vTPM: Fix missing NULL check

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>

diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
index 946025a..84eca4f 100644 (file)
--- 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_dev *vdev)
        }
 
        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_dev *vdev)
 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;