[PATCH 136/139] vlan: adjust vlan_set_encap_proto() for its callers

[Luis Henriques]

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

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

From: Cong Wang <amwang@xxxxxxxxxx>

commit da8c87241c26aac81a64c7e4d21d438a33018f4e upstream.

There are two places to call vlan_set_encap_proto():
vlan_untag() and __pop_vlan_tci().

vlan_untag() assumes skb->data points after mac addr, otherwise
the following code

        vhdr = (struct vlan_hdr *) skb->data;
        vlan_tci = ntohs(vhdr->h_vlan_TCI);
        __vlan_hwaccel_put_tag(skb, vlan_tci);

        skb_pull_rcsum(skb, VLAN_HLEN);

won't be correct. But __pop_vlan_tci() assumes points _before_
mac addr.

In vlan_set_encap_proto(), it looks for some magic L2 value
after mac addr:

        rawp = skb->data;
        if (*(unsigned short *) rawp == 0xFFFF)
	...

Therefore __pop_vlan_tci() is obviously wrong.

A quick fix is avoiding using skb->data in vlan_set_encap_proto(),
use 'vhdr+1' is always correct in both cases.

Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Jesse Gross <jesse@xxxxxxxxxx>
Signed-off-by: Cong Wang <amwang@xxxxxxxxxx>
Acked-by: Jesse Gross <jesse@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Luis Henriques <luis.henriques@xxxxxxxxxxxxx>
---
 include/linux/if_vlan.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index 561e130..9b0c614 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -327,7 +327,7 @@ static inline void vlan_set_encap_proto(struct sk_buff *skb,
 					struct vlan_hdr *vhdr)
 {
 	__be16 proto;
-	unsigned char *rawp;
+	unsigned short *rawp;
 
 	/*
 	 * Was a VLAN packet, grab the encapsulated protocol, which the layer
@@ -340,8 +340,8 @@ static inline void vlan_set_encap_proto(struct sk_buff *skb,
 		return;
 	}
 
-	rawp = skb->data;
-	if (*(unsigned short *) rawp == 0xFFFF)
+	rawp = (unsigned short *)(vhdr + 1);
+	if (*rawp == 0xFFFF)
 		/*
 		 * This is a magic hack to spot IPX packets. Older Novell
 		 * breaks the protocol design and runs IPX over 802.3 without
-- 
1.8.1.2

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