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net: eth_type_trans() should use skb_header_pointer() 

eth_type_trans() can read uninitialized memory as drivers
do not necessarily pull more than 14 bytes in skb->head before
calling it.

As David suggested, we can use skb_header_pointer() to
fix this without breaking some drivers that might not expect
eth_type_trans() pulling 2 additional bytes.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2014-01-16 15:03:31 -08:00 committed by David S. Miller
parent 7967919db6
commit 0864c15883
1 changed files with 5 additions and 2 deletions
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7
net/ethernet/eth.c
View File

@ -156,7 +156,9 @@ EXPORT_SYMBOL(eth_rebuild_header);
*/ */
__be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev) __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
{ {
struct ethhdr *eth; unsigned short _service_access_point;
const unsigned short *sap;
const struct ethhdr *eth;
skb->dev = dev; skb->dev = dev;
skb_reset_mac_header(skb); skb_reset_mac_header(skb);
@ -194,7 +196,8 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
* layer. We look for FFFF which isn't a used 802.2 SSAP/DSAP. This * layer. We look for FFFF which isn't a used 802.2 SSAP/DSAP. This
* won't work for fault tolerant netware but does for the rest. * won't work for fault tolerant netware but does for the rest.
*/ */
if (unlikely(skb->len >= 2 && *(unsigned short *)(skb->data) == 0xFFFF)) sap = skb_header_pointer(skb, 0, sizeof(*sap), &_service_access_point);
if (sap && *sap == 0xFFFF)
return htons(ETH_P_802_3); return htons(ETH_P_802_3);
/* /*