From: Jarkko Sakkinen <jarkko.sakki...@opinsys.com>

Repeal and replace tpm_buf_init() and tpm_buf_init_sized() with
tpm_buf_alloc(), which returns PAGE_SIZE of memory with the struct tpm_buf
header in the beginning of the returned buffer. This leaves 4088 bytes of
free space for data.

Given that kfree() is now the destructor for struct tpm_buf instances,
tpm_buf_destroy() is obsolete, and can (and should) be wiped off.

The gist of this patch is that now a tpm_buf can be now declared using
__free(kfree) declared in linux/slab.h:

        struct tpm_buf *buf __free(kfree) = NULL;

        /* ... */

        buf = tpm_buf_alloc();

This makes TPM driver and other subsystems using struct tpm_buf more
memory-safe as there is no to worry about freeing up these temporary
scratch buffers.

Signed-off-by: Jarkko Sakkinen <jarkko.sakki...@opinsys.com>

v3:
- Removed the cleanup class and moved on using __free(kfree) instead.
- Removed `buf_size` (James).
- I'm open for the idea of splitting still (Jason) but I'll hold
  at least this revision just to check that my core idea here
  is correct.
v2:
- Implement also memory allocation using the cleanup class.
- Rewrote the commit message.
- Implemented CLASS_TPM_BUF() helper macro.
---
 drivers/char/tpm/tpm-buf.c                |  52 ++---
 drivers/char/tpm/tpm-sysfs.c              |  20 +-
 drivers/char/tpm/tpm1-cmd.c               | 150 ++++++------
 drivers/char/tpm/tpm2-cmd.c               | 272 ++++++++++------------
 drivers/char/tpm/tpm2-sessions.c          | 122 +++++-----
 drivers/char/tpm/tpm2-space.c             |  44 ++--
 drivers/char/tpm/tpm_vtpm_proxy.c         |  30 ++-
 include/linux/tpm.h                       |  15 +-
 security/keys/trusted-keys/trusted_tpm1.c |  35 +--
 security/keys/trusted-keys/trusted_tpm2.c | 157 ++++++-------
 10 files changed, 414 insertions(+), 483 deletions(-)

diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
index dc882fc9fa9e..e874bb57600c 100644
--- a/drivers/char/tpm/tpm-buf.c
+++ b/drivers/char/tpm/tpm-buf.c
@@ -8,23 +8,28 @@
 #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
+ * tpm_buf_alloc() - Allocate a TPM buffer
+ *
+ * Allocates `PAGE_SIZE` of memory and places &tpm_buf to the beginning of the
+ * allocated buffer. For that reason the total capacity can be at most 4088
+ * bytes. If a caller tries to surpass the maximum capacity, `TPM_BUF_OVERFLOW`
+ * will be set and any future operations will be ignored.
  *
- * Return: 0 or -ENOMEM
+ * Return:
+ * * &tpm_buf: success
+ * * NULL:     out of memory
  */
-int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal)
+struct tpm_buf *tpm_buf_alloc(void)
 {
-       buf->data = (u8 *)__get_free_page(GFP_KERNEL);
-       if (!buf->data)
-               return -ENOMEM;
+       struct tpm_buf *buf;
 
-       tpm_buf_reset(buf, tag, ordinal);
-       return 0;
+       buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
+       if (!buf)
+               return NULL;
+
+       return buf;
 }
-EXPORT_SYMBOL_GPL(tpm_buf_init);
+EXPORT_SYMBOL_GPL(tpm_buf_alloc);
 
 /**
  * tpm_buf_reset() - Initialize a TPM command
@@ -48,23 +53,6 @@ void tpm_buf_reset(struct tpm_buf *buf, u16 tag, u32 ordinal)
 }
 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
- */
-int tpm_buf_init_sized(struct tpm_buf *buf)
-{
-       buf->data = (u8 *)__get_free_page(GFP_KERNEL);
-       if (!buf->data)
-               return -ENOMEM;
-
-       tpm_buf_reset_sized(buf);
-       return 0;
-}
-EXPORT_SYMBOL_GPL(tpm_buf_init_sized);
-
 /**
  * tpm_buf_reset_sized() - Initialize a sized buffer
  * @buf:       A &tpm_buf
@@ -78,12 +66,6 @@ void tpm_buf_reset_sized(struct tpm_buf *buf)
 }
 EXPORT_SYMBOL_GPL(tpm_buf_reset_sized);
 
-void tpm_buf_destroy(struct tpm_buf *buf)
-{
-       free_page((unsigned long)buf->data);
-}
-EXPORT_SYMBOL_GPL(tpm_buf_destroy);
-
 /**
  * tpm_buf_length() - Return the number of bytes consumed by the data
  * @buf:       A &tpm_buf
diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
index 94231f052ea7..9aaebd8057d4 100644
--- a/drivers/char/tpm/tpm-sysfs.c
+++ b/drivers/char/tpm/tpm-sysfs.c
@@ -32,28 +32,30 @@ 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_buf *tpm_buf __free(kfree) = NULL;
        struct tpm_readpubek_out *out;
        int i;
        char *str = buf;
        struct tpm_chip *chip = to_tpm_chip(dev);
        char anti_replay[20];
 
+       tpm_buf = tpm_buf_alloc();
+       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_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 +73,6 @@ 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/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c
index cf64c7385105..974894013287 100644
--- a/drivers/char/tpm/tpm1-cmd.c
+++ b/drivers/char/tpm/tpm1-cmd.c
@@ -323,19 +323,19 @@ unsigned long tpm1_calc_ordinal_duration(struct tpm_chip 
*chip, u32 ordinal)
  */
 static int tpm1_startup(struct tpm_chip *chip)
 {
-       struct tpm_buf buf;
+       struct tpm_buf *buf __free(kfree) = NULL;
        int rc;
 
-       dev_info(&chip->dev, "starting up the TPM manually\n");
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
 
-       rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_STARTUP);
-       if (rc < 0)
-               return rc;
+       dev_info(&chip->dev, "starting up the TPM manually\n");
 
-       tpm_buf_append_u16(&buf, TPM_ST_CLEAR);
+       tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_STARTUP);
+       tpm_buf_append_u16(buf, TPM_ST_CLEAR);
 
-       rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to start the TPM");
-       tpm_buf_destroy(&buf);
+       rc = tpm_transmit_cmd(chip, buf, 0, "attempting to start the TPM");
        return rc;
 }
 
@@ -463,18 +463,18 @@ 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;
+       struct tpm_buf *buf __free(kfree) = NULL;
        int rc;
 
-       rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCR_EXTEND);
-       if (rc)
-               return rc;
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
 
-       tpm_buf_append_u32(&buf, pcr_idx);
-       tpm_buf_append(&buf, hash, TPM_DIGEST_SIZE);
+       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);
 
-       rc = tpm_transmit_cmd(chip, &buf, TPM_DIGEST_SIZE, log_msg);
-       tpm_buf_destroy(&buf);
+       rc = tpm_transmit_cmd(chip, buf, TPM_DIGEST_SIZE, log_msg);
        return rc;
 }
 
@@ -482,31 +482,32 @@ int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, 
const u8 *hash,
 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;
+       struct tpm_buf *buf __free(kfree) = NULL;
        int rc;
 
-       rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_GET_CAP);
-       if (rc)
-               return rc;
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
+       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);
@@ -529,83 +530,76 @@ struct tpm1_get_random_out {
  */
 int tpm1_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 {
+       struct tpm_buf *buf __free(kfree) = NULL;
        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;
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
+       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)
                                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);
+               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;
+       struct tpm_buf *buf __free(kfree) = NULL;
        int rc;
 
-       rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCRREAD);
-       if (rc)
-               return rc;
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
 
-       tpm_buf_append_u32(&buf, pcr_idx);
+       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 (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;
 }
 
@@ -619,15 +613,15 @@ 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;
+       struct tpm_buf *buf __free(kfree) = NULL;
        int rc;
 
-       rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_CONTINUE_SELFTEST);
-       if (rc)
-               return rc;
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
 
-       rc = tpm_transmit_cmd(chip, &buf, 0, "continue selftest");
-       tpm_buf_destroy(&buf);
+       tpm_buf_reset(buf, TPM_TAG_RQU_COMMAND, TPM_ORD_CONTINUE_SELFTEST);
+       rc = tpm_transmit_cmd(chip, buf, 0, "continue selftest");
        return rc;
 }
 
@@ -741,23 +735,25 @@ int tpm1_auto_startup(struct tpm_chip *chip)
  */
 int tpm1_pm_suspend(struct tpm_chip *chip, u32 tpm_suspend_pcr)
 {
+       struct tpm_buf *buf __free(kfree) = NULL;
        u8 dummy_hash[TPM_DIGEST_SIZE] = { 0 };
-       struct tpm_buf buf;
        unsigned int try;
        int rc;
 
+       buf = tpm_buf_alloc();
+       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_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 +768,7 @@ 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 +778,6 @@ 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 524d802ede26..86b961f4027b 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -165,14 +165,18 @@ struct tpm2_pcr_read_out {
 int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
                  struct tpm_digest *digest, u16 *digest_size_ptr)
 {
+       struct tpm_buf *buf __free(kfree) = NULL;
        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;
 
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
        if (pcr_idx >= TPM2_PLATFORM_PCR)
                return -EINVAL;
 
@@ -187,23 +191,21 @@ 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_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;
 
-       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)) {
@@ -216,7 +218,6 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx,
 
        memcpy(digest->digest, out->digest, digest_size);
 out:
-       tpm_buf_destroy(&buf);
        return rc;
 }
 
@@ -232,46 +233,43 @@ 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;
+       struct tpm_buf *buf __free(kfree) = NULL;
        int rc;
        int i;
 
+       buf = tpm_buf_alloc();
+       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_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_EXTEND);
 
        if (!disable_pcr_integrity) {
-               tpm_buf_append_name(chip, &buf, pcr_idx, NULL);
-               tpm_buf_append_hmac_session(chip, &buf, 0, NULL, 0);
+               tpm_buf_append_name(chip, buf, pcr_idx, NULL);
+               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, 0, NULL, 0);
+               tpm_buf_append_handle(chip, buf, pcr_idx);
+               tpm_buf_append_auth(chip, buf, 0, 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)
-               tpm_buf_fill_hmac_session(chip, &buf);
-       rc = tpm_transmit_cmd(chip, &buf, 0, "attempting extend a PCR value");
+               tpm_buf_fill_hmac_session(chip, buf);
+       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;
 }
@@ -294,9 +292,9 @@ struct tpm2_get_random_out {
  */
 int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max)
 {
+       struct tpm_buf *buf __free(kfree) = NULL;
        struct tpm2_get_random_out *out;
        struct tpm_header *head;
-       struct tpm_buf buf;
        u32 recd;
        u32 num_bytes = max;
        int err;
@@ -308,43 +306,41 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, 
size_t max)
        if (!num_bytes || max > TPM_MAX_RNG_DATA)
                return -EINVAL;
 
+       buf = tpm_buf_alloc();
+       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;
-       }
-
        do {
-               tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
-               tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT
+               tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM);
+               tpm_buf_append_hmac_session_opt(chip, buf, TPM2_SA_ENCRYPT
                                                | TPM2_SA_CONTINUE_SESSION,
                                                NULL, 0);
-               tpm_buf_append_u16(&buf, num_bytes);
-               tpm_buf_fill_hmac_session(chip, &buf);
-               err = tpm_transmit_cmd(chip, &buf,
+               tpm_buf_append_u16(buf, num_bytes);
+               tpm_buf_fill_hmac_session(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) {
@@ -358,11 +354,9 @@ 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;
 }
@@ -374,20 +368,19 @@ 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;
+       struct tpm_buf *buf __free(kfree) = NULL;
 
-       rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_FLUSH_CONTEXT);
-       if (rc) {
+       buf = tpm_buf_alloc();
+       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_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);
 
@@ -413,20 +406,22 @@ struct tpm2_get_cap_out {
 ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id,  u32 *value,
                        const char *desc)
 {
+       struct tpm_buf *buf __free(kfree) = NULL;
        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);
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
+       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
@@ -438,7 +433,6 @@ 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);
@@ -455,15 +449,15 @@ EXPORT_SYMBOL_GPL(tpm2_get_tpm_pt);
  */
 void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type)
 {
-       struct tpm_buf buf;
-       int rc;
+       struct tpm_buf *buf __free(kfree) = NULL;
 
-       rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_SHUTDOWN);
-       if (rc)
+       buf = tpm_buf_alloc();
+       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_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");
 }
 
 /**
@@ -481,19 +475,19 @@ void tpm2_shutdown(struct tpm_chip *chip, u16 
shutdown_type)
  */
 static int tpm2_do_selftest(struct tpm_chip *chip)
 {
-       struct tpm_buf buf;
+       struct tpm_buf *buf __free(kfree) = NULL;
        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;
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
 
-               tpm_buf_append_u8(&buf, full);
-               rc = tpm_transmit_cmd(chip, &buf, 0,
+       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,
                                      "attempting the self test");
-               tpm_buf_destroy(&buf);
 
                if (rc == TPM2_RC_TESTING)
                        rc = TPM2_RC_SUCCESS;
@@ -518,24 +512,25 @@ static int tpm2_do_selftest(struct tpm_chip *chip)
  */
 int tpm2_probe(struct tpm_chip *chip)
 {
+       struct tpm_buf *buf __free(kfree) = NULL;
        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);
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
+       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);
@@ -574,8 +569,8 @@ struct tpm2_pcr_selection {
 
 ssize_t tpm2_get_pcr_allocation(struct tpm_chip *chip)
 {
+       struct tpm_buf *buf __free(kfree) = NULL;
        struct tpm2_pcr_selection pcr_selection;
-       struct tpm_buf buf;
        void *marker;
        void *end;
        void *pcr_select_offset;
@@ -587,41 +582,39 @@ 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;
+       buf = tpm_buf_alloc();
+       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_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;
+               return rc;
 
        nr_possible_banks = be32_to_cpup(
-               (__be32 *)&buf.data[TPM_HEADER_SIZE + 5]);
+               (__be32 *)&buf->data[TPM_HEADER_SIZE + 5]);
 
        chip->allocated_banks = kcalloc(nr_possible_banks,
                                        sizeof(*chip->allocated_banks),
                                        GFP_KERNEL);
-       if (!chip->allocated_banks) {
-               rc = -ENOMEM;
-               goto out;
-       }
+       if (!chip->allocated_banks)
+               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];
 
+       return rc;
        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);
@@ -633,7 +626,7 @@ 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++;
                }
@@ -645,21 +638,22 @@ 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;
+       struct tpm_buf *buf __free(kfree) = NULL;
        u32 nr_commands;
        __be32 *attrs;
        u32 cc;
        int i;
        int rc;
 
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
        rc = tpm2_get_tpm_pt(chip, TPM_PT_TOTAL_COMMANDS, &nr_commands, NULL);
        if (rc)
                goto out;
@@ -676,30 +670,24 @@ 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_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])) {
+           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;
@@ -711,8 +699,6 @@ int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip)
                }
        }
 
-       tpm_buf_destroy(&buf);
-
 out:
        if (rc > 0)
                rc = -ENODEV;
@@ -733,20 +719,18 @@ 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");
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
 
-       rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_STARTUP);
-       if (rc < 0)
-               return rc;
+       dev_info(&chip->dev, "starting up the TPM manually\n");
 
-       tpm_buf_append_u16(&buf, TPM2_SU_CLEAR);
-       rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to start the TPM");
-       tpm_buf_destroy(&buf);
+       tpm_buf_reset(buf, TPM2_ST_NO_SESSIONS, TPM2_CC_STARTUP);
+       tpm_buf_append_u16(buf, TPM2_SU_CLEAR);
 
-       return rc;
+       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 7b5049b3d476..50c481c7c947 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -182,19 +182,18 @@ static int tpm2_parse_read_public(char *name, struct 
tpm_buf *buf)
 
 static int tpm2_read_public(struct tpm_chip *chip, u32 handle, char *name)
 {
-       struct tpm_buf buf;
+       struct tpm_buf *buf __free(kfree) = NULL;
        int rc;
 
-       rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
-       if (rc)
-               return rc;
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
 
-       tpm_buf_append_u32(&buf, handle);
-       rc = tpm_transmit_cmd(chip, &buf, 0, "read public");
+       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, "read public");
        if (rc == TPM2_RC_SUCCESS)
-               rc = tpm2_parse_read_public(name, &buf);
-
-       tpm_buf_destroy(&buf);
+               rc = tpm2_parse_read_public(name, buf);
 
        return rc;
 }
@@ -968,8 +967,8 @@ 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;
 
@@ -978,6 +977,10 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
                return 0;
        }
 
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
        auth = kzalloc(sizeof(*auth), GFP_KERNEL);
        if (!auth)
                return -ENOMEM;
@@ -988,41 +991,36 @@ 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_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;
@@ -1243,19 +1241,20 @@ 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 *buf __free(kfree) = NULL;
+       struct tpm_buf *template __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 = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
 
-       rc = tpm_buf_init_sized(&template);
-       if (rc) {
-               tpm_buf_destroy(&buf);
-               return rc;
-       }
+       template = tpm_buf_alloc();
+       if (!template)
+               return -ENOMEM;
+
+       tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE_PRIMARY);
+       tpm_buf_reset_sized(template);
 
        /*
         * create the template.  Note: in order for userspace to
@@ -1267,75 +1266,72 @@ 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..818b6f4084c7 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 tpm_buf *tbuf __free(kfree) = NULL;
        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;
+       tbuf = tpm_buf_alloc();
+       if (!tbuf)
+               return -ENOMEM;
+
+       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;
+       struct tpm_buf *tbuf __free(kfree) = NULL;
        unsigned int body_size;
        int rc;
 
-       rc = tpm_buf_init(&tbuf, TPM2_ST_NO_SESSIONS, TPM2_CC_CONTEXT_SAVE);
-       if (rc)
-               return rc;
+       tbuf = tpm_buf_alloc();
+       if (!tbuf)
+               return -ENOMEM;
 
-       tpm_buf_append_u32(&tbuf, handle);
+       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..6d76fe28826a 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;
+       struct tpm_buf *buf __free(kfree) = NULL;
        int rc;
        const struct tpm_header *header;
        struct proxy_dev *proxy_dev = dev_get_drvdata(&chip->dev);
 
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
        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 804fbbe3873d..463174182701 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -375,13 +375,14 @@ 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 handles;
+       u16 flags;
+       u16 length;
+       u16 handles;
+       u8 data[];
 };
 
 enum tpm2_object_attributes {
@@ -412,11 +413,9 @@ struct tpm2_hash {
        unsigned int tpm_id;
 };
 
-int tpm_buf_init(struct tpm_buf *buf, u16 tag, u32 ordinal);
+struct tpm_buf *tpm_buf_alloc(void);
 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);
 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);
diff --git a/security/keys/trusted-keys/trusted_tpm1.c 
b/security/keys/trusted-keys/trusted_tpm1.c
index 89c9798d1800..106496c68625 100644
--- a/security/keys/trusted-keys/trusted_tpm1.c
+++ b/security/keys/trusted-keys/trusted_tpm1.c
@@ -356,21 +356,24 @@ static int TSS_checkhmac2(unsigned char *buffer,
  */
 int trusted_tpm_send(unsigned char *cmd, size_t buflen)
 {
-       struct tpm_buf buf;
+       struct tpm_buf *buf __free(kfree) = NULL;
        int rc;
 
        if (!chip)
                return -ENODEV;
 
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
        rc = tpm_try_get_ops(chip);
        if (rc)
                return rc;
 
-       buf.flags = 0;
-       buf.length = buflen;
-       buf.data = cmd;
+       tpm_buf_append(buf, cmd, buflen);
+
        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)
@@ -672,23 +675,22 @@ 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;
+       struct tpm_buf *tb __free(kfree) = NULL;
        int ret;
 
-       ret = tpm_buf_init(&tb, 0, 0);
-       if (ret)
-               return ret;
+       tb = tpm_buf_alloc();
+       if (!tb)
+               return -ENOMEM;
 
        /* 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;
 }
 
@@ -698,14 +700,14 @@ 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;
+       struct tpm_buf *tb __free(kfree) = NULL;
        int ret;
 
-       ret = tpm_buf_init(&tb, 0, 0);
-       if (ret)
-               return ret;
+       tb = tpm_buf_alloc();
+       if (!tb)
+               return -ENOMEM;
 
-       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);
@@ -713,7 +715,6 @@ 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 024be262702f..54bcd8d0621e 100644
--- a/security/keys/trusted-keys/trusted_tpm2.c
+++ b/security/keys/trusted-keys/trusted_tpm2.c
@@ -241,14 +241,23 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
                      struct trusted_key_payload *payload,
                      struct trusted_key_options *options)
 {
+       struct tpm_buf *buf __free(kfree) = NULL;
+       struct tpm_buf *sized __free(kfree) = NULL;
        off_t offset = TPM_HEADER_SIZE;
-       struct tpm_buf buf, sized;
        int blob_len = 0;
        u32 hash;
        u32 flags;
        int i;
        int rc;
 
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
+       sized = tpm_buf_alloc();
+       if (!sized)
+               return -ENOMEM;
+
        for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) {
                if (options->hash == tpm2_hash_map[i].crypto_id) {
                        hash = tpm2_hash_map[i].tpm_id;
@@ -270,89 +279,76 @@ 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) {
-               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_append_name(chip, &buf, options->keyhandle, NULL);
-       tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_DECRYPT,
+       tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE);
+       tpm_buf_reset_sized(sized);
+       tpm_buf_append_name(chip, buf, options->keyhandle, NULL);
+       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;
        }
 
-       tpm_buf_fill_hmac_session(chip, &buf);
-       rc = tpm_transmit_cmd(chip, &buf, 4, "sealing data");
-       rc = tpm_buf_check_hmac_response(chip, &buf, rc);
+       tpm_buf_fill_hmac_session(chip, buf);
+       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);
 
 out:
-       tpm_buf_destroy(&sized);
-       tpm_buf_destroy(&buf);
-
        if (rc > 0) {
                if (tpm2_rc_value(rc) == TPM2_RC_HASH)
                        rc = -EINVAL;
@@ -387,7 +383,7 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
                         struct trusted_key_options *options,
                         u32 *blob_handle)
 {
-       struct tpm_buf buf;
+       struct tpm_buf *buf __free(kfree) = NULL;
        unsigned int private_len;
        unsigned int public_len;
        unsigned int blob_len;
@@ -395,6 +391,10 @@ static int tpm2_load_cmd(struct tpm_chip *chip,
        int rc;
        u32 attrs;
 
+       buf = tpm_buf_alloc();
+       if (!buf)
+               return -ENOMEM;
+
        rc = tpm2_key_decode(payload, options, &blob);
        if (rc) {
                /* old form */
@@ -438,35 +438,29 @@ 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) {
-               tpm2_end_auth_session(chip);
-               return rc;
-       }
-
-       tpm_buf_append_name(chip, &buf, options->keyhandle, NULL);
-       tpm_buf_append_hmac_session(chip, &buf, 0, options->keyauth,
+       tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD);
+       tpm_buf_append_name(chip, buf, options->keyhandle, NULL);
+       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) {
+       if (buf->flags & TPM_BUF_OVERFLOW) {
                rc = -E2BIG;
                tpm2_end_auth_session(chip);
                goto out;
        }
 
-       tpm_buf_fill_hmac_session(chip, &buf);
-       rc = tpm_transmit_cmd(chip, &buf, 4, "loading blob");
-       rc = tpm_buf_check_hmac_response(chip, &buf, rc);
+       tpm_buf_fill_hmac_session(chip, buf);
+       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]);
+                       (__be32 *)&buf->data[TPM_HEADER_SIZE]);
 
 out:
        if (blob != payload->blob)
                kfree(blob);
-       tpm_buf_destroy(&buf);
 
        if (rc > 0)
                rc = -EPERM;
@@ -491,25 +485,24 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
                           struct trusted_key_options *options,
                           u32 blob_handle)
 {
-       struct tpm_buf buf;
+       struct tpm_buf *buf __free(kfree) = NULL;
        u16 data_len;
        u8 *data;
        int rc;
 
+       buf = tpm_buf_alloc();
+       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_append_name(chip, &buf, blob_handle, NULL);
+       tpm_buf_reset(buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL);
+       tpm_buf_append_name(chip, buf, blob_handle, NULL);
 
        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 {
@@ -524,32 +517,28 @@ 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);
-               tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT,
+               tpm_buf_append_hmac_session_opt(chip, buf, TPM2_SA_ENCRYPT,
                                                NULL, 0);
        }
 
-       tpm_buf_fill_hmac_session(chip, &buf);
-       rc = tpm_transmit_cmd(chip, &buf, 6, "unsealing");
-       rc = tpm_buf_check_hmac_response(chip, &buf, rc);
+       tpm_buf_fill_hmac_session(chip, buf);
+       rc = tpm_transmit_cmd(chip, buf, 6, "unsealing");
+       rc = tpm_buf_check_hmac_response(chip, buf, rc);
        if (rc > 0)
                rc = -EPERM;
 
        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 */
@@ -566,8 +555,6 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
                }
        }
 
-out:
-       tpm_buf_destroy(&buf);
        return rc;
 }
 
-- 
2.39.5


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