Date: Mon, 8 May 2017 07:09:45 -0700 From: Thomas Garnier <thgarnie@...gle.com> To: Daniel Gruss <daniel.gruss@...k.tugraz.at> Cc: David Gens <david.gens@...tu-darmstadt.de>, kernel list <linux-kernel@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, clementine.maurice@...k.tugraz.at, moritz.lipp@...k.tugraz.at, Michael Schwarz <michael.schwarz@...k.tugraz.at>, Richard Fellner <richard.fellner@...dent.tugraz.at>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Ingo Molnar <mingo@...nel.org>, anders.fogh@...ta-adan.de Subject: Re: [RFC, PATCH] x86_64: KAISER - do not map kernel in user mode On Mon, May 8, 2017 at 6:53 AM, Daniel Gruss <daniel.gruss@...k.tugraz.at> wrote: > On 06.05.2017 10:38, Daniel Gruss wrote: >> >> On 2017-05-06 06:02, David Gens wrote: >>> >>> Assuming that their patch indeed leaks per-cpu addresses.. it might not >>> necessarily >>> be required to change it. >> >> >> I think we're not leaking them (unless we still have some bug in our >> code). > > > Just to correct my answer here as well: Although we experimented with fixed > mappings for per-cpu addresses, the current patch does not incorporate this > yet, so it indeed still leaks. However, it is not a severe problem. The > mapping of the required (per-cpu) variables would be at a fixed location in > the user CR3, instead of the ones that are used in the kernel. Why do you think it should be at a fixed location in the user CR3? I see that you just mirror the entries. You also mirror __entry_text_start / __entry_text_end which is part of the binary so will leak the base address of the kernel. Maybe I am missing something. -- Thomas
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