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

[Sasha Levin]

On Mon, Sep 30, 2019 at 08:13:46AM +0200, Pavel Machek wrote:
> > From: Vadim Sukhomlinov <sukhomlinov@xxxxxxxxxx>
> >
> > 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?

--
Thanks,
Sasha