Messages in this thread | | | Subject | Re: [RFC] x86/mm/KASLR: Remap GDTs at fixed location | From | Arjan van de Ven <> | Date | Thu, 5 Jan 2017 07:08:05 -0800 |
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On 1/5/2017 12:11 AM, Ingo Molnar wrote: > > * Thomas Garnier <thgarnie@google.com> wrote: > >> Each processor holds a GDT in its per-cpu structure. The sgdt >> instruction gives the base address of the current GDT. This address can >> be used to bypass KASLR memory randomization. With another bug, an >> attacker could target other per-cpu structures or deduce the base of the >> main memory section (PAGE_OFFSET). >> >> In this change, a space is reserved at the end of the memory range >> available for KASLR memory randomization. The space is big enough to hold >> the maximum number of CPUs (as defined by setup_max_cpus). Each GDT is >> mapped at specific offset based on the target CPU. Note that if there is >> not enough space available, the GDTs are not remapped. >> >> The document was changed to mention GDT remapping for KASLR. This patch >> also include dump page tables support. >> >> This patch was tested on multiple hardware configurations and for >> hibernation support. > >> void kernel_randomize_memory(void); >> +void kernel_randomize_smp(void); >> +void* kaslr_get_gdt_remap(int cpu); > > Yeah, no fundamental objections from me to the principle, but I get some bad vibes > from the naming here: seeing that kernel_randomize_smp() actually makes things > less random. >
kernel_unrandomize_smp() ...
one request.. can we make sure this unrandomization is optional?
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