From: Todd C. Miller <millert@openbsd.org>
Subject: Re: readpassphrase(3): avoid spin on ignored signals
To: Damien Miller <djm@mindrot.org>
Cc: Philip Guenther <guenther@gmail.com>, tech@openbsd.org
Date: Tue, 15 Sep 2026 10:44:17 -0600

On Tue, 15 Sep 2026 17:20:22 +1000, Damien Miller wrote:

> Something like the below?

That looks reasonable, though the special case for "old == NULL" makes
me a little uncomfortable.  Another alternative would be:

/* Like sigaction(2) but preserves SIG_IGN */
static void
sigaction_except_ign(int signum, struct sigaction *act, struct sigaction *old)
{
	struct sigaction sabuf;

	if (old == NULL)
		old = &sabuf;

	(void)sigaction(signum, act, old);
	/* Reinstate SIG_IGN; we don't want to override this */
	if (old->sa_handler == SIG_IGN && act->sa_handler != SIG_IGN)
		(void)sigaction(signum, old, NULL);
}