linux-kernel - Re: [PATCH 4.19 33/63] tpm: Fix TPM 1.2 Shutdown sequence to prevent future TPM operations

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Date:   Tue, 1 Oct 2019 23:56:58 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Sasha Levin <sashal@...nel.org>
Cc:     Pavel Machek <pavel@....cz>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Vadim Sukhomlinov <sukhomlinov@...gle.com>,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH 4.19 33/63] tpm: Fix TPM 1.2 Shutdown sequence to prevent
 future TPM operations

On Mon, Sep 30, 2019 at 08:57:12AM -0400, Sasha Levin wrote:
> On Mon, Sep 30, 2019 at 08:13:46AM +0200, Pavel Machek wrote:
> > > From: Vadim Sukhomlinov <sukhomlinov@...gle.com>
> > > 
> > > commit db4d8cb9c9f2af71c4d087817160d866ed572cc9 upstream
> > > 
> > > TPM 2.0 Shutdown involve sending TPM2_Shutdown to TPM chip and disabling
> > > future TPM operations. TPM 1.2 behavior was different, future TPM
> > > operations weren't disabled, causing rare issues. This patch ensures
> > > that future TPM operations are disabled.
> > 
> > > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > > index 46caadca916a0..dccc61af9ffab 100644
> > > --- a/drivers/char/tpm/tpm-chip.c
> > > +++ b/drivers/char/tpm/tpm-chip.c
> > > @@ -187,12 +187,15 @@ static int tpm_class_shutdown(struct device *dev)
> > >  {
> > >  	struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
> > > 
> > > +	down_write(&chip->ops_sem);
> > >  	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> > >  		down_write(&chip->ops_sem);
> > >  		tpm2_shutdown(chip, TPM2_SU_CLEAR);
> > >  		chip->ops = NULL;
> > >  		up_write(&chip->ops_sem);
> > >  	}
> > > +	chip->ops = NULL;
> > > +	up_write(&chip->ops_sem);
> > 
> > This is wrong, it takes &chip->ops_sem twice, that can't be
> > good. db4d8cb9c9f2af71c4d087817160d866ed572cc9 does not have that
> > problem.
> 
> I agree. I've dropped it from 4.19 and 4.14.
> 
> Jarkko, can you take a look at this again please?

Pavel, thank you for spotting that one, phew!

I'll do an update.

/Jarkko