[ 78/86] vlan: adjust vlan_set_encap_proto() for its callers

From: Greg Kroah-Hartman
Date: Tue Feb 26 2013 - 19:11:48 EST

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


From: Cong Wang <amwang@xxxxxxxxxx>

[ Upstream commit da8c87241c26aac81a64c7e4d21d438a33018f4e ]

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.

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

--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -327,7 +327,7 @@ static inline void vlan_set_encap_proto(
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(

- 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

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