On Wed, Jul 28, 2021 at 12:57:30PM +0200, Borys Movchan wrote:
> If something went wrong during the TPM firmware upgrade,
> like power failure or the firmware image file get corrupted,
> the TPM might end up in Upgrade or Failure mode upon the
> next start. The state is persistent between the TPM power
> cycle/restart.
>
> According to TPM specification:
> * If the TPM is in Upgrade mode, it will answer with
> TPM2_RC_UPGRADE to all commands except Field Upgrade
> related ones.
> * If the TPM is in Failure mode, it will allow performing
> TPM initialization but will not provide any crypto
> operations. Will happily respond to Field Upgrade calls.
>
> The fix adds the possibility to detect an active state of
> the TPM and gives the user-space a chance to finish the
> firmware upgrade/recover the TPM.
This is different than telling what the patch does. It's just
describing a goal, but does not describe how the driver is
changed, and reasons for doing that.
For instance, you check 'limited_mode' flag in a few sites.
How can I know that those are exactly the locations where this
needs to be done?
> Signed-off-by: Borys Movchan <borysmn@xxxxxxxx>
> ---
>
> Notes:
> v2: The terms are changed to match the ones used in the TPM specification.
> Rework the commit message to provide more details regarding TPM
> behavior in Failure/Upgrade mode.
>
> The TPM specification describes TPM behavior in Upgrade mode very clearly.
> Things are a bit more complex if we are talking about Failure mode.
> The TPM behavior in this mode is highly vendor-specific. Although, there
> is one thing clearly described in the TPM specification and can be relied
> on to detect the Failure state: in Failure mode, the TPM doesn't provide
> any crypto operations. Including access to attributes and configuration
> registers.
> It seems persistent between different TPM manufacturers, at least to the
> degree I was able to verify.
>
> drivers/char/tpm/tpm-chip.c | 23 +++++++++++++++--------
> drivers/char/tpm/tpm2-cmd.c | 12 ++++++++++--
> include/linux/tpm.h | 1 +
> 3 files changed, 26 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index ddaeceb7e109..ff2367c447fb 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -574,20 +574,25 @@ static int tpm_get_pcr_allocation(struct tpm_chip *chip)
> int tpm_chip_register(struct tpm_chip *chip)
> {
> int rc;
> + bool limited_mode = false;
>
> rc = tpm_chip_start(chip);
> if (rc)
> return rc;
> rc = tpm_auto_startup(chip);
> - if (rc) {
> + if (rc == -EIO) {
> + limited_mode = true;
> + } else if (rc) {
> tpm_chip_stop(chip);
> return rc;
> }
>
> - rc = tpm_get_pcr_allocation(chip);
> - tpm_chip_stop(chip);
> - if (rc)
> - return rc;
> + if (!limited_mode) {
> + rc = tpm_get_pcr_allocation(chip);
> + tpm_chip_stop(chip);
> + if (rc)
> + return rc;
> + }
>
> tpm_sysfs_add_device(chip);
>
> @@ -595,9 +600,11 @@ int tpm_chip_register(struct tpm_chip *chip)
>
> tpm_add_ppi(chip);
>
> - rc = tpm_add_hwrng(chip);
> - if (rc)
> - goto out_ppi;
> + if (!limited_mode) {
> + rc = tpm_add_hwrng(chip);
> + if (rc)
> + goto out_ppi;
> + }
>
> rc = tpm_add_char_device(chip);
> if (rc)
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index a25815a6f625..7468353ed67d 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -718,7 +718,8 @@ static int tpm2_startup(struct tpm_chip *chip)
> * sequence
> * @chip: TPM chip to use
> *
> - * Returns 0 on success, < 0 in case of fatal error.
> + * Returns 0 on success, -ENODEV in case of fatal error,
> + * -EIO in case of Reduced/Upgrade mode
> */
> int tpm2_auto_startup(struct tpm_chip *chip)
> {
> @@ -729,7 +730,10 @@ int tpm2_auto_startup(struct tpm_chip *chip)
> goto out;
>
> rc = tpm2_do_selftest(chip);
> - if (rc && rc != TPM2_RC_INITIALIZE)
> + if (rc == TPM2_RC_UPGRADE) {
> + rc = -EIO;
> + goto out;
> + } else if (rc && rc != TPM2_RC_INITIALIZE)
> goto out;
>
> if (rc == TPM2_RC_INITIALIZE) {
> @@ -743,6 +747,10 @@ int tpm2_auto_startup(struct tpm_chip *chip)
> }
>
> rc = tpm2_get_cc_attrs_tbl(chip);
> + if (rc) { /* Succeeded until here, but failed -> reduced mode */
> + rc = -EIO;
> + goto out;
> + }
>
> out:
> if (rc > 0)
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index aa11fe323c56..e873c42907f0 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -207,6 +207,7 @@ enum tpm2_return_codes {
> TPM2_RC_INITIALIZE = 0x0100, /* RC_VER1 */
> TPM2_RC_FAILURE = 0x0101,
> TPM2_RC_DISABLED = 0x0120,
> + TPM2_RC_UPGRADE = 0x012D,
> TPM2_RC_COMMAND_CODE = 0x0143,
> TPM2_RC_TESTING = 0x090A, /* RC_WARN */
> TPM2_RC_REFERENCE_H0 = 0x0910,
> --
> 2.20.1
>
>
/Jarkko
