sctp: prevent info leak in sctp_make_heartbeat()

The "hbinfo" struct has a 4 byte hole at the end so we have to zero it
out to prevent stack information from being disclosed.

Fixes: fe59379b ("sctp: do the basic send and recv for PLPMTUD probe")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/sm_make_chunk.c

@@ -1163,7 +1163,7 @@ struct sctp_chunk *sctp_make_heartbeat(const struct sctp_association *asoc,
 				       const struct sctp_transport *transport,
 				       __u32 probe_size)
 {
-	struct sctp_sender_hb_info hbinfo;
+	struct sctp_sender_hb_info hbinfo = {};
 	struct sctp_chunk *retval;
 
 	retval = sctp_make_control(asoc, SCTP_CID_HEARTBEAT, 0,