[PATCH v2 0/5] Migrate all TPM 2.0 commands to use struct tpm_buf

[PATCH v2 0/5] Migrate all TPM 2.0 commands to use struct tpm_buf

[Jarkko Sakkinen]

v2:
* Fixed author information in the commit that fixes the self-test issue,
  removed '\n' from the log message and added the missing tested-by.
  (James: sincere apologies about this)
* Removed the redundant "out of memory" log message from tpm2_shutdown().
* tpm_buf_destroy() was called before using the response data in
  tpm2_probe().
* Added missing tpm_buf_destroy() to tpm2_get_random().

James Bottomley (1):
  tpm: fix intermittent failure with self tests

Jarkko Sakkinen (4):
  tpm: migrate tpm2_shutdown() to use struct tpm_buf
  tpm: migrate tpm2_probe() to use struct tpm_buf
  tpm: migrate tpm2_get_tpm_pt() to use struct tpm_buf
  tpm: migrate tpm2_get_random() to use struct tpm_buf

 drivers/char/tpm/tpm-interface.c |  20 ++-
 drivers/char/tpm/tpm.h           |  20 +--
 drivers/char/tpm/tpm2-cmd.c      | 281 ++++++++++++++-------------------------
 3 files changed, 128 insertions(+), 193 deletions(-)

-- 
2.15.1

[PATCH v2 1/5] tpm: fix intermittent failure with self tests

[Jarkko Sakkinen]

From: James Bottomley <James.Bottomley@HansenPartnership.com>

My Nuvoton 6xx in a Dell XPS-13 has been intermittently failing to work
(necessitating a reboot). The problem seems to be that the TPM gets into a
state where the partial self-test doesn't return TPM_RC_SUCCESS (meaning
all tests have run to completion), but instead returns TPM_RC_TESTING
(meaning some tests are still running in the background).  There are
various theories that resending the self-test command actually causes the
tests to restart and thus triggers more TPM_RC_TESTING returns until the
timeout is exceeded.

There are several issues here: firstly being we shouldn't slow down the
boot sequence waiting for the self test to complete once the TPM
backgrounds them.  It will actually make available all functions that have
passed and if it gets a failure return TPM_RC_FAILURE to every subsequent
command.  So the fix is to kick off self tests once and if they return
TPM_RC_TESTING log that as a backgrounded self test and continue on.  In
order to prevent other tpm users from seeing any TPM_RC_TESTING returns
(which it might if they send a command that needs a TPM subsystem which is
still under test), we loop in tpm_transmit_cmd until either a timeout or we
don't get a TPM_RC_TESTING return.

Finally, there have been observations of strange returns from a partial
test. One Nuvoton is occasionally returning TPM_RC_COMMAND_CODE, so treat
any unexpected return from a partial self test as an indication we need to
run a full self test.

[jarkko.sakkinen@linux.intel.com: cleaned up James' original commit and
 added a proper Fixes line]

Fixes: 2482b1bba5122 ("tpm: Trigger only missing TPM 2.0 self tests")
Cc: stable@vger.kernel.org
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkine@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkine@linux.intel.com>
---
 drivers/char/tpm/tpm-interface.c | 20 ++++++++++++---
 drivers/char/tpm/tpm.h           |  1 +
 drivers/char/tpm/tpm2-cmd.c      | 54 ++++++++++++----------------------------
 3 files changed, 33 insertions(+), 42 deletions(-)

diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 9e80a953d693..1adb976a2e37 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -537,14 +537,26 @@ ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_space *space,
 			 const char *desc)
 {
 	const struct tpm_output_header *header = buf;
+	unsigned int delay_msec = TPM2_DURATION_SHORT;
 	int err;
 	ssize_t len;
 
-	len = tpm_transmit(chip, space, (u8 *)buf, bufsiz, flags);
-	if (len <  0)
-		return len;
+	for (;;) {
+		len = tpm_transmit(chip, space, (u8 *)buf, bufsiz, flags);
+		if (len <  0)
+			return len;
+		err = be32_to_cpu(header->return_code);
+		if (err != TPM2_RC_TESTING)
+			break;
+
+		delay_msec *= 2;
+		if (delay_msec > TPM2_DURATION_LONG) {
+			dev_err(&chip->dev, "the self test is still running\n");
+			break;
+		}
+		tpm_msleep(delay_msec);
+	}
 
-	err = be32_to_cpu(header->return_code);
 	if (err != 0 && desc)
 		dev_err(&chip->dev, "A TPM error (%d) occurred %s\n", err,
 			desc);
diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index f895fba4e20d..cccd5994a0e1 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -104,6 +104,7 @@ enum tpm2_return_codes {
 	TPM2_RC_HASH		= 0x0083, /* RC_FMT1 */
 	TPM2_RC_HANDLE		= 0x008B,
 	TPM2_RC_INITIALIZE	= 0x0100, /* RC_VER1 */
+	TPM2_RC_FAILURE		= 0x0101,
 	TPM2_RC_DISABLED	= 0x0120,
 	TPM2_RC_COMMAND_CODE    = 0x0143,
 	TPM2_RC_TESTING		= 0x090A, /* RC_WARN */
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index a700f8f9ead7..89a5397b18d2 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -31,10 +31,6 @@ struct tpm2_startup_in {
 	__be16	startup_type;
 } __packed;
 
-struct tpm2_self_test_in {
-	u8	full_test;
-} __packed;
-
 struct tpm2_get_tpm_pt_in {
 	__be32	cap_id;
 	__be32	property_id;
@@ -60,7 +56,6 @@ struct tpm2_get_random_out {
 
 union tpm2_cmd_params {
 	struct	tpm2_startup_in		startup_in;
-	struct	tpm2_self_test_in	selftest_in;
 	struct	tpm2_get_tpm_pt_in	get_tpm_pt_in;
 	struct	tpm2_get_tpm_pt_out	get_tpm_pt_out;
 	struct	tpm2_get_random_in	getrandom_in;
@@ -827,16 +822,6 @@ unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal)
 }
 EXPORT_SYMBOL_GPL(tpm2_calc_ordinal_duration);
 
-#define TPM2_SELF_TEST_IN_SIZE \
-	(sizeof(struct tpm_input_header) + \
-	 sizeof(struct tpm2_self_test_in))
-
-static const struct tpm_input_header tpm2_selftest_header = {
-	.tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
-	.length = cpu_to_be32(TPM2_SELF_TEST_IN_SIZE),
-	.ordinal = cpu_to_be32(TPM2_CC_SELF_TEST)
-};
-
 /**
  * tpm2_do_selftest() - ensure that all self tests have passed
  *
@@ -852,27 +837,24 @@ static const struct tpm_input_header tpm2_selftest_header = {
  */
 static int tpm2_do_selftest(struct tpm_chip *chip)
 {
+	struct tpm_buf buf;
+	int full;
 	int rc;
-	unsigned int delay_msec = 10;
-	long duration;
-	struct tpm2_cmd cmd;
 
-	duration = jiffies_to_msecs(
-		tpm2_calc_ordinal_duration(chip, TPM2_CC_SELF_TEST));
-
-	while (1) {
-		cmd.header.in = tpm2_selftest_header;
-		cmd.params.selftest_in.full_test = 0;
-
-		rc = tpm_transmit_cmd(chip, NULL, &cmd, TPM2_SELF_TEST_IN_SIZE,
-				      0, 0, "continue selftest");
+	for (full = 0; full < 2; full++) {
+		rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SELF_TEST);
+		if (rc)
+			return rc;
 
-		if (rc != TPM2_RC_TESTING || delay_msec >= duration)
-			break;
+		tpm_buf_append_u8(&buf, full);
+		rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE, 0, 0,
+				      "attempting the self test");
+		tpm_buf_destroy(&buf);
 
-		/* wait longer than before */
-		delay_msec *= 2;
-		tpm_msleep(delay_msec);
+		if (rc == TPM2_RC_TESTING)
+			rc = TPM2_RC_SUCCESS;
+		if (rc == TPM2_RC_INITIALIZE || rc == TPM2_RC_SUCCESS)
+			return rc;
 	}
 
 	return rc;
@@ -1058,10 +1040,8 @@ int tpm2_auto_startup(struct tpm_chip *chip)
 		goto out;
 
 	rc = tpm2_do_selftest(chip);
-	if (rc != 0 && rc != TPM2_RC_INITIALIZE) {
-		dev_err(&chip->dev, "TPM self test failed\n");
+	if (rc && rc != TPM2_RC_INITIALIZE)
 		goto out;
-	}
 
 	if (rc == TPM2_RC_INITIALIZE) {
 		rc = tpm_startup(chip);
@@ -1069,10 +1049,8 @@ int tpm2_auto_startup(struct tpm_chip *chip)
 			goto out;
 
 		rc = tpm2_do_selftest(chip);
-		if (rc) {
-			dev_err(&chip->dev, "TPM self test failed\n");
+		if (rc)
 			goto out;
-		}
 	}
 
 	rc = tpm2_get_pcr_allocation(chip);
-- 
2.15.1

[PATCH v2 2/5] tpm: migrate tpm2_shutdown() to use struct tpm_buf

[Jarkko Sakkinen]

In order to make struct tpm_buf the first class object for constructing TPM
commands, migrate tpm2_shutdown() to use it. In addition, removed the klog
entry when tpm_transmit_cmd() fails because tpm_tansmit_cmd() already
prints an error message.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 drivers/char/tpm/tpm2-cmd.c | 44 ++++++++++++--------------------------------
 1 file changed, 12 insertions(+), 32 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 89a5397b18d2..abe6ef4a7a0b 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -27,10 +27,6 @@ enum tpm2_session_attributes {
 	TPM2_SA_CONTINUE_SESSION	= BIT(0),
 };
 
-struct tpm2_startup_in {
-	__be16	startup_type;
-} __packed;
-
 struct tpm2_get_tpm_pt_in {
 	__be32	cap_id;
 	__be32	property_id;
@@ -55,7 +51,6 @@ struct tpm2_get_random_out {
 } __packed;
 
 union tpm2_cmd_params {
-	struct	tpm2_startup_in		startup_in;
 	struct	tpm2_get_tpm_pt_in	get_tpm_pt_in;
 	struct	tpm2_get_tpm_pt_out	get_tpm_pt_out;
 	struct	tpm2_get_random_in	getrandom_in;
@@ -410,11 +405,8 @@ void tpm2_flush_context_cmd(struct tpm_chip *chip, u32 handle,
 	int rc;
 
 	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_FLUSH_CONTEXT);
-	if (rc) {
-		dev_warn(&chip->dev, "0x%08x was not flushed, out of memory\n",
-			 handle);
+	if (rc)
 		return;
-	}
 
 	tpm_buf_append_u32(&buf, handle);
 
@@ -760,40 +752,28 @@ ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,  u32 *value,
 }
 EXPORT_SYMBOL_GPL(tpm2_get_tpm_pt);
 
-#define TPM2_SHUTDOWN_IN_SIZE \
-	(sizeof(struct tpm_input_header) + \
-	 sizeof(struct tpm2_startup_in))
-
-static const struct tpm_input_header tpm2_shutdown_header = {
-	.tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
-	.length = cpu_to_be32(TPM2_SHUTDOWN_IN_SIZE),
-	.ordinal = cpu_to_be32(TPM2_CC_SHUTDOWN)
-};
-
 /**
  * tpm2_shutdown() - send shutdown command to the TPM chip
  *
+ * In places where shutdown command is sent there's no much we can do except
+ * print the error code on a system failure.
+ *
  * @chip:		TPM chip to use.
  * @shutdown_type:	shutdown type. The value is either
  *			TPM_SU_CLEAR or TPM_SU_STATE.
  */
 void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type)
 {
-	struct tpm2_cmd cmd;
+	struct tpm_buf buf;
 	int rc;
 
-	cmd.header.in = tpm2_shutdown_header;
-	cmd.params.startup_in.startup_type = cpu_to_be16(shutdown_type);
-
-	rc = tpm_transmit_cmd(chip, NULL, &cmd, sizeof(cmd), 0, 0,
-			      "stopping the TPM");
-
-	/* In places where shutdown command is sent there's no much we can do
-	 * except print the error code on a system failure.
-	 */
-	if (rc < 0 && rc != -EPIPE)
-		dev_warn(&chip->dev, "transmit returned %d while stopping the TPM",
-			 rc);
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SHUTDOWN);
+	if (rc)
+		return;
+	tpm_buf_append_u16(&buf, shutdown_type);
+	tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE, 0, 0,
+			 "stopping the TPM");
+	tpm_buf_destroy(&buf);
 }
 
 /*
-- 
2.15.1

[PATCH v2 3/5] tpm: migrate tpm2_probe() to use struct tpm_buf

[Jarkko Sakkinen]

In order to make struct tpm_buf the first class object for constructing TPM
commands, migrate tpm2_probe() to use it.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 drivers/char/tpm/tpm2-cmd.c | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index abe6ef4a7a0b..890d83c5c78b 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -851,22 +851,25 @@ static int tpm2_do_selftest(struct tpm_chip *chip)
  */
 int tpm2_probe(struct tpm_chip *chip)
 {
-	struct tpm2_cmd cmd;
+	struct tpm_output_header *out;
+	struct tpm_buf buf;
 	int rc;
 
-	cmd.header.in = tpm2_get_tpm_pt_header;
-	cmd.params.get_tpm_pt_in.cap_id = cpu_to_be32(TPM2_CAP_TPM_PROPERTIES);
-	cmd.params.get_tpm_pt_in.property_id = cpu_to_be32(0x100);
-	cmd.params.get_tpm_pt_in.property_cnt = cpu_to_be32(1);
-
-	rc = tpm_transmit_cmd(chip, NULL, &cmd, sizeof(cmd), 0, 0, NULL);
-	if (rc <  0)
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
+	if (rc)
 		return rc;
-
-	if (be16_to_cpu(cmd.header.out.tag) == TPM2_ST_NO_SESSIONS)
+	tpm_buf_append_u32(&buf, TPM2_CAP_TPM_PROPERTIES);
+	tpm_buf_append_u32(&buf, TPM_PT_TOTAL_COMMANDS);
+	tpm_buf_append_u32(&buf, 1);
+	rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE, 0, 0, NULL);
+	if (rc <  0)
+		goto out;
+	out = (struct tpm_output_header *)buf.data;
+	if (be16_to_cpu(out->tag) == TPM2_ST_NO_SESSIONS)
 		chip->flags |= TPM_CHIP_FLAG_TPM2;
-
-	return 0;
+out:
+	tpm_buf_destroy(&buf);
+	return rc;
 }
 EXPORT_SYMBOL_GPL(tpm2_probe);
 
-- 
2.15.1

[PATCH v2 4/5] tpm: migrate tpm2_get_tpm_pt() to use struct tpm_buf

[Jarkko Sakkinen]

In order to make struct tpm_buf the first class object for constructing TPM
commands, migrate tpm2_get_tpm_pt() to use it.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 drivers/char/tpm/tpm2-cmd.c | 63 +++++++++++++++++----------------------------
 1 file changed, 23 insertions(+), 40 deletions(-)

diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 890d83c5c78b..e02f7d46e9ac 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -27,20 +27,6 @@ enum tpm2_session_attributes {
 	TPM2_SA_CONTINUE_SESSION	= BIT(0),
 };
 
-struct tpm2_get_tpm_pt_in {
-	__be32	cap_id;
-	__be32	property_id;
-	__be32	property_cnt;
-} __packed;
-
-struct tpm2_get_tpm_pt_out {
-	u8	more_data;
-	__be32	subcap_id;
-	__be32	property_cnt;
-	__be32	property_id;
-	__be32	value;
-} __packed;
-
 struct tpm2_get_random_in {
 	__be16	size;
 } __packed;
@@ -51,8 +37,6 @@ struct tpm2_get_random_out {
 } __packed;
 
 union tpm2_cmd_params {
-	struct	tpm2_get_tpm_pt_in	get_tpm_pt_in;
-	struct	tpm2_get_tpm_pt_out	get_tpm_pt_out;
 	struct	tpm2_get_random_in	getrandom_in;
 	struct	tpm2_get_random_out	getrandom_out;
 };
@@ -377,19 +361,6 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max)
 	return total ? total : -EIO;
 }
 
-#define TPM2_GET_TPM_PT_IN_SIZE \
-	(sizeof(struct tpm_input_header) + \
-	 sizeof(struct tpm2_get_tpm_pt_in))
-
-#define TPM2_GET_TPM_PT_OUT_BODY_SIZE \
-	 sizeof(struct tpm2_get_tpm_pt_out)
-
-static const struct tpm_input_header tpm2_get_tpm_pt_header = {
-	.tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
-	.length = cpu_to_be32(TPM2_GET_TPM_PT_IN_SIZE),
-	.ordinal = cpu_to_be32(TPM2_CC_GET_CAPABILITY)
-};
-
 /**
  * tpm2_flush_context_cmd() - execute a TPM2_FlushContext command
  * @chip: TPM chip to use
@@ -723,6 +694,14 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
 	return rc;
 }
 
+struct tpm2_get_cap_out {
+	u8 more_data;
+	__be32 subcap_id;
+	__be32 property_cnt;
+	__be32 property_id;
+	__be32 value;
+} __packed;
+
 /**
  * tpm2_get_tpm_pt() - get value of a TPM_CAP_TPM_PROPERTIES type property
  * @chip:		TPM chip to use.
@@ -735,19 +714,23 @@ int tpm2_unseal_trusted(struct tpm_chip *chip,
 ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,  u32 *value,
 			const char *desc)
 {
-	struct tpm2_cmd cmd;
+	struct tpm2_get_cap_out *out;
+	struct tpm_buf buf;
 	int rc;
 
-	cmd.header.in = tpm2_get_tpm_pt_header;
-	cmd.params.get_tpm_pt_in.cap_id = cpu_to_be32(TPM2_CAP_TPM_PROPERTIES);
-	cmd.params.get_tpm_pt_in.property_id = cpu_to_be32(property_id);
-	cmd.params.get_tpm_pt_in.property_cnt = cpu_to_be32(1);
-
-	rc = tpm_transmit_cmd(chip, NULL, &cmd, sizeof(cmd),
-			      TPM2_GET_TPM_PT_OUT_BODY_SIZE, 0, desc);
-	if (!rc)
-		*value = be32_to_cpu(cmd.params.get_tpm_pt_out.value);
-
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
+	if (rc)
+		return rc;
+	tpm_buf_append_u32(&buf, TPM2_CAP_TPM_PROPERTIES);
+	tpm_buf_append_u32(&buf, property_id);
+	tpm_buf_append_u32(&buf, 1);
+	rc = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE, 0, 0, NULL);
+	if (!rc) {
+		out = (struct tpm2_get_cap_out *)
+			&buf.data[TPM_HEADER_SIZE];
+		*value = be32_to_cpu(out->value);
+	}
+	tpm_buf_destroy(&buf);
 	return rc;
 }
 EXPORT_SYMBOL_GPL(tpm2_get_tpm_pt);
-- 
2.15.1

[PATCH v2 5/5] tpm: migrate tpm2_get_random() to use struct tpm_buf

[Jarkko Sakkinen]

In order to make struct tpm_buf the first class object for constructing
TPM commands, migrate tpm2_get_random() to use it. In addition, removed
remaining references to struct tpm2_cmd. All of them use it to acquire
the length of the response, which can be achieved by using
tpm_buf_length().

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
---
 drivers/char/tpm/tpm.h      | 19 ++++-----
 drivers/char/tpm/tpm2-cmd.c | 93 +++++++++++++++++----------------------------
 2 files changed, 45 insertions(+), 67 deletions(-)

diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index cccd5994a0e1..29c0717437bc 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -412,23 +412,24 @@ struct tpm_buf {
 	u8 *data;
 };
 
-static inline int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+static inline void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
 {
 	struct tpm_input_header *head;
+	head = (struct tpm_input_header *)buf->data;
+	head->tag = cpu_to_be16(tag);
+	head->length = cpu_to_be32(sizeof(*head));
+	head->ordinal = cpu_to_be32(ordinal);
+}
 
+static inline int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+{
 	buf->data_page = alloc_page(GFP_HIGHUSER);
 	if (!buf->data_page)
 		return -ENOMEM;
 
 	buf->flags = 0;
 	buf->data = kmap(buf->data_page);
-
-	head = (struct tpm_input_header *) buf->data;
-
-	head->tag = cpu_to_be16(tag);
-	head->length = cpu_to_be32(sizeof(*head));
-	head->ordinal = cpu_to_be32(ordinal);
-
+	tpm_buf_reset(buf, tag, ordinal);
 	return 0;
 }
 
@@ -557,7 +558,7 @@ static inline u32 tpm2_rc_value(u32 rc)
 int tpm2_pcr_read(struct tpm_chip *chip, int pcr_idx, u8 *res_buf);
 int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
 		    struct tpm2_digest *digests);
-int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max);
+int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max);
 void tpm2_flush_context_cmd(struct tpm_chip *chip, u32 handle,
 			    unsigned int flags);
 int tpm2_seal_trusted(struct tpm_chip *chip,
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index e02f7d46e9ac..36a58af6f5c7 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -27,25 +27,6 @@ enum tpm2_session_attributes {
 	TPM2_SA_CONTINUE_SESSION	= BIT(0),
 };
 
-struct tpm2_get_random_in {
-	__be16	size;
-} __packed;
-
-struct tpm2_get_random_out {
-	__be16	size;
-	u8	buffer[TPM_MAX_RNG_DATA];
-} __packed;
-
-union tpm2_cmd_params {
-	struct	tpm2_get_random_in	getrandom_in;
-	struct	tpm2_get_random_out	getrandom_out;
-};
-
-struct tpm2_cmd {
-	tpm_cmd_header		header;
-	union tpm2_cmd_params	params;
-} __packed;
-
 struct tpm2_hash {
 	unsigned int crypto_id;
 	unsigned int tpm_id;
@@ -298,66 +279,66 @@ int tpm2_pcr_extend(struct tpm_chip *chip, int pcr_idx, u32 count,
 }
 
 
-#define TPM2_GETRANDOM_IN_SIZE \
-	(sizeof(struct tpm_input_header) + \
-	 sizeof(struct tpm2_get_random_in))
-
-static const struct tpm_input_header tpm2_getrandom_header = {
-	.tag = cpu_to_be16(TPM2_ST_NO_SESSIONS),
-	.length = cpu_to_be32(TPM2_GETRANDOM_IN_SIZE),
-	.ordinal = cpu_to_be32(TPM2_CC_GET_RANDOM)
-};
+struct tpm2_get_random_out {
+	__be16 size;
+	u8 buffer[TPM_MAX_RNG_DATA];
+} __packed;
 
 /**
  * tpm2_get_random() - get random bytes from the TPM RNG
  *
  * @chip: TPM chip to use
- * @out: destination buffer for the random bytes
+ * @dest: destination buffer for the random bytes
  * @max: the max number of bytes to write to @out
  *
  * Return:
- *    Size of the output buffer, or -EIO on error.
+ * size of the output buffer when the operation is successful.
+ * A negative number for system errors (errno).
  */
-int tpm2_get_random(struct tpm_chip *chip, u8 *out, size_t max)
+int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 {
-	struct tpm2_cmd cmd;
-	u32 recd, rlength;
-	u32 num_bytes;
+	struct tpm2_get_random_out *out;
+	struct tpm_buf buf;
+	u32 recd;
+	u32 num_bytes = max;
 	int err;
 	int total = 0;
 	int retries = 5;
-	u8 *dest = out;
+	u8 *dest_ptr = dest;
 
-	num_bytes = min_t(u32, max, sizeof(cmd.params.getrandom_out.buffer));
-
-	if (!out || !num_bytes ||
-	    max > sizeof(cmd.params.getrandom_out.buffer))
+	if (!num_bytes || max > TPM_MAX_RNG_DATA)
 		return -EINVAL;
 
-	do {
-		cmd.header.in = tpm2_getrandom_header;
-		cmd.params.getrandom_in.size = cpu_to_be16(num_bytes);
+	err = tpm_buf_init(&buf, 0, 0);
+	if (err)
+		return err;
 
-		err = tpm_transmit_cmd(chip, NULL, &cmd, sizeof(cmd),
+	do {
+		tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_RANDOM);
+		tpm_buf_append_u16(&buf, num_bytes);
+		err = tpm_transmit_cmd(chip, NULL, buf.data, PAGE_SIZE,
 				       offsetof(struct tpm2_get_random_out,
 						buffer),
 				       0, "attempting get random");
 		if (err)
 			break;
 
-		recd = min_t(u32, be16_to_cpu(cmd.params.getrandom_out.size),
-			     num_bytes);
-		rlength = be32_to_cpu(cmd.header.out.length);
-		if (rlength < offsetof(struct tpm2_get_random_out, buffer) +
-			      recd)
-			return -EFAULT;
-		memcpy(dest, cmd.params.getrandom_out.buffer, recd);
+		out = (struct tpm2_get_random_out *)
+			&buf.data[TPM_HEADER_SIZE];
+		recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
+		if (tpm_buf_length(&buf) <
+		    offsetof(struct tpm2_get_random_out, buffer) + recd) {
+			err = -EFAULT;
+			break;
+		}
+		memcpy(dest_ptr, out->buffer, recd);
 
-		dest += recd;
+		dest_ptr += recd;
 		total += recd;
 		num_bytes -= recd;
 	} while (retries-- && total < max);
 
+	tpm_buf_destroy(&buf);
 	return total ? total : -EIO;
 }
 
@@ -432,7 +413,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 {
 	unsigned int blob_len;
 	struct tpm_buf buf;
-	u32 hash, rlength;
+	u32 hash;
 	int i;
 	int rc;
 
@@ -507,8 +488,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
 		rc = -E2BIG;
 		goto out;
 	}
-	rlength = be32_to_cpu(((struct tpm2_cmd *)&buf)->header.out.length);
-	if (rlength < TPM_HEADER_SIZE + 4 + blob_len) {
+	if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 4 + blob_len) {
 		rc = -EFAULT;
 		goto out;
 	}
@@ -618,7 +598,6 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 	u16 data_len;
 	u8 *data;
 	int rc;
-	u32 rlength;
 
 	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
 	if (rc)
@@ -646,9 +625,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
 			goto out;
 		}
 
-		rlength = be32_to_cpu(((struct tpm2_cmd *)&buf)
-					->header.out.length);
-		if (rlength < TPM_HEADER_SIZE + 6 + data_len) {
+		if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 6 + data_len) {
 			rc = -EFAULT;
 			goto out;
 		}
-- 
2.15.1