On Thu, May 4, 2017 at 3:02 AM, Daniel Gruss <daniel.gr...@iaik.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 [4] (the corresponding > paper [5] 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) > > [1] http://www.ieee-security.org/TC/SP2013/papers/4977a191.pdf > [2] > 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 > [3] > https://www.blackhat.com/docs/us-16/materials/us-16-Jang-Breaking-Kernel-Address-Space-Layout-Randomization-KASLR-With-Intel-TSX.pdf > [4] https://github.com/IAIK/KAISER > [5] https://gruss.cc/files/kaiser.pdf > >
Please read the documentation on submitting patches [1] and coding style [2]. 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? [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/submitting-patches.rst [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst Thanks, -- Thomas