On 24 March 2017 at 09:24, Ingo Molnar <mi...@kernel.org> wrote: > > * Dave Young <dyo...@redhat.com> wrote: > >> > > So I applied this kexec fix and extended the changelog to clearly show >> > > why >> > > this fix matters in practice. >> > >> > I thought it only impacts kexec, but Dave thought it will impact 1st kenrel >> > either. >> >> Yes, I think no need to mention kexec, it is a general issue. >> >> First, the space is reserved for EFI, so kernel should not use it for kaslr. > > It's the kernel's EFI code, and we map whatever address we want (and then pass > that to the EFI runtime), so wether it's randomized or not is the Linux > kernel's > policy decision... >
No. It is the firmware's EFI code, and the virtual translation applied by the OS is made known to the firmware by means of a call into the runtime service SetVirtualAddressMap(). This service can only be called once after each boot, and so kexec kernels are forced to use the same VA mapping for runtime services as the first kernel. This is the whole point of having a VA region reserved for this, so that kexec kernels are guaranteed to be able to use the same VA mapping. > So that's my question: can these memory regions include security sensitive > data, > and if yes, how can we best randomize it while kexec and other kernel and EFI > features still work? > > Preserving virtual addresses for kexec is a red herring: the randomized offset > could be passed to the kexec-ed kernel just fine. > > Thanks, > > Ingo > -- > To unsubscribe from this list: send the line "unsubscribe linux-efi" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
