macvlan: Check return of dev_set_allmulti

allmulti might overflow.
Commit: "netdevice: Fix promiscuity and allmulti overflow" in net-next makes
dev_set_promiscuity/allmulti return error number if overflow happened.

Here, we check the positive increment for allmulti to get error return.
Signed-off-by: Wang Chen <wangchen@cn.fujitsu.com>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macvlan.c

@@ -189,12 +189,20 @@ static int macvlan_open(struct net_device *dev)
 
 	err = dev_unicast_add(lowerdev, dev->dev_addr, ETH_ALEN);
 	if (err < 0)
-		return err;
-	if (dev->flags & IFF_ALLMULTI)
-		dev_set_allmulti(lowerdev, 1);
+		goto out;
+	if (dev->flags & IFF_ALLMULTI) {
+		err = dev_set_allmulti(lowerdev, 1);
+		if (err < 0)
+			goto del_unicast;
+	}
 
 	hlist_add_head_rcu(&vlan->hlist, &port->vlan_hash[dev->dev_addr[5]]);
 	return 0;
+
+del_unicast:
+	dev_unicast_delete(lowerdev, dev->dev_addr, ETH_ALEN);
+out:
+	return err;
 }
 
 static int macvlan_stop(struct net_device *dev)