ipvlan: fix use after free of skb

commit a534dc52 upstream.

ipvlan_handle_frame is a rx_handler, and when it returns a value other
than RX_HANDLER_CONSUMED (here, NET_RX_DROP aka RX_HANDLER_ANOTHER),
__netif_receive_skb_core expects that the skb still exists and will
process it further, but we just freed it.

Fixes: 2ad7bf36 ("ipvlan: Initial check-in of the IPVLAN driver.")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/net/ipvlan/ipvlan_core.c

@@ -607,5 +607,5 @@ rx_handler_result_t ipvlan_handle_frame(struct sk_buff **pskb)
 	WARN_ONCE(true, "ipvlan_handle_frame() called for mode = [%hx]\n",
 			  port->mode);
 	kfree_skb(skb);
-	return NET_RX_DROP;
+	return RX_HANDLER_CONSUMED;
 }