Greg Kroah-Hartman of the Linux Foundation submitted version 4.10 of a 81-part(!) patch to the Linux kernel by Baoquan He of Red Hat.
[PATCH 4.10 65/81] x86/mm/KASLR: Exclude EFI region from KASLR VA space randomization
4.10-stable review patch. If anyone has any objections, please let me know.
commit a46f60d76004965e5669dbf3fc21ef3bc3632eb4 upstream.
Currently KASLR is enabled on three regions: the direct mapping of physical memory, vamlloc and vmemmap. However the EFI region is also mistakenly included for VA space randomization because of misusing EFI_VA_START macro and assuming EFI_VA_START < EFI_VA_END. (This breaks kexec and possibly other things that rely on stable addresses.) The EFI region is reserved for EFI runtime services virtual mapping which should not be included in KASLR ranges. In Documentation/x86/x86_64/mm.txt, we can see:
ffffffef00000000 – fffffffeffffffff (=64 GB) EFI region mapping space
EFI uses the space from -4G to -64G thus EFI_VA_START > EFI_VA_END, Here EFI_VA_START = -4G, and EFI_VA_END = -64G. Changing EFI_VA_START to EFI_VA_END in mm/kaslr.c fixes this problem.
More info: see the linux-efi/linux-kernel list.