[PATCH] tpm: Fix the value of TPM2_SE_TRIAL

[PATCH] tpm: Fix the value of TPM2_SE_TRIAL

[Alban Munari via B4 Relay]

From: Alban Munari <alban.kernel@gmail.com>

The TPM 2.0 Library specification, Part 2: Structures, defines the
session types (TPM_SE) as TPM_SE_HMAC = 0x00, TPM_SE_POLICY = 0x01 and
TPM_SE_TRIAL = 0x03. TPM2_SE_TRIAL is defined as 0x02, which is not a
session type: TPM2_StartAuthSession with it fails with TPM_RC_VALUE on
the sessionType parameter, as swtpm 0.11.0 shows.

No code in the kernel uses TPM2_SE_TRIAL, so nothing changes at run
time. The TPM 2.0 selftests already define it as 0x03 in
tools/testing/selftests/tpm2/tpm2.py.

This change was found and written with an AI coding assistant (Claude
Opus 5.5, Anthropic), while building trial sessions on an AMD fTPM with
the value 0x03.

Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
Signed-off-by: Alban Munari <alban.kernel@gmail.com>
---
 include/linux/tpm_command.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/tpm_command.h b/include/linux/tpm_command.h
index fc446a1282e2..076ee8ce816c 100644
--- a/include/linux/tpm_command.h
+++ b/include/linux/tpm_command.h
@@ -171,7 +171,7 @@ struct tpm1_get_random_out {
 enum tpm2_session_types {
 	TPM2_SE_HMAC	= 0x00,
 	TPM2_SE_POLICY	= 0x01,
-	TPM2_SE_TRIAL	= 0x02,
+	TPM2_SE_TRIAL	= 0x03,
 };
 
 enum tpm2_timeouts {

---
base-commit: 05441d697f7f9a927264f4058cbbc6a03dfcac9d
change-id: 20261108-tpm-se-trial-580bef9b4f17

Best regards,
--  
Alban Munari <alban.kernel@gmail.com>

Re: [PATCH] tpm: Fix the value of TPM2_SE_TRIAL

[Jarkko Sakkinen]

On Sun, Nov 08, 2026 at 06:05:39PM +0000, Alban Munari via B4 Relay wrote:
> From: Alban Munari <alban.kernel@gmail.com>
> 
> The TPM 2.0 Library specification, Part 2: Structures, defines the
> session types (TPM_SE) as TPM_SE_HMAC = 0x00, TPM_SE_POLICY = 0x01 and
> TPM_SE_TRIAL = 0x03. TPM2_SE_TRIAL is defined as 0x02, which is not a
> session type: TPM2_StartAuthSession with it fails with TPM_RC_VALUE on
> the sessionType parameter, as swtpm 0.11.0 shows.
> 
> No code in the kernel uses TPM2_SE_TRIAL, so nothing changes at run
> time. The TPM 2.0 selftests already define it as 0x03 in
> tools/testing/selftests/tpm2/tpm2.py.
> 
> This change was found and written with an AI coding assistant (Claude
> Opus 5.5, Anthropic), while building trial sessions on an AMD fTPM with
> the value 0x03.

Please delete this paragraph. It is your responsibility to do the
fact checking. I.e. refer to a section in appropriate TCG spec that
defines this instead.

> 
> Fixes: 699e3efd6c64 ("tpm: Add HMAC session start and end functions")
> Signed-off-by: Alban Munari <alban.kernel@gmail.com>

If no code uses it why fixes-tag?

> ---
>  include/linux/tpm_command.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/tpm_command.h b/include/linux/tpm_command.h
> index fc446a1282e2..076ee8ce816c 100644
> --- a/include/linux/tpm_command.h
> +++ b/include/linux/tpm_command.h
> @@ -171,7 +171,7 @@ struct tpm1_get_random_out {
>  enum tpm2_session_types {
>  	TPM2_SE_HMAC	= 0x00,
>  	TPM2_SE_POLICY	= 0x01,
> -	TPM2_SE_TRIAL	= 0x02,
> +	TPM2_SE_TRIAL	= 0x03,
>  };
>  
>  enum tpm2_timeouts {
> 
> ---
> base-commit: 05441d697f7f9a927264f4058cbbc6a03dfcac9d
> change-id: 20261108-tpm-se-trial-580bef9b4f17
> 
> Best regards,
> --  
> Alban Munari <alban.kernel@gmail.com>
> 
> 

I think better action would be delete the enum and change the single
site to  tpm_buf_append_u8(buf, 0x00 /* HMAC */);

Br, Jarkko