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

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Date:   Thu, 27 Jun 2019 11:08:31 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Prakhar Srivastava <prsriva02@...il.com>
Cc:     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

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'.  Even without the
duplication, the MAX_TEPLATE_NAME_LEN is greater than the current 15.

Thiago, could you address this as a separate patch?

thanks!

Mimi