From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: [PATCH v4 1/2] tpm: Issue a TPM2_Shutdown for TPM2 devices. Date: Tue, 30 May 2017 08:07:01 +0300 Message-ID: <20170530050701.drf6geqplnfezllv@intel.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tpmdd-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: Josh Zimmerman Cc: tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, jmorris-gx6/JNMH7DfYtjvyW6yDsg@public.gmane.org List-Id: tpmdd-devel@lists.sourceforge.net On Thu, May 25, 2017 at 04:20:28PM -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. After the DA > counter gets sufficiently large, the TPM will 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. > > Signed-off-by: Josh Zimmerman > Reviewed-by: Jarko Sakkinen > Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Still have some remarks. > ---- > v2: > - Properly split changes between this and another commit > - Use proper locking primitive. > - Fix commenting style > v3: > - Re-fix commenting style > v4: > - Update description and tags (Reviewed-by, Cc). > --- > --- > 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. > + */ The comment should be either deleted or a kdoc. > + 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); > + } > +} Would be a better idea to rename tpm2_shutdown as tpm_shutdown and call it unconditionally in tpm_del_char_device. > + > /** > * 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. > + */ Not sure about this remark. Most, if not all, attributes in tpm-sysfs.c are useless attributes as you can use /dev/tpm0 to retrieve their values. > if (chip->flags & TPM_CHIP_FLAG_TPM2) > return; > > -- > 2.13.0.219.gdb65acc882-goog /Jarkko ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot