Index: head/sys/dev/hyperv/netvsc/if_hn.c
===================================================================
--- head/sys/dev/hyperv/netvsc/if_hn.c
+++ head/sys/dev/hyperv/netvsc/if_hn.c
@@ -1161,6 +1161,13 @@
 	    strcmp(ifp->if_dname, "vlan") == 0)
 		return (false);
 
+	/*
+	 * During detach events ifp->if_addr might be NULL.
+	 * Make sure the bcmp() below doesn't panic on that:
+	 */
+	if (ifp->if_addr == NULL || hn_ifp->if_addr == NULL)
+		return (false);
+
 	if (bcmp(IF_LLADDR(ifp), IF_LLADDR(hn_ifp), ETHER_ADDR_LEN) != 0)
 		return (false);