linux-kernel - Fwd: AMD Geode LX hardware RNG driver produces regular patterns (geode-rng.c)

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Message-ID: <9a28c2fc-d769-4802-a1f2-77ba2cb34d25@gmail.com>
Date:   Thu, 7 Sep 2023 18:37:00 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     Andres Salomon <dilinger@...ued.net>,
        "Timur I. Davletshin" <timur.davletshin@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Regressions <regressions@...ts.linux.dev>,
        Linux AMD GEODE <linux-geode@...ts.infradead.org>
Subject: Fwd: AMD Geode LX hardware RNG driver produces regular patterns
 (geode-rng.c)

Hi,

I notice a regression report on Bugzilla [1]. Quoting from it:

> System: Alix board 2d13 (AMD Geode LX800) running OpenWrt 23.05.0-rc3 (kernel 5.15.127)
> 
> Steps to reproduce:
> 
> cat /dev/hwrng and see output. Output in console shows regular pattern, rngd daemon (from rng-tools) refuses to run because of low entropy from /dev/hwrng. Pattern doesn't change until I reboot system.
> 
> Important notice: This problem started somewhere between 4.14.267 (kernel used in OpenWrt 19.07.9) and my current 5.15.127.
> 
> OpenWrt developers recommended addressing this problem upstream since they did not alter this driver in any way.

See Bugzilla for the full thread.

Anyway, I'm adding it to regzbot:

#regzbot ^introduced: v4.14.267..v5.15.127
#regzbot title: predictable urandom output on Alix 2d13

Thanks.

[1]: https://bugzilla.kernel.org/show_bug.cgi?id=217882

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