linux-kernel - Re: [PATCH v3 06/16] tpm: clean up tpm_try

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Date:   Mon, 5 Nov 2018 17:20:33 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        linux-integrity@...r.kernel.org
Cc:     linux-security-module@...r.kernel.org,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        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>,
        Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 06/16] tpm: clean up tpm_try_transmit() error handling
 flow

On 11/4/18 8:45 PM, Jarkko Sakkinen wrote:
> Move locking, locality handling and power management to tpm_transmit()
> in order to simplify the flow.
>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
> ---
>   drivers/char/tpm/tpm-interface.c | 90 ++++++++++++++------------------
>   1 file changed, 39 insertions(+), 51 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c
> index ecda6f96cde0..0f343407daf8 100644
> --- a/drivers/char/tpm/tpm-interface.c
> +++ b/drivers/char/tpm/tpm-interface.c
> @@ -171,7 +171,6 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
>   	ssize_t len = 0;
>   	u32 count, ordinal;
>   	unsigned long stop;
> -	bool need_locality;
>
>   	rc = tpm_validate_command(chip, space, buf, bufsiz);
>   	if (rc == -EINVAL)
> @@ -201,30 +200,9 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
>   		return -E2BIG;
>   	}
>
> -	if (!(flags & TPM_TRANSMIT_UNLOCKED) && !(flags & TPM_TRANSMIT_NESTED))
> -		mutex_lock(&chip->tpm_mutex);
> -
> -	if (chip->ops->clk_enable != NULL)
> -		chip->ops->clk_enable(chip, true);
> -
> -	/* Store the decision as chip->locality will be changed. */
> -	need_locality = chip->locality == -1;
> -
> -	if (need_locality) {
> -		rc = tpm_request_locality(chip, flags);
> -		if (rc < 0) {
> -			need_locality = false;
> -			goto out_locality;
> -		}
> -	}
> -
> -	rc = tpm_cmd_ready(chip, flags);
> -	if (rc)
> -		goto out_locality;
> -
>   	rc = tpm2_prepare_space(chip, space, ordinal, buf);


tpm2_prepare_space() may issue TPM commands itself. Following your tree 
the move should now put the clk_enable() and tpm_request_locality() in 
the path. So, looks good.


>   	if (rc)
> -		goto out_idle;
> +		return rc;
>
>   	rc = chip->ops->send(chip, buf, count);
>   	if (rc < 0) {
> @@ -265,40 +243,16 @@ static ssize_t tpm_try_transmit(struct tpm_chip *chip,
>   		rc = len;
>   		dev_err(&chip->dev,
>   			"tpm_transmit: tpm_recv: error %d\n", rc);
> -		goto out_idle;
> -	} else if (len < TPM_HEADER_SIZE) {
> -		rc = -EFAULT;
> -		goto out_idle;
> -	}
> -
> -	if (len != be32_to_cpu(header->length)) {
> +		tpm2_flush_space(chip);
> +	} else if (len < TPM_HEADER_SIZE || len != be32_to_cpu(header->length))
>   		rc = -EFAULT;
> -		goto out_idle;
> -	}
>
>   out_space:
> -	if (rc) {
> +	if (rc)
>   		tpm2_flush_space(chip);
> -	} else {
> +	else
>   		rc = tpm2_commit_space(chip, space, ordinal, buf, &len);
> -		if (rc)
> -			dev_err(&chip->dev, "tpm2_commit_space: error %d\n",
> -				rc);


This should have been removed in the previous patch...


> -	}
> -
> -out_idle:
> -	/* may fail but do not override previous error value in rc */
> -	tpm_go_idle(chip, flags);
> -
> -out_locality:
> -	if (need_locality)
> -		tpm_relinquish_locality(chip, flags);
> -
> -	if (chip->ops->clk_enable != NULL)
> -		chip->ops->clk_enable(chip, false);
>
> -	if (!(flags & TPM_TRANSMIT_UNLOCKED) && !(flags & TPM_TRANSMIT_NESTED))
> -		mutex_unlock(&chip->tpm_mutex);
>   	return rc ? rc : len;
>   }
>
> @@ -328,6 +282,7 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
>   	/* space for header and handles */
>   	u8 save[TPM_HEADER_SIZE + 3*sizeof(u32)];
>   	unsigned int delay_msec = TPM2_DURATION_SHORT;
> +	bool has_locality = false;
>   	u32 rc = 0;
>   	ssize_t ret;
>   	const size_t save_size = min(space ? sizeof(save) : TPM_HEADER_SIZE,
> @@ -343,7 +298,40 @@ ssize_t tpm_transmit(struct tpm_chip *chip, struct tpm_space *space,
>   	memcpy(save, buf, save_size);
>
>   	for (;;) {
> +		if (!(flags & TPM_TRANSMIT_UNLOCKED) &&
> +		    !(flags & TPM_TRANSMIT_NESTED))
> +			mutex_lock(&chip->tpm_mutex);
> +
> +		if (chip->ops->clk_enable != NULL)
> +			chip->ops->clk_enable(chip, true);
> +
> +		if (chip->locality == -1) {
> +			ret = tpm_request_locality(chip, flags);
> +			if (ret)
> +				goto out_locality;
> +			has_locality = true;
> +		}
> +
> +		ret = tpm_cmd_ready(chip, flags);
> +		if (ret)
> +			goto out_locality;
> +
>   		ret = tpm_try_transmit(chip, space, buf, bufsiz, flags);
> +
> +		/* This may fail but do not override ret. */
> +		tpm_go_idle(chip, flags);
> +
> +out_locality:
> +		if (has_locality)
> +			tpm_relinquish_locality(chip, flags);

Safer to also put has_locality = false here ?


> +
> +		if (chip->ops->clk_enable != NULL)
> +			chip->ops->clk_enable(chip, false);
> +
> +		if (!(flags & TPM_TRANSMIT_UNLOCKED) &&
> +		    !(flags & TPM_TRANSMIT_NESTED))
> +			mutex_unlock(&chip->tpm_mutex);
> +
>   		if (ret < 0)
>   			break;
>   		rc = be32_to_cpu(header->return_code);