linux-kernel - Re: [PATCH] signal/posixtimers: Handle ignore/blocked sequences correctly

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Message-ID: <Z2Vvw4_eGQAEo85P@pavilion.home>
Date: Fri, 20 Dec 2024 14:23:15 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: syzbot <syzbot+3c2e3cc60665d71de2f7@...kaller.appspotmail.com>,
	anna-maria@...utronix.de, linux-kernel@...r.kernel.org,
	peterz@...radead.org, syzkaller-bugs@...glegroups.com,
	Eric Biederman <ebiederm@...ssion.com>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [PATCH] signal/posixtimers: Handle ignore/blocked sequences
 correctly

Le Fri, Dec 20, 2024 at 02:14:07PM +0100, Thomas Gleixner a écrit :
> On Fri, Dec 20 2024 at 14:06, Frederic Weisbecker wrote:
> > Le Thu, Dec 19, 2024 at 08:46:25PM +0100, Thomas Gleixner a écrit :
> >>  		if (!list_empty(&q->list)) {
> >>  			/*
> >> -			 * If task group is exiting with the signal already pending,
> >> -			 * wait for __exit_signal() to do its job. Otherwise if
> >> -			 * ignored, it's not supposed to be queued. Try to survive.
> >> +			 * The signal was ignored and blocked. The timer
> >> +			 * expiry queued it because blocked signals are
> >> +			 * queued independent of the ignored state.
> >> +			 *
> >> +			 * The unblocking set SIGPENDING, but the signal
> >> +			 * was not yet dequeued from the pending list,
> >> +			 * which would have put it back on the ignore list.
> >
> > I must be missing something. I don't see dequeue_signal() checking if a signal
> > is ignored upon delivery.
> 
> 
> Sorry, I meant get_signal() which is what the actual signal delivery
> path on exit to user space invokes. dequeue itself does not care.
> 

Hmm, ok it eventually ignores the signal delivery to the user but:

_ Dequeue signal has delivered it to posix timers
_ The signal isn't moved back to the ignored list (or I'm missing something else?)

Thanks.