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

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Message-ID: <87cyhm7azk.ffs@tglx>
Date: Fri, 20 Dec 2024 14:14:07 +0100
From: Thomas Gleixner <tglx@...utronix.de>
To: Frederic Weisbecker <frederic@...nel.org>
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

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.