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=-12.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 6755DC433DB for ; Thu, 25 Mar 2021 19:10:17 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 07B2361A2B for ; Thu, 25 Mar 2021 19:10:16 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 07B2361A2B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 939D06B006C; Thu, 25 Mar 2021 15:10:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9104C6B006E; Thu, 25 Mar 2021 15:10:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7B3A96B0070; Thu, 25 Mar 2021 15:10:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0135.hostedemail.com [216.40.44.135]) by kanga.kvack.org (Postfix) with ESMTP id 626096B006C for ; Thu, 25 Mar 2021 15:10:16 -0400 (EDT) Received: from smtpin04.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 0CE7CEFAE for ; Thu, 25 Mar 2021 19:10:16 +0000 (UTC) X-FDA: 77959337232.04.E3E6646 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf25.hostedemail.com (Postfix) with ESMTP id 737656000136 for ; Thu, 25 Mar 2021 19:10:12 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 3D1D161A28; Thu, 25 Mar 2021 19:10:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1616699412; bh=2Q1sdWBYJRIs3LEAmp9AiVKbXjQPiGRodgRuIomqKp0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dCzqJLsNd5I+rC/aScks7FIuG8oSmB4LIL1oy+SBlT+rE+oAuo6AVbQsv8rp566aB g7qFW6EoNbBD9DSNUjPgv8gJGDly4jakTAKspIO4HsiR3lgsVca5JdOT3gnemCiesL vIChCCpsahBpUZqZgU58NTHBUyNho3pGHsoRDtDZvSaEHx4wJAiyL/gHyyxWZpgOW2 0f+ds9H2FWxs497vSXu/NG2SMuqGBjbnuWX63Vjm1CpOnonWKQhII9gVHp5YtcX9Y+ 4b/cHNFYjXXrNlEUE2aTkii+kgn19/CIK6uKExXgB+5iGgIcq6Hlu3l0plmhdSz3Tp q9r8RasJAoVBA== Date: Thu, 25 Mar 2021 19:10:07 +0000 From: Will Deacon To: Dmitry Vyukov Cc: syzbot , kernel-team@android.com, Andrew Morton , LKML , Linux-MM , syzkaller-bugs , Linux ARM , syzkaller Subject: Re: [syzbot] BUG: soft lockup in do_wp_page (4) Message-ID: <20210325191006.GE15860@willie-the-truck> References: <000000000000ce4c9505bdd4a48f@google.com> <20210325182046.GA15860@willie-the-truck> 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-Stat-Signature: hdtaj8tuz5tas8whtfpgmbc9qeewsjeu X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 737656000136 Received-SPF: none (kernel.org>: No applicable sender policy available) receiver=imf25; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616699412-512569 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 Thu, Mar 25, 2021 at 07:34:54PM +0100, Dmitry Vyukov wrote: > On Thu, Mar 25, 2021 at 7:20 PM Will Deacon wrote: > > > > On Thu, Mar 18, 2021 at 08:34:16PM +0100, Dmitry Vyukov wrote: > > > On Thu, Mar 18, 2021 at 8:31 PM syzbot > > > wrote: > > > > > > > > Hello, > > > > > > > > syzbot found the following issue on: > > > > > > > > HEAD commit: bf152b0b Merge tag 'for_linus' of git://git.kernel.org/pub.. > > > > git tree: upstream > > > > console output: https://syzkaller.appspot.com/x/log.txt?x=17d5264ed00000 > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=2c9917c41f0bc04b > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=0b036374a865ba0efa8e > > > > userspace arch: arm64 > > > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > > > Reported-by: syzbot+0b036374a865ba0efa8e@syzkaller.appspotmail.com > > > > > > > > watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [syz-executor.1:3684] > > > > > > +Will, arm > > > > > > If I am reading this commit correctly, this is caused by: > > > > > > commit cae118b6acc309539b33339e846cbb19187c164c > > > Author: Will Deacon > > > Date: Wed Mar 3 13:49:27 2021 +0000 > > > arm64: Drop support for CMDLINE_EXTEND > > > > > > syzbot passes lots of critical things in CONFIG_CMDLINE: > > > https://github.com/google/syzkaller/blob/c3c81c94865791469d376eba84f4a2d7763d3f71/dashboard/config/linux/upstream-arm64-kasan.config#L495 > > > but also wants the bootloader args to be appended. > > > What is the way to do it now? > > > > For now, there isn't a way to do it with CONFIG_CMDLINE, so I think you can > > either: > > > > * Revert my patch for your kernels > > * Pass the arguments via QEMU's -append option > > * Take a look at one of the series which should hopefully add this > > functionality back (but with well-defined semantics) [1] [2] > > Unfortunately none of these work for syzbot (and I assume other > testing environments). > > syzbot does not support custom patches by design: > http://bit.do/syzbot#no-custom-patches > As any testing system, it tests the official trees. > > It's not humans who start these VMs, so it's not as easy as changing > the command line after typing... > There is no support for passing args specifically to qemu, syzkaller > support not just qemu, so these things are specifically localized in > the config. Additionally there is an issue of communicating all these > scattered details to developers in bug reports. Currently syzbot > reports the kernel config and it as well captures command line. > > Could you revert the patch? Is there any point in removing the > currently supported feature before the new feature lands? Well, we only just merged it (in 5.10 I think?), and the semantics of the new version will be different, so I really don't see the value in supporting both (even worse, Android has its own implementation which is different again). The timeline was: we merged CMDLINE_EXTEND, then we noticed it was broken, my fixes were rejected, so we removed the feature rather than support the broken version. In the relatively small window while it was merged, syzbot started using it :( So I really think the best bet is to wait until the patches are sorted out. I think Christophe is about to spin a new version, and I reviewed his last copy, so I don't see this being far off, Will