From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031068AbXD2S7o (ORCPT ); Sun, 29 Apr 2007 14:59:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1031076AbXD2S7o (ORCPT ); Sun, 29 Apr 2007 14:59:44 -0400 Received: from moutng.kundenserver.de ([212.227.126.179]:52328 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031068AbXD2S7n (ORCPT ); Sun, 29 Apr 2007 14:59:43 -0400 Subject: unprivileged mount problems: device permissions ignored, mount sharing From: utz lehmann To: Miklos Szeredi , LKML Content-Type: text/plain Date: Sun, 29 Apr 2007 20:59:11 +0200 Message-Id: <1177873151.4343.29.camel@segv.aura.of.mankind> Mime-Version: 1.0 X-Mailer: Evolution 2.8.3 (2.8.3-2.fc6) Content-Transfer-Encoding: 7bit X-Provags-ID: V01U2FsdGVkX1/jGIKXNTNLT22L9lLVCLP8Im7uNpGmtfVhgyE 8jes4yvM30LXaRDgkMPdpqsOeAItcU3Jf0EWMWnxLLh6xTvNVc JSUGgMvow1EOSoQwylV87DaTTgIxIEk Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hello I tried the unprivileged mount v5 patches with 2.6.21.1. I made some experiments with normal filesystems (ext3, xfs, iso9660). I removed the FS_SAFE checks for that. Mounting and umounting as unprivileged user (user1) works, e.g. (/mnt/user1 is a mount owned by user1) [user1@segv ~]$ mmount -t xfs /dev/mapper/vg00-test /mnt/user1 But the device permissions are ignored. The unprivileged user can mount the block device even there are no permissions to access it: brw------- 1 root root 253, 5 Apr 29 18:32 /dev/mapper/vg00-test And there is another problem with sharing the device (superblock?). If user1 mount a device readonly: [user1@segv ~]$ mmount -r -t xfs /dev/mapper/vg00-test /mnt/user1 Than root cannot mount the device rw: [root@segv ~]# mount /dev/mapper/vg00-test /mnt/test/ mount: /dev/mapper/vg00-test already mounted or /mnt/test/ busy Mounting ro works and than remounting rw work. But than /mnt/user1 is rw too. This can DoS e.g. the automounter mounting /dev/mapper/vg00-test rw. utz