super.c 26.0 KB
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/*
 *
 * Copyright (C) 2011 Novell Inc.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 */

#include <linux/fs.h>
#include <linux/namei.h>
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#include <linux/pagemap.h>
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#include <linux/xattr.h>
#include <linux/security.h>
#include <linux/mount.h>
#include <linux/slab.h>
#include <linux/parser.h>
#include <linux/module.h>
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#include <linux/pagemap.h>
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#include <linux/sched.h>
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#include <linux/statfs.h>
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#include <linux/seq_file.h>
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#include "overlayfs.h"

MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
MODULE_DESCRIPTION("Overlay filesystem");
MODULE_LICENSE("GPL");

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struct ovl_config {
	char *lowerdir;
	char *upperdir;
	char *workdir;
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	bool default_permissions;
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};

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/* private information held for overlayfs's superblock */
struct ovl_fs {
	struct vfsmount *upper_mnt;
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	unsigned numlower;
	struct vfsmount **lower_mnt;
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	struct dentry *workdir;
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	long lower_namelen;
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	/* pathnames of lower and upper dirs, for show_options */
	struct ovl_config config;
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	/* creds of process who forced instantiation of super block */
	const struct cred *creator_cred;
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};

struct ovl_dir_cache;

/* private information held for every overlayfs dentry */
struct ovl_entry {
	struct dentry *__upperdentry;
	struct ovl_dir_cache *cache;
	union {
		struct {
			u64 version;
			bool opaque;
		};
		struct rcu_head rcu;
	};
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	unsigned numlower;
	struct path lowerstack[];
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};

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#define OVL_MAX_STACK 500

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static struct dentry *__ovl_dentry_lower(struct ovl_entry *oe)
{
	return oe->numlower ? oe->lowerstack[0].dentry : NULL;
}
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enum ovl_path_type ovl_path_type(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;
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	enum ovl_path_type type = 0;
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	if (oe->__upperdentry) {
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		type = __OVL_PATH_UPPER;

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		/*
		 * Non-dir dentry can hold lower dentry from previous
		 * location. Its purity depends only on opaque flag.
		 */
		if (oe->numlower && S_ISDIR(dentry->d_inode->i_mode))
			type |= __OVL_PATH_MERGE;
		else if (!oe->opaque)
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			type |= __OVL_PATH_PURE;
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	} else {
		if (oe->numlower > 1)
			type |= __OVL_PATH_MERGE;
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	}
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	return type;
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}

static struct dentry *ovl_upperdentry_dereference(struct ovl_entry *oe)
{
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	return lockless_dereference(oe->__upperdentry);
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}

void ovl_path_upper(struct dentry *dentry, struct path *path)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	struct ovl_entry *oe = dentry->d_fsdata;

	path->mnt = ofs->upper_mnt;
	path->dentry = ovl_upperdentry_dereference(oe);
}

enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
{
	enum ovl_path_type type = ovl_path_type(dentry);

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	if (!OVL_TYPE_UPPER(type))
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		ovl_path_lower(dentry, path);
	else
		ovl_path_upper(dentry, path);

	return type;
}

struct dentry *ovl_dentry_upper(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	return ovl_upperdentry_dereference(oe);
}

struct dentry *ovl_dentry_lower(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

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	return __ovl_dentry_lower(oe);
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}

struct dentry *ovl_dentry_real(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	struct dentry *realdentry;

	realdentry = ovl_upperdentry_dereference(oe);
	if (!realdentry)
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		realdentry = __ovl_dentry_lower(oe);
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	return realdentry;
}

struct dentry *ovl_entry_real(struct ovl_entry *oe, bool *is_upper)
{
	struct dentry *realdentry;

	realdentry = ovl_upperdentry_dereference(oe);
	if (realdentry) {
		*is_upper = true;
	} else {
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		realdentry = __ovl_dentry_lower(oe);
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		*is_upper = false;
	}
	return realdentry;
}

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struct vfsmount *ovl_entry_mnt_real(struct ovl_entry *oe, struct inode *inode,
				    bool is_upper)
{
	if (is_upper) {
		struct ovl_fs *ofs = inode->i_sb->s_fs_info;

		return ofs->upper_mnt;
	} else {
		return oe->numlower ? oe->lowerstack[0].mnt : NULL;
	}
}

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struct ovl_dir_cache *ovl_dir_cache(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	return oe->cache;
}

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bool ovl_is_default_permissions(struct inode *inode)
{
	struct ovl_fs *ofs = inode->i_sb->s_fs_info;

	return ofs->config.default_permissions;
}

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void ovl_set_dir_cache(struct dentry *dentry, struct ovl_dir_cache *cache)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	oe->cache = cache;
}

void ovl_path_lower(struct dentry *dentry, struct path *path)
{
	struct ovl_entry *oe = dentry->d_fsdata;

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	*path = oe->numlower ? oe->lowerstack[0] : (struct path) { NULL, NULL };
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}

int ovl_want_write(struct dentry *dentry)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	return mnt_want_write(ofs->upper_mnt);
}

void ovl_drop_write(struct dentry *dentry)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	mnt_drop_write(ofs->upper_mnt);
}

struct dentry *ovl_workdir(struct dentry *dentry)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	return ofs->workdir;
}

bool ovl_dentry_is_opaque(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	return oe->opaque;
}

void ovl_dentry_set_opaque(struct dentry *dentry, bool opaque)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	oe->opaque = opaque;
}

void ovl_dentry_update(struct dentry *dentry, struct dentry *upperdentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

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	WARN_ON(!inode_is_locked(upperdentry->d_parent->d_inode));
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	WARN_ON(oe->__upperdentry);
	BUG_ON(!upperdentry->d_inode);
	/*
	 * Make sure upperdentry is consistent before making it visible to
	 * ovl_upperdentry_dereference().
	 */
	smp_wmb();
	oe->__upperdentry = upperdentry;
}

void ovl_dentry_version_inc(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

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	WARN_ON(!inode_is_locked(dentry->d_inode));
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	oe->version++;
}

u64 ovl_dentry_version_get(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

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	WARN_ON(!inode_is_locked(dentry->d_inode));
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	return oe->version;
}

bool ovl_is_whiteout(struct dentry *dentry)
{
	struct inode *inode = dentry->d_inode;

	return inode && IS_WHITEOUT(inode);
}

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const struct cred *ovl_override_creds(struct super_block *sb)
{
	struct ovl_fs *ofs = sb->s_fs_info;

	return override_creds(ofs->creator_cred);
}

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static bool ovl_is_opaquedir(struct dentry *dentry)
{
	int res;
	char val;
	struct inode *inode = dentry->d_inode;

	if (!S_ISDIR(inode->i_mode) || !inode->i_op->getxattr)
		return false;

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	res = inode->i_op->getxattr(dentry, inode, OVL_XATTR_OPAQUE, &val, 1);
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	if (res == 1 && val == 'y')
		return true;

	return false;
}

static void ovl_dentry_release(struct dentry *dentry)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	if (oe) {
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		unsigned int i;

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		dput(oe->__upperdentry);
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		for (i = 0; i < oe->numlower; i++)
			dput(oe->lowerstack[i].dentry);
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		kfree_rcu(oe, rcu);
	}
}

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static struct dentry *ovl_d_real(struct dentry *dentry, struct inode *inode)
{
	struct dentry *real;

	if (d_is_dir(dentry)) {
		if (!inode || inode == d_inode(dentry))
			return dentry;
		goto bug;
	}

	real = ovl_dentry_upper(dentry);
	if (real && (!inode || inode == d_inode(real)))
		return real;

	real = ovl_dentry_lower(dentry);
	if (!real)
		goto bug;

	if (!inode || inode == d_inode(real))
		return real;

	/* Handle recursion */
	if (real->d_flags & DCACHE_OP_REAL)
		return real->d_op->d_real(real, inode);

bug:
	WARN(1, "ovl_d_real(%pd4, %s:%lu\n): real dentry not found\n", dentry,
	     inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
	return dentry;
}

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static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	unsigned int i;
	int ret = 1;

	for (i = 0; i < oe->numlower; i++) {
		struct dentry *d = oe->lowerstack[i].dentry;

		if (d->d_flags & DCACHE_OP_REVALIDATE) {
			ret = d->d_op->d_revalidate(d, flags);
			if (ret < 0)
				return ret;
			if (!ret) {
				if (!(flags & LOOKUP_RCU))
					d_invalidate(d);
				return -ESTALE;
			}
		}
	}
	return 1;
}

static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
{
	struct ovl_entry *oe = dentry->d_fsdata;
	unsigned int i;
	int ret = 1;

	for (i = 0; i < oe->numlower; i++) {
		struct dentry *d = oe->lowerstack[i].dentry;

		if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
			ret = d->d_op->d_weak_revalidate(d, flags);
			if (ret <= 0)
				break;
		}
	}
	return ret;
}

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static const struct dentry_operations ovl_dentry_operations = {
	.d_release = ovl_dentry_release,
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	.d_select_inode = ovl_d_select_inode,
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	.d_real = ovl_d_real,
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};

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static const struct dentry_operations ovl_reval_dentry_operations = {
	.d_release = ovl_dentry_release,
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	.d_select_inode = ovl_d_select_inode,
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	.d_real = ovl_d_real,
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	.d_revalidate = ovl_dentry_revalidate,
	.d_weak_revalidate = ovl_dentry_weak_revalidate,
};

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static struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
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{
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	size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
	struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);

	if (oe)
		oe->numlower = numlower;

	return oe;
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}

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static bool ovl_dentry_remote(struct dentry *dentry)
{
	return dentry->d_flags &
		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
}

static bool ovl_dentry_weird(struct dentry *dentry)
{
	return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
				  DCACHE_MANAGE_TRANSIT |
				  DCACHE_OP_HASH |
				  DCACHE_OP_COMPARE);
}

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static inline struct dentry *ovl_lookup_real(struct dentry *dir,
					     struct qstr *name)
{
	struct dentry *dentry;

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	dentry = lookup_hash(name, dir);
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	if (IS_ERR(dentry)) {
		if (PTR_ERR(dentry) == -ENOENT)
			dentry = NULL;
	} else if (!dentry->d_inode) {
		dput(dentry);
		dentry = NULL;
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	} else if (ovl_dentry_weird(dentry)) {
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		dput(dentry);
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		/* Don't support traversing automounts and other weirdness */
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		dentry = ERR_PTR(-EREMOTE);
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	}
	return dentry;
}

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/*
 * Returns next layer in stack starting from top.
 * Returns -1 if this is the last layer.
 */
int ovl_path_next(int idx, struct dentry *dentry, struct path *path)
{
	struct ovl_entry *oe = dentry->d_fsdata;

	BUG_ON(idx < 0);
	if (idx == 0) {
		ovl_path_upper(dentry, path);
		if (path->dentry)
			return oe->numlower ? 1 : -1;
		idx++;
	}
	BUG_ON(idx > oe->numlower);
	*path = oe->lowerstack[idx - 1];

	return (idx < oe->numlower) ? idx + 1 : -1;
}

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struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
			  unsigned int flags)
{
	struct ovl_entry *oe;
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	struct ovl_entry *poe = dentry->d_parent->d_fsdata;
	struct path *stack = NULL;
	struct dentry *upperdir, *upperdentry = NULL;
	unsigned int ctr = 0;
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	struct inode *inode = NULL;
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	bool upperopaque = false;
	struct dentry *this, *prev = NULL;
	unsigned int i;
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	int err;

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	upperdir = ovl_upperdentry_dereference(poe);
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	if (upperdir) {
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		this = ovl_lookup_real(upperdir, &dentry->d_name);
		err = PTR_ERR(this);
		if (IS_ERR(this))
			goto out;

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		if (this) {
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			if (unlikely(ovl_dentry_remote(this))) {
				dput(this);
				err = -EREMOTE;
				goto out;
			}
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			if (ovl_is_whiteout(this)) {
				dput(this);
				this = NULL;
				upperopaque = true;
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			} else if (poe->numlower && ovl_is_opaquedir(this)) {
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				upperopaque = true;
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			}
		}
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		upperdentry = prev = this;
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	}
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	if (!upperopaque && poe->numlower) {
		err = -ENOMEM;
		stack = kcalloc(poe->numlower, sizeof(struct path), GFP_KERNEL);
		if (!stack)
			goto out_put_upper;
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	}

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	for (i = 0; !upperopaque && i < poe->numlower; i++) {
		bool opaque = false;
		struct path lowerpath = poe->lowerstack[i];

		this = ovl_lookup_real(lowerpath.dentry, &dentry->d_name);
		err = PTR_ERR(this);
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		if (IS_ERR(this)) {
			/*
			 * If it's positive, then treat ENAMETOOLONG as ENOENT.
			 */
			if (err == -ENAMETOOLONG && (upperdentry || ctr))
				continue;
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			goto out_put;
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		}
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		if (!this)
			continue;
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		if (ovl_is_whiteout(this)) {
			dput(this);
			break;
		}
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		/*
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		 * Only makes sense to check opaque dir if this is not the
		 * lowermost layer.
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		 */
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		if (i < poe->numlower - 1 && ovl_is_opaquedir(this))
			opaque = true;
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		if (prev && (!S_ISDIR(prev->d_inode->i_mode) ||
			     !S_ISDIR(this->d_inode->i_mode))) {
			/*
			 * FIXME: check for upper-opaqueness maybe better done
			 * in remove code.
			 */
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			if (prev == upperdentry)
				upperopaque = true;
			dput(this);
			break;
		}
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		/*
		 * If this is a non-directory then stop here.
		 */
		if (!S_ISDIR(this->d_inode->i_mode))
			opaque = true;

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		stack[ctr].dentry = this;
		stack[ctr].mnt = lowerpath.mnt;
		ctr++;
		prev = this;
		if (opaque)
			break;
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	}

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	oe = ovl_alloc_entry(ctr);
	err = -ENOMEM;
	if (!oe)
		goto out_put;

	if (upperdentry || ctr) {
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		struct dentry *realdentry;

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		realdentry = upperdentry ? upperdentry : stack[0].dentry;

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		err = -ENOMEM;
		inode = ovl_new_inode(dentry->d_sb, realdentry->d_inode->i_mode,
				      oe);
		if (!inode)
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			goto out_free_oe;
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		ovl_copyattr(realdentry->d_inode, inode);
	}

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	oe->opaque = upperopaque;
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	oe->__upperdentry = upperdentry;
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	memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
	kfree(stack);
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	dentry->d_fsdata = oe;
	d_add(dentry, inode);

	return NULL;

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out_free_oe:
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	kfree(oe);
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out_put:
	for (i = 0; i < ctr; i++)
		dput(stack[i].dentry);
	kfree(stack);
out_put_upper:
	dput(upperdentry);
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out:
	return ERR_PTR(err);
}

struct file *ovl_path_open(struct path *path, int flags)
{
	return dentry_open(path, flags, current_cred());
}

static void ovl_put_super(struct super_block *sb)
{
	struct ovl_fs *ufs = sb->s_fs_info;
604
	unsigned i;
M
Miklos Szeredi 已提交
605 606 607

	dput(ufs->workdir);
	mntput(ufs->upper_mnt);
608 609
	for (i = 0; i < ufs->numlower; i++)
		mntput(ufs->lower_mnt[i]);
610
	kfree(ufs->lower_mnt);
M
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E
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612 613 614
	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
615
	put_cred(ufs->creator_cred);
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	kfree(ufs);
}

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619 620 621 622 623 624
/**
 * ovl_statfs
 * @sb: The overlayfs super block
 * @buf: The struct kstatfs to fill in with stats
 *
 * Get the filesystem statistics.  As writes always target the upper layer
625
 * filesystem pass the statfs to the upper filesystem (if it exists)
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626 627 628 629 630 631 632 633
 */
static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
{
	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
	struct dentry *root_dentry = dentry->d_sb->s_root;
	struct path path;
	int err;

634
	ovl_path_real(root_dentry, &path);
A
Andy Whitcroft 已提交
635 636 637 638 639 640 641 642 643 644

	err = vfs_statfs(&path, buf);
	if (!err) {
		buf->f_namelen = max(buf->f_namelen, ofs->lower_namelen);
		buf->f_type = OVERLAYFS_SUPER_MAGIC;
	}

	return err;
}

E
Erez Zadok 已提交
645 646 647 648 649 650 651 652 653 654 655
/**
 * ovl_show_options
 *
 * Prints the mount options for a given superblock.
 * Returns zero; does not fail.
 */
static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
{
	struct super_block *sb = dentry->d_sb;
	struct ovl_fs *ufs = sb->s_fs_info;

656
	seq_show_option(m, "lowerdir", ufs->config.lowerdir);
M
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657
	if (ufs->config.upperdir) {
658 659
		seq_show_option(m, "upperdir", ufs->config.upperdir);
		seq_show_option(m, "workdir", ufs->config.workdir);
M
Miklos Szeredi 已提交
660
	}
M
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661 662
	if (ufs->config.default_permissions)
		seq_puts(m, ",default_permissions");
E
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663 664 665
	return 0;
}

666 667 668 669
static int ovl_remount(struct super_block *sb, int *flags, char *data)
{
	struct ovl_fs *ufs = sb->s_fs_info;

670
	if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
671 672 673 674 675
		return -EROFS;

	return 0;
}

M
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676 677
static const struct super_operations ovl_super_operations = {
	.put_super	= ovl_put_super,
A
Andy Whitcroft 已提交
678
	.statfs		= ovl_statfs,
E
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679
	.show_options	= ovl_show_options,
680
	.remount_fs	= ovl_remount,
M
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681 682 683 684 685 686
};

enum {
	OPT_LOWERDIR,
	OPT_UPPERDIR,
	OPT_WORKDIR,
M
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687
	OPT_DEFAULT_PERMISSIONS,
M
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688 689 690 691 692 693 694
	OPT_ERR,
};

static const match_table_t ovl_tokens = {
	{OPT_LOWERDIR,			"lowerdir=%s"},
	{OPT_UPPERDIR,			"upperdir=%s"},
	{OPT_WORKDIR,			"workdir=%s"},
M
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695
	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
M
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	{OPT_ERR,			NULL}
};

M
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699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721
static char *ovl_next_opt(char **s)
{
	char *sbegin = *s;
	char *p;

	if (sbegin == NULL)
		return NULL;

	for (p = sbegin; *p; p++) {
		if (*p == '\\') {
			p++;
			if (!*p)
				break;
		} else if (*p == ',') {
			*p = '\0';
			*s = p + 1;
			return sbegin;
		}
	}
	*s = NULL;
	return sbegin;
}

M
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722 723 724 725
static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
	char *p;

M
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726
	while ((p = ovl_next_opt(&opt)) != NULL) {
M
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727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755
		int token;
		substring_t args[MAX_OPT_ARGS];

		if (!*p)
			continue;

		token = match_token(p, ovl_tokens, args);
		switch (token) {
		case OPT_UPPERDIR:
			kfree(config->upperdir);
			config->upperdir = match_strdup(&args[0]);
			if (!config->upperdir)
				return -ENOMEM;
			break;

		case OPT_LOWERDIR:
			kfree(config->lowerdir);
			config->lowerdir = match_strdup(&args[0]);
			if (!config->lowerdir)
				return -ENOMEM;
			break;

		case OPT_WORKDIR:
			kfree(config->workdir);
			config->workdir = match_strdup(&args[0]);
			if (!config->workdir)
				return -ENOMEM;
			break;

M
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756 757 758 759
		case OPT_DEFAULT_PERMISSIONS:
			config->default_permissions = true;
			break;

M
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760
		default:
761
			pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
M
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762 763 764
			return -EINVAL;
		}
	}
H
hujianyang 已提交
765 766 767 768 769 770 771 772 773

	/* Workdir is useless in non-upper mount */
	if (!config->upperdir && config->workdir) {
		pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
			config->workdir);
		kfree(config->workdir);
		config->workdir = NULL;
	}

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774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790
	return 0;
}

#define OVL_WORKDIR_NAME "work"

static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
					 struct dentry *dentry)
{
	struct inode *dir = dentry->d_inode;
	struct dentry *work;
	int err;
	bool retried = false;

	err = mnt_want_write(mnt);
	if (err)
		return ERR_PTR(err);

A
Al Viro 已提交
791
	inode_lock_nested(dir, I_MUTEX_PARENT);
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792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816
retry:
	work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
			      strlen(OVL_WORKDIR_NAME));

	if (!IS_ERR(work)) {
		struct kstat stat = {
			.mode = S_IFDIR | 0,
		};

		if (work->d_inode) {
			err = -EEXIST;
			if (retried)
				goto out_dput;

			retried = true;
			ovl_cleanup(dir, work);
			dput(work);
			goto retry;
		}

		err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
		if (err)
			goto out_dput;
	}
out_unlock:
A
Al Viro 已提交
817
	inode_unlock(dir);
M
Miklos Szeredi 已提交
818 819 820 821 822 823 824 825 826 827
	mnt_drop_write(mnt);

	return work;

out_dput:
	dput(work);
	work = ERR_PTR(err);
	goto out_unlock;
}

M
Miklos Szeredi 已提交
828 829 830 831 832 833 834 835 836 837 838 839 840
static void ovl_unescape(char *s)
{
	char *d = s;

	for (;; s++, d++) {
		if (*s == '\\')
			s++;
		*d = *s;
		if (!*s)
			break;
	}
}

M
Miklos Szeredi 已提交
841 842
static int ovl_mount_dir_noesc(const char *name, struct path *path)
{
843
	int err = -EINVAL;
M
Miklos Szeredi 已提交
844

845 846 847 848
	if (!*name) {
		pr_err("overlayfs: empty lowerdir\n");
		goto out;
	}
M
Miklos Szeredi 已提交
849 850 851 852 853 854
	err = kern_path(name, LOOKUP_FOLLOW, path);
	if (err) {
		pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
		goto out;
	}
	err = -EINVAL;
855
	if (ovl_dentry_weird(path->dentry)) {
M
Miklos Szeredi 已提交
856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878
		pr_err("overlayfs: filesystem on '%s' not supported\n", name);
		goto out_put;
	}
	if (!S_ISDIR(path->dentry->d_inode->i_mode)) {
		pr_err("overlayfs: '%s' not a directory\n", name);
		goto out_put;
	}
	return 0;

out_put:
	path_put(path);
out:
	return err;
}

static int ovl_mount_dir(const char *name, struct path *path)
{
	int err = -ENOMEM;
	char *tmp = kstrdup(name, GFP_KERNEL);

	if (tmp) {
		ovl_unescape(tmp);
		err = ovl_mount_dir_noesc(tmp, path);
879 880 881 882 883 884 885 886

		if (!err)
			if (ovl_dentry_remote(path->dentry)) {
				pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
				       tmp);
				path_put(path);
				err = -EINVAL;
			}
M
Miklos Szeredi 已提交
887 888 889 890 891 892
		kfree(tmp);
	}
	return err;
}

static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
893
			 int *stack_depth, bool *remote)
M
Miklos Szeredi 已提交
894 895 896 897
{
	int err;
	struct kstatfs statfs;

898
	err = ovl_mount_dir_noesc(name, path);
M
Miklos Szeredi 已提交
899 900 901 902 903 904 905 906 907 908 909
	if (err)
		goto out;

	err = vfs_statfs(path, &statfs);
	if (err) {
		pr_err("overlayfs: statfs failed on '%s'\n", name);
		goto out_put;
	}
	*namelen = max(*namelen, statfs.f_namelen);
	*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);

910 911 912
	if (ovl_dentry_remote(path->dentry))
		*remote = true;

M
Miklos Szeredi 已提交
913 914 915 916 917 918 919 920
	return 0;

out_put:
	path_put(path);
out:
	return err;
}

M
Miklos Szeredi 已提交
921 922 923 924 925 926 927 928 929 930 931 932
/* Workdir should not be subdir of upperdir and vice versa */
static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
{
	bool ok = false;

	if (workdir != upperdir) {
		ok = (lock_rename(workdir, upperdir) == NULL);
		unlock_rename(workdir, upperdir);
	}
	return ok;
}

933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952
static unsigned int ovl_split_lowerdirs(char *str)
{
	unsigned int ctr = 1;
	char *s, *d;

	for (s = d = str;; s++, d++) {
		if (*s == '\\') {
			s++;
		} else if (*s == ':') {
			*d = '\0';
			ctr++;
			continue;
		}
		*d = *s;
		if (!*s)
			break;
	}
	return ctr;
}

M
Miklos Szeredi 已提交
953 954
static int ovl_fill_super(struct super_block *sb, void *data, int silent)
{
M
Miklos Szeredi 已提交
955 956
	struct path upperpath = { NULL, NULL };
	struct path workpath = { NULL, NULL };
M
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957 958 959
	struct dentry *root_dentry;
	struct ovl_entry *oe;
	struct ovl_fs *ufs;
960 961 962 963 964
	struct path *stack = NULL;
	char *lowertmp;
	char *lower;
	unsigned int numlower;
	unsigned int stacklen = 0;
965
	unsigned int i;
966
	bool remote = false;
M
Miklos Szeredi 已提交
967 968
	int err;

E
Erez Zadok 已提交
969 970 971
	err = -ENOMEM;
	ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
	if (!ufs)
M
Miklos Szeredi 已提交
972 973
		goto out;

E
Erez Zadok 已提交
974 975 976 977
	err = ovl_parse_opt((char *) data, &ufs->config);
	if (err)
		goto out_free_config;

M
Miklos Szeredi 已提交
978
	err = -EINVAL;
M
Miklos Szeredi 已提交
979
	if (!ufs->config.lowerdir) {
980 981
		if (!silent)
			pr_err("overlayfs: missing 'lowerdir'\n");
M
Miklos Szeredi 已提交
982 983 984
		goto out_free_config;
	}

M
Miklos Szeredi 已提交
985
	sb->s_stack_depth = 0;
986
	sb->s_maxbytes = MAX_LFS_FILESIZE;
M
Miklos Szeredi 已提交
987 988 989 990 991
	if (ufs->config.upperdir) {
		if (!ufs->config.workdir) {
			pr_err("overlayfs: missing 'workdir'\n");
			goto out_free_config;
		}
M
Miklos Szeredi 已提交
992

M
Miklos Szeredi 已提交
993 994 995
		err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
		if (err)
			goto out_free_config;
M
Miklos Szeredi 已提交
996

H
hujianyang 已提交
997 998 999 1000 1001 1002 1003
		/* Upper fs should not be r/o */
		if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
			pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
			err = -EINVAL;
			goto out_put_upperpath;
		}

M
Miklos Szeredi 已提交
1004 1005 1006 1007
		err = ovl_mount_dir(ufs->config.workdir, &workpath);
		if (err)
			goto out_put_upperpath;

1008
		err = -EINVAL;
M
Miklos Szeredi 已提交
1009 1010 1011 1012 1013 1014 1015 1016 1017
		if (upperpath.mnt != workpath.mnt) {
			pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
			goto out_put_workpath;
		}
		if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
			pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
			goto out_put_workpath;
		}
		sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
A
Andy Whitcroft 已提交
1018
	}
1019 1020 1021
	err = -ENOMEM;
	lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
	if (!lowertmp)
M
Miklos Szeredi 已提交
1022
		goto out_put_workpath;
1023

1024 1025
	err = -EINVAL;
	stacklen = ovl_split_lowerdirs(lowertmp);
1026 1027 1028
	if (stacklen > OVL_MAX_STACK) {
		pr_err("overlayfs: too many lower directries, limit is %d\n",
		       OVL_MAX_STACK);
1029
		goto out_free_lowertmp;
1030 1031 1032 1033
	} else if (!ufs->config.upperdir && stacklen == 1) {
		pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
		goto out_free_lowertmp;
	}
1034 1035 1036 1037 1038 1039 1040 1041

	stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
	if (!stack)
		goto out_free_lowertmp;

	lower = lowertmp;
	for (numlower = 0; numlower < stacklen; numlower++) {
		err = ovl_lower_dir(lower, &stack[numlower],
1042 1043
				    &ufs->lower_namelen, &sb->s_stack_depth,
				    &remote);
1044 1045 1046 1047 1048 1049
		if (err)
			goto out_put_lowerpath;

		lower = strchr(lower, '\0') + 1;
	}

1050
	err = -EINVAL;
M
Miklos Szeredi 已提交
1051
	sb->s_stack_depth++;
1052 1053
	if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
		pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1054
		goto out_put_lowerpath;
1055 1056
	}

M
Miklos Szeredi 已提交
1057 1058 1059 1060 1061 1062 1063
	if (ufs->config.upperdir) {
		ufs->upper_mnt = clone_private_mount(&upperpath);
		err = PTR_ERR(ufs->upper_mnt);
		if (IS_ERR(ufs->upper_mnt)) {
			pr_err("overlayfs: failed to clone upperpath\n");
			goto out_put_lowerpath;
		}
1064

M
Miklos Szeredi 已提交
1065 1066 1067
		ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
		err = PTR_ERR(ufs->workdir);
		if (IS_ERR(ufs->workdir)) {
1068 1069 1070 1071
			pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
				ufs->config.workdir, OVL_WORKDIR_NAME, -err);
			sb->s_flags |= MS_RDONLY;
			ufs->workdir = NULL;
M
Miklos Szeredi 已提交
1072
		}
1073 1074 1075 1076

		/*
		 * Upper should support d_type, else whiteouts are visible.
		 * Given workdir and upper are on same fs, we can do
1077 1078
		 * iterate_dir() on workdir. This check requires successful
		 * creation of workdir in previous step.
1079
		 */
1080 1081 1082 1083
		if (ufs->workdir) {
			err = ovl_check_d_type_supported(&workpath);
			if (err < 0)
				goto out_put_workdir;
1084

1085 1086 1087 1088 1089
			if (!err) {
				pr_err("overlayfs: upper fs needs to support d_type.\n");
				err = -EINVAL;
				goto out_put_workdir;
			}
1090
		}
M
Miklos Szeredi 已提交
1091 1092
	}

1093
	err = -ENOMEM;
1094
	ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
1095
	if (ufs->lower_mnt == NULL)
1096
		goto out_put_workdir;
1097 1098
	for (i = 0; i < numlower; i++) {
		struct vfsmount *mnt = clone_private_mount(&stack[i]);
1099

1100
		err = PTR_ERR(mnt);
1101 1102 1103 1104 1105 1106 1107 1108 1109
		if (IS_ERR(mnt)) {
			pr_err("overlayfs: failed to clone lowerpath\n");
			goto out_put_lower_mnt;
		}
		/*
		 * Make lower_mnt R/O.  That way fchmod/fchown on lower file
		 * will fail instead of modifying lower fs.
		 */
		mnt->mnt_flags |= MNT_READONLY;
1110

1111 1112 1113
		ufs->lower_mnt[ufs->numlower] = mnt;
		ufs->numlower++;
	}
M
Miklos Szeredi 已提交
1114

H
hujianyang 已提交
1115 1116
	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
	if (!ufs->upper_mnt)
M
Miklos Szeredi 已提交
1117 1118
		sb->s_flags |= MS_RDONLY;

1119 1120 1121 1122
	if (remote)
		sb->s_d_op = &ovl_reval_dentry_operations;
	else
		sb->s_d_op = &ovl_dentry_operations;
M
Miklos Szeredi 已提交
1123

1124 1125 1126 1127
	ufs->creator_cred = prepare_creds();
	if (!ufs->creator_cred)
		goto out_put_lower_mnt;

M
Miklos Szeredi 已提交
1128
	err = -ENOMEM;
1129
	oe = ovl_alloc_entry(numlower);
1130
	if (!oe)
1131
		goto out_put_cred;
M
Miklos Szeredi 已提交
1132

1133
	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, oe));
M
Miklos Szeredi 已提交
1134
	if (!root_dentry)
1135
		goto out_free_oe;
M
Miklos Szeredi 已提交
1136 1137

	mntput(upperpath.mnt);
1138 1139
	for (i = 0; i < numlower; i++)
		mntput(stack[i].mnt);
M
Miklos Szeredi 已提交
1140
	path_put(&workpath);
1141
	kfree(lowertmp);
M
Miklos Szeredi 已提交
1142 1143

	oe->__upperdentry = upperpath.dentry;
1144 1145 1146 1147
	for (i = 0; i < numlower; i++) {
		oe->lowerstack[i].dentry = stack[i].dentry;
		oe->lowerstack[i].mnt = ufs->lower_mnt[i];
	}
1148
	kfree(stack);
M
Miklos Szeredi 已提交
1149 1150 1151

	root_dentry->d_fsdata = oe;

M
Miklos Szeredi 已提交
1152 1153 1154
	ovl_copyattr(ovl_dentry_real(root_dentry)->d_inode,
		     root_dentry->d_inode);

A
Andy Whitcroft 已提交
1155
	sb->s_magic = OVERLAYFS_SUPER_MAGIC;
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	sb->s_op = &ovl_super_operations;
	sb->s_root = root_dentry;
	sb->s_fs_info = ufs;

	return 0;

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out_free_oe:
	kfree(oe);
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out_put_cred:
	put_cred(ufs->creator_cred);
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out_put_lower_mnt:
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	for (i = 0; i < ufs->numlower; i++)
		mntput(ufs->lower_mnt[i]);
	kfree(ufs->lower_mnt);
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out_put_workdir:
	dput(ufs->workdir);
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	mntput(ufs->upper_mnt);
out_put_lowerpath:
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	for (i = 0; i < numlower; i++)
		path_put(&stack[i]);
	kfree(stack);
out_free_lowertmp:
	kfree(lowertmp);
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out_put_workpath:
	path_put(&workpath);
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out_put_upperpath:
	path_put(&upperpath);
out_free_config:
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	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
	kfree(ufs);
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out:
	return err;
}

static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
				const char *dev_name, void *raw_data)
{
	return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
}

static struct file_system_type ovl_fs_type = {
	.owner		= THIS_MODULE,
1200
	.name		= "overlay",
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	.mount		= ovl_mount,
	.kill_sb	= kill_anon_super,
};
1204
MODULE_ALIAS_FS("overlay");
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static int __init ovl_init(void)
{
	return register_filesystem(&ovl_fs_type);
}

static void __exit ovl_exit(void)
{
	unregister_filesystem(&ovl_fs_type);
}

module_init(ovl_init);
module_exit(ovl_exit);