From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966127AbdLSBBY (ORCPT ); Mon, 18 Dec 2017 20:01:24 -0500 Received: from mail-it0-f51.google.com ([209.85.214.51]:46083 "EHLO mail-it0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933276AbdLSBBV (ORCPT ); Mon, 18 Dec 2017 20:01:21 -0500 X-Google-Smtp-Source: ACJfBouxM4allXjS2b+/6atLg448QwhqR/k+eGcVOOlZPWPfU+aBLIuRfnZpKKApvtAjP5SqYNCKew== Date: Mon, 18 Dec 2017 17:01:17 -0800 From: Eric Biggers To: Thomas Gleixner Cc: Dmitry Vyukov , Greg KH , Kees Cook , Alexey Dobriyan , security@kernel.org, Akinobu Mita , Andrew Morton , "Eric W. Biederman" , Josh Poimboeuf , LKML , Ingo Molnar , syzkaller-bugs@googlegroups.com, Vegard Nossum Subject: Re: general protection fault in show_timer Message-ID: <20171219010117.GB55142@gmail.com> References: <20171212083343.GG22935@kroah.com> <20171214183607.GB259981@gmail.com> 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Dec 15, 2017 at 05:40:15PM +0100, Thomas Gleixner wrote: > On Thu, 14 Dec 2017, Eric Biggers wrote: > > On Thu, Dec 14, 2017 at 04:34:12PM +0100, Thomas Gleixner wrote: > > > On Thu, 14 Dec 2017, Dmitry Vyukov wrote: > > > > On Thu, Dec 14, 2017 at 3:26 PM, Thomas Gleixner wrote: > > > > > On Tue, 12 Dec 2017, Greg KH wrote: > > > > >> Did this ever go anywhere? I don't see it in Linus's tree yet... > > > > > > > > > > I learned yesterday that syzboz is understuffed and cannot test patches, so > > > > > I need to find a minute to run the reproducer myself and verify that the > > > > > patch is correct. > > > > > > > > Hi Thomas, > > > > > > > > Why do you say so? Have you tried to ask it to test? > > > > https://github.com/google/syzkaller/blob/master/docs/syzbot.md#communication-with-syzbot > > > > What happened? > > > > > > Eric explained that to me yesterday and I did not try yet. > > > > > > > Your patch definitely fixes the bug (I tested the C reproducers, you just need > > to build a kernel with CONFIG_CHECKPOINT_RESTORE=y and CONFIG_POSIX_TIMERS=y, > > then run them). The real question is whether the check being introduced is too > > strict -- are there users passing in other values for ->sigev_notify that would > > be broken? That I can't really answer. > > Me neither. The manpage is rather clear about the possible values, so I > don't expect wreckage. Aside of that non canonical values would have to > have bit 2, i.e. SIGEV_THREAD_ID cleared because that already has a > restriction that it's only allowed with SIGEV_SIGNAL. So unlikely... > > If really some crap application breaks we can handle it in the default > clause by setting it to SIGEV_SIGNAL. Though I rather prefer not to do that > unless it turns out to be absolutely necessary. > I see a fix is committed now (thanks!), so let's tell syzbot: #syz fix: posix-timer: Properly check sigevent->sigev_notify