Merge tag 'tpmdd-next-6.10-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd

Pull TPM fixes from Jarkko Sakkinen:
 "This contains the fixes for !chip->auth condition, preventing the
  breakage of:
   - tpm_ftpm_tee.c
   - tpm_i2c_nuvoton.c
   - tpm_ibmvtpm.c
   - tpm_tis_i2c_cr50.c
   - tpm_vtpm_proxy.c

  All drivers will continue to work as they did in 6.9, except a single
  warning (dev_warn() not WARN()) is printed to klog only to inform that
  authenticated sessions are not enabled"

* tag 'tpmdd-next-6.10-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/jarkko/linux-tpmdd:
  tpm: Address !chip->auth in tpm_buf_append_hmac_session*()
  tpm: Address !chip->auth in tpm_buf_append_name()
  tpm: Address !chip->auth in tpm2_*_auth_session()

drivers/char/tpm/Makefile

@@ -16,8 +16,8 @@ tpm-y += eventlog/common.o
 tpm-y += eventlog/tpm1.o
 tpm-y += eventlog/tpm2.o
 tpm-y += tpm-buf.o
+tpm-y += tpm2-sessions.o
 
-tpm-$(CONFIG_TCG_TPM2_HMAC) += tpm2-sessions.o
 tpm-$(CONFIG_ACPI) += tpm_ppi.o eventlog/acpi.o
 tpm-$(CONFIG_EFI) += eventlog/efi.o
 tpm-$(CONFIG_OF) += eventlog/of.o

drivers/char/tpm/tpm2-sessions.c

@@ -83,9 +83,6 @@
 #define AES_KEY_BYTES	AES_KEYSIZE_128
 #define AES_KEY_BITS	(AES_KEY_BYTES*8)
 
-static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
-			       u32 *handle, u8 *name);
-
 /*
  * This is the structure that carries all the auth information (like
  * session handle, nonces, session key and auth) from use to use it is
@@ -148,6 +145,7 @@ struct tpm2_auth {
 	u8 name[AUTH_MAX_NAMES][2 + SHA512_DIGEST_SIZE];
 };
 
+#ifdef CONFIG_TCG_TPM2_HMAC
 /*
  * Name Size based on TPM algorithm (assumes no hash bigger than 255)
  */
@@ -163,6 +161,226 @@ static u8 name_size(const u8 *name)
 	return size_map[alg] + 2;
 }
 
+static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
+{
+	struct tpm_header *head = (struct tpm_header *)buf->data;
+	off_t offset = TPM_HEADER_SIZE;
+	u32 tot_len = be32_to_cpu(head->length);
+	u32 val;
+
+	/* we're starting after the header so adjust the length */
+	tot_len -= TPM_HEADER_SIZE;
+
+	/* skip public */
+	val = tpm_buf_read_u16(buf, &offset);
+	if (val > tot_len)
+		return -EINVAL;
+	offset += val;
+	/* name */
+	val = tpm_buf_read_u16(buf, &offset);
+	if (val != name_size(&buf->data[offset]))
+		return -EINVAL;
+	memcpy(name, &buf->data[offset], val);
+	/* forget the rest */
+	return 0;
+}
+
+static int tpm2_read_public(struct tpm_chip *chip, u32 handle, char *name)
+{
+	struct tpm_buf buf;
+	int rc;
+
+	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
+	if (rc)
+		return rc;
+
+	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);
+
+	return rc;
+}
+#endif /* CONFIG_TCG_TPM2_HMAC */
+
+/**
+ * tpm_buf_append_name() - add a handle area to the buffer
+ * @chip: the TPM chip structure
+ * @buf: The buffer to be appended
+ * @handle: The handle to be appended
+ * @name: The name of the handle (may be NULL)
+ *
+ * In order to compute session HMACs, we need to know the names of the
+ * objects pointed to by the handles.  For most objects, this is simply
+ * the actual 4 byte handle or an empty buf (in these cases @name
+ * should be NULL) but for volatile objects, permanent objects and NV
+ * areas, the name is defined as the hash (according to the name
+ * algorithm which should be set to sha256) of the public area to
+ * which the two byte algorithm id has been appended.  For these
+ * objects, the @name pointer should point to this.  If a name is
+ * required but @name is NULL, then TPM2_ReadPublic() will be called
+ * on the handle to obtain the name.
+ *
+ * As with most tpm_buf operations, success is assumed because failure
+ * will be caused by an incorrect programming model and indicated by a
+ * kernel message.
+ */
+void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
+			 u32 handle, u8 *name)
+{
+#ifdef CONFIG_TCG_TPM2_HMAC
+	enum tpm2_mso_type mso = tpm2_handle_mso(handle);
+	struct tpm2_auth *auth;
+	int slot;
+#endif
+
+	if (!tpm2_chip_auth(chip)) {
+		tpm_buf_append_u32(buf, handle);
+		/* count the number of handles in the upper bits of flags */
+		buf->handles++;
+		return;
+	}
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+	slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE) / 4;
+	if (slot >= AUTH_MAX_NAMES) {
+		dev_err(&chip->dev, "TPM: too many handles\n");
+		return;
+	}
+	auth = chip->auth;
+	WARN(auth->session != tpm_buf_length(buf),
+	     "name added in wrong place\n");
+	tpm_buf_append_u32(buf, handle);
+	auth->session += 4;
+
+	if (mso == TPM2_MSO_PERSISTENT ||
+	    mso == TPM2_MSO_VOLATILE ||
+	    mso == TPM2_MSO_NVRAM) {
+		if (!name)
+			tpm2_read_public(chip, handle, auth->name[slot]);
+	} else {
+		if (name)
+			dev_err(&chip->dev, "TPM: Handle does not require name but one is specified\n");
+	}
+
+	auth->name_h[slot] = handle;
+	if (name)
+		memcpy(auth->name[slot], name, name_size(name));
+#endif
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_name);
+
+/**
+ * tpm_buf_append_hmac_session() - Append a TPM session element
+ * @chip: the TPM chip structure
+ * @buf: The buffer to be appended
+ * @attributes: The session attributes
+ * @passphrase: The session authority (NULL if none)
+ * @passphrase_len: The length of the session authority (0 if none)
+ *
+ * This fills in a session structure in the TPM command buffer, except
+ * for the HMAC which cannot be computed until the command buffer is
+ * complete.  The type of session is controlled by the @attributes,
+ * the main ones of which are TPM2_SA_CONTINUE_SESSION which means the
+ * session won't terminate after tpm_buf_check_hmac_response(),
+ * TPM2_SA_DECRYPT which means this buffers first parameter should be
+ * encrypted with a session key and TPM2_SA_ENCRYPT, which means the
+ * response buffer's first parameter needs to be decrypted (confusing,
+ * but the defines are written from the point of view of the TPM).
+ *
+ * Any session appended by this command must be finalized by calling
+ * tpm_buf_fill_hmac_session() otherwise the HMAC will be incorrect
+ * and the TPM will reject the command.
+ *
+ * As with most tpm_buf operations, success is assumed because failure
+ * will be caused by an incorrect programming model and indicated by a
+ * kernel message.
+ */
+void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
+				 u8 attributes, u8 *passphrase,
+				 int passphrase_len)
+{
+#ifdef CONFIG_TCG_TPM2_HMAC
+	u8 nonce[SHA256_DIGEST_SIZE];
+	struct tpm2_auth *auth;
+	u32 len;
+#endif
+
+	if (!tpm2_chip_auth(chip)) {
+		/* offset tells us where the sessions area begins */
+		int offset = buf->handles * 4 + TPM_HEADER_SIZE;
+		u32 len = 9 + passphrase_len;
+
+		if (tpm_buf_length(buf) != offset) {
+			/* not the first session so update the existing length */
+			len += get_unaligned_be32(&buf->data[offset]);
+			put_unaligned_be32(len, &buf->data[offset]);
+		} else {
+			tpm_buf_append_u32(buf, len);
+		}
+		/* auth handle */
+		tpm_buf_append_u32(buf, TPM2_RS_PW);
+		/* nonce */
+		tpm_buf_append_u16(buf, 0);
+		/* attributes */
+		tpm_buf_append_u8(buf, 0);
+		/* passphrase */
+		tpm_buf_append_u16(buf, passphrase_len);
+		tpm_buf_append(buf, passphrase, passphrase_len);
+		return;
+	}
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+	/*
+	 * The Architecture Guide requires us to strip trailing zeros
+	 * before computing the HMAC
+	 */
+	while (passphrase && passphrase_len > 0 && passphrase[passphrase_len - 1] == '\0')
+		passphrase_len--;
+
+	auth = chip->auth;
+	auth->attrs = attributes;
+	auth->passphrase_len = passphrase_len;
+	if (passphrase_len)
+		memcpy(auth->passphrase, passphrase, passphrase_len);
+
+	if (auth->session != tpm_buf_length(buf)) {
+		/* we're not the first session */
+		len = get_unaligned_be32(&buf->data[auth->session]);
+		if (4 + len + auth->session != tpm_buf_length(buf)) {
+			WARN(1, "session length mismatch, cannot append");
+			return;
+		}
+
+		/* add our new session */
+		len += 9 + 2 * SHA256_DIGEST_SIZE;
+		put_unaligned_be32(len, &buf->data[auth->session]);
+	} else {
+		tpm_buf_append_u32(buf, 9 + 2 * SHA256_DIGEST_SIZE);
+	}
+
+	/* random number for our nonce */
+	get_random_bytes(nonce, sizeof(nonce));
+	memcpy(auth->our_nonce, nonce, sizeof(nonce));
+	tpm_buf_append_u32(buf, auth->handle);
+	/* our new nonce */
+	tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
+	tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
+	tpm_buf_append_u8(buf, auth->attrs);
+	/* and put a placeholder for the hmac */
+	tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
+	tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
+#endif
+}
+EXPORT_SYMBOL_GPL(tpm_buf_append_hmac_session);
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+
+static int tpm2_create_primary(struct tpm_chip *chip, u32 hierarchy,
+			       u32 *handle, u8 *name);
+
 /*
  * It turns out the crypto hmac(sha256) is hard for us to consume
  * because it assumes a fixed key and the TPM seems to change the key
@@ -343,82 +561,6 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
 	crypto_free_kpp(kpp);
 }
 
-/**
- * tpm_buf_append_hmac_session() - Append a TPM session element
- * @chip: the TPM chip structure
- * @buf: The buffer to be appended
- * @attributes: The session attributes
- * @passphrase: The session authority (NULL if none)
- * @passphrase_len: The length of the session authority (0 if none)
- *
- * This fills in a session structure in the TPM command buffer, except
- * for the HMAC which cannot be computed until the command buffer is
- * complete.  The type of session is controlled by the @attributes,
- * the main ones of which are TPM2_SA_CONTINUE_SESSION which means the
- * session won't terminate after tpm_buf_check_hmac_response(),
- * TPM2_SA_DECRYPT which means this buffers first parameter should be
- * encrypted with a session key and TPM2_SA_ENCRYPT, which means the
- * response buffer's first parameter needs to be decrypted (confusing,
- * but the defines are written from the point of view of the TPM).
- *
- * Any session appended by this command must be finalized by calling
- * tpm_buf_fill_hmac_session() otherwise the HMAC will be incorrect
- * and the TPM will reject the command.
- *
- * As with most tpm_buf operations, success is assumed because failure
- * will be caused by an incorrect programming model and indicated by a
- * kernel message.
- */
-void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
-				 u8 attributes, u8 *passphrase,
-				 int passphrase_len)
-{
-	u8 nonce[SHA256_DIGEST_SIZE];
-	u32 len;
-	struct tpm2_auth *auth = chip->auth;
-
-	/*
-	 * The Architecture Guide requires us to strip trailing zeros
-	 * before computing the HMAC
-	 */
-	while (passphrase && passphrase_len > 0
-	       && passphrase[passphrase_len - 1] == '\0')
-		passphrase_len--;
-
-	auth->attrs = attributes;
-	auth->passphrase_len = passphrase_len;
-	if (passphrase_len)
-		memcpy(auth->passphrase, passphrase, passphrase_len);
-
-	if (auth->session != tpm_buf_length(buf)) {
-		/* we're not the first session */
-		len = get_unaligned_be32(&buf->data[auth->session]);
-		if (4 + len + auth->session != tpm_buf_length(buf)) {
-			WARN(1, "session length mismatch, cannot append");
-			return;
-		}
-
-		/* add our new session */
-		len += 9 + 2 * SHA256_DIGEST_SIZE;
-		put_unaligned_be32(len, &buf->data[auth->session]);
-	} else {
-		tpm_buf_append_u32(buf, 9 + 2 * SHA256_DIGEST_SIZE);
-	}
-
-	/* random number for our nonce */
-	get_random_bytes(nonce, sizeof(nonce));
-	memcpy(auth->our_nonce, nonce, sizeof(nonce));
-	tpm_buf_append_u32(buf, auth->handle);
-	/* our new nonce */
-	tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
-	tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
-	tpm_buf_append_u8(buf, auth->attrs);
-	/* and put a placeholder for the hmac */
-	tpm_buf_append_u16(buf, SHA256_DIGEST_SIZE);
-	tpm_buf_append(buf, nonce, SHA256_DIGEST_SIZE);
-}
-EXPORT_SYMBOL(tpm_buf_append_hmac_session);
-
 /**
  * tpm_buf_fill_hmac_session() - finalize the session HMAC
  * @chip: the TPM chip structure
@@ -449,6 +591,9 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 	u8 cphash[SHA256_DIGEST_SIZE];
 	struct sha256_state sctx;
 
+	if (!auth)
+		return;
+
 	/* save the command code in BE format */
 	auth->ordinal = head->ordinal;
 
@@ -567,104 +712,6 @@ void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf)
 }
 EXPORT_SYMBOL(tpm_buf_fill_hmac_session);
 
-static int tpm2_parse_read_public(char *name, struct tpm_buf *buf)
-{
-	struct tpm_header *head = (struct tpm_header *)buf->data;
-	off_t offset = TPM_HEADER_SIZE;
-	u32 tot_len = be32_to_cpu(head->length);
-	u32 val;
-
-	/* we're starting after the header so adjust the length */
-	tot_len -= TPM_HEADER_SIZE;
-
-	/* skip public */
-	val = tpm_buf_read_u16(buf, &offset);
-	if (val > tot_len)
-		return -EINVAL;
-	offset += val;
-	/* name */
-	val = tpm_buf_read_u16(buf, &offset);
-	if (val != name_size(&buf->data[offset]))
-		return -EINVAL;
-	memcpy(name, &buf->data[offset], val);
-	/* forget the rest */
-	return 0;
-}
-
-static int tpm2_read_public(struct tpm_chip *chip, u32 handle, char *name)
-{
-	struct tpm_buf buf;
-	int rc;
-
-	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_READ_PUBLIC);
-	if (rc)
-		return rc;
-
-	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);
-
-	return rc;
-}
-
-/**
- * tpm_buf_append_name() - add a handle area to the buffer
- * @chip: the TPM chip structure
- * @buf: The buffer to be appended
- * @handle: The handle to be appended
- * @name: The name of the handle (may be NULL)
- *
- * In order to compute session HMACs, we need to know the names of the
- * objects pointed to by the handles.  For most objects, this is simply
- * the actual 4 byte handle or an empty buf (in these cases @name
- * should be NULL) but for volatile objects, permanent objects and NV
- * areas, the name is defined as the hash (according to the name
- * algorithm which should be set to sha256) of the public area to
- * which the two byte algorithm id has been appended.  For these
- * objects, the @name pointer should point to this.  If a name is
- * required but @name is NULL, then TPM2_ReadPublic() will be called
- * on the handle to obtain the name.
- *
- * As with most tpm_buf operations, success is assumed because failure
- * will be caused by an incorrect programming model and indicated by a
- * kernel message.
- */
-void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
-			 u32 handle, u8 *name)
-{
-	enum tpm2_mso_type mso = tpm2_handle_mso(handle);
-	struct tpm2_auth *auth = chip->auth;
-	int slot;
-
-	slot = (tpm_buf_length(buf) - TPM_HEADER_SIZE)/4;
-	if (slot >= AUTH_MAX_NAMES) {
-		dev_err(&chip->dev, "TPM: too many handles\n");
-		return;
-	}
-	WARN(auth->session != tpm_buf_length(buf),
-	     "name added in wrong place\n");
-	tpm_buf_append_u32(buf, handle);
-	auth->session += 4;
-
-	if (mso == TPM2_MSO_PERSISTENT ||
-	    mso == TPM2_MSO_VOLATILE ||
-	    mso == TPM2_MSO_NVRAM) {
-		if (!name)
-			tpm2_read_public(chip, handle, auth->name[slot]);
-	} else {
-		if (name)
-			dev_err(&chip->dev, "TPM: Handle does not require name but one is specified\n");
-	}
-
-	auth->name_h[slot] = handle;
-	if (name)
-		memcpy(auth->name[slot], name, name_size(name));
-}
-EXPORT_SYMBOL(tpm_buf_append_name);
-
 /**
  * tpm_buf_check_hmac_response() - check the TPM return HMAC for correctness
  * @chip: the TPM chip structure
@@ -705,6 +752,9 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
 	u32 cc = be32_to_cpu(auth->ordinal);
 	int parm_len, len, i, handles;
 
+	if (!auth)
+		return rc;
+
 	if (auth->session >= TPM_HEADER_SIZE) {
 		WARN(1, "tpm session not filled correctly\n");
 		goto out;
@@ -824,8 +874,13 @@ EXPORT_SYMBOL(tpm_buf_check_hmac_response);
  */
 void tpm2_end_auth_session(struct tpm_chip *chip)
 {
-	tpm2_flush_context(chip, chip->auth->handle);
-	memzero_explicit(chip->auth, sizeof(*chip->auth));
+	struct tpm2_auth *auth = chip->auth;
+
+	if (!auth)
+		return;
+
+	tpm2_flush_context(chip, auth->handle);
+	memzero_explicit(auth, sizeof(*auth));
 }
 EXPORT_SYMBOL(tpm2_end_auth_session);
 
@@ -907,6 +962,11 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 	int rc;
 	u32 null_key;
 
+	if (!auth) {
+		dev_warn_once(&chip->dev, "auth session is not active\n");
+		return 0;
+	}
+
 	rc = tpm2_load_null(chip, &null_key);
 	if (rc)
 		goto out;
@@ -1301,3 +1361,4 @@ int tpm2_sessions_init(struct tpm_chip *chip)
 
 	return rc;
 }
+#endif /* CONFIG_TCG_TPM2_HMAC */

include/linux/tpm.h

@@ -490,9 +490,16 @@ static inline void tpm_buf_append_empty_auth(struct tpm_buf *buf, u32 handle)
 {
 }
 #endif
+
+static inline struct tpm2_auth *tpm2_chip_auth(struct tpm_chip *chip)
+{
 #ifdef CONFIG_TCG_TPM2_HMAC
+	return chip->auth;
+#else
+	return NULL;
+#endif
+}
 
-int tpm2_start_auth_session(struct tpm_chip *chip);
 void tpm_buf_append_name(struct tpm_chip *chip, struct tpm_buf *buf,
 			 u32 handle, u8 *name);
 void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
@@ -504,9 +511,27 @@ static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
 						   u8 *passphrase,
 						   int passphraselen)
 {
-	tpm_buf_append_hmac_session(chip, buf, attributes, passphrase,
-				    passphraselen);
+	struct tpm_header *head;
+	int offset;
+
+	if (tpm2_chip_auth(chip)) {
+		tpm_buf_append_hmac_session(chip, buf, attributes, passphrase, passphraselen);
+	} else  {
+		offset = buf->handles * 4 + TPM_HEADER_SIZE;
+		head = (struct tpm_header *)buf->data;
+
+		/*
+		 * If the only sessions are optional, the command tag must change to
+		 * TPM2_ST_NO_SESSIONS.
+		 */
+		if (tpm_buf_length(buf) == offset)
+			head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
+	}
 }
+
+#ifdef CONFIG_TCG_TPM2_HMAC
+
+int tpm2_start_auth_session(struct tpm_chip *chip);
 void tpm_buf_fill_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf);
 int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
 				int rc);
@@ -521,56 +546,6 @@ static inline int tpm2_start_auth_session(struct tpm_chip *chip)
 static inline void tpm2_end_auth_session(struct tpm_chip *chip)
 {
 }
-static inline void tpm_buf_append_name(struct tpm_chip *chip,
-				       struct tpm_buf *buf,
-				       u32 handle, u8 *name)
-{
-	tpm_buf_append_u32(buf, handle);
-	/* count the number of handles in the upper bits of flags */
-	buf->handles++;
-}
-static inline void tpm_buf_append_hmac_session(struct tpm_chip *chip,
-					       struct tpm_buf *buf,
-					       u8 attributes, u8 *passphrase,
-					       int passphraselen)
-{
-	/* offset tells us where the sessions area begins */
-	int offset = buf->handles * 4 + TPM_HEADER_SIZE;
-	u32 len = 9 + passphraselen;
-
-	if (tpm_buf_length(buf) != offset) {
-		/* not the first session so update the existing length */
-		len += get_unaligned_be32(&buf->data[offset]);
-		put_unaligned_be32(len, &buf->data[offset]);
-	} else {
-		tpm_buf_append_u32(buf, len);
-	}
-	/* auth handle */
-	tpm_buf_append_u32(buf, TPM2_RS_PW);
-	/* nonce */
-	tpm_buf_append_u16(buf, 0);
-	/* attributes */
-	tpm_buf_append_u8(buf, 0);
-	/* passphrase */
-	tpm_buf_append_u16(buf, passphraselen);
-	tpm_buf_append(buf, passphrase, passphraselen);
-}
-static inline void tpm_buf_append_hmac_session_opt(struct tpm_chip *chip,
-						   struct tpm_buf *buf,
-						   u8 attributes,
-						   u8 *passphrase,
-						   int passphraselen)
-{
-	int offset = buf->handles * 4 + TPM_HEADER_SIZE;
-	struct tpm_header *head = (struct tpm_header *) buf->data;
-
-	/*
-	 * if the only sessions are optional, the command tag
-	 * must change to TPM2_ST_NO_SESSIONS
-	 */
-	if (tpm_buf_length(buf) == offset)
-		head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS);
-}
 static inline void tpm_buf_fill_hmac_session(struct tpm_chip *chip,
 					     struct tpm_buf *buf)
 {