linux-kernel - Re: [PATCH 3/3] tpm: make locality request return value consistent

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Date: Fri, 02 Feb 2024 00:49:07 +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 3/3] tpm: make locality request return value consistent

On Wed Jan 31, 2024 at 7:08 PM EET, Daniel P. Smith wrote:
> The function tpm_tis_request_locality() is expected to return the locality
> value that was requested, or a negative error code upon failure. If it is called
> while locality_count of struct tis_data is non-zero, no actual locality request
> will be sent. Because the ret variable is initially set to 0, the
> locality_count will still get increased, and the function will return 0. For a
> caller, this would indicate that locality 0 was successfully requested and not
> the state changes just mentioned.
>
> Additionally, the function __tpm_tis_request_locality() provides inconsistent
> error codes. It will provide either a failed IO write or a -1 should it have
> timed out waiting for locality request to succeed.
>
> This commit changes __tpm_tis_request_locality() to return valid negative error
> codes to reflect the reason it fails. It then adjusts the return value check in
> tpm_tis_request_locality() to check for a non-negative return value before
> incrementing locality_cout. In addition, the initial value of the ret value is
> set to a negative error to ensure the check does not pass if
> __tpm_tis_request_locality() is not called.

This is way way too abtract explanation and since I don't honestly
understand what I'm reading, the code changes look bunch of arbitrary
changes with no sound logic as a whole.

Please do not add more text to it. Instead write something more
understandable.

Again, we would need a legit scenario for each and any return value
change.<F49>

BR, Jarkko