Add a missing check for negative tv_sec when setting the timeout. Also clear the entire timeout if the remaining time becomes negative instead of just clearing tv_sec or tv_nsec. OK cheloha@.

usr.sbin/cron/cron.c

···
-/*	$OpenBSD: cron.c,v 1.81 2022/07/07 20:58:57 jca Exp $	*/
+/*	$OpenBSD: cron.c,v 1.82 2022/07/08 20:47:24 millert Exp $	*/
 
 /* Copyright 1988,1990,1993,1994 by Paul Vixie
  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
···
 	clock_gettime(CLOCK_REALTIME, &t1);
 	t1.tv_sec += GMToff;
 	timeout.tv_sec = (target * SECONDS_PER_MINUTE - t1.tv_sec) + 1;
+	if (timeout.tv_sec < 0)
+		timeout.tv_sec = 0;
 	timeout.tv_nsec = 0;
 
 	pfd[0].fd = cronSock;
···
 		timespecsub(&timeout, &t1, &timeout);
 		memcpy(&t1, &t2, sizeof(t1));
 		if (timeout.tv_sec < 0)
-			timeout.tv_sec = 0;
-		if (timeout.tv_nsec < 0)
-			timeout.tv_nsec = 0;
+			timespecclear(&timeout);
 	}
 }