linux-kernel - Re: [patch 1/4] Add routine for generating an ID for kernel pointer

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Message-ID: <20111228164522.GO17712@google.com>
Date:	Wed, 28 Dec 2011 08:45:22 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Pavel Emelyanov <xemul@...allels.com>,
	Glauber Costa <glommer@...allels.com>,
	Andi Kleen <andi@...stfloor.org>,
	Matt Helsley <matthltc@...ibm.com>,
	Pekka Enberg <penberg@...nel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Vasiliy Kulikov <segoon@...nwall.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [patch 1/4] Add routine for generating an ID for kernel pointer

Hello,

On Wed, Dec 28, 2011 at 08:40:55PM +0400, Cyrill Gorcunov wrote:
> > We have the whole crypto subsystem dealing with this.  It sure would
> > be more complex than ^ operator but it's not like you have to open
> > code the whole thing.  Is it really that complex to use?
> 
> No, Tejun, the use of crypto engine is not hard but it means more memory
> consumption (one need to carry resulting hashes and print them out into
> /proc) and more cpu consuption while we really need some fast and cheap
> solution. Unlike other usage of crypto engine (such as encoding for net
> layer, iirc ipsec uses it) I'm not really convinced we should use that
> heavy artillery here ;)

But the cost would be attributed to the user requesting that specific
data and given the amount of data to be hashed, I don't think the
computational or memory overhead should be the deciding design factor
here.  There are far more grave issues here.  Userland visible API and
security.

> I see, I could use some other form of output, it's not a problem. The main
> problem which interface community prefer, should I really switch to crypto
> usage or we can leave with root-only+plain-pointer approach?

I don't know either but if proper hashing (crypto or not) is simple
enough, this really isn't a tradeoff we need to make, no?

Thanks.

-- 
tejun
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