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

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 */

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