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Date:   Fri, 12 Feb 2021 13:02:03 +0200
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     Lino Sanfilippo <l.sanfilippo@kunbus.com>,
        James Bottomley <James.Bottomley@hansenpartnership.com>,
        Lino Sanfilippo <LinoSanfilippo@gmx.de>, peterhuewe@gmx.de,
        stefanb@linux.vnet.ibm.com, stable@vger.kernel.org,
        linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
        seanjc@google.com
Subject: Re: [PATCH v3 2/2] tpm: in tpm2_del_space check if ops pointer is
 still valid
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On Tue, Feb 09, 2021 at 09:36:53AM -0400, Jason Gunthorpe wrote:
> On Tue, Feb 09, 2021 at 12:52:17PM +0100, Lino Sanfilippo wrote:
> > > @@ -640,8 +643,10 @@ void tpm_chip_unregister(struct tpm_chip *chip)
> > >  	if (IS_ENABLED(CONFIG_HW_RANDOM_TPM))
> > >  		hwrng_unregister(&chip->hwrng);
> > >  	tpm_bios_log_teardown(chip);
> > > -	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> > > +	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> > >  		cdev_device_del(&chip->cdevs, &chip->devs);
> > > +		put_device(&chip->devs);
> > > +	}
> > >  	tpm_del_char_device(chip);
> > >  }
> > >  EXPORT_SYMBOL_GPL(tpm_chip_unregister);
> > > 
> > 
> > I tested the solution you scetched and it fixes the issue for me. Will you send a (real) patch for this?
> 
> No, feel free to bundle this up with any fixes needed and send it with
> a Signed-off-by from both of us
> 
> I did it pretty fast so it will need a careful read that there isn't a
> typo
> 
> Thanks,
> Jason

Let's use CDB too as it exist and Sean kindly provided a better
documentation for it in some recent kernel release. It's great
exactly for this type of situation.

/Jarkko