netdev - [PATCH net-next] tcp: tcp_data_ready() must look at SOCK

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Message-Id: <20210213142634.3237642-1-eric.dumazet@gmail.com>
Date:   Sat, 13 Feb 2021 06:26:34 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Wei Wang <weiwan@...gle.com>, Arjun Roy <arjunroy@...gle.com>
Subject: [PATCH net-next] tcp: tcp_data_ready() must look at SOCK_DONE

From: Eric Dumazet <edumazet@...gle.com>

My prior cleanup missed that tcp_data_ready() has to look at SOCK_DONE.
Otherwise, an application using SO_RCVLOWAT will not get EPOLLIN event
if a FIN is received in the middle of expected payload.

The reason SOCK_DONE is not examined in tcp_epollin_ready()
is that tcp_poll() catches the FIN because tcp_fin()
is also setting RCV_SHUTDOWN into sk->sk_shutdown

Fixes: 05dc72aba364 ("tcp: factorize logic into tcp_epollin_ready()")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Wei Wang <weiwan@...gle.com>
Cc: Arjun Roy <arjunroy@...gle.com>
---
 net/ipv4/tcp_input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e32a7056cb7640c67ef2d6a4d9484684d2602fcd..69a545db80d2ead47ffcf2f3819a6d066e95f35d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4924,7 +4924,7 @@ int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
 
 void tcp_data_ready(struct sock *sk)
 {
-	if (tcp_epollin_ready(sk, sk->sk_rcvlowat))
+	if (tcp_epollin_ready(sk, sk->sk_rcvlowat) || sock_flag(sk, SOCK_DONE))
 		sk->sk_data_ready(sk);
 }
 
-- 
2.30.0.478.g8a0d178c01-goog