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[217.140.110.172]) by mx.google.com with ESMTP id ny24si11495741ejb.78.2019.07.26.09.15.35 for ; Fri, 26 Jul 2019 09:15:35 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=catalin.marinas@arm.com 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) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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