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Commit 25dfe478 authored by Thomas Garnier's avatar Thomas Garnier Committed by Ingo Molnar
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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: default avatarThomas Garnier <thgarnie@google.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-hardening@lists.openwall.com
Link: http://lkml.kernel.org/r/1469635196-122447-1-git-send-email-thgarnie@google.com


[ Minor edits. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 404f6aac

arch/x86/include/asm/kaslr.h

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/include/asm/pgtable_64_types.h

+3 −1
Original line number Diff line number Diff line
@@ -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)

arch/x86/mm/kaslr.c

+24 −2
Original line number Diff line number Diff line
@@ -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;