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,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 4686CC432C0 for ; Tue, 19 Nov 2019 03:54:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 191122230F for ; Tue, 19 Nov 2019 03:54:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574135653; bh=gVaoEfdiE6QGBVJzfbL1Mk1XcPXpP9BXLfVw/JsCMCQ=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=Lo6HmcgEB+s3SiZ4sGYY5hYilWHxuU0+zFD3THqPhb2Zk5XvvBhRDO1N77KBC044F JBHWQg/wqr38IZEJIM1DgR+e0/ejEyvzVddbmGA16vaPJWvCx/Af4oqhnOB61oLmAs OWHk1TGLqem6hhXt1sEky4s5TWvOcMxhVmhqdy10= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727112AbfKSDyM (ORCPT ); Mon, 18 Nov 2019 22:54:12 -0500 Received: from mail.kernel.org ([198.145.29.99]:51646 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727363AbfKSDyM (ORCPT ); Mon, 18 Nov 2019 22:54:12 -0500 Received: from paulmck-ThinkPad-P72.home (199-192-87-166.static.wiline.com [199.192.87.166]) (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 22306222DD; Tue, 19 Nov 2019 03:54:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574135651; bh=gVaoEfdiE6QGBVJzfbL1Mk1XcPXpP9BXLfVw/JsCMCQ=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=DkiMhRza8LV0gcVFrffeiUMy2HPFDAdV4VBn6Wgd1M1VQoGTDQghdmLngOD2oMw7a H7Vuu8OeOZB6T0CBMnVlcewDLC2T+tZeJ+sqFWhlhewIxok5FlMVbgLpGJeSCTpUdj 2bU5aC4TUUwNbqsVnjYO7m9wOBAS8BTdanBvDL1M= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id B91CC35227AF; Mon, 18 Nov 2019 19:54:10 -0800 (PST) Date: Mon, 18 Nov 2019 19:54:10 -0800 From: "Paul E. McKenney" To: Eric Biggers Cc: Marco Elver , syzbot , Lai Jiangshan , Josh Triplett , axboe@kernel.dk, justin@coraid.com, linux-block@vger.kernel.org, LKML , syzkaller-bugs@googlegroups.com Subject: Re: KCSAN: data-race in process_srcu / synchronize_srcu Message-ID: <20191119035410.GR2889@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <000000000000b587670596839fab@google.com> <20191104161152.GB20975@paulmck-ThinkPad-P72> <20191104165303.GG20975@paulmck-ThinkPad-P72> <20191119024805.GF3147@sol.localdomain> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191119024805.GF3147@sol.localdomain> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Nov 18, 2019 at 06:48:05PM -0800, Eric Biggers wrote: > On Mon, Nov 04, 2019 at 08:53:03AM -0800, Paul E. McKenney wrote: > > On Mon, Nov 04, 2019 at 05:14:50PM +0100, Marco Elver wrote: > > > On Mon, 4 Nov 2019 at 17:11, Paul E. McKenney wrote: > > > > > > > > On Mon, Nov 04, 2019 at 12:31:56PM +0100, Marco Elver wrote: > > > > > +RCU folks, since this is probably a data race in RCU. > > > > > > > > > > On Mon, 4 Nov 2019 at 12:29, syzbot > > > > > wrote: > > > > > > > > > > > > Hello, > > > > > > > > > > > > syzbot found the following crash on: > > > > > > > > > > > > HEAD commit: 05f22368 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=17ade7ef600000 > > > > > > kernel config: https://syzkaller.appspot.com/x/.config?x=87d111955f40591f > > > > > > dashboard link: https://syzkaller.appspot.com/bug?extid=08f3e9d26e5541e1ecf2 > > > > > > 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+08f3e9d26e5541e1ecf2@syzkaller.appspotmail.com > > > > > > > > > > > > ================================================================== > > > > > > BUG: KCSAN: data-race in process_srcu / synchronize_srcu > > > > > > > > > > > > write to 0xffffffff8604e8a0 of 8 bytes by task 17 on cpu 1: > > > > > > srcu_gp_end kernel/rcu/srcutree.c:533 [inline] > > > > > > srcu_advance_state kernel/rcu/srcutree.c:1146 [inline] > > > > > > process_srcu+0x207/0x780 kernel/rcu/srcutree.c:1237 > > > > > > 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 0xffffffff8604e8a0 of 8 bytes by task 12515 on cpu 0: > > > > > > srcu_might_be_idle kernel/rcu/srcutree.c:784 [inline] > > > > > > synchronize_srcu+0x107/0x214 kernel/rcu/srcutree.c:996 > > > > > > fsnotify_connector_destroy_workfn+0x63/0xb0 fs/notify/mark.c:164 > > > > > > 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: 0 PID: 12515 Comm: kworker/u4:8 Not tainted 5.4.0-rc3+ #0 > > > > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > > > > > Google 01/01/2011 > > > > > > Workqueue: events_unbound fsnotify_connector_destroy_workfn > > > > > > ================================================================== > > > > > > Kernel panic - not syncing: panic_on_warn set ... > > > > > > CPU: 0 PID: 12515 Comm: kworker/u4:8 Not tainted 5.4.0-rc3+ #0 > > > > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > > > > > Google 01/01/2011 > > > > > > Workqueue: events_unbound fsnotify_connector_destroy_workfn > > > > > > Call Trace: > > > > > > __dump_stack lib/dump_stack.c:77 [inline] > > > > > > dump_stack+0xf5/0x159 lib/dump_stack.c:113 > > > > > > panic+0x210/0x640 kernel/panic.c:221 > > > > > > kcsan_report.cold+0xc/0x10 kernel/kcsan/report.c:302 > > > > > > __kcsan_setup_watchpoint+0x32e/0x4a0 kernel/kcsan/core.c:411 > > > > > > __tsan_read8 kernel/kcsan/kcsan.c:36 [inline] > > > > > > __tsan_read8+0x2c/0x30 kernel/kcsan/kcsan.c:36 > > > > > > srcu_might_be_idle kernel/rcu/srcutree.c:784 [inline] > > > > > > synchronize_srcu+0x107/0x214 kernel/rcu/srcutree.c:996 > > > > > > fsnotify_connector_destroy_workfn+0x63/0xb0 fs/notify/mark.c:164 > > > > > > 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 > > > > > > Kernel Offset: disabled > > > > > > Rebooting in 86400 seconds.. > > > > > > > > > > > > > > > > > > --- > > > > > > 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. > > > > > > > > Good catch! Does the patch below help? > > > > > > Looks good to me, thanks for the quick fix. > > > > > > Acked-by: Marco Elver > > > > Applied, thank you! > > > > Thanx, Paul > > This patch is not in linux-next. What happened to it? It is in -rcu, but arrived too late to make my pull request for v5.5. It will hit -next shortly after v5.5-rc1. Thanx, Paul