Re: [PATCH 3/3] tpm-buf: Implement managed allocations

[Jarkko Sakkinen <jarkko@kernel.org>]

On Sat, Dec 06, 2025 at 01:31:10PM +0200, Jarkko Sakkinen wrote:
> From: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>
> 
> Decouple kzalloc from buffer creation, so that a managed allocation can be
> used:
> 
> 	struct tpm_buf *buf __free(kfree) buf = kzalloc(TPM_BUFSIZE,
> 							GFP_KERNEL);
> 	if (!buf)
> 		return -ENOMEM;
> 
> 	tpm_buf_init(buf, TPM_BUFSIZE);
> 
> Alternatively, stack allocations are also possible:
> 
> 	u8 buf_data[512];
> 	struct tpm_buf *buf = (struct tpm_buf *)buf_data;
> 	tpm_buf_init(buf, sizeof(buf_data));
> 
> This is achieved by embedding buffer's header inside the allocated blob,
> instead of having an outer wrapper.
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>
> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> ---
>  drivers/char/tpm/tpm-buf.c                | 124 +++++----
>  drivers/char/tpm/tpm-sysfs.c              |  21 +-
>  drivers/char/tpm/tpm.h                    |   1 -
>  drivers/char/tpm/tpm1-cmd.c               | 166 +++++------
>  drivers/char/tpm/tpm2-cmd.c               | 320 ++++++++++------------
>  drivers/char/tpm/tpm2-sessions.c          | 142 +++++-----
>  drivers/char/tpm/tpm2-space.c             |  44 ++-
>  drivers/char/tpm/tpm_vtpm_proxy.c         |  30 +-
>  include/linux/tpm.h                       |  20 +-
>  security/keys/trusted-keys/trusted_tpm1.c |  36 +--
>  security/keys/trusted-keys/trusted_tpm2.c | 170 ++++++------
>  11 files changed, 508 insertions(+), 566 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index 1b9dee0d0681..73be8a87b472 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -7,82 +7,109 @@
>  #include <linux/module.h>
>  #include <linux/tpm.h>
>  
> -/**
> - * tpm_buf_init() - Allocate and initialize a TPM command
> - * @buf:	A &tpm_buf
> - * @tag:	TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
> - * @ordinal:	A command ordinal
> - *
> - * Return: 0 or -ENOMEM
> - */
> -int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
> +static void __tpm_buf_size_invariant(struct tpm_buf *buf, u16 buf_size)
>  {
> -	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
> -	if (!buf->data)
> -		return -ENOMEM;
> -
> -	tpm_buf_reset(buf, tag, ordinal);
> -	return 0;
> +	u32 buf_size_2 = (u32)buf->capacity + (u32)sizeof(*buf);
> +
> +	if (!buf->capacity) {
> +		if (buf_size > TPM_BUFSIZE) {
> +			WARN(1, "%s: size overflow: %u\n", __func__, buf_size);
> +			buf->flags |= TPM_BUF_INVALID;
> +		}
> +	} else {
> +		if (buf_size != buf_size_2) {
> +			WARN(1, "%s: size mismatch: %u != %u\n", __func__, buf_size,
> +			     buf_size_2);
> +			buf->flags |= TPM_BUF_INVALID;
> +		}
> +	}
>  }
> -EXPORT_SYMBOL_GPL(tpm_buf_init);
>  
> -/**
> - * tpm_buf_reset() - Initialize a TPM command
> - * @buf:	A &tpm_buf
> - * @tag:	TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
> - * @ordinal:	A command ordinal
> - */
> -void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
> +static void __tpm_buf_reset(struct tpm_buf *buf, u16 buf_size, u16 tag, u32 ordinal)
>  {
>  	struct tpm_header *head = (struct tpm_header *)buf->data;
>  
> +	__tpm_buf_size_invariant(buf, buf_size);
> +
> +	if (buf->flags & TPM_BUF_INVALID)
> +		return;
> +
>  	WARN_ON(tag != TPM_TAG_RQU_COMMAND && tag != TPM2_ST_NO_SESSIONS &&
>  		tag != TPM2_ST_SESSIONS && tag != 0);
>  
>  	buf->flags = 0;
>  	buf->length = sizeof(*head);
> +	buf->capacity = buf_size - sizeof(*buf);
> +	buf->handles = 0;
>  	head->tag = cpu_to_be16(tag);
>  	head->length = cpu_to_be32(sizeof(*head));
>  	head->ordinal = cpu_to_be32(ordinal);
> +}
> +
> +static void __tpm_buf_reset_sized(struct tpm_buf *buf, u16 buf_size)
> +{
> +	__tpm_buf_size_invariant(buf, buf_size);
> +
> +	if (buf->flags & TPM_BUF_INVALID)
> +		return;
> +
> +	buf->flags = TPM_BUF_TPM2B;
> +	buf->length = 2;
> +	buf->capacity = buf_size - sizeof(*buf);
>  	buf->handles = 0;
> +	buf->data[0] = 0;
> +	buf->data[1] = 0;
>  }
> -EXPORT_SYMBOL_GPL(tpm_buf_reset);
>  
>  /**
> - * tpm_buf_init_sized() - Allocate and initialize a sized (TPM2B) buffer
> - * @buf:	A @tpm_buf
> - *
> - * Return: 0 or -ENOMEM
> + * tpm_buf_init() - Initialize a TPM command
> + * @buf:	A &tpm_buf
> + * @buf_size:	Size of the buffer.
>   */
> -int tpm_buf_init_sized(struct tpm_buf *buf)
> +void tpm_buf_init(struct tpm_buf *buf, u16 buf_size)
>  {
> -	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
> -	if (!buf->data)
> -		return -ENOMEM;
> +	memset(buf, 0, buf_size);
> +	__tpm_buf_reset(buf, buf_size, TPM_TAG_RQU_COMMAND, 0);
> +}
> +EXPORT_SYMBOL_GPL(tpm_buf_init);
>  
> -	tpm_buf_reset_sized(buf);
> -	return 0;
> +/**
> + * tpm_buf_init_sized() - Initialize a sized buffer
> + * @buf:	A &tpm_buf
> + * @buf_size:	Size of the buffer.
> + */
> +void tpm_buf_init_sized(struct tpm_buf *buf, u16 buf_size)
> +{
> +	memset(buf, 0, buf_size);
> +	__tpm_buf_reset_sized(buf, buf_size);
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_init_sized);
>  
>  /**
> - * tpm_buf_reset_sized() - Initialize a sized buffer
> + * tpm_buf_reset() - Re-initialize a TPM command
>   * @buf:	A &tpm_buf
> + * @tag:	TPM_TAG_RQU_COMMAND, TPM2_ST_NO_SESSIONS or TPM2_ST_SESSIONS
> + * @ordinal:	A command ordinal
>   */
> -void tpm_buf_reset_sized(struct tpm_buf *buf)
> +void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
>  {
> -	buf->flags = TPM_BUF_TPM2B;
> -	buf->length = 2;
> -	buf->data[0] = 0;
> -	buf->data[1] = 0;
> +	u16 buf_size = buf->capacity + sizeof(*buf);
> +
> +	__tpm_buf_reset(buf, buf_size, tag, ordinal);
>  }
> -EXPORT_SYMBOL_GPL(tpm_buf_reset_sized);
> +EXPORT_SYMBOL_GPL(tpm_buf_reset);
>  
> -void tpm_buf_destroy(struct tpm_buf *buf)
> +/**
> + * tpm_buf_reset_sized() - Re-initialize a sized buffer
> + * @buf:	A &tpm_buf
> + */
> +void tpm_buf_reset_sized(struct tpm_buf *buf)
>  {
> -	free_page((unsigned long)buf->data);
> +	u16 buf_size = buf->capacity + sizeof(*buf);
> +
> +	__tpm_buf_reset_sized(buf, buf_size);
>  }
> -EXPORT_SYMBOL_GPL(tpm_buf_destroy);
> +EXPORT_SYMBOL_GPL(tpm_buf_reset_sized);
>  
>  /**
>   * tpm_buf_length() - Return the number of bytes consumed by the data
> @@ -90,8 +117,11 @@ EXPORT_SYMBOL_GPL(tpm_buf_destroy);
>   *
>   * Return: The number of bytes consumed by the buffer
>   */
> -u32 tpm_buf_length(struct tpm_buf *buf)
> +u16 tpm_buf_length(struct tpm_buf *buf)
>  {
> +	if (buf->flags & TPM_BUF_INVALID)
> +		return 0;
> +
>  	return buf->length;
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_length);
> @@ -104,10 +134,12 @@ EXPORT_SYMBOL_GPL(tpm_buf_length);
>   */
>  void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length)
>  {
> +	u32 total_length = (u32)buf->length + (u32)new_length;
> +
>  	if (buf->flags & TPM_BUF_INVALID)
>  		return;
>  
> -	if ((buf->length + new_length) > PAGE_SIZE) {
> +	if (total_length > (u32)buf->capacity) {
>  		WARN(1, "tpm_buf: write overflow\n");
>  		buf->flags |= TPM_BUF_INVALID;
>  		return;
> diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
> index 94231f052ea7..f5dcadb1ab3c 100644
> --- a/drivers/char/tpm/tpm-sysfs.c
> +++ b/drivers/char/tpm/tpm-sysfs.c
> @@ -32,28 +32,29 @@ struct tpm_readpubek_out {
>  static ssize_t pubek_show(struct device *dev, struct device_attribute *attr,
>  			  char *buf)
>  {
> -	struct tpm_buf tpm_buf;
>  	struct tpm_readpubek_out *out;
>  	int i;
>  	char *str = buf;
>  	struct tpm_chip *chip = to_tpm_chip(dev);
>  	char anti_replay[20];
>  
> +	struct tpm_buf *tpm_buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!tpm_buf)
> +		return -ENOMEM;
> +
>  	memset(&anti_replay, 0, sizeof(anti_replay));
>  
>  	if (tpm_try_get_ops(chip))
>  		return 0;
>  
> -	if (tpm_buf_init(&tpm_buf, TPM_TAG_RQU_COMMAND, TPM_ORD_READPUBEK))
> -		goto out_ops;
> -
> -	tpm_buf_append(&tpm_buf, anti_replay, sizeof(anti_replay));
> +	tpm_buf_init(tpm_buf, TPM_BUFSIZE);
> +	tpm_buf_reset(tpm_buf, TPM_TAG_RQU_COMMAND, TPM_ORD_READPUBEK);
> +	tpm_buf_append(tpm_buf, anti_replay, sizeof(anti_replay));
>  
> -	if (tpm_transmit_cmd(chip, &tpm_buf, READ_PUBEK_RESULT_MIN_BODY_SIZE,
> -			     "attempting to read the PUBEK"))
> -		goto out_buf;
> +	if (tpm_transmit_cmd(chip, tpm_buf, READ_PUBEK_RESULT_MIN_BODY_SIZE, "TPM_ReadPubek"))
> +		goto out_ops;
>  
> -	out = (struct tpm_readpubek_out *)&tpm_buf.data[10];
> +	out = (struct tpm_readpubek_out *)&tpm_buf->data[10];
>  	str +=
>  	    sprintf(str,
>  		    "Algorithm: %4ph\n"
> @@ -71,8 +72,6 @@ static ssize_t pubek_show(struct device *dev, struct device_attribute *attr,
>  	for (i = 0; i < 256; i += 16)
>  		str += sprintf(str, "%16ph\n", &out->modulus[i]);
>  
> -out_buf:
> -	tpm_buf_destroy(&tpm_buf);
>  out_ops:
>  	tpm_put_ops(chip);
>  	return str - buf;
> diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h
> index 02c07fef41ba..5395927c62fc 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -32,7 +32,6 @@
>  #endif
>  
>  #define TPM_MINOR		224	/* officially assigned */
> -#define TPM_BUFSIZE		4096
>  #define TPM_NUM_DEVICES		65536
>  #define TPM_RETRY		50
>  
> diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
> index b49a790f1bd5..11090053ef54 100644
> --- a/drivers/char/tpm/tpm1-cmd.c
> +++ b/drivers/char/tpm/tpm1-cmd.c
> @@ -323,20 +323,14 @@ unsigned long tpm1_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal)
>   */
>  static int tpm1_startup(struct tpm_chip *chip)
>  {
> -	struct tpm_buf buf;
> -	int rc;
> -
> -	dev_info(&chip->dev, "starting up the TPM manually\n");
> -
> -	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_STARTUP);
> -	if (rc < 0)
> -		return rc;
> -
> -	tpm_buf_append_u16(&buf, TPM_ST_CLEAR);
> -
> -	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to start the TPM");
> -	tpm_buf_destroy(&buf);
> -	return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_STARTUP);
> +	tpm_buf_append_u16(buf, TPM_ST_CLEAR);
> +	return tpm_transmit_cmd(chip, buf, 0, "TPM_Startup");
>  }
>  
>  int tpm1_get_timeouts(struct tpm_chip *chip)
> @@ -463,50 +457,47 @@ int tpm1_get_timeouts(struct tpm_chip *chip)
>  int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash,
>  		    const char *log_msg)
>  {
> -	struct tpm_buf buf;
> -	int rc;
> -
> -	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCR_EXTEND);
> -	if (rc)
> -		return rc;
> -
> -	tpm_buf_append_u32(&buf, pcr_idx);
> -	tpm_buf_append(&buf, hash, TPM_DIGEST_SIZE);
> -
> -	rc = tpm_transmit_cmd(chip, &buf, TPM_DIGEST_SIZE, log_msg);
> -	tpm_buf_destroy(&buf);
> -	return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCR_EXTEND);
> +	tpm_buf_append_u32(buf, pcr_idx);
> +	tpm_buf_append(buf, hash, TPM_DIGEST_SIZE);
> +	return tpm_transmit_cmd(chip, buf, TPM_DIGEST_SIZE, log_msg);
>  }
>  
>  #define TPM_ORD_GET_CAP 101
>  ssize_t tpm1_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap,
>  		    const char *desc, size_t min_cap_length)
>  {
> -	struct tpm_buf buf;
>  	int rc;
>  
> -	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_CAP);
> -	if (rc)
> -		return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_CAP);
>  
>  	if (subcap_id == TPM_CAP_VERSION_1_1 ||
>  	    subcap_id == TPM_CAP_VERSION_1_2) {
> -		tpm_buf_append_u32(&buf, subcap_id);
> -		tpm_buf_append_u32(&buf, 0);
> +		tpm_buf_append_u32(buf, subcap_id);
> +		tpm_buf_append_u32(buf, 0);
>  	} else {
>  		if (subcap_id == TPM_CAP_FLAG_PERM ||
>  		    subcap_id == TPM_CAP_FLAG_VOL)
> -			tpm_buf_append_u32(&buf, TPM_CAP_FLAG);
> +			tpm_buf_append_u32(buf, TPM_CAP_FLAG);
>  		else
> -			tpm_buf_append_u32(&buf, TPM_CAP_PROP);
> +			tpm_buf_append_u32(buf, TPM_CAP_PROP);
>  
> -		tpm_buf_append_u32(&buf, 4);
> -		tpm_buf_append_u32(&buf, subcap_id);
> +		tpm_buf_append_u32(buf, 4);
> +		tpm_buf_append_u32(buf, subcap_id);
>  	}
> -	rc = tpm_transmit_cmd(chip, &buf, min_cap_length, desc);
> +	rc = tpm_transmit_cmd(chip, buf, min_cap_length, desc);
>  	if (!rc)
> -		*cap = *(cap_t *)&buf.data[TPM_HEADER_SIZE + 4];
> -	tpm_buf_destroy(&buf);
> +		*cap = *(cap_t *)&buf->data[TPM_HEADER_SIZE + 4];
>  	return rc;
>  }
>  EXPORT_SYMBOL_GPL(tpm1_getcap);
> @@ -531,81 +522,69 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  {
>  	struct tpm1_get_random_out *out;
>  	u32 num_bytes =  min_t(u32, max, TPM_MAX_RNG_DATA);
> -	struct tpm_buf buf;
>  	u32 total = 0;
>  	int retries = 5;
>  	u32 recd;
>  	int rc;
>  
> -	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_RANDOM);
> -	if (rc)
> -		return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>  
> +	tpm_buf_init(buf, TPM_BUFSIZE);
>  	do {
> -		tpm_buf_append_u32(&buf, num_bytes);
> +		tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_RANDOM);
> +		tpm_buf_append_u32(buf, num_bytes);
>  
> -		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
> -				      "attempting get random");
> +		rc = tpm_transmit_cmd(chip, buf, sizeof(out->rng_data_len), "TPM_GetRandom");
>  		if (rc) {
>  			if (rc > 0)
>  				rc = -EIO;
> -			goto out;
> +			return rc;
>  		}
>  
> -		out = (struct tpm1_get_random_out *)&buf.data[TPM_HEADER_SIZE];
> +		out = (struct tpm1_get_random_out *)&buf->data[TPM_HEADER_SIZE];
>  
>  		recd = be32_to_cpu(out->rng_data_len);
> -		if (recd > num_bytes) {
> -			rc = -EFAULT;
> -			goto out;
> -		}
> +		if (recd > num_bytes)
> +			return -EFAULT;
> +
> +		if (buf->length < TPM_HEADER_SIZE +
> +				  sizeof(out->rng_data_len) + recd)
> +			return -EFAULT;
>  
> -		if (tpm_buf_length(&buf) < TPM_HEADER_SIZE +
> -					   sizeof(out->rng_data_len) + recd) {
> -			rc = -EFAULT;
> -			goto out;
> -		}
>  		memcpy(dest, out->rng_data, recd);
>  
>  		dest += recd;
>  		total += recd;
>  		num_bytes -= recd;
> -
> -		tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_RANDOM);
>  	} while (retries-- && total < max);
>  
>  	rc = total ? (int)total : -EIO;
> -out:
> -	tpm_buf_destroy(&buf);
>  	return rc;
>  }
>  
>  #define TPM_ORD_PCRREAD 21
>  int tpm1_pcr_read(struct tpm_chip *chip, u32 pcr_idx, u8 *res_buf)
>  {
> -	struct tpm_buf buf;
>  	int rc;
>  
> -	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCRREAD);
> -	if (rc)
> -		return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>  
> -	tpm_buf_append_u32(&buf, pcr_idx);
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCRREAD);
> +	tpm_buf_append_u32(buf, pcr_idx);
>  
> -	rc = tpm_transmit_cmd(chip, &buf, TPM_DIGEST_SIZE,
> -			      "attempting to read a pcr value");
> +	rc = tpm_transmit_cmd(chip, buf, TPM_DIGEST_SIZE, "TPM_PCRRead");
>  	if (rc)
> -		goto out;
> -
> -	if (tpm_buf_length(&buf) < TPM_DIGEST_SIZE) {
> -		rc = -EFAULT;
> -		goto out;
> -	}
> +		return rc;
>  
> -	memcpy(res_buf, &buf.data[TPM_HEADER_SIZE], TPM_DIGEST_SIZE);
> +	if (buf->length < TPM_DIGEST_SIZE)
> +		return -EFAULT;
>  
> -out:
> -	tpm_buf_destroy(&buf);
> +	memcpy(res_buf, &buf->data[TPM_HEADER_SIZE], TPM_DIGEST_SIZE);
>  	return rc;
>  }
>  
> @@ -619,16 +598,13 @@ int tpm1_pcr_read(struct tpm_chip *chip, u32 pcr_idx, u8 *res_buf)
>   */
>  static int tpm1_continue_selftest(struct tpm_chip *chip)
>  {
> -	struct tpm_buf buf;
> -	int rc;
> -
> -	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_CONTINUE_SELFTEST);
> -	if (rc)
> -		return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 0, "continue selftest");
> -	tpm_buf_destroy(&buf);
> -	return rc;
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_CONTINUE_SELFTEST);
> +	return tpm_transmit_cmd(chip, buf, 0, "TPM_ContinueSelfTest");
>  }
>  
>  /**
> @@ -742,22 +718,24 @@ int tpm1_auto_startup(struct tpm_chip *chip)
>  int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
>  {
>  	u8 dummy_hash[TPM_DIGEST_SIZE] = { 0 };
> -	struct tpm_buf buf;
>  	unsigned int try;
>  	int rc;
>  
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>  
>  	/* for buggy tpm, flush pcrs with extend to selected dummy */
>  	if (tpm_suspend_pcr)
>  		rc = tpm1_pcr_extend(chip, tpm_suspend_pcr, dummy_hash,
>  				     "extending dummy pcr before suspend");
>  
> -	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SAVESTATE);
> -	if (rc)
> -		return rc;
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SAVESTATE);
> +
>  	/* now do the actual savestate */
>  	for (try = 0; try < TPM_RETRY; try++) {
> -		rc = tpm_transmit_cmd(chip, &buf, 0, NULL);
> +		rc = tpm_transmit_cmd(chip, buf, 0, NULL);
>  		/*
>  		 * If the TPM indicates that it is too busy to respond to
>  		 * this command then retry before giving up.  It can take
> @@ -772,7 +750,7 @@ int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
>  			break;
>  		tpm_msleep(TPM_TIMEOUT_RETRY);
>  
> -		tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SAVESTATE);
> +		tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SAVESTATE);
>  	}
>  
>  	if (rc)
> @@ -782,8 +760,6 @@ int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
>  		dev_warn(&chip->dev, "TPM savestate took %dms\n",
>  			 try * TPM_TIMEOUT_RETRY);
>  
> -	tpm_buf_destroy(&buf);
> -
>  	return rc;
>  }
>  
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 82076b6cfcf7..2682f5ec09cb 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -119,12 +119,15 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
>  {
>  	int i;
>  	int rc;
> -	struct tpm_buf buf;
>  	struct tpm2_pcr_read_out *out;
>  	u8 pcr_select[TPM2_PCR_SELECT_MIN] = {0};
>  	u16 digest_size;
>  	u16 expected_digest_size = 0;
>  
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
>  	if (pcr_idx >= TPM2_PLATFORM_PCR)
>  		return -EINVAL;
>  
> @@ -139,36 +142,31 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
>  		expected_digest_size = chip->allocated_banks[i].digest_size;
>  	}
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
> -	if (rc)
> -		return rc;
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_PCR_READ);
>  
>  	pcr_select[pcr_idx >> 3] = 1 << (pcr_idx & 0x7);
>  
> -	tpm_buf_append_u32(&buf, 1);
> -	tpm_buf_append_u16(&buf, digest->alg_id);
> -	tpm_buf_append_u8(&buf, TPM2_PCR_SELECT_MIN);
> -	tpm_buf_append(&buf, (const unsigned char *)pcr_select,
> +	tpm_buf_append_u32(buf, 1);
> +	tpm_buf_append_u16(buf, digest->alg_id);
> +	tpm_buf_append_u8(buf, TPM2_PCR_SELECT_MIN);
> +	tpm_buf_append(buf, (const unsigned char *)pcr_select,
>  		       sizeof(pcr_select));
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to read a pcr value");
> +	rc = tpm_transmit_cmd(chip, buf, 0, "TPM2_PCR_Read");
>  	if (rc)
> -		goto out;
> +		return rc;
>  
> -	out = (struct tpm2_pcr_read_out *)&buf.data[TPM_HEADER_SIZE];
> +	out = (struct tpm2_pcr_read_out *)&buf->data[TPM_HEADER_SIZE];
>  	digest_size = be16_to_cpu(out->digest_size);
>  	if (digest_size > sizeof(digest->digest) ||
> -	    (!digest_size_ptr && digest_size != expected_digest_size)) {
> -		rc = -EINVAL;
> -		goto out;
> -	}
> +	    (!digest_size_ptr && digest_size != expected_digest_size))
> +		return rc;
>  
>  	if (digest_size_ptr)
>  		*digest_size_ptr = digest_size;
>  
>  	memcpy(digest->digest, out->digest, digest_size);
> -out:
> -	tpm_buf_destroy(&buf);
>  	return rc;
>  }
>  
> @@ -184,56 +182,52 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
>  int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx,
>  		    struct tpm_digest *digests)
>  {
> -	struct tpm_buf buf;
>  	int rc;
>  	int i;
>  
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
>  	if (!disable_pcr_integrity) {
>  		rc = tpm2_start_auth_session(chip);
>  		if (rc)
>  			return rc;
>  	}
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
> -	if (rc) {
> -		if (!disable_pcr_integrity)
> -			tpm2_end_auth_session(chip);
> -		return rc;
> -	}
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
>  
>  	if (!disable_pcr_integrity) {
> -		rc = tpm_buf_append_name(chip, &buf, pcr_idx, NULL);
> -		if (rc) {
> -			tpm_buf_destroy(&buf);
> +		rc = tpm_buf_append_name(chip, buf, pcr_idx, NULL);
> +		if (rc)
>  			return rc;
> -		}
> -		tpm_buf_append_hmac_session(chip, &buf, 0, NULL, 0);
> +		tpm_buf_append_hmac_session(chip, buf, 0, NULL, 0);
>  	} else {
> -		tpm_buf_append_handle(&buf, pcr_idx);
> -		tpm_buf_append_auth(chip, &buf, NULL, 0);
> +		tpm_buf_append_handle(buf, pcr_idx);
> +		tpm_buf_append_auth(chip, buf, NULL, 0);
>  	}
>  
> -	tpm_buf_append_u32(&buf, chip->nr_allocated_banks);
> +	tpm_buf_append_u32(buf, chip->nr_allocated_banks);
>  
>  	for (i = 0; i < chip->nr_allocated_banks; i++) {
> -		tpm_buf_append_u16(&buf, digests[i].alg_id);
> -		tpm_buf_append(&buf, (const unsigned char *)&digests[i].digest,
> +		tpm_buf_append_u16(buf, digests[i].alg_id);
> +		tpm_buf_append(buf, (const unsigned char *)&digests[i].digest,
>  			       chip->allocated_banks[i].digest_size);
>  	}
> +	if (buf->flags & TPM_BUF_INVALID)
> +		return -EINVAL;
>  
>  	if (!disable_pcr_integrity) {
> -		rc = tpm_buf_fill_hmac_session(chip, &buf);
> -		if (rc) {
> -			tpm_buf_destroy(&buf);
> +		rc = tpm_buf_fill_hmac_session(chip, buf);
> +		if (rc)
>  			return rc;
> -		}
>  	}
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting extend a PCR value");
> -	if (!disable_pcr_integrity)
> -		rc = tpm_buf_check_hmac_response(chip, &buf, rc);
> +	rc = tpm_transmit_cmd(chip, buf, 0, "TPM2_PCR_Extend");
>  
> -	tpm_buf_destroy(&buf);
> +	if (!disable_pcr_integrity)
> +		rc = tpm_buf_check_hmac_response(chip, buf, rc);
>  
>  	return rc;
>  }
> @@ -258,7 +252,6 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  {
>  	struct tpm2_get_random_out *out;
>  	struct tpm_header *head;
> -	struct tpm_buf buf;
>  	u32 recd;
>  	u32 num_bytes = max;
>  	int err;
> @@ -270,61 +263,58 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  	if (!num_bytes || max > TPM_MAX_RNG_DATA)
>  		return -EINVAL;
>  
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
>  	err = tpm2_start_auth_session(chip);
>  	if (err)
>  		return err;
>  
> -	err = tpm_buf_init(&buf, 0, 0);
> -	if (err) {
> -		tpm2_end_auth_session(chip);
> -		return err;
> -	}
> -
> +	tpm_buf_init(buf, TPM_BUFSIZE);
>  	do {
> -		tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
> +		tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
>  		if (tpm2_chip_auth(chip)) {
> -			tpm_buf_append_hmac_session(chip, &buf,
> +			tpm_buf_append_hmac_session(chip, buf,
>  						    TPM2_SA_ENCRYPT |
>  						    TPM2_SA_CONTINUE_SESSION,
>  						    NULL, 0);
>  		} else  {
> -			offset = buf.handles * 4 + TPM_HEADER_SIZE;
> -			head = (struct tpm_header *)buf.data;
> -			if (tpm_buf_length(&buf) == offset)
> +			offset = buf->handles * 4 + TPM_HEADER_SIZE;
> +			head = (struct tpm_header *)buf->data;
> +			if (tpm_buf_length(buf) == offset)
>  				head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
>  		}
> -		tpm_buf_append_u16(&buf, num_bytes);
> -		err = tpm_buf_fill_hmac_session(chip, &buf);
> -		if (err) {
> -			tpm_buf_destroy(&buf);
> +		tpm_buf_append_u16(buf, num_bytes);
> +
> +		err = tpm_buf_fill_hmac_session(chip, buf);
> +		if (err)
>  			return err;
> -		}
>  
> -		err = tpm_transmit_cmd(chip, &buf,
> +		err = tpm_transmit_cmd(chip, buf,
>  				       offsetof(struct tpm2_get_random_out,
>  						buffer),
> -				       "attempting get random");
> -		err = tpm_buf_check_hmac_response(chip, &buf, err);
> +				       "TPM2_GetRandom");
> +		err = tpm_buf_check_hmac_response(chip, buf, err);
>  		if (err) {
>  			if (err > 0)
>  				err = -EIO;
> -			goto out;
> +			return err;
>  		}
>  
> -		head = (struct tpm_header *)buf.data;
> +		head = (struct tpm_header *)buf->data;
>  		offset = TPM_HEADER_SIZE;
>  		/* Skip the parameter size field: */
>  		if (be16_to_cpu(head->tag) == TPM2_ST_SESSIONS)
>  			offset += 4;
>  
> -		out = (struct tpm2_get_random_out *)&buf.data[offset];
> +		out = (struct tpm2_get_random_out *)&buf->data[offset];
>  		recd = min_t(u32, be16_to_cpu(out->size), num_bytes);
> -		if (tpm_buf_length(&buf) <
> +		if (tpm_buf_length(buf) <
>  		    TPM_HEADER_SIZE +
>  		    offsetof(struct tpm2_get_random_out, buffer) +
>  		    recd) {
> -			err = -EFAULT;
> -			goto out;
> +			return -EFAULT;
>  		}
>  		memcpy(dest_ptr, out->buffer, recd);
>  
> @@ -333,13 +323,7 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>  		num_bytes -= recd;
>  	} while (retries-- && total < max);
>  
> -	tpm_buf_destroy(&buf);
> -
>  	return total ? total : -EIO;
> -out:
> -	tpm_buf_destroy(&buf);
> -	tpm2_end_auth_session(chip);
> -	return err;
>  }
>  
>  /**
> @@ -349,20 +333,18 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>   */
>  void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
>  {
> -	struct tpm_buf buf;
> -	int rc;
> -
> -	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_FLUSH_CONTEXT);
> -	if (rc) {
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf) {
>  		dev_warn(&chip->dev, "0x%08x was not flushed, out of memory\n",
>  			 handle);
>  		return;
>  	}
>  
> -	tpm_buf_append_u32(&buf, handle);
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_FLUSH_CONTEXT);
> +	tpm_buf_append_u32(buf, handle);
>  
> -	tpm_transmit_cmd(chip, &buf, 0, "flushing context");
> -	tpm_buf_destroy(&buf);
> +	tpm_transmit_cmd(chip, buf, 0, "TPM2_FlushContext");
>  }
>  EXPORT_SYMBOL_GPL(tpm2_flush_context);
>  
> @@ -389,19 +371,20 @@ ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,  u32 *value,
>  			const char *desc)
>  {
>  	struct tpm2_get_cap_out *out;
> -	struct tpm_buf buf;
>  	int rc;
>  
> -	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, &buf, 0, NULL);
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
> +	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, buf, 0, NULL);
>  	if (!rc) {
> -		out = (struct tpm2_get_cap_out *)
> -			&buf.data[TPM_HEADER_SIZE];
> +		out = (struct tpm2_get_cap_out *)&buf->data[TPM_HEADER_SIZE];
>  		/*
>  		 * To prevent failing boot up of some systems, Infineon TPM2.0
>  		 * returns SUCCESS on TPM2_Startup in field upgrade mode. Also
> @@ -413,7 +396,6 @@ ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,  u32 *value,
>  		else
>  			rc = -ENODATA;
>  	}
> -	tpm_buf_destroy(&buf);
>  	return rc;
>  }
>  EXPORT_SYMBOL_GPL(tpm2_get_tpm_pt);
> @@ -430,15 +412,14 @@ EXPORT_SYMBOL_GPL(tpm2_get_tpm_pt);
>   */
>  void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type)
>  {
> -	struct tpm_buf buf;
> -	int rc;
> -
> -	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SHUTDOWN);
> -	if (rc)
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
>  		return;
> -	tpm_buf_append_u16(&buf, shutdown_type);
> -	tpm_transmit_cmd(chip, &buf, 0, "stopping the TPM");
> -	tpm_buf_destroy(&buf);
> +
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SHUTDOWN);
> +	tpm_buf_append_u16(buf, shutdown_type);
> +	tpm_transmit_cmd(chip, buf, 0, "TPM2_Shutdown");
>  }
>  
>  /**
> @@ -456,20 +437,19 @@ void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type)
>   */
>  static int tpm2_do_selftest(struct tpm_chip *chip)
>  {
> -	struct tpm_buf buf;
>  	int full;
>  	int rc;
>  
> -	for (full = 0; full < 2; full++) {
> -		rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SELF_TEST);
> -		if (rc)
> -			return rc;
> -
> -		tpm_buf_append_u8(&buf, full);
> -		rc = tpm_transmit_cmd(chip, &buf, 0,
> -				      "attempting the self test");
> -		tpm_buf_destroy(&buf);
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>  
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SELF_TEST);
> +	for (full = 0; full < 2; full++) {
> +		tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SELF_TEST);
> +		tpm_buf_append_u8(buf, full);
> +		rc = tpm_transmit_cmd(chip, buf, 0, "TPM2_SelfTest");
>  		if (rc == TPM2_RC_TESTING)
>  			rc = TPM2_RC_SUCCESS;
>  		if (rc == TPM2_RC_INITIALIZE || rc == TPM2_RC_SUCCESS)
> @@ -494,23 +474,24 @@ static int tpm2_do_selftest(struct tpm_chip *chip)
>  int tpm2_probe(struct tpm_chip *chip)
>  {
>  	struct tpm_header *out;
> -	struct tpm_buf buf;
>  	int rc;
>  
> -	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, TPM_PT_TOTAL_COMMANDS);
> -	tpm_buf_append_u32(&buf, 1);
> -	rc = tpm_transmit_cmd(chip, &buf, 0, NULL);
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
> +	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, buf, 0, NULL);
>  	/* We ignore TPM return codes on purpose. */
>  	if (rc >=  0) {
> -		out = (struct tpm_header *)buf.data;
> +		out = (struct tpm_header *)buf->data;
>  		if (be16_to_cpu(out->tag) == TPM2_ST_NO_SESSIONS)
>  			chip->flags |= TPM_CHIP_FLAG_TPM2;
>  	}
> -	tpm_buf_destroy(&buf);
>  	return 0;
>  }
>  EXPORT_SYMBOL_GPL(tpm2_probe);
> @@ -550,7 +531,6 @@ struct tpm2_pcr_selection {
>  ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>  {
>  	struct tpm2_pcr_selection pcr_selection;
> -	struct tpm_buf buf;
>  	void *marker;
>  	void *end;
>  	void *pcr_select_offset;
> @@ -562,39 +542,37 @@ ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>  	int rc;
>  	int i = 0;
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
> -	if (rc)
> -		return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>  
> -	tpm_buf_append_u32(&buf, TPM2_CAP_PCRS);
> -	tpm_buf_append_u32(&buf, 0);
> -	tpm_buf_append_u32(&buf, 1);
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
> +	tpm_buf_append_u32(buf, TPM2_CAP_PCRS);
> +	tpm_buf_append_u32(buf, 0);
> +	tpm_buf_append_u32(buf, 1);
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 9, "get tpm pcr allocation");
> +	rc = tpm_transmit_cmd(chip, buf, 9, "TPM2_GetCapability(PCRS)");
>  	if (rc)
> -		goto out;
> +		return rc;
>  
> -	nr_possible_banks = be32_to_cpup(
> -		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
> +	nr_possible_banks = be32_to_cpup((__be32 *)&buf->data[TPM_HEADER_SIZE + 5]);
>  	if (nr_possible_banks > TPM2_MAX_PCR_BANKS) {
>  		pr_err("tpm: out of bank capacity: %u > %u\n",
>  		       nr_possible_banks, TPM2_MAX_PCR_BANKS);
> -		rc = -ENOMEM;
> -		goto out;
> +		return -ENOMEM;
>  	}
>  
> -	marker = &buf.data[TPM_HEADER_SIZE + 9];
> +	marker = &buf->data[TPM_HEADER_SIZE + 9];
>  
> -	rsp_len = be32_to_cpup((__be32 *)&buf.data[2]);
> -	end = &buf.data[rsp_len];
> +	rsp_len = be32_to_cpup((__be32 *)&buf->data[2]);
> +	end = &buf->data[rsp_len];
>  
>  	for (i = 0; i < nr_possible_banks; i++) {
>  		pcr_select_offset = marker +
>  			offsetof(struct tpm2_pcr_selection, size_of_select);
> -		if (pcr_select_offset >= end) {
> -			rc = -EFAULT;
> -			break;
> -		}
> +		if (pcr_select_offset >= end)
> +			return -EFAULT;
>  
>  		memcpy(&pcr_selection, marker, sizeof(pcr_selection));
>  		hash_alg = be16_to_cpu(pcr_selection.hash_alg);
> @@ -606,7 +584,7 @@ ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>  
>  			rc = tpm2_init_bank_info(chip, nr_alloc_banks);
>  			if (rc < 0)
> -				break;
> +				return rc;
>  
>  			nr_alloc_banks++;
>  		}
> @@ -618,21 +596,21 @@ ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>  	}
>  
>  	chip->nr_allocated_banks = nr_alloc_banks;
> -out:
> -	tpm_buf_destroy(&buf);
> -
> -	return rc;
> +	return 0;
>  }
>  
>  int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip)
>  {
> -	struct tpm_buf buf;
>  	u32 nr_commands;
>  	__be32 *attrs;
>  	u32 cc;
>  	int i;
>  	int rc;
>  
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
>  	rc = tpm2_get_tpm_pt(chip, TPM_PT_TOTAL_COMMANDS, &nr_commands, NULL);
>  	if (rc)
>  		goto out;
> @@ -649,30 +627,24 @@ int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip)
>  		goto out;
>  	}
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
> -	if (rc)
> -		goto out;
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_CAPABILITY);
> +	tpm_buf_append_u32(buf, TPM2_CAP_COMMANDS);
> +	tpm_buf_append_u32(buf, TPM2_CC_FIRST);
> +	tpm_buf_append_u32(buf, nr_commands);
>  
> -	tpm_buf_append_u32(&buf, TPM2_CAP_COMMANDS);
> -	tpm_buf_append_u32(&buf, TPM2_CC_FIRST);
> -	tpm_buf_append_u32(&buf, nr_commands);
> -
> -	rc = tpm_transmit_cmd(chip, &buf, 9 + 4 * nr_commands, NULL);
> -	if (rc) {
> -		tpm_buf_destroy(&buf);
> +	rc = tpm_transmit_cmd(chip, buf, 9 + 4 * nr_commands, NULL);
> +	if (rc)
>  		goto out;
> -	}
>  
> -	if (nr_commands !=
> -	    be32_to_cpup((__be32 *)&buf.data[TPM_HEADER_SIZE + 5])) {
> +	if (nr_commands != be32_to_cpup((__be32 *)&buf->data[TPM_HEADER_SIZE + 5])) {
>  		rc = -EFAULT;
> -		tpm_buf_destroy(&buf);
>  		goto out;
>  	}
>  
>  	chip->nr_commands = nr_commands;
>  
> -	attrs = (__be32 *)&buf.data[TPM_HEADER_SIZE + 9];
> +	attrs = (__be32 *)&buf->data[TPM_HEADER_SIZE + 9];
>  	for (i = 0; i < nr_commands; i++, attrs++) {
>  		chip->cc_attrs_tbl[i] = be32_to_cpup(attrs);
>  		cc = chip->cc_attrs_tbl[i] & 0xFFFF;
> @@ -684,8 +656,6 @@ int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip)
>  		}
>  	}
>  
> -	tpm_buf_destroy(&buf);
> -
>  out:
>  	if (rc > 0)
>  		rc = -ENODEV;
> @@ -706,20 +676,14 @@ EXPORT_SYMBOL_GPL(tpm2_get_cc_attrs_tbl);
>  
>  static int tpm2_startup(struct tpm_chip *chip)
>  {
> -	struct tpm_buf buf;
> -	int rc;
> -
> -	dev_info(&chip->dev, "starting up the TPM manually\n");
> -
> -	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_STARTUP);
> -	if (rc < 0)
> -		return rc;
> -
> -	tpm_buf_append_u16(&buf, TPM2_SU_CLEAR);
> -	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to start the TPM");
> -	tpm_buf_destroy(&buf);
> -
> -	return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_STARTUP);
> +	tpm_buf_append_u16(buf, TPM2_SU_CLEAR);
> +	return tpm_transmit_cmd(chip, buf, 0, "TPM2_Startup");
>  }
>  
>  /**
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 92d116d73c6f..79f27a46bd7f 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -168,7 +168,6 @@ static int tpm2_read_public(struct tpm_chip *chip, u32 handle, void *name)
>  	u32 mso = tpm2_handle_mso(handle);
>  	off_t offset = TPM_HEADER_SIZE;
>  	int rc, name_size_alg;
> -	struct tpm_buf buf;
>  
>  	if (mso != TPM2_MSO_PERSISTENT && mso != TPM2_MSO_VOLATILE &&
>  	    mso != TPM2_MSO_NVRAM) {
> @@ -176,47 +175,41 @@ static int tpm2_read_public(struct tpm_chip *chip, u32 handle, void *name)
>  		return sizeof(u32);
>  	}
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
> -	if (rc)
> -		return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>  
> -	tpm_buf_append_u32(&buf, handle);
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
> +	tpm_buf_append_u32(buf, handle);
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 0, "TPM2_ReadPublic");
> -	if (rc) {
> -		tpm_buf_destroy(&buf);
> +	rc = tpm_transmit_cmd(chip, buf, 0, "TPM2_ReadPublic");
> +	if (rc)
>  		return tpm_ret_to_err(rc);
> -	}
>  
>  	/* Skip TPMT_PUBLIC: */
> -	offset += tpm_buf_read_u16(&buf, &offset);
> +	offset += tpm_buf_read_u16(buf, &offset);
>  
>  	/*
>  	 * Ensure space for the length field of TPM2B_NAME and hashAlg field of
>  	 * TPMT_HA (the extra four bytes).
>  	 */
> -	if (offset + 4 > tpm_buf_length(&buf)) {
> -		tpm_buf_destroy(&buf);
> +	if (offset + 4 > tpm_buf_length(buf))
>  		return -EIO;
> -	}
>  
> -	rc = tpm_buf_read_u16(&buf, &offset);
> -	name_size_alg = name_size(&buf.data[offset]);
> +	rc = tpm_buf_read_u16(buf, &offset);
> +	name_size_alg = name_size(&buf->data[offset]);
>  
>  	if (name_size_alg < 0)
>  		return name_size_alg;
>  
> -	if (rc != name_size_alg) {
> -		tpm_buf_destroy(&buf);
> +	if (rc != name_size_alg)
>  		return -EIO;
> -	}
>  
> -	if (offset + rc > tpm_buf_length(&buf)) {
> -		tpm_buf_destroy(&buf);
> +	if (offset + rc > tpm_buf_length(buf))
>  		return -EIO;
> -	}
>  
> -	memcpy(name, &buf.data[offset], rc);
> +	memcpy(name, &buf->data[offset], rc);
>  	return name_size_alg;
>  }
>  #endif /* CONFIG_TCG_TPM2_HMAC */
> @@ -982,7 +975,6 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
>  int tpm2_start_auth_session(struct tpm_chip *chip)
>  {
>  	struct tpm2_auth *auth;
> -	struct tpm_buf buf;
>  	u32 null_key;
>  	int rc;
>  
> @@ -991,6 +983,10 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>  		return 0;
>  	}
>  
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
>  	auth = kzalloc(sizeof(*auth), GFP_KERNEL);
>  	if (!auth)
>  		return -ENOMEM;
> @@ -1001,41 +997,37 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>  
>  	auth->session = TPM_HEADER_SIZE;
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
> -	if (rc)
> -		goto out;
> -
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
>  	/* salt key handle */
> -	tpm_buf_append_u32(&buf, null_key);
> +	tpm_buf_append_u32(buf, null_key);
>  	/* bind key handle */
> -	tpm_buf_append_u32(&buf, TPM2_RH_NULL);
> +	tpm_buf_append_u32(buf, TPM2_RH_NULL);
>  	/* nonce caller */
>  	get_random_bytes(auth->our_nonce, sizeof(auth->our_nonce));
> -	tpm_buf_append_u16(&buf, sizeof(auth->our_nonce));
> -	tpm_buf_append(&buf, auth->our_nonce, sizeof(auth->our_nonce));
> +	tpm_buf_append_u16(buf, sizeof(auth->our_nonce));
> +	tpm_buf_append(buf, auth->our_nonce, sizeof(auth->our_nonce));
>  
>  	/* append encrypted salt and squirrel away unencrypted in auth */
> -	tpm_buf_append_salt(&buf, chip, auth);
> +	tpm_buf_append_salt(buf, chip, auth);
>  	/* session type (HMAC, audit or policy) */
> -	tpm_buf_append_u8(&buf, TPM2_SE_HMAC);
> +	tpm_buf_append_u8(buf, TPM2_SE_HMAC);
>  
>  	/* symmetric encryption parameters */
>  	/* symmetric algorithm */
> -	tpm_buf_append_u16(&buf, TPM_ALG_AES);
> +	tpm_buf_append_u16(buf, TPM_ALG_AES);
>  	/* bits for symmetric algorithm */
> -	tpm_buf_append_u16(&buf, AES_KEY_BITS);
> +	tpm_buf_append_u16(buf, AES_KEY_BITS);
>  	/* symmetric algorithm mode (must be CFB) */
> -	tpm_buf_append_u16(&buf, TPM_ALG_CFB);
> +	tpm_buf_append_u16(buf, TPM_ALG_CFB);
>  	/* hash algorithm for session */
> -	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
> +	tpm_buf_append_u16(buf, TPM_ALG_SHA256);
>  
> -	rc = tpm_ret_to_err(tpm_transmit_cmd(chip, &buf, 0, "StartAuthSession"));
> +	rc = tpm_ret_to_err(tpm_transmit_cmd(chip, buf, 0, "TPM2_StartAuthSession"));
>  	tpm2_flush_context(chip, null_key);
>  
>  	if (rc == TPM2_RC_SUCCESS)
> -		rc = tpm2_parse_start_auth_session(auth, &buf);
> -
> -	tpm_buf_destroy(&buf);
> +		rc = tpm2_parse_start_auth_session(auth, buf);
>  
>  	if (rc == TPM2_RC_SUCCESS) {
>  		chip->auth = auth;
> @@ -1257,18 +1249,18 @@ static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
>  			       u32 *handle, u8 *name)
>  {
>  	int rc;
> -	struct tpm_buf buf;
> -	struct tpm_buf template;
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE_PRIMARY);
> -	if (rc)
> -		return rc;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>  
> -	rc = tpm_buf_init_sized(&template);
> -	if (rc) {
> -		tpm_buf_destroy(&buf);
> -		return rc;
> -	}
> +	struct tpm_buf *template __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!template)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE_PRIMARY);
> +	tpm_buf_init_sized(template, TPM_BUFSIZE);
>  
>  	/*
>  	 * create the template.  Note: in order for userspace to
> @@ -1280,75 +1272,71 @@ static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
>  	 */
>  
>  	/* key type */
> -	tpm_buf_append_u16(&template, TPM_ALG_ECC);
> +	tpm_buf_append_u16(template, TPM_ALG_ECC);
>  
>  	/* name algorithm */
> -	tpm_buf_append_u16(&template, TPM_ALG_SHA256);
> +	tpm_buf_append_u16(template, TPM_ALG_SHA256);
>  
>  	/* object properties */
> -	tpm_buf_append_u32(&template, TPM2_OA_NULL_KEY);
> +	tpm_buf_append_u32(template, TPM2_OA_NULL_KEY);
>  
>  	/* sauth policy (empty) */
> -	tpm_buf_append_u16(&template, 0);
> +	tpm_buf_append_u16(template, 0);
>  
>  	/* BEGIN parameters: key specific; for ECC*/
>  
>  	/* symmetric algorithm */
> -	tpm_buf_append_u16(&template, TPM_ALG_AES);
> +	tpm_buf_append_u16(template, TPM_ALG_AES);
>  
>  	/* bits for symmetric algorithm */
> -	tpm_buf_append_u16(&template, AES_KEY_BITS);
> +	tpm_buf_append_u16(template, AES_KEY_BITS);
>  
>  	/* algorithm mode (must be CFB) */
> -	tpm_buf_append_u16(&template, TPM_ALG_CFB);
> +	tpm_buf_append_u16(template, TPM_ALG_CFB);
>  
>  	/* scheme (NULL means any scheme) */
> -	tpm_buf_append_u16(&template, TPM_ALG_NULL);
> +	tpm_buf_append_u16(template, TPM_ALG_NULL);
>  
>  	/* ECC Curve ID */
> -	tpm_buf_append_u16(&template, TPM2_ECC_NIST_P256);
> +	tpm_buf_append_u16(template, TPM2_ECC_NIST_P256);
>  
>  	/* KDF Scheme */
> -	tpm_buf_append_u16(&template, TPM_ALG_NULL);
> +	tpm_buf_append_u16(template, TPM_ALG_NULL);
>  
>  	/* unique: key specific; for ECC it is two zero size points */
> -	tpm_buf_append_u16(&template, 0);
> -	tpm_buf_append_u16(&template, 0);
> +	tpm_buf_append_u16(template, 0);
> +	tpm_buf_append_u16(template, 0);
>  
>  	/* END parameters */
>  
>  	/* primary handle */
> -	tpm_buf_append_u32(&buf, hierarchy);
> -	tpm_buf_append_empty_auth(&buf, TPM2_RS_PW);
> +	tpm_buf_append_u32(buf, hierarchy);
> +	tpm_buf_append_empty_auth(buf, TPM2_RS_PW);
>  
>  	/* sensitive create size is 4 for two empty buffers */
> -	tpm_buf_append_u16(&buf, 4);
> +	tpm_buf_append_u16(buf, 4);
>  
>  	/* sensitive create auth data (empty) */
> -	tpm_buf_append_u16(&buf, 0);
> +	tpm_buf_append_u16(buf, 0);
>  
>  	/* sensitive create sensitive data (empty) */
> -	tpm_buf_append_u16(&buf, 0);
> +	tpm_buf_append_u16(buf, 0);
>  
>  	/* the public template */
> -	tpm_buf_append(&buf, template.data, template.length);
> -	tpm_buf_destroy(&template);
> +	tpm_buf_append(buf, template->data, template->length);
>  
>  	/* outside info (empty) */
> -	tpm_buf_append_u16(&buf, 0);
> +	tpm_buf_append_u16(buf, 0);
>  
>  	/* creation PCR (none) */
> -	tpm_buf_append_u32(&buf, 0);
> +	tpm_buf_append_u32(buf, 0);
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 0,
> -			      "attempting to create NULL primary");
> +	rc = tpm_transmit_cmd(chip, buf, 0, "TPM2_CreatePrimary");
>  
>  	if (rc == TPM2_RC_SUCCESS)
> -		rc = tpm2_parse_create_primary(chip, &buf, handle, hierarchy,
> +		rc = tpm2_parse_create_primary(chip, buf, handle, hierarchy,
>  					       name);
>  
> -	tpm_buf_destroy(&buf);
> -
>  	return rc;
>  }
>  
> diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c
> index 60354cd53b5c..cbf86ff5931f 100644
> --- a/drivers/char/tpm/tpm2-space.c
> +++ b/drivers/char/tpm/tpm2-space.c
> @@ -71,24 +71,25 @@ void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space)
>  int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
>  		      unsigned int *offset, u32 *handle)
>  {
> -	struct tpm_buf tbuf;
>  	struct tpm2_context *ctx;
>  	unsigned int body_size;
>  	int rc;
>  
> -	rc = tpm_buf_init(&tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_LOAD);
> -	if (rc)
> -		return rc;
> +	struct tpm_buf *tbuf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!tbuf)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(tbuf, TPM_BUFSIZE);
> +	tpm_buf_reset(tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_LOAD);
>  
>  	ctx = (struct tpm2_context *)&buf[*offset];
>  	body_size = sizeof(*ctx) + be16_to_cpu(ctx->blob_size);
> -	tpm_buf_append(&tbuf, &buf[*offset], body_size);
> +	tpm_buf_append(tbuf, &buf[*offset], body_size);
>  
> -	rc = tpm_transmit_cmd(chip, &tbuf, 4, NULL);
> +	rc = tpm_transmit_cmd(chip, tbuf, 4, NULL);
>  	if (rc < 0) {
>  		dev_warn(&chip->dev, "%s: failed with a system error %d\n",
>  			 __func__, rc);
> -		tpm_buf_destroy(&tbuf);
>  		return -EFAULT;
>  	} else if (tpm2_rc_value(rc) == TPM2_RC_HANDLE ||
>  		   rc == TPM2_RC_REFERENCE_H0) {
> @@ -103,64 +104,55 @@ int tpm2_load_context(struct tpm_chip *chip, u8 *buf,
>  		 * flushed outside the space
>  		 */
>  		*handle = 0;
> -		tpm_buf_destroy(&tbuf);
>  		return -ENOENT;
>  	} else if (tpm2_rc_value(rc) == TPM2_RC_INTEGRITY) {
> -		tpm_buf_destroy(&tbuf);
>  		return -EINVAL;
>  	} else if (rc > 0) {
>  		dev_warn(&chip->dev, "%s: failed with a TPM error 0x%04X\n",
>  			 __func__, rc);
> -		tpm_buf_destroy(&tbuf);
>  		return -EFAULT;
>  	}
>  
> -	*handle = be32_to_cpup((__be32 *)&tbuf.data[TPM_HEADER_SIZE]);
> +	*handle = be32_to_cpup((__be32 *)&tbuf->data[TPM_HEADER_SIZE]);
>  	*offset += body_size;
> -
> -	tpm_buf_destroy(&tbuf);
>  	return 0;
>  }
>  
>  int tpm2_save_context(struct tpm_chip *chip, u32 handle, u8 *buf,
>  		      unsigned int buf_size, unsigned int *offset)
>  {
> -	struct tpm_buf tbuf;
>  	unsigned int body_size;
>  	int rc;
>  
> -	rc = tpm_buf_init(&tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_SAVE);
> -	if (rc)
> -		return rc;
> +	struct tpm_buf *tbuf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!tbuf)
> +		return -ENOMEM;
>  
> -	tpm_buf_append_u32(&tbuf, handle);
> +	tpm_buf_init(tbuf, TPM_BUFSIZE);
> +	tpm_buf_reset(tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_SAVE);
> +	tpm_buf_append_u32(tbuf, handle);
>  
> -	rc = tpm_transmit_cmd(chip, &tbuf, 0, NULL);
> +	rc = tpm_transmit_cmd(chip, tbuf, 0, NULL);
>  	if (rc < 0) {
>  		dev_warn(&chip->dev, "%s: failed with a system error %d\n",
>  			 __func__, rc);
> -		tpm_buf_destroy(&tbuf);
>  		return -EFAULT;
>  	} else if (tpm2_rc_value(rc) == TPM2_RC_REFERENCE_H0) {
> -		tpm_buf_destroy(&tbuf);
>  		return -ENOENT;
>  	} else if (rc) {
>  		dev_warn(&chip->dev, "%s: failed with a TPM error 0x%04X\n",
>  			 __func__, rc);
> -		tpm_buf_destroy(&tbuf);
>  		return -EFAULT;
>  	}
>  
> -	body_size = tpm_buf_length(&tbuf) - TPM_HEADER_SIZE;
> +	body_size = tpm_buf_length(tbuf) - TPM_HEADER_SIZE;
>  	if ((*offset + body_size) > buf_size) {
>  		dev_warn(&chip->dev, "%s: out of backing storage\n", __func__);
> -		tpm_buf_destroy(&tbuf);
>  		return -ENOMEM;
>  	}
>  
> -	memcpy(&buf[*offset], &tbuf.data[TPM_HEADER_SIZE], body_size);
> +	memcpy(&buf[*offset], &tbuf->data[TPM_HEADER_SIZE], body_size);
>  	*offset += body_size;
> -	tpm_buf_destroy(&tbuf);
>  	return 0;
>  }
>  
> diff --git a/drivers/char/tpm/tpm_vtpm_proxy.c b/drivers/char/tpm/tpm_vtpm_proxy.c
> index 0818bb517805..682dfc93845d 100644
> --- a/drivers/char/tpm/tpm_vtpm_proxy.c
> +++ b/drivers/char/tpm/tpm_vtpm_proxy.c
> @@ -395,40 +395,36 @@ static bool vtpm_proxy_tpm_req_canceled(struct tpm_chip  *chip, u8 status)
>  
>  static int vtpm_proxy_request_locality(struct tpm_chip *chip, int locality)
>  {
> -	struct tpm_buf buf;
>  	int rc;
>  	const struct tpm_header *header;
>  	struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
>  
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(buf, TPM_BUFSIZE);
>  	if (chip->flags & TPM_CHIP_FLAG_TPM2)
> -		rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS,
> -				  TPM2_CC_SET_LOCALITY);
> +		tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_SET_LOCALITY);
>  	else
> -		rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND,
> -				  TPM_ORD_SET_LOCALITY);
> -	if (rc)
> -		return rc;
> -	tpm_buf_append_u8(&buf, locality);
> +		tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SET_LOCALITY);
> +
> +	tpm_buf_append_u8(buf, locality);
>  
>  	proxy_dev->state |= STATE_DRIVER_COMMAND;
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to set locality");
> +	rc = tpm_transmit_cmd(chip, buf, 0, "attempting to set locality");
>  
>  	proxy_dev->state &= ~STATE_DRIVER_COMMAND;
>  
> -	if (rc < 0) {
> -		locality = rc;
> -		goto out;
> -	}
> +	if (rc < 0)
> +		return rc;
>  
> -	header = (const struct tpm_header *)buf.data;
> +	header = (const struct tpm_header *)buf->data;
>  	rc = be32_to_cpu(header->return_code);
>  	if (rc)
>  		locality = -1;
>  
> -out:
> -	tpm_buf_destroy(&buf);
> -
>  	return locality;
>  }
>  
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 1e0585e45371..42e2a091f43d 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -25,7 +25,8 @@
>  #include <crypto/hash_info.h>
>  #include <crypto/aes.h>
>  
> -#define TPM_DIGEST_SIZE 20	/* Max TPM v1.2 PCR size */
> +#define TPM_DIGEST_SIZE		20	/* Max TPM v1.2 PCR size */
> +#define TPM_BUFSIZE		4096
>  
>  #define TPM2_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE
>  #define TPM2_MAX_PCR_BANKS	8
> @@ -376,13 +377,15 @@ enum tpm_buf_flags {
>  };
>  
>  /*
> - * A string buffer type for constructing TPM commands.
> + * A buffer for constructing and parsing TPM commands, responses and sized
> + * (TPM2B) buffers.
>   */
>  struct tpm_buf {
> -	u32 flags;
> -	u32 length;
> -	u8 *data;
> +	u8 flags;
>  	u8 handles;
> +	u16 length;
> +	u16 capacity;
> +	u8 data[];
>  };
>  
>  enum tpm2_object_attributes {
> @@ -413,12 +416,11 @@ struct tpm2_hash {
>  	unsigned int tpm_id;
>  };
>  
> -int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
> +void tpm_buf_init(struct tpm_buf *buf, u16 buf_size);
> +void tpm_buf_init_sized(struct tpm_buf *buf, u16 buf_size);
>  void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal);
> -int tpm_buf_init_sized(struct tpm_buf *buf);
>  void tpm_buf_reset_sized(struct tpm_buf *buf);
> -void tpm_buf_destroy(struct tpm_buf *buf);
> -u32 tpm_buf_length(struct tpm_buf *buf);
> +u16 tpm_buf_length(struct tpm_buf *buf);
>  void tpm_buf_append(struct tpm_buf *buf, const u8 *new_data, u16 new_length);
>  void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
>  void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
> diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> index 636acb66a4f6..759c1ecb0435 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -310,9 +310,10 @@ static int TSS_checkhmac2(unsigned char *buffer,
>   * For key specific tpm requests, we will generate and send our
>   * own TPM command packets using the drivers send function.
>   */
> -static int trusted_tpm_send(unsigned char *cmd, size_t buflen)
> +static int trusted_tpm_send(void *cmd, size_t cmd_len)
>  {
> -	struct tpm_buf buf;
> +	u8 buf_data[512];
> +	struct tpm_buf *buf = (struct tpm_buf *)buf_data;
>  	int rc;
>  
>  	if (!chip)
> @@ -322,11 +323,10 @@ static int trusted_tpm_send(unsigned char *cmd, size_t buflen)
>  	if (rc)
>  		return rc;
>  
> -	buf.flags = 0;
> -	buf.length = buflen;
> -	buf.data = cmd;
> +	tpm_buf_init(buf, sizeof(buf_data));
> +	tpm_buf_append(buf, cmd, cmd_len);
>  	dump_tpm_buf(cmd);
> -	rc = tpm_transmit_cmd(chip, &buf, 4, "sending data");
> +	rc = tpm_transmit_cmd(chip, buf, 4, "sending data");
>  	dump_tpm_buf(cmd);
>  
>  	if (rc > 0)
> @@ -624,23 +624,23 @@ static int tpm_unseal(struct tpm_buf *tb,
>  static int key_seal(struct trusted_key_payload *p,
>  		    struct trusted_key_options *o)
>  {
> -	struct tpm_buf tb;
>  	int ret;
>  
> -	ret = tpm_buf_init(&tb, 0, 0);
> -	if (ret)
> -		return ret;
> +	struct tpm_buf *tb __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!tb)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(tb, TPM_BUFSIZE);
>  
>  	/* include migratable flag at end of sealed key */
>  	p->key[p->key_len] = p->migratable;
>  
> -	ret = tpm_seal(&tb, o->keytype, o->keyhandle, o->keyauth,
> +	ret = tpm_seal(tb, o->keytype, o->keyhandle, o->keyauth,
>  		       p->key, p->key_len + 1, p->blob, &p->blob_len,
>  		       o->blobauth, o->pcrinfo, o->pcrinfo_len);
>  	if (ret < 0)
>  		pr_info("srkseal failed (%d)\n", ret);
>  
> -	tpm_buf_destroy(&tb);
>  	return ret;
>  }
>  
> @@ -650,14 +650,15 @@ static int key_seal(struct trusted_key_payload *p,
>  static int key_unseal(struct trusted_key_payload *p,
>  		      struct trusted_key_options *o)
>  {
> -	struct tpm_buf tb;
>  	int ret;
>  
> -	ret = tpm_buf_init(&tb, 0, 0);
> -	if (ret)
> -		return ret;
> +	struct tpm_buf *tb __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!tb)
> +		return -ENOMEM;
> +
> +	tpm_buf_init(tb, TPM_BUFSIZE);
>  
> -	ret = tpm_unseal(&tb, o->keyhandle, o->keyauth, p->blob, p->blob_len,
> +	ret = tpm_unseal(tb, o->keyhandle, o->keyauth, p->blob, p->blob_len,
>  			 o->blobauth, p->key, &p->key_len);
>  	if (ret < 0)
>  		pr_info("srkunseal failed (%d)\n", ret);
> @@ -665,7 +666,6 @@ static int key_unseal(struct trusted_key_payload *p,
>  		/* pull migratable flag out of sealed key */
>  		p->migratable = p->key[--p->key_len];
>  
> -	tpm_buf_destroy(&tb);
>  	return ret;
>  }
>  
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index fdba641fefdb..fb76c4ea496f 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -234,7 +234,6 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>  		      struct trusted_key_options *options)
>  {
>  	off_t offset = TPM_HEADER_SIZE;
> -	struct tpm_buf buf, sized;
>  	int blob_len = 0;
>  	int hash;
>  	u32 flags;
> @@ -255,97 +254,99 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>  	if (rc)
>  		goto out_put;
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
> -	if (rc) {
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf) {
> +		rc = -ENOMEM;
>  		tpm2_end_auth_session(chip);
>  		goto out_put;
>  	}
>  
> -	rc = tpm_buf_init_sized(&sized);
> -	if (rc) {
> -		tpm_buf_destroy(&buf);
> -		tpm2_end_auth_session(chip);
> -		goto out_put;
> -	}
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
>  
> -	rc = tpm_buf_append_name(chip, &buf, options->keyhandle, NULL);
> +	rc = tpm_buf_append_name(chip, buf, options->keyhandle, NULL);
>  	if (rc)
> -		goto out;
> +		goto out_put;
>  
> -	tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_DECRYPT,
> +	tpm_buf_append_hmac_session(chip, buf, TPM2_SA_DECRYPT,
>  				    options->keyauth, TPM_DIGEST_SIZE);
>  
> +	struct tpm_buf *sized __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!sized) {
> +		rc = -ENOMEM;
> +		tpm2_end_auth_session(chip);
> +		goto out_put;
> +	}
> +
>  	/* sensitive */
> -	tpm_buf_append_u16(&sized, options->blobauth_len);
> +	tpm_buf_init_sized(sized, TPM_BUFSIZE);
> +	tpm_buf_append_u16(sized, options->blobauth_len);
>  
>  	if (options->blobauth_len)
> -		tpm_buf_append(&sized, options->blobauth, options->blobauth_len);
> +		tpm_buf_append(sized, options->blobauth, options->blobauth_len);
>  
> -	tpm_buf_append_u16(&sized, payload->key_len);
> -	tpm_buf_append(&sized, payload->key, payload->key_len);
> -	tpm_buf_append(&buf, sized.data, sized.length);
> +	tpm_buf_append_u16(sized, payload->key_len);
> +	tpm_buf_append(sized, payload->key, payload->key_len);
> +	tpm_buf_append(buf, sized->data, sized->length);
>  
>  	/* public */
> -	tpm_buf_reset_sized(&sized);
> -	tpm_buf_append_u16(&sized, TPM_ALG_KEYEDHASH);
> -	tpm_buf_append_u16(&sized, hash);
> +	tpm_buf_init_sized(sized, TPM_BUFSIZE);
> +	tpm_buf_append_u16(sized, TPM_ALG_KEYEDHASH);
> +	tpm_buf_append_u16(sized, hash);
>  
>  	/* key properties */
>  	flags = 0;
>  	flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH;
>  	flags |= payload->migratable ? 0 : (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT);
> -	tpm_buf_append_u32(&sized, flags);
> +	tpm_buf_append_u32(sized, flags);
>  
>  	/* policy */
> -	tpm_buf_append_u16(&sized, options->policydigest_len);
> +	tpm_buf_append_u16(sized, options->policydigest_len);
>  	if (options->policydigest_len)
> -		tpm_buf_append(&sized, options->policydigest, options->policydigest_len);
> +		tpm_buf_append(sized, options->policydigest, options->policydigest_len);
>  
>  	/* public parameters */
> -	tpm_buf_append_u16(&sized, TPM_ALG_NULL);
> -	tpm_buf_append_u16(&sized, 0);
> +	tpm_buf_append_u16(sized, TPM_ALG_NULL);
> +	tpm_buf_append_u16(sized, 0);
>  
> -	tpm_buf_append(&buf, sized.data, sized.length);
> +	tpm_buf_append(buf, sized->data, sized->length);
>  
>  	/* outside info */
> -	tpm_buf_append_u16(&buf, 0);
> +	tpm_buf_append_u16(buf, 0);
>  
>  	/* creation PCR */
> -	tpm_buf_append_u32(&buf, 0);
> +	tpm_buf_append_u32(buf, 0);
>  
> -	if (buf.flags & TPM_BUF_INVALID) {
> +	if (buf->flags & TPM_BUF_INVALID) {
>  		rc = -E2BIG;
>  		tpm2_end_auth_session(chip);
>  		goto out;
>  	}
>  
> -	rc = tpm_buf_fill_hmac_session(chip, &buf);
> +	rc = tpm_buf_fill_hmac_session(chip, buf);
>  	if (rc)
>  		goto out;
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 4, "sealing data");
> -	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
> +	rc = tpm_transmit_cmd(chip, buf, 4, "sealing data");
> +	rc = tpm_buf_check_hmac_response(chip, buf, rc);
>  	if (rc)
>  		goto out;
>  
> -	blob_len = tpm_buf_read_u32(&buf, &offset);
> -	if (blob_len > MAX_BLOB_SIZE || buf.flags & TPM_BUF_INVALID) {
> +	blob_len = tpm_buf_read_u32(buf, &offset);
> +	if (blob_len > MAX_BLOB_SIZE || buf->flags & TPM_BUF_INVALID) {
>  		rc = -E2BIG;
>  		goto out;
>  	}
> -	if (buf.length - offset < blob_len) {
> +	if (buf->length - offset < blob_len) {
>  		rc = -EFAULT;
>  		goto out;
>  	}
>  
> -	blob_len = tpm2_key_encode(payload, options, &buf.data[offset], blob_len);
> +	blob_len = tpm2_key_encode(payload, options, &buf->data[offset], blob_len);
>  	if (blob_len < 0)
>  		rc = blob_len;
>  
>  out:
> -	tpm_buf_destroy(&sized);
> -	tpm_buf_destroy(&buf);
> -
>  	if (!rc)
>  		payload->blob_len = blob_len;
>  
> @@ -373,7 +374,6 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>  			 u32 *blob_handle)
>  {
>  	u8 *blob_ref __free(kfree) = NULL;
> -	struct tpm_buf buf;
>  	unsigned int private_len;
>  	unsigned int public_len;
>  	unsigned int blob_len;
> @@ -427,39 +427,38 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>  	if (rc)
>  		return rc;
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
> -	if (rc) {
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf) {
>  		tpm2_end_auth_session(chip);
> -		return rc;
> +		return -ENOMEM;
>  	}
>  
> -	rc = tpm_buf_append_name(chip, &buf, options->keyhandle, NULL);
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
> +
> +	rc = tpm_buf_append_name(chip, buf, options->keyhandle, NULL);
>  	if (rc)
> -		goto out;
> +		return rc;
>  
> -	tpm_buf_append_hmac_session(chip, &buf, 0, options->keyauth,
> +	tpm_buf_append_hmac_session(chip, buf, 0, options->keyauth,
>  				    TPM_DIGEST_SIZE);
>  
> -	tpm_buf_append(&buf, blob, blob_len);
> +	tpm_buf_append(buf, blob, blob_len);
>  
> -	if (buf.flags & TPM_BUF_INVALID) {
> -		rc = -E2BIG;
> +	if (buf->flags & TPM_BUF_INVALID) {
>  		tpm2_end_auth_session(chip);
> -		goto out;
> +		return -E2BIG;
>  	}
>  
> -	rc = tpm_buf_fill_hmac_session(chip, &buf);
> +	rc = tpm_buf_fill_hmac_session(chip, buf);
>  	if (rc)
> -		goto out;
> +		return rc;
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 4, "loading blob");
> -	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
> +	rc = tpm_transmit_cmd(chip, buf, 4, "loading blob");
> +	rc = tpm_buf_check_hmac_response(chip, buf, rc);
>  	if (!rc)
>  		*blob_handle = be32_to_cpup(
> -			(__be32 *) &buf.data[TPM_HEADER_SIZE]);
> -
> -out:
> -	tpm_buf_destroy(&buf);
> +			(__be32 *)&buf->data[TPM_HEADER_SIZE]);
>  
>  	return tpm_ret_to_err(rc);
>  }
> @@ -482,28 +481,28 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>  			   u32 blob_handle)
>  {
>  	struct tpm_header *head;
> -	struct tpm_buf buf;
>  	u16 data_len;
>  	int offset;
>  	u8 *data;
>  	int rc;
>  
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
>  	rc = tpm2_start_auth_session(chip);
>  	if (rc)
>  		return rc;
>  
> -	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
> -	if (rc) {
> -		tpm2_end_auth_session(chip);
> -		return rc;
> -	}
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
>  
> -	rc = tpm_buf_append_name(chip, &buf, options->keyhandle, NULL);
> +	rc = tpm_buf_append_name(chip, buf, options->keyhandle, NULL);
>  	if (rc)
> -		goto out;
> +		return rc;
>  
>  	if (!options->policyhandle) {
> -		tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_ENCRYPT,
> +		tpm_buf_append_hmac_session(chip, buf, TPM2_SA_ENCRYPT,
>  					    options->blobauth,
>  					    options->blobauth_len);
>  	} else {
> @@ -518,39 +517,36 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>  		 * could repeat our actions with the exfiltrated
>  		 * password.
>  		 */
> -		tpm2_buf_append_auth(&buf, options->policyhandle,
> +		tpm2_buf_append_auth(buf, options->policyhandle,
>  				     NULL /* nonce */, 0, 0,
>  				     options->blobauth, options->blobauth_len);
> +
>  		if (tpm2_chip_auth(chip)) {
> -			tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_ENCRYPT, NULL, 0);
> +			tpm_buf_append_hmac_session(chip, buf, TPM2_SA_ENCRYPT, NULL, 0);
>  		} else  {
> -			offset = buf.handles * 4 + TPM_HEADER_SIZE;
> -			head = (struct tpm_header *)buf.data;
> -			if (tpm_buf_length(&buf) == offset)
> +			offset = buf->handles * 4 + TPM_HEADER_SIZE;
> +			head = (struct tpm_header *)buf->data;
> +			if (tpm_buf_length(buf) == offset)
>  				head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
>  		}
>  	}
>  
> -	rc = tpm_buf_fill_hmac_session(chip, &buf);
> +	rc = tpm_buf_fill_hmac_session(chip, buf);
>  	if (rc)
> -		goto out;
> +		return rc;
>  
> -	rc = tpm_transmit_cmd(chip, &buf, 6, "unsealing");
> -	rc = tpm_buf_check_hmac_response(chip, &buf, rc);
> +	rc = tpm_transmit_cmd(chip, buf, 6, "unsealing");
> +	rc = tpm_buf_check_hmac_response(chip, buf, rc);
>  
>  	if (!rc) {
>  		data_len = be16_to_cpup(
> -			(__be16 *) &buf.data[TPM_HEADER_SIZE + 4]);
> -		if (data_len < MIN_KEY_SIZE ||  data_len > MAX_KEY_SIZE) {
> -			rc = -EFAULT;
> -			goto out;
> -		}
> +			(__be16 *)&buf->data[TPM_HEADER_SIZE + 4]);
> +		if (data_len < MIN_KEY_SIZE ||  data_len > MAX_KEY_SIZE)
> +			return -EFAULT;
>  
> -		if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 6 + data_len) {
> -			rc = -EFAULT;
> -			goto out;
> -		}
> -		data = &buf.data[TPM_HEADER_SIZE + 6];
> +		if (tpm_buf_length(buf) < TPM_HEADER_SIZE + 6 + data_len)
> +			return -EFAULT;
> +		data = &buf->data[TPM_HEADER_SIZE + 6];
>  
>  		if (payload->old_format) {
>  			/* migratable flag is at the end of the key */
> @@ -567,8 +563,6 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>  		}
>  	}
>  
> -out:
> -	tpm_buf_destroy(&buf);
>  	return tpm_ret_to_err(rc);
>  }
>  
> -- 
> 2.39.5
> 

I applied these patches to my master branch for these reasons:

1. It is a change for better, as managed allocations objectively
   deliver safer memory semantics overall.
2. The patch has been in my testing cycle for months now already.
   I've tested *everything* with it and without it in order to
   stress the change a bit.
3. Despite being large change it does fit to the "single logical
   change" category. It would only make things more dissolved if
   it was split in any possible way.
4. It's a great idea roughly base it on 6.19-rc1 so that it can
   be applied easily top of the mainline release (if wanted).

I will appreciate any testing results etc. and stay put on fixing
any possible issues. Also, e.g. tested-by tags can be added up
until the first pull request for 6.20.

BR, Jarkko