From: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
To: Josh Zimmerman <joshz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Cc: Greg Kroah-Hartman
<gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>,
tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: Re: [PATCH v2] tpm: Issue a TPM2_Shutdown for TPM2 devices.
Date: Sat, 20 May 2017 15:44:50 +0300 [thread overview]
Message-ID: <20170520124450.lrmahcpeu2egxbtg@intel.com> (raw)
In-Reply-To: <20170515173304.12216-1-joshz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
On Mon, May 15, 2017 at 10:33:04AM -0700, Josh Zimmerman 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
Is this merged already? Who is going to merge it?
> Signed-off-by: Josh Zimmerman <joshz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
Otherwise,
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
/Jarkko
> ----
> v2:
> - Properly split changes between this and another commit
> - Use proper locking primitive.
> - Fix commenting style
> ---
> drivers/char/tpm/tpm-chip.c | 20 ++++++++++++++++++++
> drivers/char/tpm/tpm-sysfs.c | 2 ++
> 2 files changed, 22 insertions(+)
>
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 9dec9f551b83..e0c4323876b8 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..6256f6e174b0 100644
> --- a/drivers/char/tpm/tpm-sysfs.c
> +++ b/drivers/char/tpm/tpm-sysfs.c
> @@ -294,6 +294,8 @@ 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.rc2.291.g57267f2277-goog
>
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prev parent reply other threads:[~2017-05-20 12:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-15 17:33 [PATCH v2] tpm: Issue a TPM2_Shutdown for TPM2 devices Josh Zimmerman
[not found] ` <20170515173304.12216-1-joshz-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2017-05-15 17:40 ` Jason Gunthorpe
[not found] ` <20170515174053.GA6229-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>
2017-05-16 0:24 ` Josh Zimmerman
2017-05-20 12:44 ` Jarkko Sakkinen [this message]
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