ipv4: ping: Fix recvmsg MSG_OOB error handling.

Don't return an uninitialized variable as the error, return
-EOPNOTSUPP instead.
Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ping.c

@@ -630,6 +630,7 @@ static int ping_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 
 	pr_debug("ping_recvmsg(sk=%p,sk->num=%u)\n", isk, isk->inet_num);
 
+	err = -EOPNOTSUPP;
 	if (flags & MSG_OOB)
 		goto out;