Index: head/sys/dev/virtio/network/if_vtnet.c
===================================================================
--- head/sys/dev/virtio/network/if_vtnet.c
+++ head/sys/dev/virtio/network/if_vtnet.c
@@ -1080,8 +1080,12 @@
 			    (IFF_PROMISC | IFF_ALLMULTI)) {
 				if (sc->vtnet_flags & VTNET_FLAG_CTRL_RX)
 					vtnet_rx_filter(sc);
-				else
-					error = ENOTSUP;
+				else {
+					ifp->if_flags |= IFF_PROMISC;
+					if ((ifp->if_flags ^ sc->vtnet_if_flags)
+					    & IFF_ALLMULTI)
+						error = ENOTSUP;
+				}
 			}
 		} else
 			vtnet_init_locked(sc);
Index: head/sys/net/if_bridge.c
===================================================================
--- head/sys/net/if_bridge.c
+++ head/sys/net/if_bridge.c
@@ -1033,9 +1033,12 @@
 		case IFT_ETHER:
 		case IFT_L2VLAN:
 			/*
-			 * Take the interface out of promiscuous mode.
+			 * Take the interface out of promiscuous mode, but only
+			 * if it was promiscuous in the first place. It might
+			 * not be if we're in the bridge_ioctl_add() error path.
 			 */
-			(void) ifpromisc(ifs, 0);
+			if (ifs->if_flags & IFF_PROMISC)
+				(void) ifpromisc(ifs, 0);
 			break;
 
 		case IFT_GIF:
@@ -1203,10 +1206,8 @@
 			break;
 	}
 
-	if (error) {
+	if (error)
 		bridge_delete_member(sc, bif, 0);
-		free(bif, M_DEVBUF);
-	}
 	return (error);
 }