From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D985C433EF for ; Tue, 1 Feb 2022 00:40:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230384AbiBAAkD (ORCPT ); Mon, 31 Jan 2022 19:40:03 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36604 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230376AbiBAAkC (ORCPT ); Mon, 31 Jan 2022 19:40:02 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3DE2C061714; Mon, 31 Jan 2022 16:40:01 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 82F2760FDB; Tue, 1 Feb 2022 00:40:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 841DFC340E8; Tue, 1 Feb 2022 00:39:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1643676000; bh=CsrXfoGMeQKaG2qPeBp//CQavVXu6y759jKmNTE+4L4=; h=Date:To:From:Subject:From; b=v+OsPI7k6b586cpIuu6JoKfz2yybET7JjhBwvl0cMto6MxzYaE/ZJyUdHRV+ODtoK 1DEo8l6WnatWTs3I7PPFRODOQaI1r/MMyi2yGX2DQPf6Kki/KRBYsrTlt/w9C5X+Lw O18GJqV/ajbReRUNF7Dh9TE2XonGCSRn0QOE7u0U= Received: by hp1 (sSMTP sendmail emulation); Mon, 31 Jan 2022 16:39:59 -0800 Date: Mon, 31 Jan 2022 16:39:59 -0800 To: mm-commits@vger.kernel.org, willy@infradead.org, viro@zeniv.linux.org.uk, stable@vger.kernel.org, mtk.manpages@gmail.com, keescook@chromium.org, ebiederm@xmission.com, dalias@libc.org, brauner@kernel.org, ariadne@dereferenced.org, akpm@linux-foundation.org From: Andrew Morton Subject: [alternative-merged] fs-exec-require-argv-presence-in-do_execveat_common.patch removed from -mm tree Message-Id: <20220201003959.841DFC340E8@smtp.kernel.org> Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: fs/exec: require argv[0] presence in do_execveat_common() has been removed from the -mm tree. Its filename was fs-exec-require-argv-presence-in-do_execveat_common.patch This patch was dropped because an alternative patch was merged ------------------------------------------------------ From: Ariadne Conill Subject: fs/exec: require argv[0] presence in do_execveat_common() In several other operating systems, it is a hard requirement that the second argument to execve(2) be the name of a program, thus prohibiting a scenario where argc < 1. POSIX 2017 also recommends this behaviour, but it is not an explicit requirement[0]: The argument arg0 should point to a filename string that is associated with the process being started by one of the exec functions. To ensure that execve(2) with argc < 1 is not a useful tool for shellcode to use, we can validate this in do_execveat_common() and fail for this scenario, effectively blocking successful exploitation of CVE-2021-4034 and similar bugs which depend on execve(2) working with argc < 1. We use -EINVAL for this case, mirroring recent changes to FreeBSD and OpenBSD. -EINVAL is also used by QNX for this, while Solaris uses -EFAULT. In earlier versions of the patch, it was proposed that we create a fake argv for applications to use when argc < 1, but it was concluded that it would be better to just fail the execve(2) in these cases, as launching a process with an empty or NULL argv[0] was likely to just cause more problems. Interestingly, Michael Kerrisk opened an issue about this in 2008[1], but there was no consensus to support fixing this issue then. Hopefully now that CVE-2021-4034 shows practical exploitative use[2] of this bug in a shellcode, we can reconsider. This issue is being tracked in the KSPP issue tracker[3]. There are a few[4][5] minor edge cases (primarily in test suites) that are caught by this, but we plan to work with the projects to fix those edge cases. [0]: https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html [1]: https://bugzilla.kernel.org/show_bug.cgi?id=8408 [2]: https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt [3]: https://github.com/KSPP/linux/issues/176 [4]: https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+*NULL&literal=0 [5]: https://codesearch.debian.net/search?q=execlp%3F%5Cs*%5C%28%5B%5E%2C%5D%2B%2C%5Cs*NULL&literal=0 Link: https://lkml.kernel.org/r/20220127000724.15106-1-ariadne@dereferenced.org Signed-off-by: Ariadne Conill Reported-by: Michael Kerrisk Cc: Matthew Wilcox Cc: Christian Brauner Cc: Rich Felker Cc: Eric Biederman Cc: Alexander Viro Cc: Kees Cook Cc: Signed-off-by: Andrew Morton --- fs/exec.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/fs/exec.c~fs-exec-require-argv-presence-in-do_execveat_common +++ a/fs/exec.c @@ -1897,6 +1897,10 @@ static int do_execveat_common(int fd, st } retval = count(argv, MAX_ARG_STRINGS); + if (retval == 0) { + pr_warn_once("Attempted to run process '%s' with NULL argv\n", bprm->filename); + retval = -EINVAL; + } if (retval < 0) goto out_free; bprm->argc = retval; _ Patches currently in -mm which might be from ariadne@dereferenced.org are