From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752837AbdK2UvI (ORCPT ); Wed, 29 Nov 2017 15:51:08 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:36330 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752600AbdK2UvG (ORCPT ); Wed, 29 Nov 2017 15:51:06 -0500 Date: Wed, 29 Nov 2017 12:50:59 -0800 From: "Paul E. McKenney" To: Dmitry Vyukov Cc: Andrew Morton , syzbot , Christoph Lameter , Joonsoo Kim , LKML , Linux-MM , Pekka Enberg , David Rientjes , syzkaller-bugs@googlegroups.com, Herbert Xu Subject: Re: WARNING: suspicious RCU usage (3) Reply-To: paulmck@linux.vnet.ibm.com References: <94eb2c03c9bcc3b127055f11171d@google.com> <20171128133026.cf03471c99d7a0c827c5a21c@linux-foundation.org> <20171128223041.GZ3624@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 17112920-0044-0000-0000-000003B72140 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008123; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000242; SDB=6.00953059; UDB=6.00481522; IPR=6.00733138; BA=6.00005721; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00018255; XFM=3.00000015; UTC=2017-11-29 20:51:02 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17112920-0045-0000-0000-000007E64E61 Message-Id: <20171129205059.GI3624@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-11-29_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1711290269 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Nov 29, 2017 at 07:25:32AM +0100, Dmitry Vyukov wrote: > On Tue, Nov 28, 2017 at 11:30 PM, Paul E. McKenney > wrote: > > On Tue, Nov 28, 2017 at 01:30:26PM -0800, Andrew Morton wrote: > >> On Tue, 28 Nov 2017 12:45:01 -0800 syzbot wrote: > >> > >> > Hello, > >> > > >> > syzkaller hit the following crash on > >> > b0a84f19a5161418d4360cd57603e94ed489915e > >> > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master > >> > compiler: gcc (GCC) 7.1.1 20170620 > >> > .config is attached > >> > Raw console output is attached. > >> > > >> > Unfortunately, I don't have any reproducer for this bug yet. > >> > > >> > WARNING: suspicious RCU usage > >> > >> There's a bunch of other info which lockdep_rcu_suspicious() should > >> have printed out, but this trace doesn't have any of it. I wonder why. > > > > Yes, there should be more info printed, no idea why it would go missing. > > I think that's because while reporting "suspicious RCU usage" kernel hit: > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000074 > > and the rest of the report is actually about the NULL deref. > > syzkaller hits too many crashes at the same time. And it's a problem > for us. We get reports with corrupted/intermixed titles, > corrupted/intermixed bodies, reports with same titles but about > different bugs, etc. Got it, thank you! Thanx, Paul