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Date:	Tue, 22 Jul 2014 15:20:53 -0700
From:	Kees Cook <>
To:	"Luis R. Rodriguez" <>
Cc:	LKML <>,
	Ming Lei <>,
	Greg Kroah-Hartman <>,
	James Morris <>,
	David Howells <>,
	"" <>,
	linux-security-module <>,,
	linux-wireless <>
Subject: Re: [PATCH 3/7] security: introduce kernel_fw_from_file hook

On Tue, Jul 22, 2014 at 3:11 PM, Luis R. Rodriguez <> wrote:
> On Tue, Jul 22, 2014 at 1:55 PM, Kees Cook <> wrote:
>> On Tue, Jul 22, 2014 at 12:39 PM, Luis R. Rodriguez <> wrote:
>>> On Mon, Jul 14, 2014 at 3:31 PM, Kees Cook <> wrote:
>>>> Yup, with this and the module hook, adding a similar hook for kexec
>>>> makes sense as well. A paranoid kernel doesn't want to trust anything
>>>> it's loading from userspace. :)
>>> Well I'm actually wondering if we could generalize requiring hooks or
>>> not for LSM as part of the general kobject definition. Then we
>>> wouldn't need to keep growing hooks for modules, firmware, kexec
>>> images, etc, but instead using the interfaces for kobjects and who
>>> depend on them. How that would actually look -- I'm not sure, but just
>>> a thought.
>> Yeah, there does seem to be a repeated "get a thing from userspace"
>> method here, but the interfaces have been rather scattered so far. I
>> haven't seen an obvious way to consolidate them yet.
> If we are going to be adding a new system call for each type of
> userspace object to help LSMs with requirements I wonder if its a
> worthy endeavor to review. This series didn't add one but you had
> mentioned finit_module() for example, are we going to want one for
> finit_firmware() finit_kexec_image(), etc?

The kernel pulls in firmware directly from the filesystem, so no
syscall there. :) kexec just had kexec_load_file added as a syscall
(it takes 2 fds: kernel and initrd).


Kees Cook
Chrome OS Security
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