linux-kernel - Re: [PATCH 2/3] tpm: ensure tpm is in known state at startup

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Date: Fri, 02 Feb 2024 00:33:25 +0200
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Daniel P. Smith" <dpsmith@...rtussolutions.com>, "Jason Gunthorpe"
 <jgg@...pe.ca>, <linux-integrity@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Cc: "Ross Philipson" <ross.philipson@...cle.com>, "Peter Huewe"
 <peterhuewe@....de>
Subject: Re: [PATCH 2/3] tpm: ensure tpm is in known state at startup

On Wed Jan 31, 2024 at 7:08 PM EET, Daniel P. Smith wrote:
> When tis core initializes, it assumes all localities are closed. There
       ~~~~~~~~
       tpm_tis_core

> are cases when this may not be the case. This commit addresses this by
> ensuring all localities are closed before initializing begins.

Remove the last sentence and replace with this paragraph:

"Address this by ensuring all the localities are closed in the beginning
of tpm_tis_core_init(). There are environments, like Intel TXT, which
may leave a locality open. Close all localities to start from a known
state."

BTW, why we should motivated to take this patch anyway?

Since the patch is not marked as a bug fix the commit message must pitch
why it is important to care.

> Signed-off-by: Daniel P. Smith <dpsmith@...rtussolutions.com>
> Signed-off-by: Ross Philipson <ross.philipson@...cle.com>
> ---
>  drivers/char/tpm/tpm_tis_core.c | 11 ++++++++++-
>  include/linux/tpm.h             |  6 ++++++
>  2 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
> index 4176d3bd1f04..5709f87991d9 100644
> --- a/drivers/char/tpm/tpm_tis_core.c
> +++ b/drivers/char/tpm/tpm_tis_core.c
> @@ -1109,7 +1109,7 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  	u32 intmask;
>  	u32 clkrun_val;
>  	u8 rid;
> -	int rc, probe;
> +	int rc, probe, i;
>  	struct tpm_chip *chip;
>  
>  	chip = tpmm_chip_alloc(dev, &tpm_tis);
> @@ -1170,6 +1170,15 @@ int tpm_tis_core_init(struct device *dev, struct tpm_tis_data *priv, int irq,
>  		goto out_err;
>  	}
>  
> +	/*
> +	 * There are environments, like Intel TXT, that may leave a TPM
> +	 * locality open. Close all localities to start from a known state.
> +	 */
> +	for (i = 0; i <= TPM_MAX_LOCALITY; i++) {
> +		if (check_locality(chip, i))
> +			tpm_tis_relinquish_locality(chip, i);
> +	}
> +
>  	/* Take control of the TPM's interrupt hardware and shut it off */
>  	rc = tpm_tis_read32(priv, TPM_INT_ENABLE(priv->locality), &intmask);
>  	if (rc < 0)
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index 4ee9d13749ad..abe0d44d00ee 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -116,6 +116,12 @@ struct tpm_chip_seqops {
>  	const struct seq_operations *seqops;
>  };
>  
> +/*
> + * The maximum locality (0 - 4) for a TPM, as defined in section 3.2 of the
> + * Client Platform Profile Specification.
> + */
> +#define TPM_MAX_LOCALITY		4
> +
>  struct tpm_chip {
>  	struct device dev;
>  	struct device devs;

Is there a dependency to 1/3?

BR, Jarkko