netdev - Re: [PATCH v2] cls_u32: use skb_header_pointer() to dereference data safely

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Date:	Wed, 02 Jun 2010 07:15:10 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	xiaosuo@...il.com
Cc:	hadi@...erus.ca, netdev@...r.kernel.org
Subject: Re: [PATCH v2] cls_u32: use skb_header_pointer() to dereference
 data safely

From: Changli Gao <xiaosuo@...il.com>
Date: Wed,  2 Jun 2010 22:00:36 +0800

> use skb_header_pointer() to dereference data safely
> 
> the original skb->data dereference isn't safe, as there isn't any skb->len or
> skb_is_nonlinear() check. skb_header_pointer() is used instead in this patch.
> And when the skb isn't long enough, we terminate the function u32_classify()
> immediately with -1. Unaligned access is also fixed.
> 
> Signed-off-by: Changli Gao <xiaosuo@...il.com>

Please don't do so many things at once Changli.

Everything is fine except the get_unaligned() addition.  It's
intentionally not there, and by adding the get_unaligned() you're
going to kill performance as this expands to 4 byte loads per u32 key
check on RISC systems.

If it's not aligned, that's a path or configuration that will need to
be fixed up such that the accesses are aligned.

Please respin this patch with the get_unaligned() part removed.

Thanks.
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