On Mon, May 15, 2017 at 10:33:04AM -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 (eventually, this
> will cause the TPM to 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.
> 
> This patch is dependent on '[PATCH] Add "shutdown" to "struct class".'
> http://marc.info/?l=linux-kernel&m=149463235025420&w=2

Is this merged already? Who is going to merge it?

> Signed-off-by: Josh Zimmerman <jo...@google.com>

Otherwise,

Reviewed-by: Jarkko Sakkinen <jarkko.sakki...@linux.intel.com>

/Jarkko

> ----
> v2:
>   - Properly split changes between this and another commit
>   - Use proper locking primitive.
>   - Fix commenting style
> ---
>  drivers/char/tpm/tpm-chip.c  | 20 ++++++++++++++++++++
>  drivers/char/tpm/tpm-sysfs.c |  2 ++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 9dec9f551b83..e0c4323876b8 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -142,6 +142,25 @@ static void tpm_devs_release(struct device *dev)
>       put_device(&chip->dev);
>  }
>  
> +static void tpm_shutdown(struct device *dev)
> +{
> +     struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
> +     /** TPM 2.0 requires that the TPM2_Shutdown() command be issued prior to
> +      * loss of power. If it is not, the DA counter will be incremented and,
> +      * eventually, the user will be locked out of their TPM.
> +      * XXX: This codepath relies on the fact that sysfs is not enabled for
> +      * TPM2: sysfs uses an implicit lock on chip->ops, so this use could
> +      * race if TPM2 has sysfs support enabled before TPM sysfs's implicit
> +      * locking is fixed.
> +      */
> +     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);
> +     }
> +}
> +
>  /**
>   * tpm_chip_alloc() - allocate a new struct tpm_chip instance
>   * @pdev: device to which the chip is associated
> @@ -181,6 +200,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
>       device_initialize(&chip->devs);
>  
>       chip->dev.class = tpm_class;
> +     chip->dev.class.shutdown = tpm_shutdown;
>       chip->dev.release = tpm_dev_release;
>       chip->dev.parent = pdev;
>       chip->dev.groups = chip->groups;
> diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
> index 55405dbe43fa..6256f6e174b0 100644
> --- a/drivers/char/tpm/tpm-sysfs.c
> +++ b/drivers/char/tpm/tpm-sysfs.c
> @@ -294,6 +294,8 @@ static const struct attribute_group tpm_dev_group = {
>  
>  void tpm_sysfs_add_device(struct tpm_chip *chip)
>  {
> +     // XXX: Before this restriction is removed, tpm_sysfs must be updated
> +     // to explicitly lock chip->ops.
>       if (chip->flags & TPM_CHIP_FLAG_TPM2)
>               return;
>  
> -- 
> 2.13.0.rc2.291.g57267f2277-goog
> 

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