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

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Message-Id: <1405622543.23772.142820021.13876840@webmail.messagingengine.com>
Date:	Thu, 17 Jul 2014 20:42:23 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Andy Lutomirski <luto@...capital.net>,
	"Theodore Ts'o" <tytso@....edu>, "H. Peter Anvin" <hpa@...or.com>,
	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, 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 19:34, Andy Lutomirski wrote:
> On Thu, Jul 17, 2014 at 10:32 AM, Theodore Ts'o <tytso@....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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