[IPV4]: Do not leak IP options.

If the user makes ip_cmsg_send call ip_options_get
multiple times, we leak kmalloced IP options data.

Noticed by Georgi Guninski.
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/ip_options.c

@@ -515,6 +515,8 @@ int ip_options_get(struct ip_options **optp, unsigned char *data, int optlen, in
 		kfree(opt);
 		return -EINVAL;
 	}
+	if (*optp)
+		kfree(*optp);
 	*optp = opt;
 	return 0;
 }