diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index debfff94f3af5a550f2a4975ef25faa4c97cef14..d386a69b1c057a36ba4256b4c24973f2b8fb9598 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3629,7 +3629,7 @@ static void tcp_send_challenge_ack(struct sock *sk)
 	/* Then check host-wide RFC 5961 rate limit. */
 	now = jiffies / HZ;
 	if (now != challenge_timestamp) {
-		u32 ack_limit = net->ipv4.sysctl_tcp_challenge_ack_limit;
+		u32 ack_limit = READ_ONCE(net->ipv4.sysctl_tcp_challenge_ack_limit);
 		u32 half = (ack_limit + 1) >> 1;
 
 		challenge_timestamp = now;