linux-kernel - Re: [PATCH] random: add and use memzero

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Message-ID: <20140827032143.GQ11317@thunk.org>
Date:	Tue, 26 Aug 2014 23:21:43 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	Daniel Borkmann <dborkman@...hat.com>, zatimend@...mail.co.uk,
	linux-kernel@...r.kernel.org, Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [PATCH] random: add and use memzero_explicit() for clearing data

On Tue, Aug 26, 2014 at 01:11:30AM +0200, Hannes Frederic Sowa wrote:
> On Mo, 2014-08-25 at 22:01 +0200, Daniel Borkmann wrote:
> > zatimend has reported that in his environment (3.16/gcc4.8.3/corei7)
> > memset() calls which clear out sensitive data in extract_{buf,entropy,
> > entropy_user}() in random driver are being optimized away by gcc.
> > 
> > Add a helper memzero_explicit() (similarly as explicit_bzero() variants)
> > that can be used in such cases where a variable with sensitive data is
> > being cleared out in the end. Other use cases might also be in crypto
> > code. [ I have put this into lib/string.c though, as it's always built-in
> > and doesn't need any dependencies then. ]
> > 
> > Fixes kernel bugzilla: 82041
> > 
> > Reported-by: zatimend@...mail.co.uk
> > Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
> > Cc: Hannes Frederic Sowa <hannes@...essinduktion.org>
> > Cc: Alexey Dobriyan <adobriyan@...il.com>
> 
> Acked-by: Hannes Frederic Sowa <hannes@...essinduktion.org>

Applied to the random tree, thanks.

					- Ted
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