linux-kernel - Re: [tpmdd-devel] [PATCH v2 2/7] tpm: two-phase chip management functions

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Date:	Thu, 9 Oct 2014 12:07:47 +0300
From:	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	Peter Huewe <peterhuewe@....de>, Ashley Lai <ashley@...leylai.com>,
	Marcel Selhorst <tpmdd@...horst.net>,
	linux-api@...r.kernel.org, tpmdd-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: [tpmdd-devel] [PATCH v2 2/7] tpm: two-phase chip management
 functions

On Tue, Oct 07, 2014 at 04:34:42PM -0600, Jason Gunthorpe wrote:
> On Wed, Oct 08, 2014 at 01:28:14AM +0300, Jarkko Sakkinen wrote:
> 
> > > > @@ -714,15 +709,10 @@ static int tpm_tis_i2c_remove(struct i2c_client *client)
> > > >  	struct tpm_chip *chip = tpm_dev.chip;
> > > >  	release_locality(chip, chip->vendor.locality, 1);
> > > >  
> > > > -	/* close file handles */
> > > > -	tpm_dev_vendor_release(chip);
> > > > -
> > > >  	/* remove hardware */
> > > >  	tpm_remove_hardware(chip->dev);
> > > 
> > > Wrong ordering here, tpm_remove_hardware should always be first -
> > > drivers should not tear down internal state before calling it, so
> > > release_locality should be second.
> > > 
> > > Noting that since we use devm the kfree will not happen until
> > > remove returns, so the chip pointer is still valid.
> > 
> > Should I fix this ordering? I was thinking to focus putting proper
> > patterns in place only in tpm_tis and tpm_crb because they are the
> > that I'm able to test easily and then they can work as guideline for
> > other drivers.
> 
> I think since this patch is already touching this function there is
> no reason not to make it be correct (especially since it was noticed)
> 
> The rest can wait till we globally replace tpm_remove_hardware with
> tpm_unregister - at that time the ordering can be audited and
> checked.
> 
> Then the drivers will be clean and the core can finally be fixed.

This makes sense. I'll also document this. And I decided to completely
wipe old tpm_register/remove_hardware() completely from v3 because they
only cause confusion.

I pushed patch that should implement fix for the ordering into tpm2-v2
branch:

https://github.com/jsakkine/linux-tpm2/commit/63ab650fa6f8dddd95100869e50275801d7d9360

> Jason

/Jarkko
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