linux-kernel - Re: [PATCH 1/2 v2] tpm: cmd_ready command can be issued only after granting locality

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Date:   Mon, 29 Jan 2018 10:57:20 -0700
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     "Winkler, Tomas" <tomas.winkler@...el.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        "Usyskin, Alexander" <alexander.usyskin@...el.com>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2 v2] tpm: cmd_ready command can be issued only after
 granting locality

On Sun, Jan 28, 2018 at 09:17:53PM +0000, Winkler, Tomas wrote:

> > I think if a driver can fail reliquish then it needs some kind of strategy to
> > recover.

> Maybe some driver can and some not, but if it doesn't succeed it
> should return an error.

But you can't just leave the driver in some inconsistent state..

Every time I've audited something to do with 'add error codes to
destroy/free/release' I find driver design issues..

> > Suggest trying the reliquish again on every next request until success,
> > otherwise fail request locality, potentially permanently.
> 
> This is something I rather prevent because it leaves the HW in kind of undefined state 
> ( and we should probably work on that a bit more later).
> As far as I've debugged the flow now, the driver just fails, and the error goes up 
> user space caller or the internal flow is stopped.

But tranmist_command will be called again - then what does the driver
do? The driver needs an answer for that..

If you don't want to retry then I'd rather see request_locality
permanently fail then adding a return code to release.

Jason