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, USER_AGENT_SANE_1 autolearn=ham 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 297C6C7618B for ; Fri, 26 Jul 2019 16:15:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 07AF3218DA for ; Fri, 26 Jul 2019 16:15:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728396AbfGZQPf (ORCPT ); Fri, 26 Jul 2019 12:15:35 -0400 Received: from foss.arm.com ([217.140.110.172]:46896 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726655AbfGZQPf (ORCPT ); Fri, 26 Jul 2019 12:15:35 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7F570337; Fri, 26 Jul 2019 09:15:34 -0700 (PDT) Received: from arrakis.emea.arm.com (arrakis.cambridge.arm.com [10.1.196.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 457483F71F; Fri, 26 Jul 2019 09:15:33 -0700 (PDT) Date: Fri, 26 Jul 2019 17:15:31 +0100 From: Catalin Marinas To: Dmitry Vyukov Cc: syzbot , alexandre.belloni@free-electrons.com, LKML , Linux-MM , nicolas.ferre@atmel.com, Rob Herring , sre@kernel.org, syzkaller-bugs Subject: Re: memory leak in vq_meta_prefetch Message-ID: <20190726161530.GE2368@arrakis.emea.arm.com> References: <00000000000052ad6b058e722ba4@google.com> <20190726130013.GC2368@arrakis.emea.arm.com> <20190726155732.GA30211@e109758.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 26, 2019 at 06:05:32PM +0200, Dmitry Vyukov wrote: > On Fri, Jul 26, 2019 at 5:57 PM Catalin Marinas wrote: > > > > On Fri, Jul 26, 2019 at 05:20:55PM +0200, Dmitry Vyukov wrote: > > > On Fri, Jul 26, 2019 at 3:00 PM Catalin Marinas wrote: > > > > On Wed, Jul 24, 2019 at 12:18:07PM -0700, syzbot wrote: > > > > > syzbot found the following crash on: > > > > > > > > > > HEAD commit: c6dd78fc Merge branch 'x86-urgent-for-linus' of git://git... > > > > > git tree: upstream > > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=15fffef4600000 > > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=8de7d700ea5ac607 > > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=a871c1e6ea00685e73d7 > > > > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=127b0334600000 > > > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=12609e94600000 > > > > > > > > > > The bug was bisected to: > > > > > > > > > > commit 0e5f7d0b39e1f184dc25e3adb580c79e85332167 > > > > > Author: Nicolas Ferre > > > > > Date: Wed Mar 16 13:19:49 2016 +0000 > > > > > > > > > > ARM: dts: at91: shdwc binding: add new shutdown controller documentation > > > > > > > > That's another wrong commit identification (a documentation patch should > > > > not cause a memory leak). > > > > > > > > I don't really think kmemleak, with its relatively high rate of false > > > > positives, is suitable for automated testing like syzbot. You could > > > > > > Do you mean automated testing in general, or bisection only? > > > The wrong commit identification is related to bisection only, but you > > > generalized it to automated testing in general. So which exactly you > > > mean? > > > > I probably meant both. In terms of automated testing and reporting, if > > the false positives rate is high, people start ignoring the reports. So > > it requires some human checking first (or make the tool more robust). [...] > Do you have any data points wrt automated testing in general? This > disagrees with what I see. I'm fine with automated testing in general. Just that automated reporting for kmemleak could be improved a bit to reduce the false positives (e.g. run it a few times to confirm that it is a real leak). Just to be clear, I'm not talking about syzbot in general, it's a great tool, only about improving kmemleak reporting and bisecting. -- Catalin