* [PATCH] tpm: fix crash in tpm_tis
@ 2016-04-07 12:56 Jarkko Sakkinen
[not found] ` <65cbfbc2-d994-452d-851c-102831ea0837@email.android.com>
0 siblings, 1 reply; 3+ messages in thread
From: Jarkko Sakkinen @ 2016-04-07 12:56 UTC (permalink / raw)
To: Peter Huewe
Cc: Jarkko Sakkinen, Marcel Selhorst, Jason Gunthorpe,
moderated list:TPM DEVICE DRIVER, open list
rmmod crashes the driver because tpm_chip_unregister() already sets ops
to NULL. Release ops in tpm_dev_release() so that tpm2_shutdown() can be
cleanly executed and also because it is symmetrical where they are
allocated (in tpmm_chip_alloc()).
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Fixes: 4d3eac5e156a ("tpm: Provide strong locking for device removal")
---
drivers/char/tpm/tpm-chip.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index f62c851..5241bc4 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -127,6 +127,11 @@ static void tpm_dev_release(struct device *dev)
idr_remove(&dev_nums_idr, chip->dev_num);
mutex_unlock(&idr_lock);
+ /* Make the driver uncallable. */
+ down_write(&chip->ops_sem);
+ chip->ops = NULL;
+ up_write(&chip->ops_sem);
+
kfree(chip);
}
@@ -266,11 +271,6 @@ static void tpm_del_char_device(struct tpm_chip *chip)
mutex_lock(&idr_lock);
idr_replace(&dev_nums_idr, NULL, chip->dev_num);
mutex_unlock(&idr_lock);
-
- /* Make the driver uncallable. */
- down_write(&chip->ops_sem);
- chip->ops = NULL;
- up_write(&chip->ops_sem);
}
static int tpm1_chip_register(struct tpm_chip *chip)
--
1.9.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] tpm: fix crash in tpm_tis
[not found] ` <65cbfbc2-d994-452d-851c-102831ea0837@email.android.com>
@ 2016-04-11 8:41 ` Jarkko Sakkinen
2016-04-11 11:18 ` Jarkko Sakkinen
0 siblings, 1 reply; 3+ messages in thread
From: Jarkko Sakkinen @ 2016-04-11 8:41 UTC (permalink / raw)
To: Jason Gunthorpe; +Cc: tpmdd-devel, Marcel Selhorst, linux-kernel, Peter Huewe
On Thu, Apr 07, 2016 at 07:36:54AM -0700, Jason Gunthorpe wrote:
> I will have to look closer after the conference, but this does not look
> right.
>
> I vaguely recall commenting on this before. Move the shutdown into the
> core code to fix it.
This fix that I sent is not the right way to do it.
One example scenario:
1. TIS driver gets detached, which causes tpm_tis_remove() to be called.
2. Some in-kernel subsystem uses TPM, which should not be done since the
hardware is already unitialized.
3. The devres subsystem sets ops to NULL.
Even though the fix is wrong I feel that it might put the rwsem into
question.
I'm just thinking that maybe there could be a release callback in
tpm_class_ops that could be called by tpm_del_char_device(). There can't
be clients for the chip at that point so no synchronization mechanism
is needed.
> Jason
/Jarkko
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] tpm: fix crash in tpm_tis
2016-04-11 8:41 ` Jarkko Sakkinen
@ 2016-04-11 11:18 ` Jarkko Sakkinen
0 siblings, 0 replies; 3+ messages in thread
From: Jarkko Sakkinen @ 2016-04-11 11:18 UTC (permalink / raw)
To: Jason Gunthorpe; +Cc: tpmdd-devel, Marcel Selhorst, linux-kernel, Peter Huewe
On Mon, Apr 11, 2016 at 11:41:24AM +0300, Jarkko Sakkinen wrote:
> On Thu, Apr 07, 2016 at 07:36:54AM -0700, Jason Gunthorpe wrote:
> > I will have to look closer after the conference, but this does not look
> > right.
> >
> > I vaguely recall commenting on this before. Move the shutdown into the
> > core code to fix it.
>
> This fix that I sent is not the right way to do it.
>
> One example scenario:
>
> 1. TIS driver gets detached, which causes tpm_tis_remove() to be called.
> 2. Some in-kernel subsystem uses TPM, which should not be done since the
> hardware is already unitialized.
> 3. The devres subsystem sets ops to NULL.
>
> Even though the fix is wrong I feel that it might put the rwsem into
> question.
>
> I'm just thinking that maybe there could be a release callback in
> tpm_class_ops that could be called by tpm_del_char_device(). There can't
> be clients for the chip at that point so no synchronization mechanism
> is needed.
As a fix for this regression moving shutdown to tmp_chip_unregister() does
make more sense since the patch is already merged to next. Lets not get
stuck into locking discussion...
/Jarkko
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-04-07 12:56 [PATCH] tpm: fix crash in tpm_tis Jarkko Sakkinen
[not found] ` <65cbfbc2-d994-452d-851c-102831ea0837@email.android.com>
2016-04-11 8:41 ` Jarkko Sakkinen
2016-04-11 11:18 ` Jarkko Sakkinen
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