[PATCH v7 0/5] Lazy flush for the auth session

[PATCH v7 0/5] Lazy flush for the auth session

[Jarkko Sakkinen]

Cc: David Howells <dhowells@redhat.com> 
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Mimi Zohar <zohar@linux.ibm.com>
Cc: Roberto Sassu <roberto.sassu@huawei.com>
Cc: Stefan Berger <stefanb@linux.ibm.com>
Cc: linux-integrity@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219229

v6:
https://lore.kernel.org/linux-integrity/D501D1CY5SJ4.SUKXHV680B30@kernel.org/T/#t
v5:
https://lore.kernel.org/linux-integrity/D4WQ58T5O21X.CGFKGFKV630K@kernel.org/T/#m527d0466a02abaa448720999ff055de0540e7bb7
v4:
https://lore.kernel.org/linux-integrity/20240918203559.192605-1-jarkko@kernel.org/
v3:
https://lore.kernel.org/linux-integrity/20240917154444.702370-1-jarkko@kernel.org/
v2:
https://lore.kernel.org/linux-integrity/20240916110714.1396407-1-jarkko@kernel.org/
v1:
https://lore.kernel.org/linux-integrity/20240915180448.2030115-1-jarkko@kernel.org/

Jarkko Sakkinen (5):
  tpm: Return on tpm2_create_null_primary() failure
  tpm: Implement tpm2_load_null() rollback
  tpm: flush the null key only when /dev/tpm0 is accessed
  tpm: Allocate chip->auth in tpm2_start_auth_session()
  tpm: flush the auth session only when /dev/tpm0 is open

 drivers/char/tpm/tpm-chip.c       |  14 ++++
 drivers/char/tpm/tpm-dev-common.c |   8 +++
 drivers/char/tpm/tpm-interface.c  |  10 ++-
 drivers/char/tpm/tpm2-cmd.c       |   3 +
 drivers/char/tpm/tpm2-sessions.c  | 115 +++++++++++++++++++-----------
 include/linux/tpm.h               |   2 +
 6 files changed, 108 insertions(+), 44 deletions(-)

-- 
2.47.0

[PATCH v7 1/5] tpm: Return on tpm2_create_null_primary() failure

[Jarkko Sakkinen]

tpm2_sessions_init() does not ignore the result of
tpm2_create_null_primary(). Address this by returning -ENODEV to the
caller. Given that upper layers cannot help healing the situation
further, deal with the TPM error here by

Cc: stable@vger.kernel.org # v6.10+
Fixes: d2add27cf2b8 ("tpm: Add NULL primary creation")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v7:
- Add the error message back but fix it up a bit:
  1. Remove 'TPM:' given dev_err().
  2. s/NULL/null/ as this has nothing to do with the macro in libc.
  3. Fix the reasoning: null key creation failed
v6:
- Address:
  https://lore.kernel.org/linux-integrity/69c893e7-6b87-4daa-80db-44d1120e80fe@linux.ibm.com/
  as TPM RC is taken care of at the call site. Add also the missing
  documentation for the return values.
v5:
- Do not print klog messages on error, as tpm2_save_context() already
  takes care of this.
v4:
- Fixed up stable version.
v3:
- Handle TPM and POSIX error separately and return -ENODEV always back
  to the caller.
v2:
- Refined the commit message.
---
 drivers/char/tpm/tpm2-sessions.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index d3521aadd43e..1e12e0b2492e 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -1347,14 +1347,21 @@ static int tpm2_create_null_primary(struct tpm_chip *chip)
  *
  * Derive and context save the null primary and allocate memory in the
  * struct tpm_chip for the authorizations.
+ *
+ * Return:
+ * * 0		- OK
+ * * -errno	- A system error
+ * * TPM_RC	- A TPM error
  */
 int tpm2_sessions_init(struct tpm_chip *chip)
 {
 	int rc;
 
 	rc = tpm2_create_null_primary(chip);
-	if (rc)
-		dev_err(&chip->dev, "TPM: security failed (NULL seed derivation): %d\n", rc);
+	if (rc) {
+		dev_err(&chip->dev, "null primary key creation failed with %d\n", rc);
+		return rc;
+	}
 
 	chip->auth = kmalloc(sizeof(*chip->auth), GFP_KERNEL);
 	if (!chip->auth)
-- 
2.47.0

[PATCH v7 2/5] tpm: Implement tpm2_load_null() rollback

[Jarkko Sakkinen]

tpm2_load_null() has weak and broken error handling:

- The return value of tpm2_create_primary() is ignored.
- Leaks TPM return codes from tpm2_load_context() to the caller.
- If the key name comparison succeeds returns previous error
  instead of zero to the caller.

Implement a proper error rollback.

Cc: stable@vger.kernel.org # v6.10+
Fixes: eb24c9788cd9 ("tpm: disable the TPM if NULL name changes")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
--
v6:
- Address Stefan's remark:
  https://lore.kernel.org/linux-integrity/def4ec2d-584b-405f-9d5e-99267013c3c0@linux.ibm.com/
v5:
- Fix the TPM error code leak from tpm2_load_context().
v4:
- No changes.
v3:
- Update log messages. Previously the log message incorrectly stated
  on load failure that integrity check had been failed, even tho the
  check is done *after* the load operation.
v2:
- Refined the commit message.
- Reverted tpm2_create_primary() changes. They are not required if
  tmp_null_key is used as the parameter.
---
 drivers/char/tpm/tpm2-sessions.c | 43 +++++++++++++++++---------------
 1 file changed, 23 insertions(+), 20 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 1e12e0b2492e..bdac11964b55 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -915,33 +915,36 @@ static int tpm2_parse_start_auth_session(struct tpm2_auth *auth,
 
 static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
 {
-	int rc;
 	unsigned int offset = 0; /* dummy offset for null seed context */
 	u8 name[SHA256_DIGEST_SIZE + 2];
+	u32 tmp_null_key;
+	int rc;
 
 	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
-			       null_key);
-	if (rc != -EINVAL)
-		return rc;
+			       &tmp_null_key);
+	if (rc != -EINVAL) {
+		if (!rc)
+			*null_key = tmp_null_key;
+		goto err;
+	}
 
-	/* an integrity failure may mean the TPM has been reset */
-	dev_err(&chip->dev, "NULL key integrity failure!\n");
-	/* check the null name against what we know */
-	tpm2_create_primary(chip, TPM2_RH_NULL, NULL, name);
-	if (memcmp(name, chip->null_key_name, sizeof(name)) == 0)
-		/* name unchanged, assume transient integrity failure */
-		return rc;
-	/*
-	 * Fatal TPM failure: the NULL seed has actually changed, so
-	 * the TPM must have been illegally reset.  All in-kernel TPM
-	 * operations will fail because the NULL primary can't be
-	 * loaded to salt the sessions, but disable the TPM anyway so
-	 * userspace programmes can't be compromised by it.
-	 */
-	dev_err(&chip->dev, "NULL name has changed, disabling TPM due to interference\n");
+	rc = tpm2_create_primary(chip, TPM2_RH_NULL, &tmp_null_key, name);
+	if (rc)
+		goto err;
+
+	/* Return the null key if the name has not been changed: */
+	if (memcmp(name, chip->null_key_name, sizeof(name)) == 0) {
+		*null_key = tmp_null_key;
+		return 0;
+	}
+
+	/* Deduce from the name change TPM interference: */
+	dev_err(&chip->dev, "the null key integrity check failedh\n");
+	tpm2_flush_context(chip, tmp_null_key);
 	chip->flags |= TPM_CHIP_FLAG_DISABLE;
 
-	return rc;
+err:
+	return rc ? -ENODEV : 0;
 }
 
 /**
-- 
2.47.0

[PATCH v7 3/5] tpm: flush the null key only when /dev/tpm0 is accessed

[Jarkko Sakkinen]

Instead of flushing and reloading the null key for every single auth
session, flush it only when:

1. User space needs to access /dev/tpm{rm}0.
2. When going to sleep.
3. When unregistering the chip.

This removes the need to load and swap the null key between TPM and
regular memory per transaction, when the user space is not using the
chip.

Cc: stable@vger.kernel.org # v6.10+
Fixes: d2add27cf2b8 ("tpm: Add NULL primary creation")
Tested-by: Pengyu Ma <mapengyu@gmail.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v5:
- No changes.
v4:
- Changed to bug fix as not having the patch there is a major hit
  to bootup times.
v3:
- Unchanged.
v2:
- Refined the commit message.
- Added tested-by from Pengyu Ma <mapengyu@gmail.com>.
- Removed spurious pr_info() statement.
---
 drivers/char/tpm/tpm-chip.c       | 13 +++++++++++++
 drivers/char/tpm/tpm-dev-common.c |  7 +++++++
 drivers/char/tpm/tpm-interface.c  |  9 +++++++--
 drivers/char/tpm/tpm2-cmd.c       |  3 +++
 drivers/char/tpm/tpm2-sessions.c  | 17 ++++++++++++++---
 include/linux/tpm.h               |  2 ++
 6 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 854546000c92..0ea00e32f575 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -674,6 +674,19 @@ EXPORT_SYMBOL_GPL(tpm_chip_register);
  */
 void tpm_chip_unregister(struct tpm_chip *chip)
 {
+#ifdef CONFIG_TCG_TPM2_HMAC
+	int rc;
+
+	rc = tpm_try_get_ops(chip);
+	if (!rc) {
+		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+			tpm2_flush_context(chip, chip->null_key);
+			chip->null_key = 0;
+		}
+		tpm_put_ops(chip);
+	}
+#endif
+
 	tpm_del_legacy_sysfs(chip);
 	if (tpm_is_hwrng_enabled(chip))
 		hwrng_unregister(&chip->hwrng);
diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 30b4c288c1bb..4eaa8e05c291 100644
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -27,6 +27,13 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
 	struct tpm_header *header = (void *)buf;
 	ssize_t ret, len;
 
+#ifdef CONFIG_TCG_TPM2_HMAC
+	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+		tpm2_flush_context(chip, chip->null_key);
+		chip->null_key = 0;
+	}
+#endif
+
 	ret = tpm2_prepare_space(chip, space, buf, bufsiz);
 	/* If the command is not implemented by the TPM, synthesize a
 	 * response with a TPM2_RC_COMMAND_CODE return for user-space.
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index 5da134f12c9a..bfa47d48b0f2 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -379,10 +379,15 @@ int tpm_pm_suspend(struct device *dev)
 
 	rc = tpm_try_get_ops(chip);
 	if (!rc) {
-		if (chip->flags & TPM_CHIP_FLAG_TPM2)
+		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+#ifdef CONFIG_TCG_TPM2_HMAC
+			tpm2_flush_context(chip, chip->null_key);
+			chip->null_key = 0;
+#endif
 			tpm2_shutdown(chip, TPM2_SU_STATE);
-		else
+		} else {
 			rc = tpm1_pm_suspend(chip, tpm_suspend_pcr);
+		}
 
 		tpm_put_ops(chip);
 	}
diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
index 1e856259219e..aba024cbe7c5 100644
--- a/drivers/char/tpm/tpm2-cmd.c
+++ b/drivers/char/tpm/tpm2-cmd.c
@@ -364,6 +364,9 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
 	struct tpm_buf buf;
 	int rc;
 
+	if (!handle)
+		return;
+
 	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_FLUSH_CONTEXT);
 	if (rc) {
 		dev_warn(&chip->dev, "0x%08x was not flushed, out of memory\n",
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index bdac11964b55..78c650ce4c9f 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -920,11 +920,19 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
 	u32 tmp_null_key;
 	int rc;
 
+	/* fast path */
+	if (chip->null_key) {
+		*null_key = chip->null_key;
+		return 0;
+	}
+
 	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
 			       &tmp_null_key);
 	if (rc != -EINVAL) {
-		if (!rc)
+		if (!rc) {
+			chip->null_key = tmp_null_key;
 			*null_key = tmp_null_key;
+		}
 		goto err;
 	}
 
@@ -934,6 +942,7 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
 
 	/* Return the null key if the name has not been changed: */
 	if (memcmp(name, chip->null_key_name, sizeof(name)) == 0) {
+		chip->null_key = tmp_null_key;
 		*null_key = tmp_null_key;
 		return 0;
 	}
@@ -1006,7 +1015,6 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
 
 	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
-	tpm2_flush_context(chip, null_key);
 
 	if (rc == TPM2_RC_SUCCESS)
 		rc = tpm2_parse_start_auth_session(auth, &buf);
@@ -1338,7 +1346,10 @@ static int tpm2_create_null_primary(struct tpm_chip *chip)
 
 		rc = tpm2_save_context(chip, null_key, chip->null_key_context,
 				       sizeof(chip->null_key_context), &offset);
-		tpm2_flush_context(chip, null_key);
+		if (rc)
+			tpm2_flush_context(chip, null_key);
+		else
+			chip->null_key = null_key;
 	}
 
 	return rc;
diff --git a/include/linux/tpm.h b/include/linux/tpm.h
index e93ee8d936a9..4eb39db80e05 100644
--- a/include/linux/tpm.h
+++ b/include/linux/tpm.h
@@ -205,6 +205,8 @@ struct tpm_chip {
 #ifdef CONFIG_TCG_TPM2_HMAC
 	/* details for communication security via sessions */
 
+	/* loaded null key */
+	u32 null_key;
 	/* saved context for NULL seed */
 	u8 null_key_context[TPM2_MAX_CONTEXT_SIZE];
 	 /* name of NULL seed */
-- 
2.47.0

[PATCH v7 4/5] tpm: Allocate chip->auth in tpm2_start_auth_session()

[Jarkko Sakkinen]

Move allocation of chip->auth to tpm2_start_auth_session() so that the
field can be used as flag to tell whether auth session is active or not.

Cc: stable@vger.kernel.org # v6.10+
Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v5:
- No changes.
v4:
- Change to bug.
v3:
- No changes.
v2:
- A new patch.
---
 drivers/char/tpm/tpm2-sessions.c | 43 +++++++++++++++++++-------------
 1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 78c650ce4c9f..6e52785de9fd 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -484,7 +484,8 @@ static void tpm2_KDFe(u8 z[EC_PT_SZ], const char *str, u8 *pt_u, u8 *pt_v,
 	sha256_final(&sctx, out);
 }
 
-static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
+static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip,
+				struct tpm2_auth *auth)
 {
 	struct crypto_kpp *kpp;
 	struct kpp_request *req;
@@ -543,7 +544,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
 	sg_set_buf(&s[0], chip->null_ec_key_x, EC_PT_SZ);
 	sg_set_buf(&s[1], chip->null_ec_key_y, EC_PT_SZ);
 	kpp_request_set_input(req, s, EC_PT_SZ*2);
-	sg_init_one(d, chip->auth->salt, EC_PT_SZ);
+	sg_init_one(d, auth->salt, EC_PT_SZ);
 	kpp_request_set_output(req, d, EC_PT_SZ);
 	crypto_kpp_compute_shared_secret(req);
 	kpp_request_free(req);
@@ -554,8 +555,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
 	 * This works because KDFe fully consumes the secret before it
 	 * writes the salt
 	 */
-	tpm2_KDFe(chip->auth->salt, "SECRET", x, chip->null_ec_key_x,
-		  chip->auth->salt);
+	tpm2_KDFe(auth->salt, "SECRET", x, chip->null_ec_key_x, auth->salt);
 
  out:
 	crypto_free_kpp(kpp);
@@ -854,6 +854,8 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
 			/* manually close the session if it wasn't consumed */
 			tpm2_flush_context(chip, auth->handle);
 		memzero_explicit(auth, sizeof(*auth));
+		kfree(auth);
+		chip->auth = NULL;
 	} else {
 		/* reset for next use  */
 		auth->session = TPM_HEADER_SIZE;
@@ -882,6 +884,8 @@ void tpm2_end_auth_session(struct tpm_chip *chip)
 
 	tpm2_flush_context(chip, auth->handle);
 	memzero_explicit(auth, sizeof(*auth));
+	kfree(auth);
+	chip->auth = NULL;
 }
 EXPORT_SYMBOL(tpm2_end_auth_session);
 
@@ -970,25 +974,29 @@ 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;
-	struct tpm2_auth *auth = chip->auth;
-	int rc;
 	u32 null_key;
+	int rc;
 
-	if (!auth) {
-		dev_warn_once(&chip->dev, "auth session is not active\n");
+	if (chip->auth) {
+		dev_warn_once(&chip->dev, "auth session is active\n");
 		return 0;
 	}
 
+	auth = kzalloc(sizeof(*auth), GFP_KERNEL);
+	if (!auth)
+		return -ENOMEM;
+
 	rc = tpm2_load_null(chip, &null_key);
 	if (rc)
-		goto out;
+		goto err;
 
 	auth->session = TPM_HEADER_SIZE;
 
 	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
 	if (rc)
-		goto out;
+		goto err;
 
 	/* salt key handle */
 	tpm_buf_append_u32(&buf, null_key);
@@ -1000,7 +1008,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 	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);
+	tpm_buf_append_salt(&buf, chip, auth);
 	/* session type (HMAC, audit or policy) */
 	tpm_buf_append_u8(&buf, TPM2_SE_HMAC);
 
@@ -1021,10 +1029,13 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
 
 	tpm_buf_destroy(&buf);
 
-	if (rc)
-		goto out;
+	if (rc == TPM2_RC_SUCCESS) {
+		chip->auth = auth;
+		return 0;
+	}
 
- out:
+err:
+	kfree(auth);
 	return rc;
 }
 EXPORT_SYMBOL(tpm2_start_auth_session);
@@ -1377,10 +1388,6 @@ int tpm2_sessions_init(struct tpm_chip *chip)
 		return rc;
 	}
 
-	chip->auth = kmalloc(sizeof(*chip->auth), GFP_KERNEL);
-	if (!chip->auth)
-		return -ENOMEM;
-
 	return rc;
 }
 #endif /* CONFIG_TCG_TPM2_HMAC */
-- 
2.47.0

[PATCH v7 5/5] tpm: flush the auth session only when /dev/tpm0 is open

[Jarkko Sakkinen]

Instead of flushing and reloading the auth session for every single
transaction, keep the session open unless /dev/tpm0 is used. In practice
this means applying TPM2_SA_CONTINUE_SESSION to the session attributes.
Flush the session always when /dev/tpm0 is written.

Reported-by: Pengyu Ma <mapengyu@gmail.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219229
Cc: stable@vger.kernel.org # v6.10+
Fixes: 7ca110f2679b ("tpm: Address !chip->auth in tpm_buf_append_hmac_session*()")
Tested-by: Pengyu Ma <mapengyu@gmail.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v5:
- No changes.
v4:
- Changed as bug.
v3:
- Refined the commit message.
- Removed the conditional for applying TPM2_SA_CONTINUE_SESSION only when
  /dev/tpm0 is open. It is not required as the auth session is flushed,
  not saved.
v2:
- A new patch.
---
 drivers/char/tpm/tpm-chip.c       | 1 +
 drivers/char/tpm/tpm-dev-common.c | 1 +
 drivers/char/tpm/tpm-interface.c  | 1 +
 drivers/char/tpm/tpm2-sessions.c  | 3 +++
 4 files changed, 6 insertions(+)

diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
index 0ea00e32f575..7a6bb30d1f32 100644
--- a/drivers/char/tpm/tpm-chip.c
+++ b/drivers/char/tpm/tpm-chip.c
@@ -680,6 +680,7 @@ void tpm_chip_unregister(struct tpm_chip *chip)
 	rc = tpm_try_get_ops(chip);
 	if (!rc) {
 		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+			tpm2_end_auth_session(chip);
 			tpm2_flush_context(chip, chip->null_key);
 			chip->null_key = 0;
 		}
diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
index 4eaa8e05c291..a3ed7a99a394 100644
--- a/drivers/char/tpm/tpm-dev-common.c
+++ b/drivers/char/tpm/tpm-dev-common.c
@@ -29,6 +29,7 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
 
 #ifdef CONFIG_TCG_TPM2_HMAC
 	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
+		tpm2_end_auth_session(chip);
 		tpm2_flush_context(chip, chip->null_key);
 		chip->null_key = 0;
 	}
diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
index bfa47d48b0f2..2363018fa8fb 100644
--- a/drivers/char/tpm/tpm-interface.c
+++ b/drivers/char/tpm/tpm-interface.c
@@ -381,6 +381,7 @@ int tpm_pm_suspend(struct device *dev)
 	if (!rc) {
 		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
 #ifdef CONFIG_TCG_TPM2_HMAC
+			tpm2_end_auth_session(chip);
 			tpm2_flush_context(chip, chip->null_key);
 			chip->null_key = 0;
 #endif
diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
index 6e52785de9fd..a7079c7ec6d1 100644
--- a/drivers/char/tpm/tpm2-sessions.c
+++ b/drivers/char/tpm/tpm2-sessions.c
@@ -333,6 +333,9 @@ void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
 	}
 
 #ifdef CONFIG_TCG_TPM2_HMAC
+	/* The first write to /dev/tpm{rm0} will flush the session. */
+	attributes |= TPM2_SA_CONTINUE_SESSION;
+
 	/*
 	 * The Architecture Guide requires us to strip trailing zeros
 	 * before computing the HMAC
-- 
2.47.0

Re: [PATCH v7 2/5] tpm: Implement tpm2_load_null() rollback

[Stefan Berger]

On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
> tpm2_load_null() has weak and broken error handling:
> 
> - The return value of tpm2_create_primary() is ignored.
> - Leaks TPM return codes from tpm2_load_context() to the caller.
> - If the key name comparison succeeds returns previous error
>    instead of zero to the caller.
> 
> Implement a proper error rollback.
> 
> Cc: stable@vger.kernel.org # v6.10+
> Fixes: eb24c9788cd9 ("tpm: disable the TPM if NULL name changes")
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> --
> v6:
> - Address Stefan's remark:
>    https://lore.kernel.org/linux-integrity/def4ec2d-584b-405f-9d5e-99267013c3c0@linux.ibm.com/
> v5:
> - Fix the TPM error code leak from tpm2_load_context().
> v4:
> - No changes.
> v3:
> - Update log messages. Previously the log message incorrectly stated
>    on load failure that integrity check had been failed, even tho the
>    check is done *after* the load operation.
> v2:
> - Refined the commit message.
> - Reverted tpm2_create_primary() changes. They are not required if
>    tmp_null_key is used as the parameter.
> ---
>   drivers/char/tpm/tpm2-sessions.c | 43 +++++++++++++++++---------------
>   1 file changed, 23 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 1e12e0b2492e..bdac11964b55 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -915,33 +915,36 @@ static int tpm2_parse_start_auth_session(struct tpm2_auth *auth,
>   
>   static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
>   {
> -	int rc;
>   	unsigned int offset = 0; /* dummy offset for null seed context */
>   	u8 name[SHA256_DIGEST_SIZE + 2];
> +	u32 tmp_null_key;
> +	int rc;
>   
>   	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
> -			       null_key);
> -	if (rc != -EINVAL)
> -		return rc;
> +			       &tmp_null_key);
> +	if (rc != -EINVAL) {
> +		if (!rc)
> +			*null_key = tmp_null_key;
> +		goto err;
> +	}
>   
> -	/* an integrity failure may mean the TPM has been reset */
> -	dev_err(&chip->dev, "NULL key integrity failure!\n");
> -	/* check the null name against what we know */
> -	tpm2_create_primary(chip, TPM2_RH_NULL, NULL, name);
> -	if (memcmp(name, chip->null_key_name, sizeof(name)) == 0)
> -		/* name unchanged, assume transient integrity failure */
> -		return rc;
> -	/*
> -	 * Fatal TPM failure: the NULL seed has actually changed, so
> -	 * the TPM must have been illegally reset.  All in-kernel TPM
> -	 * operations will fail because the NULL primary can't be
> -	 * loaded to salt the sessions, but disable the TPM anyway so
> -	 * userspace programmes can't be compromised by it.
> -	 */
> -	dev_err(&chip->dev, "NULL name has changed, disabling TPM due to interference\n");
> +	rc = tpm2_create_primary(chip, TPM2_RH_NULL, &tmp_null_key, name);
> +	if (rc)
> +		goto err;
> +
> +	/* Return the null key if the name has not been changed: */
> +	if (memcmp(name, chip->null_key_name, sizeof(name)) == 0) {
> +		*null_key = tmp_null_key;
> +		return 0;
> +	}
> +
> +	/* Deduce from the name change TPM interference: */
> +	dev_err(&chip->dev, "the null key integrity check failedh\n");

stray 'h': s/failedh/failed

> +	tpm2_flush_context(chip, tmp_null_key);
>   	chip->flags |= TPM_CHIP_FLAG_DISABLE;
>   
> -	return rc;
> +err:
> +	return rc ? -ENODEV : 0;
>   }
>   
>   /**

Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>

Re: [PATCH v7 1/5] tpm: Return on tpm2_create_null_primary() failure

[Stefan Berger]

On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
> tpm2_sessions_init() does not ignore the result of
> tpm2_create_null_primary(). Address this by returning -ENODEV to the
> caller. Given that upper layers cannot help healing the situation

It looks like returning -ENODEV applied to a previous version of the patch.

> further, deal with the TPM error here by

This sounds like an incomplete sentence...

> 
> Cc: stable@vger.kernel.org # v6.10+
> Fixes: d2add27cf2b8 ("tpm: Add NULL primary creation")
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> v7:
> - Add the error message back but fix it up a bit:
>    1. Remove 'TPM:' given dev_err().
>    2. s/NULL/null/ as this has nothing to do with the macro in libc.
>    3. Fix the reasoning: null key creation failed
> v6:
> - Address:
>    https://lore.kernel.org/linux-integrity/69c893e7-6b87-4daa-80db-44d1120e80fe@linux.ibm.com/
>    as TPM RC is taken care of at the call site. Add also the missing
>    documentation for the return values.
> v5:
> - Do not print klog messages on error, as tpm2_save_context() already
>    takes care of this.
> v4:
> - Fixed up stable version.
> v3:
> - Handle TPM and POSIX error separately and return -ENODEV always back
>    to the caller.
> v2:
> - Refined the commit message.
> ---
>   drivers/char/tpm/tpm2-sessions.c | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index d3521aadd43e..1e12e0b2492e 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -1347,14 +1347,21 @@ static int tpm2_create_null_primary(struct tpm_chip *chip)
>    *
>    * Derive and context save the null primary and allocate memory in the
>    * struct tpm_chip for the authorizations.
> + *
> + * Return:
> + * * 0		- OK
> + * * -errno	- A system error
> + * * TPM_RC	- A TPM error
>    */
>   int tpm2_sessions_init(struct tpm_chip *chip)
>   {
>   	int rc;
>   
>   	rc = tpm2_create_null_primary(chip);
> -	if (rc)
> -		dev_err(&chip->dev, "TPM: security failed (NULL seed derivation): %d\n", rc);
> +	if (rc) {
> +		dev_err(&chip->dev, "null primary key creation failed with %d\n", rc);
> +		return rc;
> +	}
>   
>   	chip->auth = kmalloc(sizeof(*chip->auth), GFP_KERNEL);
>   	if (!chip->auth)

Re: [PATCH v7 3/5] tpm: flush the null key only when /dev/tpm0 is accessed

[Stefan Berger]

On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
> Instead of flushing and reloading the null key for every single auth
> session, flush it only when:
> 
> 1. User space needs to access /dev/tpm{rm}0.
> 2. When going to sleep.
> 3. When unregistering the chip.
> 
> This removes the need to load and swap the null key between TPM and
> regular memory per transaction, when the user space is not using the
> chip.
> 
> Cc: stable@vger.kernel.org # v6.10+
> Fixes: d2add27cf2b8 ("tpm: Add NULL primary creation")
> Tested-by: Pengyu Ma <mapengyu@gmail.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> v5:
> - No changes.
> v4:
> - Changed to bug fix as not having the patch there is a major hit
>    to bootup times.
> v3:
> - Unchanged.
> v2:
> - Refined the commit message.
> - Added tested-by from Pengyu Ma <mapengyu@gmail.com>.
> - Removed spurious pr_info() statement.
> ---
>   drivers/char/tpm/tpm-chip.c       | 13 +++++++++++++
>   drivers/char/tpm/tpm-dev-common.c |  7 +++++++
>   drivers/char/tpm/tpm-interface.c  |  9 +++++++--
>   drivers/char/tpm/tpm2-cmd.c       |  3 +++
>   drivers/char/tpm/tpm2-sessions.c  | 17 ++++++++++++++---
>   include/linux/tpm.h               |  2 ++
>   6 files changed, 46 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 854546000c92..0ea00e32f575 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -674,6 +674,19 @@ EXPORT_SYMBOL_GPL(tpm_chip_register);
>    */
>   void tpm_chip_unregister(struct tpm_chip *chip)
>   {
> +#ifdef CONFIG_TCG_TPM2_HMAC
> +	int rc;
> +
> +	rc = tpm_try_get_ops(chip);
> +	if (!rc) {
> +		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> +			tpm2_flush_context(chip, chip->null_key);

If chip->null_key is already 0, the above function will not do anything 
good, but you could avoid this whole block then by checking for 0 before 
tpm_try_get_ops().

> +			chip->null_key = 0;
> +		}
> +		tpm_put_ops(chip);
> +	}
> +#endif
> +
>   	tpm_del_legacy_sysfs(chip);
>   	if (tpm_is_hwrng_enabled(chip))
>   		hwrng_unregister(&chip->hwrng);
> diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> index 30b4c288c1bb..4eaa8e05c291 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -27,6 +27,13 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
>   	struct tpm_header *header = (void *)buf;
>   	ssize_t ret, len;
>   
> +#ifdef CONFIG_TCG_TPM2_HMAC
> +	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> +		tpm2_flush_context(chip, chip->null_key);
> +		chip->null_key = 0;
> +	}
> +#endif
> +
>   	ret = tpm2_prepare_space(chip, space, buf, bufsiz);
>   	/* If the command is not implemented by the TPM, synthesize a
>   	 * response with a TPM2_RC_COMMAND_CODE return for user-space.
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index 5da134f12c9a..bfa47d48b0f2 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -379,10 +379,15 @@ int tpm_pm_suspend(struct device *dev)
>   
>   	rc = tpm_try_get_ops(chip);
>   	if (!rc) {
> -		if (chip->flags & TPM_CHIP_FLAG_TPM2)
> +		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> +#ifdef CONFIG_TCG_TPM2_HMAC
> +			tpm2_flush_context(chip, chip->null_key);
> +			chip->null_key = 0;
> +#endif

Worth using an inline on this repeating pattern? Up to you.

static inline void tpm2_flush_null_key(struct tpm_chip *chip)
{
#ifdef CONFIG_TCG_TPM2_HMAC
     if (chip->flags & TPM_CHIP_FLAG_TPM2 && chip->null_key) {
         tpm2_flush_context(chip, chip->null_key);
         chip->null_key = 0;
     }
#endif
}

>   			tpm2_shutdown(chip, TPM2_SU_STATE);
> -		else
> +		} else {
>   			rc = tpm1_pm_suspend(chip, tpm_suspend_pcr);
> +		}
>   
>   		tpm_put_ops(chip);
>   	}
> diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> index 1e856259219e..aba024cbe7c5 100644
> --- a/drivers/char/tpm/tpm2-cmd.c
> +++ b/drivers/char/tpm/tpm2-cmd.c
> @@ -364,6 +364,9 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
>   	struct tpm_buf buf;
>   	int rc;
>   
> +	if (!handle)
> +		return;
> +

wouldn't be necessary with inline.

>   	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_FLUSH_CONTEXT);
>   	if (rc) {
>   		dev_warn(&chip->dev, "0x%08x was not flushed, out of memory\n",
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index bdac11964b55..78c650ce4c9f 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -920,11 +920,19 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
>   	u32 tmp_null_key;
>   	int rc;
>   
> +	/* fast path */
> +	if (chip->null_key) {
> +		*null_key = chip->null_key;
> +		return 0;
> +	}
> +
>   	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
>   			       &tmp_null_key);
>   	if (rc != -EINVAL) {
> -		if (!rc)
> +		if (!rc) {
> +			chip->null_key = tmp_null_key;
>   			*null_key = tmp_null_key;
> +		}
>   		goto err;
>   	}
>   
> @@ -934,6 +942,7 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
>   
>   	/* Return the null key if the name has not been changed: */
>   	if (memcmp(name, chip->null_key_name, sizeof(name)) == 0) {
> +		chip->null_key = tmp_null_key;
>   		*null_key = tmp_null_key;
>   		return 0;
>   	}
> @@ -1006,7 +1015,6 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>   	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
>   
>   	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> -	tpm2_flush_context(chip, null_key);
>   
>   	if (rc == TPM2_RC_SUCCESS)
>   		rc = tpm2_parse_start_auth_session(auth, &buf);
> @@ -1338,7 +1346,10 @@ static int tpm2_create_null_primary(struct tpm_chip *chip)
>   
>   		rc = tpm2_save_context(chip, null_key, chip->null_key_context,
>   				       sizeof(chip->null_key_context), &offset);
> -		tpm2_flush_context(chip, null_key);
> +		if (rc)
> +			tpm2_flush_context(chip, null_key);
> +		else
> +			chip->null_key = null_key;
>   	}
>   
>   	return rc;
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index e93ee8d936a9..4eb39db80e05 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -205,6 +205,8 @@ struct tpm_chip {
>   #ifdef CONFIG_TCG_TPM2_HMAC
>   	/* details for communication security via sessions */
>   
> +	/* loaded null key */

nit: handle of loaded null key

> +	u32 null_key;
>   	/* saved context for NULL seed */
>   	u8 null_key_context[TPM2_MAX_CONTEXT_SIZE];
>   	 /* name of NULL seed */

Re: [PATCH v7 4/5] tpm: Allocate chip->auth in tpm2_start_auth_session()

[Stefan Berger]

On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
> Move allocation of chip->auth to tpm2_start_auth_session() so that the
> field can be used as flag to tell whether auth session is active or not.
> 
> Cc: stable@vger.kernel.org # v6.10+
> Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> v5:
> - No changes.
> v4:
> - Change to bug.
> v3:
> - No changes.
> v2:
> - A new patch.
> ---
>   drivers/char/tpm/tpm2-sessions.c | 43 +++++++++++++++++++-------------
>   1 file changed, 25 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 78c650ce4c9f..6e52785de9fd 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -484,7 +484,8 @@ static void tpm2_KDFe(u8 z[EC_PT_SZ], const char *str, u8 *pt_u, u8 *pt_v,
>   	sha256_final(&sctx, out);
>   }
>   
> -static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
> +static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip,
> +				struct tpm2_auth *auth)
>   {
>   	struct crypto_kpp *kpp;
>   	struct kpp_request *req;
> @@ -543,7 +544,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
>   	sg_set_buf(&s[0], chip->null_ec_key_x, EC_PT_SZ);
>   	sg_set_buf(&s[1], chip->null_ec_key_y, EC_PT_SZ);
>   	kpp_request_set_input(req, s, EC_PT_SZ*2);
> -	sg_init_one(d, chip->auth->salt, EC_PT_SZ);
> +	sg_init_one(d, auth->salt, EC_PT_SZ);
>   	kpp_request_set_output(req, d, EC_PT_SZ);
>   	crypto_kpp_compute_shared_secret(req);
>   	kpp_request_free(req);
> @@ -554,8 +555,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
>   	 * This works because KDFe fully consumes the secret before it
>   	 * writes the salt
>   	 */
> -	tpm2_KDFe(chip->auth->salt, "SECRET", x, chip->null_ec_key_x,
> -		  chip->auth->salt);
> +	tpm2_KDFe(auth->salt, "SECRET", x, chip->null_ec_key_x, auth->salt);
>   
>    out:
>   	crypto_free_kpp(kpp);
> @@ -854,6 +854,8 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
>   			/* manually close the session if it wasn't consumed */
>   			tpm2_flush_context(chip, auth->handle);
>   		memzero_explicit(auth, sizeof(*auth));
> +		kfree(auth);
> +		chip->auth = NULL;
>   	} else {
>   		/* reset for next use  */
>   		auth->session = TPM_HEADER_SIZE;
> @@ -882,6 +884,8 @@ void tpm2_end_auth_session(struct tpm_chip *chip)
>   
>   	tpm2_flush_context(chip, auth->handle);
>   	memzero_explicit(auth, sizeof(*auth));
> +	kfree(auth);
> +	chip->auth = NULL;
>   }
>   EXPORT_SYMBOL(tpm2_end_auth_session);
>   
> @@ -970,25 +974,29 @@ 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;
> -	struct tpm2_auth *auth = chip->auth;
> -	int rc;
>   	u32 null_key;
> +	int rc;
>   
> -	if (!auth) {
> -		dev_warn_once(&chip->dev, "auth session is not active\n");
> +	if (chip->auth) {
> +		dev_warn_once(&chip->dev, "auth session is active\n");
>   		return 0;
>   	}
>   
> +	auth = kzalloc(sizeof(*auth), GFP_KERNEL);
> +	if (!auth)
> +		return -ENOMEM;
> +
>   	rc = tpm2_load_null(chip, &null_key);
>   	if (rc)
> -		goto out;
> +		goto err;
>   
>   	auth->session = TPM_HEADER_SIZE;
>   
>   	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
>   	if (rc)
> -		goto out;
> +		goto err;
>   
>   	/* salt key handle */
>   	tpm_buf_append_u32(&buf, null_key);
> @@ -1000,7 +1008,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>   	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);
> +	tpm_buf_append_salt(&buf, chip, auth);
>   	/* session type (HMAC, audit or policy) */
>   	tpm_buf_append_u8(&buf, TPM2_SE_HMAC);
>   
> @@ -1021,10 +1029,13 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>   
>   	tpm_buf_destroy(&buf);
>   
> -	if (rc)
> -		goto out;
> +	if (rc == TPM2_RC_SUCCESS) {
> +		chip->auth = auth;
> +		return 0;
> +	}
>   
> - out:
> +err:

like in many other cases before kfree(auth):
memzero_explicit(auth, sizeof(*auth));

With this:

Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>

> +	kfree(auth);
>   	return rc;
>   }
>   EXPORT_SYMBOL(tpm2_start_auth_session);
> @@ -1377,10 +1388,6 @@ int tpm2_sessions_init(struct tpm_chip *chip)
>   		return rc;
>   	}
>   
> -	chip->auth = kmalloc(sizeof(*chip->auth), GFP_KERNEL);
> -	if (!chip->auth)
> -		return -ENOMEM;
> -
>   	return rc;
>   }
>   #endif /* CONFIG_TCG_TPM2_HMAC */

Re: [PATCH v7 5/5] tpm: flush the auth session only when /dev/tpm0 is open

[Stefan Berger]

On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
> Instead of flushing and reloading the auth session for every single
> transaction, keep the session open unless /dev/tpm0 is used. In practice
> this means applying TPM2_SA_CONTINUE_SESSION to the session attributes.
> Flush the session always when /dev/tpm0 is written.
> 
> Reported-by: Pengyu Ma <mapengyu@gmail.com>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=219229
> Cc: stable@vger.kernel.org # v6.10+
> Fixes: 7ca110f2679b ("tpm: Address !chip->auth in tpm_buf_append_hmac_session*()")
> Tested-by: Pengyu Ma <mapengyu@gmail.com>
> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> ---
> v5:
> - No changes.
> v4:
> - Changed as bug.
> v3:
> - Refined the commit message.
> - Removed the conditional for applying TPM2_SA_CONTINUE_SESSION only when
>    /dev/tpm0 is open. It is not required as the auth session is flushed,
>    not saved.
> v2:
> - A new patch.
> ---
>   drivers/char/tpm/tpm-chip.c       | 1 +
>   drivers/char/tpm/tpm-dev-common.c | 1 +
>   drivers/char/tpm/tpm-interface.c  | 1 +
>   drivers/char/tpm/tpm2-sessions.c  | 3 +++
>   4 files changed, 6 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 0ea00e32f575..7a6bb30d1f32 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -680,6 +680,7 @@ void tpm_chip_unregister(struct tpm_chip *chip)
>   	rc = tpm_try_get_ops(chip);
>   	if (!rc) {
>   		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> +			tpm2_end_auth_session(chip);

That could also go into the inline. Looks good otherwise.

>   			tpm2_flush_context(chip, chip->null_key);
>   			chip->null_key = 0;
>   		}
> diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> index 4eaa8e05c291..a3ed7a99a394 100644
> --- a/drivers/char/tpm/tpm-dev-common.c
> +++ b/drivers/char/tpm/tpm-dev-common.c
> @@ -29,6 +29,7 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
>   
>   #ifdef CONFIG_TCG_TPM2_HMAC
>   	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> +		tpm2_end_auth_session(chip);
>   		tpm2_flush_context(chip, chip->null_key);
>   		chip->null_key = 0;
>   	}
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index bfa47d48b0f2..2363018fa8fb 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -381,6 +381,7 @@ int tpm_pm_suspend(struct device *dev)
>   	if (!rc) {
>   		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
>   #ifdef CONFIG_TCG_TPM2_HMAC
> +			tpm2_end_auth_session(chip);
>   			tpm2_flush_context(chip, chip->null_key);
>   			chip->null_key = 0;
>   #endif
> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> index 6e52785de9fd..a7079c7ec6d1 100644
> --- a/drivers/char/tpm/tpm2-sessions.c
> +++ b/drivers/char/tpm/tpm2-sessions.c
> @@ -333,6 +333,9 @@ void tpm_buf_append_hmac_session(struct tpm_chip *chip, struct tpm_buf *buf,
>   	}
>   
>   #ifdef CONFIG_TCG_TPM2_HMAC
> +	/* The first write to /dev/tpm{rm0} will flush the session. */
> +	attributes |= TPM2_SA_CONTINUE_SESSION;
> +
>   	/*
>   	 * The Architecture Guide requires us to strip trailing zeros
>   	 * before computing the HMAC

Re: [PATCH v7 1/5] tpm: Return on tpm2_create_null_primary() failure

[Jarkko Sakkinen]

On Wed Oct 23, 2024 at 8:46 PM EEST, Stefan Berger wrote:
>
>
> On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
> > tpm2_sessions_init() does not ignore the result of
> > tpm2_create_null_primary(). Address this by returning -ENODEV to the
> > caller. Given that upper layers cannot help healing the situation
>
> It looks like returning -ENODEV applied to a previous version of the patch.
>
> > further, deal with the TPM error here by
>
> This sounds like an incomplete sentence...

It looks like totally corrupted, thanks for the remark.

"tpm2_sessions_init() ignores the return value of tpm2_create_null_primary().
Fail early and return back to the caller if it fails. Fine-tune the error
message while at it."
	
Is this sufficient?

BR, Jarkko

Re: [PATCH v7 3/5] tpm: flush the null key only when /dev/tpm0 is accessed

[Jarkko Sakkinen]

On Wed Oct 23, 2024 at 9:18 PM EEST, Stefan Berger wrote:
>
>
> On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
> > Instead of flushing and reloading the null key for every single auth
> > session, flush it only when:
> > 
> > 1. User space needs to access /dev/tpm{rm}0.
> > 2. When going to sleep.
> > 3. When unregistering the chip.
> > 
> > This removes the need to load and swap the null key between TPM and
> > regular memory per transaction, when the user space is not using the
> > chip.
> > 
> > Cc: stable@vger.kernel.org # v6.10+
> > Fixes: d2add27cf2b8 ("tpm: Add NULL primary creation")
> > Tested-by: Pengyu Ma <mapengyu@gmail.com>
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > v5:
> > - No changes.
> > v4:
> > - Changed to bug fix as not having the patch there is a major hit
> >    to bootup times.
> > v3:
> > - Unchanged.
> > v2:
> > - Refined the commit message.
> > - Added tested-by from Pengyu Ma <mapengyu@gmail.com>.
> > - Removed spurious pr_info() statement.
> > ---
> >   drivers/char/tpm/tpm-chip.c       | 13 +++++++++++++
> >   drivers/char/tpm/tpm-dev-common.c |  7 +++++++
> >   drivers/char/tpm/tpm-interface.c  |  9 +++++++--
> >   drivers/char/tpm/tpm2-cmd.c       |  3 +++
> >   drivers/char/tpm/tpm2-sessions.c  | 17 ++++++++++++++---
> >   include/linux/tpm.h               |  2 ++
> >   6 files changed, 46 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> > index 854546000c92..0ea00e32f575 100644
> > --- a/drivers/char/tpm/tpm-chip.c
> > +++ b/drivers/char/tpm/tpm-chip.c
> > @@ -674,6 +674,19 @@ EXPORT_SYMBOL_GPL(tpm_chip_register);
> >    */
> >   void tpm_chip_unregister(struct tpm_chip *chip)
> >   {
> > +#ifdef CONFIG_TCG_TPM2_HMAC
> > +	int rc;
> > +
> > +	rc = tpm_try_get_ops(chip);
> > +	if (!rc) {
> > +		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> > +			tpm2_flush_context(chip, chip->null_key);
>
> If chip->null_key is already 0, the above function will not do anything 
> good, but you could avoid this whole block then by checking for 0 before 
> tpm_try_get_ops().
>
> > +			chip->null_key = 0;
> > +		}
> > +		tpm_put_ops(chip);
> > +	}
> > +#endif
> > +
> >   	tpm_del_legacy_sysfs(chip);
> >   	if (tpm_is_hwrng_enabled(chip))
> >   		hwrng_unregister(&chip->hwrng);
> > diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c
> > index 30b4c288c1bb..4eaa8e05c291 100644
> > --- a/drivers/char/tpm/tpm-dev-common.c
> > +++ b/drivers/char/tpm/tpm-dev-common.c
> > @@ -27,6 +27,13 @@ static ssize_t tpm_dev_transmit(struct tpm_chip *chip, struct tpm_space *space,
> >   	struct tpm_header *header = (void *)buf;
> >   	ssize_t ret, len;
> >   
> > +#ifdef CONFIG_TCG_TPM2_HMAC
> > +	if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> > +		tpm2_flush_context(chip, chip->null_key);
> > +		chip->null_key = 0;
> > +	}
> > +#endif
> > +
> >   	ret = tpm2_prepare_space(chip, space, buf, bufsiz);
> >   	/* If the command is not implemented by the TPM, synthesize a
> >   	 * response with a TPM2_RC_COMMAND_CODE return for user-space.
> > diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> > index 5da134f12c9a..bfa47d48b0f2 100644
> > --- a/drivers/char/tpm/tpm-interface.c
> > +++ b/drivers/char/tpm/tpm-interface.c
> > @@ -379,10 +379,15 @@ int tpm_pm_suspend(struct device *dev)
> >   
> >   	rc = tpm_try_get_ops(chip);
> >   	if (!rc) {
> > -		if (chip->flags & TPM_CHIP_FLAG_TPM2)
> > +		if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> > +#ifdef CONFIG_TCG_TPM2_HMAC
> > +			tpm2_flush_context(chip, chip->null_key);
> > +			chip->null_key = 0;
> > +#endif
>
> Worth using an inline on this repeating pattern? Up to you.
>
> static inline void tpm2_flush_null_key(struct tpm_chip *chip)
> {
> #ifdef CONFIG_TCG_TPM2_HMAC
>      if (chip->flags & TPM_CHIP_FLAG_TPM2 && chip->null_key) {
>          tpm2_flush_context(chip, chip->null_key);
>          chip->null_key = 0;
>      }
> #endif
> }
>
> >   			tpm2_shutdown(chip, TPM2_SU_STATE);
> > -		else
> > +		} else {
> >   			rc = tpm1_pm_suspend(chip, tpm_suspend_pcr);
> > +		}
> >   
> >   		tpm_put_ops(chip);
> >   	}
> > diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c
> > index 1e856259219e..aba024cbe7c5 100644
> > --- a/drivers/char/tpm/tpm2-cmd.c
> > +++ b/drivers/char/tpm/tpm2-cmd.c
> > @@ -364,6 +364,9 @@ void tpm2_flush_context(struct tpm_chip *chip, u32 handle)
> >   	struct tpm_buf buf;
> >   	int rc;
> >   
> > +	if (!handle)
> > +		return;
> > +
>
> wouldn't be necessary with inline.

True!

>
> >   	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_FLUSH_CONTEXT);
> >   	if (rc) {
> >   		dev_warn(&chip->dev, "0x%08x was not flushed, out of memory\n",
> > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> > index bdac11964b55..78c650ce4c9f 100644
> > --- a/drivers/char/tpm/tpm2-sessions.c
> > +++ b/drivers/char/tpm/tpm2-sessions.c
> > @@ -920,11 +920,19 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> >   	u32 tmp_null_key;
> >   	int rc;
> >   
> > +	/* fast path */
> > +	if (chip->null_key) {
> > +		*null_key = chip->null_key;
> > +		return 0;
> > +	}
> > +
> >   	rc = tpm2_load_context(chip, chip->null_key_context, &offset,
> >   			       &tmp_null_key);
> >   	if (rc != -EINVAL) {
> > -		if (!rc)
> > +		if (!rc) {
> > +			chip->null_key = tmp_null_key;
> >   			*null_key = tmp_null_key;
> > +		}
> >   		goto err;
> >   	}
> >   
> > @@ -934,6 +942,7 @@ static int tpm2_load_null(struct tpm_chip *chip, u32 *null_key)
> >   
> >   	/* Return the null key if the name has not been changed: */
> >   	if (memcmp(name, chip->null_key_name, sizeof(name)) == 0) {
> > +		chip->null_key = tmp_null_key;
> >   		*null_key = tmp_null_key;
> >   		return 0;
> >   	}
> > @@ -1006,7 +1015,6 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> >   	tpm_buf_append_u16(&buf, TPM_ALG_SHA256);
> >   
> >   	rc = tpm_transmit_cmd(chip, &buf, 0, "start auth session");
> > -	tpm2_flush_context(chip, null_key);
> >   
> >   	if (rc == TPM2_RC_SUCCESS)
> >   		rc = tpm2_parse_start_auth_session(auth, &buf);
> > @@ -1338,7 +1346,10 @@ static int tpm2_create_null_primary(struct tpm_chip *chip)
> >   
> >   		rc = tpm2_save_context(chip, null_key, chip->null_key_context,
> >   				       sizeof(chip->null_key_context), &offset);
> > -		tpm2_flush_context(chip, null_key);
> > +		if (rc)
> > +			tpm2_flush_context(chip, null_key);
> > +		else
> > +			chip->null_key = null_key;
> >   	}
> >   
> >   	return rc;
> > diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> > index e93ee8d936a9..4eb39db80e05 100644
> > --- a/include/linux/tpm.h
> > +++ b/include/linux/tpm.h
> > @@ -205,6 +205,8 @@ struct tpm_chip {
> >   #ifdef CONFIG_TCG_TPM2_HMAC
> >   	/* details for communication security via sessions */
> >   
> > +	/* loaded null key */
>
> nit: handle of loaded null key
>
> > +	u32 null_key;
> >   	/* saved context for NULL seed */
> >   	u8 null_key_context[TPM2_MAX_CONTEXT_SIZE];
> >   	 /* name of NULL seed */

I agree with all of your remarks. I'll send one more round because there
is enough changes. Thank you.

BR, Jarkko

Re: [PATCH v7 4/5] tpm: Allocate chip->auth in tpm2_start_auth_session()

[Jarkko Sakkinen]

On Wed Oct 23, 2024 at 10:15 PM EEST, Stefan Berger wrote:
>
>
> On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
> > Move allocation of chip->auth to tpm2_start_auth_session() so that the
> > field can be used as flag to tell whether auth session is active or not.
> > 
> > Cc: stable@vger.kernel.org # v6.10+
> > Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> > Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> > ---
> > v5:
> > - No changes.
> > v4:
> > - Change to bug.
> > v3:
> > - No changes.
> > v2:
> > - A new patch.
> > ---
> >   drivers/char/tpm/tpm2-sessions.c | 43 +++++++++++++++++++-------------
> >   1 file changed, 25 insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> > index 78c650ce4c9f..6e52785de9fd 100644
> > --- a/drivers/char/tpm/tpm2-sessions.c
> > +++ b/drivers/char/tpm/tpm2-sessions.c
> > @@ -484,7 +484,8 @@ static void tpm2_KDFe(u8 z[EC_PT_SZ], const char *str, u8 *pt_u, u8 *pt_v,
> >   	sha256_final(&sctx, out);
> >   }
> >   
> > -static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
> > +static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip,
> > +				struct tpm2_auth *auth)
> >   {
> >   	struct crypto_kpp *kpp;
> >   	struct kpp_request *req;
> > @@ -543,7 +544,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
> >   	sg_set_buf(&s[0], chip->null_ec_key_x, EC_PT_SZ);
> >   	sg_set_buf(&s[1], chip->null_ec_key_y, EC_PT_SZ);
> >   	kpp_request_set_input(req, s, EC_PT_SZ*2);
> > -	sg_init_one(d, chip->auth->salt, EC_PT_SZ);
> > +	sg_init_one(d, auth->salt, EC_PT_SZ);
> >   	kpp_request_set_output(req, d, EC_PT_SZ);
> >   	crypto_kpp_compute_shared_secret(req);
> >   	kpp_request_free(req);
> > @@ -554,8 +555,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
> >   	 * This works because KDFe fully consumes the secret before it
> >   	 * writes the salt
> >   	 */
> > -	tpm2_KDFe(chip->auth->salt, "SECRET", x, chip->null_ec_key_x,
> > -		  chip->auth->salt);
> > +	tpm2_KDFe(auth->salt, "SECRET", x, chip->null_ec_key_x, auth->salt);
> >   
> >    out:
> >   	crypto_free_kpp(kpp);
> > @@ -854,6 +854,8 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
> >   			/* manually close the session if it wasn't consumed */
> >   			tpm2_flush_context(chip, auth->handle);
> >   		memzero_explicit(auth, sizeof(*auth));
> > +		kfree(auth);
> > +		chip->auth = NULL;
> >   	} else {
> >   		/* reset for next use  */
> >   		auth->session = TPM_HEADER_SIZE;
> > @@ -882,6 +884,8 @@ void tpm2_end_auth_session(struct tpm_chip *chip)
> >   
> >   	tpm2_flush_context(chip, auth->handle);
> >   	memzero_explicit(auth, sizeof(*auth));
> > +	kfree(auth);
> > +	chip->auth = NULL;
> >   }
> >   EXPORT_SYMBOL(tpm2_end_auth_session);
> >   
> > @@ -970,25 +974,29 @@ 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;
> > -	struct tpm2_auth *auth = chip->auth;
> > -	int rc;
> >   	u32 null_key;
> > +	int rc;
> >   
> > -	if (!auth) {
> > -		dev_warn_once(&chip->dev, "auth session is not active\n");
> > +	if (chip->auth) {
> > +		dev_warn_once(&chip->dev, "auth session is active\n");
> >   		return 0;
> >   	}
> >   
> > +	auth = kzalloc(sizeof(*auth), GFP_KERNEL);
> > +	if (!auth)
> > +		return -ENOMEM;
> > +
> >   	rc = tpm2_load_null(chip, &null_key);
> >   	if (rc)
> > -		goto out;
> > +		goto err;
> >   
> >   	auth->session = TPM_HEADER_SIZE;
> >   
> >   	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
> >   	if (rc)
> > -		goto out;
> > +		goto err;
> >   
> >   	/* salt key handle */
> >   	tpm_buf_append_u32(&buf, null_key);
> > @@ -1000,7 +1008,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> >   	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);
> > +	tpm_buf_append_salt(&buf, chip, auth);
> >   	/* session type (HMAC, audit or policy) */
> >   	tpm_buf_append_u8(&buf, TPM2_SE_HMAC);
> >   
> > @@ -1021,10 +1029,13 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> >   
> >   	tpm_buf_destroy(&buf);
> >   
> > -	if (rc)
> > -		goto out;
> > +	if (rc == TPM2_RC_SUCCESS) {
> > +		chip->auth = auth;
> > +		return 0;
> > +	}
> >   
> > - out:
> > +err:
>
> like in many other cases before kfree(auth):
> memzero_explicit(auth, sizeof(*auth));
>
> With this:
>
> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>

Thanks, or should we use kfree_sensitive()?

It has some additional functionality, which is missed now:

https://elixir.bootlin.com/linux/v6.11.5/source/mm/slab_common.c#L1339

I.e. kasan_unpoison().

BR, Jarkko

Re: [PATCH v7 4/5] tpm: Allocate chip->auth in tpm2_start_auth_session()

[Stefan Berger]

On 10/24/24 7:28 AM, Jarkko Sakkinen wrote:
> On Wed Oct 23, 2024 at 10:15 PM EEST, Stefan Berger wrote:
>>
>>
>> On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
>>> Move allocation of chip->auth to tpm2_start_auth_session() so that the
>>> field can be used as flag to tell whether auth session is active or not.
>>>
>>> Cc: stable@vger.kernel.org # v6.10+
>>> Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
>>> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
>>> ---
>>> v5:
>>> - No changes.
>>> v4:
>>> - Change to bug.
>>> v3:
>>> - No changes.
>>> v2:
>>> - A new patch.
>>> ---
>>>    drivers/char/tpm/tpm2-sessions.c | 43 +++++++++++++++++++-------------
>>>    1 file changed, 25 insertions(+), 18 deletions(-)
>>>
>>> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
>>> index 78c650ce4c9f..6e52785de9fd 100644
>>> --- a/drivers/char/tpm/tpm2-sessions.c
>>> +++ b/drivers/char/tpm/tpm2-sessions.c
>>> @@ -484,7 +484,8 @@ static void tpm2_KDFe(u8 z[EC_PT_SZ], const char *str, u8 *pt_u, u8 *pt_v,
>>>    	sha256_final(&sctx, out);
>>>    }
>>>    
>>> -static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
>>> +static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip,
>>> +				struct tpm2_auth *auth)
>>>    {
>>>    	struct crypto_kpp *kpp;
>>>    	struct kpp_request *req;
>>> @@ -543,7 +544,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
>>>    	sg_set_buf(&s[0], chip->null_ec_key_x, EC_PT_SZ);
>>>    	sg_set_buf(&s[1], chip->null_ec_key_y, EC_PT_SZ);
>>>    	kpp_request_set_input(req, s, EC_PT_SZ*2);
>>> -	sg_init_one(d, chip->auth->salt, EC_PT_SZ);
>>> +	sg_init_one(d, auth->salt, EC_PT_SZ);
>>>    	kpp_request_set_output(req, d, EC_PT_SZ);
>>>    	crypto_kpp_compute_shared_secret(req);
>>>    	kpp_request_free(req);
>>> @@ -554,8 +555,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
>>>    	 * This works because KDFe fully consumes the secret before it
>>>    	 * writes the salt
>>>    	 */
>>> -	tpm2_KDFe(chip->auth->salt, "SECRET", x, chip->null_ec_key_x,
>>> -		  chip->auth->salt);
>>> +	tpm2_KDFe(auth->salt, "SECRET", x, chip->null_ec_key_x, auth->salt);
>>>    
>>>     out:
>>>    	crypto_free_kpp(kpp);
>>> @@ -854,6 +854,8 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
>>>    			/* manually close the session if it wasn't consumed */
>>>    			tpm2_flush_context(chip, auth->handle);
>>>    		memzero_explicit(auth, sizeof(*auth));
>>> +		kfree(auth);
>>> +		chip->auth = NULL;
>>>    	} else {
>>>    		/* reset for next use  */
>>>    		auth->session = TPM_HEADER_SIZE;
>>> @@ -882,6 +884,8 @@ void tpm2_end_auth_session(struct tpm_chip *chip)
>>>    
>>>    	tpm2_flush_context(chip, auth->handle);
>>>    	memzero_explicit(auth, sizeof(*auth));
>>> +	kfree(auth);
>>> +	chip->auth = NULL;
>>>    }
>>>    EXPORT_SYMBOL(tpm2_end_auth_session);
>>>    
>>> @@ -970,25 +974,29 @@ 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;
>>> -	struct tpm2_auth *auth = chip->auth;
>>> -	int rc;
>>>    	u32 null_key;
>>> +	int rc;
>>>    
>>> -	if (!auth) {
>>> -		dev_warn_once(&chip->dev, "auth session is not active\n");
>>> +	if (chip->auth) {
>>> +		dev_warn_once(&chip->dev, "auth session is active\n");
>>>    		return 0;
>>>    	}
>>>    
>>> +	auth = kzalloc(sizeof(*auth), GFP_KERNEL);
>>> +	if (!auth)
>>> +		return -ENOMEM;
>>> +
>>>    	rc = tpm2_load_null(chip, &null_key);
>>>    	if (rc)
>>> -		goto out;
>>> +		goto err;
>>>    
>>>    	auth->session = TPM_HEADER_SIZE;
>>>    
>>>    	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
>>>    	if (rc)
>>> -		goto out;
>>> +		goto err;
>>>    
>>>    	/* salt key handle */
>>>    	tpm_buf_append_u32(&buf, null_key);
>>> @@ -1000,7 +1008,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>>>    	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);
>>> +	tpm_buf_append_salt(&buf, chip, auth);
>>>    	/* session type (HMAC, audit or policy) */
>>>    	tpm_buf_append_u8(&buf, TPM2_SE_HMAC);
>>>    
>>> @@ -1021,10 +1029,13 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
>>>    
>>>    	tpm_buf_destroy(&buf);
>>>    
>>> -	if (rc)
>>> -		goto out;
>>> +	if (rc == TPM2_RC_SUCCESS) {
>>> +		chip->auth = auth;
>>> +		return 0;
>>> +	}
>>>    
>>> - out:
>>> +err:
>>
>> like in many other cases before kfree(auth):
>> memzero_explicit(auth, sizeof(*auth));
>>
>> With this:
>>
>> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> 
> Thanks, or should we use kfree_sensitive()?
> 
> It has some additional functionality, which is missed now:
> 
> https://elixir.bootlin.com/linux/v6.11.5/source/mm/slab_common.c#L1339
> 
> I.e. kasan_unpoison().

And change the other ones that use memzero_explicit()?

> 
> BR, Jarkko
> 

Re: [PATCH v7 4/5] tpm: Allocate chip->auth in tpm2_start_auth_session()

[Jarkko Sakkinen]

On Thu Oct 24, 2024 at 3:59 PM EEST, Stefan Berger wrote:
>
>
> On 10/24/24 7:28 AM, Jarkko Sakkinen wrote:
> > On Wed Oct 23, 2024 at 10:15 PM EEST, Stefan Berger wrote:
> >>
> >>
> >> On 10/21/24 1:39 AM, Jarkko Sakkinen wrote:
> >>> Move allocation of chip->auth to tpm2_start_auth_session() so that the
> >>> field can be used as flag to tell whether auth session is active or not.
> >>>
> >>> Cc: stable@vger.kernel.org # v6.10+
> >>> Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> >>> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
> >>> ---
> >>> v5:
> >>> - No changes.
> >>> v4:
> >>> - Change to bug.
> >>> v3:
> >>> - No changes.
> >>> v2:
> >>> - A new patch.
> >>> ---
> >>>    drivers/char/tpm/tpm2-sessions.c | 43 +++++++++++++++++++-------------
> >>>    1 file changed, 25 insertions(+), 18 deletions(-)
> >>>
> >>> diff --git a/drivers/char/tpm/tpm2-sessions.c b/drivers/char/tpm/tpm2-sessions.c
> >>> index 78c650ce4c9f..6e52785de9fd 100644
> >>> --- a/drivers/char/tpm/tpm2-sessions.c
> >>> +++ b/drivers/char/tpm/tpm2-sessions.c
> >>> @@ -484,7 +484,8 @@ static void tpm2_KDFe(u8 z[EC_PT_SZ], const char *str, u8 *pt_u, u8 *pt_v,
> >>>    	sha256_final(&sctx, out);
> >>>    }
> >>>    
> >>> -static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
> >>> +static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip,
> >>> +				struct tpm2_auth *auth)
> >>>    {
> >>>    	struct crypto_kpp *kpp;
> >>>    	struct kpp_request *req;
> >>> @@ -543,7 +544,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
> >>>    	sg_set_buf(&s[0], chip->null_ec_key_x, EC_PT_SZ);
> >>>    	sg_set_buf(&s[1], chip->null_ec_key_y, EC_PT_SZ);
> >>>    	kpp_request_set_input(req, s, EC_PT_SZ*2);
> >>> -	sg_init_one(d, chip->auth->salt, EC_PT_SZ);
> >>> +	sg_init_one(d, auth->salt, EC_PT_SZ);
> >>>    	kpp_request_set_output(req, d, EC_PT_SZ);
> >>>    	crypto_kpp_compute_shared_secret(req);
> >>>    	kpp_request_free(req);
> >>> @@ -554,8 +555,7 @@ static void tpm_buf_append_salt(struct tpm_buf *buf, struct tpm_chip *chip)
> >>>    	 * This works because KDFe fully consumes the secret before it
> >>>    	 * writes the salt
> >>>    	 */
> >>> -	tpm2_KDFe(chip->auth->salt, "SECRET", x, chip->null_ec_key_x,
> >>> -		  chip->auth->salt);
> >>> +	tpm2_KDFe(auth->salt, "SECRET", x, chip->null_ec_key_x, auth->salt);
> >>>    
> >>>     out:
> >>>    	crypto_free_kpp(kpp);
> >>> @@ -854,6 +854,8 @@ int tpm_buf_check_hmac_response(struct tpm_chip *chip, struct tpm_buf *buf,
> >>>    			/* manually close the session if it wasn't consumed */
> >>>    			tpm2_flush_context(chip, auth->handle);
> >>>    		memzero_explicit(auth, sizeof(*auth));
> >>> +		kfree(auth);
> >>> +		chip->auth = NULL;
> >>>    	} else {
> >>>    		/* reset for next use  */
> >>>    		auth->session = TPM_HEADER_SIZE;
> >>> @@ -882,6 +884,8 @@ void tpm2_end_auth_session(struct tpm_chip *chip)
> >>>    
> >>>    	tpm2_flush_context(chip, auth->handle);
> >>>    	memzero_explicit(auth, sizeof(*auth));
> >>> +	kfree(auth);
> >>> +	chip->auth = NULL;
> >>>    }
> >>>    EXPORT_SYMBOL(tpm2_end_auth_session);
> >>>    
> >>> @@ -970,25 +974,29 @@ 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;
> >>> -	struct tpm2_auth *auth = chip->auth;
> >>> -	int rc;
> >>>    	u32 null_key;
> >>> +	int rc;
> >>>    
> >>> -	if (!auth) {
> >>> -		dev_warn_once(&chip->dev, "auth session is not active\n");
> >>> +	if (chip->auth) {
> >>> +		dev_warn_once(&chip->dev, "auth session is active\n");
> >>>    		return 0;
> >>>    	}
> >>>    
> >>> +	auth = kzalloc(sizeof(*auth), GFP_KERNEL);
> >>> +	if (!auth)
> >>> +		return -ENOMEM;
> >>> +
> >>>    	rc = tpm2_load_null(chip, &null_key);
> >>>    	if (rc)
> >>> -		goto out;
> >>> +		goto err;
> >>>    
> >>>    	auth->session = TPM_HEADER_SIZE;
> >>>    
> >>>    	rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_START_AUTH_SESS);
> >>>    	if (rc)
> >>> -		goto out;
> >>> +		goto err;
> >>>    
> >>>    	/* salt key handle */
> >>>    	tpm_buf_append_u32(&buf, null_key);
> >>> @@ -1000,7 +1008,7 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> >>>    	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);
> >>> +	tpm_buf_append_salt(&buf, chip, auth);
> >>>    	/* session type (HMAC, audit or policy) */
> >>>    	tpm_buf_append_u8(&buf, TPM2_SE_HMAC);
> >>>    
> >>> @@ -1021,10 +1029,13 @@ int tpm2_start_auth_session(struct tpm_chip *chip)
> >>>    
> >>>    	tpm_buf_destroy(&buf);
> >>>    
> >>> -	if (rc)
> >>> -		goto out;
> >>> +	if (rc == TPM2_RC_SUCCESS) {
> >>> +		chip->auth = auth;
> >>> +		return 0;
> >>> +	}
> >>>    
> >>> - out:
> >>> +err:
> >>
> >> like in many other cases before kfree(auth):
> >> memzero_explicit(auth, sizeof(*auth));
> >>
> >> With this:
> >>
> >> Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
> > 
> > Thanks, or should we use kfree_sensitive()?
> > 
> > It has some additional functionality, which is missed now:
> > 
> > https://elixir.bootlin.com/linux/v6.11.5/source/mm/slab_common.c#L1339
> > 
> > I.e. kasan_unpoison().
>
> And change the other ones that use memzero_explicit()?

Yeah, might be a good idea too. Don't invent your own "safe primitives"
sounds like a good idea to me at least...

>
> > 
> > BR, Jarkko
> > 

BR, Jarkko