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=-10.3 required=3.0 tests=BAYES_00, 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 D3115C433B4 for ; Tue, 6 Apr 2021 12:32:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9987D6135D for ; Tue, 6 Apr 2021 12:32:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344028AbhDFMcm (ORCPT ); Tue, 6 Apr 2021 08:32:42 -0400 Received: from mx2.suse.de ([195.135.220.15]:48300 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238115AbhDFMcm (ORCPT ); Tue, 6 Apr 2021 08:32:42 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4BD67B178; Tue, 6 Apr 2021 12:32:33 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 07D541F2B77; Tue, 6 Apr 2021 14:32:33 +0200 (CEST) Date: Tue, 6 Apr 2021 14:32:33 +0200 From: Jan Kara To: Hao Sun Cc: tytso@mit.edu, jack@suse.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: KCSAN: data-race in __jbd2_journal_file_buffer / jbd2_journal_dirty_metadata Message-ID: <20210406123232.GD19407@quack2.suse.cz> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org Hello! On Sun 04-04-21 17:40:44, Hao Sun wrote: > When using Healer(https://github.com/SunHao-0/healer/tree/dev) to fuzz > the Linux kernel, I found a data-race vulnerability in > __jbd2_journal_file_buffer / jbd2_journal_dirty_metadata. > Sorry, data-race is usually difficult to reproduce. I cannot provide > you with a reproducing program. > I hope that the call stack information in the crash log can help you > locate the problem. > Kernel config and full log can be found in the attachment. > > Here is the detailed information: > commit: 3b9cdafb5358eb9f3790de2f728f765fef100731 > version: linux 5.11 > git tree: upstream > report: > ================================================================== > BUG: KCSAN: data-race in __jbd2_journal_file_buffer / > jbd2_journal_dirty_metadata > write to 0xffff88800af6da38 of 8 bytes by task 4822 on cpu 1: > __jbd2_journal_file_buffer+0x18d/0x370 linux/fs/jbd2/transaction.c:2518 > __jbd2_journal_refile_buffer+0x155/0x230 linux/fs/jbd2/transaction.c:2612 > jbd2_journal_commit_transaction+0x24c6/0x3200 linux/fs/jbd2/commit.c:1084 > kjournald2+0x253/0x470 linux/fs/jbd2/journal.c:213 > kthread+0x1f0/0x220 linux/kernel/kthread.c:292 > ret_from_fork+0x1f/0x30 linux/arch/x86/entry/entry_64.S:294 Thanks for report but I'm not sure what KCSAN is complaining about - isn't the report truncated? I'm missing 'read' part of the report... The complaint is on line: jh->b_transaction = transaction; I would guess the complaint is because of the check: /* * This and the following assertions are unreliable since we may see jh * in inconsistent state unless we grab bh_state lock. But this is * crucial to catch bugs so let's do a reliable check until the * lockless handling is fully proven. */ if (jh->b_transaction != transaction && jh->b_next_transaction != transaction) { And the comment explains, why we do this unreliable check. Again, if we wanted to silence KCSAN, we could use data_race() macro but AFAIU Ted isn't very fond of that annotation. Honza -- Jan Kara SUSE Labs, CR