From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: [RFC][PATCH 2/2] Prevent container-inits from using CLONE_PARENT
Date: Thu, 18 Jun 2009 17:42:16 +0200
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To: Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
Cc: Containers <containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, "David C. Hansen" <haveblue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>, Alexey Dobriyan <adobriyan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, roland-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
List-Id: containers.vger.kernel.org

On 06/18, Oleg Nesterov wrote:
>
> On 06/17, Sukadev Bhattiprolu wrote:
> >
> > @@ -974,6 +974,14 @@ static struct task_struct *copy_process(
> >  	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
> >  		return ERR_PTR(-EINVAL);
> >
> > +	/*
> > +	 * To keep pid namespace semantics simple, prevent container-inits
> > +	 * from creating siblings.
> > +	 */
> > +	if ((clone_flags & CLONE_PARENT) &&
> > +			is_container_init(current) && !is_global_init(current))
>
> Both is_ checks are not right afaics. There are per-thread. This means
> that container-init can do clone(CLONE_THREAD), and then this thread
> does CLONE_PARENT and fools copy_process().
>
> As for !is_global_init(). I never understood what should we do if the
> global init does CLONE_PARENT, this attaches another process to swapper,
> not good.

Hmm. And idle threads run with ->action[SIGHLD] == SIG_DFL, so this is
really wrong. Fortunately, we can trust the global init.

Oleg.