From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753498AbXDUQ7c (ORCPT ); Sat, 21 Apr 2007 12:59:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753396AbXDUQ7c (ORCPT ); Sat, 21 Apr 2007 12:59:32 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:35640 "EHLO ebiederm.dsl.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753388AbXDUQ7b (ORCPT ); Sat, 21 Apr 2007 12:59:31 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Jan Engelhardt Cc: Andrew Morton , Miklos Szeredi , serue@us.ibm.com, viro@ftp.linux.org.uk, linuxram@us.ibm.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, containers@lists.osdl.org Subject: Re: [patch 7/8] allow unprivileged mounts References: <20070420102532.385211890@szeredi.hu> <20070420102652.075606533@szeredi.hu> <20070421005513.e230aa88.akpm@linux-foundation.org> Date: Sat, 21 Apr 2007 10:57:10 -0600 In-Reply-To: (Jan Engelhardt's message of "Sat, 21 Apr 2007 17:43:28 +0200 (MEST)") Message-ID: User-Agent: Gnus/5.110006 (No Gnus v0.6) Emacs/21.4 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jan Engelhardt writes: > On Apr 21 2007 08:10, Eric W. Biederman wrote: >>> >>>> Define a new fs flag FS_SAFE, which denotes, that unprivileged >>>> mounting of this filesystem may not constitute a security problem. >>>> >>>> Since most filesystems haven't been designed with unprivileged >>>> mounting in mind, a thorough audit is needed before setting this flag. >>> >>> Practically speaking, is there any realistic likelihood that any filesystem >>> apart from FUSE will ever use this? >> >>Also potentially some of the kernel virtual filesystems. /proc should >>be safe already. If you don't have any kind of backing store this problem >>gets easier. > > tmpfs! tmpfs is a possible problem because it can consume lots of ram/swap. Which is why it has limits on the amount of space it can consume. Those are set as mount options as I recall. Which means that we would need to do something different with respect to limits before tmpfs could become safe for an untrusted user to mount. Still it's close. Eric