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Message-ID: <1455156500.2538.268.camel@linux.vnet.ibm.com>
Subject: Re: [PATCH v3 19/22] ima: support for kexec image and initramfs
From: Mimi Zohar <zohar@linux.vnet.ibm.com>
To: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>
Cc: linux-security-module <linux-security-module@vger.kernel.org>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	David Woodhouse <dwmw2@infradead.org>,
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	linux-modules@vger.kernel.org,
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	David Howells <dhowells@redhat.com>, fsdevel@vger.kernel.org,
	Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	"Luis R. Rodriguez" <mcgrof@suse.com>
Date: Wed, 10 Feb 2016 21:08:20 -0500
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On Thu, 2016-02-11 at 01:55 +0200, Dmitry Kasatkin wrote:
> On Feb 11, 2016 1:22 AM, "Mimi Zohar" <zohar@linux.vnet.ibm.com> wrote:
> >
> > On Wed, 2016-02-10 at 23:09 +0200, Dmitry Kasatkin wrote:
> > > On Wed, Feb 3, 2016 at 9:06 PM, Mimi Zohar <zohar@linux.vnet.ibm.com>
> wrote:

> > > >
> > > > -       if (read_id == READING_FIRMWARE)
> > > > +       switch (read_id) {
> > > > +       case READING_FIRMWARE:
> > > >                 func = FIRMWARE_CHECK;
> > > > -       else if (read_id == READING_MODULE)
> > > > +               break;
> > > > +       case READING_MODULE:
> > > >                 func = MODULE_CHECK;
> > > > +               break;
> > > > +       case READING_KEXEC_IMAGE:
> > > > +               func = KEXEC_CHECK;
> > > > +               break;
> > > > +       case READING_KEXEC_INITRAMFS:
> > > > +               func = INITRAMFS_CHECK;
> > > > +               break;
> > > > +       default:
> > > > +               func = FILE_CHECK;
> > > > +               break;
> > > > +       }
> > > >
> > >
> > > I would define a separate function like "int ima_read_id_to_func(id)"
> > > which search over the map
> > >
> > > Something like...
> > >
> > > struct
> > > {
> > >      int id;
> > >      int func;
> > > }  map[] = {
> > >   { .id = READING_FIRMWARE, .fun = FIRMWARE_CHECK },
> > >    ...
> > >   { -1, 0 }
> > > };
> > >
> >
> > So we stay with the duplication (option 1), but clean it up.  That works
> > for me.
> >
> 
> Actually it may be simpler.
> Just define int idmap[MAX_ID] and assign to every id corresponding func.
> It will be quick and simple.

Unlike the ima_read_id_to_func() above or the original switch/case
statement, this method assumes the kernel_read_file_id enumeration stays
in sync with ima_hooks.  In terms of the  ima_read_id_to_func()
function, it would iterate over the map[] to find the corresponding .id,
whereas the current switch/case is a direct lookup.

Perhaps we should defer making a change for now.
  
Mimi