linux-kernel - Re: [PATCH] user namespace: make signal.c respect user namespaces

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Date:	Sun, 9 Oct 2011 21:03:44 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	"Serge E. Hallyn" <serge.hallyn@...onical.com>,
	lkml <linux-kernel@...r.kernel.org>, richard@....at,
	Andrew Morton <akpm@...gle.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH] user namespace: make signal.c respect user namespaces

On 10/08, Serge E. Hallyn wrote:
>
> Quoting Oleg Nesterov (oleg@...hat.com):
> >
> > +static inline fixup_uid(struct siginfo *info, struct task_struct *t)
> > +{
> > +#ifdef CONFIG_USER_NS
> > +	if (current_user_ns() == task_cred_xxx(t, user_ns)))
> > +#endif
> > +		return;
> > +
> > +	if (SI_FROMKERNEL(info))
> > +		switch (info->si_code & __SI_MASK) {
> > +			default:
> > +				return;
> > +
> > +			case __SI_CHLD:
>
> After looking a bit more, I really think the __SI_CHLD case just needs to
> always be converted at the callers (i.e. do_notify_parent).

Yes, unfortunately.

> > +			case __SI_MESGQ:
>
> This can be done like this, but if this is going to be the only case of
> a SI_FROMKERNEL not being converted at the caller, and there is aiui only
> one caller (__do_notivy in ipc/mmqueue.c), it seems better to just have
> fixup_uid() always return for SI_FROMKERNEL(info).

Yes, agreed.

Oleg.

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