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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 B1ED0C34031 for ; Thu, 20 Feb 2020 04:17:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 921302465D for ; Thu, 20 Feb 2020 04:17:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727952AbgBTERD (ORCPT ); Wed, 19 Feb 2020 23:17:03 -0500 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:33759 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727476AbgBTERD (ORCPT ); Wed, 19 Feb 2020 23:17:03 -0500 Received: from callcc.thunk.org (guestnat-104-133-8-109.corp.google.com [104.133.8.109] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 01K4Gp6k017152 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 19 Feb 2020 23:16:53 -0500 Received: by callcc.thunk.org (Postfix, from userid 15806) id 5101C4211EF; Wed, 19 Feb 2020 23:16:51 -0500 (EST) Date: Wed, 19 Feb 2020 23:16:51 -0500 From: "Theodore Y. Ts'o" To: Qian Cai Cc: adilger.kernel@dilger.ca, elver@google.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] ext4: fix a data race in EXT4_I(inode)->i_disksize Message-ID: <20200220041651.GA476845@mit.edu> References: <1581085751-31793-1-git-send-email-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1581085751-31793-1-git-send-email-cai@lca.pw> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 07, 2020 at 09:29:11AM -0500, Qian Cai wrote: > EXT4_I(inode)->i_disksize could be accessed concurrently as noticed by > KCSAN, > > BUG: KCSAN: data-race in ext4_write_end [ext4] / ext4_writepages [ext4] > > write to 0xffff91c6713b00f8 of 8 bytes by task 49268 on cpu 127: > ext4_write_end+0x4e3/0x750 [ext4] > ext4_update_i_disksize at fs/ext4/ext4.h:3032 > (inlined by) ext4_update_inode_size at fs/ext4/ext4.h:3046 > (inlined by) ext4_write_end at fs/ext4/inode.c:1287 > generic_perform_write+0x208/0x2a0 > ext4_buffered_write_iter+0x11f/0x210 [ext4] > ext4_file_write_iter+0xce/0x9e0 [ext4] > new_sync_write+0x29c/0x3b0 > __vfs_write+0x92/0xa0 > vfs_write+0x103/0x260 > ksys_write+0x9d/0x130 > __x64_sys_write+0x4c/0x60 > do_syscall_64+0x91/0xb47 > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > read to 0xffff91c6713b00f8 of 8 bytes by task 24872 on cpu 37: > ext4_writepages+0x10ac/0x1d00 [ext4] > mpage_map_and_submit_extent at fs/ext4/inode.c:2468 > (inlined by) ext4_writepages at fs/ext4/inode.c:2772 > do_writepages+0x5e/0x130 > __writeback_single_inode+0xeb/0xb20 > writeback_sb_inodes+0x429/0x900 > __writeback_inodes_wb+0xc4/0x150 > wb_writeback+0x4bd/0x870 > wb_workfn+0x6b4/0x960 > process_one_work+0x54c/0xbe0 > worker_thread+0x80/0x650 > kthread+0x1e0/0x200 > ret_from_fork+0x27/0x50 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 37 PID: 24872 Comm: kworker/u261:2 Tainted: G W O L 5.5.0-next-20200204+ #5 > Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 > Workqueue: writeback wb_workfn (flush-7:0) > > Since only the read is operating as lockless (outside of the > "i_data_sem"), load tearing could introduce a logic bug. Fix it by > adding READ_ONCE() for the read and WRITE_ONCE() for the write. > > Signed-off-by: Qian Cai Thanks, applied. - Ted