tcp: Fix a data-race around sysctl_tcp_adv_win_scale.

q2ven · davem330 · commit 36eeee75ef01 · 2022-07-22T12:06:17.000+01:00
While reading sysctl_tcp_adv_win_scale, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader. Fixes: 1da177e ("Linux-2.6.12-rc2") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
@@ -1419,7 +1419,7 @@ void tcp_select_initial_window(const struct sock *sk, int __space,
 
 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)) :

Original file line number	Diff line number	Diff line change
`@@ -1419,7 +1419,7 @@ void tcp_select_initial_window(const struct sock *sk, int __space,`
`1419`	`1419`
`1420`	`1420`	`static inline int tcp_win_from_space(const struct sock *sk, int space)`
`1421`	`1421`	`{`
`1422`		`- int tcp_adv_win_scale = sock_net(sk)->ipv4.sysctl_tcp_adv_win_scale;`
	`1422`	`+ int tcp_adv_win_scale = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_adv_win_scale);`
`1423`	`1423`
`1424`	`1424`	`return tcp_adv_win_scale <= 0 ?`
`1425`	`1425`	`(space>>(-tcp_adv_win_scale)) :`