diff --git a/fs/exec.c b/fs/exec.c
index 40073142288f..1cb3bf323e0f 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -700,25 +700,14 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 	unsigned long length = old_end - old_start;
 	unsigned long new_start = old_start - shift;
 	unsigned long new_end = old_end - shift;
-	VMA_ITERATOR(vmi, mm, new_start);
+	VMA_ITERATOR(vmi, mm, 0);
 	struct vm_area_struct *next;
 	struct mmu_gather tlb;
+	int ret;
 
-	BUG_ON(new_start > new_end);
-
-	/*
-	 * ensure there are no vmas between where we want to go
-	 * and where we are
-	 */
-	if (vma != vma_next(&vmi))
-		return -EFAULT;
-
-	vma_iter_prev_range(&vmi);
-	/*
-	 * cover the whole range: [new_start, old_end)
-	 */
-	if (vma_expand(&vmi, vma, new_start, old_end, vma->vm_pgoff, NULL))
-		return -ENOMEM;
+	ret = vma_expand_bottom(&vmi, vma, shift, &next);
+	if (ret)
+		return ret;
 
 	/*
 	 * move the page tables downwards, on failure we rely on
@@ -730,7 +719,7 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 
 	lru_add_drain();
 	tlb_gather_mmu(&tlb, mm);
-	next = vma_next(&vmi);
+
 	if (new_end > old_start) {
 		/*
 		 * when the old and new regions overlap clear from new_end.
@@ -749,9 +738,8 @@ static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 	}
 	tlb_finish_mmu(&tlb);
 
-	vma_prev(&vmi);
 	/* Shrink the vma to just the new range */
-	return vma_shrink(&vmi, vma, new_start, new_end, vma->vm_pgoff);
+	return vma_shrink_top(&vmi, vma, shift);
 }
 
 /*
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 4d2b5538925b..e3220439cf75 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3273,11 +3273,10 @@ void anon_vma_interval_tree_verify(struct anon_vma_chain *node);
 
 /* mmap.c */
 extern int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin);
-extern int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
-		      unsigned long start, unsigned long end, pgoff_t pgoff,
-		      struct vm_area_struct *next);
-extern int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
-		       unsigned long start, unsigned long end, pgoff_t pgoff);
+extern int vma_expand_bottom(struct vma_iterator *vmi, struct vm_area_struct *vma,
+			     unsigned long shift, struct vm_area_struct **next);
+extern int vma_shrink_top(struct vma_iterator *vmi, struct vm_area_struct *vma,
+			  unsigned long shift);
 extern struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *);
 extern int insert_vm_struct(struct mm_struct *, struct vm_area_struct *);
 extern void unlink_file_vma(struct vm_area_struct *);
diff --git a/mm/internal.h b/mm/internal.h
index c8177200c943..f7779727bb78 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1305,6 +1305,12 @@ static inline struct vm_area_struct
 			  vma_policy(vma), new_ctx, anon_vma_name(vma));
 }
 
+int vma_expand(struct vma_iterator *vmi, struct vm_area_struct *vma,
+	       unsigned long start, unsigned long end, pgoff_t pgoff,
+		      struct vm_area_struct *next);
+int vma_shrink(struct vma_iterator *vmi, struct vm_area_struct *vma,
+	       unsigned long start, unsigned long end, pgoff_t pgoff);
+
 enum {
 	/* mark page accessed */
 	FOLL_TOUCH = 1 << 16,
diff --git a/mm/mmap.c b/mm/mmap.c
index e42d89f98071..574e69a04ebe 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -3940,6 +3940,71 @@ void mm_drop_all_locks(struct mm_struct *mm)
 	mutex_unlock(&mm_all_locks_mutex);
 }
 
+/*
+ * vma_expand_bottom() - Expands the bottom of a VMA downwards. An error will
+ *                       arise if there is another VMA in the expanded range, or
+ *                       if the expansion fails. This function leaves the VMA
+ *                       iterator, vmi, positioned at the newly expanded VMA.
+ * @vmi: The VMA iterator.
+ * @vma: The VMA to modify.
+ * @shift: The number of bytes by which to expand the bottom of the VMA.
+ * @next: Output parameter, pointing at the VMA immediately succeeding the newly
+ *        expanded VMA.
+ *
+ * Returns: 0 on success, an error code otherwise.
+ */
+int vma_expand_bottom(struct vma_iterator *vmi, struct vm_area_struct *vma,
+		      unsigned long shift, struct vm_area_struct **next)
+{
+	unsigned long old_start = vma->vm_start;
+	unsigned long old_end = vma->vm_end;
+	unsigned long new_start = old_start - shift;
+	unsigned long new_end = old_end - shift;
+
+	BUG_ON(new_start > new_end);
+
+	vma_iter_set(vmi, new_start);
+
+	/*
+	 * ensure there are no vmas between where we want to go
+	 * and where we are
+	 */
+	if (vma != vma_next(vmi))
+		return -EFAULT;
+
+	vma_iter_prev_range(vmi);
+
+	/*
+	 * cover the whole range: [new_start, old_end)
+	 */
+	if (vma_expand(vmi, vma, new_start, old_end, vma->vm_pgoff, NULL))
+		return -ENOMEM;
+
+	*next = vma_next(vmi);
+	vma_prev(vmi);
+
+	return 0;
+}
+
+/*
+ * vma_shrink_top() - Reduce an existing VMA's memory area by shift bytes from
+ *                    the top of the VMA.
+ * @vmi: The VMA iterator, must be positioned at the VMA.
+ * @vma: The VMA to modify.
+ * @shift: The number of bytes by which to shrink the VMA.
+ *
+ * Returns: 0 on success, an error code otherwise.
+ */
+int vma_shrink_top(struct vma_iterator *vmi, struct vm_area_struct *vma,
+		   unsigned long shift)
+{
+	if (shift >= vma->vm_end - vma->vm_start)
+		return -EINVAL;
+
+	return vma_shrink(vmi, vma, vma->vm_start, vma->vm_end - shift,
+			  vma->vm_pgoff);
+}
+
 /*
  * initialise the percpu counter for VM
  */
