mptcp: ensure subflow is unhashed before cleaning the backlog

While tacking care of the mptcp-level listener I unintentionally
moved the subflow level unhash after the subflow listener backlog
cleanup.

That could cause some nasty race and makes the code harder to read.

Address the issue restoring the proper order of operations.

Fixes: 57fc0f1 ("mptcp: ensure listener is unhashed before updating the sk status")
Cc: [email protected]
Signed-off-by: Paolo Abeni <[email protected]>
Reviewed-by: Matthieu Baerts <[email protected]>
Signed-off-by: Matthieu Baerts <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: Paolo Abeni

net/mptcp/protocol.c

@@ -2909,10 +2909,10 @@ static void mptcp_check_listen_stop(struct sock *sk)
 		return;
 
 	lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
+	tcp_set_state(ssk, TCP_CLOSE);
 	mptcp_subflow_queue_clean(sk, ssk);
 	inet_csk_listen_stop(ssk);
 	mptcp_event_pm_listener(ssk, MPTCP_EVENT_LISTENER_CLOSED);
-	tcp_set_state(ssk, TCP_CLOSE);
 	release_sock(ssk);
 }