super.c 30.0 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.
 */

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#include <uapi/linux/magic.h>
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#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/xattr.h>
#include <linux/mount.h>
#include <linux/parser.h>
#include <linux/module.h>
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#include <linux/statfs.h>
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#include <linux/seq_file.h>
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#include <linux/posix_acl_xattr.h>
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#include "overlayfs.h"

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


struct ovl_dir_cache;

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#define OVL_MAX_STACK 500

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static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
MODULE_PARM_DESC(ovl_redirect_dir_def,
		 "Default to on or off for the redirect_dir feature");
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static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
module_param_named(index, ovl_index_def, bool, 0644);
MODULE_PARM_DESC(ovl_index_def,
		 "Default to on or off for the inodes index feature");

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

	if (oe) {
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		unsigned int i;

		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 int ovl_check_append_only(struct inode *inode, int flag)
{
	/*
	 * This test was moot in vfs may_open() because overlay inode does
	 * not have the S_APPEND flag, so re-check on real upper inode
	 */
	if (IS_APPEND(inode)) {
		if  ((flag & O_ACCMODE) != O_RDONLY && !(flag & O_APPEND))
			return -EPERM;
		if (flag & O_TRUNC)
			return -EPERM;
	}

	return 0;
}

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static struct dentry *ovl_d_real(struct dentry *dentry,
				 const struct inode *inode,
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				 unsigned int open_flags, unsigned int flags)
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{
	struct dentry *real;
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	int err;
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	if (flags & D_REAL_UPPER)
		return ovl_dentry_upper(dentry);

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

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	if (open_flags) {
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		err = ovl_open_maybe_copy_up(dentry, open_flags);
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		if (err)
			return ERR_PTR(err);
	}

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	real = ovl_dentry_upper(dentry);
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	if (real && (!inode || inode == d_inode(real))) {
		if (!inode) {
			err = ovl_check_append_only(d_inode(real), open_flags);
			if (err)
				return ERR_PTR(err);
		}
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		return real;
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	}
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	real = ovl_dentry_lower(dentry);
	if (!real)
		goto bug;

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	/* Handle recursion */
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	real = d_real(real, inode, open_flags, 0);
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	if (!inode || inode == d_inode(real))
		return real;
bug:
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	WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
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	     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_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_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 kmem_cache *ovl_inode_cachep;

static struct inode *ovl_alloc_inode(struct super_block *sb)
{
	struct ovl_inode *oi = kmem_cache_alloc(ovl_inode_cachep, GFP_KERNEL);

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	if (!oi)
		return NULL;

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	oi->cache = NULL;
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	oi->redirect = NULL;
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	oi->version = 0;
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	oi->flags = 0;
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	oi->__upperdentry = NULL;
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	oi->lower = NULL;
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	mutex_init(&oi->lock);
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	return &oi->vfs_inode;
}

static void ovl_i_callback(struct rcu_head *head)
{
	struct inode *inode = container_of(head, struct inode, i_rcu);

	kmem_cache_free(ovl_inode_cachep, OVL_I(inode));
}

static void ovl_destroy_inode(struct inode *inode)
{
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	struct ovl_inode *oi = OVL_I(inode);

	dput(oi->__upperdentry);
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	kfree(oi->redirect);
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	ovl_dir_cache_free(inode);
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	mutex_destroy(&oi->lock);
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	call_rcu(&inode->i_rcu, ovl_i_callback);
}

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static void ovl_put_super(struct super_block *sb)
{
	struct ovl_fs *ufs = sb->s_fs_info;
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	unsigned i;
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	dput(ufs->indexdir);
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	dput(ufs->workdir);
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	if (ufs->workdir_locked)
		ovl_inuse_unlock(ufs->workbasedir);
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	dput(ufs->workbasedir);
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	if (ufs->upper_mnt && ufs->upperdir_locked)
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		ovl_inuse_unlock(ufs->upper_mnt->mnt_root);
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	mntput(ufs->upper_mnt);
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	for (i = 0; i < ufs->numlower; i++) {
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		mntput(ufs->lower_layers[i].mnt);
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		free_anon_bdev(ufs->lower_layers[i].pseudo_dev);
	}
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	kfree(ufs->lower_layers);
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	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
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	put_cred(ufs->creator_cred);
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	kfree(ufs);
}

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static int ovl_sync_fs(struct super_block *sb, int wait)
{
	struct ovl_fs *ufs = sb->s_fs_info;
	struct super_block *upper_sb;
	int ret;

	if (!ufs->upper_mnt)
		return 0;
	upper_sb = ufs->upper_mnt->mnt_sb;
	if (!upper_sb->s_op->sync_fs)
		return 0;

	/* real inodes have already been synced by sync_filesystem(ovl_sb) */
	down_read(&upper_sb->s_umount);
	ret = upper_sb->s_op->sync_fs(upper_sb, wait);
	up_read(&upper_sb->s_umount);
	return ret;
}

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/**
 * 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
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 * filesystem pass the statfs to the upper filesystem (if it exists)
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 */
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;

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

	return err;
}

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/* Will this overlay be forced to mount/remount ro? */
static bool ovl_force_readonly(struct ovl_fs *ufs)
{
	return (!ufs->upper_mnt || !ufs->workdir);
}

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/**
 * 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;

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	seq_show_option(m, "lowerdir", ufs->config.lowerdir);
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	if (ufs->config.upperdir) {
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		seq_show_option(m, "upperdir", ufs->config.upperdir);
		seq_show_option(m, "workdir", ufs->config.workdir);
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	}
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	if (ufs->config.default_permissions)
		seq_puts(m, ",default_permissions");
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	if (ufs->config.redirect_dir != ovl_redirect_dir_def)
		seq_printf(m, ",redirect_dir=%s",
			   ufs->config.redirect_dir ? "on" : "off");
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	if (ufs->config.index != ovl_index_def)
		seq_printf(m, ",index=%s",
			   ufs->config.index ? "on" : "off");
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	return 0;
}

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

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	if (!(*flags & MS_RDONLY) && ovl_force_readonly(ufs))
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		return -EROFS;

	return 0;
}

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static const struct super_operations ovl_super_operations = {
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	.alloc_inode	= ovl_alloc_inode,
	.destroy_inode	= ovl_destroy_inode,
	.drop_inode	= generic_delete_inode,
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	.put_super	= ovl_put_super,
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	.sync_fs	= ovl_sync_fs,
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	.statfs		= ovl_statfs,
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	.show_options	= ovl_show_options,
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	.remount_fs	= ovl_remount,
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};

enum {
	OPT_LOWERDIR,
	OPT_UPPERDIR,
	OPT_WORKDIR,
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	OPT_DEFAULT_PERMISSIONS,
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	OPT_REDIRECT_DIR_ON,
	OPT_REDIRECT_DIR_OFF,
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	OPT_INDEX_ON,
	OPT_INDEX_OFF,
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	OPT_ERR,
};

static const match_table_t ovl_tokens = {
	{OPT_LOWERDIR,			"lowerdir=%s"},
	{OPT_UPPERDIR,			"upperdir=%s"},
	{OPT_WORKDIR,			"workdir=%s"},
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	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
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	{OPT_REDIRECT_DIR_ON,		"redirect_dir=on"},
	{OPT_REDIRECT_DIR_OFF,		"redirect_dir=off"},
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	{OPT_INDEX_ON,			"index=on"},
	{OPT_INDEX_OFF,			"index=off"},
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	{OPT_ERR,			NULL}
};

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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;
}

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static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
	char *p;

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	while ((p = ovl_next_opt(&opt)) != NULL) {
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		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;

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		case OPT_DEFAULT_PERMISSIONS:
			config->default_permissions = true;
			break;

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		case OPT_REDIRECT_DIR_ON:
			config->redirect_dir = true;
			break;

		case OPT_REDIRECT_DIR_OFF:
			config->redirect_dir = false;
			break;

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		case OPT_INDEX_ON:
			config->index = true;
			break;

		case OPT_INDEX_OFF:
			config->index = false;
			break;

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		default:
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			pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
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			return -EINVAL;
		}
	}
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	/* 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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	return 0;
}

#define OVL_WORKDIR_NAME "work"
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#define OVL_INDEXDIR_NAME "index"
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static struct dentry *ovl_workdir_create(struct super_block *sb,
					 struct ovl_fs *ufs,
					 struct dentry *dentry,
					 const char *name, bool persist)
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{
	struct inode *dir = dentry->d_inode;
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	struct vfsmount *mnt = ufs->upper_mnt;
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	struct dentry *work;
	int err;
	bool retried = false;
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	bool locked = false;
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	err = mnt_want_write(mnt);
	if (err)
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		goto out_err;
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	inode_lock_nested(dir, I_MUTEX_PARENT);
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	locked = true;

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retry:
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	work = lookup_one_len(name, dentry, strlen(name));
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	if (!IS_ERR(work)) {
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		struct iattr attr = {
			.ia_valid = ATTR_MODE,
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			.ia_mode = S_IFDIR | 0,
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		};
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		if (work->d_inode) {
			err = -EEXIST;
			if (retried)
				goto out_dput;

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			if (persist)
				goto out_unlock;

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			retried = true;
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			ovl_workdir_cleanup(dir, mnt, work, 0);
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			dput(work);
			goto retry;
		}

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		err = ovl_create_real(dir, work,
				      &(struct cattr){.mode = S_IFDIR | 0},
				      NULL, true);
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		if (err)
			goto out_dput;
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		/*
		 * Try to remove POSIX ACL xattrs from workdir.  We are good if:
		 *
		 * a) success (there was a POSIX ACL xattr and was removed)
		 * b) -ENODATA (there was no POSIX ACL xattr)
		 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
		 *
		 * There are various other error values that could effectively
		 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
		 * if the xattr name is too long), but the set of filesystems
		 * allowed as upper are limited to "normal" ones, where checking
		 * for the above two errors is sufficient.
		 */
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		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
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		if (err && err != -ENODATA && err != -EOPNOTSUPP)
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			goto out_dput;

		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
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		if (err && err != -ENODATA && err != -EOPNOTSUPP)
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			goto out_dput;

		/* Clear any inherited mode bits */
		inode_lock(work->d_inode);
		err = notify_change(work, &attr, NULL);
		inode_unlock(work->d_inode);
		if (err)
			goto out_dput;
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	} else {
		err = PTR_ERR(work);
		goto out_err;
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	}
out_unlock:
	mnt_drop_write(mnt);
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	if (locked)
		inode_unlock(dir);
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	return work;

out_dput:
	dput(work);
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out_err:
	pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
		ufs->config.workdir, name, -err);
	sb->s_flags |= MS_RDONLY;
	work = NULL;
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	goto out_unlock;
}

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static void ovl_unescape(char *s)
{
	char *d = s;

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

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static int ovl_mount_dir_noesc(const char *name, struct path *path)
{
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	int err = -EINVAL;
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	if (!*name) {
		pr_err("overlayfs: empty lowerdir\n");
		goto out;
	}
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	err = kern_path(name, LOOKUP_FOLLOW, path);
	if (err) {
		pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
		goto out;
	}
	err = -EINVAL;
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	if (ovl_dentry_weird(path->dentry)) {
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579 580 581
		pr_err("overlayfs: filesystem on '%s' not supported\n", name);
		goto out_put;
	}
M
Miklos Szeredi 已提交
582
	if (!d_is_dir(path->dentry)) {
M
Miklos Szeredi 已提交
583 584 585 586 587 588
		pr_err("overlayfs: '%s' not a directory\n", name);
		goto out_put;
	}
	return 0;

out_put:
589
	path_put_init(path);
M
Miklos Szeredi 已提交
590 591 592 593 594 595 596 597 598 599 600 601
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);
602 603 604 605 606

		if (!err)
			if (ovl_dentry_remote(path->dentry)) {
				pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
				       tmp);
607
				path_put_init(path);
608 609
				err = -EINVAL;
			}
M
Miklos Szeredi 已提交
610 611 612 613 614
		kfree(tmp);
	}
	return err;
}

M
Miklos Szeredi 已提交
615 616
static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
			     const char *name)
M
Miklos Szeredi 已提交
617 618
{
	struct kstatfs statfs;
M
Miklos Szeredi 已提交
619 620 621 622 623 624 625 626 627 628 629 630 631 632
	int err = vfs_statfs(path, &statfs);

	if (err)
		pr_err("overlayfs: statfs failed on '%s'\n", name);
	else
		ofs->namelen = max(ofs->namelen, statfs.f_namelen);

	return err;
}

static int ovl_lower_dir(const char *name, struct path *path,
			 struct ovl_fs *ofs, int *stack_depth, bool *remote)
{
	int err;
M
Miklos Szeredi 已提交
633

634
	err = ovl_mount_dir_noesc(name, path);
M
Miklos Szeredi 已提交
635 636 637
	if (err)
		goto out;

M
Miklos Szeredi 已提交
638 639
	err = ovl_check_namelen(path, ofs, name);
	if (err)
M
Miklos Szeredi 已提交
640
		goto out_put;
M
Miklos Szeredi 已提交
641

M
Miklos Szeredi 已提交
642 643
	*stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);

644 645 646
	if (ovl_dentry_remote(path->dentry))
		*remote = true;

647 648 649 650 651 652 653 654 655
	/*
	 * The inodes index feature needs to encode and decode file
	 * handles, so it requires that all layers support them.
	 */
	if (ofs->config.index && !ovl_can_decode_fh(path->dentry->d_sb)) {
		ofs->config.index = false;
		pr_warn("overlayfs: fs on '%s' does not support file handles, falling back to index=off.\n", name);
	}

M
Miklos Szeredi 已提交
656 657 658
	return 0;

out_put:
659
	path_put_init(path);
M
Miklos Szeredi 已提交
660 661 662 663
out:
	return err;
}

M
Miklos Szeredi 已提交
664 665 666 667 668 669 670 671 672 673 674 675
/* 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;
}

676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695
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;
}

696 697 698 699 700
static int __maybe_unused
ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
			struct dentry *dentry, struct inode *inode,
			const char *name, void *buffer, size_t size)
{
701
	return ovl_xattr_get(dentry, inode, handler->name, buffer, size);
702 703
}

704 705 706 707 708
static int __maybe_unused
ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
			struct dentry *dentry, struct inode *inode,
			const char *name, const void *value,
			size_t size, int flags)
M
Miklos Szeredi 已提交
709 710
{
	struct dentry *workdir = ovl_workdir(dentry);
711
	struct inode *realinode = ovl_inode_real(inode);
M
Miklos Szeredi 已提交
712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735
	struct posix_acl *acl = NULL;
	int err;

	/* Check that everything is OK before copy-up */
	if (value) {
		acl = posix_acl_from_xattr(&init_user_ns, value, size);
		if (IS_ERR(acl))
			return PTR_ERR(acl);
	}
	err = -EOPNOTSUPP;
	if (!IS_POSIXACL(d_inode(workdir)))
		goto out_acl_release;
	if (!realinode->i_op->set_acl)
		goto out_acl_release;
	if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
		err = acl ? -EACCES : 0;
		goto out_acl_release;
	}
	err = -EPERM;
	if (!inode_owner_or_capable(inode))
		goto out_acl_release;

	posix_acl_release(acl);

736 737 738 739 740 741 742 743 744 745 746 747 748 749 750
	/*
	 * Check if sgid bit needs to be cleared (actual setacl operation will
	 * be done with mounter's capabilities and so that won't do it for us).
	 */
	if (unlikely(inode->i_mode & S_ISGID) &&
	    handler->flags == ACL_TYPE_ACCESS &&
	    !in_group_p(inode->i_gid) &&
	    !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
		struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };

		err = ovl_setattr(dentry, &iattr);
		if (err)
			return err;
	}

751
	err = ovl_xattr_set(dentry, inode, handler->name, value, size, flags);
752
	if (!err)
753
		ovl_copyattr(ovl_inode_real(inode), inode);
754 755

	return err;
M
Miklos Szeredi 已提交
756 757 758 759 760 761

out_acl_release:
	posix_acl_release(acl);
	return err;
}

762 763 764 765
static int ovl_own_xattr_get(const struct xattr_handler *handler,
			     struct dentry *dentry, struct inode *inode,
			     const char *name, void *buffer, size_t size)
{
A
Amir Goldstein 已提交
766
	return -EOPNOTSUPP;
767 768
}

M
Miklos Szeredi 已提交
769 770 771 772 773
static int ovl_own_xattr_set(const struct xattr_handler *handler,
			     struct dentry *dentry, struct inode *inode,
			     const char *name, const void *value,
			     size_t size, int flags)
{
A
Amir Goldstein 已提交
774
	return -EOPNOTSUPP;
M
Miklos Szeredi 已提交
775 776
}

777 778 779 780
static int ovl_other_xattr_get(const struct xattr_handler *handler,
			       struct dentry *dentry, struct inode *inode,
			       const char *name, void *buffer, size_t size)
{
781
	return ovl_xattr_get(dentry, inode, name, buffer, size);
782 783
}

784 785 786 787 788
static int ovl_other_xattr_set(const struct xattr_handler *handler,
			       struct dentry *dentry, struct inode *inode,
			       const char *name, const void *value,
			       size_t size, int flags)
{
789
	return ovl_xattr_set(dentry, inode, name, value, size, flags);
790 791
}

792 793
static const struct xattr_handler __maybe_unused
ovl_posix_acl_access_xattr_handler = {
M
Miklos Szeredi 已提交
794 795
	.name = XATTR_NAME_POSIX_ACL_ACCESS,
	.flags = ACL_TYPE_ACCESS,
796
	.get = ovl_posix_acl_xattr_get,
M
Miklos Szeredi 已提交
797 798 799
	.set = ovl_posix_acl_xattr_set,
};

800 801
static const struct xattr_handler __maybe_unused
ovl_posix_acl_default_xattr_handler = {
M
Miklos Szeredi 已提交
802 803
	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
	.flags = ACL_TYPE_DEFAULT,
804
	.get = ovl_posix_acl_xattr_get,
M
Miklos Szeredi 已提交
805 806 807 808 809
	.set = ovl_posix_acl_xattr_set,
};

static const struct xattr_handler ovl_own_xattr_handler = {
	.prefix	= OVL_XATTR_PREFIX,
810
	.get = ovl_own_xattr_get,
M
Miklos Szeredi 已提交
811 812 813 814 815
	.set = ovl_own_xattr_set,
};

static const struct xattr_handler ovl_other_xattr_handler = {
	.prefix	= "", /* catch all */
816
	.get = ovl_other_xattr_get,
M
Miklos Szeredi 已提交
817 818 819 820
	.set = ovl_other_xattr_set,
};

static const struct xattr_handler *ovl_xattr_handlers[] = {
821
#ifdef CONFIG_FS_POSIX_ACL
M
Miklos Szeredi 已提交
822 823
	&ovl_posix_acl_access_xattr_handler,
	&ovl_posix_acl_default_xattr_handler,
824
#endif
M
Miklos Szeredi 已提交
825 826 827 828 829
	&ovl_own_xattr_handler,
	&ovl_other_xattr_handler,
	NULL
};

830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862
static int ovl_get_upperpath(struct ovl_fs *ufs, struct path *upperpath)
{
	int err;

	err = ovl_mount_dir(ufs->config.upperdir, upperpath);
	if (err)
		goto out;

	/* Upper fs should not be r/o */
	if (sb_rdonly(upperpath->mnt->mnt_sb)) {
		pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
		err = -EINVAL;
		goto out;
	}

	err = ovl_check_namelen(upperpath, ufs, ufs->config.upperdir);
	if (err)
		goto out;

	err = -EBUSY;
	if (ovl_inuse_trylock(upperpath->dentry)) {
		ufs->upperdir_locked = true;
	} else if (ufs->config.index) {
		pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n");
		goto out;
	} else {
		pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
	}
	err = 0;
out:
	return err;
}

M
Miklos Szeredi 已提交
863 864
static int ovl_fill_super(struct super_block *sb, void *data, int silent)
{
K
Kees Cook 已提交
865 866
	struct path upperpath = { };
	struct path workpath = { };
M
Miklos Szeredi 已提交
867 868 869
	struct dentry *root_dentry;
	struct ovl_entry *oe;
	struct ovl_fs *ufs;
870 871 872 873 874
	struct path *stack = NULL;
	char *lowertmp;
	char *lower;
	unsigned int numlower;
	unsigned int stacklen = 0;
875
	unsigned int i;
876
	bool remote = false;
877
	struct cred *cred;
M
Miklos Szeredi 已提交
878 879
	int err;

E
Erez Zadok 已提交
880 881 882
	err = -ENOMEM;
	ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
	if (!ufs)
M
Miklos Szeredi 已提交
883 884
		goto out;

885
	ufs->config.redirect_dir = ovl_redirect_dir_def;
886
	ufs->config.index = ovl_index_def;
E
Erez Zadok 已提交
887 888 889 890
	err = ovl_parse_opt((char *) data, &ufs->config);
	if (err)
		goto out_free_config;

M
Miklos Szeredi 已提交
891
	err = -EINVAL;
M
Miklos Szeredi 已提交
892
	if (!ufs->config.lowerdir) {
893 894
		if (!silent)
			pr_err("overlayfs: missing 'lowerdir'\n");
M
Miklos Szeredi 已提交
895 896 897
		goto out_free_config;
	}

M
Miklos Szeredi 已提交
898
	sb->s_stack_depth = 0;
899
	sb->s_maxbytes = MAX_LFS_FILESIZE;
M
Miklos Szeredi 已提交
900 901 902 903 904
	if (ufs->config.upperdir) {
		if (!ufs->config.workdir) {
			pr_err("overlayfs: missing 'workdir'\n");
			goto out_free_config;
		}
M
Miklos Szeredi 已提交
905

906
		err = ovl_get_upperpath(ufs, &upperpath);
M
Miklos Szeredi 已提交
907
		if (err)
908
			goto out_unlock_upperdentry;
909

M
Miklos Szeredi 已提交
910 911
		err = ovl_mount_dir(ufs->config.workdir, &workpath);
		if (err)
912
			goto out_unlock_upperdentry;
M
Miklos Szeredi 已提交
913

914
		err = -EINVAL;
M
Miklos Szeredi 已提交
915 916 917 918 919 920 921 922
		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;
		}
923 924

		err = -EBUSY;
925 926 927 928
		if (ovl_inuse_trylock(workpath.dentry)) {
			ufs->workdir_locked = true;
		} else if (ufs->config.index) {
			pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n");
929
			goto out_put_workpath;
930 931
		} else {
			pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
932 933 934
		}

		ufs->workbasedir = workpath.dentry;
M
Miklos Szeredi 已提交
935
		sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
A
Andy Whitcroft 已提交
936
	}
937 938 939
	err = -ENOMEM;
	lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
	if (!lowertmp)
940
		goto out_unlock_workdentry;
941

942 943
	err = -EINVAL;
	stacklen = ovl_split_lowerdirs(lowertmp);
944
	if (stacklen > OVL_MAX_STACK) {
945
		pr_err("overlayfs: too many lower directories, limit is %d\n",
946
		       OVL_MAX_STACK);
947
		goto out_free_lowertmp;
948 949 950 951
	} else if (!ufs->config.upperdir && stacklen == 1) {
		pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
		goto out_free_lowertmp;
	}
952

953
	err = -ENOMEM;
954 955 956 957
	stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
	if (!stack)
		goto out_free_lowertmp;

958
	err = -EINVAL;
959 960
	lower = lowertmp;
	for (numlower = 0; numlower < stacklen; numlower++) {
M
Miklos Szeredi 已提交
961 962
		err = ovl_lower_dir(lower, &stack[numlower], ufs,
				    &sb->s_stack_depth, &remote);
963 964 965 966 967 968
		if (err)
			goto out_put_lowerpath;

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

969
	err = -EINVAL;
M
Miklos Szeredi 已提交
970
	sb->s_stack_depth++;
971 972
	if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
		pr_err("overlayfs: maximum fs stacking depth exceeded\n");
973
		goto out_put_lowerpath;
974 975
	}

M
Miklos Szeredi 已提交
976 977 978 979 980 981 982
	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;
		}
983

M
Miklos Szeredi 已提交
984 985 986 987
		/* Don't inherit atime flags */
		ufs->upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);

		sb->s_time_gran = ufs->upper_mnt->mnt_sb->s_time_gran;
988

989 990
		ufs->workdir = ovl_workdir_create(sb, ufs, workpath.dentry,
						  OVL_WORKDIR_NAME, false);
991 992 993
		/*
		 * Upper should support d_type, else whiteouts are visible.
		 * Given workdir and upper are on same fs, we can do
994 995
		 * iterate_dir() on workdir. This check requires successful
		 * creation of workdir in previous step.
996
		 */
997
		if (ufs->workdir) {
998 999
			struct dentry *temp;

1000 1001 1002
			err = ovl_check_d_type_supported(&workpath);
			if (err < 0)
				goto out_put_workdir;
1003

1004 1005 1006 1007 1008 1009 1010
			/*
			 * We allowed this configuration and don't want to
			 * break users over kernel upgrade. So warn instead
			 * of erroring out.
			 */
			if (!err)
				pr_warn("overlayfs: upper fs needs to support d_type.\n");
1011 1012 1013 1014 1015 1016 1017 1018

			/* Check if upper/work fs supports O_TMPFILE */
			temp = ovl_do_tmpfile(ufs->workdir, S_IFREG | 0);
			ufs->tmpfile = !IS_ERR(temp);
			if (ufs->tmpfile)
				dput(temp);
			else
				pr_warn("overlayfs: upper fs does not support tmpfile.\n");
1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031

			/*
			 * Check if upper/work fs supports trusted.overlay.*
			 * xattr
			 */
			err = ovl_do_setxattr(ufs->workdir, OVL_XATTR_OPAQUE,
					      "0", 1, 0);
			if (err) {
				ufs->noxattr = true;
				pr_warn("overlayfs: upper fs does not support xattr.\n");
			} else {
				vfs_removexattr(ufs->workdir, OVL_XATTR_OPAQUE);
			}
1032 1033 1034 1035 1036 1037 1038

			/* Check if upper/work fs supports file handles */
			if (ufs->config.index &&
			    !ovl_can_decode_fh(ufs->workdir->d_sb)) {
				ufs->config.index = false;
				pr_warn("overlayfs: upper fs does not support file handles, falling back to index=off.\n");
			}
1039
		}
M
Miklos Szeredi 已提交
1040 1041
	}

1042
	err = -ENOMEM;
1043 1044 1045
	ufs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
				    GFP_KERNEL);
	if (ufs->lower_layers == NULL)
1046
		goto out_put_workdir;
1047
	for (i = 0; i < numlower; i++) {
1048
		struct vfsmount *mnt;
1049 1050 1051 1052 1053 1054 1055
		dev_t dev;

		err = get_anon_bdev(&dev);
		if (err) {
			pr_err("overlayfs: failed to get anonymous bdev for lowerpath\n");
			goto out_put_lower_layers;
		}
1056

1057
		mnt = clone_private_mount(&stack[i]);
1058
		err = PTR_ERR(mnt);
1059 1060
		if (IS_ERR(mnt)) {
			pr_err("overlayfs: failed to clone lowerpath\n");
1061
			free_anon_bdev(dev);
1062
			goto out_put_lower_layers;
1063 1064
		}
		/*
1065
		 * Make lower layers R/O.  That way fchmod/fchown on lower file
1066 1067
		 * will fail instead of modifying lower fs.
		 */
M
Miklos Szeredi 已提交
1068
		mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1069

1070
		ufs->lower_layers[ufs->numlower].mnt = mnt;
1071
		ufs->lower_layers[ufs->numlower].pseudo_dev = dev;
1072
		ufs->numlower++;
1073 1074 1075 1076 1077 1078

		/* Check if all lower layers are on same sb */
		if (i == 0)
			ufs->same_sb = mnt->mnt_sb;
		else if (ufs->same_sb != mnt->mnt_sb)
			ufs->same_sb = NULL;
1079
	}
M
Miklos Szeredi 已提交
1080

H
hujianyang 已提交
1081 1082
	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
	if (!ufs->upper_mnt)
M
Miklos Szeredi 已提交
1083
		sb->s_flags |= MS_RDONLY;
1084 1085
	else if (ufs->upper_mnt->mnt_sb != ufs->same_sb)
		ufs->same_sb = NULL;
M
Miklos Szeredi 已提交
1086

1087 1088 1089 1090 1091 1092 1093 1094 1095 1096
	err = -ENOMEM;
	oe = ovl_alloc_entry(numlower);
	if (!oe)
		goto out_put_lower_layers;

	for (i = 0; i < numlower; i++) {
		oe->lowerstack[i].dentry = stack[i].dentry;
		oe->lowerstack[i].layer = &(ufs->lower_layers[i]);
	}

1097
	if (!(ovl_force_readonly(ufs)) && ufs->config.index) {
1098
		/* Verify lower root is upper root origin */
1099 1100 1101 1102
		err = ovl_verify_origin(upperpath.dentry,
					oe->lowerstack[0].layer->mnt,
					oe->lowerstack[0].dentry,
					false, true);
1103 1104
		if (err) {
			pr_err("overlayfs: failed to verify upper root origin\n");
1105
			goto out_free_oe;
1106 1107
		}

1108 1109
		ufs->indexdir = ovl_workdir_create(sb, ufs, workpath.dentry,
						   OVL_INDEXDIR_NAME, true);
1110 1111 1112 1113 1114 1115
		if (ufs->indexdir) {
			/* Verify upper root is index dir origin */
			err = ovl_verify_origin(ufs->indexdir, ufs->upper_mnt,
						upperpath.dentry, true, true);
			if (err)
				pr_err("overlayfs: failed to verify index dir origin\n");
1116

1117
			/* Cleanup bad/stale/orphan index entries */
1118 1119 1120
			if (!err)
				err = ovl_indexdir_cleanup(ufs->indexdir,
							   ufs->upper_mnt,
1121 1122
							   oe->lowerstack,
							   numlower);
1123 1124
		}
		if (err || !ufs->indexdir)
1125
			pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1126 1127
		if (err)
			goto out_put_indexdir;
1128 1129 1130 1131 1132 1133
	}

	/* Show index=off/on in /proc/mounts for any of the reasons above */
	if (!ufs->indexdir)
		ufs->config.index = false;

1134 1135 1136 1137
	if (remote)
		sb->s_d_op = &ovl_reval_dentry_operations;
	else
		sb->s_d_op = &ovl_dentry_operations;
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1139
	err = -ENOMEM;
1140 1141
	ufs->creator_cred = cred = prepare_creds();
	if (!cred)
1142
		goto out_put_indexdir;
1143

1144 1145 1146
	/* Never override disk quota limits or use reserved space */
	cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);

1147 1148 1149 1150 1151 1152
	sb->s_magic = OVERLAYFS_SUPER_MAGIC;
	sb->s_op = &ovl_super_operations;
	sb->s_xattr = ovl_xattr_handlers;
	sb->s_fs_info = ufs;
	sb->s_flags |= MS_POSIXACL | MS_NOREMOTELOCK;

1153
	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
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	if (!root_dentry)
1155
		goto out_put_cred;
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1156 1157

	mntput(upperpath.mnt);
1158 1159
	for (i = 0; i < numlower; i++)
		mntput(stack[i].mnt);
1160
	kfree(stack);
1161
	mntput(workpath.mnt);
1162
	kfree(lowertmp);
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1163

1164
	if (upperpath.dentry) {
1165
		oe->has_upper = true;
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		if (ovl_is_impuredir(upperpath.dentry))
			ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1168
	}
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	root_dentry->d_fsdata = oe;

1172 1173
	/* Root is always merge -> can have whiteouts */
	ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1174 1175
	ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
		       ovl_dentry_lower(root_dentry));
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	sb->s_root = root_dentry;

	return 0;

1181 1182
out_put_cred:
	put_cred(ufs->creator_cred);
1183 1184
out_put_indexdir:
	dput(ufs->indexdir);
1185 1186 1187
out_free_oe:
	kfree(oe);
out_put_lower_layers:
1188 1189 1190
	for (i = 0; i < ufs->numlower; i++) {
		if (ufs->lower_layers[i].mnt)
			free_anon_bdev(ufs->lower_layers[i].pseudo_dev);
1191
		mntput(ufs->lower_layers[i].mnt);
1192
	}
1193
	kfree(ufs->lower_layers);
1194 1195
out_put_workdir:
	dput(ufs->workdir);
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	mntput(ufs->upper_mnt);
out_put_lowerpath:
1198 1199 1200 1201 1202
	for (i = 0; i < numlower; i++)
		path_put(&stack[i]);
	kfree(stack);
out_free_lowertmp:
	kfree(lowertmp);
1203
out_unlock_workdentry:
1204 1205
	if (ufs->workdir_locked)
		ovl_inuse_unlock(workpath.dentry);
1206 1207
out_put_workpath:
	path_put(&workpath);
1208
out_unlock_upperdentry:
1209 1210
	if (ufs->upperdir_locked)
		ovl_inuse_unlock(upperpath.dentry);
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1211 1212
	path_put(&upperpath);
out_free_config:
E
Erez Zadok 已提交
1213 1214 1215 1216
	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
	kfree(ufs);
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1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228
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,
1229
	.name		= "overlay",
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1230 1231 1232
	.mount		= ovl_mount,
	.kill_sb	= kill_anon_super,
};
1233
MODULE_ALIAS_FS("overlay");
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1234

1235 1236 1237 1238 1239 1240 1241
static void ovl_inode_init_once(void *foo)
{
	struct ovl_inode *oi = foo;

	inode_init_once(&oi->vfs_inode);
}

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1242 1243
static int __init ovl_init(void)
{
1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258
	int err;

	ovl_inode_cachep = kmem_cache_create("ovl_inode",
					     sizeof(struct ovl_inode), 0,
					     (SLAB_RECLAIM_ACCOUNT|
					      SLAB_MEM_SPREAD|SLAB_ACCOUNT),
					     ovl_inode_init_once);
	if (ovl_inode_cachep == NULL)
		return -ENOMEM;

	err = register_filesystem(&ovl_fs_type);
	if (err)
		kmem_cache_destroy(ovl_inode_cachep);

	return err;
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}

static void __exit ovl_exit(void)
{
	unregister_filesystem(&ovl_fs_type);
1264 1265 1266 1267 1268 1269 1270 1271

	/*
	 * Make sure all delayed rcu free inodes are flushed before we
	 * destroy cache.
	 */
	rcu_barrier();
	kmem_cache_destroy(ovl_inode_cachep);

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1272 1273 1274 1275
}

module_init(ovl_init);
module_exit(ovl_exit);