linux-kernel - Re: [PATCH v3 1/3] crypto: hw_random

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Message-ID: <20170328174308.lwcogz2ae3bwnumr@kozik-lap>
Date:   Tue, 28 Mar 2017 20:43:08 +0300
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Stephan Müller <smueller@...onox.de>
Cc:     PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>,
        Kukjin Kim <kgene@...nel.org>,
        Javier Martinez Canillas <javier@....samsung.com>,
        Matt Mackall <mpm@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-crypto@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>
Subject: Re: [PATCH v3 1/3] crypto: hw_random - Add new Exynos RNG driver

On Tue, Mar 28, 2017 at 07:41:47PM +0200, Stephan Müller wrote:
> Am Dienstag, 28. März 2017, 18:48:24 CEST schrieb Krzysztof Kozlowski:
> 
> Hi Krzysztof,
> 
> > I tested a little bit and:
> > 1. Seeding with some value
> > 2. generating random,
> > 3. kcapi_rng_destroy+kcrng_init, (I cannot do a hardware reset except
> >    reboot of entire system)
> > 4. seeding with the same value as in (1) - different random numbers.
> > 
> > Doing a system reboot and repeating above - different random numbers
> > (all are different: step (2) and in (4)).
> > 
> > Your test case also produces different random values every time.
> 
> Then I would assume that simply adding an outer loop to your for() loop to 
> inject seed larger than the minimum required seed size should be fine.

Yes, makes sense. I'll send an updated version of patch.

Best regards,
Krzysztof