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Message-ID: <20130410094135.GD24443@gmail.com>
Date: Wed, 10 Apr 2013 11:41:35 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Kees Cook <keescook@...omium.org>
Cc: "H. Peter Anvin" <hpa@...or.com>,
"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: Re: [PATCH] x86: make IDT read-only
* Kees Cook <keescook@...omium.org> wrote:
> > That's the area in which we just map 1:1 to memory. Anything allocated with
> > e.g. kmalloc() ends up with those addresses.
>
> 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's still an infoleak to worry about: any function pointers nearby matter, and
the x86 GDT is obviously full of useful and highly privilege-relevant function
pointers ...
I have no objections against read-only mapping the GDT as well.
Thanks,
Ingo
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