linux-kernel - Re: [PATCH] sha: prevent removal of memset as dead store in sha1

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Message-ID: <87sk8oqkil.fsf@basil.nowhere.org>
Date:	Fri, 26 Feb 2010 12:55:14 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	roel kluin <roel.kluin@...il.com>
Cc:	David Miller <davem@...emloft.net>, herbert@...dor.apana.org.au,
	mikpe@...uu.se, linux-crypto@...r.kernel.org,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sha: prevent removal of memset as dead store in  sha1_update()

roel kluin <roel.kluin@...il.com> writes:

>> And it's wrong because the reason the memset() is there seems to be
>> to clear out key information that might exist kernel stack so that
>> it's more difficult for rogue code to get at things.
>
> If the memset is optimized away then the clear out does not occur. Do you
> know a different way to fix this? I observed this with:

You could always cast to volatile before memsetting?

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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