Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull core fixes from Ingo Molnar:
 "This fixes a particularly thorny munmap() bug with MPX, plus fixes a
  host build environment assumption in objtool"

* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Allow AR to be overridden with HOSTAR
  x86/mpx, mm/core: Fix recursive munmap() corruption

arch/x86/mm/mpx.c

@@ -881,9 +881,10 @@ static int mpx_unmap_tables(struct mm_struct *mm,
  * the virtual address region start...end have already been split if
  * necessary, and the 'vma' is the first vma in this range (start -> end).
  */
-void mpx_notify_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
-		unsigned long start, unsigned long end)
+void mpx_notify_unmap(struct mm_struct *mm, unsigned long start,
+		      unsigned long end)
 {
+	struct vm_area_struct *vma;
 	int ret;
 
 	/*
@@ -902,11 +903,12 @@ void mpx_notify_unmap(struct mm_struct *mm, struct vm_area_struct *vma,
 	 * which should not occur normally. Being strict about it here
 	 * helps ensure that we do not have an exploitable stack overflow.
 	 */
-	do {
+	vma = find_vma(mm, start);
+	while (vma && vma->vm_start < end) {
 		if (vma->vm_flags & VM_MPX)
 			return;
 		vma = vma->vm_next;
-	} while (vma && vma->vm_start < end);
+	}
 
 	ret = mpx_unmap_tables(mm, start, end);
 	if (ret)