From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Wed, 20 Jul 2022 16:50:13 +0000 (-0700)
Subject: tcp: Fix a data-race around sysctl_tcp_app_win.
X-Git-Tag: v5.4.209~30
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f4b83df0110569cf0ca33e4e01ae59adbbc8710a;p=thirdparty%2Fkernel%2Fstable.git

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 01def4f67fcde..0fcb741778fa5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -439,7 +439,7 @@ static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb)
  */
 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;