xfrm: replay: Fix the update of replay_esn->oseq_hi for GSO

When skb needs GSO and wrap around happens, if xo->seq.low (seqno of
the first skb segment) is before the last seq number but oseq (seqno
of the last segment) is after it, xo->seq.low is still bigger than
replay_esn->oseq while oseq is smaller than it, so the update of
replay_esn->oseq_hi is missed for this case wrap around because of
the change in the cited commit.

For example, if sending a packet with gso_segs=3 while old
replay_esn->oseq=0xfffffffe, we calculate:
    xo->seq.low = 0xfffffffe + 1 = 0x0xffffffff
    oseq = 0xfffffffe + 3 = 0x1
(oseq < replay_esn->oseq) is true, but (xo->seq.low <
replay_esn->oseq) is false, so replay_esn->oseq_hi is not incremented.

To fix this issue, change the outer checking back for the update of
replay_esn->oseq_hi. And add new checking inside for the update of
packet's oseq_hi.

Fixes: 4b549cc ("xfrm: replay: Fix ESN wrap around for GSO")
Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Patrisious Haddad <phaddad@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

Author: Jianbo Liu

net/xfrm/xfrm_replay.c

@@ -714,10 +714,12 @@ static int xfrm_replay_overflow_offload_esn(struct xfrm_state *x, struct sk_buff
 			oseq += skb_shinfo(skb)->gso_segs;
 		}
 
-		if (unlikely(xo->seq.low < replay_esn->oseq)) {
-			XFRM_SKB_CB(skb)->seq.output.hi = ++oseq_hi;
-			xo->seq.hi = oseq_hi;
-			replay_esn->oseq_hi = oseq_hi;
+		if (unlikely(oseq < replay_esn->oseq)) {
+			replay_esn->oseq_hi = ++oseq_hi;
+			if (xo->seq.low < replay_esn->oseq) {
+				XFRM_SKB_CB(skb)->seq.output.hi = oseq_hi;
+				xo->seq.hi = oseq_hi;
+			}
 			if (replay_esn->oseq_hi == 0) {
 				replay_esn->oseq--;
 				replay_esn->oseq_hi--;