linux-kernel - Re: [PATCH v8 08/10] tpm: Proxy driver for supporting multiple emulated TPMs

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Date:	Wed, 16 Mar 2016 22:37:50 +0200
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	Stefan Berger <stefanb@...ux.vnet.ibm.com>,
	tpmdd-devel@...ts.sourceforge.net,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	linux-api@...r.kernel.org, dhowells@...hat.com
Subject: Re: [PATCH v8 08/10] tpm: Proxy driver for supporting multiple
 emulated TPMs

On Wed, Mar 16, 2016 at 11:49:04AM -0600, Jason Gunthorpe wrote:
> On Wed, Mar 16, 2016 at 02:09:16PM +0200, Jarkko Sakkinen wrote:
> > On Sun, Mar 13, 2016 at 06:54:38PM -0400, Stefan Berger wrote:
> 
> > Alternative to this would be to have /dev/vtpmx create:
> > 
> > * /dev/vtpm0 for the server
> > * /dev/tpm0 for the client
> > 
> > This is how David Howell's PoC worked and that's why I want
> > to make this alternative visible.
> > 
> > The server could even respawn without container noticing it.
> > This solution have better availability properties.
> 
> Seriously, no, that doesn't make any sense. TPM is stateful, you can't
> respawn the server side.
> 
> If anyone is ever clever enough to make that workable then they just
> go ahead and save the server fd with the other state. systemd for
> instance already has everything needed to make that work.
> 
> We don't need to have a server dev node and we certainly don't need
> the leaking problem that leaves us with.

Fair enough.

> Jason

/Jarkko