linux-kernel - Re: [PATCH v11 00/16] Remove nested TPM operations

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Message-ID: <20190208115031.GB11755@linux.intel.com>
Date:   Fri, 8 Feb 2019 13:50:31 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Stefan Berger <stefanb@...ux.ibm.com>
Cc:     Alexander Steffen <Alexander.Steffen@...ineon.com>,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        Peter Huewe <PeterHuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Tomas Winkler <tomas.winkler@...el.com>,
        Tadeusz Struk <tadeusz.struk@...el.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>
Subject: Re: [PATCH v11 00/16] Remove nested TPM operations

On Thu, Feb 07, 2019 at 09:14:54PM -0500, Stefan Berger wrote:
> +EXPORT_SYMBOL_GPL(tpm_chip_start);
> 
>  /**
>   * tpm_chip_stop() - power off the TPM
> @@ -131,7 +132,7 @@ void tpm_chip_stop(struct tpm_chip *chip)
>      if (chip->ops->clk_enable)
>          chip->ops->clk_enable(chip, false);
>  }
> -
> +EXPORT_SYMBOL_GPL(tpm_chip_stop);

These are already fixed.

>  /**
>   * tpm_try_get_ops() - Get a ref to the tpm_chip
> @@ -474,8 +475,11 @@ static void tpm_del_char_device(struct tpm_chip *chip)
> 
>      /* Make the driver uncallable. */
>      down_write(&chip->ops_sem);
> -    if (chip->flags & TPM_CHIP_FLAG_TPM2)
> +    if (chip->flags & TPM_CHIP_FLAG_TPM2) {
> +        tpm_chip_start(chip, 0);
>          tpm2_shutdown(chip, TPM2_SU_CLEAR);
> +        tpm_chip_stop(chip, 0);
> +    }

Thanks!

Needs to be also done in tpm_pm_suspend() but there it is also better to
take locks because in-kernel subsystem might be using TPM even user
space has been freezed (e.g. hibernate possibly in future).

mutex_lock(&chip->tpm_mutex);
if (!tpm_chip_start(chip, 0)) {
	tpm2_shutdown(chip, TPM2_SU_CLEAR);
	tpm_chip_stop(chip, 0);
}
mutex_unlock(&chip->tpm_mutex);

Fixed now.

>      chip->ops = NULL;
>      up_write(&chip->ops_sem);
>  }
> diff --git a/drivers/char/tpm/tpm-interface.c
> b/drivers/char/tpm/tpm-interface.c
> index 02e8cffd1163..fcd845ad8c3c 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -124,6 +124,8 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
> void *buf, size_t bufsiz)
>          dev_err(&chip->dev, "tpm_transmit: tpm_recv: error %d\n", rc);
>      } else if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
>          rc = -EFAULT;
> +    else
> +        rc = 0;

Why is this needed?

/Jarkko