tcp: Fix a data-race around sysctl_tcp_app_win.

commit 02ca527ac5581cf56749db9fd03d854e842253dd upstream.

While reading sysctl_tcp_app_win, 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>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index e066c52..1c94051 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -526,7 +526,7 @@ static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb,
  */
 static void tcp_init_buffer_space(struct sock *sk)
 {
-       int tcp_app_win = sock_net(sk)->ipv4.sysctl_tcp_app_win;
+       int tcp_app_win = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_app_win);
        struct tcp_sock *tp = tcp_sk(sk);
        int maxwin;