tcp: Fix a data-race around sysctl_tcp_min_rtt_wlen.

q2ven · davem330 · commit 1330ffacd05f · 2022-07-22T12:06:18.000+01:00
While reading sysctl_tcp_min_rtt_wlen, it can be changed concurrently. Thus, we need to add READ_ONCE() to its reader. Fixes: f672258 ("tcp: track min RTT using windowed min-filter") Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
@@ -3058,7 +3058,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
 
 static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us, const int flag)
 {
-	u32 wlen = sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen * HZ;
+	u32 wlen = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen) * HZ;
 	struct tcp_sock *tp = tcp_sk(sk);
 
 	if ((flag & FLAG_ACK_MAYBE_DELAYED) && rtt_us > tcp_min_rtt(tp)) {

Original file line number	Diff line number	Diff line change
`@@ -3058,7 +3058,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,`
`3058`	`3058`
`3059`	`3059`	`static void tcp_update_rtt_min(struct sock *sk, u32 rtt_us, const int flag)`
`3060`	`3060`	`{`
`3061`		`- u32 wlen = sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen * HZ;`
	`3061`	`+ u32 wlen = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_min_rtt_wlen) * HZ;`
`3062`	`3062`	`struct tcp_sock *tp = tcp_sk(sk);`
`3063`	`3063`
`3064`	`3064`	`if ((flag & FLAG_ACK_MAYBE_DELAYED) && rtt_us > tcp_min_rtt(tp)) {`