linux-kernel - Re: [PATCH] char: tpm: ftpm_tee: use kernel login identifier

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Message-Id: <CSIXYHYSW45R.O3II0HIIHZV4@suppilovahvero>
Date:   Thu, 11 May 2023 01:12:41 +0300
From:   "Jarkko Sakkinen" <jarkko@...nel.org>
To:     "Etienne Carriere" <etienne.carriere@...aro.org>,
        <linux-kernel@...r.kernel.org>
Cc:     "Peter Huewe" <peterhuewe@....de>,
        "Jason Gunthorpe" <jgg@...pe.ca>, <linux-integrity@...r.kernel.org>
Subject: Re: [PATCH] char: tpm: ftpm_tee: use kernel login identifier

On Fri May 5, 2023 at 9:43 PM EEST, Etienne Carriere wrote:
> Changes fTPM TEE driver to open the TEE session with REE kernel login
> identifier rather than public login. This is needed in case fTPM service
> it denied to user land application and restricted to kernel operating
> system services only.
>
> Signed-off-by: Etienne Carriere <etienne.carriere@...aro.org>


Can you bring up a little context here?

What is REE login?
Does it break backwards compatibility to switch?
What kind of scenario we are talking about? What does it mean in plain
English when fTPM service is denied.
What is fTPM service?

> ---
>  drivers/char/tpm/tpm_ftpm_tee.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/tpm_ftpm_tee.c b/drivers/char/tpm/tpm_ftpm_tee.c
> index 528f35b14fb6..6d32e260af43 100644
> --- a/drivers/char/tpm/tpm_ftpm_tee.c
> +++ b/drivers/char/tpm/tpm_ftpm_tee.c
> @@ -241,7 +241,7 @@ static int ftpm_tee_probe(struct device *dev)
>  	/* Open a session with fTPM TA */
>  	memset(&sess_arg, 0, sizeof(sess_arg));
>  	export_uuid(sess_arg.uuid, &ftpm_ta_uuid);
> -	sess_arg.clnt_login = TEE_IOCTL_LOGIN_PUBLIC;
> +	sess_arg.clnt_login = TEE_IOCTL_LOGIN_REE_KERNEL;
>  	sess_arg.num_params = 0;
>  
>  	rc = tee_client_open_session(pvt_data->ctx, &sess_arg, NULL);
> -- 
> 2.25.1

BR, Jarkko