linux-kernel - Re: [PATCH V10 2/3] IMA: Define a new template field buf

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Message-Id: <878stmr4lo.fsf@morokweng.localdomain>
Date:   Thu, 27 Jun 2019 20:27:47 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     Prakhar Srivastava <prsriva02@...il.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, roberto.sassu@...wei.com,
        vgoyal@...hat.com
Subject: Re: [PATCH V10 2/3] IMA: Define a new template field buf


Mimi Zohar <zohar@...ux.ibm.com> writes:

> On Mon, 2019-06-24 at 19:03 -0300, Thiago Jung Bauermann wrote:
>> Hello Prakhar,
>> 
>> Prakhar Srivastava <prsriva02@...il.com> writes:
>> 
>> > diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
>> > index 00dd5a434689..a01a17e5c581 100644
>> > --- a/security/integrity/ima/ima_template.c
>> > +++ b/security/integrity/ima/ima_template.c
>> > @@ -26,6 +26,7 @@ static struct ima_template_desc builtin_templates[] = {
>> >  	{.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
>> >  	{.name = "ima-ng", .fmt = "d-ng|n-ng"},
>> >  	{.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
>> > +	{.name = "ima-buf", .fmt = "d-ng|n-ng|buf"},
>> >  	{.name = "", .fmt = ""},	/* placeholder for a custom format */
>> >  };
>> >
>> > @@ -43,6 +44,8 @@ static const struct ima_template_field supported_fields[] = {
>> >  	 .field_show = ima_show_template_string},
>> >  	{.field_id = "sig", .field_init = ima_eventsig_init,
>> >  	 .field_show = ima_show_template_sig},
>> > +	{.field_id = "buf", .field_init = ima_eventbuf_init,
>> > +	 .field_show = ima_show_template_buf},
>> >  };
>> >  #define MAX_TEMPLATE_NAME_LEN 15
>> 
>> Currently, MAX_TEMPLATE_NAME_LEN is the length of a template that
>> contains all valid fields. It may make sense to increase it since
>> there's a new field being added.
>> 
>> I suggest using a sizeof() to show where the number comes from (and
>> which can be visually shown to be correct):
>> 
>> #define MAX_TEMPLATE_NAME_LEN sizeof("d|n|d-ng|n-ng|sig|buf")
>> 
>> The sizeof() is calculated at compile time.
>
> MAX_TEMPLATE_NAME_LEN is used when restoring measurements carried over
> from a kexec.  'd' and 'd-ng' should not both be defined in the
> template description, nor should 'n' and 'n-ng'.

Ah, makes sense. Thanks for that information. 

> Even without the
> duplication, the MAX_TEPLATE_NAME_LEN is greater than the current 15.
>
> Thiago, could you address this as a separate patch?

Yes, I just sent a patch.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center