[PATCH] tpm: fix crash in tpm_tis deinitialization

[PATCH] tpm: fix crash in tpm_tis deinitialization

[Jarkko Sakkinen]

rmmod crashes the driver because tpm_chip_unregister() already sets ops
to NULL. This commit fixes the issue by moving tpm2_shutdown() to
tpm_chip_unregister(). This commit is also cleanup because it removes
duplicate code from tpm_crb and tpm_tis to the core.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Fixes: 4d3eac5e156a ("tpm: Provide strong locking for device removal")
---
 drivers/char/tpm/tpm-chip.c | 3 +++
 drivers/char/tpm/tpm_crb.c  | 3 ---
 drivers/char/tpm/tpm_tis.c  | 3 ---
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index f62c851..2642cca 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -361,6 +361,9 @@ void tpm_chip_unregister(struct tpm_chip *chip)
 	if (!(chip->flags & TPM_CHIP_FLAG_REGISTERED))
 		return;
 
+	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		tpm2_shutdown(chip, TPM2_SU_CLEAR);
+
 	if (!(chip->flags & TPM_CHIP_FLAG_TPM2))
 		sysfs_remove_link(&chip->dev.parent->kobj, "ppi");
 
diff --git a/drivers/char/tpm/tpm_crb.c b/drivers/char/tpm/tpm_crb.c
index 20155d5..c31b5a7 100644
--- a/drivers/char/tpm/tpm_crb.c
+++ b/drivers/char/tpm/tpm_crb.c
@@ -341,9 +341,6 @@ static int crb_acpi_remove(struct acpi_device *device)
 	struct device *dev = &device->dev;
 	struct tpm_chip *chip = dev_get_drvdata(dev);
 
-	if (chip->flags & TPM_CHIP_FLAG_TPM2)
-		tpm2_shutdown(chip, TPM2_SU_CLEAR);
-
 	tpm_chip_unregister(chip);
 
 	return 0;
diff --git a/drivers/char/tpm/tpm_tis.c b/drivers/char/tpm/tpm_tis.c
index 1e45e73..a6b2d46 100644
--- a/drivers/char/tpm/tpm_tis.c
+++ b/drivers/char/tpm/tpm_tis.c
@@ -681,9 +681,6 @@ static void tpm_tis_remove(struct tpm_chip *chip)
 	struct priv_data *priv = dev_get_drvdata(&chip->dev);
 	void __iomem *reg = priv->iobase + TPM_INT_ENABLE(priv->locality);
 
-	if (chip->flags & TPM_CHIP_FLAG_TPM2)
-		tpm2_shutdown(chip, TPM2_SU_CLEAR);
-
 	iowrite32(~TPM_GLOBAL_INT_ENABLE & ioread32(reg), reg);
 	release_locality(chip, priv->locality, 1);
 }
-- 
2.7.4


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Re: [PATCH] tpm: fix crash in tpm_tis deinitialization

[Jason Gunthorpe]

On Mon, Apr 11, 2016 at 07:05:20PM +0300, Jarkko Sakkinen wrote:
> rmmod crashes the driver because tpm_chip_unregister() already sets ops
> to NULL. This commit fixes the issue by moving tpm2_shutdown() to
> tpm_chip_unregister(). This commit is also cleanup because it removes
> duplicate code from tpm_crb and tpm_tis to the core.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Fixes: 4d3eac5e156a ("tpm: Provide strong locking for device removal")
>  drivers/char/tpm/tpm-chip.c | 3 +++
>  drivers/char/tpm/tpm_crb.c  | 3 ---
>  drivers/char/tpm/tpm_tis.c  | 3 ---
>  3 files changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index f62c851..2642cca 100644
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -361,6 +361,9 @@ void tpm_chip_unregister(struct tpm_chip *chip)
>  	if (!(chip->flags & TPM_CHIP_FLAG_REGISTERED))
>  		return;
>  
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> +		tpm2_shutdown(chip, TPM2_SU_CLEAR);
> +
>  	if (!(chip->flags & TPM_CHIP_FLAG_TPM2))
>  		sysfs_remove_link(&chip->dev.parent->kobj, "ppi");

This needs to be after ops is fenced, something like this.

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 2642cca05cac..2ea2f1561e59 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -269,6 +269,8 @@ static void tpm_del_char_device(struct tpm_chip *chip)
 
 	/* Make the driver uncallable. */
 	down_write(&chip->ops_sem);
+	if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		tpm2_shutdown(chip, TPM2_SU_CLEAR);
 	chip->ops = NULL;
 	up_write(&chip->ops_sem);
 }
@@ -361,9 +363,6 @@ void tpm_chip_unregister(struct tpm_chip *chip)
 	if (!(chip->flags & TPM_CHIP_FLAG_REGISTERED))
 		return;
 
-	if (chip->flags & TPM_CHIP_FLAG_TPM2)
-		tpm2_shutdown(chip, TPM2_SU_CLEAR);
-
 	if (!(chip->flags & TPM_CHIP_FLAG_TPM2))
 		sysfs_remove_link(&chip->dev.parent->kobj, "ppi");
 

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Re: [PATCH] tpm: fix crash in tpm_tis deinitialization

[Jarkko Sakkinen]

On Mon, Apr 11, 2016 at 11:40:37AM -0600, Jason Gunthorpe wrote:
> On Mon, Apr 11, 2016 at 07:05:20PM +0300, Jarkko Sakkinen wrote:
> > rmmod crashes the driver because tpm_chip_unregister() already sets ops
> > to NULL. This commit fixes the issue by moving tpm2_shutdown() to
> > tpm_chip_unregister(). This commit is also cleanup because it removes
> > duplicate code from tpm_crb and tpm_tis to the core.
> > 
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> > Fixes: 4d3eac5e156a ("tpm: Provide strong locking for device removal")
> >  drivers/char/tpm/tpm-chip.c | 3 +++
> >  drivers/char/tpm/tpm_crb.c  | 3 ---
> >  drivers/char/tpm/tpm_tis.c  | 3 ---
> >  3 files changed, 3 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index f62c851..2642cca 100644
> > +++ b/drivers/char/tpm/tpm-chip.c
> > @@ -361,6 +361,9 @@ void tpm_chip_unregister(struct tpm_chip *chip)
> >  	if (!(chip->flags & TPM_CHIP_FLAG_REGISTERED))
> >  		return;
> >  
> > +	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> > +		tpm2_shutdown(chip, TPM2_SU_CLEAR);
> > +
> >  	if (!(chip->flags & TPM_CHIP_FLAG_TPM2))
> >  		sysfs_remove_link(&chip->dev.parent->kobj, "ppi");
> 
> This needs to be after ops is fenced, something like this.

I would appreciate a supporting argument.

I guess the argument here is that this will prevent user space from
issuing TPM commands after the shutdown command has been sent?

/Jarkko

> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 2642cca05cac..2ea2f1561e59 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -269,6 +269,8 @@ static void tpm_del_char_device(struct tpm_chip *chip)
>  
>  	/* Make the driver uncallable. */
>  	down_write(&chip->ops_sem);
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> +		tpm2_shutdown(chip, TPM2_SU_CLEAR);
>  	chip->ops = NULL;
>  	up_write(&chip->ops_sem);
>  }
> @@ -361,9 +363,6 @@ void tpm_chip_unregister(struct tpm_chip *chip)
>  	if (!(chip->flags & TPM_CHIP_FLAG_REGISTERED))
>  		return;
>  
> -	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> -		tpm2_shutdown(chip, TPM2_SU_CLEAR);
> -
>  	if (!(chip->flags & TPM_CHIP_FLAG_TPM2))
>  		sysfs_remove_link(&chip->dev.parent->kobj, "ppi");
>  

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Re: [PATCH] tpm: fix crash in tpm_tis deinitialization

[Jason Gunthorpe]

On Tue, Apr 12, 2016 at 07:26:27AM +0300, Jarkko Sakkinen wrote:
> > This needs to be after ops is fenced, something like this.
> 
> I would appreciate a supporting argument.
> 
> I guess the argument here is that this will prevent user space from
> issuing TPM commands after the shutdown command has been sent?

It prevents everything including the kernel from issuing a command
after shutdown. The shutdown is sent as the last command and no other
commands can follow it.

It doesn't make any sense to allow commands to follow shutdown.

Jason

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Re: [PATCH] tpm: fix crash in tpm_tis deinitialization

[Jarkko Sakkinen]

On Tue, Apr 12, 2016 at 11:26:55AM -0600, Jason Gunthorpe wrote:
> On Tue, Apr 12, 2016 at 07:26:27AM +0300, Jarkko Sakkinen wrote:
> > > This needs to be after ops is fenced, something like this.
> > 
> > I would appreciate a supporting argument.
> > 
> > I guess the argument here is that this will prevent user space from
> > issuing TPM commands after the shutdown command has been sent?
> 
> It prevents everything including the kernel from issuing a command
                         ^^^^^^^^^^^^^^^^^^^^

That lock is not used to exclude kernel access. Read lock is only taken
for the user space device in tpm-dev.c.

> after shutdown. The shutdown is sent as the last command and no other
> commands can follow it.
> 
> It doesn't make any sense to allow commands to follow shutdown.

I agree with this.

> Jason

/Jarkko

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Re: [PATCH] tpm: fix crash in tpm_tis deinitialization

[Jarkko Sakkinen]

On Wed, Apr 13, 2016 at 09:16:51AM +0300, Jarkko Sakkinen wrote:
> On Tue, Apr 12, 2016 at 11:26:55AM -0600, Jason Gunthorpe wrote:
> > On Tue, Apr 12, 2016 at 07:26:27AM +0300, Jarkko Sakkinen wrote:
> > > > This needs to be after ops is fenced, something like this.
> > > 
> > > I would appreciate a supporting argument.
> > > 
> > > I guess the argument here is that this will prevent user space from
> > > issuing TPM commands after the shutdown command has been sent?
> > 
> > It prevents everything including the kernel from issuing a command
>                          ^^^^^^^^^^^^^^^^^^^^
> 
> That lock is not used to exclude kernel access. Read lock is only taken
> for the user space device in tpm-dev.c.

My bad. For the in-kernel API it is taken through tpm_find_get().

I'll update the fix.

/Jarkko

Re: [PATCH] tpm: fix crash in tpm_tis deinitialization

[Jason Gunthorpe]

On Wed, Apr 13, 2016 at 09:58:05AM +0300, Jarkko Sakkinen wrote:
> > > It prevents everything including the kernel from issuing a command
> >                          ^^^^^^^^^^^^^^^^^^^^
> > 
> > That lock is not used to exclude kernel access. Read lock is only taken
> > for the user space device in tpm-dev.c.
> 
> My bad. For the in-kernel API it is taken through tpm_find_get().

Right. At this point any thing that can run in-kernel concurrently
with the write exclusion is a kernel bug. Those places will need to
grab the read side of the lock.

Jason

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