| Message ID | CAHSjozDnf5Nm9Nw=kKBQRRYYmEozT-m=XN-bxwLbk8Rs+=pduA@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
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 <joshz@google.com> > Reviewed-by: Jarko Sakkinen <jarkko.sakkinen@linux.intel.com> > Cc: stable@vger.kernel.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
On Mon, May 29, 2017 at 10:07 PM, Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> wrote: > 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 <joshz@google.com> >> Reviewed-by: Jarko Sakkinen <jarkko.sakkinen@linux.intel.com> >> Cc: stable@vger.kernel.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. Done. >> + 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. I'm not sure quite what you mean here. Are you suggesting that tpm_del_char_device should unconditionally call the tpm_shutdown that this patch introduces? Or that the tpm2_shutdown function from drivers/char/tpm/tpm2-cmd.c (which right now just sends the TPM2_Shutdown command) be renamed to tpm_shutdown? >> + >> /** >> * 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. This is again in reference to https://patchwork.kernel.org/patch/9516631/; if at some point in the future a developer wishes to enable sysfs support for TPM2.0, the implicit locking must be fixed. I've attempted to clarify the phrasing here. Josh ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
On Tue, May 30, 2017 at 12:00:53PM -0700, Josh Zimmerman wrote: > On Mon, May 29, 2017 at 10:07 PM, Jarkko Sakkinen > <jarkko.sakkinen@linux.intel.com> wrote: > > 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 <joshz@google.com> > >> Reviewed-by: Jarko Sakkinen <jarkko.sakkinen@linux.intel.com> > >> Cc: stable@vger.kernel.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. > Done. > > >> + 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. > I'm not sure quite what you mean here. Are you suggesting that > tpm_del_char_device should unconditionally call the tpm_shutdown that > this patch introduces? Or that the tpm2_shutdown function from > drivers/char/tpm/tpm2-cmd.c (which right now just sends the > TPM2_Shutdown command) be renamed to tpm_shutdown? The second option. In addition can make that your patch set applies to security/next so I can merge both. I realized that the first patch does not apply so that needs a resend too. > >> + > >> /** > >> * 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. > This is again in reference to > https://patchwork.kernel.org/patch/9516631/; if at some point in the > future a developer wishes to enable sysfs support for TPM2.0, the > implicit locking must be fixed. > > I've attempted to clarify the phrasing here. > > Josh OK lets keep it! /Jarkko ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
On Wed, May 31, 2017 at 5:01 AM, Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> wrote: > On Tue, May 30, 2017 at 12:00:53PM -0700, Josh Zimmerman wrote: >> On Mon, May 29, 2017 at 10:07 PM, Jarkko Sakkinen >> <jarkko.sakkinen@linux.intel.com> wrote: >> > 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 <joshz@google.com> >> >> Reviewed-by: Jarko Sakkinen <jarkko.sakkinen@linux.intel.com> >> >> Cc: stable@vger.kernel.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. >> Done. >> >> >> + 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. >> I'm not sure quite what you mean here. Are you suggesting that >> tpm_del_char_device should unconditionally call the tpm_shutdown that >> this patch introduces? Or that the tpm2_shutdown function from >> drivers/char/tpm/tpm2-cmd.c (which right now just sends the >> TPM2_Shutdown command) be renamed to tpm_shutdown? > > The second option. I'm afraid I don't quite understand. I believe that tpm2_shutdown is currently quite specific to the TPM2 devices. It can also be called when preparing for hibernation, in which case we may not want to NULL out chip->ops. Can you please explain again what you'd like me to accomplish by making this change? > In addition can make that your patch set applies to > security/next so I can merge both. I realized that the first patch does > not apply so that needs a resend too. Replied in the other thread. This patch appears to apply cleanly on the branch I mentioned there. > >> >> + >> >> /** >> >> * 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. >> This is again in reference to >> https://patchwork.kernel.org/patch/9516631/; if at some point in the >> future a developer wishes to enable sysfs support for TPM2.0, the >> implicit locking must be fixed. >> >> I've attempted to clarify the phrasing here. >> >> Josh > > OK lets keep it! > > /Jarkko ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot
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;