On Sat, Dec 06, 2025 at 01:31:10PM +0200, Jarkko Sakkinen wrote:
> From: Jarkko Sakkinen <[email protected]>
> 
> 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 <[email protected]>
> Reviewed-by: Stefan Berger <[email protected]>
> ---
>  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

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