {
		sb->s_op->umount_begin(sb);
	}
L
Linus Torvalds 已提交
1328 1329 1330 1331 1332 1333 1334 1335 1336 1337

	/*
	 * 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.
	 */
J
Jan Blunck 已提交
1338
	if (mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) {
L
Linus Torvalds 已提交
1339 1340 1341 1342 1343
		/*
		 * Special case for "unmounting" root ...
		 * we just try to remount it readonly.
		 */
		down_write(&sb->s_umount);
A
Al Viro 已提交
1344
		if (!(sb->s_flags & MS_RDONLY))
L
Linus Torvalds 已提交
1345 1346 1347 1348 1349
			retval = do_remount_sb(sb, MS_RDONLY, NULL, 0);
		up_write(&sb->s_umount);
		return retval;
	}

R
Ram Pai 已提交
1350
	down_write(&namespace_sem);
N
Nick Piggin 已提交
1351
	br_write_lock(vfsmount_lock);
A
Al Viro 已提交
1352
	event++;
L
Linus Torvalds 已提交
1353

1354 1355 1356
	if (!(flags & MNT_DETACH))
		shrink_submounts(mnt, &umount_list);

L
Linus Torvalds 已提交
1357
	retval = -EBUSY;
R
Ram Pai 已提交
1358
	if (flags & MNT_DETACH || !propagate_mount_busy(mnt, 2)) {
L
Linus Torvalds 已提交
1359
		if (!list_empty(&mnt->mnt_list))
R
Ram Pai 已提交
1360
			umount_tree(mnt, 1, &umount_list);
L
Linus Torvalds 已提交
1361 1362
		retval = 0;
	}
N
Nick Piggin 已提交
1363
	br_write_unlock(vfsmount_lock);
R
Ram Pai 已提交
1364
	up_write(&namespace_sem);
R
Ram Pai 已提交
1365
	release_mounts(&umount_list);
L
Linus Torvalds 已提交
1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376
	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
 */

1377
SYSCALL_DEFINE2(umount, char __user *, name, int, flags)
L
Linus Torvalds 已提交
1378
{
1379
	struct path path;
L
Linus Torvalds 已提交
1380
	int retval;
1381
	int lookup_flags = 0;
L
Linus Torvalds 已提交
1382

1383 1384 1385 1386 1387 1388 1389
	if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW))
		return -EINVAL;

	if (!(flags & UMOUNT_NOFOLLOW))
		lookup_flags |= LOOKUP_FOLLOW;

	retval = user_path_at(AT_FDCWD, name, lookup_flags, &path);
L
Linus Torvalds 已提交
1390 1391 1392
	if (retval)
		goto out;
	retval = -EINVAL;
1393
	if (path.dentry != path.mnt->mnt_root)
L
Linus Torvalds 已提交
1394
		goto dput_and_out;
1395
	if (!check_mnt(path.mnt))
L
Linus Torvalds 已提交
1396 1397 1398 1399 1400 1401
		goto dput_and_out;

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

1402
	retval = do_umount(path.mnt, flags);
L
Linus Torvalds 已提交
1403
dput_and_out:
J
Jan Blunck 已提交
1404
	/* we mustn't call path_put() as that would clear mnt_expiry_mark */
1405 1406
	dput(path.dentry);
	mntput_no_expire(path.mnt);
L
Linus Torvalds 已提交
1407 1408 1409 1410 1411 1412 1413
out:
	return retval;
}

#ifdef __ARCH_WANT_SYS_OLDUMOUNT

/*
R
Ram Pai 已提交
1414
 *	The 2.0 compatible umount. No flags.
L
Linus Torvalds 已提交
1415
 */
1416
SYSCALL_DEFINE1(oldumount, char __user *, name)
L
Linus Torvalds 已提交
1417
{
R
Ram Pai 已提交
1418
	return sys_umount(name, 0);
L
Linus Torvalds 已提交
1419 1420 1421 1422
}

#endif

1423
static int mount_is_safe(struct path *path)
L
Linus Torvalds 已提交
1424 1425 1426 1427 1428
{
	if (capable(CAP_SYS_ADMIN))
		return 0;
	return -EPERM;
#ifdef notyet
1429
	if (S_ISLNK(path->dentry->d_inode->i_mode))
L
Linus Torvalds 已提交
1430
		return -EPERM;
1431
	if (path->dentry->d_inode->i_mode & S_ISVTX) {
1432
		if (current_uid() != path->dentry->d_inode->i_uid)
L
Linus Torvalds 已提交
1433 1434
			return -EPERM;
	}
1435
	if (inode_permission(path->dentry->d_inode, MAY_WRITE))
L
Linus Torvalds 已提交
1436 1437 1438 1439 1440
		return -EPERM;
	return 0;
#endif
}

1441
struct vfsmount *copy_tree(struct vfsmount *mnt, struct dentry *dentry,
R
Ram Pai 已提交
1442
					int flag)
L
Linus Torvalds 已提交
1443 1444
{
	struct vfsmount *res, *p, *q, *r, *s;
1445
	struct path path;
L
Linus Torvalds 已提交
1446

R
Ram Pai 已提交
1447 1448 1449
	if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(mnt))
		return NULL;

R
Ram Pai 已提交
1450
	res = q = clone_mnt(mnt, dentry, flag);
L
Linus Torvalds 已提交
1451 1452 1453 1454 1455
	if (!q)
		goto Enomem;
	q->mnt_mountpoint = mnt->mnt_mountpoint;

	p = mnt;
1456
	list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) {
1457
		if (!is_subdir(r->mnt_mountpoint, dentry))
L
Linus Torvalds 已提交
1458 1459 1460
			continue;

		for (s = r; s; s = next_mnt(s, r)) {
R
Ram Pai 已提交
1461 1462 1463 1464
			if (!(flag & CL_COPY_ALL) && IS_MNT_UNBINDABLE(s)) {
				s = skip_mnt_tree(s);
				continue;
			}
L
Linus Torvalds 已提交
1465 1466 1467 1468 1469
			while (p != s->mnt_parent) {
				p = p->mnt_parent;
				q = q->mnt_parent;
			}
			p = s;
1470 1471
			path.mnt = q;
			path.dentry = p->mnt_mountpoint;
R
Ram Pai 已提交
1472
			q = clone_mnt(p, p->mnt_root, flag);
L
Linus Torvalds 已提交
1473 1474
			if (!q)
				goto Enomem;
N
Nick Piggin 已提交
1475
			br_write_lock(vfsmount_lock);
L
Linus Torvalds 已提交
1476
			list_add_tail(&q->mnt_list, &res->mnt_list);
1477
			attach_mnt(q, &path);
N
Nick Piggin 已提交
1478
			br_write_unlock(vfsmount_lock);
L
Linus Torvalds 已提交
1479 1480 1481
		}
	}
	return res;
R
Ram Pai 已提交
1482
Enomem:
L
Linus Torvalds 已提交
1483
	if (res) {
R
Ram Pai 已提交
1484
		LIST_HEAD(umount_list);
N
Nick Piggin 已提交
1485
		br_write_lock(vfsmount_lock);
R
Ram Pai 已提交
1486
		umount_tree(res, 0, &umount_list);
N
Nick Piggin 已提交
1487
		br_write_unlock(vfsmount_lock);
R
Ram Pai 已提交
1488
		release_mounts(&umount_list);
L
Linus Torvalds 已提交
1489 1490 1491 1492
	}
	return NULL;
}

A
Al Viro 已提交
1493
struct vfsmount *collect_mounts(struct path *path)
1494 1495
{
	struct vfsmount *tree;
1496
	down_write(&namespace_sem);
A
Al Viro 已提交
1497
	tree = copy_tree(path->mnt, path->dentry, CL_COPY_ALL | CL_PRIVATE);
1498
	up_write(&namespace_sem);
1499 1500 1501 1502 1503 1504
	return tree;
}

void drop_collected_mounts(struct vfsmount *mnt)
{
	LIST_HEAD(umount_list);
1505
	down_write(&namespace_sem);
N
Nick Piggin 已提交
1506
	br_write_lock(vfsmount_lock);
1507
	umount_tree(mnt, 0, &umount_list);
N
Nick Piggin 已提交
1508
	br_write_unlock(vfsmount_lock);
1509
	up_write(&namespace_sem);
1510 1511 1512
	release_mounts(&umount_list);
}

A
Al Viro 已提交
1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527
int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg,
		   struct vfsmount *root)
{
	struct vfsmount *mnt;
	int res = f(root, arg);
	if (res)
		return res;
	list_for_each_entry(mnt, &root->mnt_list, mnt_list) {
		res = f(mnt, arg);
		if (res)
			return res;
	}
	return 0;
}

1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554
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;
}

1555 1556
/*
 *  @source_mnt : mount tree to be attached
R
Ram Pai 已提交
1557 1558 1559 1560
 *  @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)
1561 1562 1563
 *
 *  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
Ram Pai 已提交
1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575
 * ---------------------------------------------------------------------------
 * |         BIND MOUNT OPERATION                                            |
 * |**************************************************************************
 * | source-->| shared        |       private  |       slave    | unbindable |
 * | dest     |               |                |                |            |
 * |   |      |               |                |                |            |
 * |   v      |               |                |                |            |
 * |**************************************************************************
 * |  shared  | shared (++)   |     shared (+) |     shared(+++)|  invalid   |
 * |          |               |                |                |            |
 * |non-shared| shared (+)    |      private   |      slave (*) |  invalid   |
 * ***************************************************************************
1576 1577 1578 1579 1580 1581 1582 1583 1584
 * 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
Ram Pai 已提交
1585 1586 1587 1588 1589 1590 1591
 * (+++) 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
Ram Pai 已提交
1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603
 * ---------------------------------------------------------------------------
 * |         		MOVE MOUNT OPERATION                                 |
 * |**************************************************************************
 * | source-->| shared        |       private  |       slave    | unbindable |
 * | dest     |               |                |                |            |
 * |   |      |               |                |                |            |
 * |   v      |               |                |                |            |
 * |**************************************************************************
 * |  shared  | shared (+)    |     shared (+) |    shared(+++) |  invalid   |
 * |          |               |                |                |            |
 * |non-shared| shared (+*)   |      private   |    slave (*)   | unbindable |
 * ***************************************************************************
R
Ram Pai 已提交
1604 1605 1606
 *
 * (+)  the mount is moved to the destination. And is then propagated to
 * 	all the mounts in the propagation tree of the destination mount.
R
Ram Pai 已提交
1607
 * (+*)  the mount is moved to the destination.
R
Ram Pai 已提交
1608 1609 1610 1611
 * (+++)  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.
1612 1613 1614 1615 1616 1617 1618
 *
 * 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,
1619
			struct path *path, struct path *parent_path)
1620 1621
{
	LIST_HEAD(tree_list);
1622 1623
	struct vfsmount *dest_mnt = path->mnt;
	struct dentry *dest_dentry = path->dentry;
1624
	struct vfsmount *child, *p;
1625
	int err;
1626

1627 1628 1629 1630 1631 1632 1633 1634
	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;
1635

N
Nick Piggin 已提交
1636
	br_write_lock(vfsmount_lock);
1637

1638 1639 1640 1641
	if (IS_MNT_SHARED(dest_mnt)) {
		for (p = source_mnt; p; p = next_mnt(p, source_mnt))
			set_mnt_shared(p);
	}
1642 1643 1644
	if (parent_path) {
		detach_mnt(source_mnt, parent_path);
		attach_mnt(source_mnt, path);
1645
		touch_mnt_namespace(parent_path->mnt->mnt_ns);
R
Ram Pai 已提交
1646 1647 1648 1649
	} else {
		mnt_set_mountpoint(dest_mnt, dest_dentry, source_mnt);
		commit_tree(source_mnt);
	}
1650 1651 1652 1653 1654

	list_for_each_entry_safe(child, p, &tree_list, mnt_hash) {
		list_del_init(&child->mnt_hash);
		commit_tree(child);
	}
N
Nick Piggin 已提交
1655 1656
	br_write_unlock(vfsmount_lock);

1657
	return 0;
1658 1659 1660 1661 1662 1663

 out_cleanup_ids:
	if (IS_MNT_SHARED(dest_mnt))
		cleanup_group_ids(source_mnt, NULL);
 out:
	return err;
1664 1665
}

1666
static int graft_tree(struct vfsmount *mnt, struct path *path)
L
Linus Torvalds 已提交
1667 1668 1669 1670 1671
{
	int err;
	if (mnt->mnt_sb->s_flags & MS_NOUSER)
		return -EINVAL;

1672
	if (S_ISDIR(path->dentry->d_inode->i_mode) !=
L
Linus Torvalds 已提交
1673 1674 1675 1676
	      S_ISDIR(mnt->mnt_root->d_inode->i_mode))
		return -ENOTDIR;

	err = -ENOENT;
1677
	mutex_lock(&path->dentry->d_inode->i_mutex);
1678
	if (cant_mount(path->dentry))
L
Linus Torvalds 已提交
1679 1680
		goto out_unlock;

1681
	if (!d_unlinked(path->dentry))
1682
		err = attach_recursive_mnt(mnt, path, NULL);
L
Linus Torvalds 已提交
1683
out_unlock:
1684
	mutex_unlock(&path->dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
1685 1686 1687
	return err;
}

1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704
/*
 * Sanity check the flags to change_mnt_propagation.
 */

static int flags_to_propagation_type(int flags)
{
	int type = flags & ~MS_REC;

	/* Fail if any non-propagation flags are set */
	if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
		return 0;
	/* Only one propagation flag should be set */
	if (!is_power_of_2(type))
		return 0;
	return type;
}

1705 1706 1707
/*
 * recursively change the type of the mountpoint.
 */
1708
static int do_change_type(struct path *path, int flag)
1709
{
1710
	struct vfsmount *m, *mnt = path->mnt;
1711
	int recurse = flag & MS_REC;
1712
	int type;
1713
	int err = 0;
1714

1715 1716 1717
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;

1718
	if (path->dentry != path->mnt->mnt_root)
1719 1720
		return -EINVAL;

1721 1722 1723 1724
	type = flags_to_propagation_type(flag);
	if (!type)
		return -EINVAL;

1725
	down_write(&namespace_sem);
1726 1727 1728 1729 1730 1731
	if (type == MS_SHARED) {
		err = invent_group_ids(mnt, recurse);
		if (err)
			goto out_unlock;
	}

N
Nick Piggin 已提交
1732
	br_write_lock(vfsmount_lock);
1733 1734
	for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL))
		change_mnt_propagation(m, type);
N
Nick Piggin 已提交
1735
	br_write_unlock(vfsmount_lock);
1736 1737

 out_unlock:
1738
	up_write(&namespace_sem);
1739
	return err;
1740 1741
}

L
Linus Torvalds 已提交
1742 1743 1744
/*
 * do loopback mount.
 */
1745
static int do_loopback(struct path *path, char *old_name,
1746
				int recurse)
L
Linus Torvalds 已提交
1747
{
1748
	struct path old_path;
L
Linus Torvalds 已提交
1749
	struct vfsmount *mnt = NULL;
1750
	int err = mount_is_safe(path);
L
Linus Torvalds 已提交
1751 1752 1753 1754
	if (err)
		return err;
	if (!old_name || !*old_name)
		return -EINVAL;
1755
	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
L
Linus Torvalds 已提交
1756 1757 1758
	if (err)
		return err;

R
Ram Pai 已提交
1759
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
1760
	err = -EINVAL;
1761
	if (IS_MNT_UNBINDABLE(old_path.mnt))
1762
		goto out;
R
Ram Pai 已提交
1763

1764
	if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
1765
		goto out;
L
Linus Torvalds 已提交
1766

1767 1768
	err = -ENOMEM;
	if (recurse)
1769
		mnt = copy_tree(old_path.mnt, old_path.dentry, 0);
1770
	else
1771
		mnt = clone_mnt(old_path.mnt, old_path.dentry, 0);
1772 1773 1774 1775

	if (!mnt)
		goto out;

1776
	err = graft_tree(mnt, path);
1777
	if (err) {
R
Ram Pai 已提交
1778
		LIST_HEAD(umount_list);
N
Nick Piggin 已提交
1779 1780

		br_write_lock(vfsmount_lock);
R
Ram Pai 已提交
1781
		umount_tree(mnt, 0, &umount_list);
N
Nick Piggin 已提交
1782
		br_write_unlock(vfsmount_lock);
R
Ram Pai 已提交
1783
		release_mounts(&umount_list);
1784
	}
L
Linus Torvalds 已提交
1785

1786
out:
R
Ram Pai 已提交
1787
	up_write(&namespace_sem);
1788
	path_put(&old_path);
L
Linus Torvalds 已提交
1789 1790 1791
	return err;
}

1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808
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;
}

L
Linus Torvalds 已提交
1809 1810 1811 1812 1813
/*
 * 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.
 */
1814
static int do_remount(struct path *path, int flags, int mnt_flags,
L
Linus Torvalds 已提交
1815 1816 1817
		      void *data)
{
	int err;
1818
	struct super_block *sb = path->mnt->mnt_sb;
L
Linus Torvalds 已提交
1819 1820 1821 1822

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

1823
	if (!check_mnt(path->mnt))
L
Linus Torvalds 已提交
1824 1825
		return -EINVAL;

1826
	if (path->dentry != path->mnt->mnt_root)
L
Linus Torvalds 已提交
1827 1828
		return -EINVAL;

1829 1830 1831 1832
	err = security_sb_remount(sb, data);
	if (err)
		return err;

L
Linus Torvalds 已提交
1833
	down_write(&sb->s_umount);
1834
	if (flags & MS_BIND)
1835
		err = change_mount_flags(path->mnt, flags);
A
Al Viro 已提交
1836
	else
1837
		err = do_remount_sb(sb, flags, data, 0);
A
Al Viro 已提交
1838
	if (!err) {
N
Nick Piggin 已提交
1839
		br_write_lock(vfsmount_lock);
1840
		mnt_flags |= path->mnt->mnt_flags & MNT_PROPAGATION_MASK;
1841
		path->mnt->mnt_flags = mnt_flags;
N
Nick Piggin 已提交
1842
		br_write_unlock(vfsmount_lock);
A
Al Viro 已提交
1843
	}
L
Linus Torvalds 已提交
1844
	up_write(&sb->s_umount);
1845
	if (!err) {
N
Nick Piggin 已提交
1846
		br_write_lock(vfsmount_lock);
1847
		touch_mnt_namespace(path->mnt->mnt_ns);
N
Nick Piggin 已提交
1848
		br_write_unlock(vfsmount_lock);
1849
	}
L
Linus Torvalds 已提交
1850 1851 1852
	return err;
}

R
Ram Pai 已提交
1853 1854 1855 1856 1857 1858 1859 1860 1861 1862
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;
}

1863
static int do_move_mount(struct path *path, char *old_name)
L
Linus Torvalds 已提交
1864
{
1865
	struct path old_path, parent_path;
L
Linus Torvalds 已提交
1866 1867 1868 1869 1870 1871
	struct vfsmount *p;
	int err = 0;
	if (!capable(CAP_SYS_ADMIN))
		return -EPERM;
	if (!old_name || !*old_name)
		return -EINVAL;
1872
	err = kern_path(old_name, LOOKUP_FOLLOW, &old_path);
L
Linus Torvalds 已提交
1873 1874 1875
	if (err)
		return err;

R
Ram Pai 已提交
1876
	down_write(&namespace_sem);
1877 1878 1879 1880
	err = follow_down(path, true);
	if (err < 0)
		goto out;

L
Linus Torvalds 已提交
1881
	err = -EINVAL;
1882
	if (!check_mnt(path->mnt) || !check_mnt(old_path.mnt))
L
Linus Torvalds 已提交
1883 1884 1885
		goto out;

	err = -ENOENT;
1886
	mutex_lock(&path->dentry->d_inode->i_mutex);
1887
	if (cant_mount(path->dentry))
L
Linus Torvalds 已提交
1888 1889
		goto out1;

1890
	if (d_unlinked(path->dentry))
R
Ram Pai 已提交
1891
		goto out1;
L
Linus Torvalds 已提交
1892 1893

	err = -EINVAL;
1894
	if (old_path.dentry != old_path.mnt->mnt_root)
R
Ram Pai 已提交
1895
		goto out1;
L
Linus Torvalds 已提交
1896

1897
	if (old_path.mnt == old_path.mnt->mnt_parent)
R
Ram Pai 已提交
1898
		goto out1;
L
Linus Torvalds 已提交
1899

1900 1901
	if (S_ISDIR(path->dentry->d_inode->i_mode) !=
	      S_ISDIR(old_path.dentry->d_inode->i_mode))
R
Ram Pai 已提交
1902 1903 1904 1905
		goto out1;
	/*
	 * Don't move a mount residing in a shared parent.
	 */
1906 1907
	if (old_path.mnt->mnt_parent &&
	    IS_MNT_SHARED(old_path.mnt->mnt_parent))
R
Ram Pai 已提交
1908
		goto out1;
R
Ram Pai 已提交
1909 1910 1911 1912
	/*
	 * Don't move a mount tree containing unbindable mounts to a destination
	 * mount which is shared.
	 */
1913 1914
	if (IS_MNT_SHARED(path->mnt) &&
	    tree_contains_unbindable(old_path.mnt))
R
Ram Pai 已提交
1915
		goto out1;
L
Linus Torvalds 已提交
1916
	err = -ELOOP;
1917 1918
	for (p = path->mnt; p->mnt_parent != p; p = p->mnt_parent)
		if (p == old_path.mnt)
R
Ram Pai 已提交
1919
			goto out1;
L
Linus Torvalds 已提交
1920

1921
	err = attach_recursive_mnt(old_path.mnt, path, &parent_path);
1922
	if (err)
R
Ram Pai 已提交
1923
		goto out1;
L
Linus Torvalds 已提交
1924 1925 1926

	/* if the mount is moved, it should no longer be expire
	 * automatically */
1927
	list_del_init(&old_path.mnt->mnt_expire);
L
Linus Torvalds 已提交
1928
out1:
1929
	mutex_unlock(&path->dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
1930
out:
R
Ram Pai 已提交
1931
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
1932
	if (!err)
1933
		path_put(&parent_path);
1934
	path_put(&old_path);
L
Linus Torvalds 已提交
1935 1936 1937
	return err;
}

1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype)
{
	int err;
	const char *subtype = strchr(fstype, '.');
	if (subtype) {
		subtype++;
		err = -EINVAL;
		if (!subtype[0])
			goto err;
	} else
		subtype = "";

	mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL);
	err = -ENOMEM;
	if (!mnt->mnt_sb->s_subtype)
		goto err;
	return mnt;

 err:
	mntput(mnt);
	return ERR_PTR(err);
}

struct vfsmount *
do_kern_mount(const char *fstype, int flags, const char *name, void *data)
{
	struct file_system_type *type = get_fs_type(fstype);
	struct vfsmount *mnt;
	if (!type)
		return ERR_PTR(-ENODEV);
	mnt = vfs_kern_mount(type, flags, name, data);
	if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE) &&
	    !mnt->mnt_sb->s_subtype)
		mnt = fs_set_subtype(mnt, fstype);
	put_filesystem(type);
	return mnt;
}
EXPORT_SYMBOL_GPL(do_kern_mount);

/*
 * add a mount into a namespace's mount tree
 */
static int do_add_mount(struct vfsmount *newmnt, struct path *path, int mnt_flags)
{
	int err;

	mnt_flags &= ~(MNT_SHARED | MNT_WRITE_HOLD | MNT_INTERNAL);

	down_write(&namespace_sem);
	/* Something was mounted here while we slept */
	err = follow_down(path, true);
	if (err < 0)
		goto unlock;

	err = -EINVAL;
	if (!(mnt_flags & MNT_SHRINKABLE) && !check_mnt(path->mnt))
		goto unlock;

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

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

	newmnt->mnt_flags = mnt_flags;
	err = graft_tree(newmnt, path);

unlock:
	up_write(&namespace_sem);
	return err;
}
A
Al Viro 已提交
2013

L
Linus Torvalds 已提交
2014 2015 2016 2017
/*
 * create a new mount for userspace and request it to be added into the
 * namespace's tree
 */
2018
static int do_new_mount(struct path *path, char *type, int flags,
L
Linus Torvalds 已提交
2019 2020 2021
			int mnt_flags, char *name, void *data)
{
	struct vfsmount *mnt;
2022
	int err;
L
Linus Torvalds 已提交
2023

2024
	if (!type)
L
Linus Torvalds 已提交
2025 2026 2027 2028 2029 2030 2031 2032 2033 2034
		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);

2035 2036 2037 2038
	err = do_add_mount(mnt, path, mnt_flags);
	if (err)
		mntput(mnt);
	return err;
L
Linus Torvalds 已提交
2039 2040
}

2041 2042 2043 2044 2045 2046 2047 2048 2049 2050
int finish_automount(struct vfsmount *m, struct path *path)
{
	int err;
	/* The new mount record should have at least 2 refs to prevent it being
	 * expired before we get a chance to add it
	 */
	BUG_ON(mnt_get_count(m) < 2);

	if (m->mnt_sb == path->mnt->mnt_sb &&
	    m->mnt_root == path->dentry) {
A
Al Viro 已提交
2051 2052
		err = -ELOOP;
		goto fail;
2053 2054 2055
	}

	err = do_add_mount(m, path, path->mnt->mnt_flags | MNT_SHRINKABLE);
A
Al Viro 已提交
2056 2057 2058 2059 2060 2061 2062 2063 2064 2065
	if (!err)
		return 0;
fail:
	/* remove m from any expiration list it may be on */
	if (!list_empty(&m->mnt_expire)) {
		down_write(&namespace_sem);
		br_write_lock(vfsmount_lock);
		list_del_init(&m->mnt_expire);
		br_write_unlock(vfsmount_lock);
		up_write(&namespace_sem);
2066
	}
A
Al Viro 已提交
2067 2068
	mntput(m);
	mntput(m);
2069 2070 2071
	return err;
}

2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088
/**
 * mnt_set_expiry - Put a mount on an expiration list
 * @mnt: The mount to list.
 * @expiry_list: The list to add the mount to.
 */
void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list)
{
	down_write(&namespace_sem);
	br_write_lock(vfsmount_lock);

	list_add_tail(&mnt->mnt_expire, expiry_list);

	br_write_unlock(vfsmount_lock);
	up_write(&namespace_sem);
}
EXPORT_SYMBOL(mnt_set_expiry);

L
Linus Torvalds 已提交
2089 2090 2091 2092 2093 2094 2095 2096 2097
/*
 * 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);
2098
	LIST_HEAD(umounts);
L
Linus Torvalds 已提交
2099 2100 2101 2102

	if (list_empty(mounts))
		return;

2103
	down_write(&namespace_sem);
N
Nick Piggin 已提交
2104
	br_write_lock(vfsmount_lock);
L
Linus Torvalds 已提交
2105 2106 2107 2108 2109 2110 2111

	/* 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())
	 */
2112
	list_for_each_entry_safe(mnt, next, mounts, mnt_expire) {
L
Linus Torvalds 已提交
2113
		if (!xchg(&mnt->mnt_expiry_mark, 1) ||
2114
			propagate_mount_busy(mnt, 1))
L
Linus Torvalds 已提交
2115
			continue;
2116
		list_move(&mnt->mnt_expire, &graveyard);
L
Linus Torvalds 已提交
2117
	}
2118 2119 2120 2121 2122
	while (!list_empty(&graveyard)) {
		mnt = list_first_entry(&graveyard, struct vfsmount, mnt_expire);
		touch_mnt_namespace(mnt->mnt_ns);
		umount_tree(mnt, 1, &umounts);
	}
N
Nick Piggin 已提交
2123
	br_write_unlock(vfsmount_lock);
2124 2125 2126
	up_write(&namespace_sem);

	release_mounts(&umounts);
T
Trond Myklebust 已提交
2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151
}

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))
L
Linus Torvalds 已提交
2152
			continue;
T
Trond Myklebust 已提交
2153 2154 2155 2156 2157 2158 2159
		/*
		 * Descend a level if the d_mounts list is non-empty.
		 */
		if (!list_empty(&mnt->mnt_mounts)) {
			this_parent = mnt;
			goto repeat;
		}
L
Linus Torvalds 已提交
2160

T
Trond Myklebust 已提交
2161 2162 2163 2164
		if (!propagate_mount_busy(mnt, 1)) {
			list_move_tail(&mnt->mnt_expire, graveyard);
			found++;
		}
L
Linus Torvalds 已提交
2165
	}
T
Trond Myklebust 已提交
2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179
	/*
	 * 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
N
Nick Piggin 已提交
2180 2181
 *
 * vfsmount_lock must be held for write
T
Trond Myklebust 已提交
2182
 */
2183
static void shrink_submounts(struct vfsmount *mnt, struct list_head *umounts)
T
Trond Myklebust 已提交
2184 2185
{
	LIST_HEAD(graveyard);
2186
	struct vfsmount *m;
T
Trond Myklebust 已提交
2187 2188

	/* extract submounts of 'mountpoint' from the expiration list */
2189
	while (select_submounts(mnt, &graveyard)) {
2190
		while (!list_empty(&graveyard)) {
2191
			m = list_first_entry(&graveyard, struct vfsmount,
2192
						mnt_expire);
E
Eric W. Biederman 已提交
2193 2194
			touch_mnt_namespace(m->mnt_ns);
			umount_tree(m, 1, umounts);
2195 2196
		}
	}
L
Linus Torvalds 已提交
2197 2198 2199 2200 2201 2202 2203 2204
}

/*
 * 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
Ram Pai 已提交
2205 2206
static long exact_copy_from_user(void *to, const void __user * from,
				 unsigned long n)
L
Linus Torvalds 已提交
2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226
{
	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
2227
int copy_mount_options(const void __user * data, unsigned long *where)
L
Linus Torvalds 已提交
2228 2229 2230 2231
{
	int i;
	unsigned long page;
	unsigned long size;
R
Ram Pai 已提交
2232

L
Linus Torvalds 已提交
2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250
	*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
2251
		free_page(page);
L
Linus Torvalds 已提交
2252 2253 2254 2255 2256 2257 2258 2259
		return -EFAULT;
	}
	if (i != PAGE_SIZE)
		memset((char *)page + i, 0, PAGE_SIZE - i);
	*where = page;
	return 0;
}

2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276
int copy_mount_string(const void __user *data, char **where)
{
	char *tmp;

	if (!data) {
		*where = NULL;
		return 0;
	}

	tmp = strndup_user(data, PAGE_SIZE);
	if (IS_ERR(tmp))
		return PTR_ERR(tmp);

	*where = tmp;
	return 0;
}

L
Linus Torvalds 已提交
2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290
/*
 * 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
2291
long do_mount(char *dev_name, char *dir_name, char *type_page,
L
Linus Torvalds 已提交
2292 2293
		  unsigned long flags, void *data_page)
{
2294
	struct path path;
L
Linus Torvalds 已提交
2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309
	int retval = 0;
	int mnt_flags = 0;

	/* Discard magic */
	if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
		flags &= ~MS_MGC_MSK;

	/* Basic sanity checks */

	if (!dir_name || !*dir_name || !memchr(dir_name, 0, PAGE_SIZE))
		return -EINVAL;

	if (data_page)
		((char *)data_page)[PAGE_SIZE - 1] = 0;

2310 2311 2312 2313 2314 2315 2316 2317 2318 2319
	/* ... and get the mountpoint */
	retval = kern_path(dir_name, LOOKUP_FOLLOW, &path);
	if (retval)
		return retval;

	retval = security_sb_mount(dev_name, &path,
				   type_page, flags, data_page);
	if (retval)
		goto dput_out;

2320 2321 2322
	/* Default to relatime unless overriden */
	if (!(flags & MS_NOATIME))
		mnt_flags |= MNT_RELATIME;
M
Matthew Garrett 已提交
2323

L
Linus Torvalds 已提交
2324 2325 2326 2327 2328 2329 2330
	/* 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;
2331 2332 2333 2334
	if (flags & MS_NOATIME)
		mnt_flags |= MNT_NOATIME;
	if (flags & MS_NODIRATIME)
		mnt_flags |= MNT_NODIRATIME;
M
Matthew Garrett 已提交
2335 2336
	if (flags & MS_STRICTATIME)
		mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME);
2337 2338
	if (flags & MS_RDONLY)
		mnt_flags |= MNT_READONLY;
2339

A
Al Viro 已提交
2340
	flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
M
Matthew Garrett 已提交
2341 2342
		   MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
		   MS_STRICTATIME);
L
Linus Torvalds 已提交
2343 2344

	if (flags & MS_REMOUNT)
2345
		retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
L
Linus Torvalds 已提交
2346 2347
				    data_page);
	else if (flags & MS_BIND)
2348
		retval = do_loopback(&path, dev_name, flags & MS_REC);
R
Ram Pai 已提交
2349
	else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
2350
		retval = do_change_type(&path, flags);
L
Linus Torvalds 已提交
2351
	else if (flags & MS_MOVE)
2352
		retval = do_move_mount(&path, dev_name);
L
Linus Torvalds 已提交
2353
	else
2354
		retval = do_new_mount(&path, type_page, flags, mnt_flags,
L
Linus Torvalds 已提交
2355 2356
				      dev_name, data_page);
dput_out:
2357
	path_put(&path);
L
Linus Torvalds 已提交
2358 2359 2360
	return retval;
}

2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375
static struct mnt_namespace *alloc_mnt_ns(void)
{
	struct mnt_namespace *new_ns;

	new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL);
	if (!new_ns)
		return ERR_PTR(-ENOMEM);
	atomic_set(&new_ns->count, 1);
	new_ns->root = NULL;
	INIT_LIST_HEAD(&new_ns->list);
	init_waitqueue_head(&new_ns->poll);
	new_ns->event = 0;
	return new_ns;
}

A
Al Viro 已提交
2376 2377
void mnt_make_longterm(struct vfsmount *mnt)
{
2378
	__mnt_make_longterm(mnt);
A
Al Viro 已提交
2379 2380 2381 2382
}

void mnt_make_shortterm(struct vfsmount *mnt)
{
2383
#ifdef CONFIG_SMP
A
Al Viro 已提交
2384 2385 2386 2387 2388
	if (atomic_add_unless(&mnt->mnt_longterm, -1, 1))
		return;
	br_write_lock(vfsmount_lock);
	atomic_dec(&mnt->mnt_longterm);
	br_write_unlock(vfsmount_lock);
2389
#endif
A
Al Viro 已提交
2390 2391
}

2392 2393 2394 2395
/*
 * Allocate a new namespace structure and populate it with contents
 * copied from the namespace of the passed in task structure.
 */
2396
static struct mnt_namespace *dup_mnt_ns(struct mnt_namespace *mnt_ns,
2397
		struct fs_struct *fs)
L
Linus Torvalds 已提交
2398
{
2399
	struct mnt_namespace *new_ns;
A
Al Viro 已提交
2400
	struct vfsmount *rootmnt = NULL, *pwdmnt = NULL;
L
Linus Torvalds 已提交
2401 2402
	struct vfsmount *p, *q;

2403 2404 2405
	new_ns = alloc_mnt_ns();
	if (IS_ERR(new_ns))
		return new_ns;
L
Linus Torvalds 已提交
2406

R
Ram Pai 已提交
2407
	down_write(&namespace_sem);
L
Linus Torvalds 已提交
2408
	/* First pass: copy the tree topology */
2409
	new_ns->root = copy_tree(mnt_ns->root, mnt_ns->root->mnt_root,
R
Ram Pai 已提交
2410
					CL_COPY_ALL | CL_EXPIRE);
L
Linus Torvalds 已提交
2411
	if (!new_ns->root) {
R
Ram Pai 已提交
2412
		up_write(&namespace_sem);
L
Linus Torvalds 已提交
2413
		kfree(new_ns);
2414
		return ERR_PTR(-ENOMEM);
L
Linus Torvalds 已提交
2415
	}
N
Nick Piggin 已提交
2416
	br_write_lock(vfsmount_lock);
L
Linus Torvalds 已提交
2417
	list_add_tail(&new_ns->list, &new_ns->root->mnt_list);
N
Nick Piggin 已提交
2418
	br_write_unlock(vfsmount_lock);
L
Linus Torvalds 已提交
2419 2420 2421 2422 2423 2424

	/*
	 * 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.
	 */
2425
	p = mnt_ns->root;
L
Linus Torvalds 已提交
2426 2427
	q = new_ns->root;
	while (p) {
2428
		q->mnt_ns = new_ns;
2429
		__mnt_make_longterm(q);
L
Linus Torvalds 已提交
2430
		if (fs) {
J
Jan Blunck 已提交
2431
			if (p == fs->root.mnt) {
A
Al Viro 已提交
2432
				fs->root.mnt = mntget(q);
2433
				__mnt_make_longterm(q);
A
Al Viro 已提交
2434
				mnt_make_shortterm(p);
L
Linus Torvalds 已提交
2435 2436
				rootmnt = p;
			}
J
Jan Blunck 已提交
2437
			if (p == fs->pwd.mnt) {
A
Al Viro 已提交
2438
				fs->pwd.mnt = mntget(q);
2439
				__mnt_make_longterm(q);
A
Al Viro 已提交
2440
				mnt_make_shortterm(p);
L
Linus Torvalds 已提交
2441 2442 2443
				pwdmnt = p;
			}
		}
2444
		p = next_mnt(p, mnt_ns->root);
L
Linus Torvalds 已提交
2445 2446
		q = next_mnt(q, new_ns->root);
	}
R
Ram Pai 已提交
2447
	up_write(&namespace_sem);
L
Linus Torvalds 已提交
2448 2449

	if (rootmnt)
A
Al Viro 已提交
2450
		mntput(rootmnt);
L
Linus Torvalds 已提交
2451
	if (pwdmnt)
A
Al Viro 已提交
2452
		mntput(pwdmnt);
L
Linus Torvalds 已提交
2453

2454 2455 2456
	return new_ns;
}

2457
struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
2458
		struct fs_struct *new_fs)
2459
{
2460
	struct mnt_namespace *new_ns;
2461

2462
	BUG_ON(!ns);
2463
	get_mnt_ns(ns);
2464 2465

	if (!(flags & CLONE_NEWNS))
2466
		return ns;
2467

2468
	new_ns = dup_mnt_ns(ns, new_fs);
2469

2470
	put_mnt_ns(ns);
2471
	return new_ns;
L
Linus Torvalds 已提交
2472 2473
}

2474 2475 2476 2477
/**
 * create_mnt_ns - creates a private namespace and adds a root filesystem
 * @mnt: pointer to the new root filesystem mountpoint
 */
2478
struct mnt_namespace *create_mnt_ns(struct vfsmount *mnt)
2479 2480 2481 2482 2483 2484
{
	struct mnt_namespace *new_ns;

	new_ns = alloc_mnt_ns();
	if (!IS_ERR(new_ns)) {
		mnt->mnt_ns = new_ns;
2485
		__mnt_make_longterm(mnt);
2486 2487 2488 2489 2490
		new_ns->root = mnt;
		list_add(&new_ns->list, &new_ns->root->mnt_list);
	}
	return new_ns;
}
2491
EXPORT_SYMBOL(create_mnt_ns);
2492

2493 2494
SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name,
		char __user *, type, unsigned long, flags, void __user *, data)
L
Linus Torvalds 已提交
2495
{
2496 2497 2498 2499
	int ret;
	char *kernel_type;
	char *kernel_dir;
	char *kernel_dev;
L
Linus Torvalds 已提交
2500 2501
	unsigned long data_page;

2502 2503 2504
	ret = copy_mount_string(type, &kernel_type);
	if (ret < 0)
		goto out_type;
L
Linus Torvalds 已提交
2505

2506 2507 2508 2509 2510
	kernel_dir = getname(dir_name);
	if (IS_ERR(kernel_dir)) {
		ret = PTR_ERR(kernel_dir);
		goto out_dir;
	}
L
Linus Torvalds 已提交
2511

2512 2513 2514
	ret = copy_mount_string(dev_name, &kernel_dev);
	if (ret < 0)
		goto out_dev;
L
Linus Torvalds 已提交
2515

2516 2517 2518
	ret = copy_mount_options(data, &data_page);
	if (ret < 0)
		goto out_data;
L
Linus Torvalds 已提交
2519

2520 2521
	ret = do_mount(kernel_dev, kernel_dir, kernel_type, flags,
		(void *) data_page);
L
Linus Torvalds 已提交
2522

2523 2524 2525 2526 2527 2528 2529 2530 2531
	free_page(data_page);
out_data:
	kfree(kernel_dev);
out_dev:
	putname(kernel_dir);
out_dir:
	kfree(kernel_type);
out_type:
	return ret;
L
Linus Torvalds 已提交
2532 2533 2534 2535 2536 2537 2538 2539 2540 2541 2542 2543 2544 2545 2546
}

/*
 * 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
2547 2548 2549 2550
 * 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
2551 2552 2553 2554 2555 2556 2557 2558
 * 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.
 */
2559 2560
SYSCALL_DEFINE2(pivot_root, const char __user *, new_root,
		const char __user *, put_old)
L
Linus Torvalds 已提交
2561 2562
{
	struct vfsmount *tmp;
2563
	struct path new, old, parent_path, root_parent, root;
L
Linus Torvalds 已提交
2564 2565 2566 2567 2568
	int error;

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

2569
	error = user_path_dir(new_root, &new);
L
Linus Torvalds 已提交
2570 2571 2572
	if (error)
		goto out0;

2573
	error = user_path_dir(put_old, &old);
L
Linus Torvalds 已提交
2574 2575 2576
	if (error)
		goto out1;

2577
	error = security_sb_pivotroot(&old, &new);
L
Linus Torvalds 已提交
2578
	if (error) {
2579
		path_put(&old);
L
Linus Torvalds 已提交
2580 2581 2582
		goto out1;
	}

2583
	get_fs_root(current->fs, &root);
R
Ram Pai 已提交
2584
	down_write(&namespace_sem);
2585
	mutex_lock(&old.dentry->d_inode->i_mutex);
L
Linus Torvalds 已提交
2586
	error = -EINVAL;
2587 2588
	if (IS_MNT_SHARED(old.mnt) ||
		IS_MNT_SHARED(new.mnt->mnt_parent) ||
2589
		IS_MNT_SHARED(root.mnt->mnt_parent))
R
Ram Pai 已提交
2590
		goto out2;
A
Al Viro 已提交
2591
	if (!check_mnt(root.mnt) || !check_mnt(new.mnt))
L
Linus Torvalds 已提交
2592 2593
		goto out2;
	error = -ENOENT;
2594
	if (cant_mount(old.dentry))
L
Linus Torvalds 已提交
2595
		goto out2;
2596
	if (d_unlinked(new.dentry))
L
Linus Torvalds 已提交
2597
		goto out2;
2598
	if (d_unlinked(old.dentry))
L
Linus Torvalds 已提交
2599 2600
		goto out2;
	error = -EBUSY;
2601 2602
	if (new.mnt == root.mnt ||
	    old.mnt == root.mnt)
L
Linus Torvalds 已提交
2603 2604
		goto out2; /* loop, on the same file system  */
	error = -EINVAL;
2605
	if (root.mnt->mnt_root != root.dentry)
L
Linus Torvalds 已提交
2606
		goto out2; /* not a mountpoint */
2607
	if (root.mnt->mnt_parent == root.mnt)
2608
		goto out2; /* not attached */
2609
	if (new.mnt->mnt_root != new.dentry)
L
Linus Torvalds 已提交
2610
		goto out2; /* not a mountpoint */
2611
	if (new.mnt->mnt_parent == new.mnt)
2612
		goto out2; /* not attached */
2613
	/* make sure we can reach put_old from new_root */
2614 2615
	tmp = old.mnt;
	if (tmp != new.mnt) {
L
Linus Torvalds 已提交
2616 2617
		for (;;) {
			if (tmp->mnt_parent == tmp)
A
Al Viro 已提交
2618
				goto out2; /* already mounted on put_old */
2619
			if (tmp->mnt_parent == new.mnt)
L
Linus Torvalds 已提交
2620 2621 2622
				break;
			tmp = tmp->mnt_parent;
		}
2623
		if (!is_subdir(tmp->mnt_mountpoint, new.dentry))
A
Al Viro 已提交
2624
			goto out2;
2625
	} else if (!is_subdir(old.dentry, new.dentry))
A
Al Viro 已提交
2626 2627
		goto out2;
	br_write_lock(vfsmount_lock);
2628
	detach_mnt(new.mnt, &parent_path);
2629
	detach_mnt(root.mnt, &root_parent);
2630
	/* mount old root on put_old */
2631
	attach_mnt(root.mnt, &old);
2632
	/* mount new_root on / */
2633
	attach_mnt(new.mnt, &root_parent);
2634
	touch_mnt_namespace(current->nsproxy->mnt_ns);
N
Nick Piggin 已提交
2635
	br_write_unlock(vfsmount_lock);
2636
	chroot_fs_refs(&root, &new);
N
Nick Piggin 已提交
2637

L
Linus Torvalds 已提交
2638
	error = 0;
2639 2640
	path_put(&root_parent);
	path_put(&parent_path);
L
Linus Torvalds 已提交
2641
out2:
2642
	mutex_unlock(&old.dentry->d_inode->i_mutex);
R
Ram Pai 已提交
2643
	up_write(&namespace_sem);
2644
	path_put(&root);
2645
	path_put(&old);
L
Linus Torvalds 已提交
2646
out1:
2647
	path_put(&new);
L
Linus Torvalds 已提交
2648 2649 2650 2651 2652 2653 2654
out0:
	return error;
}

static void __init init_mount_tree(void)
{
	struct vfsmount *mnt;
2655
	struct mnt_namespace *ns;
2656
	struct path root;
L
Linus Torvalds 已提交
2657 2658 2659 2660

	mnt = do_kern_mount("rootfs", 0, "rootfs", NULL);
	if (IS_ERR(mnt))
		panic("Can't create rootfs");
N
Nick Piggin 已提交
2661

2662 2663
	ns = create_mnt_ns(mnt);
	if (IS_ERR(ns))
L
Linus Torvalds 已提交
2664
		panic("Can't allocate initial namespace");
2665 2666 2667 2668

	init_task.nsproxy->mnt_ns = ns;
	get_mnt_ns(ns);

2669 2670 2671 2672 2673
	root.mnt = ns->root;
	root.dentry = ns->root->mnt_root;

	set_fs_pwd(current->fs, &root);
	set_fs_root(current->fs, &root);
L
Linus Torvalds 已提交
2674 2675
}

2676
void __init mnt_init(void)
L
Linus Torvalds 已提交
2677
{
E
Eric Dumazet 已提交
2678
	unsigned u;
2679
	int err;
L
Linus Torvalds 已提交
2680

R
Ram Pai 已提交
2681 2682
	init_rwsem(&namespace_sem);

L
Linus Torvalds 已提交
2683
	mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct vfsmount),
2684
			0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
L
Linus Torvalds 已提交
2685

R
Ram Pai 已提交
2686
	mount_hashtable = (struct list_head *)__get_free_page(GFP_ATOMIC);
L
Linus Torvalds 已提交
2687 2688 2689 2690

	if (!mount_hashtable)
		panic("Failed to allocate mount hash table\n");

E
Eric Dumazet 已提交
2691 2692 2693 2694
	printk("Mount-cache hash table entries: %lu\n", HASH_SIZE);

	for (u = 0; u < HASH_SIZE; u++)
		INIT_LIST_HEAD(&mount_hashtable[u]);
L
Linus Torvalds 已提交
2695

N
Nick Piggin 已提交
2696 2697
	br_lock_init(vfsmount_lock);

2698 2699 2700
	err = sysfs_init();
	if (err)
		printk(KERN_WARNING "%s: sysfs_init error: %d\n",
2701
			__func__, err);
2702 2703
	fs_kobj = kobject_create_and_add("fs", NULL);
	if (!fs_kobj)
2704
		printk(KERN_WARNING "%s: kobj create error\n", __func__);
L
Linus Torvalds 已提交
2705 2706 2707 2708
	init_rootfs();
	init_mount_tree();
}

2709
void put_mnt_ns(struct mnt_namespace *ns)
L
Linus Torvalds 已提交
2710
{
R
Ram Pai 已提交
2711
	LIST_HEAD(umount_list);
2712

2713
	if (!atomic_dec_and_test(&ns->count))
2714
		return;
R
Ram Pai 已提交
2715
	down_write(&namespace_sem);
N
Nick Piggin 已提交
2716
	br_write_lock(vfsmount_lock);
2717
	umount_tree(ns->root, 0, &umount_list);
N
Nick Piggin 已提交
2718
	br_write_unlock(vfsmount_lock);
R
Ram Pai 已提交
2719
	up_write(&namespace_sem);
R
Ram Pai 已提交
2720
	release_mounts(&umount_list);
2721
	kfree(ns);
L
Linus Torvalds 已提交
2722
}
2723
EXPORT_SYMBOL(put_mnt_ns);
2724 2725 2726 2727 2728 2729

struct vfsmount *kern_mount_data(struct file_system_type *type, void *data)
{
	return vfs_kern_mount(type, MS_KERNMOUNT, type->name, data);
}
EXPORT_SYMBOL_GPL(kern_mount_data);