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=-4.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no 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 6030BC433E1 for ; Wed, 29 Jul 2020 19:13:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4F55A20809 for ; Wed, 29 Jul 2020 19:13:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726820AbgG2TN3 convert rfc822-to-8bit (ORCPT ); Wed, 29 Jul 2020 15:13:29 -0400 Received: from mga01.intel.com ([192.55.52.88]:2252 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726710AbgG2TN3 (ORCPT ); Wed, 29 Jul 2020 15:13:29 -0400 IronPort-SDR: APilKWlAra2BRvFzKRAk5pYx9pOqQ1yAwQ89Ao3M3WQd21Fa+8RxR8qb2RMwT0BfP79ZIeiq+O AWe4moDyXe9g== X-IronPort-AV: E=McAfee;i="6000,8403,9697"; a="169609180" X-IronPort-AV: E=Sophos;i="5.75,411,1589266800"; d="scan'208";a="169609180" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jul 2020 12:13:29 -0700 IronPort-SDR: myaKcCtokUJMkzeggkpvAj5yxerRteQIEo9VLaiKhg7BXQhs0cG1Dr2nExr3NPQZHn5rKMBVyK g63hxz7RTLnw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,411,1589266800"; d="scan'208";a="490391579" Received: from askotian-mobl2.amr.corp.intel.com (HELO ellie) ([10.212.6.60]) by fmsmga006.fm.intel.com with ESMTP; 29 Jul 2020 12:13:28 -0700 From: Vinicius Costa Gomes To: "Zhang\, Qiang" , syzbot , "davem\@davemloft.net" , "fweisbec\@gmail.com" , "jhs\@mojatatu.com" , "jiri\@resnulli.us" , "linux-kernel\@vger.kernel.org" , "mingo\@kernel.org" , "netdev\@vger.kernel.org" , "syzkaller-bugs\@googlegroups.com" , "tglx\@linutronix.de" , "xiyou.wangcong\@gmail.com" Subject: Re: =?utf-8?B?5Zue5aSNOg==?= INFO: rcu detected stall in tc_modify_qdisc In-Reply-To: References: <0000000000006f179d05ab8e2cf2@google.com> Date: Wed, 29 Jul 2020 12:13:25 -0700 Message-ID: <87tuxqxhgq.fsf@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi, "Zhang, Qiang" writes: > ________________________________________ > 发件人: linux-kernel-owner@vger.kernel.org 代表 syzbot > 发送时间: 2020年7月29日 13:53 > 收件人: davem@davemloft.net; fweisbec@gmail.com; jhs@mojatatu.com; jiri@resnulli.us; linux-kernel@vger.kernel.org; mingo@kernel.org; netdev@vger.kernel.org; syzkaller-bugs@googlegroups.com; tglx@linutronix.de; vinicius.gomes@intel.com; xiyou.wangcong@gmail.com > 主题: INFO: rcu detected stall in tc_modify_qdisc > > Hello, > > syzbot found the following issue on: > > HEAD commit: 181964e6 fix a braino in cmsghdr_from_user_compat_to_kern() > git tree: net > console output: https://syzkaller.appspot.com/x/log.txt?x=12925e38900000 > kernel config: https://syzkaller.appspot.com/x/.config?x=f87a5e4232fdb267 > dashboard link: https://syzkaller.appspot.com/bug?extid=9f78d5c664a8c33f4cce > compiler: gcc (GCC) 10.1.0-syz 20200507 > syz repro: > https://syzkaller.appspot.com/x/repro.syz?x=16587f8c900000 It seems that syzkaller is generating an schedule with too small intervals (3ns in this case) which causes a hrtimer busy-loop which starves other kernel threads. We could put some limits on the interval when running in software mode, but I don't like this too much, because we are talking about users with CAP_NET_ADMIN and they have easier ways to do bad things to the system. Cheers, -- Vinicius