linux-kernel - Re: [PATCH v3 03/16] tpm: return 0 from pcrs_show() when tpm1_pcr

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Date:   Mon, 5 Nov 2018 16:54:52 -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 03/16] tpm: return 0 from pcrs_show() when
 tpm1_pcr_read() fails

On 11/4/18 8:45 PM, 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>
> ---
>   drivers/char/tpm/tpm-sysfs.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm-sysfs.c b/drivers/char/tpm/tpm-sysfs.c
> index 7ed7eb6f906a..d3b05c7526c8 100644
> --- a/drivers/char/tpm/tpm-sysfs.c
> +++ b/drivers/char/tpm/tpm-sysfs.c
> @@ -115,13 +115,15 @@ static ssize_t pcrs_show(struct device *dev, struct device_attribute *attr,
>   	for (i = 0; i < num_pcrs; i++) {
>   		rc = tpm1_pcr_read(chip, i, digest);
>   		if (rc)
> -			break;
> +			goto out;

Previous patch said "Return zero when tpm_buf_init() fails as we do for 
other functions in tpm-sysfs.c.". Why not return 0 in this case as well?


>   		str += sprintf(str, "PCR-%02d: ", i);
>   		for (j = 0; j < TPM_DIGEST_SIZE; j++)
>   			str += sprintf(str, "%02X ", digest[j]);
>   		str += sprintf(str, "\n");
>   	}
> -	return str - buf;
> +	rc = str - buf;
> +out:
> +	return rc;
>   }
>   static DEVICE_ATTR_RO(pcrs);
>