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[217.140.110.172]) by mx.google.com with ESMTP id i13si10728982eja.216.2019.07.26.06.00.18 for ; Fri, 26 Jul 2019 06:00:18 -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 70923337; Fri, 26 Jul 2019 06:00:17 -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 357033F694; Fri, 26 Jul 2019 06:00:16 -0700 (PDT) Date: Fri, 26 Jul 2019 14:00:14 +0100 From: Catalin Marinas To: syzbot Cc: alexandre.belloni@free-electrons.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, nicolas.ferre@atmel.com, robh@kernel.org, sre@kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: memory leak in vq_meta_prefetch Message-ID: <20190726130013.GC2368@arrakis.emea.arm.com> References: <00000000000052ad6b058e722ba4@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <00000000000052ad6b058e722ba4@google.com> 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 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 reduce the false positives if you add support for scanning in stop_machine(). Otherwise, in order to avoid locking the kernel for long periods, kmemleak runs concurrently with other threads (even on the current CPU) and under high load, pointers are missed (e.g. they are in CPU registers rather than stack). -- Catalin