Patch "vTPM: Fix missing NULL check" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

vTPM: Fix missing NULL check

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
vtpm-fix-missing-null-check.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: "Hon Ching \\(Vicky\\) Lo" <[email protected]>
Date: Wed, 15 Mar 2017 01:28:07 -0400
Subject: vTPM: Fix missing NULL check

From: Hon Ching \(Vicky\) Lo <[email protected]>

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.

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

@@ -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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/vtpm-fix-missing-null-check.patch