Re: [PATCH v6 1/2] tpm: Issue a TPM2_Shutdown for TPM2 devices.

[Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

Hold on.

On Fri, 2017-06-16 at 10:25 -0700, Josh Zimmerman wrote:
> If a TPM2 loses power without a TPM2_Shutdown command being issued (a
> "disorderly reboot"), it may lose some state that has yet to be
> persisted to NVRam, and will increment the DA counter. After the DA
> counter gets sufficiently large, the TPM will lock the user out.
> 
> NOTE: This only changes behavior on TPM2 devices. Since TPM1 uses
sysfs,
> and sysfs relies on implicit locking on chip->ops, it is not safe to
> allow this code to run in TPM1, or to add sysfs support to TPM2,
until
> that locking is made explicit.
> 
> Signed-off-by: Josh Zimmerman <joshz@google.com>
> Cc: stable@vger.kernel.org
> 
> ----
> v2:
>   - Properly split changes between this and another commit
>   - Use proper locking primitive.
>   - Fix commenting style
> v3:
>   - Re-fix commenting style
> v4:
>   - Update description and tags (Reviewed-by, Cc).
> v5:
>   - Update documentation.
> v6:
>   - Call device and/or bus shutdown from tpm_shutdown.
> ---
>  drivers/char/tpm/tpm-chip.c  | 31 +++++++++++++++++++++++++++++++
>  drivers/char/tpm/tpm-sysfs.c |  3 +++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-
chip.c
> index 9dec9f551b83..62691d266f22 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -142,6 +142,36 @@ static void tpm_devs_release(struct device *dev)
>  	put_device(&chip->dev);
>  }
>  
> +/**
> + * tpm_shutdown() - prepare the TPM device for loss of power.
> + * @dev: device to which the chip is associated.
> + *
> + * Issues a TPM2_Shutdown command prior to loss of power, as
required by the
> + * TPM 2.0 spec.
> + *
> + * XXX: This codepath relies on the fact that sysfs is not enabled
for
> + * TPM2: sysfs uses an implicit lock on chip->ops, so this could
race if TPM2
> + * has sysfs support enabled before TPM sysfs's implicit locking is
fixed.
> + */
> +static void tpm_shutdown(struct device *dev)
> +{
> +	struct tpm_chip *chip = container_of(dev, struct tpm_chip,
dev);
> +
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> +		down_write(&chip->ops_sem);
> +		tpm2_shutdown(chip, TPM_SU_CLEAR);
> +		chip->ops = NULL;
> +		up_write(&chip->ops_sem);
> +	}
> +	// Allow bus- and device-specific code to run. Note: since
chip->ops
> +	// is NULL, more-specific shutdown code will not be able to
issue TPM
> +	// commands.
> +	if (dev->bus->shutdown)
> +		dev->bus->shutdown(dev);
> +	else if (dev->driver && dev->driver->shutdown)
> +		dev->driver->shutdown(dev);

WTF is this part.

And why we have now duplicate code??

I'm dropping these patches for now from my master branch. I don't
understand what is going on...

/Jarkko

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