--- sys/geom/geom_ccd.c	2008-11-22 14:40:23.000000000 +0800
+++ /var/current/mysrc/sys/geom/geom_ccd.c	2008-11-24 16:21:07.000000000 +0800
@@ -839,6 +839,10 @@
 	int i, unit, *up;
 
 	up = gctl_get_paraml(req, "unit", sizeof (int));
+	if (up == NULL) {
+		gctl_error(req, "No '%s' argument", "unit");
+		return;
+	}
 	unit = *up;
 	sb = sbuf_new_auto();
 	LIST_FOREACH(gp, &mp->geom, geom) {