linux-kernel - Re: [PATCH v2 1/2] hwrng: fetch randomness only after device init

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Date:	Mon, 7 Jul 2014 11:23:52 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Virtualization List <virtualization@...ts.linux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Jason Cooper <jason@...edaemon.net>,
	"# 3.4.x" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] hwrng: fetch randomness only after device init

On (Sun) 06 Jul 2014 [21:41:47], Kees Cook wrote:
> On Fri, Jul 4, 2014 at 10:34 PM, Amit Shah <amit.shah@...hat.com> wrote:
> > Commit d9e7972619334 "hwrng: add randomness to system from rng sources"
> > added a call to rng_get_data() from the hwrng_register() function.
> > However, some rng devices need initialization before data can be read
> > from them.
> >
> > This commit makes the call to rng_get_data() depend on no init fn
> > pointer being registered by the device.  If an init function is
> > registered, this call is made after device init.
> 
> Thanks, this seems pretty reasonable. One side-effect is that cycling
> between hwrngs via sysfs (when they have init functions) will cause
> them to add more entropy. I don't think this is a problem, but it is
> kind of a weird side-effect.

Yes, agreed.  Having a per-device bool that indicates whether the
initial randomness is obtained is quite a heavy solution for this
side-effect.  But I can put this in the commit log so it's clear..

> Reviewed-by: Kees Cook <keescook@...omium.org>

Thanks!

		Amit
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