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Message-ID: <CAGXu5j+zz1PyqRM4_Mz_UokD3Y6i6Vj7v_G8W-Ggd1XO_i0MsA@mail.gmail.com>
Date: Mon, 8 Apr 2013 15:55:10 -0700
From: Kees Cook <keescook@...omium.org>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Ingo Molnar <mingo@...hat.com>, LKML <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>, "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>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Dan Rosenberg <drosenberg@...curity.com>, Julien Tinnes <jln@...gle.com>,
Will Drewry <wad@...omium.org>, Eric Northup <digitaleric@...gle.com>
Subject: Re: [PATCH] x86: make IDT read-only
On Mon, Apr 8, 2013 at 3:47 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 04/08/2013 03:43 PM, Kees Cook wrote:
>> This makes the IDT unconditionally read-only. This primarily removes
>> the IDT from being a target for arbitrary memory write attacks. It has
>> an added benefit of also not leaking (via the "sidt" instruction) the
>> kernel base offset, if it has been relocated.
>>
>> Signed-off-by: Kees Cook <keescook@...omium.org>
>> Cc: Eric Northup <digitaleric@...gle.com>
>
> This isn't quite what this patch does, though, right? There is still a
> writable IDT mapping at all times, which is different from a true
> readonly IDT, no?
Ah, I guess that's true. I suppose I should say it makes the memory
seen at the "sidt" location read-only. Can we make them both
read-only?
-Kees
--
Kees Cook
Chrome OS Security
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