linux-kernel - Re: [PATCH] tpm: fix crash in tpm

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Message-ID: <20160413061651.GA6986@intel.com>
Date:	Wed, 13 Apr 2016 09:16:51 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	Peter Huewe <peterhuewe@....de>,
	Marcel Selhorst <tpmdd@...horst.net>,
	"moderated list:TPM DEVICE DRIVER" 
	<tpmdd-devel@...ts.sourceforge.net>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: fix crash in tpm_tis deinitialization

On Tue, Apr 12, 2016 at 11:26:55AM -0600, Jason Gunthorpe wrote:
> On Tue, Apr 12, 2016 at 07:26:27AM +0300, Jarkko Sakkinen wrote:
> > > This needs to be after ops is fenced, something like this.
> > 
> > I would appreciate a supporting argument.
> > 
> > I guess the argument here is that this will prevent user space from
> > issuing TPM commands after the shutdown command has been sent?
> 
> It prevents everything including the kernel from issuing a command
                         ^^^^^^^^^^^^^^^^^^^^

That lock is not used to exclude kernel access. Read lock is only taken
for the user space device in tpm-dev.c.

> after shutdown. The shutdown is sent as the last command and no other
> commands can follow it.
> 
> It doesn't make any sense to allow commands to follow shutdown.

I agree with this.

> Jason

/Jarkko