[PATCH 4.20 012/127] openvswitch: Fix IPv6 later frags parsing

[Greg Kroah-Hartman]

4.20-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Yi-Hung Wei <yihung.wei@xxxxxxxxx>

[ Upstream commit 41e4e2cd75346667b0c531c07dab05cce5b06d15 ]

The previous commit fa642f08839b
("openvswitch: Derive IP protocol number for IPv6 later frags")
introduces IP protocol number parsing for IPv6 later frags that can mess
up the network header length calculation logic, i.e. nh_len < 0.
However, the network header length calculation is mainly for deriving
the transport layer header in the key extraction process which the later
fragment does not apply.

Therefore, this commit skips the network header length calculation to
fix the issue.

Reported-by: Chris Mi <chrism@xxxxxxxxxxxx>
Reported-by: Greg Rose <gvrose8192@xxxxxxxxx>
Fixes: fa642f08839b ("openvswitch: Derive IP protocol number for IPv6 later frags")
Signed-off-by: Yi-Hung Wei <yihung.wei@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/openvswitch/flow.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/net/openvswitch/flow.c
+++ b/net/openvswitch/flow.c
@@ -276,10 +276,12 @@ static int parse_ipv6hdr(struct sk_buff
 
 	nexthdr = ipv6_find_hdr(skb, &payload_ofs, -1, &frag_off, &flags);
 	if (flags & IP6_FH_F_FRAG) {
-		if (frag_off)
+		if (frag_off) {
 			key->ip.frag = OVS_FRAG_TYPE_LATER;
-		else
-			key->ip.frag = OVS_FRAG_TYPE_FIRST;
+			key->ip.proto = nexthdr;
+			return 0;
+		}
+		key->ip.frag = OVS_FRAG_TYPE_FIRST;
 	} else {
 		key->ip.frag = OVS_FRAG_TYPE_NONE;
 	}