On Thu, Dec 14, 2017 at 05:06:14PM +0100, Alexander Steffen wrote:
> When one of the commands during the auto_startup sequences does not return
> TPM_RC_SUCCESS, tpm_chip_register misleadingly returns ENODEV, even though
> a TPM device is definitely present.
>
> An error response during those sequences is indeed unexpected, so to
> prevent subsequent errors, the kernel should not make use of the TPM
> device. But user space applications still might be able to communicate with
> the TPM, so they can be used to further diagnose and/or fix the problem. To
> allow this, with this patch the device is still exported to user space,
> even if a TPM error code has been received, but the kernel itself will not
> be allowed to use the device for anything.
>
> This is not a hypothetical scenario, but there are devices in the wild that
> show this behavior. With this fix, those devices can be recovered from
> their failed state.
>
> Signed-off-by: Alexander Steffen <Alexander.Steffen@xxxxxxxxxxxx>
> drivers/char/tpm/tpm-chip.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 9cbe1ef..c4636e1 100644
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -384,7 +384,7 @@ static int tpm_add_legacy_sysfs(struct tpm_chip *chip)
> *
> * Creates a character device for the TPM chip and adds sysfs attributes for
> * the device. As the last step this function adds the chip to the list of TPM
> - * chips available for in-kernel use.
> + * chips available for in-kernel use, if the TPM startup was successful.
> *
> * This function should be only called after the chip initialization is
> * complete.
> @@ -392,6 +392,7 @@ static int tpm_add_legacy_sysfs(struct tpm_chip *chip)
> int tpm_chip_register(struct tpm_chip *chip)
> {
> int rc;
> + bool startup_successful = true;
>
> if (chip->ops->flags & TPM_OPS_AUTO_STARTUP) {
> if (chip->flags & TPM_CHIP_FLAG_TPM2)
> @@ -401,7 +402,7 @@ int tpm_chip_register(struct tpm_chip *chip)
> if (rc < 0)
> return rc;
> else if (rc > 0)
> - return -ENODEV;
> + startup_successful = false;
> }
The sysfs files probably shouldn't be created either in this case, and
the RM cdev should be disabled too.
Jsaon
