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>

1 files changed, 6 insertions, 1 deletions

diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
index 566d0d71a1e7..1e6c33d01c05 100644
--- 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;
 }