super.c 30.7 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;
}

863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897
static int ovl_get_workpath(struct ovl_fs *ufs, struct path *upperpath,
			    struct path *workpath)
{
	int err;

	err = ovl_mount_dir(ufs->config.workdir, workpath);
	if (err)
		goto out;

	err = -EINVAL;
	if (upperpath->mnt != workpath->mnt) {
		pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
		goto out;
	}
	if (!ovl_workdir_ok(workpath->dentry, upperpath->dentry)) {
		pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
		goto out;
	}

	err = -EBUSY;
	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");
		goto out;
	} else {
		pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n");
	}

	ufs->workbasedir = workpath->dentry;
	err = 0;
out:
	return err;
}

898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914
static int ovl_get_upper(struct ovl_fs *ufs, struct path *upperpath)
{
	struct vfsmount *upper_mnt;

	upper_mnt = clone_private_mount(upperpath);
	if (IS_ERR(upper_mnt)) {
		pr_err("overlayfs: failed to clone upperpath\n");
		return PTR_ERR(upper_mnt);
	}

	/* Don't inherit atime flags */
	upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
	ufs->upper_mnt = upper_mnt;

	return 0;
}

915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983
static int ovl_get_lowerstack(struct super_block *sb, struct ovl_fs *ufs,
			      struct path **stackp, unsigned int *stacklenp)
{
	int err;
	char *lowertmp, *lower;
	struct path *stack;
	unsigned int stacklen, numlower, i;
	bool remote = false;

	err = -ENOMEM;
	lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
	if (!lowertmp)
		goto out;

	err = -EINVAL;
	stacklen = ovl_split_lowerdirs(lowertmp);
	if (stacklen > OVL_MAX_STACK) {
		pr_err("overlayfs: too many lower directories, limit is %d\n",
		       OVL_MAX_STACK);
		goto out;
	} else if (!ufs->config.upperdir && stacklen == 1) {
		pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
		goto out;
	}

	err = -ENOMEM;
	stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
	if (!stack)
		goto out;

	err = -EINVAL;
	lower = lowertmp;
	for (numlower = 0; numlower < stacklen; numlower++) {
		err = ovl_lower_dir(lower, &stack[numlower], ufs,
				    &sb->s_stack_depth, &remote);
		if (err)
			goto out_free_stack;

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

	err = -EINVAL;
	sb->s_stack_depth++;
	if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
		pr_err("overlayfs: maximum fs stacking depth exceeded\n");
		goto out_free_stack;
	}

	*stackp = stack;
	*stacklenp = numlower;

	if (remote)
		sb->s_d_op = &ovl_reval_dentry_operations;
	else
		sb->s_d_op = &ovl_dentry_operations;

	err = 0;

out:
	kfree(lowertmp);
	return err;

out_free_stack:
	for (i = 0; i < numlower; i++)
		path_put(&stack[i]);
	kfree(stack);
	goto out;
}

M
Miklos Szeredi 已提交
984 985
static int ovl_fill_super(struct super_block *sb, void *data, int silent)
{
K
Kees Cook 已提交
986 987
	struct path upperpath = { };
	struct path workpath = { };
M
Miklos Szeredi 已提交
988 989 990
	struct dentry *root_dentry;
	struct ovl_entry *oe;
	struct ovl_fs *ufs;
991
	struct path *stack = NULL;
992
	unsigned int numlower = 0;
993
	unsigned int i;
994
	struct cred *cred;
M
Miklos Szeredi 已提交
995 996
	int err;

E
Erez Zadok 已提交
997 998 999
	err = -ENOMEM;
	ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
	if (!ufs)
M
Miklos Szeredi 已提交
1000 1001
		goto out;

1002
	ufs->config.redirect_dir = ovl_redirect_dir_def;
1003
	ufs->config.index = ovl_index_def;
E
Erez Zadok 已提交
1004 1005 1006 1007
	err = ovl_parse_opt((char *) data, &ufs->config);
	if (err)
		goto out_free_config;

M
Miklos Szeredi 已提交
1008
	err = -EINVAL;
M
Miklos Szeredi 已提交
1009
	if (!ufs->config.lowerdir) {
1010 1011
		if (!silent)
			pr_err("overlayfs: missing 'lowerdir'\n");
M
Miklos Szeredi 已提交
1012 1013 1014
		goto out_free_config;
	}

M
Miklos Szeredi 已提交
1015
	sb->s_stack_depth = 0;
1016
	sb->s_maxbytes = MAX_LFS_FILESIZE;
M
Miklos Szeredi 已提交
1017 1018 1019 1020 1021
	if (ufs->config.upperdir) {
		if (!ufs->config.workdir) {
			pr_err("overlayfs: missing 'workdir'\n");
			goto out_free_config;
		}
M
Miklos Szeredi 已提交
1022

1023
		err = ovl_get_upperpath(ufs, &upperpath);
M
Miklos Szeredi 已提交
1024
		if (err)
1025
			goto out_unlock_upperdentry;
1026

1027
		err = ovl_get_workpath(ufs, &upperpath, &workpath);
M
Miklos Szeredi 已提交
1028
		if (err)
1029
			goto out_unlock_workdentry;
1030

M
Miklos Szeredi 已提交
1031
		sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
A
Andy Whitcroft 已提交
1032
	}
1033 1034
	err = ovl_get_lowerstack(sb, ufs, &stack, &numlower);
	if (err)
1035
		goto out_unlock_workdentry;
1036

M
Miklos Szeredi 已提交
1037
	if (ufs->config.upperdir) {
1038 1039
		err = ovl_get_upper(ufs, &upperpath);
		if (err)
M
Miklos Szeredi 已提交
1040
			goto out_put_lowerpath;
M
Miklos Szeredi 已提交
1041 1042

		sb->s_time_gran = ufs->upper_mnt->mnt_sb->s_time_gran;
1043

1044 1045
		ufs->workdir = ovl_workdir_create(sb, ufs, workpath.dentry,
						  OVL_WORKDIR_NAME, false);
1046 1047 1048
		/*
		 * Upper should support d_type, else whiteouts are visible.
		 * Given workdir and upper are on same fs, we can do
1049 1050
		 * iterate_dir() on workdir. This check requires successful
		 * creation of workdir in previous step.
1051
		 */
1052
		if (ufs->workdir) {
1053 1054
			struct dentry *temp;

1055 1056 1057
			err = ovl_check_d_type_supported(&workpath);
			if (err < 0)
				goto out_put_workdir;
1058

1059 1060 1061 1062 1063 1064 1065
			/*
			 * 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");
1066 1067 1068 1069 1070 1071 1072 1073

			/* 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");
1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086

			/*
			 * 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);
			}
1087 1088 1089 1090 1091 1092 1093

			/* 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");
			}
1094
		}
M
Miklos Szeredi 已提交
1095 1096
	}

1097
	err = -ENOMEM;
1098 1099 1100
	ufs->lower_layers = kcalloc(numlower, sizeof(struct ovl_layer),
				    GFP_KERNEL);
	if (ufs->lower_layers == NULL)
1101
		goto out_put_workdir;
1102
	for (i = 0; i < numlower; i++) {
1103
		struct vfsmount *mnt;
1104 1105 1106 1107 1108 1109 1110
		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;
		}
1111

1112
		mnt = clone_private_mount(&stack[i]);
1113
		err = PTR_ERR(mnt);
1114 1115
		if (IS_ERR(mnt)) {
			pr_err("overlayfs: failed to clone lowerpath\n");
1116
			free_anon_bdev(dev);
1117
			goto out_put_lower_layers;
1118 1119
		}
		/*
1120
		 * Make lower layers R/O.  That way fchmod/fchown on lower file
1121 1122
		 * will fail instead of modifying lower fs.
		 */
M
Miklos Szeredi 已提交
1123
		mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1124

1125
		ufs->lower_layers[ufs->numlower].mnt = mnt;
1126
		ufs->lower_layers[ufs->numlower].pseudo_dev = dev;
1127
		ufs->numlower++;
1128 1129 1130 1131 1132 1133

		/* 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;
1134
	}
M
Miklos Szeredi 已提交
1135

H
hujianyang 已提交
1136 1137
	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
	if (!ufs->upper_mnt)
M
Miklos Szeredi 已提交
1138
		sb->s_flags |= MS_RDONLY;
1139 1140
	else if (ufs->upper_mnt->mnt_sb != ufs->same_sb)
		ufs->same_sb = NULL;
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1142 1143 1144 1145 1146 1147 1148 1149 1150 1151
	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]);
	}

1152
	if (!(ovl_force_readonly(ufs)) && ufs->config.index) {
1153
		/* Verify lower root is upper root origin */
1154 1155 1156 1157
		err = ovl_verify_origin(upperpath.dentry,
					oe->lowerstack[0].layer->mnt,
					oe->lowerstack[0].dentry,
					false, true);
1158 1159
		if (err) {
			pr_err("overlayfs: failed to verify upper root origin\n");
1160
			goto out_free_oe;
1161 1162
		}

1163 1164
		ufs->indexdir = ovl_workdir_create(sb, ufs, workpath.dentry,
						   OVL_INDEXDIR_NAME, true);
1165 1166 1167 1168 1169 1170
		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");
1171

1172
			/* Cleanup bad/stale/orphan index entries */
1173 1174 1175
			if (!err)
				err = ovl_indexdir_cleanup(ufs->indexdir,
							   ufs->upper_mnt,
1176 1177
							   oe->lowerstack,
							   numlower);
1178 1179
		}
		if (err || !ufs->indexdir)
1180
			pr_warn("overlayfs: try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
1181 1182
		if (err)
			goto out_put_indexdir;
1183 1184 1185 1186 1187 1188
	}

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

1189
	err = -ENOMEM;
1190 1191
	ufs->creator_cred = cred = prepare_creds();
	if (!cred)
1192
		goto out_put_indexdir;
1193

1194 1195 1196
	/* Never override disk quota limits or use reserved space */
	cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);

1197 1198 1199 1200 1201 1202
	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;

1203
	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
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	if (!root_dentry)
1205
		goto out_put_cred;
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1206 1207

	mntput(upperpath.mnt);
1208 1209
	for (i = 0; i < numlower; i++)
		mntput(stack[i].mnt);
1210
	kfree(stack);
1211
	mntput(workpath.mnt);
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1212

1213
	if (upperpath.dentry) {
1214
		oe->has_upper = true;
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		if (ovl_is_impuredir(upperpath.dentry))
			ovl_set_flag(OVL_IMPURE, d_inode(root_dentry));
1217
	}
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1218 1219 1220

	root_dentry->d_fsdata = oe;

1221 1222
	/* Root is always merge -> can have whiteouts */
	ovl_set_flag(OVL_WHITEOUTS, d_inode(root_dentry));
1223 1224
	ovl_inode_init(d_inode(root_dentry), upperpath.dentry,
		       ovl_dentry_lower(root_dentry));
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1225

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1226 1227 1228 1229
	sb->s_root = root_dentry;

	return 0;

1230 1231
out_put_cred:
	put_cred(ufs->creator_cred);
1232 1233
out_put_indexdir:
	dput(ufs->indexdir);
1234 1235 1236
out_free_oe:
	kfree(oe);
out_put_lower_layers:
1237 1238 1239
	for (i = 0; i < ufs->numlower; i++) {
		if (ufs->lower_layers[i].mnt)
			free_anon_bdev(ufs->lower_layers[i].pseudo_dev);
1240
		mntput(ufs->lower_layers[i].mnt);
1241
	}
1242
	kfree(ufs->lower_layers);
1243 1244
out_put_workdir:
	dput(ufs->workdir);
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1245 1246
	mntput(ufs->upper_mnt);
out_put_lowerpath:
1247 1248 1249
	for (i = 0; i < numlower; i++)
		path_put(&stack[i]);
	kfree(stack);
1250
out_unlock_workdentry:
1251 1252
	if (ufs->workdir_locked)
		ovl_inuse_unlock(workpath.dentry);
1253
	path_put(&workpath);
1254
out_unlock_upperdentry:
1255 1256
	if (ufs->upperdir_locked)
		ovl_inuse_unlock(upperpath.dentry);
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1257 1258
	path_put(&upperpath);
out_free_config:
E
Erez Zadok 已提交
1259 1260 1261 1262
	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
	kfree(ufs);
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1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274
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,
1275
	.name		= "overlay",
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1276 1277 1278
	.mount		= ovl_mount,
	.kill_sb	= kill_anon_super,
};
1279
MODULE_ALIAS_FS("overlay");
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1280

1281 1282 1283 1284 1285 1286 1287
static void ovl_inode_init_once(void *foo)
{
	struct ovl_inode *oi = foo;

	inode_init_once(&oi->vfs_inode);
}

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1288 1289
static int __init ovl_init(void)
{
1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304
	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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1305 1306 1307 1308 1309
}

static void __exit ovl_exit(void)
{
	unregister_filesystem(&ovl_fs_type);
1310 1311 1312 1313 1314 1315 1316 1317

	/*
	 * 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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1318 1319 1320 1321
}

module_init(ovl_init);
module_exit(ovl_exit);