Re: [PATCH] signal: skip blocked signals in dequeue_synchronous_signal()

[Oleg Nesterov <oleg@redhat.com>]

On 10/20, Avi Weiss wrote:
>
> dequeue_synchronous_signal() checks whether an unblocked
> synchronous signal is pending, but its queue scan can select a
> different blocked entry with a positive si_code. This can deliver
> a signal while it is still blocked.

Heh ;) I can't understand how no one noticed this before.

>  	/*
> -	 * Return the first synchronous signal in the queue.
> +	 * Return the first unblocked synchronous signal in the queue.
>  	 */
>  	list_for_each_entry(q, &pending->list, list) {
>  		/* Synchronous signals have a positive si_code */
>  		if ((q->info.si_code > SI_USER) &&
> -		    (sigmask(q->info.si_signo) & SYNCHRONOUS_MASK)) {
> +		    (sigmask(q->info.si_signo) & SYNCHRONOUS_MASK) &&
> +		    !sigismember(&tsk->blocked, q->info.si_signo)) {
>  			sync = q;
>  			goto next;
>  		}

Thanks! I'll send a minor cleanup on top of this patch later.

CC: stable@vger.kernel.org

Acked-by: Oleg Nesterov <oleg@redhat.com>