linux-kernel - Re: [PATCH 2/2] user namespaces: require cap_set{ug}id for CLONE

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Date:	Fri, 5 Dec 2008 10:45:52 -0600
From:	"Serge E. Hallyn" <serue@...ibm.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	James Morris <jmorris@...ei.org>
Subject: Re: [PATCH 2/2] user namespaces: require cap_set{ug}id for
	CLONE_NEWUSER

Quoting Eric W. Biederman (ebiederm@...ssion.com):
> "Serge E. Hallyn" <serue@...ibm.com> writes:
> 
> > While ideally CLONE_NEWUSER will eventually require no
> > privilege, the required permission checks are currently
> > not there.  As a result, CLONE_NEWUSER has the same effect
> > as a setuid(0)+setgroups(1,"0").  While we already require
> > CAP_SYS_ADMIN, requiring CAP_SETUID and CAP_SETGID seems
> > appropriate.
> 
> This looks reasonable.  For the short term we will need a greater
> set of caps to be able to do all of the interesting things.

Could you ack the patch?  Stephen explicitly doesn't want patches
in linux-next which haven't been acked, and security-next feeds
into linux-next, so I don't want to ask James to take the patch
without an ack :)

> Personally the user namespace only becomes interesting when we
> start to be able to move in the other direction and remove the
> set of capabilities requires to create it.
> 
> Eric

Agreed.  Now the thing is I don't think we need full userns
support to get there.  We just need the targeted capabilities
and the basic dummy fs support - that is, init_user_ns owns
all vfsmounts, and anyone not in init_user_ns only gets
user other access to files under those mounts.

Of course complete support for targeted caps will in itself
be a huge effort :)

So my roadmap is: next address the per-user keyring, then
the targeted caps.

-serge
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