linux-kernel - [PATCH 4.11 09/28] tcp: fix access to sk->sk_state in tcp

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Date:   Thu, 11 May 2017 16:12:26 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Davide Caratti <dcaratti@...hat.com>,
        Wei Wang <weiwan@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.11 09/28] tcp: fix access to sk->sk_state in tcp_poll()

4.11-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Davide Caratti <dcaratti@...hat.com>


[ Upstream commit d68be71ea14d609a5f31534003319be5db422595 ]

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@...hat.com>
Acked-by: Wei Wang <weiwan@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/tcp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -533,7 +533,7 @@ unsigned int tcp_poll(struct file *file,
 
 		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