[PATCH 4.9 45/61] xfrm: allow to accept packets with ipv6 NEXTHDR_HOP in xfrm_input

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Xin Long <lucien.xin@xxxxxxxxx>

commit afcaf61be9d1dbdee5ec186d1dcc67b6b692180f upstream.

For beet mode, when it's ipv6 inner address with nexthdrs set,
the packet format might be:

    ----------------------------------------------------
    | outer  |     | dest |     |      |  ESP    | ESP |
    | IP hdr | ESP | opts.| TCP | Data | Trailer | ICV |
    ----------------------------------------------------

The nexthdr from ESP could be NEXTHDR_HOP(0), so it should
continue processing the packet when nexthdr returns 0 in
xfrm_input(). Otherwise, when ipv6 nexthdr is set, the
packet will be dropped.

I don't see any error cases that nexthdr may return 0. So
fix it by removing the check for nexthdr == 0.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 net/xfrm/xfrm_input.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/xfrm/xfrm_input.c
+++ b/net/xfrm/xfrm_input.c
@@ -302,7 +302,7 @@ resume:
 		dev_put(skb->dev);
 
 		spin_lock(&x->lock);
-		if (nexthdr <= 0) {
+		if (nexthdr < 0) {
 			if (nexthdr == -EBADMSG) {
 				xfrm_audit_state_icvfail(x, skb,
 							 x->type->proto);