Re: [PATCH v3] tpm: Issue a TPM2_Shutdown for TPM2 devices.

[Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>]

Yes. Can you ping me once it is in? I can merge this after that.

/Jarkko

On Thu, May 18, 2017 at 08:21:32AM -0700, Josh Zimmerman wrote:
> Are there any other changes I should make to this patch, or is it good
> to go once the patch it depends on is in?
> 
> Thanks!
> Josh
> 
> 
> On Mon, May 15, 2017 at 5:08 PM, Josh Zimmerman <joshz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> wrote:
> > If a TPM2 loses power without a TPM2_Shutdown command being issued (a
> > "disorderly reboot"), it may lose some state that has yet to be
> > persisted to NVRam, and will increment the DA counter (eventually, this
> > will cause the TPM to lock the user out.)
> >
> > NOTE: This only changes behavior on TPM2 devices. Since TPM1 uses sysfs,
> > and sysfs relies on implicit locking on chip->ops, it is not safe to
> > allow this code to run in TPM1, or to add sysfs support to TPM2, until
> > that locking is made explicit.
> >
> > This patch is dependent on '[PATCH] Add "shutdown" to "struct class".'
> > http://marc.info/?l=linux-kernel&m=149463235025420&w=2
> >
> > Signed-off-by: Josh Zimmerman <joshz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
> >
> > ----
> > v2:
> >   - Properly split changes between this and another commit
> >   - Use proper locking primitive.
> >   - Fix commenting style
> > v3:
> >   - Re-fix commenting style
> > ---
> >  drivers/char/tpm/tpm-chip.c  | 20 ++++++++++++++++++++
> >  drivers/char/tpm/tpm-sysfs.c |  3 +++
> >  2 files changed, 23 insertions(+)
> >
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index 9dec9f551b83..272a42e77574 100644
> > --- a/drivers/char/tpm/tpm-chip.c
> > +++ b/drivers/char/tpm/tpm-chip.c
> > @@ -142,6 +142,25 @@ static void tpm_devs_release(struct device *dev)
> >         put_device(&chip->dev);
> >  }
> >
> > +static void tpm_shutdown(struct device *dev)
> > +{
> > +       struct tpm_chip *chip = container_of(dev, struct tpm_chip, dev);
> > +       /* TPM 2.0 requires that the TPM2_Shutdown() command be issued prior to
> > +        * loss of power. If it is not, the DA counter will be incremented and,
> > +        * eventually, the user will be locked out of their TPM.
> > +        * XXX: This codepath relies on the fact that sysfs is not enabled for
> > +        * TPM2: sysfs uses an implicit lock on chip->ops, so this use could
> > +        * race if TPM2 has sysfs support enabled before TPM sysfs's implicit
> > +        * locking is fixed.
> > +        */
> > +       if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> > +               down_write(&chip->ops_sem);
> > +               tpm2_shutdown(chip, TPM_SU_CLEAR);
> > +               chip->ops = NULL;
> > +               up_write(&chip->ops_sem);
> > +       }
> > +}
> > +
> >  /**
> >   * tpm_chip_alloc() - allocate a new struct tpm_chip instance
> >   * @pdev: device to which the chip is associated
> > @@ -181,6 +200,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
> >         device_initialize(&chip->devs);
> >
> >         chip->dev.class = tpm_class;
> > +       chip->dev.class.shutdown = tpm_shutdown;
> >         chip->dev.release = tpm_dev_release;
> >         chip->dev.parent = pdev;
> >         chip->dev.groups = chip->groups;
> > diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
> > index 55405dbe43fa..5e5ff7eb6f7e 100644
> > --- a/drivers/char/tpm/tpm-sysfs.c
> > +++ b/drivers/char/tpm/tpm-sysfs.c
> > @@ -294,6 +294,9 @@ static const struct attribute_group tpm_dev_group = {
> >
> >  void tpm_sysfs_add_device(struct tpm_chip *chip)
> >  {
> > +       /* XXX: Before this restriction is removed, tpm_sysfs must be updated
> > +        * to explicitly lock chip->ops.
> > +        */
> >         if (chip->flags & TPM_CHIP_FLAG_TPM2)
> >                 return;
> >
> > --
> > 2.13.0.303.g4ebf302169-goog
> >

------------------------------------------------------------------------------
Check out the vibrant tech community on one of the world's most
engaging tech sites, Slashdot.org! http://sdm.link/slashdot