linux-kernel - Re: [PATCH v5 03/17] tpm: return 0 from pcrs_show() when tpm1_pcr

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Message-Id: <cfc87ece-d69f-3e14-d2bc-c3a9f350b48b@linux.ibm.com>
Date:   Thu, 8 Nov 2018 09:52:14 -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 v5 03/17] tpm: return 0 from pcrs_show() when
 tpm1_pcr_read() fails

On 11/8/18 9:15 AM, Jarkko Sakkinen wrote:
> Do not print partial list of PCRs when tpm1_pcr_read() fails but instead
> return 0 from pcrs_show(). This is consistent behavior with other sysfs
> functions.
>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>

Reviewed-by: Stefan Berger <stefanb@...ux.ibm.com>


> ---
>   drivers/char/tpm/tpm-sysfs.c | 13 ++++++-------
>   1 file changed, 6 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
> index 7ed7eb6f906a..928d4e839bb7 100644
> --- a/drivers/char/tpm/tpm-sysfs.c
> +++ b/drivers/char/tpm/tpm-sysfs.c
> @@ -100,22 +100,21 @@ static ssize_t pcrs_show(struct device *dev, struct device_attribute *attr,
>   {
>   	cap_t cap;
>   	u8 digest[TPM_DIGEST_SIZE];
> -	ssize_t rc;
>   	u32 i, j, num_pcrs;
>   	char *str = buf;
>   	struct tpm_chip *chip = to_tpm_chip(dev);
>
> -	rc = tpm1_getcap(chip, TPM_CAP_PROP_PCR, &cap,
> -			 "attempting to determine the number of PCRS",
> -			 sizeof(cap.num_pcrs));
> -	if (rc)
> +	if (tpm1_getcap(chip, TPM_CAP_PROP_PCR, &cap,
> +			"attempting to determine the number of PCRS",
> +			sizeof(cap.num_pcrs)))
>   		return 0;
>
>   	num_pcrs = be32_to_cpu(cap.num_pcrs);
>   	for (i = 0; i < num_pcrs; i++) {
> -		rc = tpm1_pcr_read(chip, i, digest);
> -		if (rc)
> +		if (tpm1_pcr_read(chip, i, digest)) {
> +			str = buf;
>   			break;
> +		}
>   		str += sprintf(str, "PCR-%02d: ", i);
>   		for (j = 0; j < TPM_DIGEST_SIZE; j++)
>   			str += sprintf(str, "%02X ", digest[j]);