[PATCH net] tcp: fix access to sk->sk_state in tcp_poll()

[PATCH net] tcp: fix access to sk->sk_state in tcp_poll()

[Davide Caratti]

avoid direct access to sk->sk_state when tcp_poll() is called on a socket
using active TCP fastopen with deferred connect. Use local variable
'state', which stores the result of sk_state_load(), like it was done in
commit 00fd38d938db ("tcp: ensure proper barriers in lockless contexts").

Fixes: 19f6d3f3c842 ("net/tcp-fastopen: Add new API support")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
---
 net/ipv4/tcp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 40ba424..2dc7fcf 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -533,7 +533,7 @@ unsigned int tcp_poll(struct file *file, struct socket *sock, poll_table *wait)
 
 		if (tp->urg_data & TCP_URG_VALID)
 			mask |= POLLPRI;
-	} else if (sk->sk_state == TCP_SYN_SENT && inet_sk(sk)->defer_connect) {
+	} else if (state == TCP_SYN_SENT && inet_sk(sk)->defer_connect) {
 		/* Active TCP fastopen socket with defer_connect
 		 * Return POLLOUT so application can call write()
 		 * in order for kernel to generate SYN+data
-- 
2.7.4

Re: [PATCH net] tcp: fix access to sk->sk_state in tcp_poll()

[Wei Wang]

On Wed, Apr 26, 2017 at 10:07 AM, Davide Caratti <dcaratti@redhat.com> wrote:
> avoid direct access to sk->sk_state when tcp_poll() is called on a socket
> using active TCP fastopen with deferred connect. Use local variable
> 'state', which stores the result of sk_state_load(), like it was done in
> commit 00fd38d938db ("tcp: ensure proper barriers in lockless contexts").
>
> Fixes: 19f6d3f3c842 ("net/tcp-fastopen: Add new API support")
> Signed-off-by: Davide Caratti <dcaratti@redhat.com>

Acked-by: Wei Wang <weiwan@google.com>
Thanks for the fix.

Re: [PATCH net] tcp: fix access to sk->sk_state in tcp_poll()

[David Miller]

From: Davide Caratti <dcaratti@redhat.com>
Date: Wed, 26 Apr 2017 19:07:35 +0200

> avoid direct access to sk->sk_state when tcp_poll() is called on a socket
> using active TCP fastopen with deferred connect. Use local variable
> 'state', which stores the result of sk_state_load(), like it was done in
> commit 00fd38d938db ("tcp: ensure proper barriers in lockless contexts").
> 
> Fixes: 19f6d3f3c842 ("net/tcp-fastopen: Add new API support")
> Signed-off-by: Davide Caratti <dcaratti@redhat.com>

Applied.