super.c 30.6 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;

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	if (!d_is_dir(dentry))
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		return false;

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	res = vfs_getxattr(dentry, 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 dentry *dir,
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					     const struct qstr *name)
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{
	struct dentry *dentry;

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	dentry = lookup_one_len_unlocked(name->name, dir, name->len);
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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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	const struct cred *old_cred;
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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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	old_cred = ovl_override_creds(dentry->d_sb);
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	upperdir = ovl_upperdentry_dereference(poe);
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	if (upperdir) {
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		this = ovl_lookup_real(upperdir, &dentry->d_name);
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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(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)
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			goto out_free_oe;
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		ovl_copyattr(realdentry->d_inode, inode);
	}

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

	return NULL;

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out_free_oe:
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	kfree(oe);
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out_put:
	for (i = 0; i < ctr; i++)
		dput(stack[i].dentry);
	kfree(stack);
out_put_upper:
	dput(upperdentry);
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605
out:
606
	revert_creds(old_cred);
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607 608 609 610 611
	return ERR_PTR(err);
}

struct file *ovl_path_open(struct path *path, int flags)
{
612
	return dentry_open(path, flags | O_NOATIME, current_cred());
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}

static void ovl_put_super(struct super_block *sb)
{
	struct ovl_fs *ufs = sb->s_fs_info;
618
	unsigned i;
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619 620 621

	dput(ufs->workdir);
	mntput(ufs->upper_mnt);
622 623
	for (i = 0; i < ufs->numlower; i++)
		mntput(ufs->lower_mnt[i]);
624
	kfree(ufs->lower_mnt);
M
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625

626 627 628
	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
629
	put_cred(ufs->creator_cred);
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630 631 632
	kfree(ufs);
}

633 634 635 636 637 638
/**
 * 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
639
 * filesystem pass the statfs to the upper filesystem (if it exists)
640 641 642 643 644 645 646 647
 */
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;

648
	ovl_path_real(root_dentry, &path);
649 650 651 652 653 654 655 656 657 658

	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;
}

659 660 661 662 663 664 665 666 667 668 669
/**
 * 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;

670
	seq_show_option(m, "lowerdir", ufs->config.lowerdir);
671
	if (ufs->config.upperdir) {
672 673
		seq_show_option(m, "upperdir", ufs->config.upperdir);
		seq_show_option(m, "workdir", ufs->config.workdir);
674
	}
675 676
	if (ufs->config.default_permissions)
		seq_puts(m, ",default_permissions");
677 678 679
	return 0;
}

680 681 682 683
static int ovl_remount(struct super_block *sb, int *flags, char *data)
{
	struct ovl_fs *ufs = sb->s_fs_info;

684
	if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
685 686 687 688 689
		return -EROFS;

	return 0;
}

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690 691
static const struct super_operations ovl_super_operations = {
	.put_super	= ovl_put_super,
692
	.statfs		= ovl_statfs,
693
	.show_options	= ovl_show_options,
694
	.remount_fs	= ovl_remount,
695
	.drop_inode	= generic_delete_inode,
M
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696 697 698 699 700 701
};

enum {
	OPT_LOWERDIR,
	OPT_UPPERDIR,
	OPT_WORKDIR,
702
	OPT_DEFAULT_PERMISSIONS,
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703 704 705 706 707 708 709
	OPT_ERR,
};

static const match_table_t ovl_tokens = {
	{OPT_LOWERDIR,			"lowerdir=%s"},
	{OPT_UPPERDIR,			"upperdir=%s"},
	{OPT_WORKDIR,			"workdir=%s"},
710
	{OPT_DEFAULT_PERMISSIONS,	"default_permissions"},
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711 712 713
	{OPT_ERR,			NULL}
};

714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736
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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737 738 739 740
static int ovl_parse_opt(char *opt, struct ovl_config *config)
{
	char *p;

741
	while ((p = ovl_next_opt(&opt)) != NULL) {
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742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770
		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;

771 772 773 774
		case OPT_DEFAULT_PERMISSIONS:
			config->default_permissions = true;
			break;

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775
		default:
776
			pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
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777 778 779
			return -EINVAL;
		}
	}
780 781 782 783 784 785 786 787 788

	/* 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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789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805
	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
806
	inode_lock_nested(dir, I_MUTEX_PARENT);
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807 808 809 810 811 812 813 814
retry:
	work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
			      strlen(OVL_WORKDIR_NAME));

	if (!IS_ERR(work)) {
		struct kstat stat = {
			.mode = S_IFDIR | 0,
		};
815 816 817 818
		struct iattr attr = {
			.ia_valid = ATTR_MODE,
			.ia_mode = stat.mode,
		};
M
Miklos Szeredi 已提交
819 820 821 822 823 824 825

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

			retried = true;
826
			ovl_workdir_cleanup(dir, mnt, work, 0);
M
Miklos Szeredi 已提交
827 828 829 830 831 832 833
			dput(work);
			goto retry;
		}

		err = ovl_create_real(dir, work, &stat, NULL, NULL, true);
		if (err)
			goto out_dput;
834 835

		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
836
		if (err && err != -ENODATA && err != -EOPNOTSUPP)
837 838 839
			goto out_dput;

		err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
840
		if (err && err != -ENODATA && err != -EOPNOTSUPP)
841 842 843 844 845 846 847 848
			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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849 850
	}
out_unlock:
A
Al Viro 已提交
851
	inode_unlock(dir);
M
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852 853 854 855 856 857 858 859 860 861
	mnt_drop_write(mnt);

	return work;

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

862 863 864 865 866 867 868 869 870 871 872 873 874
static void ovl_unescape(char *s)
{
	char *d = s;

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

875 876
static int ovl_mount_dir_noesc(const char *name, struct path *path)
{
877
	int err = -EINVAL;
878

879 880 881 882
	if (!*name) {
		pr_err("overlayfs: empty lowerdir\n");
		goto out;
	}
883 884 885 886 887 888
	err = kern_path(name, LOOKUP_FOLLOW, path);
	if (err) {
		pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
		goto out;
	}
	err = -EINVAL;
889
	if (ovl_dentry_weird(path->dentry)) {
890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912
		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);
913 914 915 916 917 918 919 920

		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;
			}
921 922 923 924 925 926
		kfree(tmp);
	}
	return err;
}

static int ovl_lower_dir(const char *name, struct path *path, long *namelen,
927
			 int *stack_depth, bool *remote)
928 929 930 931
{
	int err;
	struct kstatfs statfs;

932
	err = ovl_mount_dir_noesc(name, path);
933 934 935 936 937 938 939 940 941 942 943
	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);

944 945 946
	if (ovl_dentry_remote(path->dentry))
		*remote = true;

947 948 949 950 951 952 953 954
	return 0;

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

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955 956 957 958 959 960 961 962 963 964 965 966
/* 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;
}

967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986
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;
}

987 988 989 990 991 992 993 994
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)
{
	return ovl_xattr_get(dentry, handler->name, buffer, size);
}

995 996 997 998 999
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)
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
{
	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);

1027 1028 1029 1030 1031
	err = ovl_xattr_set(dentry, handler->name, value, size, flags);
	if (!err)
		ovl_copyattr(ovl_inode_real(inode, NULL), inode);

	return err;
1032 1033 1034 1035 1036 1037

out_acl_release:
	posix_acl_release(acl);
	return err;
}

1038 1039 1040 1041 1042 1043 1044
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)
{
	return -EPERM;
}

1045 1046 1047 1048 1049 1050 1051 1052
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;
}

1053 1054 1055 1056 1057 1058 1059
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)
{
	return ovl_xattr_get(dentry, name, buffer, size);
}

1060 1061 1062 1063 1064 1065 1066 1067
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_xattr_set(dentry, name, value, size, flags);
}

1068 1069
static const struct xattr_handler __maybe_unused
ovl_posix_acl_access_xattr_handler = {
1070 1071
	.name = XATTR_NAME_POSIX_ACL_ACCESS,
	.flags = ACL_TYPE_ACCESS,
1072
	.get = ovl_posix_acl_xattr_get,
1073 1074 1075
	.set = ovl_posix_acl_xattr_set,
};

1076 1077
static const struct xattr_handler __maybe_unused
ovl_posix_acl_default_xattr_handler = {
1078 1079
	.name = XATTR_NAME_POSIX_ACL_DEFAULT,
	.flags = ACL_TYPE_DEFAULT,
1080
	.get = ovl_posix_acl_xattr_get,
1081 1082 1083 1084 1085
	.set = ovl_posix_acl_xattr_set,
};

static const struct xattr_handler ovl_own_xattr_handler = {
	.prefix	= OVL_XATTR_PREFIX,
1086
	.get = ovl_own_xattr_get,
1087 1088 1089 1090 1091
	.set = ovl_own_xattr_set,
};

static const struct xattr_handler ovl_other_xattr_handler = {
	.prefix	= "", /* catch all */
1092
	.get = ovl_other_xattr_get,
1093 1094 1095 1096
	.set = ovl_other_xattr_set,
};

static const struct xattr_handler *ovl_xattr_handlers[] = {
1097
#ifdef CONFIG_FS_POSIX_ACL
1098 1099
	&ovl_posix_acl_access_xattr_handler,
	&ovl_posix_acl_default_xattr_handler,
1100
#endif
1101 1102 1103 1104 1105
	&ovl_own_xattr_handler,
	&ovl_other_xattr_handler,
	NULL
};

M
Miklos Szeredi 已提交
1106 1107
static int ovl_fill_super(struct super_block *sb, void *data, int silent)
{
1108 1109
	struct path upperpath = { NULL, NULL };
	struct path workpath = { NULL, NULL };
M
Miklos Szeredi 已提交
1110
	struct dentry *root_dentry;
1111
	struct inode *realinode;
M
Miklos Szeredi 已提交
1112 1113
	struct ovl_entry *oe;
	struct ovl_fs *ufs;
1114 1115 1116 1117 1118
	struct path *stack = NULL;
	char *lowertmp;
	char *lower;
	unsigned int numlower;
	unsigned int stacklen = 0;
1119
	unsigned int i;
1120
	bool remote = false;
M
Miklos Szeredi 已提交
1121 1122
	int err;

1123 1124 1125
	err = -ENOMEM;
	ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
	if (!ufs)
M
Miklos Szeredi 已提交
1126 1127
		goto out;

1128 1129 1130 1131
	err = ovl_parse_opt((char *) data, &ufs->config);
	if (err)
		goto out_free_config;

M
Miklos Szeredi 已提交
1132
	err = -EINVAL;
1133
	if (!ufs->config.lowerdir) {
1134 1135
		if (!silent)
			pr_err("overlayfs: missing 'lowerdir'\n");
M
Miklos Szeredi 已提交
1136 1137 1138
		goto out_free_config;
	}

1139
	sb->s_stack_depth = 0;
1140
	sb->s_maxbytes = MAX_LFS_FILESIZE;
1141 1142 1143 1144 1145
	if (ufs->config.upperdir) {
		if (!ufs->config.workdir) {
			pr_err("overlayfs: missing 'workdir'\n");
			goto out_free_config;
		}
M
Miklos Szeredi 已提交
1146

1147 1148 1149
		err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
		if (err)
			goto out_free_config;
M
Miklos Szeredi 已提交
1150

1151 1152 1153 1154 1155 1156 1157
		/* 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;
		}

1158 1159 1160 1161
		err = ovl_mount_dir(ufs->config.workdir, &workpath);
		if (err)
			goto out_put_upperpath;

1162
		err = -EINVAL;
1163 1164 1165 1166 1167 1168 1169 1170 1171
		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;
1172
	}
1173 1174 1175
	err = -ENOMEM;
	lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
	if (!lowertmp)
1176
		goto out_put_workpath;
1177

1178 1179
	err = -EINVAL;
	stacklen = ovl_split_lowerdirs(lowertmp);
1180
	if (stacklen > OVL_MAX_STACK) {
1181
		pr_err("overlayfs: too many lower directories, limit is %d\n",
1182
		       OVL_MAX_STACK);
1183
		goto out_free_lowertmp;
1184 1185 1186 1187
	} else if (!ufs->config.upperdir && stacklen == 1) {
		pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
		goto out_free_lowertmp;
	}
1188 1189 1190 1191 1192 1193 1194 1195

	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],
1196 1197
				    &ufs->lower_namelen, &sb->s_stack_depth,
				    &remote);
1198 1199 1200 1201 1202 1203
		if (err)
			goto out_put_lowerpath;

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

1204
	err = -EINVAL;
1205
	sb->s_stack_depth++;
1206 1207
	if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
		pr_err("overlayfs: maximum fs stacking depth exceeded\n");
1208
		goto out_put_lowerpath;
1209 1210
	}

1211 1212 1213 1214 1215 1216 1217
	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;
		}
1218 1219 1220 1221
		/* 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;
1222

1223 1224 1225
		ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
		err = PTR_ERR(ufs->workdir);
		if (IS_ERR(ufs->workdir)) {
1226 1227 1228 1229
			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;
1230
		}
1231 1232 1233 1234

		/*
		 * Upper should support d_type, else whiteouts are visible.
		 * Given workdir and upper are on same fs, we can do
1235 1236
		 * iterate_dir() on workdir. This check requires successful
		 * creation of workdir in previous step.
1237
		 */
1238 1239 1240 1241
		if (ufs->workdir) {
			err = ovl_check_d_type_supported(&workpath);
			if (err < 0)
				goto out_put_workdir;
1242

1243 1244 1245 1246 1247 1248 1249
			/*
			 * 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");
1250
		}
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	}

1253
	err = -ENOMEM;
1254
	ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
1255
	if (ufs->lower_mnt == NULL)
1256
		goto out_put_workdir;
1257 1258
	for (i = 0; i < numlower; i++) {
		struct vfsmount *mnt = clone_private_mount(&stack[i]);
1259

1260
		err = PTR_ERR(mnt);
1261 1262 1263 1264 1265 1266 1267 1268
		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.
		 */
1269
		mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1270

1271 1272 1273
		ufs->lower_mnt[ufs->numlower] = mnt;
		ufs->numlower++;
	}
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1274

1275 1276
	/* If the upper fs is nonexistent, we mark overlayfs r/o too */
	if (!ufs->upper_mnt)
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1277 1278
		sb->s_flags |= MS_RDONLY;

1279 1280 1281 1282
	if (remote)
		sb->s_d_op = &ovl_reval_dentry_operations;
	else
		sb->s_d_op = &ovl_dentry_operations;
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1283

1284 1285 1286 1287
	ufs->creator_cred = prepare_creds();
	if (!ufs->creator_cred)
		goto out_put_lower_mnt;

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1288
	err = -ENOMEM;
1289
	oe = ovl_alloc_entry(numlower);
1290
	if (!oe)
1291
		goto out_put_cred;
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1292

1293
	root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR));
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1294
	if (!root_dentry)
1295
		goto out_free_oe;
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1296 1297

	mntput(upperpath.mnt);
1298 1299
	for (i = 0; i < numlower; i++)
		mntput(stack[i].mnt);
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1300
	path_put(&workpath);
1301
	kfree(lowertmp);
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1302 1303

	oe->__upperdentry = upperpath.dentry;
1304 1305 1306 1307
	for (i = 0; i < numlower; i++) {
		oe->lowerstack[i].dentry = stack[i].dentry;
		oe->lowerstack[i].mnt = ufs->lower_mnt[i];
	}
1308
	kfree(stack);
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1309 1310 1311

	root_dentry->d_fsdata = oe;

1312 1313 1314
	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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1315

1316
	sb->s_magic = OVERLAYFS_SUPER_MAGIC;
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1317
	sb->s_op = &ovl_super_operations;
1318
	sb->s_xattr = ovl_xattr_handlers;
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1319 1320
	sb->s_root = root_dentry;
	sb->s_fs_info = ufs;
1321
	sb->s_flags |= MS_POSIXACL;
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1322 1323 1324

	return 0;

1325 1326
out_free_oe:
	kfree(oe);
1327 1328
out_put_cred:
	put_cred(ufs->creator_cred);
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1329
out_put_lower_mnt:
1330 1331 1332
	for (i = 0; i < ufs->numlower; i++)
		mntput(ufs->lower_mnt[i]);
	kfree(ufs->lower_mnt);
1333 1334
out_put_workdir:
	dput(ufs->workdir);
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1335 1336
	mntput(ufs->upper_mnt);
out_put_lowerpath:
1337 1338 1339 1340 1341
	for (i = 0; i < numlower; i++)
		path_put(&stack[i]);
	kfree(stack);
out_free_lowertmp:
	kfree(lowertmp);
1342 1343
out_put_workpath:
	path_put(&workpath);
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1344 1345 1346
out_put_upperpath:
	path_put(&upperpath);
out_free_config:
1347 1348 1349 1350
	kfree(ufs->config.lowerdir);
	kfree(ufs->config.upperdir);
	kfree(ufs->config.workdir);
	kfree(ufs);
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1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362
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,
1363
	.name		= "overlay",
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Miklos Szeredi 已提交
1364 1365 1366
	.mount		= ovl_mount,
	.kill_sb	= kill_anon_super,
};
1367
MODULE_ALIAS_FS("overlay");
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1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380

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);
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