James Bottomley @ 2020-10-01 11:09 MST:
> The current release locality code seems to be based on the
> misunderstanding that the TPM interrupts when a locality is released:
> it doesn't, only when the locality is acquired.
>
> Furthermore, there seems to be no point in waiting for the locality to
> be released. All it does is penalize the last TPM user. However, if
> there's no next TPM user, this is a pointless wait and if there is a
> next TPM user, they'll pay the penalty waiting for the new locality
> (or possibly not if it's the same as the old locality).
>
> Fix the code by making release_locality as simple write to release
> with no waiting for completion.
>
> Fixes: 33bafe90824b ("tpm_tis: verify locality released before returning from release_locality")
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
>
> ---
>
> v2: added fixes
> ---
> drivers/char/tpm/tpm_tis_core.c | 47 +--------------------------------
> 1 file changed, 1 insertion(+), 46 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index f3ecde8df47d..431919d5f48a 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -135,58 +135,13 @@ static bool check_locality(struct tpm_chip *chip, int l)
> return false;
> }
>
> -static bool locality_inactive(struct tpm_chip *chip, int l)
> -{
> - struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> - int rc;
> - u8 access;
> -
> - rc = tpm_tis_read8(priv, TPM_ACCESS(l), &access);
> - if (rc < 0)
> - return false;
> -
> - if ((access & (TPM_ACCESS_VALID | TPM_ACCESS_ACTIVE_LOCALITY))
> - == TPM_ACCESS_VALID)
> - return true;
> -
> - return false;
> -}
> -
> static int release_locality(struct tpm_chip *chip, int l)
> {
> struct tpm_tis_data *priv = dev_get_drvdata(&chip->dev);
> - unsigned long stop, timeout;
> - long rc;
>
> tpm_tis_write8(priv, TPM_ACCESS(l), TPM_ACCESS_ACTIVE_LOCALITY);
>
> - stop = jiffies + chip->timeout_a;
> -
> - if (chip->flags & TPM_CHIP_FLAG_IRQ) {
> -again:
> - timeout = stop - jiffies;
> - if ((long)timeout <= 0)
> - return -1;
> -
> - rc = wait_event_interruptible_timeout(priv->int_queue,
> - (locality_inactive(chip, l)),
> - timeout);
> -
> - if (rc > 0)
> - return 0;
> -
> - if (rc == -ERESTARTSYS && freezing(current)) {
> - clear_thread_flag(TIF_SIGPENDING);
> - goto again;
> - }
> - } else {
> - do {
> - if (locality_inactive(chip, l))
> - return 0;
> - tpm_msleep(TPM_TIMEOUT);
> - } while (time_before(jiffies, stop));
> - }
> - return -1;
> + return 0;
> }
>
> static int request_locality(struct tpm_chip *chip, int l)
Reviewed-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
