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References: <cover.1405546879.git.luto@amacapital.net> <3e019617640d1b07d0ab1c9a91455957c201d4cd.1405546879.git.luto@amacapital.net>
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From: Andy Lutomirski <luto@amacapital.net>
Date: Thu, 17 Jul 2014 10:45:22 -0700
Message-ID: <CALCETrW0gbWMujW0+cty7nzaNxvAeUpsFDFrhg1bFxBL_wrDcw@mail.gmail.com>
Subject: Re: [PATCH v3 1/5] x86,kvm: Add MSR_KVM_GET_RNG_SEED and a matching
 feature bit
To: Andrew Honig <ahonig@google.com>
Cc: kvm <kvm@vger.kernel.org>, "H. Peter Anvin" <hpa@zytor.com>,
        "Theodore Ts'o" <tytso@mit.edu>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Kees Cook <keescook@chromium.org>, X86 ML <x86@kernel.org>,
        Daniel Borkmann <dborkman@redhat.com>,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
        Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
        Gleb Natapov <gleb@kernel.org>, Paolo Bonzini <pbonzini@redhat.com>,
        Bandan Das <bsd@redhat.com>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org

On Thu, Jul 17, 2014 at 10:43 AM, Andrew Honig <ahonig@google.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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