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=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, 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 62704C2D0C2 for ; Sat, 4 Jan 2020 11:09:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E8C821734 for ; Sat, 4 Jan 2020 11:09:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725805AbgADLJK (ORCPT ); Sat, 4 Jan 2020 06:09:10 -0500 Received: from www262.sakura.ne.jp ([202.181.97.72]:56413 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725796AbgADLJK (ORCPT ); Sat, 4 Jan 2020 06:09:10 -0500 Received: from fsav304.sakura.ne.jp (fsav304.sakura.ne.jp [153.120.85.135]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 004B97TD090039; Sat, 4 Jan 2020 20:09:07 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav304.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav304.sakura.ne.jp); Sat, 04 Jan 2020 20:09:07 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav304.sakura.ne.jp) Received: from [192.168.1.9] (softbank126040062084.bbtec.net [126.40.62.84]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 004B927x089997 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sat, 4 Jan 2020 20:09:06 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: INFO: rcu detected stall in sys_sendfile64 To: Dmitry Vyukov Cc: syzbot , syzkaller-bugs , Ingo Molnar , Peter Zijlstra , James Morris , LKML , linux-security-module@vger.kernel.org, "Serge E. Hallyn" References: <000000000000e728ec057d5c9d90@google.com> From: Tetsuo Handa Message-ID: Date: Sat, 4 Jan 2020 20:09:00 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.3.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On 2018/12/20 3:42, Dmitry Vyukov wrote: > On Wed, Dec 19, 2018 at 11:13 AM Tetsuo Handa > wrote: >> >> On 2018/12/19 18:27, syzbot wrote: >>> HEAD commit: ddfbab46539f Merge tag 'scsi-fixes' of git://git.kernel.or.. >>> git tree: upstream >>> console output: https://syzkaller.appspot.com/x/log.txt?x=15b87fa3400000 >>> kernel config: https://syzkaller.appspot.com/x/.config?x=861a3573f4e78ba1 >>> dashboard link: https://syzkaller.appspot.com/bug?extid=bcad772bbc241b4c6147 >>> compiler: gcc (GCC) 8.0.1 20180413 (experimental) >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13912ccd400000 >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=145781db400000 >> >> This is not a LSM problem, for the reproducer is calling >> sched_setattr(SCHED_DEADLINE) with very large values. >> >> sched_setattr(0, {size=0, sched_policy=0x6 /* SCHED_??? */, sched_flags=0, sched_nice=0, sched_priority=0, sched_runtime=2251799813724439, sched_deadline=4611686018427453437, sched_period=0}, 0) = 0 >> >> I think that this problem is nothing but an insane sched_setattr() parameter. >> >> #syz invalid > > Note there was another one with sched_setattr, which turned out to be > some serious problem in kernel (sched_setattr should not cause CPU > stall for 3 minutes): > INFO: rcu detected stall in do_idle > https://syzkaller.appspot.com/bug?extid=385468161961cee80c31 > https://groups.google.com/forum/#!msg/syzkaller-bugs/crrfvusGtwI/IoD_zus4BgAJ > > Maybe it another incarnation of the same bug, that one is still not fixed. > Can we let syzbot blacklist sched_setattr() for now? There are many stall reports doing sched_setattr(SCHED_RR) which makes it difficult to find stall reports not using sched_setattr().