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Message-ID: <CAJcbSZHZa0tk29i08xKwRuSA0hSQJ7ec3+-1W3zQ5pibC19v_Q@mail.gmail.com>
Date: Mon, 1 Aug 2016 10:09:59 -0700
From: Thomas Garnier <thgarnie@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
"H . Peter Anvin" <hpa@...or.com>, Thomas Garnier <thgarnie@...gle.com>, Kees Cook <keescook@...omium.org>
Cc: x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] x86/mm: Enable KASLR for vmemmap memory region (x86_64)
On Wed, Jul 27, 2016 at 8:59 AM, Thomas Garnier <thgarnie@...gle.com> wrote:
> 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 <thgarnie@...gle.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> Missing patch didn't pick-up by the tip bot on KASLR memory randomization.
> Resending after rebase on tip and tests as discussed with Ingo.
> Based on tip 4bcc8cf6ab5932cbb2511c8e18065e61b069f21c
Ingo: Any comment? Can you integrate it on tip?
> ---
> arch/x86/include/asm/kaslr.h | 1 +
> arch/x86/include/asm/pgtable_64_types.h | 4 +++-
> arch/x86/mm/kaslr.c | 24 +++++++++++++++++++++++-
> 3 files changed, 27 insertions(+), 2 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 26dccd6..3e9875f 100644
> --- a/arch/x86/mm/kaslr.c
> +++ b/arch/x86/mm/kaslr.c
> @@ -44,13 +44,22 @@
> * 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;
>
> --
> 2.8.0.rc3.226.g39d4020
>
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