On Sat Feb 24, 2024 at 4:34 AM EET, Lino Sanfilippo wrote:
>
>
> On 23.02.24 02:56, Daniel P. Smith wrote:
>
> >>
> >> Will the TPM TIS CORE ever (have to) request another locality than 0? Maybe the best would
> >> be to hardcode TPM_ACCESS(0) and get rid of all the locality parameters that are
> >> passed from one function to another.
> >> But this is rather code optimization and not really required to fix the reported bug.
> >
> > Actually, doing so will break the TPM API. The function
> > tpm_tis_request_locality() is registered as the locality handler,
> > int (*request_locality)(struct tpm_chip *chip, int loc), in the tis
> > instance of struct tpm_class_ops{}. This is the API used by the Secure
> > Launch series to open Locality2 for the measurements it must record.
> >
>
> I dont understand this. How do you use locality 2 with the current mainline
> API? Do you adjust the mainline code to use locality 2 instead of 0? This would
> at least explain how you ran into the underflow issue which from
> the source code seems to be impossible when using locality 0. But then I wonder why
> this has not been made clear in this discussion. And then we are talking
> about fixing a bug that does not even exist in the upstream code.
Thanks for bringing this up, now I finally figured out what confuses me
in this series.
Daniel, I also have troubles understanding why locality_count would ever
be greater than zero exactly in the mainline kernel, *without* [1]?
[1] https://lore.kernel.org/linux-integrity/20240214221847.2066632-1-ross.philipson@xxxxxxxxxx/
BR, Jarkko
