linux-kernel - Re: [PATCH v3 1/5] x86,kvm: Add MSR_KVM_GET_RNG

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Message-ID: <CALCETrW0gbWMujW0+cty7nzaNxvAeUpsFDFrhg1bFxBL_wrDcw@mail.gmail.com>
Date:	Thu, 17 Jul 2014 10:45:22 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Andrew Honig <ahonig@...gle.com>
Cc:	kvm <kvm@...r.kernel.org>, "H. Peter Anvin" <hpa@...or.com>,
	"Theodore Ts'o" <tytso@....edu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>, X86 ML <x86@...nel.org>,
	Daniel Borkmann <dborkman@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>,
	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Bandan Das <bsd@...hat.com>
Subject: Re: [PATCH v3 1/5] x86,kvm: Add MSR_KVM_GET_RNG_SEED and a matching
 feature bit

On Thu, Jul 17, 2014 at 10:43 AM, Andrew Honig <ahonig@...gle.com> wrote:
>> +       case MSR_KVM_GET_RNG_SEED:
>> +               get_random_bytes(&data, sizeof(data));
>> +               break;
>
> Should this be rate limited in the interest of conserving randomness?
> If there ever is an attack on the prng, this would create very
> favorable conditions for an attacker to exploit it.

IMO if the nonblocking pool has a weakness that requires us to
conserve its output, then this is the least of our worries.

--Andy
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