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

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Message-ID: <1378651204.2300.7.camel@x230>
Date:	Sun, 8 Sep 2013 14:40:04 +0000
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"keescook@...omium.org" <keescook@...omium.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 00:24 -0700, Greg KH wrote:
> On Sun, Sep 08, 2013 at 06:44:08AM +0000, Matthew Garrett wrote:

> > At the most trivial level, grab the address of sig_enforce from
> > kallsyms, jump to a kernel that doesn't enforce STRICT_DEVMEM, modify
> > sig_enforce, jump back to the old kernel.
> 
> Which proves what?

sig_enforce can be set, but once it's set can't be unset. Why do you
think that is?

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