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[140.211.169.12]) by mx.google.com with ESMTPS id k3si7352359pfb.100.2019.03.11.23.25.45 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Mar 2019 23:25:45 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) client-ip=140.211.169.12; Authentication-Results: mx.google.com; spf=pass (google.com: domain of akpm@linux-foundation.org designates 140.211.169.12 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from localhost.localdomain (c-73-223-200-170.hsd1.ca.comcast.net [73.223.200.170]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 60EA2B1F; Tue, 12 Mar 2019 06:25:44 +0000 (UTC) Date: Mon, 11 Mar 2019 23:25:41 -0700 From: Andrew Morton To: Dmitry Vyukov Cc: syzbot , cgroups@vger.kernel.org, Johannes Weiner , LKML , Linux-MM , Michal Hocko , Michal Hocko , Stephen Rothwell , Shakeel Butt , syzkaller-bugs , Vladimir Davydov Subject: Re: KASAN: null-ptr-deref Read in reclaim_high Message-Id: <20190311232541.db8571d2e3e0ca636785f31f@linux-foundation.org> In-Reply-To: References: <0000000000001fd5780583d1433f@google.com> <20190311163747.f56cceebd9c2661e4519bdfc@linux-foundation.org> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit 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 Tue, 12 Mar 2019 07:08:38 +0100 Dmitry Vyukov wrote: > On Tue, Mar 12, 2019 at 12:37 AM Andrew Morton > wrote: > > > > On Mon, 11 Mar 2019 06:08:01 -0700 syzbot wrote: > > > > > syzbot has bisected this bug to: > > > > > > commit 29a4b8e275d1f10c51c7891362877ef6cffae9e7 > > > Author: Shakeel Butt > > > Date: Wed Jan 9 22:02:21 2019 +0000 > > > > > > memcg: schedule high reclaim for remote memcgs on high_work > > > > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=155bf5db200000 > > > start commit: 29a4b8e2 memcg: schedule high reclaim for remote memcgs on.. > > > git tree: linux-next > > > final crash: https://syzkaller.appspot.com/x/report.txt?x=175bf5db200000 > > > console output: https://syzkaller.appspot.com/x/log.txt?x=135bf5db200000 > > > kernel config: https://syzkaller.appspot.com/x/.config?x=611f89e5b6868db > > > dashboard link: https://syzkaller.appspot.com/bug?extid=fa11f9da42b46cea3b4a > > > userspace arch: amd64 > > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14259017400000 > > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=141630a0c00000 > > > > > > Reported-by: syzbot+fa11f9da42b46cea3b4a@syzkaller.appspotmail.com > > > Fixes: 29a4b8e2 ("memcg: schedule high reclaim for remote memcgs on > > > high_work") > > > > The following patch > > memcg-schedule-high-reclaim-for-remote-memcgs-on-high_work-v3.patch > > might have fixed this. Was it applied? > > Hi Andrew, > > You mean if the patch was applied during the bisection? > No, it wasn't. Bisection is very specifically done on the same tree > where the bug was hit. There are already too many factors that make > the result flaky/wrong/inconclusive without changing the tree state. > Now, if syzbot would know about any pending fix for this bug, then it > would not do the bisection at all. But it have not seen any patch in > upstream/linux-next with the Reported-by tag, nor it received any syz > fix commands for this bugs. Should have been it aware of the fix? How? memcg-schedule-high-reclaim-for-remote-memcgs-on-high_work-v3.patch was added to linux-next on Jan 10. I take it that this bug was hit when testing the entire linux-next tree, so we can assume that memcg-schedule-high-reclaim-for-remote-memcgs-on-high_work-v3.patch does not fix it, correct? In which case, over to Shakeel!