linux-kernel - Re: [RFC][PATCH 6/6][v3] Protect cinit from blocked fatal signals

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Message-ID: <20081222233855.GA13079@us.ibm.com>
Date:	Mon, 22 Dec 2008 15:38:55 -0800
From:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	ebiederm@...ssion.com, roland@...hat.com, bastian@...di.eu.org,
	daniel@...ac.com, xemul@...nvz.org, containers@...ts.osdl.org,
	linux-kernel@...r.kernel.org, sukadev@...ibm.com
Subject: Re: [RFC][PATCH 6/6][v3] Protect cinit from blocked fatal signals

Oleg Nesterov [oleg@...hat.com] wrote:
| > @@ -1907,9 +1943,10 @@ relock:
| >
| >  		/*
| >  		 * Global init gets no signals it doesn't want.
| > +		 * Container-init gets no signals it doesn't want from same
| > +		 * container.
| >  		 */
| > -		if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
| > -		    !signal_group_exit(signal))
| > +		if (sig_unkillable(signal, signr) && !signal_group_exit(signal))
| >  			continue;
| 
| Again, I do not understand why do we need SIGNAL_UNKILLABLE_FROM_NS.
| 
| I thought about the change in get_signal_to_deliver() during the
| previous discussion, and I think what we need is:
| 
| 		if (unlikely(signal->flags & SIGNAL_UNKILLABLE) &&
| 		    !sig_kernel_only(sig))
| 			continue;
| 
| and this was yet another reason for "protect init from unwanted signals more".

I was trying to avoid the clearing of the SIGNAL_UNKILLABLE in
send_signal() that we had last time.

But yes, you are right. I even had a BUG_ON() to confirm SIGKILL/SIGSTOP
will never happen for global-init :-). If so, SIGKLL/SIGSTOP to an init
can come only from parent ns.

So, yes, we can drop this flag.
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