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Date:	Tue, 22 Jul 2014 09:59:15 -0400
From:	Theodore Ts'o <>
To:	Andy Lutomirski <>
Cc:, "H. Peter Anvin" <>,, Kees Cook <>,, Daniel Borkmann <>,
	Srivatsa Vaddagiri <>,
	Raghavendra K T <>,
	Gleb Natapov <>,
	Paolo Bonzini <>,,
	Andrew Honig <>
Subject: Re: [PATCH v4 2/5] random: Add and use arch_get_rng_seed

On Thu, Jul 17, 2014 at 11:22:17AM -0700, Andy Lutomirski wrote:
> Currently, init_std_data contains its own logic for using arch
> random sources.  This logic is a bit strange: it reads one long of
> arch random data per byte of internal state.

This isn't true.  Check out the init_std_data() a bit more closely.

	unsigned long rv;


	for (i = r->poolinfo->poolbytes; i > 0; i -= sizeof(rv)) {

In particular, note the "i -= sizeof(rv)".  We are reading one bit per
bit of internal state beeing seeded.

> Assuming the arch sources are perfect, this is the right thing to
> do.  They're not, though, so the followup patch attempts to
> implement the correct logic on x86.

... and that's not a problem because we aren't giving any entropy
credit --- and this is deliberate, because we don't want to trust
un-auditable hardware.  We are deliberately trying to be conservative

So I don't think either this patch or the next one is needed.  It adds
far more complexity than is warranted.


						- Ted
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