From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752018AbcFXOhW (ORCPT ); Fri, 24 Jun 2016 10:37:22 -0400 Received: from mx2.suse.de ([195.135.220.15]:56494 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751652AbcFXOhU (ORCPT ); Fri, 24 Jun 2016 10:37:20 -0400 Date: Fri, 24 Jun 2016 16:37:18 +0200 Message-ID: From: Takashi Iwai To: Dmitry Vyukov Cc: Jaroslav Kysela , alsa-devel@alsa-project.org, LKML , Sasha Levin , Alexander Potapenko , Kostya Serebryany , syzkaller Subject: Re: sound: use-after-free in hrtimer_cancel In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI/1.14.6 (Maruoka) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 Emacs/24.5 (x86_64-suse-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 24 Jun 2016 15:33:35 +0200, Dmitry Vyukov wrote: > > On Fri, Jun 24, 2016 at 3:32 PM, Takashi Iwai wrote: > > On Tue, 21 Jun 2016 20:26:48 +0200, > > Dmitry Vyukov wrote: > >> > >> On Mon, Jun 6, 2016 at 4:11 PM, Takashi Iwai wrote: > >> > On Sat, 04 Jun 2016 20:27:50 +0200, > >> > Dmitry Vyukov wrote: > >> >> > >> >> On Sat, Jun 4, 2016 at 8:00 PM, Dmitry Vyukov wrote: > >> >> > Hello, > >> >> > > >> >> > The following program triggers use-after-free: > >> >> > >> >> Forget to mention that you need to run it in a tight parallel loop. It > >> >> takes around 5 minutes to reproduce for me. > >> > > >> > Hmm, this again is a bug that is difficult to trigger... At least, I > >> > couldn't reproduce locally. How many processes are you running with > >> > stress program? > >> > > >> > It seems that there is nothing more than opening /dev/audio and does > >> > some mmap in the job. Is there any other relevant thing there? > >> > > >> > Also, this assumes that the first sound card is Dummy driver, right? > >> > Check /proc/asound/cards. > >> > > >> > If it's about snd-dummy driver, one blind shot would be a patch like > >> > below. But even if it would fix, it doesn't explain why it's > >> > triggered in that way... > >> > > >> > > >> > thanks, > >> > > >> > Takashi > >> > > >> > --- > >> > diff --git a/sound/drivers/dummy.c b/sound/drivers/dummy.c > >> > index c0f8f613f1f1..172dacd925f5 100644 > >> > --- a/sound/drivers/dummy.c > >> > +++ b/sound/drivers/dummy.c > >> > @@ -420,6 +420,7 @@ static int dummy_hrtimer_stop(struct snd_pcm_substream *substream) > >> > > >> > static inline void dummy_hrtimer_sync(struct dummy_hrtimer_pcm *dpcm) > >> > { > >> > + hrtimer_cancel(&dpcm->timer); > >> > tasklet_kill(&dpcm->tasklet); > >> > } > >> > >> > >> Yes, this seems to fix it. I've stressed it for an hour with several > >> reproducers. If I am not mistaken, it also makes test cases run 15% > >> faster. > > > > Interesting. Possibly because it now syncs properly before other > > restart of stream or such... > > > >> Please mail a patch. > > > > OK, below is the formal patch. > > Let me know if I can give your tested-by tag. > > Sure. > > Tested-by: Dmitry Vyukov Thanks, the patch queued with your tags, now. Takashi