linux-kernel - Re: + userns-add-a-user_namespace-as-creator-owner-of-uts

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Message-ID: <20110220222853.GA2960@mail.hallyn.com>
Date:	Sun, 20 Feb 2011 22:28:53 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	"Serge E. Hallyn" <serge.hallyn@...onical.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	James Morris <jmorris@...ei.org>,
	Kees Cook <kees.cook@...onical.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: +
 userns-add-a-user_namespace-as-creator-owner-of-uts_namespace.patch added
 to -mm tree

Quoting Oleg Nesterov (oleg@...hat.com):
> > Subject: userns: add a user_namespace as creator/owner of uts_namespace
> > From: "Serge E. Hallyn" <serge@...lyn.com>
> 
> Minor nit... feel free to ignore, but can't resist.
> 
> --- a/kernel/nsproxy.c~userns-add-a-user_namespace-as-creator-owner-of-uts_namespace
> +++ a/kernel/nsproxy.c
> @@ -74,6 +74,11 @@ static struct nsproxy *create_new_namesp
>  		err = PTR_ERR(new_nsp->uts_ns);
>  		goto out_uts;
>  	}
> +	if (new_nsp->uts_ns != tsk->nsproxy->uts_ns) {
> +		put_user_ns(new_nsp->uts_ns->user_ns);
> +		new_nsp->uts_ns->user_ns = task_cred_xxx(tsk, user)->user_ns;
> +		get_user_ns(new_nsp->uts_ns->user_ns);
> +	}
> 
> Looks correct, but confusing imho.
> 
> "new_nsp->uts_ns != tsk->nsproxy->uts_ns" is a bit strange way to
> check "flags & CLONE_NEWUTS", no?
> 
> And since copy_utsname() already checks CLONE_NEWUTS, can't we move
> this code into copy_utsname() or clone_uts_ns() ?

Yup.  I had only found the bug this addresses very late so sort of
felt I should keep it as an obvious band-aid for now.  I've got a
lot of feedback to address on this set (!), and I'll do this more
cleanly as well.

Thanks for taking a look, Oleg.

-serge
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