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.
Unified · Split
| @@ -48,7 +48,7 @@ static const unsigned long vaddr_start = __PAGE_OFFSET_BASE; · 47 unmodified lines | |||
| 48 | #if defined(CONFIG_X86_ESPFIX64) | 48 | #if defined(CONFIG_X86_ESPFIX64) |
| 49 | static const unsigned long vaddr_end = ESPFIX_BASE_ADDR; | 49 | static const unsigned long vaddr_end = ESPFIX_BASE_ADDR; |
| 50 | #elif defined(CONFIG_EFI) | 50 | #elif defined(CONFIG_EFI) |
| 51 | static const unsigned long vaddr_end = EFI_VA_START; | 51 | static const unsigned long vaddr_end = EFI_VA_END; |
| 52 | #else | 52 | #else |
| 53 | static const unsigned long vaddr_end = __START_KERNEL_map; | 53 | static const unsigned long vaddr_end = __START_KERNEL_map; |
| 54 | #endif | 54 | #endif |
| @@ -105,7 +105,7 @@ void __init kernel_randomize_memory(void) · 50 unmodified lines | |||
| 105 | */ | 105 | */ |
| 106 | BUILD_BUG_ON(vaddr_start >= vaddr_end); | 106 | BUILD_BUG_ON(vaddr_start >= vaddr_end); |
| 107 | BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) && | 107 | BUILD_BUG_ON(IS_ENABLED(CONFIG_X86_ESPFIX64) && |
| 108 | vaddr_end >= EFI_VA_START); | 108 | vaddr_end >= EFI_VA_END); |
| 109 | BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) || | 109 | BUILD_BUG_ON((IS_ENABLED(CONFIG_X86_ESPFIX64) || |
| 110 | IS_ENABLED(CONFIG_EFI)) && | 110 | IS_ENABLED(CONFIG_EFI)) && |
| 111 | vaddr_end >= __START_KERNEL_map); | 111 | vaddr_end >= __START_KERNEL_map); |