From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752220AbcFFQjG (ORCPT ); Mon, 6 Jun 2016 12:39:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:46625 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751304AbcFFQjD (ORCPT ); Mon, 6 Jun 2016 12:39:03 -0400 Date: Mon, 06 Jun 2016 18:39:01 +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 Mon, 06 Jun 2016 18:29:25 +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? > > I use a VM with 4 cores and use 20 parallel test processes. > > > 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? > > > I think poll with timeout is related. It is poll who sets hrtimer, right? If it's about snd-dummy driver, hrtimer is created at open, and started/stopped at PCM trigger, and removed at close. Is there any good way to decode which syscalls are executed in the test code? Takashi > > Also, this assumes that the first sound card is Dummy driver, right? > > Check /proc/asound/cards. > > # cat /proc/asound/cards > 0 [Dummy ]: Dummy - Dummy > Dummy 1 > 1 [Loopback ]: Loopback - Loopback > Loopback 1 > 2 [VirMIDI ]: VirMIDI - VirMIDI > Virtual MIDI Card 1 > 3 [pcsp ]: PC-Speaker - pcsp > Internal PC-Speaker at port 0x61 > 4 [Intel ]: HDA-Intel - HDA Intel > HDA Intel at 0xfebf0000 irq 24 > > > > > 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); > > } > > >