Currently KASLR is enabled on three regions: the direct mapping of physical memory, vamlloc and vmemmap. However 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.
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 use 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. Cc: <[email protected]> #4.8+ Signed-off-by: Baoquan He <[email protected]> Acked-by: Dave Young <[email protected]> Reviewed-by: Bhupesh Sharma <[email protected]> Acked-by: Thomas Garnier <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: [email protected] Cc: [email protected] Cc: Thomas Garnier <[email protected]> Cc: Kees Cook <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Masahiro Yamada <[email protected]> Cc: Dave Young <[email protected]> Cc: Bhupesh Sharma <[email protected]> --- v1->v2: No code change, just update patch log according to reviewer's comment. arch/x86/mm/kaslr.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index 887e571..aed2064 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -48,7 +48,7 @@ static const unsigned long vaddr_start = __PAGE_OFFSET_BASE; #if defined(CONFIG_X86_ESPFIX64) static const unsigned long vaddr_end = ESPFIX_BASE_ADDR; #elif defined(CONFIG_EFI) -static const unsigned long vaddr_end = EFI_VA_START; +static const unsigned long vaddr_end = EFI_VA_END; #else static const unsigned long vaddr_end = __START_KERNEL_map; #endif @@ -105,7 +105,7 @@ void __init kernel_randomize_memory(void) */ BUILD_BUG_ON(vaddr_start >= vaddr_end); BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) && - vaddr_end >= EFI_VA_START); + vaddr_end >= EFI_VA_END); BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) || IS_ENABLED(CONFIG_EFI)) && vaddr_end >= __START_KERNEL_map); -- 2.5.5 -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
