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Date: Tue, 21 Jun 2016 17:47:05 -0700
From: Kees Cook <keescook@...omium.org>
To: Ingo Molnar <mingo@...nel.org>
Cc: Kees Cook <keescook@...omium.org>,
Thomas Garnier <thgarnie@...gle.com>,
Andy Lutomirski <luto@...nel.org>,
x86@...nel.org,
Borislav Petkov <bp@...e.de>,
Baoquan He <bhe@...hat.com>,
Yinghai Lu <yinghai@...nel.org>,
Juergen Gross <jgross@...e.com>,
Matt Fleming <matt@...eblueprint.co.uk>,
Toshi Kani <toshi.kani@....com>,
Andrew Morton <akpm@...ux-foundation.org>,
Dan Williams <dan.j.williams@...el.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Xiao Guangrong <guangrong.xiao@...ux.intel.com>,
Martin Schwidefsky <schwidefsky@...ibm.com>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Alexander Kuleshov <kuleshovmail@...il.com>,
Alexander Popov <alpopov@...ecurity.com>,
Dave Young <dyoung@...hat.com>,
Joerg Roedel <jroedel@...e.de>,
Lv Zheng <lv.zheng@...el.com>,
Mark Salter <msalter@...hat.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
Stephen Smalley <sds@...ho.nsa.gov>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Jan Beulich <JBeulich@...e.com>,
linux-kernel@...r.kernel.org,
Jonathan Corbet <corbet@....net>,
linux-doc@...r.kernel.org,
kernel-hardening@...ts.openwall.com
Subject: [PATCH v7 8/9] x86/mm: Enable KASLR for vmemmap memory region (x86_64)
From: Thomas Garnier <thgarnie@...gle.com>
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>
---
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 2674ee3de748..1052a797d71d 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 6fdef9eef2d5..3a264200c62f 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 c939cfe1b516..4f91dc273062 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;
--
2.7.4
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