[PATCH] x86/mm: Enable KASLR for vmemmap memory region (x86_64)

[PATCH] x86/mm: Enable KASLR for vmemmap memory region (x86_64)

[Thomas Garnier]

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@google.com>
Signed-off-by: Kees Cook <keescook@chromium.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
---
 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

Re: [PATCH] x86/mm: Enable KASLR for vmemmap memory region (x86_64)

[Thomas Garnier]

On Wed, Jul 27, 2016 at 8:59 AM, Thomas Garnier <thgarnie@google.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@google.com>
> Signed-off-by: Kees Cook <keescook@chromium.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
>

Re: [PATCH] x86/mm: Enable KASLR for vmemmap memory region (x86_64)

[Ingo Molnar]

* Thomas Garnier <thgarnie@google.com> wrote:

> On Wed, Jul 27, 2016 at 8:59 AM, Thomas Garnier <thgarnie@google.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@google.com>
> > Signed-off-by: Kees Cook <keescook@chromium.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(-)

After the merge window is over. There's no bad effect from the lack of this patch, 
other than lower level of randomization of kernel virtual addresses, right?

Thanks,

	Ingo

Re: [PATCH] x86/mm: Enable KASLR for vmemmap memory region (x86_64)

[Thomas Garnier]

On Tue, Aug 2, 2016 at 1:14 AM, Ingo Molnar <mingo@kernel.org> wrote:
>
> * Thomas Garnier <thgarnie@google.com> wrote:
>
>> On Wed, Jul 27, 2016 at 8:59 AM, Thomas Garnier <thgarnie@google.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@google.com>
>> > Signed-off-by: Kees Cook <keescook@chromium.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(-)
>
> After the merge window is over. There's no bad effect from the lack of this patch,
> other than lower level of randomization of kernel virtual addresses, right?
>

That's right, this change just enables randomization for vmemmap.

> Thanks,
>
>         Ingo

[tip:x86/mm] x86/mm/64: Enable KASLR for vmemmap memory region

[tip-bot for Thomas Garnier]

Commit-ID:  25dfe4785332723f09311dcb7fd91015a60c022f
Gitweb:     http://git.kernel.org/tip/25dfe4785332723f09311dcb7fd91015a60c022f
Author:     Thomas Garnier <thgarnie@google.com>
AuthorDate: Wed, 27 Jul 2016 08:59:56 -0700
Committer:  Ingo Molnar <mingo@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 <thgarnie@google.com>
Signed-off-by: Kees 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: Ingo Molnar <mingo@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;