linux-kernel - Re: [RFC,PATCH] fix /sbin/init signal handling

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Date:	Tue, 21 Aug 2007 21:04:43 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	Daniel Pittman <daniel@...space.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Ingo Molnar <mingo@...e.hu>, Kirill Korotaev <dev@...ru>,
	Pavel Emelyanov <xemul@...ru>,
	Roland McGrath <roland@...hat.com>,
	Sukadev Bhattiprolu <sukadev@...ibm.com>,
	containers@...ts.osdl.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC,PATCH] fix /sbin/init signal handling

On 08/21, Serge E. Hallyn wrote:
>
> Quoting Oleg Nesterov (oleg@...sign.ru):
> > @@ -1841,14 +1865,6 @@ relock:
> >  		if (sig_kernel_ignore(signr)) /* Default is nothing. */
> >  			continue;
> > 
> > -		/*
> > -		 * Init of a pid space gets no signals it doesn't want from
> > -		 * within that pid space. It can of course get signals from
> > -		 * its parent pid space.
> > -		 */
> > -		if (current == child_reaper(current))
> > -			continue;
> > -
> 
> Ok, so the idea is that this will now be caught when the signal is sent,
> using sig_ignored(), (i.e at send_sigqueue, send_group_sigqueue,
> specific_send_sig_info, and __group_send_sig_info) and so doesn't need
> to be checked here?

Yes.

> I was hoping that meant that sig_init_ignore() would always be called
> with current as the sending process, but I guess that's not the case?

Usually current == sender, but if the signal was sent from interrupt
context, current is some random process.

> At least in get_signal_to_deliver() we might resend a signal, though
> I guess we assume the signal comes from current->parent, so maybe we
> can pass that as an argument...

get_signal_to_deliver() might resend a signal, but only when current is
ptraced. In that case the signal will be delivered even if we are init,
no problem. (except that ptracing of sub-namespace init is problem by
itself).

Thanks for looking at this!

Oleg.

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