linux-kernel - Re: [RFC 1/5] user namespaces: Add a user_namespace as creator/owner of uts

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Message-ID: <20101217161200.GA5548@peq>
Date:	Fri, 17 Dec 2010 10:12:00 -0600
From:	Serge Hallyn <serge.hallyn@...onical.com>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	"Serge E. Hallyn" <serge@...lyn.com>,
	LSM <linux-security-module@...r.kernel.org>,
	James Morris <jmorris@...ei.org>,
	Kees Cook <kees.cook@...onical.com>,
	containers@...ts.linux-foundation.org,
	kernel list <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Michael Kerrisk <michael.kerrisk@...il.com>
Subject: Re: [RFC 1/5] user namespaces: Add a user_namespace as
 creator/owner of uts_namespace

Quoting Alexey Dobriyan (adobriyan@...il.com):
> On Fri, Dec 17, 2010 at 5:24 PM, Serge E. Hallyn <serge@...lyn.com> wrote:
> > +/*
> > + * userns count is 1 for root user, 1 for init_uts_ns,
> > + * and 1 for... ?
> > + */
> >  struct user_namespace init_user_ns = {
> >        .kref = {
> > -               .refcount       = ATOMIC_INIT(2),
> > +               .refcount       = ATOMIC_INIT(3),
> 
> +1 is for init_nsproxy ;-)

Hmm, actually user_namespace isn't in struct nsproxy any more,
since 18b6e0414e42d95183f07d8177e3ff0241abd825.

I think my original thought was that init_user_ns is pinned twice by
root_user - once as creator and once as the root user in it.  In
which case it isn't right - the user_ns pins the task which created
it, the creator does not pin the user_ns it creates.

-serge
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