[PATCH] x86, mm: get ASLR work for hugetlb mappings

From: Kirill A. Shutemov
Date: Tue Oct 22 2013 - 09:52:41 EST


Matthew noticed that hugetlb doesn't participate in ASLR on x86-64.
The reason is genereic hugetlb_get_unmapped_area() which is used on
x86-64. It doesn't support randomization and use bottom-up unmapped area
lookup, instead of usual top-down on x86-64.

x86 has arch-specific hugetlb_get_unmapped_area(), but it's used only on
x86-32.

Let's use arch-specific hugetlb_get_unmapped_area() on x86-64 too.
It fixes the issue and make hugetlb use top-down unmapped area lookup.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
---
arch/x86/include/asm/page.h | 1 +
arch/x86/include/asm/page_32.h | 4 ----
arch/x86/mm/hugetlbpage.c | 9 +++------
3 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/page.h b/arch/x86/include/asm/page.h
index c87892442e..775873d3be 100644
--- a/arch/x86/include/asm/page.h
+++ b/arch/x86/include/asm/page.h
@@ -71,6 +71,7 @@ extern bool __virt_addr_valid(unsigned long kaddr);
#include <asm-generic/getorder.h>

#define __HAVE_ARCH_GATE_AREA 1
+#define HAVE_ARCH_HUGETLB_UNMAPPED_AREA

#endif /* __KERNEL__ */
#endif /* _ASM_X86_PAGE_H */
diff --git a/arch/x86/include/asm/page_32.h b/arch/x86/include/asm/page_32.h
index 4d550d04b6..904f528cc8 100644
--- a/arch/x86/include/asm/page_32.h
+++ b/arch/x86/include/asm/page_32.h
@@ -5,10 +5,6 @@

#ifndef __ASSEMBLY__

-#ifdef CONFIG_HUGETLB_PAGE
-#define HAVE_ARCH_HUGETLB_UNMAPPED_AREA
-#endif
-
#define __phys_addr_nodebug(x) ((x) - PAGE_OFFSET)
#ifdef CONFIG_DEBUG_VIRTUAL
extern unsigned long __phys_addr(unsigned long);
diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c
index 9d980d88b7..8c9f647ff9 100644
--- a/arch/x86/mm/hugetlbpage.c
+++ b/arch/x86/mm/hugetlbpage.c
@@ -87,9 +87,7 @@ int pmd_huge_support(void)
}
#endif

-/* x86_64 also uses this file */
-
-#ifdef HAVE_ARCH_HUGETLB_UNMAPPED_AREA
+#ifdef CONFIG_HUGETLB_PAGE
static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
@@ -99,7 +97,7 @@ static unsigned long hugetlb_get_unmapped_area_bottomup(struct file *file,

info.flags = 0;
info.length = len;
- info.low_limit = TASK_UNMAPPED_BASE;
+ info.low_limit = current->mm->mmap_legacy_base;
info.high_limit = TASK_SIZE;
info.align_mask = PAGE_MASK & ~huge_page_mask(h);
info.align_offset = 0;
@@ -172,8 +170,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
return hugetlb_get_unmapped_area_topdown(file, addr, len,
pgoff, flags);
}
-
-#endif /*HAVE_ARCH_HUGETLB_UNMAPPED_AREA*/
+#endif /* CONFIG_HUGETLB_PAGE */

#ifdef CONFIG_X86_64
static __init int setup_hugepagesz(char *opt)
--
1.8.4.rc3

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