diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 2fa55f57ac06584bfd9b555799ceb3bbfb7e1b4e..9f4380662196d277165b12040bac6236bf2c617d 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -112,6 +112,7 @@ int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2;
 #define FLAG_DSACKING_ACK	0x800 /* SACK blocks contained D-SACK info */
 #define FLAG_SACK_RENEGING	0x2000 /* snd_una advanced to a sacked seq */
 #define FLAG_UPDATE_TS_RECENT	0x4000 /* tcp_replace_ts_recent() */
+#define FLAG_NO_CHALLENGE_ACK	0x8000 /* do not call tcp_send_challenge_ack()	*/
 
 #define FLAG_ACKED		(FLAG_DATA_ACKED|FLAG_SYN_ACKED)
 #define FLAG_NOT_DUP		(FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
@@ -3568,7 +3569,8 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	if (before(ack, prior_snd_una)) {
 		/* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
 		if (before(ack, prior_snd_una - tp->max_window)) {
-			tcp_send_challenge_ack(sk, skb);
+			if (!(flag & FLAG_NO_CHALLENGE_ACK))
+				tcp_send_challenge_ack(sk, skb);
 			return -1;
 		}
 		goto old_ack;
@@ -5951,13 +5953,17 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 
 	/* step 5: check the ACK field */
 	acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
-				      FLAG_UPDATE_TS_RECENT) > 0;
+				      FLAG_UPDATE_TS_RECENT |
+				      FLAG_NO_CHALLENGE_ACK) > 0;
 
+	if (!acceptable) {
+		if (sk->sk_state == TCP_SYN_RECV)
+			return 1;	/* send one RST */
+		tcp_send_challenge_ack(sk, skb);
+		goto discard;
+	}
 	switch (sk->sk_state) {
 	case TCP_SYN_RECV:
-		if (!acceptable)
-			return 1;
-
 		if (!tp->srtt_us)
 			tcp_synack_rtt_meas(sk, req);
 
@@ -6026,14 +6032,6 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 		 * our SYNACK so stop the SYNACK timer.
 		 */
 		if (req) {
-			/* Return RST if ack_seq is invalid.
-			 * Note that RFC793 only says to generate a
-			 * DUPACK for it but for TCP Fast Open it seems
-			 * better to treat this case like TCP_SYN_RECV
-			 * above.
-			 */
-			if (!acceptable)
-				return 1;
 			/* We no longer need the request sock. */
 			reqsk_fastopen_remove(sk, req, false);
 			tcp_rearm_rto(sk);