packet: fix possible dev refcnt leak when bind fail

If bind is fail when bind is called after set PACKET_FANOUT
sock option, the dev refcnt will leak.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/packet/af_packet.c

@@ -2448,8 +2448,12 @@ static int packet_do_bind(struct sock *sk, struct net_device *dev, __be16 protoc
 {
 	struct packet_sock *po = pkt_sk(sk);
 
-	if (po->fanout)
+	if (po->fanout) {
+		if (dev)
+			dev_put(dev);
+
 		return -EINVAL;
+	}
 
 	lock_sock(sk);