linux-kernel - Re: [PATCH v3 2/5] random,x86: Add arch_get_slow_rng

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Date:	Thu, 17 Jul 2014 10:12:27 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"Theodore Ts'o" <tytso@....edu>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Paolo Bonzini <pbonzini@...hat.com>, X86 ML <x86@...nel.org>,
	Bandan Das <bsd@...hat.com>, Gleb Natapov <gleb@...nel.org>,
	kvm list <kvm@...r.kernel.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH v3 2/5] random,x86: Add arch_get_slow_rng_u64

On Thu, Jul 17, 2014 at 9:39 AM, H. Peter Anvin <hpa@...or.com> wrote:
> On 07/17/2014 03:33 AM, Theodore Ts'o wrote:
>> On Wed, Jul 16, 2014 at 09:55:15PM -0700, H. Peter Anvin wrote:
>>> On 07/16/2014 05:03 PM, Andy Lutomirski wrote:
>>>>>
>>>> I meant that prandom isn't using rdrand for early seeding.
>>>>
>>>
>>> We should probably fix that.
>>
>> It wouldn't hurt to explicitly use arch_get_random_long() in prandom,
>> but it does use get_random_bytes() in early seed, and for CPU's with
>> RDRAND present, we do use it in init_std_data() in
>> drivers/char/random.c, so prandom is already getting initialized via
>> an RNG (which is effectively a DRBG even if it doesn't pass all of
>> NIST's rules) which is derived from RDRAND.
>>
>
> I assumed he was referring to before alternatives.  Not sure if we use
> prandom before that point, though.

Unless I'm reading the code wrong, the prandom_reseed_late call can
happen after userspace is running.

Anyway, I'm working on a near-complete rewrite of the guest part of all of this.

--Andy

>
>         -hpa
>
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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