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=-7.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 3B6DAECE58C for ; Mon, 7 Oct 2019 13:22:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 114EB2173B for ; Mon, 7 Oct 2019 13:22:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570454548; bh=94FgQQQInriYcdaiwu3nO9LUTD1ig1lcCMAvKOjrqC4=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=MYKUZgXf/YamJixmyAWzJwwDWKnIcKqwjB0Fx++1e1qX6hOzC0h4H/TFYxbsBAsgq eyk/P88WNzi7jGC0eFVX7Fc71kz0jFYN4IFbgrtEtenwuVubZ3icCElm77jzY3o6yv WOoXNouLdI/hBrwIeq15xOVLQdWHxmd31p8GzVk8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727716AbfJGNWX (ORCPT ); Mon, 7 Oct 2019 09:22:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:60248 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727010AbfJGNWX (ORCPT ); Mon, 7 Oct 2019 09:22:23 -0400 Received: from paulmck-ThinkPad-P72 (unknown [12.12.162.101]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 821E820867; Mon, 7 Oct 2019 13:22:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570454541; bh=94FgQQQInriYcdaiwu3nO9LUTD1ig1lcCMAvKOjrqC4=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=Wu2tRRwWmif60CLvRIfmXIIdxFUVzY/DAMy3D3xiCP2QeY68YVmor0hUkkGfC6XNh HQ5HFPMwKqUTAOkE6hahJ8U/4Hip40f10Qx+/7iXubKwJtAux+CmTvfJi1CdRQvyIk OJTLt4gus3H0Mindd4qm+p3wqKrjbVvaKu+k86uM= Date: Mon, 7 Oct 2019 06:22:20 -0700 From: "Paul E. McKenney" To: Marco Elver Cc: syzbot , josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, Joel Fernandes , rcu@vger.kernel.org, a@unstable.cc, b.a.t.m.a.n@lists.open-mesh.org, davem@davemloft.net, LKML , mareklindner@neomailbox.ch, netdev@vger.kernel.org, sw@simonwunderlich.de, syzkaller-bugs@googlegroups.com Subject: Re: KCSAN: data-race in find_next_bit / rcu_report_exp_cpu_mult Message-ID: <20191007132220.GZ2689@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <000000000000604e8905944f211f@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Mon, Oct 07, 2019 at 12:04:16PM +0200, Marco Elver wrote: > +RCU maintainers > This might be a data-race in RCU itself. Quite possibly. I will take a look, but there will be delays due to this week being bootcamp and all. Thanx, Paul > On Mon, 7 Oct 2019 at 12:01, syzbot > wrote: > > > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: b4bd9343 x86, kcsan: Enable KCSAN for x86 > > git tree: https://github.com/google/ktsan.git kcsan > > console output: https://syzkaller.appspot.com/x/log.txt?x=11edb20d600000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=c0906aa620713d80 > > dashboard link: https://syzkaller.appspot.com/bug?extid=134336b86f728d6e55a0 > > compiler: gcc (GCC) 9.0.0 20181231 (experimental) > > > > Unfortunately, I don't have any reproducer for this crash yet. > > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+134336b86f728d6e55a0@syzkaller.appspotmail.com > > > > ================================================================== > > BUG: KCSAN: data-race in find_next_bit / rcu_report_exp_cpu_mult > > > > write to 0xffffffff85a7f140 of 8 bytes by task 7 on cpu 0: > > rcu_report_exp_cpu_mult+0x4f/0xa0 kernel/rcu/tree_exp.h:244 > > rcu_report_exp_rdp+0x6c/0x90 kernel/rcu/tree_exp.h:254 > > rcu_preempt_deferred_qs_irqrestore+0x3bb/0x580 kernel/rcu/tree_plugin.h:475 > > rcu_read_unlock_special+0xec/0x370 kernel/rcu/tree_plugin.h:659 > > __rcu_read_unlock+0xcf/0xe0 kernel/rcu/tree_plugin.h:394 > > rcu_read_unlock include/linux/rcupdate.h:645 [inline] > > batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:411 [inline] > > batadv_nc_worker+0x13a/0x390 net/batman-adv/network-coding.c:718 > > process_one_work+0x3d4/0x890 kernel/workqueue.c:2269 > > worker_thread+0xa0/0x800 kernel/workqueue.c:2415 > > kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352 > > > > read to 0xffffffff85a7f140 of 8 bytes by task 7251 on cpu 1: > > _find_next_bit lib/find_bit.c:39 [inline] > > find_next_bit+0x57/0xe0 lib/find_bit.c:70 > > sync_rcu_exp_select_node_cpus+0x28e/0x510 kernel/rcu/tree_exp.h:375 > > sync_rcu_exp_select_cpus+0x30c/0x590 kernel/rcu/tree_exp.h:439 > > rcu_exp_sel_wait_wake kernel/rcu/tree_exp.h:575 [inline] > > wait_rcu_exp_gp+0x25/0x40 kernel/rcu/tree_exp.h:589 > > process_one_work+0x3d4/0x890 kernel/workqueue.c:2269 > > worker_thread+0xa0/0x800 kernel/workqueue.c:2415 > > kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352 > > > > Reported by Kernel Concurrency Sanitizer on: > > CPU: 1 PID: 7251 Comm: kworker/1:4 Not tainted 5.3.0+ #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > Google 01/01/2011 > > Workqueue: rcu_gp wait_rcu_exp_gp > > ================================================================== > > > > > > --- > > This bug is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@googlegroups.com. > > > > syzbot will keep track of this bug report. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.