When TFO is used, the check to see if the 'C' flag (deny join id0) was
set was bypassed.

This flag can be set when TFO is used, so the check should also be done
when TFO is used.

Note that the set_fully_established label is also used when a 4th ACK is
received. In this case, deny_join_id0 will not be set.

Fixes: dfc8d0603033 ("mptcp: implement delayed seq generation for passive fastopen")
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
---
 net/mptcp/options.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/mptcp/options.c b/net/mptcp/options.c
index d47b8a9bc2df2f14645b1b3d3e10fea1b38567b1..cf531f2d815cdfbc772b837def6e7d558e64d558 100644
--- a/net/mptcp/options.c
+++ b/net/mptcp/options.c
@@ -985,14 +985,14 @@ static bool check_fully_established(struct mptcp_sock *msk, struct sock *ssk,
 		return false;
 	}
 
-	if (mp_opt->deny_join_id0)
-		WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
-
 	if (unlikely(!READ_ONCE(msk->pm.server_side)))
 		/* DO-NOT-MERGE: use WARN i/o pr_warn: only for MPTCP export */
 		WARN_ONCE(1, "bogus mpc option on established client sk");
 
 set_fully_established:
+	if (mp_opt->deny_join_id0)
+		WRITE_ONCE(msk->pm.remote_deny_join_id0, true);
+
 	mptcp_data_lock((struct sock *)msk);
 	__mptcp_subflow_fully_established(msk, subflow, mp_opt);
 	mptcp_data_unlock((struct sock *)msk);

-- 
2.51.0