Commit-ID: 25dfe4785332723f09311dcb7fd91015a60c022f Gitweb: http://git.kernel.org/tip/25dfe4785332723f09311dcb7fd91015a60c022f Author: Thomas Garnier <thgar...@google.com> AuthorDate: Wed, 27 Jul 2016 08:59:56 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Wed, 10 Aug 2016 16:10:06 +0200
x86/mm/64: Enable KASLR for vmemmap memory region Add vmemmap in the list of randomized memory regions. The vmemmap region holds a representation of the physical memory (through a struct page array). An attacker could use this region to disclose the kernel memory layout (walking the page linked list). Signed-off-by: Thomas Garnier <thgar...@google.com> Signed-off-by: Kees Cook <keesc...@chromium.org> Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: kernel-harden...@lists.openwall.com Link: http://lkml.kernel.org/r/1469635196-122447-1-git-send-email-thgar...@google.com [ Minor edits. ] Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/include/asm/kaslr.h | 1 + arch/x86/include/asm/pgtable_64_types.h | 4 +++- arch/x86/mm/kaslr.c | 26 ++++++++++++++++++++++++-- 3 files changed, 28 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/kaslr.h b/arch/x86/include/asm/kaslr.h index 2674ee3..1052a79 100644 --- a/arch/x86/include/asm/kaslr.h +++ b/arch/x86/include/asm/kaslr.h @@ -6,6 +6,7 @@ unsigned long kaslr_get_random_long(const char *purpose); #ifdef CONFIG_RANDOMIZE_MEMORY extern unsigned long page_offset_base; extern unsigned long vmalloc_base; +extern unsigned long vmemmap_base; void kernel_randomize_memory(void); #else diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h index 6fdef9e..3a26420 100644 --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -57,11 +57,13 @@ typedef struct { pteval_t pte; } pte_t; #define MAXMEM _AC(__AC(1, UL) << MAX_PHYSMEM_BITS, UL) #define VMALLOC_SIZE_TB _AC(32, UL) #define __VMALLOC_BASE _AC(0xffffc90000000000, UL) -#define VMEMMAP_START _AC(0xffffea0000000000, UL) +#define __VMEMMAP_BASE _AC(0xffffea0000000000, UL) #ifdef CONFIG_RANDOMIZE_MEMORY #define VMALLOC_START vmalloc_base +#define VMEMMAP_START vmemmap_base #else #define VMALLOC_START __VMALLOC_BASE +#define VMEMMAP_START __VMEMMAP_BASE #endif /* CONFIG_RANDOMIZE_MEMORY */ #define VMALLOC_END (VMALLOC_START + _AC((VMALLOC_SIZE_TB << 40) - 1, UL)) #define MODULES_VADDR (__START_KERNEL_map + KERNEL_IMAGE_SIZE) diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c index ec8654f..aec03aa 100644 --- a/arch/x86/mm/kaslr.c +++ b/arch/x86/mm/kaslr.c @@ -40,17 +40,26 @@ * You need to add an if/def entry if you introduce a new memory region * compatible with KASLR. Your entry must be in logical order with memory * layout. For example, ESPFIX is before EFI because its virtual address is - * before. You also need to add a BUILD_BUG_ON in kernel_randomize_memory to + * before. You also need to add a BUILD_BUG_ON() in kernel_randomize_memory() to * ensure that this order is correct and won't be changed. */ static const unsigned long vaddr_start = __PAGE_OFFSET_BASE; -static const unsigned long vaddr_end = VMEMMAP_START; + +#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; +#else +static const unsigned long vaddr_end = __START_KERNEL_map; +#endif /* Default values */ unsigned long page_offset_base = __PAGE_OFFSET_BASE; EXPORT_SYMBOL(page_offset_base); unsigned long vmalloc_base = __VMALLOC_BASE; EXPORT_SYMBOL(vmalloc_base); +unsigned long vmemmap_base = __VMEMMAP_BASE; +EXPORT_SYMBOL(vmemmap_base); /* * Memory regions randomized by KASLR (except modules that use a separate logic @@ -63,6 +72,7 @@ static __initdata struct kaslr_memory_region { } kaslr_regions[] = { { &page_offset_base, 64/* Maximum */ }, { &vmalloc_base, VMALLOC_SIZE_TB }, + { &vmemmap_base, 1 }, }; /* Get size in bytes used by the memory region */ @@ -89,6 +99,18 @@ void __init kernel_randomize_memory(void) struct rnd_state rand_state; unsigned long remain_entropy; + /* + * All these BUILD_BUG_ON checks ensures the memory layout is + * consistent with the vaddr_start/vaddr_end variables. + */ + BUILD_BUG_ON(vaddr_start >= vaddr_end); + BUILD_BUG_ON(config_enabled(CONFIG_X86_ESPFIX64) && + vaddr_end >= EFI_VA_START); + BUILD_BUG_ON((config_enabled(CONFIG_X86_ESPFIX64) || + config_enabled(CONFIG_EFI)) && + vaddr_end >= __START_KERNEL_map); + BUILD_BUG_ON(vaddr_end > __START_KERNEL_map); + if (!kaslr_memory_enabled()) return;
