tpm: Disable RNG for all AMD fTPMs

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commit 554b841d47 upstream.

The TPM RNG functionality is not necessary for entropy when the CPU
already supports the RDRAND instruction. The TPM RNG functionality
was previously disabled on a subset of AMD fTPM series, but reports
continue to show problems on some systems causing stutter root caused
to TPM RNG functionality.

Expand disabling TPM RNG use for all AMD fTPMs whether they have versions
that claim to have fixed or not. To accomplish this, move the detection
into part of the TPM CRB registration and add a flag indicating that
the TPM should opt-out of registration to hwrng.

Cc: stable@vger.kernel.org # 6.1.y+
Fixes: b006c439d5 ("hwrng: core - start hwrng kthread also for untrusted sources")
Fixes: f1324bbc40 ("tpm: disable hwrng for fTPM on some AMD designs")
Reported-by: daniil.stas@posteo.net
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217719
Reported-by: bitlord0xff@gmail.com
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217212
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

...

This commit is contained in:

Mario Limonciello 2023-08-02 07:25:33 -05:00 • committed by Greg Kroah-Hartman

parent ed2f8701fb

commit d8a7d6136c

3 changed files with 33 additions and 66 deletions

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68

drivers/char/tpm/tpm-chip.c

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30

drivers/char/tpm/tpm_crb.c

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1

include/linux/tpm.h

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