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List:       linux-integrity
Subject:    Re: [PATCH v4] tpm: Trigger only missing TPM 2.0 self tests
From:       Jarkko Sakkinen <jarkko.sakkinen () linux ! intel ! com>
Date:       2018-02-21 7:31:32
Message-ID: 20180221073132.vrznvdp5oh7w6n53 () linux ! intel ! com
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On Wed, Feb 21, 2018 at 12:53:47AM +0200, Jarkko Sakkinen wrote:
> From: Alexander Steffen <Alexander.Steffen@infineon.com>
> 
> My Nuvoton 6xx in a Dell XPS-13 has been intermittently failing to work
> (necessitating a reboot). The problem seems to be that the TPM gets into a
> state where the partial self-test doesn't return TPM_RC_SUCCESS (meaning
> all tests have run to completion), but instead returns TPM_RC_TESTING
> (meaning some tests are still running in the background).  There are
> various theories that resending the self-test command actually causes the
> tests to restart and thus triggers more TPM_RC_TESTING returns until the
> timeout is exceeded.
> 
> There are several issues here: firstly being we shouldn't slow down the
> boot sequence waiting for the self test to complete once the TPM
> backgrounds them.  It will actually make available all functions that have
> passed and if it gets a failure return TPM_RC_FAILURE to every subsequent
> command.  So the fix is to kick off self tests once and if they return
> TPM_RC_TESTING log that as a backgrounded self test and continue on.  In
> order to prevent other tpm users from seeing any TPM_RC_TESTING returns
> (which it might if they send a command that needs a TPM subsystem which is
> still under test), we loop in tpm_transmit_cmd until either a timeout or we
> don't get a TPM_RC_TESTING return.
> 
> Finally, there have been observations of strange returns from a partial
> test. One Nuvoton is occasionally returning TPM_RC_COMMAND_CODE, so treat
> any unexpected return from a partial self test as an indication we need to
> run a full self test.
> 
> Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkine@linux.intel.com>
> Fixes: 2482b1bba5122b1d5516c909832bdd282015b8e9

Fixes tag is in wrong format. Should be 12 characters of the hash and
short summary in parentheses:

Fixes: 2482b1bba512 ("tpm: Trigger only missing TPM 2.0 self tests")

/Jarkko
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