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

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Message-ID: <1389903345.31367.424.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Thu, 16 Jan 2014 12:15:45 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [BUG] eth_type_trans() can access stale data

On Wed, 2014-01-15 at 15:48 -0800, David Miller wrote:
> 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?

Yes, we can try this, I'll send a patch, thanks.


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