xfrm: Fix ESN sequence number handling for IPsec GSO packets.

[ Upstream commit b8b549ee ]

When IPsec offloading was introduced, we accidentally incremented
the sequence number counter on the xfrm_state by one packet
too much in the ESN case. This leads to a sequence number gap of
one packet after each GSO packet. Fix this by setting the sequence
number to the correct value.

Fixes: d7dbefc4 ("xfrm: Add xfrm_replay_overflow functions for offloading")
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/xfrm/xfrm_replay.c

@@ -658,7 +658,7 @@ static int xfrm_replay_overflow_offload_esn(struct xfrm_state *x, struct sk_buff
 		} else {
 			XFRM_SKB_CB(skb)->seq.output.low = oseq + 1;
 			XFRM_SKB_CB(skb)->seq.output.hi = oseq_hi;
-			xo->seq.low = oseq = oseq + 1;
+			xo->seq.low = oseq + 1;
 			xo->seq.hi = oseq_hi;
 			oseq += skb_shinfo(skb)->gso_segs;
 		}