Return-Path: <linux-kernel-owner+w=401wt.eu-S1758098AbXH3JGu@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1758098AbXH3JGu (ORCPT <rfc822;w@1wt.eu>);
	Thu, 30 Aug 2007 05:06:50 -0400
Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756034AbXH3JGk
	(ORCPT <rfc822;linux-kernel-outgoing>);
	Thu, 30 Aug 2007 05:06:40 -0400
Received: from styx.suse.cz ([82.119.242.94]:46096 "EHLO duck.suse.cz"
	rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP
	id S1755795AbXH3JGj (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Thu, 30 Aug 2007 05:06:39 -0400
Date: Thu, 30 Aug 2007 11:25:48 +0200
From: Jan Kara <jack@suse.cz>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org,
       Balbir Singh <balbir@in.ibm.com>, "Serge E. Hallyn" <serue@us.ibm.com>,
       containers@lists.osdl.org
Subject: Re: [PATCH] Send quota messages via netlink
Message-ID: <20070830092548.GB16336@duck.suse.cz>
References: <20070828141318.GC5869@duck.suse.cz> <20070828211335.37fce4c9.akpm@linux-foundation.org> <20070829122647.GB7814@duck.suse.cz> <m1mywa42g7.fsf@ebiederm.dsl.xmission.com> <20070829192653.GD7814@duck.suse.cz> <m1wsve2gpo.fsf@ebiederm.dsl.xmission.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <m1wsve2gpo.fsf@ebiederm.dsl.xmission.com>
User-Agent: Mutt/1.5.13 (2006-08-11)
Sender: linux-kernel-owner@vger.kernel.org
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 2491
Lines: 50

On Wed 29-08-07 15:06:43, Eric W. Biederman wrote:
> Jan Kara <jack@suse.cz> writes:
> >> However I'm still confused about the use of current->user.  If that
> >> is what we really want and not the user who's quota will be charged
> >> it gets to be a really trick business, because potentially the uid
> >> we want to deliver varies depending on who opened the netlink socket.
> >   I see it's a complicated matter :). What I need to somehow pass to
> > userspace is something (and I don't really care whether it will be number,
> > string or whatever) that userspace can read and e.g. find a terminal
> > window or desktop the affected user has open and also translate the
> > identity to some user-understandable name (average user Joe has to
> > understand that he should quickly cleanup his home directory ;).
> >   Thinking more about it, we could probably pass a string to userspace in
> > the format:
> >   <namespace type>:<user identification>
> >
> > So for example we can have something like:
> >   unix:1000 (traditional unix UIDs)
> >   nfs4:joe@machine
> >
> > The problem is: Are we able to find out in which "namespace type" we are
> > and send enough identifying information from a context of unpriviledged
> > user?
> 
> Ok.  This provides enough context to understand what you are trying to do.
> You do want the unix user id, not the filesystem notion.  Because you
> are looking for the user.
> 
> So we have to figure out how to do the hard thing which is look at
> who opened our netlink broadcast see if they are in the same user
> namespace as current->user.  Which is a pain and we don't currently
> have the infrastructure for.
  There can be arbitrary number of listeners (potentially from different
namespaces if I understand it correctly) listening to broadcasts. So I
think we should pass some universal identifier rather than try to find out
who is listening etc. I think such identifiers would be useful for other
things too, won't they?
  BTW: Do you have some idea, when would be the infrastructure clearer?
Whether it makes sence to currently proceed with UIDs and later change it
to something generic or whether I should wait before you sort it out :).

								Honza
-- 
Jan Kara <jack@suse.cz>
SuSE CR Labs
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/