From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1BBC1C433F5 for ; Mon, 3 Sep 2018 13:37:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B981C20843 for ; Mon, 3 Sep 2018 13:37:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B981C20843 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727397AbeICR5Z (ORCPT ); Mon, 3 Sep 2018 13:57:25 -0400 Received: from mx2.suse.de ([195.135.220.15]:44034 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725991AbeICR5Z (ORCPT ); Mon, 3 Sep 2018 13:57:25 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay1.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id E807AAD86; Mon, 3 Sep 2018 13:37:09 +0000 (UTC) Date: Mon, 03 Sep 2018 15:37:09 +0200 Message-ID: From: Takashi Iwai To: Dmitry Vyukov Cc: syzbot , alsa-devel-bounces@alsa-project.org, alsa-devel@alsa-project.org, LKML , Jaroslav Kysela , syzkaller-bugs Subject: Re: KMSAN: uninit-value in snd_midi_event_encode_byte In-Reply-To: References: <000000000000a25ae50574f76ff0@google.com> 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/26 (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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 03 Sep 2018 15:33:12 +0200, Dmitry Vyukov wrote: > > On Mon, Sep 3, 2018 at 3:29 PM, Takashi Iwai wrote: > > On Mon, 03 Sep 2018 15:22:42 +0200, > > syzbot wrote: > >> > >> > On Mon, 03 Sep 2018 03:53:03 +0200, > >> > syzbot wrote: > >> > >> >> syzbot has found a reproducer for the following crash on: > >> > >> >> HEAD commit: 28f0ca98eadf kmsan: don't instrument > >> >> do_syscall_64() and _.. > >> >> git tree: https://github.com/google/kmsan.git/master > >> >> console output: https://syzkaller.appspot.com/x/log.txt?x=10556c92400000 > >> >> kernel config: > >> >> https://syzkaller.appspot.com/x/.config?x=3431f03869413153 > >> >> dashboard link: > >> >> https://syzkaller.appspot.com/bug?extid=194dffdb8b22fc5d207a > >> >> compiler: clang version 8.0.0 (trunk 339414) > >> >> syz repro: > >> >> https://syzkaller.appspot.com/x/repro.syz?x=123a520a400000 > >> >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16068dc1400000 > >> > >> >> IMPORTANT: if you fix the bug, please add the following tag to the > >> >> commit: > >> >> Reported-by: syzbot+194dffdb8b22fc5d207a@syzkaller.appspotmail.com > >> > >> >> ================================================================== > >> >> BUG: KMSAN: uninit-value in snd_midi_event_encode_byte+0x569/0xff0 > >> >> sound/core/seq/seq_midi_event.c:195 > >> >> CPU: 1 PID: 1659 Comm: kworker/1:1H Not tainted 4.19.0-rc1+ #40 > >> >> Hardware name: Google Google Compute Engine/Google Compute Engine, > >> >> BIOS Google 01/01/2011 > >> >> Workqueue: events_highpri snd_vmidi_output_work > >> >> Call Trace: > >> >> __dump_stack lib/dump_stack.c:77 [inline] > >> >> dump_stack+0x14b/0x190 lib/dump_stack.c:113 > >> >> kmsan_report+0x183/0x2b0 mm/kmsan/kmsan.c:956 > >> >> __msan_warning+0x70/0xc0 mm/kmsan/kmsan_instr.c:645 > >> >> snd_midi_event_encode_byte+0x569/0xff0 > >> >> sound/core/seq/seq_midi_event.c:195 > >> >> snd_vmidi_output_work+0x34e/0x5b0 sound/core/seq/seq_virmidi.c:161 > >> >> process_one_work+0x1605/0x1f40 kernel/workqueue.c:2153 > >> >> worker_thread+0x11a2/0x2590 kernel/workqueue.c:2296 > >> >> kthread+0x465/0x4a0 kernel/kthread.c:247 > >> >> ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:416 > >> > >> >> Uninit was stored to memory at: > >> >> kmsan_save_stack_with_flags mm/kmsan/kmsan.c:256 [inline] > >> >> kmsan_save_stack mm/kmsan/kmsan.c:271 [inline] > >> >> kmsan_internal_chain_origin+0x128/0x210 mm/kmsan/kmsan.c:573 > >> >> __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:482 > >> >> __snd_rawmidi_transmit_peek sound/core/rawmidi.c:1103 [inline] > >> >> snd_rawmidi_transmit+0xa75/0xbf0 sound/core/rawmidi.c:1228 > >> >> snd_vmidi_output_work+0x2ac/0x5b0 sound/core/seq/seq_virmidi.c:159 > >> >> process_one_work+0x1605/0x1f40 kernel/workqueue.c:2153 > >> >> worker_thread+0x11a2/0x2590 kernel/workqueue.c:2296 > >> >> kthread+0x465/0x4a0 kernel/kthread.c:247 > >> >> ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:416 > >> > >> >> Uninit was created at: > >> >> kmsan_save_stack_with_flags mm/kmsan/kmsan.c:256 [inline] > >> >> kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:181 > >> >> kmsan_kmalloc+0x98/0x100 mm/kmsan/kmsan_hooks.c:91 > >> >> __kmalloc_node+0x7bf/0x11c0 mm/slub.c:3828 > >> >> kmalloc_node include/linux/slab.h:555 [inline] > >> >> kvmalloc_node+0x19d/0x3e0 mm/util.c:423 > >> >> kvmalloc include/linux/mm.h:577 [inline] > >> >> snd_rawmidi_runtime_create sound/core/rawmidi.c:132 [inline] > >> >> open_substream+0x3c8/0xaa0 sound/core/rawmidi.c:276 > >> >> rawmidi_open_priv+0x347/0x1000 sound/core/rawmidi.c:327 > >> >> snd_rawmidi_open+0x7d4/0x1120 sound/core/rawmidi.c:424 > >> >> soundcore_open+0x9be/0xa60 sound/sound_core.c:597 > >> >> chrdev_open+0xc26/0xdb0 fs/char_dev.c:417 > >> >> do_dentry_open+0xce6/0x1740 fs/open.c:771 > >> >> vfs_open+0xaf/0xe0 fs/open.c:880 > >> >> do_last fs/namei.c:3418 [inline] > >> >> path_openat+0x1799/0x6870 fs/namei.c:3534 > >> >> do_filp_open+0x259/0x610 fs/namei.c:3564 > >> >> do_sys_open+0x630/0x940 fs/open.c:1063 > >> >> __do_sys_open fs/open.c:1081 [inline] > >> >> __se_sys_open+0xad/0xc0 fs/open.c:1076 > >> >> __x64_sys_open+0x4a/0x70 fs/open.c:1076 > >> >> do_syscall_64+0xb8/0x100 arch/x86/entry/common.c:291 > >> >> entry_SYSCALL_64_after_hwframe+0x63/0xe7 > >> >> ================================================================== > >> > >> > This looks like some small race at virmidi reading and the buffer > >> > handling, which should be almost harmless by itself. > >> > Nevertheless, the fix should be easy, just replacing kvmalloc() with > >> > kvzalloc(), as below. > >> > >> > Let's check whether this works. > >> > >> > #syz test: > >> > git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git > >> > topic/rawmidi-fixes > >> > >> KMSAN bugs can only be tested on https://github.com/google/kmsan.git tree > >> because KMSAN tool is not upstreamed yet. > >> See > >> https://github.com/google/syzkaller/blob/master/docs/syzbot.md#kmsan-bugs > >> for details. > > > > So how is the procedure to test a patch for bugs spotted by KMSAN? > > > > In this case, the fix is trivial, so I can put it to my tree for the > > next pull request. Of course, it'd be better if it can be confirmed > > to work beforehand... > > https://github.com/google/syzkaller/blob/master/docs/syzbot.md#kmsan-bugs > > Which means you need to attach a patch because it's not in that tree. OK, it would have been helpful if the description there was more clear :) And no automated way for that? I mean, I already attached patch in the previous reply (together with syz-magic command to point the git branch URL). Do I need anything else? thanks, Takashi