fixup: sctp: verify size of a new chunk in _sctp_make_chunk()

BugLink: http://bugs.launchpad.net/bugs/1764627

Ben writes:
> > +	int chunklen;
> > +
> > +	chunklen = sizeof(*chunk_hdr) + paylen;
>
> I think this length still needs to be rounded up (with WORD_ROUND here,
> instead of SCTP_PAD4 upstream).

So here's a fix for this problem.
Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

net/sctp/sm_make_chunk.c

@@ -1369,7 +1369,7 @@ static struct sctp_chunk *_sctp_make_chunk(const struct sctp_association *asoc,
 	struct sock *sk;
 	int chunklen;
 
-	chunklen = sizeof(*chunk_hdr) + paylen;
+	chunklen = WORD_ROUND(sizeof(*chunk_hdr) + paylen);
 	if (chunklen > SCTP_MAX_CHUNK_LEN)
 		goto nodata;