linux-kernel - [PATCH 1/6] tpm: Introduce a kref for the tpm

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Date:   Wed, 20 Jun 2018 12:19:43 -0400
From:   Stefan Berger <stefanb@...ux.vnet.ibm.com>
To:     linux-integrity@...r.kernel.org, jarkko.sakkinen@...ux.intel.com,
        zohar@...ux.vnet.ibm.com
Cc:     jgg@...pe.ca, linux-kernel@...r.kernel.org,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>
Subject: [PATCH 1/6] tpm: Introduce a kref for the tpm_chip

Introduce a kref for the tpm_chip that we initialize when the tpm_chip has
been allocated and release before the tpm_chip is to be freed.

Signed-off-by: Stefan Berger <stefanb@...ux.vnet.ibm.com>
---
 drivers/char/tpm/tpm-chip.c | 24 +++++++++++++++++++-----
 drivers/char/tpm/tpm.h      |  1 +
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 0a62c19937b6..a933676194a4 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -119,8 +119,24 @@ struct tpm_chip *tpm_chip_find_get(struct tpm_chip *chip)
 	return res;
 }
 
+static void tpm_chip_free(struct kref *kref)
+{
+	struct tpm_chip *chip = container_of(kref, struct tpm_chip, kref);
+
+	kfree(chip->log.bios_event_log);
+	kfree(chip->work_space.context_buf);
+	kfree(chip->work_space.session_buf);
+	kfree(chip);
+}
+
+static void tpm_chip_put(struct tpm_chip *chip)
+{
+	if (chip)
+		kref_put(&chip->kref, tpm_chip_free);
+}
+
 /**
- * tpm_dev_release() - free chip memory and the device number
+ * tpm_dev_release() - free the device number and release reference to chip
  * @dev: the character device for the TPM chip
  *
  * This is used as the release function for the character device.
@@ -133,10 +149,7 @@ static void tpm_dev_release(struct device *dev)
 	idr_remove(&dev_nums_idr, chip->dev_num);
 	mutex_unlock(&idr_lock);
 
-	kfree(chip->log.bios_event_log);
-	kfree(chip->work_space.context_buf);
-	kfree(chip->work_space.session_buf);
-	kfree(chip);
+	tpm_chip_put(chip);
 }
 
 static void tpm_devs_release(struct device *dev)
@@ -195,6 +208,7 @@ struct tpm_chip *tpm_chip_alloc(struct device *pdev,
 
 	mutex_init(&chip->tpm_mutex);
 	init_rwsem(&chip->ops_sem);
+	kref_init(&chip->kref);
 
 	chip->ops = ops;
 
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index 7f2d0f489e9c..098d7dcc04a4 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -211,6 +211,7 @@ struct tpm_chip {
 	struct cdev cdev;
 	struct cdev cdevs;
 
+	struct kref kref;
 	/* A driver callback under ops cannot be run unless ops_sem is held
 	 * (sometimes implicitly, eg for the sysfs code). ops becomes null
 	 * when the driver is unregistered, see tpm_try_get_ops.
-- 
2.13.6