Date: Thu, 4 May 2017 08:28:52 -0700 From: Thomas Garnier <thgarnie@...gle.com> To: Daniel Gruss <daniel.gruss@...k.tugraz.at> Cc: kernel list <linux-kernel@...r.kernel.org>, Kernel Hardening <kernel-hardening@...ts.openwall.com>, "clementine.maurice@...k.tugraz.at" <clementine.maurice@...k.tugraz.at>, "moritz.lipp@...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" <anders.fogh@...ta-adan.de> Subject: Re: [RFC, PATCH] x86_64: KAISER - do not map kernel in user mode On Thu, May 4, 2017 at 3:02 AM, Daniel Gruss <daniel.gruss@...k.tugraz.at> wrote: > After several recent works [1,2,3] KASLR on x86_64 was basically considered > dead by many researchers. We have been working on an efficient but effective > fix for this problem and found that not mapping the kernel space when > running in user mode is the solution to this problem  (the corresponding > paper  will be presented at ESSoS17). > > With this RFC patch we allow anybody to configure their kernel with the flag > CONFIG_KAISER to add our defense mechanism. > > If there are any questions we would love to answer them. > We also appreciate any comments! > > Cheers, > Daniel (+ the KAISER team from Graz University of Technology) > >  http://www.ieee-security.org/TC/SP2013/papers/4977a191.pdf >  > https://www.blackhat.com/docs/us-16/materials/us-16-Fogh-Using-Undocumented-CPU-Behaviour-To-See-Into-Kernel-Mode-And-Break-KASLR-In-The-Process.pdf >  > https://www.blackhat.com/docs/us-16/materials/us-16-Jang-Breaking-Kernel-Address-Space-Layout-Randomization-KASLR-With-Intel-TSX.pdf >  https://github.com/IAIK/KAISER >  https://gruss.cc/files/kaiser.pdf > > Please read the documentation on submitting patches  and coding style . I have two questions: - How this approach prevent the hardware attacks you mentioned? You still have to keep a part of _text in the pagetable and an attacker could discover it no? (and deduce the kernel base address). You also need to make it clear that btb attacks are still possible. - What is the perf impact?  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst  https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst Thanks, -- Thomas
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