1 files changed, 4 insertions, 0 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index d9b83d198c3d..b5e315f13641 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1585,6 +1585,10 @@ static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb,
                 }
         }
 
+        /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
+        if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una))
+                goto fallback;
+
         if (!skb_shift(prev, skb, len))
                 goto fallback;
         if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack))