linux-kernel - [PATCH net 6/7] mptcp: really cope with fastopen race

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Date: Thu, 08 Feb 2024 19:03:54 +0100
From: "Matthieu Baerts (NGI0)" <matttbe@...nel.org>
To: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>, 
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>, 
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, 
 Paolo Abeni <pabeni@...hat.com>, Kishen Maloor <kishen.maloor@...el.com>, 
 Florian Westphal <fw@...len.de>, 
 Peter Krystad <peter.krystad@...ux.intel.com>, 
 Dmytro Shytyi <dmytro@...tyi.net>, 
 Benjamin Hesmans <benjamin.hesmans@...sares.net>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Christoph Paasch <cpaasch@...le.com>, 
 "Matthieu Baerts (NGI0)" <matttbe@...nel.org>, stable@...r.kernel.org, 
 syzbot+c53d4d3ddb327e80bc51@...kaller.appspotmail.com
Subject: [PATCH net 6/7] mptcp: really cope with fastopen race

From: Paolo Abeni <pabeni@...hat.com>

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: 1e777f39b4d7 ("mptcp: add MSG_FASTOPEN sendmsg flag support")
Fixes: 4fd19a307016 ("mptcp: fix inconsistent state on fastopen race")
Cc: stable@...r.kernel.org
Reported-by: syzbot+c53d4d3ddb327e80bc51@...kaller.appspotmail.com
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/458
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Reviewed-by: Mat Martineau <martineau@...nel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
---
 net/mptcp/protocol.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index fefcbf585411..ed50f2015dc3 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1129,7 +1129,8 @@ 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;
 }

-- 
2.43.0