linux-kernel - [PATCH 2/6] tpm: Get additional kref with every call to tpm_try_get

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Date:   Wed, 20 Jun 2018 12:19:44 -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 2/6] tpm: Get additional kref with every call to tpm_try_get_ops()

Get a reference to the TPM chip on every call to tpm_try_get_ops()
and release the reference in tpm_put_ops().

Signed-off-by: Stefan Berger <stefanb@...ux.vnet.ibm.com>
---
 drivers/char/tpm/tpm-chip.c | 5 ++++-
 include/linux/tpm.h         | 4 ++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index a933676194a4..23b667c730f6 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -58,6 +58,8 @@ int tpm_try_get_ops(struct tpm_chip *chip)
 	if (!chip->ops)
 		goto out_lock;
 
+	kref_get(&chip->kref);
+
 	return 0;
 out_lock:
 	up_read(&chip->ops_sem);
@@ -77,6 +79,7 @@ void tpm_put_ops(struct tpm_chip *chip)
 {
 	up_read(&chip->ops_sem);
 	put_device(&chip->dev);
+	tpm_chip_put(chip);
 }
 EXPORT_SYMBOL_GPL(tpm_put_ops);
 
@@ -129,7 +132,7 @@ static void tpm_chip_free(struct kref *kref)
 	kfree(chip);
 }
 
-static void tpm_chip_put(struct tpm_chip *chip)
+void tpm_chip_put(struct tpm_chip *chip)
 {
 	if (chip)
 		kref_put(&chip->kref, tpm_chip_free);
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index 06639fb6ab85..cdb3ecdfc933 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -61,6 +61,7 @@ extern int tpm_seal_trusted(struct tpm_chip *chip,
 extern int tpm_unseal_trusted(struct tpm_chip *chip,
 			      struct trusted_key_payload *payload,
 			      struct trusted_key_options *options);
+extern void tpm_chip_put(struct tpm_chip *chip);
 #else
 static inline int tpm_is_tpm2(struct tpm_chip *chip)
 {
@@ -96,5 +97,8 @@ static inline int tpm_unseal_trusted(struct tpm_chip *chip,
 {
 	return -ENODEV;
 }
+static inline void tpm_chip_put(struct tpm_chip *chip)
+{
+}
 #endif
 #endif
-- 
2.13.6