linux-kernel - Re: [PATCH v3 2/3] ima: Return int in the functions to measure a buffer

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Message-ID: <2f4920dbdb16156e1af5cf78f592a5cf07ec3176.camel@linux.ibm.com>
Date:   Mon, 19 Jul 2021 16:28:11 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...wei.com>, paul@...l-moore.com
Cc:     stephen.smalley.work@...il.com, prsriva02@...il.com,
        tusharsu@...ux.microsoft.com, nramas@...ux.microsoft.com,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, selinux@...r.kernel.org
Subject: Re: [PATCH v3 2/3] ima: Return int in the functions to measure a
 buffer

Hi Roberto,

On Mon, 2021-07-05 at 11:09 +0200, Roberto Sassu wrote:
> ima_measure_critical_data() and process_buffer_measurement() currently
> don't return a result. A caller wouldn't be able to know whether those
> functions were executed successfully.

Missing is an explanation as to why these functions aren't currently
returning a result.   The LSM/IMA hooks only return a negative result
for failure to appraise a file's integrity, not measure a file.  Only
failure to appraise a file's integrity results in preventing the file
from being read/executed/mmaped.  Other failures are only audited.

> 
> This patch modifies the return type from void to int, and returns 0 if the
> buffer has been successfully measured, a negative value otherwise.

Needed here is an explanation as to why ima_measure_critical_data() is
special.

> 
> Also, this patch does not modify the behavior of existing callers by
> processing the returned value. For those, the return value is ignored.

I agree that the existing behavior shouldn't change, but will this
result in the bots complaining?

thanks,

Mimi