linux/fs/overlayfs/dir.c
Amir Goldstein 01b39dcc95 ovl: use inode_insert5() to hash a newly created inode
Currently, there is a small window where ovl_obtain_alias() can
race with ovl_instantiate() and create two different overlay inodes
with the same underlying real non-dir non-hardlink inode.

The race requires an adversary to guess the file handle of the
yet to be created upper inode and decode the guessed file handle
after ovl_creat_real(), but before ovl_instantiate().
This race does not affect overlay directory inodes, because those
are decoded via ovl_lookup_real() and not with ovl_obtain_alias().

This patch fixes the race, by using inode_insert5() to add a newly
created inode to cache.

If the newly created inode apears to already exist in cache (hashed
by the same real upper inode), we instantiate the dentry with the old
inode and drop the new inode, instead of silently not hashing the new
inode.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-31 11:06:12 +02:00

1180 lines
26 KiB
C

/*
*
* 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>
#include <linux/xattr.h>
#include <linux/security.h>
#include <linux/cred.h>
#include <linux/module.h>
#include <linux/posix_acl.h>
#include <linux/posix_acl_xattr.h>
#include <linux/atomic.h>
#include <linux/ratelimit.h>
#include "overlayfs.h"
static unsigned short ovl_redirect_max = 256;
module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
MODULE_PARM_DESC(ovl_redirect_max,
"Maximum length of absolute redirect xattr value");
int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
{
int err;
dget(wdentry);
if (d_is_dir(wdentry))
err = ovl_do_rmdir(wdir, wdentry);
else
err = ovl_do_unlink(wdir, wdentry);
dput(wdentry);
if (err) {
pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
wdentry, err);
}
return err;
}
static struct dentry *ovl_lookup_temp(struct dentry *workdir)
{
struct dentry *temp;
char name[20];
static atomic_t temp_id = ATOMIC_INIT(0);
/* counter is allowed to wrap, since temp dentries are ephemeral */
snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
temp = lookup_one_len(name, workdir, strlen(name));
if (!IS_ERR(temp) && temp->d_inode) {
pr_err("overlayfs: workdir/%s already exists\n", name);
dput(temp);
temp = ERR_PTR(-EIO);
}
return temp;
}
/* caller holds i_mutex on workdir */
static struct dentry *ovl_whiteout(struct dentry *workdir)
{
int err;
struct dentry *whiteout;
struct inode *wdir = workdir->d_inode;
whiteout = ovl_lookup_temp(workdir);
if (IS_ERR(whiteout))
return whiteout;
err = ovl_do_whiteout(wdir, whiteout);
if (err) {
dput(whiteout);
whiteout = ERR_PTR(err);
}
return whiteout;
}
/* Caller must hold i_mutex on both workdir and dir */
int ovl_cleanup_and_whiteout(struct dentry *workdir, struct inode *dir,
struct dentry *dentry)
{
struct inode *wdir = workdir->d_inode;
struct dentry *whiteout;
int err;
int flags = 0;
whiteout = ovl_whiteout(workdir);
err = PTR_ERR(whiteout);
if (IS_ERR(whiteout))
return err;
if (d_is_dir(dentry))
flags = RENAME_EXCHANGE;
err = ovl_do_rename(wdir, whiteout, dir, dentry, flags);
if (err)
goto kill_whiteout;
if (flags)
ovl_cleanup(wdir, dentry);
out:
dput(whiteout);
return err;
kill_whiteout:
ovl_cleanup(wdir, whiteout);
goto out;
}
static int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry,
umode_t mode)
{
int err;
struct dentry *d, *dentry = *newdentry;
err = ovl_do_mkdir(dir, dentry, mode);
if (err)
return err;
if (likely(!d_unhashed(dentry)))
return 0;
/*
* vfs_mkdir() may succeed and leave the dentry passed
* to it unhashed and negative. If that happens, try to
* lookup a new hashed and positive dentry.
*/
d = lookup_one_len(dentry->d_name.name, dentry->d_parent,
dentry->d_name.len);
if (IS_ERR(d)) {
pr_warn("overlayfs: failed lookup after mkdir (%pd2, err=%i).\n",
dentry, err);
return PTR_ERR(d);
}
dput(dentry);
*newdentry = d;
return 0;
}
struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
struct ovl_cattr *attr)
{
int err;
if (IS_ERR(newdentry))
return newdentry;
err = -ESTALE;
if (newdentry->d_inode)
goto out;
if (attr->hardlink) {
err = ovl_do_link(attr->hardlink, dir, newdentry);
} else {
switch (attr->mode & S_IFMT) {
case S_IFREG:
err = ovl_do_create(dir, newdentry, attr->mode);
break;
case S_IFDIR:
/* mkdir is special... */
err = ovl_mkdir_real(dir, &newdentry, attr->mode);
break;
case S_IFCHR:
case S_IFBLK:
case S_IFIFO:
case S_IFSOCK:
err = ovl_do_mknod(dir, newdentry, attr->mode,
attr->rdev);
break;
case S_IFLNK:
err = ovl_do_symlink(dir, newdentry, attr->link);
break;
default:
err = -EPERM;
}
}
if (!err && WARN_ON(!newdentry->d_inode)) {
/*
* Not quite sure if non-instantiated dentry is legal or not.
* VFS doesn't seem to care so check and warn here.
*/
err = -EIO;
}
out:
if (err) {
dput(newdentry);
return ERR_PTR(err);
}
return newdentry;
}
struct dentry *ovl_create_temp(struct dentry *workdir, struct ovl_cattr *attr)
{
return ovl_create_real(d_inode(workdir), ovl_lookup_temp(workdir),
attr);
}
static int ovl_set_opaque_xerr(struct dentry *dentry, struct dentry *upper,
int xerr)
{
int err;
err = ovl_check_setxattr(dentry, upper, OVL_XATTR_OPAQUE, "y", 1, xerr);
if (!err)
ovl_dentry_set_opaque(dentry);
return err;
}
static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
{
/*
* Fail with -EIO when trying to create opaque dir and upper doesn't
* support xattrs. ovl_rename() calls ovl_set_opaque_xerr(-EXDEV) to
* return a specific error for noxattr case.
*/
return ovl_set_opaque_xerr(dentry, upperdentry, -EIO);
}
/*
* Common operations required to be done after creation of file on upper.
* If @hardlink is false, then @inode is a pre-allocated inode, we may or
* may not use to instantiate the new dentry.
*/
static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
struct dentry *newdentry, bool hardlink)
{
struct ovl_inode_params oip = {
.upperdentry = newdentry,
.newinode = inode,
};
ovl_dentry_version_inc(dentry->d_parent, false);
ovl_dentry_set_upper_alias(dentry);
if (!hardlink) {
/*
* ovl_obtain_alias() can be called after ovl_create_real()
* and before we get here, so we may get an inode from cache
* with the same real upperdentry that is not the inode we
* pre-allocated. In this case we will use the cached inode
* to instantiate the new dentry.
*
* XXX: if we ever use ovl_obtain_alias() to decode directory
* file handles, need to use ovl_get_inode_locked() and
* d_instantiate_new() here to prevent from creating two
* hashed directory inode aliases.
*/
inode = ovl_get_inode(dentry->d_sb, &oip);
if (WARN_ON(IS_ERR(inode)))
return PTR_ERR(inode);
} else {
WARN_ON(ovl_inode_real(inode) != d_inode(newdentry));
dput(newdentry);
inc_nlink(inode);
}
d_instantiate(dentry, inode);
if (inode != oip.newinode) {
pr_warn_ratelimited("overlayfs: newly created inode found in cache (%pd2)\n",
dentry);
}
/* Force lookup of new upper hardlink to find its lower */
if (hardlink)
d_drop(dentry);
return 0;
}
static bool ovl_type_merge(struct dentry *dentry)
{
return OVL_TYPE_MERGE(ovl_path_type(dentry));
}
static bool ovl_type_origin(struct dentry *dentry)
{
return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
}
static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
struct ovl_cattr *attr)
{
struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
struct inode *udir = upperdir->d_inode;
struct dentry *newdentry;
int err;
if (!attr->hardlink && !IS_POSIXACL(udir))
attr->mode &= ~current_umask();
inode_lock_nested(udir, I_MUTEX_PARENT);
newdentry = ovl_create_real(udir,
lookup_one_len(dentry->d_name.name,
upperdir,
dentry->d_name.len),
attr);
err = PTR_ERR(newdentry);
if (IS_ERR(newdentry))
goto out_unlock;
if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
/* Setting opaque here is just an optimization, allow to fail */
ovl_set_opaque(dentry, newdentry);
}
err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink);
if (err)
goto out_cleanup;
out_unlock:
inode_unlock(udir);
return err;
out_cleanup:
ovl_cleanup(udir, newdentry);
dput(newdentry);
goto out_unlock;
}
static struct dentry *ovl_clear_empty(struct dentry *dentry,
struct list_head *list)
{
struct dentry *workdir = ovl_workdir(dentry);
struct inode *wdir = workdir->d_inode;
struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
struct inode *udir = upperdir->d_inode;
struct path upperpath;
struct dentry *upper;
struct dentry *opaquedir;
struct kstat stat;
int err;
if (WARN_ON(!workdir))
return ERR_PTR(-EROFS);
err = ovl_lock_rename_workdir(workdir, upperdir);
if (err)
goto out;
ovl_path_upper(dentry, &upperpath);
err = vfs_getattr(&upperpath, &stat,
STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
if (err)
goto out_unlock;
err = -ESTALE;
if (!S_ISDIR(stat.mode))
goto out_unlock;
upper = upperpath.dentry;
if (upper->d_parent->d_inode != udir)
goto out_unlock;
opaquedir = ovl_create_temp(workdir, OVL_CATTR(stat.mode));
err = PTR_ERR(opaquedir);
if (IS_ERR(opaquedir))
goto out_unlock;
err = ovl_copy_xattr(upper, opaquedir);
if (err)
goto out_cleanup;
err = ovl_set_opaque(dentry, opaquedir);
if (err)
goto out_cleanup;
inode_lock(opaquedir->d_inode);
err = ovl_set_attr(opaquedir, &stat);
inode_unlock(opaquedir->d_inode);
if (err)
goto out_cleanup;
err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
if (err)
goto out_cleanup;
ovl_cleanup_whiteouts(upper, list);
ovl_cleanup(wdir, upper);
unlock_rename(workdir, upperdir);
/* dentry's upper doesn't match now, get rid of it */
d_drop(dentry);
return opaquedir;
out_cleanup:
ovl_cleanup(wdir, opaquedir);
dput(opaquedir);
out_unlock:
unlock_rename(workdir, upperdir);
out:
return ERR_PTR(err);
}
static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
const struct posix_acl *acl)
{
void *buffer;
size_t size;
int err;
if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
return 0;
size = posix_acl_to_xattr(NULL, acl, NULL, 0);
buffer = kmalloc(size, GFP_KERNEL);
if (!buffer)
return -ENOMEM;
size = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
err = size;
if (err < 0)
goto out_free;
err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
out_free:
kfree(buffer);
return err;
}
static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
struct ovl_cattr *cattr)
{
struct dentry *workdir = ovl_workdir(dentry);
struct inode *wdir = workdir->d_inode;
struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
struct inode *udir = upperdir->d_inode;
struct dentry *upper;
struct dentry *newdentry;
int err;
struct posix_acl *acl, *default_acl;
bool hardlink = !!cattr->hardlink;
if (WARN_ON(!workdir))
return -EROFS;
if (!hardlink) {
err = posix_acl_create(dentry->d_parent->d_inode,
&cattr->mode, &default_acl, &acl);
if (err)
return err;
}
err = ovl_lock_rename_workdir(workdir, upperdir);
if (err)
goto out;
upper = lookup_one_len(dentry->d_name.name, upperdir,
dentry->d_name.len);
err = PTR_ERR(upper);
if (IS_ERR(upper))
goto out_unlock;
newdentry = ovl_create_temp(workdir, cattr);
err = PTR_ERR(newdentry);
if (IS_ERR(newdentry))
goto out_dput;
/*
* mode could have been mutilated due to umask (e.g. sgid directory)
*/
if (!hardlink &&
!S_ISLNK(cattr->mode) &&
newdentry->d_inode->i_mode != cattr->mode) {
struct iattr attr = {
.ia_valid = ATTR_MODE,
.ia_mode = cattr->mode,
};
inode_lock(newdentry->d_inode);
err = notify_change(newdentry, &attr, NULL);
inode_unlock(newdentry->d_inode);
if (err)
goto out_cleanup;
}
if (!hardlink) {
err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_ACCESS,
acl);
if (err)
goto out_cleanup;
err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_DEFAULT,
default_acl);
if (err)
goto out_cleanup;
}
if (!hardlink && S_ISDIR(cattr->mode)) {
err = ovl_set_opaque(dentry, newdentry);
if (err)
goto out_cleanup;
err = ovl_do_rename(wdir, newdentry, udir, upper,
RENAME_EXCHANGE);
if (err)
goto out_cleanup;
ovl_cleanup(wdir, upper);
} else {
err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
if (err)
goto out_cleanup;
}
err = ovl_instantiate(dentry, inode, newdentry, hardlink);
if (err)
goto out_cleanup;
out_dput:
dput(upper);
out_unlock:
unlock_rename(workdir, upperdir);
out:
if (!hardlink) {
posix_acl_release(acl);
posix_acl_release(default_acl);
}
return err;
out_cleanup:
ovl_cleanup(wdir, newdentry);
dput(newdentry);
goto out_dput;
}
static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
struct ovl_cattr *attr, bool origin)
{
int err;
const struct cred *old_cred;
struct cred *override_cred;
struct dentry *parent = dentry->d_parent;
err = ovl_copy_up(parent);
if (err)
return err;
old_cred = ovl_override_creds(dentry->d_sb);
/*
* When linking a file with copy up origin into a new parent, mark the
* new parent dir "impure".
*/
if (origin) {
err = ovl_set_impure(parent, ovl_dentry_upper(parent));
if (err)
goto out_revert_creds;
}
err = -ENOMEM;
override_cred = prepare_creds();
if (override_cred) {
override_cred->fsuid = inode->i_uid;
override_cred->fsgid = inode->i_gid;
if (!attr->hardlink) {
err = security_dentry_create_files_as(dentry,
attr->mode, &dentry->d_name, old_cred,
override_cred);
if (err) {
put_cred(override_cred);
goto out_revert_creds;
}
}
put_cred(override_creds(override_cred));
put_cred(override_cred);
if (!ovl_dentry_is_whiteout(dentry))
err = ovl_create_upper(dentry, inode, attr);
else
err = ovl_create_over_whiteout(dentry, inode, attr);
}
out_revert_creds:
revert_creds(old_cred);
return err;
}
static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
const char *link)
{
int err;
struct inode *inode;
struct ovl_cattr attr = {
.rdev = rdev,
.link = link,
};
err = ovl_want_write(dentry);
if (err)
goto out;
/* Preallocate inode to be used by ovl_get_inode() */
err = -ENOMEM;
inode = ovl_new_inode(dentry->d_sb, mode, rdev);
if (!inode)
goto out_drop_write;
inode_init_owner(inode, dentry->d_parent->d_inode, mode);
attr.mode = inode->i_mode;
err = ovl_create_or_link(dentry, inode, &attr, false);
/* Did we end up using the preallocated inode? */
if (inode != d_inode(dentry))
iput(inode);
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
bool excl)
{
return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
}
static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
{
return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
}
static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
dev_t rdev)
{
/* Don't allow creation of "whiteout" on overlay */
if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
return -EPERM;
return ovl_create_object(dentry, mode, rdev, NULL);
}
static int ovl_symlink(struct inode *dir, struct dentry *dentry,
const char *link)
{
return ovl_create_object(dentry, S_IFLNK, 0, link);
}
static int ovl_link(struct dentry *old, struct inode *newdir,
struct dentry *new)
{
int err;
bool locked = false;
struct inode *inode;
err = ovl_want_write(old);
if (err)
goto out;
err = ovl_copy_up(old);
if (err)
goto out_drop_write;
err = ovl_nlink_start(old, &locked);
if (err)
goto out_drop_write;
inode = d_inode(old);
ihold(inode);
err = ovl_create_or_link(new, inode,
&(struct ovl_cattr) {.hardlink = ovl_dentry_upper(old)},
ovl_type_origin(old));
if (err)
iput(inode);
ovl_nlink_end(old, locked);
out_drop_write:
ovl_drop_write(old);
out:
return err;
}
static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
{
return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
}
static int ovl_remove_and_whiteout(struct dentry *dentry,
struct list_head *list)
{
struct dentry *workdir = ovl_workdir(dentry);
struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
struct dentry *upper;
struct dentry *opaquedir = NULL;
int err;
if (WARN_ON(!workdir))
return -EROFS;
if (!list_empty(list)) {
opaquedir = ovl_clear_empty(dentry, list);
err = PTR_ERR(opaquedir);
if (IS_ERR(opaquedir))
goto out;
}
err = ovl_lock_rename_workdir(workdir, upperdir);
if (err)
goto out_dput;
upper = lookup_one_len(dentry->d_name.name, upperdir,
dentry->d_name.len);
err = PTR_ERR(upper);
if (IS_ERR(upper))
goto out_unlock;
err = -ESTALE;
if ((opaquedir && upper != opaquedir) ||
(!opaquedir && ovl_dentry_upper(dentry) &&
!ovl_matches_upper(dentry, upper))) {
goto out_dput_upper;
}
err = ovl_cleanup_and_whiteout(workdir, d_inode(upperdir), upper);
if (err)
goto out_d_drop;
ovl_dentry_version_inc(dentry->d_parent, true);
out_d_drop:
d_drop(dentry);
out_dput_upper:
dput(upper);
out_unlock:
unlock_rename(workdir, upperdir);
out_dput:
dput(opaquedir);
out:
return err;
}
static int ovl_remove_upper(struct dentry *dentry, bool is_dir,
struct list_head *list)
{
struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
struct inode *dir = upperdir->d_inode;
struct dentry *upper;
struct dentry *opaquedir = NULL;
int err;
if (!list_empty(list)) {
opaquedir = ovl_clear_empty(dentry, list);
err = PTR_ERR(opaquedir);
if (IS_ERR(opaquedir))
goto out;
}
inode_lock_nested(dir, I_MUTEX_PARENT);
upper = lookup_one_len(dentry->d_name.name, upperdir,
dentry->d_name.len);
err = PTR_ERR(upper);
if (IS_ERR(upper))
goto out_unlock;
err = -ESTALE;
if ((opaquedir && upper != opaquedir) ||
(!opaquedir && !ovl_matches_upper(dentry, upper)))
goto out_dput_upper;
if (is_dir)
err = vfs_rmdir(dir, upper);
else
err = vfs_unlink(dir, upper, NULL);
ovl_dentry_version_inc(dentry->d_parent, ovl_type_origin(dentry));
/*
* Keeping this dentry hashed would mean having to release
* upperpath/lowerpath, which could only be done if we are the
* sole user of this dentry. Too tricky... Just unhash for
* now.
*/
if (!err)
d_drop(dentry);
out_dput_upper:
dput(upper);
out_unlock:
inode_unlock(dir);
dput(opaquedir);
out:
return err;
}
static bool ovl_pure_upper(struct dentry *dentry)
{
return !ovl_dentry_lower(dentry) &&
!ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
}
static int ovl_do_remove(struct dentry *dentry, bool is_dir)
{
int err;
bool locked = false;
const struct cred *old_cred;
bool lower_positive = ovl_lower_positive(dentry);
LIST_HEAD(list);
/* No need to clean pure upper removed by vfs_rmdir() */
if (is_dir && (lower_positive || !ovl_pure_upper(dentry))) {
err = ovl_check_empty_dir(dentry, &list);
if (err)
goto out;
}
err = ovl_want_write(dentry);
if (err)
goto out;
err = ovl_copy_up(dentry->d_parent);
if (err)
goto out_drop_write;
err = ovl_nlink_start(dentry, &locked);
if (err)
goto out_drop_write;
old_cred = ovl_override_creds(dentry->d_sb);
if (!lower_positive)
err = ovl_remove_upper(dentry, is_dir, &list);
else
err = ovl_remove_and_whiteout(dentry, &list);
revert_creds(old_cred);
if (!err) {
if (is_dir)
clear_nlink(dentry->d_inode);
else
drop_nlink(dentry->d_inode);
}
ovl_nlink_end(dentry, locked);
out_drop_write:
ovl_drop_write(dentry);
out:
ovl_cache_free(&list);
return err;
}
static int ovl_unlink(struct inode *dir, struct dentry *dentry)
{
return ovl_do_remove(dentry, false);
}
static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
{
return ovl_do_remove(dentry, true);
}
static bool ovl_type_merge_or_lower(struct dentry *dentry)
{
enum ovl_path_type type = ovl_path_type(dentry);
return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
}
static bool ovl_can_move(struct dentry *dentry)
{
return ovl_redirect_dir(dentry->d_sb) ||
!d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
}
static char *ovl_get_redirect(struct dentry *dentry, bool samedir)
{
char *buf, *ret;
struct dentry *d, *tmp;
int buflen = ovl_redirect_max + 1;
if (samedir) {
ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
GFP_KERNEL);
goto out;
}
buf = ret = kmalloc(buflen, GFP_KERNEL);
if (!buf)
goto out;
buflen--;
buf[buflen] = '\0';
for (d = dget(dentry); !IS_ROOT(d);) {
const char *name;
int thislen;
spin_lock(&d->d_lock);
name = ovl_dentry_get_redirect(d);
if (name) {
thislen = strlen(name);
} else {
name = d->d_name.name;
thislen = d->d_name.len;
}
/* If path is too long, fall back to userspace move */
if (thislen + (name[0] != '/') > buflen) {
ret = ERR_PTR(-EXDEV);
spin_unlock(&d->d_lock);
goto out_put;
}
buflen -= thislen;
memcpy(&buf[buflen], name, thislen);
tmp = dget_dlock(d->d_parent);
spin_unlock(&d->d_lock);
dput(d);
d = tmp;
/* Absolute redirect: finished */
if (buf[buflen] == '/')
break;
buflen--;
buf[buflen] = '/';
}
ret = kstrdup(&buf[buflen], GFP_KERNEL);
out_put:
dput(d);
kfree(buf);
out:
return ret ? ret : ERR_PTR(-ENOMEM);
}
static int ovl_set_redirect(struct dentry *dentry, bool samedir)
{
int err;
const char *redirect = ovl_dentry_get_redirect(dentry);
if (redirect && (samedir || redirect[0] == '/'))
return 0;
redirect = ovl_get_redirect(dentry, samedir);
if (IS_ERR(redirect))
return PTR_ERR(redirect);
err = ovl_check_setxattr(dentry, ovl_dentry_upper(dentry),
OVL_XATTR_REDIRECT,
redirect, strlen(redirect), -EXDEV);
if (!err) {
spin_lock(&dentry->d_lock);
ovl_dentry_set_redirect(dentry, redirect);
spin_unlock(&dentry->d_lock);
} else {
kfree(redirect);
pr_warn_ratelimited("overlayfs: failed to set redirect (%i)\n",
err);
/* Fall back to userspace copy-up */
err = -EXDEV;
}
return err;
}
static int ovl_rename(struct inode *olddir, struct dentry *old,
struct inode *newdir, struct dentry *new,
unsigned int flags)
{
int err;
bool locked = false;
struct dentry *old_upperdir;
struct dentry *new_upperdir;
struct dentry *olddentry;
struct dentry *newdentry;
struct dentry *trap;
bool old_opaque;
bool new_opaque;
bool cleanup_whiteout = false;
bool overwrite = !(flags & RENAME_EXCHANGE);
bool is_dir = d_is_dir(old);
bool new_is_dir = d_is_dir(new);
bool samedir = olddir == newdir;
struct dentry *opaquedir = NULL;
const struct cred *old_cred = NULL;
LIST_HEAD(list);
err = -EINVAL;
if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
goto out;
flags &= ~RENAME_NOREPLACE;
/* Don't copy up directory trees */
err = -EXDEV;
if (!ovl_can_move(old))
goto out;
if (!overwrite && !ovl_can_move(new))
goto out;
if (overwrite && new_is_dir && !ovl_pure_upper(new)) {
err = ovl_check_empty_dir(new, &list);
if (err)
goto out;
}
if (overwrite) {
if (ovl_lower_positive(old)) {
if (!ovl_dentry_is_whiteout(new)) {
/* Whiteout source */
flags |= RENAME_WHITEOUT;
} else {
/* Switch whiteouts */
flags |= RENAME_EXCHANGE;
}
} else if (is_dir && ovl_dentry_is_whiteout(new)) {
flags |= RENAME_EXCHANGE;
cleanup_whiteout = true;
}
}
err = ovl_want_write(old);
if (err)
goto out;
err = ovl_copy_up(old);
if (err)
goto out_drop_write;
err = ovl_copy_up(new->d_parent);
if (err)
goto out_drop_write;
if (!overwrite) {
err = ovl_copy_up(new);
if (err)
goto out_drop_write;
} else {
err = ovl_nlink_start(new, &locked);
if (err)
goto out_drop_write;
}
old_cred = ovl_override_creds(old->d_sb);
if (!list_empty(&list)) {
opaquedir = ovl_clear_empty(new, &list);
err = PTR_ERR(opaquedir);
if (IS_ERR(opaquedir)) {
opaquedir = NULL;
goto out_revert_creds;
}
}
old_upperdir = ovl_dentry_upper(old->d_parent);
new_upperdir = ovl_dentry_upper(new->d_parent);
if (!samedir) {
/*
* When moving a merge dir or non-dir with copy up origin into
* a new parent, we are marking the new parent dir "impure".
* When ovl_iterate() iterates an "impure" upper dir, it will
* lookup the origin inodes of the entries to fill d_ino.
*/
if (ovl_type_origin(old)) {
err = ovl_set_impure(new->d_parent, new_upperdir);
if (err)
goto out_revert_creds;
}
if (!overwrite && ovl_type_origin(new)) {
err = ovl_set_impure(old->d_parent, old_upperdir);
if (err)
goto out_revert_creds;
}
}
trap = lock_rename(new_upperdir, old_upperdir);
olddentry = lookup_one_len(old->d_name.name, old_upperdir,
old->d_name.len);
err = PTR_ERR(olddentry);
if (IS_ERR(olddentry))
goto out_unlock;
err = -ESTALE;
if (!ovl_matches_upper(old, olddentry))
goto out_dput_old;
newdentry = lookup_one_len(new->d_name.name, new_upperdir,
new->d_name.len);
err = PTR_ERR(newdentry);
if (IS_ERR(newdentry))
goto out_dput_old;
old_opaque = ovl_dentry_is_opaque(old);
new_opaque = ovl_dentry_is_opaque(new);
err = -ESTALE;
if (d_inode(new) && ovl_dentry_upper(new)) {
if (opaquedir) {
if (newdentry != opaquedir)
goto out_dput;
} else {
if (!ovl_matches_upper(new, newdentry))
goto out_dput;
}
} else {
if (!d_is_negative(newdentry) &&
(!new_opaque || !ovl_is_whiteout(newdentry)))
goto out_dput;
}
if (olddentry == trap)
goto out_dput;
if (newdentry == trap)
goto out_dput;
if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
goto out_dput;
err = 0;
if (is_dir) {
if (ovl_type_merge_or_lower(old))
err = ovl_set_redirect(old, samedir);
else if (!old_opaque && ovl_type_merge(new->d_parent))
err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
if (err)
goto out_dput;
}
if (!overwrite && new_is_dir) {
if (ovl_type_merge_or_lower(new))
err = ovl_set_redirect(new, samedir);
else if (!new_opaque && ovl_type_merge(old->d_parent))
err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
if (err)
goto out_dput;
}
err = ovl_do_rename(old_upperdir->d_inode, olddentry,
new_upperdir->d_inode, newdentry, flags);
if (err)
goto out_dput;
if (cleanup_whiteout)
ovl_cleanup(old_upperdir->d_inode, newdentry);
if (overwrite && d_inode(new)) {
if (new_is_dir)
clear_nlink(d_inode(new));
else
drop_nlink(d_inode(new));
}
ovl_dentry_version_inc(old->d_parent, ovl_type_origin(old) ||
(!overwrite && ovl_type_origin(new)));
ovl_dentry_version_inc(new->d_parent, ovl_type_origin(old) ||
(d_inode(new) && ovl_type_origin(new)));
out_dput:
dput(newdentry);
out_dput_old:
dput(olddentry);
out_unlock:
unlock_rename(new_upperdir, old_upperdir);
out_revert_creds:
revert_creds(old_cred);
ovl_nlink_end(new, locked);
out_drop_write:
ovl_drop_write(old);
out:
dput(opaquedir);
ovl_cache_free(&list);
return err;
}
const struct inode_operations ovl_dir_inode_operations = {
.lookup = ovl_lookup,
.mkdir = ovl_mkdir,
.symlink = ovl_symlink,
.unlink = ovl_unlink,
.rmdir = ovl_rmdir,
.rename = ovl_rename,
.link = ovl_link,
.setattr = ovl_setattr,
.create = ovl_create,
.mknod = ovl_mknod,
.permission = ovl_permission,
.getattr = ovl_getattr,
.listxattr = ovl_listxattr,
.get_acl = ovl_get_acl,
.update_time = ovl_update_time,
};