From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751936AbcFXOfr (ORCPT ); Fri, 24 Jun 2016 10:35:47 -0400 Received: from mx2.suse.de ([195.135.220.15]:56391 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751698AbcFXOfo (ORCPT ); Fri, 24 Jun 2016 10:35:44 -0400 Date: Fri, 24 Jun 2016 16:35:42 +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 15:48:53 +0200, Dmitry Vyukov wrote: > > On Fri, Jun 24, 2016 at 3:33 PM, Takashi Iwai wrote: > > On Tue, 21 Jun 2016 19:41:28 +0200, > > Dmitry Vyukov wrote: > >> > >> On Mon, Jun 6, 2016 at 6:39 PM, Takashi Iwai wrote: > >> > 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? > >> > >> What do you mean? > >> Here are the syscalls in the program: > >> > >> r[2] = syscall(SYS_open, "/dev/audio", 0xa40ul, 0, 0, 0); > >> // r[2] is in the descriptor passed to SYS_poll > >> r[15] = syscall(SYS_poll, 0x2001dde8ul, 0x4ul, 0x8ul, 0, 0, 0); > >> r[18] = syscall(SYS_readv, r[2], 0x20dc13c0ul, 0x1ul, 0, 0, 0); > >> r[19] = syscall(SYS_read, r[2], 0x20dbefe0ul, 0x20ul, 0, 0, 0); > > > > I meant some nice way to decode these magic numbers to be more > > understandable :) > > Short term, run it under strace. It should show file names, decode > most of flags and structs. Alright, thanks. Takashi