Index: if_tun.c
===================================================================
RCS file: /cvs/src/sys/net/if_tun.c,v
retrieving revision 1.181
diff -u -p -r1.181 if_tun.c
--- if_tun.c	24 Feb 2018 07:20:04 -0000	1.181
+++ if_tun.c	12 Nov 2018 06:02:51 -0000
@@ -193,6 +193,9 @@ tun_create(struct if_clone *ifc, int uni
 	struct tun_softc	*tp;
 	struct ifnet		*ifp;
 
+	if (unit > minor(~0U))
+		return (ENXIO);
+
 	tp = malloc(sizeof(*tp), M_DEVBUF, M_WAITOK|M_ZERO);
 	tp->tun_unit = unit;
 	tp->tun_flags = TUN_INITED|TUN_STAYUP;