net: sctp: sctp_sf_do_prm_asoc: do SCTP_CMD_INIT_CHOOSE_TRANSPORT first

While this currently cannot trigger any NULL pointer dereference in
sctp_seq_dump_local_addrs(), better change the order of commands to
prevent a future bug to happen. Although we first add SCTP_CMD_NEW_ASOC
and then set the SCTP_CMD_INIT_CHOOSE_TRANSPORT, it is okay for now,
since this primitive is only called by sctp_connect() or sctp_sendmsg()
with sctp_assoc_add_peer() set first. However, lets do this precaution
and first set the transport and then add it to the association hashlist
to prevent in future something to possibly triggering this.

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/sm_statefuns.c

@@ -4632,16 +4632,16 @@ sctp_disposition_t sctp_sf_do_prm_asoc(struct net *net,
 	if (!repl)
 		goto nomem;
 
+	/* Choose transport for INIT. */
+	sctp_add_cmd_sf(commands, SCTP_CMD_INIT_CHOOSE_TRANSPORT,
+			SCTP_CHUNK(repl));
+
 	/* Cast away the const modifier, as we want to just
 	 * rerun it through as a sideffect.
 	 */
 	my_asoc = (struct sctp_association *)asoc;
 	sctp_add_cmd_sf(commands, SCTP_CMD_NEW_ASOC, SCTP_ASOC(my_asoc));
 
-	/* Choose transport for INIT. */
-	sctp_add_cmd_sf(commands, SCTP_CMD_INIT_CHOOSE_TRANSPORT,
-			SCTP_CHUNK(repl));
-
 	/* After sending the INIT, "A" starts the T1-init timer and
 	 * enters the COOKIE-WAIT state.
 	 */