From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755279AbeDFPBx (ORCPT ); Fri, 6 Apr 2018 11:01:53 -0400 Received: from mail-io0-f193.google.com ([209.85.223.193]:46713 "EHLO mail-io0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755205AbeDFPBu (ORCPT ); Fri, 6 Apr 2018 11:01:50 -0400 X-Google-Smtp-Source: AIpwx48ATDl9wNWztPjtxTIAaFHFrT3xkEL9StbmvAG+TL9z7OFuLsyWGYClkhGT18fes7jr6gtORw== Subject: Re: WARNING: lock held when returning to user space! To: Dmitry Vyukov Cc: syzbot , linux-block@vger.kernel.org, LKML , syzkaller-bugs@googlegroups.com, Omar Sandoval References: <00000000000082922905692da9e1@google.com> <0e998b77-14f0-aee0-8d32-bc1dd96fcc4c@kernel.dk> From: Jens Axboe Message-ID: <63121c85-f417-cde8-510d-f275dbe81c4d@kernel.dk> Date: Fri, 6 Apr 2018 09:01:46 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/6/18 8:57 AM, Dmitry Vyukov wrote: > On Fri, Apr 6, 2018 at 4:27 PM, Jens Axboe wrote: >> On 4/6/18 7:02 AM, syzbot wrote: >>> Hello, >>> >>> syzbot hit the following crash on upstream commit >>> 38c23685b273cfb4ccf31a199feccce3bdcb5d83 (Fri Apr 6 04:29:35 2018 +0000) >>> Merge tag 'armsoc-drivers' of >>> git://git.kernel.org/pub/scm/linux/kernel/git/arm/arm-soc >>> syzbot dashboard link: >>> https://syzkaller.appspot.com/bug?extid=31e8daa8b3fc129e75f2 >>> >>> So far this crash happened 9 times on upstream. >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?id=6407930337296384 >>> syzkaller reproducer: >>> https://syzkaller.appspot.com/x/repro.syz?id=4942413340606464 >>> Raw console output: >>> https://syzkaller.appspot.com/x/log.txt?id=4764483918495744 >>> Kernel config: >>> https://syzkaller.appspot.com/x/.config?id=-5813481738265533882 >>> compiler: gcc (GCC) 8.0.1 20180301 (experimental) >>> >>> IMPORTANT: if you fix the bug, please add the following tag to the commit: >>> Reported-by: syzbot+31e8daa8b3fc129e75f2@syzkaller.appspotmail.com >>> It will help syzbot understand when the bug is fixed. See footer for >>> details. >>> If you forward the report, please keep this part and the footer. >>> >>> >>> ================================================ >>> WARNING: lock held when returning to user space! >>> 4.16.0+ #3 Not tainted >>> ------------------------------------------------ >>> syzkaller433111/4462 is leaving the kernel with locks still held! >>> 1 lock held by syzkaller433111/4462: >>> #0: 0000000003a06fae (&lo->lo_ctl_mutex/1){+.+.}, at: lo_ioctl+0x8d/0x1ec0 >>> drivers/block/loop.c:1363 >> >> Is this a new regression? Omar did just fiddle with the locking a bit, >> seems suspicious. > > Looking at: > https://syzkaller.appspot.com/bug?extid=31e8daa8b3fc129e75f2 > It first happened 4 hours ago and 9 times since then, so probably a > just introduced regression. After writing that, I saw the discussion in another thread ("INFO: task hung in lo_ioctl"), so I think we can definitely say that it's a recently introduced regression in loop due to the killable lock changes. -- Jens Axboe