linux-kernel - Re: [PATCH V3 08/11] kexec: Disable at runtime if the kernel enforces module loading restrictions

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Date:	Sun, 8 Sep 2013 16:24:47 +0000
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	Kees Cook <keescook@...omium.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>
Subject: Re: [PATCH V3 08/11] kexec: Disable at runtime if the kernel
 enforces module loading restrictions

On Sun, 2013-09-08 at 09:18 -0700, Greg KH wrote:

> I want both, but I don't need signed kexec support because I want to use
> kexec for a program that I "know" is correct because I validated the
> disk image it was on before I mounted it.  We already have other ways to
> "verify" things without having to add individual verification of
> specific pieces.

The kernel has no way to know that your kexec payload is coming from a
verified image. It'll just as happily take something from an unverified
image. If you've ensured that there's no way an attacker can call
kexec_load() on an unverified image, then you don't need signed modules.

-- 
Matthew Garrett <matthew.garrett@...ula.com>