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=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_MUTT autolearn=unavailable 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 A2711C48BD3 for ; Wed, 26 Jun 2019 18:43:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 820F020659 for ; Wed, 26 Jun 2019 18:43:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726563AbfFZSnS (ORCPT ); Wed, 26 Jun 2019 14:43:18 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:34866 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726227AbfFZSnR (ORCPT ); Wed, 26 Jun 2019 14:43:17 -0400 Received: from callcc.thunk.org (guestnat-104-133-0-109.corp.google.com [104.133.0.109] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id x5QIgrkG019522 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 26 Jun 2019 14:42:54 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id E3B1A42002B; Wed, 26 Jun 2019 14:42:51 -0400 (EDT) Date: Wed, 26 Jun 2019 14:42:51 -0400 From: "Theodore Ts'o" To: syzbot Cc: adilger.kernel@dilger.ca, davem@davemloft.net, eladr@mellanox.com, idosch@mellanox.com, jiri@mellanox.com, john.stultz@linaro.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, tglx@linutronix.de Subject: Re: INFO: rcu detected stall in ext4_write_checks Message-ID: <20190626184251.GE3116@mit.edu> Mail-Followup-To: Theodore Ts'o , syzbot , adilger.kernel@dilger.ca, davem@davemloft.net, eladr@mellanox.com, idosch@mellanox.com, jiri@mellanox.com, john.stultz@linaro.org, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com, tglx@linutronix.de References: <000000000000d3f34b058c3d5a4f@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <000000000000d3f34b058c3d5a4f@google.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Jun 26, 2019 at 10:27:08AM -0700, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit: abf02e29 Merge tag 'pm-5.2-rc6' of git://git.kernel.org/pu.. > git tree: upstream > console output: https://syzkaller.appspot.com/x/log.txt?x=1435aaf6a00000 > kernel config: https://syzkaller.appspot.com/x/.config?x=e5c77f8090a3b96b > dashboard link: https://syzkaller.appspot.com/bug?extid=4bfbbf28a2e50ab07368 > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11234c41a00000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15d7f026a00000 > > The bug was bisected to: > > commit 0c81ea5db25986fb2a704105db454a790c59709c > Author: Elad Raz > Date: Fri Oct 28 19:35:58 2016 +0000 > > mlxsw: core: Add port type (Eth/IB) set API Um, so this doesn't pass the laugh test. > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=10393a89a00000 It looks like the automated bisection machinery got confused by two failures getting triggered by the same repro; the symptoms changed over time. Initially, the failure was: crashed: INFO: rcu detected stall in {sys_sendfile64,ext4_file_write_iter} Later, the failure changed to something completely different, and much earlier (before the test was even started): run #5: basic kernel testing failed: failed to copy test binary to VM: failed to run ["scp" "-P" "22" "-F" "/dev/null" "-o" "UserKnownHostsFile=/dev/null" "-o" "BatchMode=yes" "-o" "IdentitiesOnly=yes" "-o" "StrictHostKeyChecking=no" "-o" "ConnectTimeout=10" "-i" "/syzkaller/jobs/linux/workdir/image/key" "/tmp/syz-executor216456474" "root@10.128.15.205:./syz-executor216456474"]: exit status 1 Connection timed out during banner exchange lost connection Looks like an opportunity to improve the bisection engine? - Ted