UPSTREAM: mptcp: really cope with fastopen race

Fastopen and PM-trigger subflow shutdown can race, as reported by
syzkaller.

In my first attempt to close such race, I missed the fact that
the subflow status can change again before the subflow_state_change
callback is invoked.

Address the issue additionally copying with all the states directly
reachable from TCP_FIN_WAIT1.

Fixes: 1e777f3 ("mptcp: add MSG_FASTOPEN sendmsg flag support")
Fixes: 4fd19a307016 ("mptcp: fix inconsistent state on fastopen race")
Cc: stable@vger.kernel.org
Reported-by: syzbot+c53d4d3ddb327e80bc51@syzkaller.appspotmail.com
Closes: multipath-tcp/mptcp_net-next#458
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit 337cebbd850f94147cee05252778f8f78b8c337f)

BUG=None
TEST=None

Signed-off-by: Linux Patches Robot <linux-patches-robot@chromeos-missing-patches.google.com.iam.gserviceaccount.com>
Change-Id: I38c3ef0dd0901d03152693851a8cc21c46f904d2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/5316317
Reviewed-by: Sean Paul <sean@poorly.run>
Commit-Queue: Tzung-Bi Shih <tzungbi@chromium.org>
Reviewed-by: Tzung-Bi Shih <tzungbi@chromium.org>

net/mptcp/protocol.h

@@ -1104,7 +1104,8 @@ static inline bool subflow_simultaneous_connect(struct sock *sk)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
 
-	return (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_FIN_WAIT1) &&
+	return (1 << sk->sk_state) &
+	       (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2 | TCPF_CLOSING) &&
 	       is_active_ssk(subflow) &&
 	       !subflow->conn_finished;
 }