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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/slab.h>
#include <linux/xattr.h>
#include "overlayfs.h"
static int ovl_copy_up_truncate(struct dentry *dentry)
{
int err;
struct dentry *parent;
struct kstat stat;
struct path lowerpath;
parent = dget_parent(dentry);
err = ovl_copy_up(parent);
if (err)
goto out_dput_parent;
ovl_path_lower(dentry, &lowerpath);
err = vfs_getattr(&lowerpath, &stat);
if (err)
goto out_dput_parent;
stat.size = 0;
err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
out_dput_parent:
dput(parent);
return err;
}
int ovl_setattr(struct dentry *dentry, struct iattr *attr)
{
int err;
struct dentry *upperdentry;
/*
* Check for permissions before trying to copy-up. This is redundant
* since it will be rechecked later by ->setattr() on upper dentry. But
* without this, copy-up can be triggered by just about anybody.
*
* We don't initialize inode->size, which just means that
* inode_newsize_ok() will always check against MAX_LFS_FILESIZE and not
* check for a swapfile (which this won't be anyway).
*/
err = inode_change_ok(dentry->d_inode, attr);
if (err)
return err;
err = ovl_want_write(dentry);
if (err)
goto out;
err = ovl_copy_up(dentry);
if (!err) {
upperdentry = ovl_dentry_upper(dentry);
inode_lock(upperdentry->d_inode);
err = notify_change(upperdentry, attr, NULL);
if (!err)
ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
inode_unlock(upperdentry->d_inode);
}
ovl_drop_write(dentry);
out:
return err;
}
static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
struct kstat *stat)
{
struct path realpath;
ovl_path_real(dentry, &realpath);
return vfs_getattr(&realpath, stat);
}
int ovl_permission(struct inode *inode, int mask)
{
struct ovl_entry *oe;
struct dentry *alias = NULL;
struct inode *realinode;
struct dentry *realdentry;
bool is_upper;
int err;
if (S_ISDIR(inode->i_mode)) {
oe = inode->i_private;
} else if (mask & MAY_NOT_BLOCK) {
return -ECHILD;
} else {
/*
* For non-directories find an alias and get the info
* from there.
*/
alias = d_find_any_alias(inode);
if (WARN_ON(!alias))
return -ENOENT;
oe = alias->d_fsdata;
}
realdentry = ovl_entry_real(oe, &is_upper);
if (ovl_is_default_permissions(inode)) {
struct kstat stat;
struct path realpath = { .dentry = realdentry };
if (mask & MAY_NOT_BLOCK)
return -ECHILD;
realpath.mnt = ovl_entry_mnt_real(oe, inode, is_upper);
err = vfs_getattr(&realpath, &stat);
if (err)
return err;
if ((stat.mode ^ inode->i_mode) & S_IFMT)
return -ESTALE;
inode->i_mode = stat.mode;
inode->i_uid = stat.uid;
inode->i_gid = stat.gid;
return generic_permission(inode, mask);
}
/* Careful in RCU walk mode */
realinode = ACCESS_ONCE(realdentry->d_inode);
if (!realinode) {
WARN_ON(!(mask & MAY_NOT_BLOCK));
err = -ENOENT;
goto out_dput;
}
if (mask & MAY_WRITE) {
umode_t mode = realinode->i_mode;
/*
* Writes will always be redirected to upper layer, so
* ignore lower layer being read-only.
*
* If the overlay itself is read-only then proceed
* with the permission check, don't return EROFS.
* This will only happen if this is the lower layer of
* another overlayfs.
*
* If upper fs becomes read-only after the overlay was
* constructed return EROFS to prevent modification of
* upper layer.
*/
err = -EROFS;
if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
(S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
goto out_dput;
}
err = __inode_permission(realinode, mask);
out_dput:
dput(alias);
return err;
}
static const char *ovl_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
struct dentry *realdentry;
struct inode *realinode;
if (!dentry)
return ERR_PTR(-ECHILD);
realdentry = ovl_dentry_real(dentry);
realinode = realdentry->d_inode;
if (WARN_ON(!realinode->i_op->get_link))
return ERR_PTR(-EPERM);
return realinode->i_op->get_link(realdentry, realinode, done);
}
static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
{
struct path realpath;
struct inode *realinode;
ovl_path_real(dentry, &realpath);
realinode = realpath.dentry->d_inode;
if (!realinode->i_op->readlink)
return -EINVAL;
touch_atime(&realpath);
return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
}
static bool ovl_is_private_xattr(const char *name)
{
return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0;
}
int ovl_setxattr(struct dentry *dentry, const char *name,
const void *value, size_t size, int flags)
{
int err;
struct dentry *upperdentry;
err = ovl_want_write(dentry);
if (err)
goto out;
err = -EPERM;
if (ovl_is_private_xattr(name))
goto out_drop_write;
err = ovl_copy_up(dentry);
if (err)
goto out_drop_write;
upperdentry = ovl_dentry_upper(dentry);
err = vfs_setxattr(upperdentry, name, value, size, flags);
out_drop_write:
ovl_drop_write(dentry);
out:
return err;
}
static bool ovl_need_xattr_filter(struct dentry *dentry,
enum ovl_path_type type)
{
if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER)
return S_ISDIR(dentry->d_inode->i_mode);
else
return false;
}
ssize_t ovl_getxattr(struct dentry *dentry, struct inode *inode,
const char *name, void *value, size_t size)
{
struct path realpath;
enum ovl_path_type type = ovl_path_real(dentry, &realpath);
if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
return -ENODATA;
return vfs_getxattr(realpath.dentry, name, value, size);
}
ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
{
struct path realpath;
enum ovl_path_type type = ovl_path_real(dentry, &realpath);
ssize_t res;
int off;
res = vfs_listxattr(realpath.dentry, list, size);
if (re
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