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 X-Spam-Level: X-Spam-Status: No, score=-5.5 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DFA59C433E7 for ; Thu, 3 Sep 2020 06:17:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF66820737 for ; Thu, 3 Sep 2020 06:17:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726855AbgICGRU (ORCPT ); Thu, 3 Sep 2020 02:17:20 -0400 Received: from brightrain.aerifal.cx ([216.12.86.13]:49162 "EHLO brightrain.aerifal.cx" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726047AbgICGRU (ORCPT ); Thu, 3 Sep 2020 02:17:20 -0400 Date: Thu, 3 Sep 2020 02:17:19 -0400 From: Rich Felker To: John Paul Adrian Glaubitz Cc: Michael Karcher , linux-sh@vger.kernel.org, linux-kernel@vger.kernel.org, Yoshinori Sato Subject: Re: [PATCH 3/4] sh: Add SECCOMP_FILTER Message-ID: <20200903061718.GZ3265@brightrain.aerifal.cx> References: <20200722231322.419642-3-kernel@mkarcher.dialup.fu-berlin.de> <20200828155024.GX3265@brightrain.aerifal.cx> <20200828163057.GY3265@brightrain.aerifal.cx> <82b625c2-23cb-69a4-7495-39427430c306@physik.fu-berlin.de> <20200828170259.GZ3265@brightrain.aerifal.cx> <20200829004939.GB3265@brightrain.aerifal.cx> <20200903035603.GV3265@brightrain.aerifal.cx> <20200903054617.GW3265@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 03, 2020 at 08:04:44AM +0200, John Paul Adrian Glaubitz wrote: > On 9/3/20 7:46 AM, Rich Felker wrote: > > > > OK, I think I have an explanation for the mechanism of the bug, and it > > really is a combination of the 2008 bug (confusion of r0 vs r3) and > > the SECCOMP_FILTER commit. When the syscall_trace_entry code path is > > in use, a syscall with argument 5 having value -1 causes > > do_syscall_trace_enter to return -1 (because it returns regs[0], which > > contains argument 5), which the change in entry-common.S interprets as > > a sign to skip the syscall and jump to syscall_exit, and things blow > > up from there. In particular, SYS_mmap2 is almost always called with > > -1 as the 5th argument (fd), and this is even more common on nommu > > where SYS_brk does not work. > > > > I'll follow up with a new proposed patch. > > I'm not sure whether we need another revision of your first patch. Your > previous analysis was at least right regarding the tests 51 and 58 > but those have been fixed now. > > But there were two other tests failing, weren't there? > > I have to recheck later, I just got up (it's 8 AM CEST). The first patch was surely not right; setting syscall_nr to -1 and letting it -ENOSYS clobbered any return value set by the seccomp filters. The one I've sent now should be right. I'll follow up after testing with libseccomp test cases. Rich