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=-13.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 D2C37C352AA for ; Mon, 7 Oct 2019 10:04:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A904D2084D for ; Mon, 7 Oct 2019 10:04:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="N6HzdJBt" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727537AbfJGKEa (ORCPT ); Mon, 7 Oct 2019 06:04:30 -0400 Received: from mail-oi1-f193.google.com ([209.85.167.193]:45923 "EHLO mail-oi1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727262AbfJGKE3 (ORCPT ); Mon, 7 Oct 2019 06:04:29 -0400 Received: by mail-oi1-f193.google.com with SMTP id o205so11093213oib.12 for ; Mon, 07 Oct 2019 03:04:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=gYT1x2/n140JP+1FiTJ0CmclfsvjrAD1h2tPOsxcDtk=; b=N6HzdJBtIpQoxnOBdY0HnLqWIl4ZGqrWy52I2zIQx6jUsIW0YliTbMjw3kdcQDsmQF WDmsktR5U8xqyStXSgOAjksxTeVxGWSEqOH7Gf8wad2mvgc2NEXwJyF4sRnMPsKCrVX+ JlFN2i4zOZK1TOsyVruHJNguL4GzRFAGoB8NJSfZZOZlDZ2YuqmvQxz2b8t7q+/bJNz+ W80qUvbBpdwcSyvj25sSkenbt7sn2nLonZFaU/QifQ51fPKU3DlrSzXNMii5YY/zsHde JXu4Ipbl36u5D5dN7SQqN7nLl7Fgy41BpH9t0uNNilMtYGmn5u6YtV4p/zLb3OdNEI3D GFFQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=gYT1x2/n140JP+1FiTJ0CmclfsvjrAD1h2tPOsxcDtk=; b=bcW5c6q1EMtlub0ep4+I5Fq1AHuvnyZie6w+ZBrAfUB4S3v1TrkWVsIP9VXa7s3n7o WfnoBSSFHRojuSXOFuNiol8KYaNF4NYNuPYhx/LndKXwie6SykqPTPgyNn95kIdlvmEv RpgWFp5oYtwS3ZbDpG4weOmRhVh3PH8babanXPZpRp+/FFfNdZNQirREGSDDI5uDXTdC dzUjf7y4holzOcDt7f2rNElpKD2oVCq3RW973NgO88iHSB4WaFfpT3aRCo3gJQZPurOQ dlgWF+g2+Xw8m7oxxa93lITatnPOrMaGPTyR1PcXlT//a8PGwbM2toMk+xcEK11ci74U 0vDA== X-Gm-Message-State: APjAAAUMFuc9mn28GsP2ZHh3ruoCa4qKsewWC8NIR/ReOp03wDYta963 SefH4ZVJxqWj+pT3LrqWF7nyHnvvx+E+dnHPynEwMQ== X-Google-Smtp-Source: APXvYqwq5iX3haMgW2pDDYlUcZQMS6VSvjATAwVAdUQyT2N2RAgpJ9Jgfm6V7j6yYCXNmqZhgSgI0P2elMaMnbZ3S04= X-Received: by 2002:a05:6808:13:: with SMTP id u19mr566370oic.83.1570442667301; Mon, 07 Oct 2019 03:04:27 -0700 (PDT) MIME-Version: 1.0 References: <000000000000604e8905944f211f@google.com> In-Reply-To: <000000000000604e8905944f211f@google.com> From: Marco Elver Date: Mon, 7 Oct 2019 12:04:16 +0200 Message-ID: Subject: Re: KCSAN: data-race in find_next_bit / rcu_report_exp_cpu_mult To: syzbot , paulmck@kernel.org, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, Joel Fernandes , rcu@vger.kernel.org Cc: 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 Content-Type: text/plain; charset="UTF-8" Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org +RCU maintainers This might be a data-race in RCU itself. 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.