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

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

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.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@google.com>
Reported-by: Wei Wang <weiwan@google.com>
Cc: Arjun Roy <arjunroy@google.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

Re: [PATCH net-next] tcp: tcp_data_ready() must look at SOCK_DONE

[Wei Wang]

On Sat, Feb 13, 2021 at 6:26 AM Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> From: Eric Dumazet <edumazet@google.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@google.com>
> Reported-by: Wei Wang <weiwan@google.com>
> Cc: Arjun Roy <arjunroy@google.com>
> ---
Thanks Eric for the fix!

Reviewed-by: Wei Wang <weiwan@google.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
>

Re: [PATCH net-next] tcp: tcp_data_ready() must look at SOCK_DONE

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Sat, 13 Feb 2021 06:26:34 -0800 you wrote:
> From: Eric Dumazet <edumazet@google.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
> 
> [...]

Here is the summary with links:
  - [net-next] tcp: tcp_data_ready() must look at SOCK_DONE
    https://git.kernel.org/netdev/net-next/c/39354eb29f59

You are awesome, thank you!
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