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.
 */

#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>
#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 <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");

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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;
}

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static void ovl_inode_init(struct inode *inode, struct inode *realinode,
			   bool is_upper)
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{
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	WRITE_ONCE(inode->i_private, (unsigned long) realinode |
		   (is_upper ? OVL_ISUPPER_MASK : 0));
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}

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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;
}

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

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void ovl_inode_update(struct inode *inode, struct inode *upperinode)
{
	WARN_ON(!upperinode);
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	WARN_ON(!inode_unhashed(inode));
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	WRITE_ONCE(inode->i_private,
		   (unsigned long) upperinode | OVL_ISUPPER_MASK);
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	if (!S_ISDIR(upperinode->i_mode))
		__insert_inode_hash(inode, (unsigned long) upperinode);
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}

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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,
				 const struct inode *inode,
				 unsigned int open_flags)
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{
	struct dentry *real;

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

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	if (d_is_negative(dentry))
		return dentry;

	if (open_flags) {
		int err = ovl_open_maybe_copy_up(dentry, open_flags);

		if (err)
			return ERR_PTR(err);
	}

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	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 */
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	return d_real(real, inode, open_flags);
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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 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 &
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		(DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
		 DCACHE_OP_REAL);
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}

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 super_block *ovl_sb,
					     struct dentry *dir,
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					     const struct qstr *name)
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{
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	const struct cred *old_cred;
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	struct dentry *dentry;

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	old_cred = ovl_override_creds(ovl_sb);
	dentry = lookup_one_len_unlocked(name->name, dir, name->len);
	revert_creds(old_cred);
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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(dentry->d_sb, upperdir, &dentry->d_name);
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		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];

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		this = ovl_lookup_real(dentry->d_sb,
				       lowerpath.dentry, &dentry->d_name);
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		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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		struct inode *realinode;
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		realdentry = upperdentry ? upperdentry : stack[0].dentry;
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		realinode = d_inode(realdentry);
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		err = -ENOMEM;
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		if (upperdentry && !d_is_dir(upperdentry)) {
			inode = ovl_get_inode(dentry->d_sb, realinode);
		} else {
			inode = ovl_new_inode(dentry->d_sb, realinode->i_mode);
			if (inode)
				ovl_inode_init(inode, realinode, !!upperdentry);
		}
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		if (!inode)
M
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587
			goto out_free_oe;
M
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588 589 590
		ovl_copyattr(realdentry->d_inode, inode);
	}

M
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591
	oe->opaque = upperopaque;
M
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592
	oe->__upperdentry = upperdentry;
M
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593 594
	memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr);
	kfree(stack);
M
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595 596 597 598 599
	dentry->d_fsdata = oe;
	d_add(dentry, inode);

	return NULL;

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600
out_free_oe:
M
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601
	kfree(oe);
M
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602 603 604 605 606 607
out_put:
	for (i = 0; i < ctr; i++)
		dput(stack[i].dentry);
	kfree(stack);
out_put_upper:
	dput(upperdentry);
M
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608 609 610 611 612 613
out:
	return ERR_PTR(err);
}

struct file *ovl_path_open(struct path *path, int flags)
{
M
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614
	return dentry_open(path, flags | O_NOATIME, current_cred());
M
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615 616 617 618 619
}

static void ovl_put_super(struct super_block *sb)
{
	struct ovl_fs *ufs = sb->s_fs_info;
620
	unsigned i;
M
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621 622 623

	dput(ufs->workdir);
	mntput(ufs->upper_mnt);
624 625
	for (i = 0; i < ufs->numlower; i++)
		mntput(ufs->lower_mnt[i]);
626
	kfree(ufs->lower_mnt);
M
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627

E
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628 629 630
	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
631
	put_cred(ufs->creator_cred);
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632 633 634
	kfree(ufs);
}

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635 636 637 638 639 640
/**
 * 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
641
 * filesystem pass the statfs to the upper filesystem (if it exists)
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642 643 644 645 646 647 648 649
 */
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;

650
	ovl_path_real(root_dentry, &path);
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Andy Whitcroft 已提交
651 652 653 654 655 656 657 658 659 660

	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;
}

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661 662 663 664 665 666 667 668 669 670 671
/**
 * 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;

672
	seq_show_option(m, "lowerdir", ufs->config.lowerdir);
M
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673
	if (ufs->config.upperdir) {
674 675
		seq_show_option(m, "upperdir", ufs->config.upperdir);
		seq_show_option(m, "workdir", ufs->config.workdir);
M
Miklos Szeredi 已提交
676
	}
M
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677 678
	if (ufs->config.default_permissions)
		seq_puts(m, ",default_permissions");
E
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679 680 681
	return 0;
}

682 683 684 685
static int ovl_remount(struct super_block *sb, int *flags, char *data)
{
	struct ovl_fs *ufs = sb->s_fs_info;

686
	if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
687 688 689 690 691
		return -EROFS;

	return 0;
}

M
Miklos Szeredi 已提交
692 693
static const struct super_operations ovl_super_operations = {
	.put_super	= ovl_put_super,
A
Andy Whitcroft 已提交
694
	.statfs		= ovl_statfs,
E
Erez Zadok 已提交
695
	.show_options	= ovl_show_options,
696
	.remount_fs	= ovl_remount,
M
Miklos Szeredi 已提交
697
	.drop_inode	= generic_delete_inode,
M
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698 699 700 701 702 703
};

enum {
	OPT_LOWERDIR,
	OPT_UPPERDIR,
	OPT_WORKDIR,
M
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704
	OPT_DEFAULT_PERMISSIONS,
M
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705 706 707 708 709 710 711
	OPT_ERR,
};

static const match_table_t ovl_tokens = {
	{OPT_LOWERDIR,			"lowerdir=%s"},
	{OPT_UPPERDIR,			"upperdir=%s"},
	{OPT_WORKDIR,			"workdir=%s"},
M
Miklos Szeredi 已提交
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	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
M
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713 714 715
	{OPT_ERR,			NULL}
};

M
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716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738
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
Miklos Szeredi 已提交
739 740 741 742
static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
	char *p;

M
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743
	while ((p = ovl_next_opt(&opt)) != NULL) {
M
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744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772
		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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773 774 775 776
		case OPT_DEFAULT_PERMISSIONS:
			config->default_permissions = true;
			break;

M
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777
		default:
778
			pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
M
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779 780 781
			return -EINVAL;
		}
	}
H
hujianyang 已提交
782 783 784 785 786 787 788 789 790

	/* 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;
	}

M
Miklos Szeredi 已提交
791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807
	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
808
	inode_lock_nested(dir, I_MUTEX_PARENT);
M
Miklos Szeredi 已提交
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,
		};
817 818 819 820
		struct iattr attr = {
			.ia_valid = ATTR_MODE,
			.ia_mode = stat.mode,
		};
M
Miklos Szeredi 已提交
821 822 823 824 825 826 827

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

			retried = true;
M
Miklos Szeredi 已提交
828
			ovl_workdir_cleanup(dir, mnt, work, 0);
M
Miklos Szeredi 已提交
829 830 831 832 833 834 835
			dput(work);
			goto retry;
		}

		err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
		if (err)
			goto out_dput;
836 837 838 839 840 841 842 843 844 845 846 847 848 849 850

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

		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
		if (err && err != -ENODATA)
			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;
M
Miklos Szeredi 已提交
851 852
	}
out_unlock:
A
Al Viro 已提交
853
	inode_unlock(dir);
M
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854 855 856 857 858 859 860 861 862 863
	mnt_drop_write(mnt);

	return work;

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

M
Miklos Szeredi 已提交
864 865 866 867 868 869 870 871 872 873 874 875 876
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
877 878
static int ovl_mount_dir_noesc(const char *name, struct path *path)
{
879
	int err = -EINVAL;
M
Miklos Szeredi 已提交
880

881 882 883 884
	if (!*name) {
		pr_err("overlayfs: empty lowerdir\n");
		goto out;
	}
M
Miklos Szeredi 已提交
885 886 887 888 889 890
	err = kern_path(name, LOOKUP_FOLLOW, path);
	if (err) {
		pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
		goto out;
	}
	err = -EINVAL;
891
	if (ovl_dentry_weird(path->dentry)) {
M
Miklos Szeredi 已提交
892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914
		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);
915 916 917 918 919 920 921 922

		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
923 924 925 926 927 928
		kfree(tmp);
	}
	return err;
}

static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
929
			 int *stack_depth, bool *remote)
M
Miklos Szeredi 已提交
930 931 932 933
{
	int err;
	struct kstatfs statfs;

934
	err = ovl_mount_dir_noesc(name, path);
M
Miklos Szeredi 已提交
935 936 937 938 939 940 941 942 943 944 945
	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);

946 947 948
	if (ovl_dentry_remote(path->dentry))
		*remote = true;

M
Miklos Szeredi 已提交
949 950 951 952 953 954 955 956
	return 0;

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

M
Miklos Szeredi 已提交
957 958 959 960 961 962 963 964 965 966 967 968
/* 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;
}

969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988
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
989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078
static int 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)
{
	struct dentry *workdir = ovl_workdir(dentry);
	struct inode *realinode = ovl_inode_real(inode, NULL);
	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);

	return ovl_setxattr(dentry, inode, handler->name, value, size, flags);

out_acl_release:
	posix_acl_release(acl);
	return err;
}

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)
{
	return ovl_setxattr(dentry, inode, name, value, size, flags);
}

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)
{
	return -EPERM;
}

static const struct xattr_handler ovl_posix_acl_access_xattr_handler = {
	.name = XATTR_NAME_POSIX_ACL_ACCESS,
	.flags = ACL_TYPE_ACCESS,
	.set = ovl_posix_acl_xattr_set,
};

static const struct xattr_handler ovl_posix_acl_default_xattr_handler = {
	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
	.flags = ACL_TYPE_DEFAULT,
	.set = ovl_posix_acl_xattr_set,
};

static const struct xattr_handler ovl_own_xattr_handler = {
	.prefix	= OVL_XATTR_PREFIX,
	.set = ovl_own_xattr_set,
};

static const struct xattr_handler ovl_other_xattr_handler = {
	.prefix	= "", /* catch all */
	.set = ovl_other_xattr_set,
};

static const struct xattr_handler *ovl_xattr_handlers[] = {
	&ovl_posix_acl_access_xattr_handler,
	&ovl_posix_acl_default_xattr_handler,
	&ovl_own_xattr_handler,
	&ovl_other_xattr_handler,
	NULL
};

static const struct xattr_handler *ovl_xattr_noacl_handlers[] = {
	&ovl_own_xattr_handler,
	&ovl_other_xattr_handler,
	NULL,
};

M
Miklos Szeredi 已提交
1079 1080
static int ovl_fill_super(struct super_block *sb, void *data, int silent)
{
M
Miklos Szeredi 已提交
1081 1082
	struct path upperpath = { NULL, NULL };
	struct path workpath = { NULL, NULL };
M
Miklos Szeredi 已提交
1083
	struct dentry *root_dentry;
1084
	struct inode *realinode;
M
Miklos Szeredi 已提交
1085 1086
	struct ovl_entry *oe;
	struct ovl_fs *ufs;
1087 1088 1089 1090 1091
	struct path *stack = NULL;
	char *lowertmp;
	char *lower;
	unsigned int numlower;
	unsigned int stacklen = 0;
1092
	unsigned int i;
1093
	bool remote = false;
M
Miklos Szeredi 已提交
1094 1095
	int err;

E
Erez Zadok 已提交
1096 1097 1098
	err = -ENOMEM;
	ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
	if (!ufs)
M
Miklos Szeredi 已提交
1099 1100
		goto out;

E
Erez Zadok 已提交
1101 1102 1103 1104
	err = ovl_parse_opt((char *) data, &ufs->config);
	if (err)
		goto out_free_config;

M
Miklos Szeredi 已提交
1105
	err = -EINVAL;
M
Miklos Szeredi 已提交
1106
	if (!ufs->config.lowerdir) {
1107 1108
		if (!silent)
			pr_err("overlayfs: missing 'lowerdir'\n");
M
Miklos Szeredi 已提交
1109 1110 1111
		goto out_free_config;
	}

M
Miklos Szeredi 已提交
1112
	sb->s_stack_depth = 0;
1113
	sb->s_maxbytes = MAX_LFS_FILESIZE;
M
Miklos Szeredi 已提交
1114 1115 1116 1117 1118
	if (ufs->config.upperdir) {
		if (!ufs->config.workdir) {
			pr_err("overlayfs: missing 'workdir'\n");
			goto out_free_config;
		}
M
Miklos Szeredi 已提交
1119

M
Miklos Szeredi 已提交
1120 1121 1122
		err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
		if (err)
			goto out_free_config;
M
Miklos Szeredi 已提交
1123

H
hujianyang 已提交
1124 1125 1126 1127 1128 1129 1130
		/* 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
1131 1132 1133 1134
		err = ovl_mount_dir(ufs->config.workdir, &workpath);
		if (err)
			goto out_put_upperpath;

1135
		err = -EINVAL;
M
Miklos Szeredi 已提交
1136 1137 1138 1139 1140 1141 1142 1143 1144
		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
1145
	}
1146 1147 1148
	err = -ENOMEM;
	lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
	if (!lowertmp)
M
Miklos Szeredi 已提交
1149
		goto out_put_workpath;
1150

1151 1152
	err = -EINVAL;
	stacklen = ovl_split_lowerdirs(lowertmp);
1153
	if (stacklen > OVL_MAX_STACK) {
1154
		pr_err("overlayfs: too many lower directories, limit is %d\n",
1155
		       OVL_MAX_STACK);
1156
		goto out_free_lowertmp;
1157 1158 1159 1160
	} else if (!ufs->config.upperdir && stacklen == 1) {
		pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
		goto out_free_lowertmp;
	}
1161 1162 1163 1164 1165 1166 1167 1168

	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],
1169 1170
				    &ufs->lower_namelen, &sb->s_stack_depth,
				    &remote);
1171 1172 1173 1174 1175 1176
		if (err)
			goto out_put_lowerpath;

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

1177
	err = -EINVAL;
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Miklos Szeredi 已提交
1178
	sb->s_stack_depth++;
1179 1180
	if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
		pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1181
		goto out_put_lowerpath;
1182 1183
	}

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1184 1185 1186 1187 1188 1189 1190
	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;
		}
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1191 1192 1193 1194
		/* 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;
1195

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1196 1197 1198
		ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
		err = PTR_ERR(ufs->workdir);
		if (IS_ERR(ufs->workdir)) {
1199 1200 1201 1202
			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
1203
		}
1204 1205 1206 1207

		/*
		 * Upper should support d_type, else whiteouts are visible.
		 * Given workdir and upper are on same fs, we can do
1208 1209
		 * iterate_dir() on workdir. This check requires successful
		 * creation of workdir in previous step.
1210
		 */
1211 1212 1213 1214
		if (ufs->workdir) {
			err = ovl_check_d_type_supported(&workpath);
			if (err < 0)
				goto out_put_workdir;
1215

1216 1217 1218 1219 1220 1221 1222
			/*
			 * 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");
1223
		}
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1224 1225
	}

1226
	err = -ENOMEM;
1227
	ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
1228
	if (ufs->lower_mnt == NULL)
1229
		goto out_put_workdir;
1230 1231
	for (i = 0; i < numlower; i++) {
		struct vfsmount *mnt = clone_private_mount(&stack[i]);
1232

1233
		err = PTR_ERR(mnt);
1234 1235 1236 1237 1238 1239 1240 1241
		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.
		 */
M
Miklos Szeredi 已提交
1242
		mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1243

1244 1245 1246
		ufs->lower_mnt[ufs->numlower] = mnt;
		ufs->numlower++;
	}
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Miklos Szeredi 已提交
1247

H
hujianyang 已提交
1248 1249
	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
	if (!ufs->upper_mnt)
M
Miklos Szeredi 已提交
1250 1251
		sb->s_flags |= MS_RDONLY;

1252 1253 1254 1255
	if (remote)
		sb->s_d_op = &ovl_reval_dentry_operations;
	else
		sb->s_d_op = &ovl_dentry_operations;
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1256

1257 1258 1259 1260
	ufs->creator_cred = prepare_creds();
	if (!ufs->creator_cred)
		goto out_put_lower_mnt;

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Miklos Szeredi 已提交
1261
	err = -ENOMEM;
1262
	oe = ovl_alloc_entry(numlower);
1263
	if (!oe)
1264
		goto out_put_cred;
M
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1265

1266
	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR));
M
Miklos Szeredi 已提交
1267
	if (!root_dentry)
1268
		goto out_free_oe;
M
Miklos Szeredi 已提交
1269 1270

	mntput(upperpath.mnt);
1271 1272
	for (i = 0; i < numlower; i++)
		mntput(stack[i].mnt);
M
Miklos Szeredi 已提交
1273
	path_put(&workpath);
1274
	kfree(lowertmp);
M
Miklos Szeredi 已提交
1275 1276

	oe->__upperdentry = upperpath.dentry;
1277 1278 1279 1280
	for (i = 0; i < numlower; i++) {
		oe->lowerstack[i].dentry = stack[i].dentry;
		oe->lowerstack[i].mnt = ufs->lower_mnt[i];
	}
1281
	kfree(stack);
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Miklos Szeredi 已提交
1282 1283 1284

	root_dentry->d_fsdata = oe;

1285 1286 1287
	realinode = d_inode(ovl_dentry_real(root_dentry));
	ovl_inode_init(d_inode(root_dentry), realinode, !!upperpath.dentry);
	ovl_copyattr(realinode, d_inode(root_dentry));
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Miklos Szeredi 已提交
1288

A
Andy Whitcroft 已提交
1289
	sb->s_magic = OVERLAYFS_SUPER_MAGIC;
M
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1290
	sb->s_op = &ovl_super_operations;
M
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1291 1292 1293 1294
	if (IS_ENABLED(CONFIG_FS_POSIX_ACL))
		sb->s_xattr = ovl_xattr_handlers;
	else
		sb->s_xattr = ovl_xattr_noacl_handlers;
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Miklos Szeredi 已提交
1295 1296
	sb->s_root = root_dentry;
	sb->s_fs_info = ufs;
1297
	sb->s_flags |= MS_POSIXACL;
M
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1298 1299 1300

	return 0;

1301 1302
out_free_oe:
	kfree(oe);
1303 1304
out_put_cred:
	put_cred(ufs->creator_cred);
M
Miklos Szeredi 已提交
1305
out_put_lower_mnt:
1306 1307 1308
	for (i = 0; i < ufs->numlower; i++)
		mntput(ufs->lower_mnt[i]);
	kfree(ufs->lower_mnt);
1309 1310
out_put_workdir:
	dput(ufs->workdir);
M
Miklos Szeredi 已提交
1311 1312
	mntput(ufs->upper_mnt);
out_put_lowerpath:
1313 1314 1315 1316 1317
	for (i = 0; i < numlower; i++)
		path_put(&stack[i]);
	kfree(stack);
out_free_lowertmp:
	kfree(lowertmp);
1318 1319
out_put_workpath:
	path_put(&workpath);
M
Miklos Szeredi 已提交
1320 1321 1322
out_put_upperpath:
	path_put(&upperpath);
out_free_config:
E
Erez Zadok 已提交
1323 1324 1325 1326
	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
	kfree(ufs);
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1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338
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,
1339
	.name		= "overlay",
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Miklos Szeredi 已提交
1340 1341 1342
	.mount		= ovl_mount,
	.kill_sb	= kill_anon_super,
};
1343
MODULE_ALIAS_FS("overlay");
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1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356

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);