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=-9.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY,URIBL_BLOCKED, USER_AGENT_GIT 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 0A947C10F00 for ; Mon, 18 Mar 2019 12:19:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CF18320857 for ; Mon, 18 Mar 2019 12:19:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="DeG4vLfK" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727169AbfCRMTj (ORCPT ); Mon, 18 Mar 2019 08:19:39 -0400 Received: from userp2130.oracle.com ([156.151.31.86]:35878 "EHLO userp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726435AbfCRMTi (ORCPT ); Mon, 18 Mar 2019 08:19:38 -0400 Received: from pps.filterd (userp2130.oracle.com [127.0.0.1]) by userp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x2ICJFUB122337; Mon, 18 Mar 2019 12:19:30 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id; s=corp-2018-07-02; bh=3rpCUiaSB+U6fopAwDgIrcqIuKktISQzb4oCWRgSzu8=; b=DeG4vLfK1egQ9yGxfCLyHFdvXs0xULT5n+ROiVauM3TaVculSaYo6f/bnePmzIw1ZvRh k0LMaiCJNJKCUqxFFM6YwUdus01PLkV3bw5z5Xk9ahg2M+cxq+evAZ6p3GAppjpJNMV6 fD9vVQUpuuB0CjzKB3gzNVEKZnrLYZJg5E/6BRzChIaSVRnRyYJAPqK+5vPc3EsygwaK 8F7onUNw5OpU4XVLgIs4ZiAZBSBGG6IB6wshryBquCPsyOAGi0nFIzfEMsc3gdLrJqLX BT/+FMt0RWe07qEs75HYmYr199kZDpwGq+VF1oI/TRcD65qSnrq0DZERrjVbCcGC1tJ/ Jg== Received: from userv0021.oracle.com (userv0021.oracle.com [156.151.31.71]) by userp2130.oracle.com with ESMTP id 2r8rjue4yn-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 18 Mar 2019 12:19:30 +0000 Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by userv0021.oracle.com (8.14.4/8.14.4) with ESMTP id x2ICJO1J000436 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Mon, 18 Mar 2019 12:19:24 GMT Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x2ICJNl7030671; Mon, 18 Mar 2019 12:19:23 GMT Received: from linux.cn.oracle.com (/10.182.69.106) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 18 Mar 2019 05:19:23 -0700 From: Dongli Zhang To: axboe@kernel.dk, linux-block@vger.kernel.org Cc: linux-kernel@vger.kernel.org, jack@suse.cz, penguin-kernel@i-love.sakura.ne.jp Subject: [PATCH 1/1] loop: access lo_backing_file only when the loop device is Lo_bound Date: Mon, 18 Mar 2019 20:23:17 +0800 Message-Id: <1552911797-20455-1-git-send-email-dongli.zhang@oracle.com> X-Mailer: git-send-email 2.7.4 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9198 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903180093 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit 758a58d0bc67 ("loop: set GENHD_FL_NO_PART_SCAN after blkdev_reread_part()") separates "lo->lo_backing_file = NULL" and "lo->lo_state = Lo_unbound" into different critical regions protected by loop_ctl_mutex. However, there is below race that the NULL lo->lo_backing_file would be accessed when the backend of a loop is another loop device, e.g., loop0's backend is a file, while loop1's backend is loop0. loop0's backend is file loop1's backend is loop0 __loop_clr_fd() mutex_lock(&loop_ctl_mutex); lo->lo_backing_file = NULL; --> set to NULL mutex_unlock(&loop_ctl_mutex); loop_set_fd() mutex_lock_killable(&loop_ctl_mutex); loop_validate_file() f = l->lo_backing_file; --> NULL access if loop0 is not Lo_unbound mutex_lock(&loop_ctl_mutex); lo->lo_state = Lo_unbound; mutex_unlock(&loop_ctl_mutex); lo->lo_backing_file should be accessed only when the loop device is Lo_bound. In fact, the problem has been introduced already in commit 7ccd0791d985 ("loop: Push loop_ctl_mutex down into loop_clr_fd()") after which loop_validate_file() could see devices in Lo_rundown state with which it did not count. It was harmless at that point but still. Fixes: 7ccd0791d985 ("loop: Push loop_ctl_mutex down into loop_clr_fd()") Reported-by: syzbot+9bdc1adc1c55e7fe765b@syzkaller.appspotmail.com Signed-off-by: Dongli Zhang Reviewed-by: Jan Kara --- drivers/block/loop.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 1e6edd5..bf1c61c 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -656,7 +656,7 @@ static int loop_validate_file(struct file *file, struct block_device *bdev) return -EBADF; l = f->f_mapping->host->i_bdev->bd_disk->private_data; - if (l->lo_state == Lo_unbound) { + if (l->lo_state != Lo_bound) { return -EINVAL; } f = l->lo_backing_file; -- 2.7.4