diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2d656eef7f8e..d4c51158470f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2478,6 +2478,9 @@ static void tcp_cwnd_reduction(struct sock *sk, const int prior_unsacked,
 	int newly_acked_sacked = prior_unsacked -
 				 (tp->packets_out - tp->sacked_out);
 
+	if (newly_acked_sacked <= 0 || WARN_ON_ONCE(!tp->prior_cwnd))
+		return;
+
 	tp->prr_delivered += newly_acked_sacked;
 	if (delta < 0) {
 		u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered +