sctp: only drop the reference on the datamsg after sending a msg

If the chunks are enqueued successfully but sctp_cmd_interpreter()
return err to sctp_sendmsg() (mainly because of no mem), the chunks will
get re-queued, but we are dropping the reference and freeing them.

The fix is to just drop the reference on the datamsg just as it had
succeeded, as:
 - if the chunks weren't queued, this is enough to get them freed.
 - if they were queued, they will get freed when they finally get out or
 discarded.
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: NMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -1964,15 +1964,13 @@ static int sctp_sendmsg(struct sock *sk, struct msghdr *msg, size_t msg_len)
 	 * breaks.
 	 */
 	err = sctp_primitive_SEND(net, asoc, datamsg);
+	sctp_datamsg_put(datamsg);
 	/* Did the lower layer accept the chunk? */
-	if (err) {
-		sctp_datamsg_free(datamsg);
+	if (err)
 		goto out_free;
-	}
 
 	pr_debug("%s: we sent primitively\n", __func__);
 
-	sctp_datamsg_put(datamsg);
 	err = msg_len;
 
 	if (unlikely(wait_connect)) {