linux-kernel - Re: [PATCH v3] tpm: Enable hwrng only for Pluton on AMD CPUs

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Message-Id: <446E94FC-C47A-453F-9A0E-CBE5049582ED@redhat.com>
Date:   Wed, 30 Aug 2023 11:25:45 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     Jarkko Sakkinen <jarkko@...nel.org>
Cc:     linux-integrity@...r.kernel.org, stable@...r.kernel.org,
        Todd Brandt <todd.e.brandt@...el.com>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Mario Limonciello <mario.limonciello@....com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] tpm: Enable hwrng only for Pluton on AMD CPUs



> On Aug 29, 2023, at 12:03 PM, Jerry Snitselaar <jsnitsel@...hat.com> wrote:
> 
> On Wed, Aug 23, 2023 at 02:15:10AM +0300, Jarkko Sakkinen wrote:
>> The vendor check introduced by commit 554b841d4703 ("tpm: Disable RNG for
>> all AMD fTPMs") doesn't work properly on a number of Intel fTPMs.  On the
>> reported systems the TPM doesn't reply at bootup and returns back the
>> command code. This makes the TPM fail probe.
>> 
>> Since only Microsoft Pluton is the only known combination of AMD CPU and
>> fTPM from other vendor, disable hwrng otherwise. In order to make sysadmin
>> aware of this, print also info message to the klog.
>> 
>> Cc: stable@...r.kernel.org
>> Fixes: 554b841d4703 ("tpm: Disable RNG for all AMD fTPMs")
>> Reported-by: Todd Brandt <todd.e.brandt@...el.com>
>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217804
>> Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
>> ---
>> v3:
>> * Forgot to amend config flags.
>> v2:
>> * CONFIG_X86
>> * Removed "Reviewed-by: Jarkko Sakkinen <jarkko@...nel.org>"
>> * Removed "Signed-off-by: Mario Limonciello <mario.limonciello@....com>"
>> ---
>> drivers/char/tpm/tpm_crb.c | 33 ++++++++-------------------------
>> 1 file changed, 8 insertions(+), 25 deletions(-)
>> 
> 
> Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>


It looks like the Fedora folks are getting more reports of the issue.