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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED 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 9B24CC43381 for ; Tue, 12 Mar 2019 06:25:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 695C9214D8 for ; Tue, 12 Mar 2019 06:25:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1552371947; bh=Yo77a/j/DxyOgAnZMiznLHziwuvOKmQPZUxgFBdJk/A=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=Jq/0wp3yg45Y1OJmDUiA0aKWcHLVl/rt5O20UGCTeFHrufi210kDjJq4KWN0cf210 TmUIkARdadG1lu04PRMRw3DzaY8N7kHCV3iPr2fIwsW6LR1OeTa0uI7iKuu5c3ZuSb V9p5GpcBaIo3KwaUo1HV0lTddMwboEZl0FCAFcTw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727122AbfCLGZq (ORCPT ); Tue, 12 Mar 2019 02:25:46 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36634 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725855AbfCLGZp (ORCPT ); Tue, 12 Mar 2019 02:25:45 -0400 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 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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!