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Date: Tue, 19 Nov 2013 15:17:50 +0200 (EET) From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> To: Ingo Molnar <mingo@...nel.org> Cc: akpm@...ux-foundation.org, mingo@...e.hu, hpa@...or.com, tglx@...utronix.de, kirill.shutemov@...ux.intel.com, dave.hansen@...el.com, mingo@...hat.com, n-horiguchi@...jp.nec.com, willy@...ux.intel.com, linux-kernel@...r.kernel.org Subject: Re: [patch 3/3] x86, mm: get ASLR work for hugetlb mappings Ingo Molnar wrote: > > * akpm@...ux-foundation.org <akpm@...ux-foundation.org> wrote: > > > From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> > > Subject: x86, mm: get ASLR work for hugetlb mappings > > > > 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. > > So the title and the changelog has typos (I counted three), which > makes me wonder how well this was tested. > > To show/document the testing effort a before/after /proc/PID/maps > output showing hugetlb vma addresses would be nice, showing that ASLR > didn't work before and that it works adequately after the patch. > > A word about the range and granularity of randomization in the typical > case would be nice as well. What about this: >From 440f2cd4a7e6918b9238680e4eacd75dc30291b6 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com> Date: Fri, 15 Nov 2013 14:14:05 -0800 Subject: [PATCH] x86, mm: get ASLR works for hugetlb mappings Matthew noticed that hugetlb doesn't participate in ASLR on x86-64. % for i in `seq 3`; do > tools/testing/selftests/vm/map_hugetlb | grep address > done Returned address is 0x2aaaaac00000 Returned address is 0x2aaaaac00000 Returned address is 0x2aaaaac00000 /proc/PID/maps entries for the mapping are always the same (except inode number): 2aaaaac00000-2aaabac00000 rw-p 00000000 00:0c 8200 /anon_hugepage (deleted) 2aaaaac00000-2aaabac00000 rw-p 00000000 00:0c 256 /anon_hugepage (deleted) 2aaaaac00000-2aaabac00000 rw-p 00000000 00:0c 7180 /anon_hugepage (deleted) The reason is generic 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 switch hugetlb to use top-down unmapped area lookup. % for i in `seq 3`; do > tools/testing/selftests/vm/map_hugetlb | grep address > done Returned address is 0x7f4f08a00000 Returned address is 0x7fdda4200000 Returned address is 0x7febe0000000 /proc/PID/maps entries: 7f4f08a00000-7f4f18a00000 rw-p 00000000 00:0c 1168 /anon_hugepage (deleted) 7fdda4200000-7fddb4200000 rw-p 00000000 00:0c 7092 /anon_hugepage (deleted) 7febe0000000-7febf0000000 rw-p 00000000 00:0c 7183 /anon_hugepage (deleted) Unmapped area lookup policy for hugetlb mappings is consistent with normal mappings now -- the only difference is alignment requirements for huge pages. libhugetlbfs test-suite didn't detect any regressions with the patch applied (although it shows few failures on my machine regardless the patch). Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com> Cc: Matthew Wilcox <willy@...ux.intel.com> Cc: Dave Hansen <dave.hansen@...el.com> Cc: Thomas Gleixner <tglx@...utronix.de> Cc: Ingo Molnar <mingo@...hat.com> Cc: "H. Peter Anvin" <hpa@...or.com> Cc: Naoya Horiguchi <n-horiguchi@...jp.nec.com> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org> --- 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 c87892442e53..775873d3be55 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 4d550d04b609..904f528cc8e8 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 9d980d88b747..8c9f647ff9e1 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) -- Kirill A. Shutemov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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