[PATCH 4.9 57/60] vTPM: Fix missing NULL check

Greg Kroah-Hartman
2017-06-19T15:30:54Z

From: Hon Ching \(Vicky\) Lo <honclo@linux.vnet.ibm.com>

commit 31574d321c70f6d3b40fe98f9b2eafd9a903fef9 upstream.

The current code passes the address of tpm_chip as the argument to
dev_get_drvdata() without prior NULL check in
tpm_ibmvtpm_get_desired_dma. This resulted an oops during kernel
boot when vTPM is enabled in Power partition configured in active
memory sharing mode.

The vio_driver's get_desired_dma() is called before the probe(), which
for vtpm is tpm_ibmvtpm_probe, and it's this latter function that
initializes the driver and set data. Attempting to get data before
the probe() caused the problem.

This patch adds a NULL check to the tpm_ibmvtpm_get_desired_dma.

fixes: 9e0d39d8a6a0 ("tpm: Remove useless priv field in struct tpm_vendor_specific")
Signed-off-by: Hon Ching(Vicky) Lo <honclo@linux.vnet.ibm.com>
Reviewed-by: Jarkko Sakkine <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/char/tpm/tpm_ibmvtpm.c | 17 +++++++++++------
1 file changed, 11 insertions(+), 6 deletions(-)

--- a/drivers/char/tpm/tpm_ibmvtpm.c
+++ b/drivers/char/tpm/tpm_ibmvtpm.c
@@ -295,6 +295,8 @@ static int tpm_ibmvtpm_remove(struct vio
}

kfree(ibmvtpm);
+ /* For tpm_ibmvtpm_get_desired_dma */
+ dev_set_drvdata(&vdev->dev, NULL);

return 0;
}
@@ -309,13 +311,16 @@ static int tpm_ibmvtpm_remove(struct vio
static unsigned long tpm_ibmvtpm_get_desired_dma(struct vio_dev *vdev)
{
struct tpm_chip *chip = dev_get_drvdata(&vdev->dev);
- struct ibmvtpm_dev *ibmvtpm = dev_get_drvdata(&chip->dev);
+ struct ibmvtpm_dev *ibmvtpm;

- /* ibmvtpm initializes at probe time, so the data we are
- * asking for may not be set yet. Estimate that 4K required
- * for TCE-mapped buffer in addition to CRQ.
- */
- if (!ibmvtpm)
+ /*
+ * ibmvtpm initializes at probe time, so the data we are
+ * asking for may not be set yet. Estimate that 4K required
+ * for TCE-mapped buffer in addition to CRQ.
+ */
+ if (chip)
+ ibmvtpm = dev_get_drvdata(&chip->dev);
+ else
return CRQ_RES_BUF_SIZE + PAGE_SIZE;

return CRQ_RES_BUF_SIZE + ibmvtpm->rtce_size;