linux-kernel - Re: [PATCH v3 2/6] IMA: change process_buffer_measurement return type from void to int

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Message-ID: <b4cc6ec3-a58b-df2b-2de9-864775ae2a5f@linux.microsoft.com>
Date:   Fri, 11 Sep 2020 09:22:44 -0700
From:   Tushar Sugandhi <tusharsu@...ux.microsoft.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>, stephen.smalley.work@...il.com,
        casey@...aufler-ca.com, agk@...hat.com, snitzer@...hat.com,
        gmazyland@...il.com
Cc:     tyhicks@...ux.microsoft.com, sashal@...nel.org, jmorris@...ei.org,
        nramas@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        selinux@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, dm-devel@...hat.com
Subject: Re: [PATCH v3 2/6] IMA: change process_buffer_measurement return type
 from void to int



On 2020-08-31 4:36 a.m., Mimi Zohar wrote:
> On Thu, 2020-08-27 at 18:57 -0700, Tushar Sugandhi wrote:
>> process_buffer_measurement() does not return the result of the operation.
>> Therefore, the consumers of this function cannot act on it, if needed.
>>
>> Update return type of process_buffer_measurement() from void to int.
> 
> Failure to measure may be audited, but should never fail.  This is one
> of the main differences between secure and trusted boot concepts.
> Notice in process_measurement() that -EACCES is only returned for
> appraisal.
> 
> Returning a failure from process_buffer_measurement() in itself isn't a
> problem, as long as the failure isn't returned to the LSM/IMA hook.
> However,  just as the callers of  process_measurement() originally
> processed the result, that processing was moved into
> process_measurement() [1].
> 
> Mimi
> 
> [1] 750943a30714 ima: remove enforce checking duplication
> 
I can ignore the result of process_buffer_measurement() in
ima_measure_critical_data(), and make  ima_measure_critical_data()
return type "void".

But currently ima_measure_critical_data() is the only place where the
results of p_b_m() are being used.
So I might as well just revert back the return type of p_b_m() to
the original "void".