1 files changed, 10 insertions, 4 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a13692560e63..a28e4db8a952 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5543,6 +5543,9 @@ slow_path:
         if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb))
                 goto csum_error;
 
+        if (!th->ack)
+                goto discard;
+
         /*
          *      Standard slow path.
          */
@@ -5551,7 +5554,7 @@ slow_path:
                 return 0;
 
 step5:
-        if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0)
+        if (tcp_ack(sk, skb, FLAG_SLOWPATH) < 0)
                 goto discard;
 
         /* ts_recent update must be made after we are sure that the packet
@@ -5984,11 +5987,15 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                 if (tcp_check_req(sk, skb, req, NULL, true) == NULL)
                         goto discard;
         }
+
+        if (!th->ack)
+                goto discard;
+
         if (!tcp_validate_incoming(sk, skb, th, 0))
                 return 0;
 
         /* step 5: check the ACK field */
-        if (th->ack) {
+        if (true) {
                 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0;
 
                 switch (sk->sk_state) {
@@ -6138,8 +6145,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
                         }
                         break;
                 }
-        } else
-                goto discard;
+        }
 
         /* ts_recent update must be made after we are sure that the packet
          * is in window.