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

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Date:	Sun, 08 Sep 2013 10:32:56 -0700
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Matthew Garrett <matthew.garrett@...ula.com>
Cc:	Kees Cook <keescook@...omium.org>,
	Greg KH <gregkh@...uxfoundation.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 17:27 +0000, Matthew Garrett wrote:
> > It's an argument that CAP_SYS_BOOT is too powerful yes, but if you
> > recall, I said I keep that one.  In the rather lame analogy, what I do
> > by giving away CAP_SYS_MODULE and enforcing module signing while keeping
> > CAP_SYS_BOOT is allow people into my conservatory to play with the
> > plants but not into my house to steal the silver ... saying CAP_SYS_BOOT
> > is too powerful doesn't affect that use case because I haven't given
> > away CAP_SYS_BOOT.
> 
> Ok, sorry, I had your meaning inverted. Yes, permitting the loading of
> signed modules while preventing the use of kexec is a completely
> reasonable configuration - so reasonable that it's what this patch
> causes the kernel to do automatically. 

Well, no, it doesn't because with this patch, *I* can't use kexec ...
you've just locked me out of my own house.

James


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