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

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Message-ID: <20111011130836.GA5106@sergelap>
Date:	Tue, 11 Oct 2011 08:08:36 -0500
From:	"Serge E. Hallyn" <serge.hallyn@...onical.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	lkml <linux-kernel@...r.kernel.org>, richard@....at,
	Andrew Morton <akpm@...gle.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Tejun Heo <tj@...nel.org>, serge@...lyn.com
Subject: Re: [PATCH] user namespace: make signal.c respect user namespaces

Quoting Oleg Nesterov (oleg@...hat.com):
> Sorry, I missed this email...
> 
> On 10/04, Serge E. Hallyn wrote:
> >
> > Quoting Oleg Nesterov (oleg@...hat.com):
> > > --- x/kernel/signal.c
> > > +++ x/kernel/signal.c
> > > @@ -1019,6 +1019,27 @@ static inline int legacy_queue(struct si
> > >  	return (sig < SIGRTMIN) && sigismember(&signals->signal, sig);
> > >  }
> > >
> > > +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:
> >
> > If I'm reading this right, this will catch do_notify_parent, which is
> > sending signals not from current.
> 
> Argh, indeed. So we need to modify the callers.
> 
> OTOH, this is only possible if the debugger notifies tracee->real_parent,
> or we reparent to /sbin/init.

Right.  (I thought we decided that was the case anyway, but maybe I was
missing something)

> Anyways, yes, I forgot about this. Thanks.
> 
> Oleg.

I'll try to get the new patch out this week, else early next.  (Shouldn't
take long to write, but testing is another matter)

thanks,
-serge
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