diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
index cccd5994a0e1..cffb71ec0289 100644
--- a/drivers/char/tpm/tpm.h
+++ b/drivers/char/tpm/tpm.h
@@ -557,7 +557,7 @@ 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 43791947b8e1..574caa33aab3 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;
@@ -298,62 +279,58 @@ 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_transmit_cmd(chip, NULL, &cmd, sizeof(cmd),
+		err = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS,
+				   TPM2_CC_GET_RANDOM);
+		if (err)
+			return err;
+		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)
+		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)
 			return -EFAULT;
-		memcpy(dest, cmd.params.getrandom_out.buffer, recd);
+		memcpy(dest_ptr, out->buffer, recd);
 
-		dest += recd;
+		dest_ptr += recd;
 		total += recd;
 		num_bytes -= recd;
 	} while (retries-- && total < max);
@@ -435,7 +412,7 @@ 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;
 
@@ -510,8 +487,7 @@ 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;
 	}
@@ -621,7 +597,6 @@ 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)
@@ -649,9 +624,7 @@ 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;
 		}
