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From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH 00/17] ATM fixes for pppoatm/br2684
Date: Sat, 01 Dec 2012 20:49:06 -0500 (EST)
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From: David Woodhouse <dwmw2@infradead.org>
Date: Sun, 02 Dec 2012 00:40:47 +0000

> On Sat, 2012-12-01 at 17:33 +0000, David Woodhouse wrote:
>> 
>> Very glad I added the BUILD_BUG_ON on the cb struct size now. Perhaps
>> there should be a generic helper for that? Something like
>>  skb_cb_cast(struct foo_cb, skb) could do it automatically...?
> 
> Something like this, perhaps? Using skb_cast_cb() would then make it
> fairly much impossible to accidentally overflow the size of the skb cb.

I actually prefer what we do now, which is do the BUILD_BUG_ON()
once in the subsystem specific code, usually the initializer.

It's part of creating a new SKB cb, adding that assertion somewhere.