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ARM: make vectors page inaccessible from userspace
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If kuser helpers are not provided by the kernel, disable user access to
the vectors page.  With the kuser helpers gone, there is no reason for
this page to be visible to userspace.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
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Russell King committed Aug 1, 2013
1 parent 48be69a commit a5463cd
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Showing 3 changed files with 12 additions and 1 deletion.
2 changes: 2 additions & 0 deletions arch/arm/include/asm/page.h
Original file line number Diff line number Diff line change
Expand Up @@ -142,7 +142,9 @@ extern void __cpu_copy_user_highpage(struct page *to, struct page *from,
#define clear_page(page) memset((void *)(page), 0, PAGE_SIZE)
extern void copy_page(void *to, const void *from);

#ifdef CONFIG_KUSER_HELPERS
#define __HAVE_ARCH_GATE_AREA 1
#endif

#ifdef CONFIG_ARM_LPAE
#include <asm/pgtable-3level-types.h>
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7 changes: 6 additions & 1 deletion arch/arm/kernel/process.c
Original file line number Diff line number Diff line change
Expand Up @@ -426,6 +426,7 @@ unsigned long arch_randomize_brk(struct mm_struct *mm)
}

#ifdef CONFIG_MMU
#ifdef CONFIG_KUSER_HELPERS
/*
* The vectors page is always readable from user space for the
* atomic helpers. Insert it into the gate_vma so that it is visible
Expand Down Expand Up @@ -458,10 +459,14 @@ int in_gate_area_no_mm(unsigned long addr)
{
return in_gate_area(NULL, addr);
}
#define is_gate_vma(vma) ((vma) = &gate_vma)
#else
#define is_gate_vma(vma) 0
#endif

const char *arch_vma_name(struct vm_area_struct *vma)
{
return (vma == &gate_vma) ? "[vectors]" :
return is_gate_vma(vma) ? "[vectors]" :
(vma->vm_mm && vma->vm_start == vma->vm_mm->context.sigpage) ?
"[sigpage]" : NULL;
}
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4 changes: 4 additions & 0 deletions arch/arm/mm/mmu.c
Original file line number Diff line number Diff line change
Expand Up @@ -1205,7 +1205,11 @@ static void __init devicemaps_init(struct machine_desc *mdesc)
map.pfn = __phys_to_pfn(virt_to_phys(vectors));
map.virtual = 0xffff0000;
map.length = PAGE_SIZE;
#ifdef CONFIG_KUSER_HELPERS
map.type = MT_HIGH_VECTORS;
#else
map.type = MT_LOW_VECTORS;
#endif
create_mapping(&map);

if (!vectors_high()) {
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