readlinkat: ensure we return ENOENT for the empty pathname for normal lookups
authorAndy Whitcroft <apw@canonical.com>
Wed, 2 Nov 2011 08:44:39 +0000 (09:44 +0100)
committerGreg Kroah-Hartman <gregkh@suse.de>
Fri, 11 Nov 2011 17:43:35 +0000 (09:43 -0800)
commit4f0d844bad2b3c705767e3df85978aae2ca5beb7
tree475c19f9a1c77c850fdbdbcc5704bdf7ec9b09a4
parent02e66bee63c63c2bec1947553e6c5b58b3f0c67d
readlinkat: ensure we return ENOENT for the empty pathname for normal lookups

commit 1fa1e7f615f4d3ae436fa319af6e4eebdd4026a8 upstream.

Since the commit below which added O_PATH support to the *at() calls, the
error return for readlink/readlinkat for the empty pathname has switched
from ENOENT to EINVAL:

  commit 65cfc6722361570bfe255698d9cd4dccaf47570d
  Author: Al Viro <viro@zeniv.linux.org.uk>
  Date:   Sun Mar 13 15:56:26 2011 -0400

    readlinkat(), fchownat() and fstatat() with empty relative pathnames

This is both unexpected for userspace and makes readlink/readlinkat
inconsistant with all other interfaces; and inconsistant with our stated
return for these pathnames.

As the readlinkat call does not have a flags parameter we cannot use the
AT_EMPTY_PATH approach used in the other calls.  Therefore expose whether
the original path is infact entry via a new user_path_at_empty() path
lookup function.  Use this to determine whether to default to EINVAL or
ENOENT for failures.

Addresses http://bugs.launchpad.net/bugs/817187

[akpm@linux-foundation.org: remove unused getname_flags()]
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
fs/namei.c
fs/stat.c
include/linux/namei.h