From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755326AbcAOTST (ORCPT ); Fri, 15 Jan 2016 14:18:19 -0500 Received: from mx2.suse.de ([195.135.220.15]:39172 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751444AbcAOTSS (ORCPT ); Fri, 15 Jan 2016 14:18:18 -0500 Date: Fri, 15 Jan 2016 20:18:16 +0100 Message-ID: From: Takashi Iwai To: Dmitry Vyukov Cc: alsa-devel@alsa-project.org, Jie Yang , Mark Brown , Jaroslav Kysela , LKML , Eric Dumazet , Alexander Potapenko , Kostya Serebryany , syzkaller , Sasha Levin Subject: Re: sound: use-after-free in snd_timer_interrupt 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, 15 Jan 2016 20:13:11 +0100, Dmitry Vyukov wrote: > > On Fri, Jan 15, 2016 at 3:38 PM, Dmitry Vyukov wrote: > > On Fri, Jan 15, 2016 at 2:51 PM, Takashi Iwai wrote: > >> On Fri, 15 Jan 2016 12:03:17 +0100, > >> Dmitry Vyukov wrote: > >>> > >>> On Fri, Jan 15, 2016 at 12:00 PM, Takashi Iwai wrote: > >>> > On Fri, 15 Jan 2016 09:06:10 +0100, > >>> > Dmitry Vyukov wrote: > >>> >> > >>> >> On Thu, Jan 14, 2016 at 5:09 PM, Takashi Iwai wrote: > >>> >> > On Wed, 13 Jan 2016 21:54:10 +0100, > >>> >> > Takashi Iwai wrote: > >>> >> >> > >>> >> >> OK, then this might be a possible race at the current snd_timer_stop() > >>> >> >> implementation. There is no sync action there, so the ISR might be > >>> >> >> still alive after snd_timer_close() call. Or might be another race. > >>> >> >> This pattern looks a bit different, as it's involved with hrtimer. > >>> >> >> > >>> >> >> I'll take a look at it tomorrow. > >>> >> > > >>> >> > I've audited the code today, but the open window doesn't look like > >>> >> > what I expected. I found only some possible cases with slave timer > >>> >> > instances. > >>> >> > > >>> >> > In anyway, below is a test fix patch. Since I couldn't reproduce the > >>> >> > issue on my local machines, it's hard to say whether this covers the > >>> >> > holes you fell. Let's see... > >>> >> > >>> >> > >>> >> Hi Takashi, > >>> >> > >>> >> I would be interested to understand why other people can't reproduce > >>> >> issues that I hit pretty reliably. > >>> >> I suspect that it can be due to .config. Please try with the following > >>> >> config values. > >>> > > >>> > I guess rather other config, e.g. the kernel debug options. > >>> > I suppose you enabled KASAN and DEBUG_LIST. What else? > >>> > >>> I've attached my config (you will need to disable CONFIG_KCOV, it is > >>> not upstreamed). > >> > >> Hm, that has lots of other drivers built-in... > >> > >>> >> I also start qemu with "-soundhw all" arg. > >>> > > >>> > OK, so you're testing with VM? This makes easier to recheck. > >>> > >>> Yes, I start qemu as: > >>> > >>> qemu-system-x86_64 -hda wheezy.img -net > >>> user,host=10.0.2.10,hostfwd=tcp::10022-:22 -net nic -nographic -kernel > >>> arch/x86/boot/bzImage -append "console=ttyS0 root=/dev/sda debug > >>> earlyprintk=serial slub_debug=UZ" -enable-kvm -m 2G -numa > >>> node,nodeid=0,cpus=0-1 -numa node,nodeid=1,cpus=2-3 -smp > >>> sockets=2,cores=2,threads=1 -usb -usbdevice mouse -usbdevice tablet > >>> -soundhw all > >> > >> And which test did trigger use-after-free, even with all previous > >> patches? > > > > I will try to extract a new reproducer now. > > Ok, I does not seem to see any crashes except the timer hangs below. > Let's consider all other bugs as fixed. I will report anything new > that I see separately. OK, good to hear. > > Meanwhile, can you try to reproduce this one: > > https://groups.google.com/forum/#!msg/syzkaller/bbtG9_h1ONU/CPLblMC6FAAJ > > ? I run the program in a tight parallel loop. I could reproduce this after your suggestion with parallel runs. This seems specific to hrtimer. Possibly it's not about the snd-timer core itself. Could you check whether this doesn't happen when CONFIG_SND_HRTIMER isn't set? thanks, Takashi