netdev - [PATCH net v2] flow_dissector: Check skb for VLAN only if skb specified.

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Date:   Mon, 17 Oct 2016 16:30:12 -0400
From:   Eric Garver <e@...g.me>
To:     netdev@...r.kernel.org
Cc:     Hadar Hen Zion <hadarh@...lanox.com>
Subject: [PATCH net v2] flow_dissector: Check skb for VLAN only if skb specified.

Fixes a panic when calling eth_get_headlen(). Noticed on i40e driver.

Fixes: d5709f7ab776 ("flow_dissector: For stripped vlan, get vlan info from skb->vlan_tci")
Signed-off-by: Eric Garver <e@...g.me>
---
 net/core/flow_dissector.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 1a7b80f73376..44e6ba9d3a6b 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -247,12 +247,10 @@ bool __skb_flow_dissect(const struct sk_buff *skb,
 	case htons(ETH_P_8021Q): {
 		const struct vlan_hdr *vlan;
 
-		if (skb_vlan_tag_present(skb))
+		if (skb && skb_vlan_tag_present(skb))
 			proto = skb->protocol;
 
-		if (!skb_vlan_tag_present(skb) ||
-		    proto == cpu_to_be16(ETH_P_8021Q) ||
-		    proto == cpu_to_be16(ETH_P_8021AD)) {
+		if (eth_type_vlan(proto)) {
 			struct vlan_hdr _vlan;
 
 			vlan = __skb_header_pointer(skb, nhoff, sizeof(_vlan),
-- 
2.5.5