linux-kernel - Re: [PATCH v2] hex2bin: make the function hex_to

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Message-ID: <24c9a856-be10-e9b3-b26d-e6ced9e13c63@gmail.com>
Date:   Wed, 4 May 2022 11:47:52 +0200
From:   Milan Broz <gmazyland@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>,
        Mikulas Patocka <mpatocka@...hat.com>
Cc:     Stafford Horne <shorne@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Shevchenko <andy@...nel.org>,
        device-mapper development <dm-devel@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Mike Snitzer <msnitzer@...hat.com>,
        Mimi Zohar <zohar@...ux.ibm.com>, Jason@...c4.com
Subject: Re: [PATCH v2] hex2bin: make the function hex_to_bin constant-time

On 04/05/2022 11:20, Andy Shevchenko wrote:
> On Wed, May 04, 2022 at 04:57:35AM -0400, Mikulas Patocka wrote:
>> On Wed, 4 May 2022, Stafford Horne wrote:
>>> On Mon, Apr 25, 2022 at 08:07:48AM -0400, Mikulas Patocka wrote:
> 
> ...
> 
>>> Just a heads up it seems this patch is causing some instability with crypto self
>>> tests on OpenRISC when using a PREEMPT kernel (no SMP).
>>>
>>> This was reported by Jason A. Donenfeld as it came up in wireguard testing.
>>>
>>> I am trying to figure out if this is an OpenRISC PREEMPT issue or something
>>> else.
> 
>> That patch is so simple that I can't imagine how could it break the
>> curve25519 test. Are you sure that you bisected it correctly?
> 
> Can you provide a test cases for hex_to_bin()?

BTW we use exactly the same code from Mikulas in cryptsetup now (actually the report
was initiated from here :) and I added some tests for this code,
you can probably adapt it (we just use generic wrapper around it):

https://gitlab.com/cryptsetup/cryptsetup/-/commit/2d8cdb2e356d187658efa6efc7bfa146be5d3f60#d9c94cde02e4509f6d12c3edd40f8a9138696807_0_176

(it calls this: https://gitlab.com/cryptsetup/cryptsetup/-/commit/ff14c17de794fe85299d90e34e12a677e6148b71 )

I do not have OpenRISC available, but it would be interesting to run cryptsetup/tests/vectors-test there...

Milan