From mboxrd@z Thu Jan 1 00:00:00 1970 From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman) Subject: Re: [PATCH] userns: Support fuse interacting with multiple user namespaces Date: Mon, 12 Nov 2012 18:37:33 -0800 Message-ID: <878va6i5xu.fsf@xmission.com> References: <87objjcfp4.fsf@xmission.com> <87625brr76.fsf@tucsk.pomaz.szeredi.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87625brr76.fsf-d8RdFUjzFsbxNFs70CDYszOMxtEWgIxa@public.gmane.org> (Miklos Szeredi's message of "Mon, 12 Nov 2012 12:33:33 +0100") List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Miklos Szeredi Cc: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux Containers , linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: containers.vger.kernel.org Miklos Szeredi writes: > ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman) writes: > >> Use kuid_t and kgid_t in struct fuse_conn and struct fuse_mount_data. >> >> The connection between between a fuse filesystem and a fuse daemon is >> established when a fuse filesystem is mounted and provided with a file >> descriptor the fuse daemon created by opening /dev/fuse. >> >> For now restrict the communication of uids and gids between the fuse >> filesystem and the fuse daemon to the initial user namespace. > > Why? > > I think far more logical would be to limit a single instance of the > filesystem and the daemon to an arbitrary but *single* namespace. > I.e. one fuse_conn <-> one user namespace. > > Is there a reason to treat the initial namespace specially? Stepwise making this work. The initial user namespace is special in that is the only user namespace you can currently mount a filesystem in. My goal with the posted patch is to support users on the other side of the vfs that are in multiple user namespaces. Which basically means accepting kuid_t and kgid_t values and converting them to uid_t and gid_t values where needed. As for creating a version of fuse that can be mounted in different user namespaces and can communicate with the fuse daemon in the user namespace the filesystem was mounted in, I have a preliminary patch for that. My goal with that patch is to support unprivileged mounts of fuse without the help of a suid root mount program. But that patch is more involved and not quite ready yet. I want to get to the point that I can enable fuse and user namespaces at the same time (what this patch allows) and then put in the effort to fully take advantage of user namespaces. Eric