From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754037Ab2B0QWU (ORCPT ); Mon, 27 Feb 2012 11:22:20 -0500 Received: from mail-lpp01m010-f46.google.com ([209.85.215.46]:38212 "EHLO mail-lpp01m010-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753918Ab2B0QWN convert rfc822-to-8bit (ORCPT ); Mon, 27 Feb 2012 11:22:13 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of wad@chromium.org designates 10.152.130.98 as permitted sender) smtp.mail=wad@chromium.org; dkim=pass header.i=wad@chromium.org MIME-Version: 1.0 In-Reply-To: References: <1330140111-17201-1-git-send-email-wad@chromium.org> <1330140111-17201-7-git-send-email-wad@chromium.org> Date: Mon, 27 Feb 2012 10:22:09 -0600 Message-ID: Subject: Re: [PATCH v11 07/12] seccomp: add SECCOMP_RET_ERRNO From: Will Drewry To: Kees Cook Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, kernel-hardening@lists.openwall.com, netdev@vger.kernel.org, x86@kernel.org, arnd@arndb.de, davem@davemloft.net, hpa@zytor.com, mingo@redhat.com, oleg@redhat.com, peterz@infradead.org, rdunlap@xenotime.net, mcgrathr@chromium.org, tglx@linutronix.de, luto@mit.edu, eparis@redhat.com, serge.hallyn@canonical.com, djm@mindrot.org, scarybeasts@gmail.com, indan@nul.nu, pmoore@redhat.com, akpm@linux-foundation.org, corbet@lwn.net, eric.dumazet@gmail.com, markus@chromium.org, coreyb@linux.vnet.ibm.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Feb 25, 2012 at 2:20 PM, Kees Cook wrote: > On Fri, Feb 24, 2012 at 7:21 PM, Will Drewry wrote: >> This change adds the SECCOMP_RET_ERRNO as a valid return value from a >> seccomp filter.  Additionally, it makes the first use of the lower >> 16-bits for storing a filter-supplied errno.  16-bits is more than >> enough for the errno-base.h calls. >> >> Returning errors instead of immediately terminating processes that >> violate seccomp policy allow for broader use of this functionality >> for kernel attack surface reduction.  For example, a linux container >> could maintain a whitelist of pre-existing system calls but drop >> all new ones with errnos.  This would keep a logically static attack >> surface while providing errnos that may allow for graceful failure >> without the downside of do_exit() on a bad call. >> >> v11: - check for NULL filter (keescook@chromium.org) >> v10: - change loaders to fn >>  v9: - n/a >>  v8: - update Kconfig to note new need for syscall_set_return_value. >>     - reordered such that TRAP behavior follows on later. >>     - made the for loop a little less indent-y >>  v7: - introduced >> >> Signed-off-by: Will Drewry > > Reviewed-by: Kees Cook Thanks! >> +       /* Ensure unexpected behavior doesn't result in failing open. */ >> +       if (unlikely(current->seccomp.filter == NULL)) >> +               ret = SECCOMP_RET_KILL; > > Any reason to not just immediately return in this case? Not that I can think of. I can just have it bail here.