// SPDX-License-Identifier: GPL-2.0-only
/*
File: fs/xattr.c
Extended attribute handling.
Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
*/
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/xattr.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/evm.h>
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/fsnotify.h>
#include <linux/audit.h>
#include <linux/vmalloc.h>
#include <linux/posix_acl_xattr.h>
#include <linux/uaccess.h>
#include "internal.h"
static const char *
strcmp_prefix(const char *a, const char *a_prefix)
{
while (*a_prefix && *a == *a_prefix) {
a++;
a_prefix++;
}
return *a_prefix ? NULL : a;
}
/*
* In order to implement different sets of xattr operations for each xattr
* prefix, a filesystem should create a null-terminated array of struct
* xattr_handler (one for each prefix) and hang a pointer to it off of the
* s_xattr field of the superblock.
*/
#define for_each_xattr_handler(handlers, handler) \
if (handlers) \
for ((handler) = *(handlers)++; \
(handler) != NULL; \
(handler) = *(handlers)++)
/*
* Find the xattr_handler with the matching prefix.
*/
static const struct xattr_handler *
xattr_resolve_name(struct inode *inode, const char **name)
{
const struct xattr_handler **handlers = inode->i_sb->s_xattr;
const struct xattr_handler *handler;
if (!(inode->i_opflags & IOP_XATTR)) {
if (unlikely(is_bad_inode(inode)))
return ERR_PTR(-EIO);
return ERR_PTR(-EOPNOTSUPP);
}
for_each_xattr_handler(handlers, handler) {
const char *n;
n = strcmp_prefix(*name, xattr_prefix(handler));
if (n) {
if (!handler->prefix ^ !*n) {
if (*n)
continue;
return ERR_PTR(-EINVAL);
}
*name = n;
return handler;
}
}
return ERR_PTR(-EOPNOTSUPP);
}
/**
* may_write_xattr - check whether inode allows writing xattr
* @idmap: idmap of the mount the inode was found from
* @inode: the inode on which to set an xattr
*
* Check whether the inode allows writing xattrs. Specifically, we can never
* set or remove an extended attribute on a read-only filesystem or on an
