linux-kernel - Re: [kernel-hardening] Re: [PATCH] x86: make IDT read-only

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Message-ID: <CAGXu5j+_sSVsB-D+zYyzBkj0HKzyVfJOBRAxMRmge2t=sSrTAg@mail.gmail.com>
Date:	Tue, 9 Apr 2013 11:53:02 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Ingo Molnar <mingo@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"x86@...nel.org" <x86@...nel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Alex Shi <alex.shi@...el.com>,
	Borislav Petkov <borislav.petkov@....com>,
	Alexander Duyck <alexander.h.duyck@...el.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>,
	Dan Rosenberg <drosenberg@...curity.com>,
	Julien Tinnes <jln@...gle.com>, Will Drewry <wad@...omium.org>,
	Eric Northup <digitaleric@...gle.com>
Subject: Re: [kernel-hardening] Re: [PATCH] x86: make IDT read-only

On Tue, Apr 9, 2013 at 11:50 AM, H. Peter Anvin <hpa@...or.com> wrote:
> On 04/09/2013 11:46 AM, Kees Cook wrote:
>>
>> Ah-ha! Yes, I see now when comparing the debug/kernel_page_tables
>> reports. It's just the High Kernel Mapping that we care about.
>> Addresses outside that range are less of a leak. Excellent, then GDT
>> may not be a problem. Whew.
>>
>
> It does beg the question if we need to randomize kmalloc... which could
> have issues by itself.

Agreed, but this should be a separate issue. As is the fact that GDT
is writable and a discoverable target.

-Kees

--
Kees Cook
Chrome OS Security
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