linux-kernel - Re: [tpmdd-devel] [PATCH v2 4/7] tpm: infrastructure for TPM spaces

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Date:   Wed, 22 Mar 2017 16:09:21 -0400
From:   Ken Goldman <kgoldman@...ibm.com>
To:     tpmdd-devel@...ts.sourceforge.net
Cc:     linux-security-module@...r.kernel.org,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [tpmdd-devel] [PATCH v2 4/7] tpm: infrastructure for TPM spaces

On 2/22/2017 12:39 PM, James Bottomley wrote:
>
> Right at the moment the kernel use of tpm2 looks like
>
> acquire chip->tpm_mutex
> load key
> process key
> unload key
> release chip->tpm_mutex
>
> While it does this, there's no need for it to have a RM interface
> because what it does between the acquisition and drop of the mutex
> can't be seen by or have any effect on userspace (whether it uses the
> RM or not).  So currently, the question doesn't arise, which is the
> situation you see.

1 - This appears to depend on the RM not releasing the mutex until all 
objects are swapped out.  Correct?  Same for sessions?

2 - A startauthsession can cause a regap error.  Does the above depend 
on the RM doing early regapping so the RM won't see that error?

3 - There's also the problem where the TPM saved session slots 
(typically 64) are full.  My intuition is that the best solution is for 
the RM to reserve 3 slots for the kernel.