linux-kernel - [PATCH net 3/4] mptcp: avoid bogus reset on fallback close

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Message-Id: <20230803-upstream-net-20230803-misc-fixes-6-5-v1-3-6671b1ab11cc@tessares.net>
Date:   Thu, 03 Aug 2023 18:27:29 +0200
From:   Matthieu Baerts <matthieu.baerts@...sares.net>
To:     mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>,
        Geliang Tang <geliang.tang@...e.com>
Cc:     Andrea Claudi <aclaudi@...hat.com>, netdev@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
        Matthieu Baerts <matthieu.baerts@...sares.net>,
        stable@...r.kernel.org
Subject: [PATCH net 3/4] mptcp: avoid bogus reset on fallback close

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

Since the blamed commit, the MPTCP protocol unconditionally sends
TCP resets on all the subflows on disconnect().

That fits full-blown MPTCP sockets - to implement the fastclose
mechanism - but causes unexpected corruption of the data stream,
caught as sporadic self-tests failures.

Fixes: d21f83485518 ("mptcp: use fastclose on more edge scenarios")
Cc: stable@...r.kernel.org
Tested-by: Matthieu Baerts <matthieu.baerts@...sares.net>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/419
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Reviewed-by: Matthieu Baerts <matthieu.baerts@...sares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@...sares.net>
---
 net/mptcp/protocol.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 3317d1cca156..ac7c11a5cbe5 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -2335,7 +2335,7 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
 
 	lock_sock_nested(ssk, SINGLE_DEPTH_NESTING);
 
-	if (flags & MPTCP_CF_FASTCLOSE) {
+	if ((flags & MPTCP_CF_FASTCLOSE) && !__mptcp_check_fallback(msk)) {
 		/* be sure to force the tcp_disconnect() path,
 		 * to generate the egress reset
 		 */

-- 
2.40.1