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Date: Fri, 05 Apr 2013 15:08:32 -0700
From: "H. Peter Anvin" <>
To: Julien Tinnes <>
CC: Ingo Molnar <>, Kees Cook <>,
        LKML <>,
        "" <>,
        Thomas Gleixner <>, Ingo Molnar <>,
        "" <>,
        Jarkko Sakkinen <>,
        Matthew Garrett <>,
        Matt Fleming <>,
        Eric Northup <>,
        Dan Rosenberg <>,
        Will Drewry <>
Subject: Re: [PATCH 3/3] x86: kernel base offset ASLR

On 04/05/2013 03:06 PM, Julien Tinnes wrote:
> Speaking of IDT, and to capture some off-thread discussion here, we
> should remember that the "SGDT" and "SIDT" instructions aren't
> privileged on x86, so user-land can leak these out without any way for
> the kernel to intercept that.
> Adding their own random offsets to these two tables would be very
> useful. This could be done in a later patchset of course.

Yes, if the GDT or IDT position is at all correlated to the kernel
position this is pointless.


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