linux-kernel - [PATCH v2] vTPM: Fix missing NULL check

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Message-Id: <1489555687-27943-1-git-send-email-honclo@linux.vnet.ibm.com>
Date:   Wed, 15 Mar 2017 01:28:07 -0400
From:   "Hon Ching(Vicky) Lo" <honclo@...ux.vnet.ibm.com>
To:     tpmdd-devel@...ts.sourceforge.net
Cc:     Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <PeterHuewe@....de>,
        Ashley Lai <ashley@...leylai.com>,
        Vicky Lo <honclo2014@...il.com>, linux-kernel@...r.kernel.org,
        "Hon Ching(Vicky) Lo" <honclo@...ux.vnet.ibm.com>,
        <stable@...r.kernel.org>
Subject: [PATCH v2] vTPM: Fix missing NULL check

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")
Cc: <stable@...r.kernel.org>
Signed-off-by: Hon Ching(Vicky) Lo <honclo@...ux.vnet.ibm.com>
---
 drivers/char/tpm/tpm_ibmvtpm.c |    8 ++++++--
 1 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm_ibmvtpm.c b/drivers/char/tpm/tpm_ibmvtpm.c
index 1b9d61f..f01d083 100644
--- a/drivers/char/tpm/tpm_ibmvtpm.c
+++ b/drivers/char/tpm/tpm_ibmvtpm.c
@@ -299,6 +299,8 @@ 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;
 }
@@ -313,14 +315,16 @@ 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)
+	if (chip)
+		ibmvtpm = dev_get_drvdata(&chip->dev);
+	else
 		return CRQ_RES_BUF_SIZE + PAGE_SIZE;
 
 	return CRQ_RES_BUF_SIZE + ibmvtpm->rtce_size;
-- 
1.7.1