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=-8.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_PASS,UNPARSEABLE_RELAY,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 211F8C43143 for ; Mon, 1 Oct 2018 08:56:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B23F120652 for ; Mon, 1 Oct 2018 08:56:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="jrskyZvG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B23F120652 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-btrfs-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729059AbeJAPdO (ORCPT ); Mon, 1 Oct 2018 11:33:14 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:44120 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728808AbeJAPdO (ORCPT ); Mon, 1 Oct 2018 11:33:14 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w918s3Rc128613 for ; Mon, 1 Oct 2018 08:56:31 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : subject : date : message-id; s=corp-2018-07-02; bh=P4uRh/6s4Y2ZXi7LrGKTTQPJfu+gp3dGXbDChpRxKZI=; b=jrskyZvGFnEHkzJ0b65LmPZXoObVhx0vKtpZRjL1o2k5E+wTBqKDWdqadcFEo8DNbmia FPg18QI14DtIetLmnGwqh/yuJH25ydxgyx4eghShhq9IC068qtLt5yJfrqYK+mDlRx6b OYbYMh3uIB+1HLsSBPXWzWLW6fcLrpQ32hiWYHAjejCElTiDlWu3eMPQ0OvTzdwiXtUS 0CzLf3+osFws+v3u5u1l+ydVoVxAh3Z1Zv2l3NM6Waex1aUNw+e0xwnRJo5EiMnFF8ii hL59+8i53X+aPzHcEfuWqsIEBWpfo7v/P1wpvyFIbi0k56ehy5TnUxagb8arO6evxsxT /A== Received: from aserv0022.oracle.com (aserv0022.oracle.com [141.146.126.234]) by aserp2120.oracle.com with ESMTP id 2mt1bpnpfg-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Mon, 01 Oct 2018 08:56:31 +0000 Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w918uVWP019000 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK) for ; Mon, 1 Oct 2018 08:56:31 GMT Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id w918uUmk019048 for ; Mon, 1 Oct 2018 08:56:30 GMT Received: from tpasj.sg.oracle.com (/10.186.53.176) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 01 Oct 2018 01:56:30 -0700 From: Anand Jain To: linux-btrfs@vger.kernel.org Subject: [PATCH RFC] btrfs: harden agaist duplicate fsid Date: Mon, 1 Oct 2018 16:56:04 +0800 Message-Id: <1538384164-3030-1-git-send-email-anand.jain@oracle.com> X-Mailer: git-send-email 1.8.3.1 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9032 signatures=668707 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=1 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1810010091 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org Its not that impossible to imagine that a device OR a btrfs image is been copied just by using the dd or the cp command. Which in case both the copies of the btrfs will have the same fsid. If on the system with automount enabled, the copied FS gets scanned. We have a known bug in btrfs, that we let the device path be changed after the device has been mounted. So using this loop hole the new copied device would appears as if its mounted immediately after its been copied. For example: Initially.. /dev/mmcblk0p4 is mounted as / lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT mmcblk0 179:0 0 29.2G 0 disk |-mmcblk0p4 179:4 0 4G 0 part / |-mmcblk0p2 179:2 0 500M 0 part /boot |-mmcblk0p3 179:3 0 256M 0 part [SWAP] `-mmcblk0p1 179:1 0 256M 0 part /boot/efi btrfs fi show Label: none uuid: 07892354-ddaa-4443-90ea-f76a06accaba Total devices 1 FS bytes used 1.40GiB devid 1 size 4.00GiB used 3.00GiB path /dev/mmcblk0p4 Copy mmcblk0 to sda dd if=/dev/mmcblk0 of=/dev/sda And immediately after the copy completes the change in the device superblock is notified which the automount scans using btrfs device scan and the new device sda becomes the mounted root device. lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 1 14.9G 0 disk |-sda4 8:4 1 4G 0 part / |-sda2 8:2 1 500M 0 part |-sda3 8:3 1 256M 0 part `-sda1 8:1 1 256M 0 part mmcblk0 179:0 0 29.2G 0 disk |-mmcblk0p4 179:4 0 4G 0 part |-mmcblk0p2 179:2 0 500M 0 part /boot |-mmcblk0p3 179:3 0 256M 0 part [SWAP] `-mmcblk0p1 179:1 0 256M 0 part /boot/efi btrfs fi show / Label: none uuid: 07892354-ddaa-4443-90ea-f76a06accaba Total devices 1 FS bytes used 1.40GiB devid 1 size 4.00GiB used 3.00GiB path /dev/sda4 The bug is quite nasty that you can't either unmount /dev/sda4 or /dev/mmcblk0p4. And the problem does not get solved until you take sda out of the system on to another system to change its fsid using the 'btrfstune -u' command. Signed-off-by: Anand Jain --- Hi, There was previous attempt to fix this bug ref: www.spinics.net/lists/linux-btrfs/msg37466.html which broke the Ubuntu subvol mount at boot. The reason for that is, Ubuntu changes the device path in the boot process, and the earlier fix checked for the device-path instead of block_device as in here and so we failed the subvol mount request and thus the bootup process. I have tested this with Oracle Linux with btrfs as boot device with a subvol to be mounted at boot. And also have verified with new test case btrfs/173. It will be good if someone run this through Ubuntu boot test case. fs/btrfs/volumes.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index f4405e430da6..62173a3abcc4 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -850,6 +850,29 @@ static noinline struct btrfs_device *device_list_add(const char *path, return ERR_PTR(-EEXIST); } + /* + * we are going to replace the device path, make sure its the + * same device if the device mounted + */ + if (device->bdev) { + struct block_device *path_bdev; + + path_bdev = lookup_bdev(path); + if (IS_ERR(path_bdev)) { + mutex_unlock(&fs_devices->device_list_mutex); + return ERR_CAST(path_bdev); + } + + if (device->bdev != path_bdev) { + bdput(path_bdev); + mutex_unlock(&fs_devices->device_list_mutex); + return ERR_PTR(-EEXIST); + } + bdput(path_bdev); + pr_info("BTRFS: device fsid:devid %pU:%llu old path:%s new path:%s\n", + disk_super->fsid, devid, rcu_str_deref(device->name), path); + } + name = rcu_string_strdup(path, GFP_NOFS); if (!name) { mutex_unlock(&fs_devices->device_list_mutex); -- 1.8.3.1