diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a9f0e646e92e512e7447732c399c9f41cd61cba7..255493c4acc3386d2e6b2cfaa9116b4ec6449031 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3576,7 +3576,7 @@ static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb)
 	/* 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;