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Date: Wed, 10 Apr 2013 11:41:35 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Kees Cook <keescook@chromium.org>
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Subject: Re: [kernel-hardening] Re: [PATCH] x86: make IDT read-only
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* Kees Cook <keescook@chromium.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