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From: Hannes Frederic Sowa <hannes@stressinduktion.org>
To: Andy Lutomirski <luto@amacapital.net>, "Theodore Ts'o" <tytso@mit.edu>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
        Paolo Bonzini <pbonzini@redhat.com>, X86 ML <x86@kernel.org>,
        Bandan Das <bsd@redhat.com>, Gleb Natapov <gleb@kernel.org>,
        kvm list <kvm@vger.kernel.org>,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
        Daniel Borkmann <dborkman@redhat.com>, linux-kernel@vger.kernel.org,
        Kees Cook <keescook@chromium.org>
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Subject: Re: [PATCH v3 2/5] random,x86: Add arch_get_slow_rng_u64
Date: Thu, 17 Jul 2014 20:42:23 +0200
Sender: linux-kernel-owner@vger.kernel.org


On Thu, Jul 17, 2014, at 19:34, Andy Lutomirski wrote:
> On Thu, Jul 17, 2014 at 10:32 AM, Theodore Ts'o <tytso@mit.edu> wrote:
> > On Thu, Jul 17, 2014 at 10:12:27AM -0700, Andy Lutomirski wrote:
> >>
> >> Unless I'm reading the code wrong, the prandom_reseed_late call can
> >> happen after userspace is running.
> >
> > But there is also the prandom_reseed() call, which happens early.
> >
> 
> Right -- I missed that.

prandom_init is a core_initcall, prandom_reseed is a late_initcall.
During initialization of the network stack we have calls to prandom_u32
before the late_initcall happens. That said, I think it is not that
important to seed prandom with rdseed/rdrand as security relevant
entropy extraction should always use get_random_bytes(), but we should
do it nonetheless.

Bye,
Hannes
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