From: Boris Sukholitko <boris.sukholitko@broadcom.com>
Date: Wed, 29 Sep 2021 14:32:23 +0300
Subject: dissector: do not set invalid PPP protocol
Patch-mainline: v5.16-rc1
Git-commit: 2e861e5e97175dfa7b7bc055c45acdc06d2301d3
References: jsc#PED-376

The following flower filter fails to match non-PPP_IP{V6} packets
wrapped in PPP_SES protocol:

tc filter add dev eth0 ingress protocol ppp_ses flower \
        action simple sdata hi64

The reason is that proto local variable is being set even when
FLOW_DISSECT_RET_OUT_BAD status is returned.

The fix is to avoid setting proto variable if the PPP protocol is unknown.

Signed-off-by: Boris Sukholitko <boris.sukholitko@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/core/flow_dissector.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1196,9 +1196,8 @@ proto_again:
 			break;
 		}
 
-		proto = hdr->proto;
 		nhoff += PPPOE_SES_HLEN;
-		switch (proto) {
+		switch (hdr->proto) {
 		case htons(PPP_IP):
 			proto = htons(ETH_P_IP);
 			fdret = FLOW_DISSECT_RET_PROTO_AGAIN;