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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Kuniyuki Iwashima <kuniyu@amazon.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.4 06/34] tcp: Fix a data-race around sysctl_tcp_adv_win_scale.
Date:   Mon,  1 Aug 2022 13:46:46 +0200
Message-Id: <20220801114128.304976802@linuxfoundation.org>
In-Reply-To: <20220801114128.025615151@linuxfoundation.org>
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From: Kuniyuki Iwashima <kuniyu@amazon.com>

commit 36eeee75ef0157e42fb6593dcc65daab289b559e upstream.

While reading sysctl_tcp_adv_win_scale, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/net/tcp.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1389,7 +1389,7 @@ void tcp_select_initial_window(const str
 
 static inline int tcp_win_from_space(const struct sock *sk, int space)
 {
-	int tcp_adv_win_scale = sock_net(sk)->ipv4.sysctl_tcp_adv_win_scale;
+	int tcp_adv_win_scale = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_adv_win_scale);
 
 	return tcp_adv_win_scale <= 0 ?
 		(space>>(-tcp_adv_win_scale)) :