netdev - Re: [BUG] eth_type_trans() can access stale data

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Message-Id: <20140115.154805.1403628531019301276.davem@davemloft.net>
Date:	Wed, 15 Jan 2014 15:48:05 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [BUG] eth_type_trans() can access stale data

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 14 Jan 2014 15:52:21 -0800

> @@ -194,7 +194,8 @@ __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))
> +	if (unlikely(skb_headlen(skb) >= 2 &&
> +		     *(unsigned short *)(skb->data) == 0xFFFF))
>  		return htons(ETH_P_802_3);

I think using skb_header_pointer() will essentially have the same cost,
why not use it instead?

Thanks.
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