From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750982AbdE1Ooe (ORCPT ); Sun, 28 May 2017 10:44:34 -0400 Received: from bh-25.webhostbox.net ([208.91.199.152]:43367 "EHLO bh-25.webhostbox.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750865AbdE1Ood (ORCPT ); Sun, 28 May 2017 10:44:33 -0400 Subject: Re: mips qemu test failures in -next due to "kthread: Fix use-after-free if kthread fork fails" To: Vegard Nossum Cc: Oleg Nesterov , Jamie Iles , Thomas Gleixner , linux-kernel@vger.kernel.org, Linus Torvalds References: <20170527175612.GA22714@roeck-us.net> From: Guenter Roeck Message-ID: <8c778771-ef3c-8b42-b205-f1528fe114a9@roeck-us.net> Date: Sun, 28 May 2017 07:44:30 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated_sender: linux@roeck-us.net X-OutGoing-Spam-Status: No, score=-1.0 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - bh-25.webhostbox.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - roeck-us.net X-Get-Message-Sender-Via: bh-25.webhostbox.net: authenticated_id: linux@roeck-us.net X-Authenticated-Sender: bh-25.webhostbox.net: linux@roeck-us.net X-Source: X-Source-Args: X-Source-Dir: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +cc Linus, as mainline is now affected. On 05/28/2017 04:45 AM, Vegard Nossum wrote: > On 05/27/17 19:56, Guenter Roeck wrote: >> Hi, >> >> my qemu testis of mips images are failing in -next. Symptom is a hang during >> boot; see http://kerneltests.org/builders/qemu-mips-next for some examples. >> >> I bisected the problem in next-20170526. It points to commit 4d6501dce079c >> ("kthread: Fix use-after-free if kthread fork fails"). Reverting that patch >> fixes the problem. >> >> Bisect log is attached. > > Hi, > > Thanks for the report and sorry for the breakage :-/ > > I can't immediately spot what's going wrong, but I am able to reproduce > it on mips so I will try to debug. > > Are you sure it's this commit, though? I checked out linus/master and > I get a boot hang even after reverting it. > Reverting the patch fixed the problem for me in -next. The last mainline build on my test system was with v4.12-rc2-228-gc86daad, which was fine except for the known build breakages (frv, hexagon) and the known tracebacks in crisv32 WARNING: CPU: 0 PID: 1 at drivers/mtd/mtdcore.c:734 mtd_device_parse_register+0x17a/0x1aa and ppc refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 1 at lib/refcount.c:184 refcount_sub_and_test+0x84/0xe0 It may well be that something else is broken in mainline. The build of v4.12-rc2-284-g249f1ef on my builders isn't complete yet. We'll see in a couple of hours if there is other damage. I'll bisect later today if necessary. Guenter