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=-6.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT 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 E13ADC4360F for ; Mon, 1 Apr 2019 17:37:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B40BC20896 for ; Mon, 1 Apr 2019 17:37:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554140232; bh=KvJGOXNkqUeEJ+FNtt4bRCBcA3Y1p9KJvuQz1VXooGc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=osn/4sgyg4a8sPO9qYi6OYG4wCncoBvAT1aF3+Tx8VzLyWPScMeXFZ8EUHmXkYbe3 4cTMnYCn3e48GQJwZvMit74gatq5Lco9pQtMbUZ5nntLnX5a5AHiQ6eKRj9HttRKA1 CXY/OGkMYugfBjALv5zXlPEq5CTelktosp5c6H3M= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388143AbfDARhL (ORCPT ); Mon, 1 Apr 2019 13:37:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:49420 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388124AbfDARhJ (ORCPT ); Mon, 1 Apr 2019 13:37:09 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 C9D0420896; Mon, 1 Apr 2019 17:37:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1554140228; bh=KvJGOXNkqUeEJ+FNtt4bRCBcA3Y1p9KJvuQz1VXooGc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RmCO0q+niSTUOJXFAqMEdwBl0nzrmtzGMBrxdHAm34ilfpxY9shHah2QqY94dz4tB LC06oNJS9tbdtIM7OvQdgVFPXB84z+DsAQ2mPe5gSyhNW/g5lK37KCuPQyH27/M71H UgkPd+5vvYgTlqDZFh5/Sq8RYBBoHEuQdHbbQ9BQ= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Frank Sorenson , Lukas Czerner , Theodore Tso Subject: [PATCH 3.18 04/50] ext4: fix data corruption caused by unaligned direct AIO Date: Mon, 1 Apr 2019 19:02:47 +0200 Message-Id: <20190401170041.634242694@linuxfoundation.org> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20190401170041.257273804@linuxfoundation.org> References: <20190401170041.257273804@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lukas Czerner commit 372a03e01853f860560eade508794dd274e9b390 upstream. Ext4 needs to serialize unaligned direct AIO because the zeroing of partial blocks of two competing unaligned AIOs can result in data corruption. However it decides not to serialize if the potentially unaligned aio is past i_size with the rationale that no pending writes are possible past i_size. Unfortunately if the i_size is not block aligned and the second unaligned write lands past i_size, but still into the same block, it has the potential of corrupting the previous unaligned write to the same block. This is (very simplified) reproducer from Frank // 41472 = (10 * 4096) + 512 // 37376 = 41472 - 4096 ftruncate(fd, 41472); io_prep_pwrite(iocbs[0], fd, buf[0], 4096, 37376); io_prep_pwrite(iocbs[1], fd, buf[1], 4096, 41472); io_submit(io_ctx, 1, &iocbs[1]); io_submit(io_ctx, 1, &iocbs[2]); io_getevents(io_ctx, 2, 2, events, NULL); Without this patch the 512B range from 40960 up to the start of the second unaligned write (41472) is going to be zeroed overwriting the data written by the first write. This is a data corruption. 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 * 00009200 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 * 0000a000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 * 0000a200 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 With this patch the data corruption is avoided because we will recognize the unaligned_aio and wait for the unwritten extent conversion. 00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 * 00009200 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 * 0000a200 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 31 * 0000b200 Reported-by: Frank Sorenson Signed-off-by: Lukas Czerner Signed-off-by: Theodore Ts'o Fixes: e9e3bcecf44c ("ext4: serialize unaligned asynchronous DIO") Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- fs/ext4/file.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -79,7 +79,7 @@ ext4_unaligned_aio(struct inode *inode, struct super_block *sb = inode->i_sb; int blockmask = sb->s_blocksize - 1; - if (pos >= i_size_read(inode)) + if (pos >= ALIGN(i_size_read(inode), sb->s_blocksize)) return 0; if ((pos | iov_iter_alignment(from)) & blockmask)