From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751146AbdKSSuZ (ORCPT ); Sun, 19 Nov 2017 13:50:25 -0500 Received: from mail-pf0-f193.google.com ([209.85.192.193]:43561 "EHLO mail-pf0-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750954AbdKSSuY (ORCPT ); Sun, 19 Nov 2017 13:50:24 -0500 X-Google-Smtp-Source: AGs4zMZyGYy8WXYpegYLgYqK4m60EFzXtUED44UDdSB5rLc70ydDjKx41EMNbW/igvICMMka6umhtw== Subject: Re: possible deadlock in blk_trace_remove To: syzbot , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, rostedt@goodmis.org, syzkaller-bugs@googlegroups.com References: <001a1141f8dc4440a9055e53896e@google.com> From: Jens Axboe Message-ID: <4d09f529-7cf9-7267-7dcb-122ecc957e7d@kernel.dk> Date: Sun, 19 Nov 2017 11:50:20 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <001a1141f8dc4440a9055e53896e@google.com> 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 11/19/2017 03:36 AM, syzbot wrote: > Hello, > > syzkaller hit the following crash on > d9e0e63d9a6f88440eb201e1491fcf730272c706 > 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.> > > Use struct sctp_sack_info instead > > ============================================ > WARNING: possible recursive locking detected > 4.14.0-rc8-next-20171110+ #40 Not tainted > -------------------------------------------- > syz-executor6/21462 is trying to acquire lock: > (&q->blk_trace_mutex){+.+.}, at: [] > blk_trace_remove+0x21/0x40 kernel/trace/blktrace.c:373 > > but task is already holding lock: > (&q->blk_trace_mutex){+.+.}, at: [] > blk_trace_setup+0x38/0x70 kernel/trace/blktrace.c:606 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&q->blk_trace_mutex); > lock(&q->blk_trace_mutex); The below should fix it. diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c index 206e0e2ace53..f224985de5fa 100644 --- a/kernel/trace/blktrace.c +++ b/kernel/trace/blktrace.c @@ -591,7 +591,7 @@ static int __blk_trace_setup(struct request_queue *q, char *name, dev_t dev, return ret; if (copy_to_user(arg, &buts, sizeof(buts))) { - blk_trace_remove(q); + __blk_trace_remove(q); return -EFAULT; } return 0; @@ -637,7 +637,7 @@ static int compat_blk_trace_setup(struct request_queue *q, char *name, return ret; if (copy_to_user(arg, &buts.name, ARRAY_SIZE(buts.name))) { - blk_trace_remove(q); + __blk_trace_remove(q); return -EFAULT; } -- Jens Axboe