ARM: make vectors page inaccessible from userspace

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>

diff --git a/arch/arm/include/asm/page.h b/arch/arm/include/asm/page.h
index 6363f3d1d505292c57a26fbd3585b3f147738771..4355f0ec44d62e9b5d7c40132f28f0ff6710f387 100644 (file)
--- a/arch/arm/include/asm/page.h
+++ b/arch/arm/include/asm/page.h
@@ -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>

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 566d0d71a1e7e2c0cdd1716f097de8a1fdf582ef..1e6c33d01c057fc95a8b6f3e14a44c7b7d6e8233 100644 (file)
--- a/arch/arm/kernel/process.c
+++ b/arch/arm/kernel/process.c
@@ -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
@@ -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;
 }

diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
index 9ea274d1af69e03e185be972329bd419eeadb781..ca46f413d867e9b90b18ef85001be758023211f5 100644 (file)
--- a/arch/arm/mm/mmu.c
+++ b/arch/arm/mm/mmu.c
@@ -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()) {