From mboxrd@z Thu Jan 1 00:00:00 1970 From: Seth Forshee Subject: Re: [PATCH v4 2/5] fuse: Support fuse filesystems outside of init_user_ns Date: Wed, 15 Oct 2014 17:05:12 +0200 Message-ID: <20141015150512.GA22951@ubuntu-mba51> References: <1413296756-25071-1-git-send-email-seth.forshee@canonical.com> <1413296756-25071-3-git-send-email-seth.forshee@canonical.com> <543E8983.5090001@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Miklos Szeredi , fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, "Eric W. Biederman" , "Serge H. Hallyn" To: Andy Lutomirski Return-path: Received: from mail-la0-f51.google.com ([209.85.215.51]:46901 "EHLO mail-la0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751418AbaJOPFX (ORCPT ); Wed, 15 Oct 2014 11:05:23 -0400 Received: by mail-la0-f51.google.com with SMTP id ge10so1220403lab.38 for ; Wed, 15 Oct 2014 08:05:21 -0700 (PDT) Content-Disposition: inline In-Reply-To: <543E8983.5090001@mit.edu> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, Oct 15, 2014 at 07:49:39AM -0700, Andy Lutomirski wrote: > On 10/14/2014 07:25 AM, Seth Forshee wrote: > > Update fuse to translate uids and gids to/from the user namspace > > of the process servicing requests on /dev/fuse. Any ids which do > > not map into the namespace will result in errors. inodes will > > also be marked bad when unmappable ids are received from > > userspace. > > > > Due to security concerns the namespace used should be fixed, > > otherwise a user might be able to gain elevated privileges or > > influence processes that the user would otherwise be unable to > > manipulate. Thus the namespace of the mounting process is used > > for all translations, and this namespace is required to be the > > same as the one in use when /dev/fuse was opened. > > > > I'm not sure that this is necessary if my nosuid patch goes in, but I > also don't think it makes any sense to hold this up while we find a > perfect solution. > > Is there a decent way to extend this to different translation schemes in > the future (e.g. a flag at fs setup that could be used)? I think it would be possible to relax the translation scheme restrictions in the future, certainly that's easier than tightening down a looser restriction. I still favor picking one namespace to use for translation (surely that's how it would work with other filesystems anyway) rather than using the current namespace during /dev/fuse I/O. I did an implementation using the latter technique, and it's far more complex with no benefits that I can see. Thanks, Seth