From 0864c158836c2d0edb61f7128475e192b09bc851 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 16 Jan 2014 15:03:31 -0800 Subject: [PATCH] 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 Cc: Ben Hutchings Signed-off-by: David S. Miller --- net/ethernet/eth.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c index 8f032bae60ad..5dc638cad2e1 100644 --- a/net/ethernet/eth.c +++ b/net/ethernet/eth.c @@ -156,7 +156,9 @@ EXPORT_SYMBOL(eth_rebuild_header); */ __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_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 * 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); /* -- 2.30.2