Re: TPM 2.0 RM flushcontext returning bad address

[James Bottomley <jejb-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>]

On Sat, 2017-01-14 at 13:19 -0500, Ken Goldman wrote:
> On 1/14/2017 11:45 AM, James Bottomley wrote:
> > 
> > Should fix all of this.  The code has to partially emulate
> > TPM2_FlushContext.  The emulation is
> > 
> >    1. If the handle type is not one we manage (transient, hmac or
> > policy)
> >       send the command on to the TPM
> >    2. next, if the handle isn't currently in the RM table,
> > manufacture a
> >       TPM_RC_HANDLE error and return it
> >    3. remove the handle from the RM table
> >    4. if the handle is transient, manufacture TPM_RC_SUCCESS and
> > return it
> >    5. otherwise it's a session handle: flush it and return success.
> 
> This sounds right, assuming:
> 
> 1 - The RM immediately context saves and then flushes any transient 
> object that's created or loaded onto the TPM.

Yes, that's how the space code operates.  It saves every handle (well,
every policy, hmac or transient handle) after a command completes and
reloads them all before the next one.

> If you want a list of commands that load transient objects, let me
> know.

I think for simplicity, unless there's a severe performance impact, we
should stick with loading and saving everything for every command
rather than trying to be selective about  whether the command might
actually use any saved contexts.

> 2 - Step 3 also implies deleting the saved context.

Yes, that's what I meant by "remove" the function in the patch is tpm2
-space.c:tpm2_forget_session() It removes both the handle and the saved
context information for the now flushed session.

James


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