Re: [PATCH] tpm-buf: memory-safe allocations

[Srish Srinivasan <ssrish@linux.ibm.com>]

Tested on emulated TPM 1.2 and TPM 2.0 backends.

Coverage:
   TPM 1.2: sysfs and trusted-key paths
   TPM 2.0: PCR, random, and trusted-key paths

Tested-by: Srish Srinivasan <ssrish@linux.ibm.com>

On 5/22/26 7:05 AM, 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.
>
> Cc: Arun Menon <armenon@redhat.com>
> Cc: Daniel P. Smith <dpsmith@apertussolutions.com>
> Cc: Alec Brown <alec.r.brown@oracle.com>
> Cc: Ross Philipson <ross.philipson@gmail.com>
> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@opinsys.com>
> ---
> Rebased the managed allocations patch, which has been probably like a
> year in circulation.
>   drivers/char/tpm/tpm-buf.c                | 122 ++++++----
>   drivers/char/tpm/tpm-sysfs.c              |  17 +-
>   drivers/char/tpm/tpm.h                    |   1 -
>   drivers/char/tpm/tpm1-cmd.c               | 150 ++++++------
>   drivers/char/tpm/tpm2-cmd.c               | 277 +++++++++++-----------
>   drivers/char/tpm/tpm2-sessions.c          | 149 ++++++------
>   drivers/char/tpm/tpm2-space.c             |  44 ++--
>   drivers/char/tpm/tpm_vtpm_proxy.c         |  30 +--
>   include/linux/tpm.h                       |  18 +-
>   security/keys/trusted-keys/trusted_tpm1.c |  44 ++--
>   security/keys/trusted-keys/trusted_tpm2.c | 165 ++++++-------
>   11 files changed, 505 insertions(+), 512 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index dc882fc9fa9e..b16d824ef0af 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -7,82 +7,110 @@
>   #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_OVERFLOW;
> +		}
> +	} 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_OVERFLOW;
> +		}
> +	}
>   }
> -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_OVERFLOW)
> +		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_OVERFLOW)
> +		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
> @@ -90,7 +118,7 @@ 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)
>   {
>   	return buf->length;
>   }
> @@ -104,11 +132,13 @@ 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;
> +
>   	/* Return silently if overflow has already happened. */
>   	if (buf->flags & TPM_BUF_OVERFLOW)
>   		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_OVERFLOW;
>   		return;
> diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
> index 94231f052ea7..1de03cf340b3 100644
> --- a/drivers/char/tpm/tpm-sysfs.c
> +++ b/drivers/char/tpm/tpm-sysfs.c
> @@ -32,28 +32,31 @@ 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) = NULL;
>
>   	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))
> +	tpm_buf = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!tpm_buf)
>   		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,
> +	if (tpm_transmit_cmd(chip, tpm_buf, READ_PUBEK_RESULT_MIN_BODY_SIZE,
>   			     "attempting to read the PUBEK"))
> -		goto out_buf;
> +		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 +74,6 @@ 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 87d68ddf270a..03f5346343ab 100644
> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -33,7 +33,6 @@
>   #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..6facc3de2c46 100644
> --- a/drivers/char/tpm/tpm1-cmd.c
> +++ b/drivers/char/tpm/tpm1-cmd.c
> @@ -323,20 +323,18 @@ 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;
> +	struct tpm_buf *buf __free(kfree) = NULL;
>
>   	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);
> +	buf = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>
> -	rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to start the TPM");
> -	tpm_buf_destroy(&buf);
> -	return rc;
> +	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, "attempting to start the TPM");
>   }
>
>   int tpm1_get_timeouts(struct tpm_chip *chip)
> @@ -463,50 +461,47 @@ 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);
> @@ -530,21 +525,24 @@ struct tpm1_get_random_out {
>   int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>   {
>   	struct tpm1_get_random_out *out;
> +	struct tpm_buf *buf __free(kfree) = NULL;
>   	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;
> +	buf = 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_RANDOM);
>
>   	do {
> -		tpm_buf_append_u32(&buf, num_bytes);
> +		tpm_buf_append_u32(buf, num_bytes);
>
> -		rc = tpm_transmit_cmd(chip, &buf, sizeof(out->rng_data_len),
> +		rc = tpm_transmit_cmd(chip, buf, sizeof(out->rng_data_len),
>   				      "attempting get random");
>   		if (rc) {
>   			if (rc > 0)
> @@ -552,7 +550,7 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>   			goto out;
>   		}
>
> -		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) {
> @@ -560,8 +558,8 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>   			goto out;
>   		}
>
> -		if (tpm_buf_length(&buf) < TPM_HEADER_SIZE +
> -					   sizeof(out->rng_data_len) + recd) {
> +		if (tpm_buf_length(buf) < TPM_HEADER_SIZE +
> +					  sizeof(out->rng_data_len) + recd) {
>   			rc = -EFAULT;
>   			goto out;
>   		}
> @@ -571,41 +569,36 @@ int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>   		total += recd;
>   		num_bytes -= recd;
>
> -		tpm_buf_reset(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_RANDOM);
> +		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,
> +	rc = tpm_transmit_cmd(chip, buf, TPM_DIGEST_SIZE,
>   			      "attempting to read a pcr value");
>   	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 (tpm_buf_length(buf) < 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 +612,13 @@ 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;
> +	struct tpm_buf *buf __free(kfree) = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>
> -	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_CONTINUE_SELFTEST);
> -	if (rc)
> -		return rc;
> -
> -	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, "continue selftest");
>   }
>
>   /**
> @@ -742,22 +732,24 @@ 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;
> +	struct tpm_buf *buf __free(kfree) = NULL;
>   	int rc;
>
> -
>   	/* 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");
> +	buf = 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_SAVESTATE);
>
> -	rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_SAVESTATE);
> -	if (rc)
> -		return rc;
>   	/* 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 +764,7 @@ 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 +774,6 @@ 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 52ee350da867..f619ce390f6d 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -119,12 +119,13 @@ 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) = NULL;
> +
>   	if (pcr_idx >= TPM2_PLATFORM_PCR)
>   		return -EINVAL;
>
> @@ -139,36 +140,35 @@ 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;
> +	buf = 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_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, "attempting to read a pcr value");
>   	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 -EINVAL;
>
>   	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 +184,54 @@ 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) = NULL;
> +
>   	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) {
> +	buf = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf) {
>   		if (!disable_pcr_integrity)
>   			tpm2_end_auth_session(chip);
> -		return rc;
> +		return -ENOMEM;
>   	}
>
> +	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(chip, &buf, pcr_idx);
> -		tpm_buf_append_auth(chip, &buf, NULL, 0);
> +		tpm_buf_append_handle(chip, 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 (!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");
> +	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);
> -
> -	tpm_buf_destroy(&buf);
> +		rc = tpm_buf_check_hmac_response(chip, buf, rc);
>
>   	return rc;
>   }
> @@ -258,7 +256,6 @@ 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;
> @@ -267,6 +264,8 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>   	u8 *dest_ptr = dest;
>   	off_t offset;
>
> +	struct tpm_buf *buf __free(kfree) = NULL;
> +
>   	if (!num_bytes || max > TPM_MAX_RNG_DATA)
>   		return -EINVAL;
>
> @@ -274,50 +273,52 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
>   	if (err)
>   		return err;
>
> -	err = tpm_buf_init(&buf, 0, 0);
> -	if (err) {
> +	buf = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf) {
>   		tpm2_end_auth_session(chip);
> -		return err;
> +		return -ENOMEM;
>   	}
>
> +	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);
> +		tpm_buf_append_u16(buf, num_bytes);
> +		err = tpm_buf_fill_hmac_session(chip, buf);
>   		if (err)
>   			goto out;
>
> -		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);
> +		err = tpm_buf_check_hmac_response(chip, buf, err);
>   		if (err) {
>   			if (err > 0)
>   				err = -EIO;
>   			goto out;
>   		}
>
> -		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) {
> @@ -331,11 +332,8 @@ 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;
>   }
> @@ -347,20 +345,18 @@ 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, "flushing context");
>   }
>   EXPORT_SYMBOL_GPL(tpm2_flush_context);
>
> @@ -387,19 +383,21 @@ 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];
> +			&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
> @@ -411,7 +409,6 @@ 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);
> @@ -428,15 +425,14 @@ 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, "stopping the TPM");
>   }
>
>   /**
> @@ -454,20 +450,21 @@ 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;
> +		struct tpm_buf *buf __free(kfree) = NULL;
>
> -		tpm_buf_append_u8(&buf, full);
> -		rc = tpm_transmit_cmd(chip, &buf, 0,
> -				      "attempting the self test");
> -		tpm_buf_destroy(&buf);
> +		buf = 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);
> +		tpm_buf_append_u8(buf, full);
> +		rc = tpm_transmit_cmd(chip, buf, 0,
> +				      "attempting the self test");
>   		if (rc == TPM2_RC_TESTING)
>   			rc = TPM2_RC_SUCCESS;
>   		if (rc == TPM2_RC_INITIALIZE || rc == TPM2_RC_SUCCESS)
> @@ -492,23 +489,24 @@ 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);
> @@ -548,7 +546,6 @@ 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;
> @@ -560,20 +557,22 @@ 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, "get tpm pcr allocation");
>   	if (rc)
>   		goto out;
>
>   	nr_possible_banks = be32_to_cpup(
> -		(__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
> +		(__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);
> @@ -581,10 +580,10 @@ ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>   		goto out;
>   	}
>
> -	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 +
> @@ -617,20 +616,19 @@ ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
>
>   	chip->nr_allocated_banks = nr_alloc_banks;
>   out:
> -	tpm_buf_destroy(&buf);
> -
>   	return rc;
>   }
>
>   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) = NULL;
> +
>   	rc = tpm2_get_tpm_pt(chip, TPM_PT_TOTAL_COMMANDS, &nr_commands, NULL);
>   	if (rc)
>   		goto out;
> @@ -647,30 +645,31 @@ 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)
> +	buf = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf) {
> +		rc = -ENOMEM;
>   		goto out;
> +	}
>
> -	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_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);
>
> -	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])) {
> +	    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;
> @@ -682,8 +681,6 @@ int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip)
>   		}
>   	}
>
> -	tpm_buf_destroy(&buf);
> -
>   out:
>   	if (rc > 0)
>   		rc = -ENODEV;
> @@ -704,20 +701,18 @@ EXPORT_SYMBOL_GPL(tpm2_get_cc_attrs_tbl);
>
>   static int tpm2_startup(struct tpm_chip *chip)
>   {
> -	struct tpm_buf buf;
> -	int rc;
> +	struct tpm_buf *buf __free(kfree) = NULL;
>
>   	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);
> +	buf = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>
> -	return rc;
> +	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, "attempting to start the TPM");
>   }
>
>   /**
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 795cd99dc6fe..b6a93db5a5ee 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -167,8 +167,8 @@ 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;
> +	struct tpm_buf *buf __free(kfree) = NULL;
>   	int rc, name_size_alg;
> -	struct tpm_buf buf;
>
>   	if (mso != TPM2_MSO_PERSISTENT && mso != TPM2_MSO_VOLATILE &&
>   	    mso != TPM2_MSO_NVRAM) {
> @@ -176,50 +176,40 @@ 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;
> +	buf = 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]);
>
> -	if (name_size_alg < 0) {
> -		tpm_buf_destroy(&buf);
> +	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);
> -	tpm_buf_destroy(&buf);
> +	memcpy(name, &buf->data[offset], rc);
>   	return name_size_alg;
>   }
>   #endif /* CONFIG_TCG_TPM2_HMAC */
> @@ -987,8 +977,8 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
>    */
>   int tpm2_start_auth_session(struct tpm_chip *chip)
>   {
> +	struct tpm_buf *buf __free(kfree) = NULL;
>   	struct tpm2_auth *auth;
> -	struct tpm_buf buf;
>   	u32 null_key;
>   	int rc;
>
> @@ -1007,41 +997,43 @@ 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)
> +	buf = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf) {
> +		rc = -ENOMEM;
>   		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, "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;
> @@ -1262,19 +1254,21 @@ static int tpm2_parse_create_primary(struct tpm_chip *chip, struct tpm_buf *buf,
>   static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
>   			       u32 *handle, u8 *name)
>   {
> +	struct tpm_buf *template __free(kfree) = NULL;
> +	struct tpm_buf *buf __free(kfree) = NULL;
>   	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;
> +	buf = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
>
> -	rc = tpm_buf_init_sized(&template);
> -	if (rc) {
> -		tpm_buf_destroy(&buf);
> -		return rc;
> -	}
> +	template = 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
> @@ -1286,75 +1280,72 @@ 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,
> +	rc = tpm_transmit_cmd(chip, buf, 0,
>   			      "attempting to create NULL primary");
>
>   	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 7bb0f4d4a2ed..b81fd2a537df 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 202da079d500..14d75c1482d6 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -26,6 +26,7 @@
>   #include <crypto/aes.h>
>
>   #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
> @@ -378,13 +379,15 @@ 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;
> +	u16 length;
> +	u16 capacity;
>   	u8 handles;
> +	u8 data[];
>   };
>
>   enum tpm2_object_attributes {
> @@ -415,12 +418,11 @@ 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 13513819991e..6e03fa7227e4 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -317,9 +317,8 @@ 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(struct tpm_buf *buf)
>   {
> -	struct tpm_buf buf;
>   	int rc;
>
>   	if (!chip)
> @@ -329,12 +328,9 @@ static int trusted_tpm_send(unsigned char *cmd, size_t buflen)
>   	if (rc)
>   		return rc;
>
> -	buf.flags = 0;
> -	buf.length = buflen;
> -	buf.data = cmd;
> -	dump_tpm_buf(cmd);
> -	rc = tpm_transmit_cmd(chip, &buf, 4, "sending data");
> -	dump_tpm_buf(cmd);
> +	dump_tpm_buf(buf->data);
> +	rc = tpm_transmit_cmd(chip, buf, 4, "sending data");
> +	dump_tpm_buf(buf->data);
>
>   	if (rc > 0)
>   		/* TPM error */
> @@ -380,7 +376,7 @@ static int osap(struct tpm_buf *tb, struct osapsess *s,
>   	tpm_buf_append_u32(tb, handle);
>   	tpm_buf_append(tb, ononce, TPM_NONCE_SIZE);
>
> -	ret = trusted_tpm_send(tb->data, tb->length);
> +	ret = trusted_tpm_send(tb);
>   	if (ret < 0)
>   		return ret;
>
> @@ -404,7 +400,7 @@ static int oiap(struct tpm_buf *tb, uint32_t *handle, unsigned char *nonce)
>   		return -ENODEV;
>
>   	tpm_buf_reset(tb, TPM_TAG_RQU_COMMAND, TPM_ORD_OIAP);
> -	ret = trusted_tpm_send(tb->data, tb->length);
> +	ret = trusted_tpm_send(tb);
>   	if (ret < 0)
>   		return ret;
>
> @@ -513,7 +509,7 @@ static int tpm_seal(struct tpm_buf *tb, uint16_t keytype,
>   	tpm_buf_append_u8(tb, cont);
>   	tpm_buf_append(tb, td->pubauth, SHA1_DIGEST_SIZE);
>
> -	ret = trusted_tpm_send(tb->data, tb->length);
> +	ret = trusted_tpm_send(tb);
>   	if (ret < 0)
>   		goto out;
>
> @@ -604,7 +600,7 @@ static int tpm_unseal(struct tpm_buf *tb,
>   	tpm_buf_append_u8(tb, cont);
>   	tpm_buf_append(tb, authdata2, SHA1_DIGEST_SIZE);
>
> -	ret = trusted_tpm_send(tb->data, tb->length);
> +	ret = trusted_tpm_send(tb);
>   	if (ret < 0) {
>   		pr_info("authhmac failed (%d)\n", ret);
>   		return ret;
> @@ -631,23 +627,23 @@ 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;
>   }
>
> @@ -657,14 +653,15 @@ 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);
> @@ -672,7 +669,6 @@ 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 6340823f8b53..6f5c34b885fb 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -234,7 +234,8 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
>   		      struct trusted_key_options *options)
>   {
>   	off_t offset = TPM_HEADER_SIZE;
> -	struct tpm_buf buf, sized;
> +	struct tpm_buf *buf __free(kfree) = NULL;
> +	struct tpm_buf *sized __free(kfree) = NULL;
>   	int blob_len = 0;
>   	int hash;
>   	u32 flags;
> @@ -255,97 +256,100 @@ 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) {
> +	buf = 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);
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
> +
> +	sized = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!sized) {
> +		rc = -ENOMEM;
>   		tpm2_end_auth_session(chip);
>   		goto out_put;
>   	}
>
> -	rc = tpm_buf_append_name(chip, &buf, options->keyhandle, NULL);
> +	tpm_buf_init_sized(sized, TPM_BUFSIZE);
> +
> +	rc = tpm_buf_append_name(chip, buf, options->keyhandle, NULL);
>   	if (rc)
>   		goto out;
>
> -	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);
>
>   	/* sensitive */
> -	tpm_buf_append_u16(&sized, options->blobauth_len);
> +	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_reset_sized(sized);
> +	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_OVERFLOW) {
> +	if (buf->flags & TPM_BUF_OVERFLOW) {
>   		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_BOUNDARY_ERROR) {
> +	blob_len = tpm_buf_read_u32(buf, &offset);
> +	if (blob_len > MAX_BLOB_SIZE || buf->flags & TPM_BUF_BOUNDARY_ERROR) {
>   		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 +377,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
>   			 u32 *blob_handle)
>   {
>   	u8 *blob_ref __free(kfree) = NULL;
> -	struct tpm_buf buf;
> +	struct tpm_buf *buf __free(kfree) = NULL;
>   	unsigned int private_len;
>   	unsigned int public_len;
>   	unsigned int blob_len;
> @@ -427,39 +431,38 @@ 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) {
> +	buf = 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_OVERFLOW) {
> -		rc = -E2BIG;
> +	if (buf->flags & TPM_BUF_OVERFLOW) {
>   		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);
>   }
> @@ -482,7 +485,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>   			   u32 blob_handle)
>   {
>   	struct tpm_header *head;
> -	struct tpm_buf buf;
> +	struct tpm_buf *buf __free(kfree) = NULL;
>   	u16 data_len;
>   	int offset;
>   	u8 *data;
> @@ -492,18 +495,21 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>   	if (rc)
>   		return rc;
>
> -	rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
> -	if (rc) {
> +	buf = kzalloc(TPM_BUFSIZE, GFP_KERNEL);
> +	if (!buf) {
>   		tpm2_end_auth_session(chip);
> -		return rc;
> +		return -ENOMEM;
>   	}
>
> -	rc = tpm_buf_append_name(chip, &buf, blob_handle, NULL);
> +	tpm_buf_init(buf, TPM_BUFSIZE);
> +	tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
> +
> +	rc = tpm_buf_append_name(chip, buf, blob_handle, 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 +524,36 @@ 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 +570,6 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
>   		}
>   	}
>
> -out:
> -	tpm_buf_destroy(&buf);
>   	return tpm_ret_to_err(rc);
>   }
>
> --
> 2.47.3
>
>