netdev - [PATCH net 1/2] mptcp: more strict state checking for acks

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Message-Id: <5566ba1c4409a652440d84ff49b99e58ca998a0e.1610471474.git.pabeni@redhat.com>
Date:   Tue, 12 Jan 2021 18:25:23 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     mptcp@...ts.01.org, "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH net 1/2] mptcp: more strict state checking for acks

Syzkaller found a way to trigger division by zero
in mptcp_subflow_cleanup_rbuf().

The current checks implemented into tcp_can_send_ack()
are too week, let's be more accurate.

Reported-by: Christoph Paasch <cpaasch@...le.com>
Fixes: ea4ca586b16f ("mptcp: refine MPTCP-level ack scheduling")
Fixes: fd8976790a6c ("mptcp: be careful on MPTCP-level ack.")
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
 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 6628d8d74203..2ff8c7caf74f 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -427,7 +427,7 @@ static bool mptcp_subflow_active(struct mptcp_subflow_context *subflow)
 static bool tcp_can_send_ack(const struct sock *ssk)
 {
 	return !((1 << inet_sk_state_load(ssk)) &
-	       (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_TIME_WAIT | TCPF_CLOSE));
+	       (TCPF_SYN_SENT | TCPF_SYN_RECV | TCPF_TIME_WAIT | TCPF_CLOSE | TCPF_LISTEN));
 }
 
 static void mptcp_send_ack(struct mptcp_sock *msk)
-- 
2.26.2