linux-kernel - Re: [PATCH 07/12] random: use the arch-specific rng in xfer_secondary

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Message-ID: <20120708014124.GA3809@thunk.org>
Date:	Sat, 7 Jul 2012 21:41:24 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Ben Hutchings <ben@...adent.org.uk>
Cc:	Linux Kernel Developers List <linux-kernel@...r.kernel.org>,
	ewust@...ch.edu, zakir@...ch.edu, nadiah@...ucsd.edu,
	jhalderm@...ch.edu, stable@...r.kernel.org
Subject: Re: [PATCH 07/12] random: use the arch-specific rng in
 xfer_secondary_pool

On Sun, Jul 08, 2012 at 02:06:46AM +0100, Ben Hutchings wrote:
> 
> Surely the number of random bytes being added is i * sizeof(long), not
> sizeof(u.hwrand)?
> 

Meh; Kees Cook has made the same observation.  Basically, in the
unlikely case where RDRAND fails, we'll end up mixing in stack
garbage.  It's not a security vulnerability, since the contents of the
entropy pool never gets exposed.  In fact, one could argue that mixing
in some unknown garbage from the kernel stack might actually help a
little; but it can't hurt.

					- Ted
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