Re: Problem with the kernels trusted module on "inactive" TPM

[Mimi Zohar <zohar@linux.ibm.com>]

[Cc'ing Nayna]

On Thu, 2019-07-04 at 14:25 +0200, Roberto Sassu wrote:
> On 7/4/2019 12:42 PM, Jarkko Sakkinen wrote:
> > On Mon, 2019-07-01 at 17:22 +0300, Roberto Sassu wrote:
> >> Adding to the discussion Jarkko (the maintainer of the trusted key) and
> >> the linux-integrity mailing list.
> > 
> > I'm a co-maintainer (added James and Mimi).
> > 
> >>> some people (including me) have problems with the "trusted" kernel module.
> >>> As a result to this also the ecryptfs-module won't load.
> >>> (https://bugs.archlinux.org/task/62678)
> >>> If you use an "inactive" TPM module, the "trusted" module won't load
> >>> anymore.
> >>> The command modprobe just responds with "Bad address".
> >>> The strace-command shows that init_module fails with EFAULT.
> >>> I believe the reason for this is that the trusted-module handles
> >>> inactive modules the same as active modules.
> >>> This results in an error.
> >>>
> >>> For example:
> >>>
> > https://github.com/torvalds/linux/commit/0b6cf6b97b7ef1fa3c7fefab0cac897a1c4a3400#diff-c01228e6d386afb29df6aac17d9dd7abR1251
> >>>
> >>> My guess is that init_digests(); returns EFAULT in that case.
> >>> The " if (!chip)" check above probably needs to check if the chip is
> >>> "inactive".
> >>>
> >>> "inactive" = still visible to the system, but not functional.
> >>> It seems to be the default bios-setting for TPM on thinkpad.
> >>> (btw.: i have no clue why anybody would need something like that)
> >>>
> >>> Sadly i have no idea how you would check for an inactive chip,else i
> >>> would have send a patch instead.
> >>> But I hope the info i wrote is enough to get it fixed by somebody.
> >>
> >> Thanks for the report. If you see -EFAULT, tpm_get_random() is probably
> >> returning 0.
> >>
> >> Jarkko, we could consider it as non-critical error, and handle it as if
> >> the TPM is not found. What do you think?
> > 
> > Not sure I get this. Wasn't the issue fixed in c78719203fc6 or is there
> > something missing?
> 
> It seems it is not enough. A TPM is found but does not return data to
> tpm_get_random(), I think.

While working with Nayna (and George) on the "tpm: fixes uninitialized
allocated banks for IBM vtpm driver" patch, I wondered what happens if
the chip is enabled, but none of the banks were enabled.  Could this
be the "inactive" state?

Mimi