diff --git a/gcc/c-family/c-ubsan.cc b/gcc/c-family/c-ubsan.cc
index 940982819ddf..164b29845b3a 100644
--- a/gcc/c-family/c-ubsan.cc
+++ b/gcc/c-family/c-ubsan.cc
@@ -376,6 +376,40 @@ ubsan_instrument_return (location_t loc)
   return build_call_expr_loc (loc, t, 1, build_fold_addr_expr_loc (loc, data));
 }
 
+/* Get the tree that represented the number of counted_by, i.e, the maximum
+   number of the elements of the object that the call to .ACCESS_WITH_SIZE
+   points to, this number will be the bound of the corresponding array.  */
+static tree
+get_bound_from_access_with_size (tree call)
+{
+  if (!is_access_with_size_p (call))
+    return NULL_TREE;
+
+  tree ref_to_size = CALL_EXPR_ARG (call, 1);
+  unsigned int type_of_size = TREE_INT_CST_LOW (CALL_EXPR_ARG (call, 2));
+  tree type = TREE_TYPE (CALL_EXPR_ARG (call, 3));
+  tree size = fold_build2 (MEM_REF, type, unshare_expr (ref_to_size),
+			   build_int_cst (ptr_type_node, 0));
+  /* If size is negative value, treat it as zero.  */
+  if (!TYPE_UNSIGNED (type))
+  {
+    tree cond = fold_build2 (LT_EXPR, boolean_type_node,
+			     unshare_expr (size), build_zero_cst (type));
+    size = fold_build3 (COND_EXPR, type, cond,
+			build_zero_cst (type), size);
+  }
+
+  /* Only when type_of_size is 1,i.e, the number of the elements of
+     the object type, return the size.  */
+  if (type_of_size != 1)
+    return NULL_TREE;
+  else
+    size = fold_convert (sizetype, size);
+
+  return size;
+}
+
+
 /* Instrument array bounds for ARRAY_REFs.  We create special builtin,
    that gets expanded in the sanopt pass, and make an array dimension
    of it.  ARRAY is the array, *INDEX is an index to the array.
@@ -401,6 +435,14 @@ ubsan_instrument_bounds (location_t loc, tree array, tree *index,
 	  && COMPLETE_TYPE_P (type)
 	  && integer_zerop (TYPE_SIZE (type)))
 	bound = build_int_cst (TREE_TYPE (TYPE_MIN_VALUE (domain)), -1);
+      else if (INDIRECT_REF_P (array)
+	       && is_access_with_size_p ((TREE_OPERAND (array, 0))))
+	{
+	  bound = get_bound_from_access_with_size ((TREE_OPERAND (array, 0)));
+	  bound = fold_build2 (MINUS_EXPR, TREE_TYPE (bound),
+			       bound,
+			       build_int_cst (TREE_TYPE (bound), 1));
+	}
       else
 	return NULL_TREE;
     }
diff --git a/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds-2.c b/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds-2.c
new file mode 100644
index 000000000000..148934975ee5
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds-2.c
@@ -0,0 +1,45 @@
+/* test the attribute counted_by and its usage in
+   bounds sanitizer combined with VLA.  */
+/* { dg-do run } */
+/* { dg-options "-fsanitize=bounds" } */
+/* { dg-output "index 11 out of bounds for type 'int \\\[\\\*\\\]\\\[\\\*\\\]'\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "\[^\n\r]*index 20 out of bounds for type 'int \\\[\\\*\\\]\\\[\\\*\\\]\\\[\\\*\\\]'\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "\[^\n\r]*index 11 out of bounds for type 'int \\\[\\\*\\\]\\\[\\\*\\\]'\[^\n\r]*(\n|\r\n|\r)" } */
+/* { dg-output "\[^\n\r]*index 10 out of bounds for type 'int \\\[\\\*\\\]'\[^\n\r]*(\n|\r\n|\r)" } */
+
+
+#include <stdlib.h>
+
+void __attribute__((__noinline__)) setup_and_test_vla (int n, int m)
+{
+   struct foo {
+       int n;
+       int p[][n] __attribute__((counted_by(n)));
+   } *f;
+
+   f = (struct foo *) malloc (sizeof(struct foo) + m*sizeof(int[n]));
+   f->n = m;
+   f->p[m][n-1]=1;
+   return;
+}
+
+void __attribute__((__noinline__)) setup_and_test_vla_1 (int n1, int n2, int m)
+{
+  struct foo {
+    int n;
+    int p[][n2][n1] __attribute__((counted_by(n)));
+  } *f;
+
+  f = (struct foo *) malloc (sizeof(struct foo) + m*sizeof(int[n2][n1]));
+  f->n = m;
+  f->p[m][n2][n1]=1;
+  return;
+}
+
+int main(int argc, char *argv[])
+{
+  setup_and_test_vla (10, 11);
+  setup_and_test_vla_1 (10, 11, 20);
+  return 0;
+}
+
diff --git a/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds-3.c b/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds-3.c
new file mode 100644
index 000000000000..33bdea1c430b
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds-3.c
@@ -0,0 +1,34 @@
+/* test the attribute counted_by and its usage in bounds
+   sanitizer. when counted_by field is negative value.  */
+/* { dg-do run } */
+/* { dg-options "-fsanitize=bounds" } */
+
+#include <stdlib.h>
+
+struct annotated {
+  int b;
+  int c[] __attribute__ ((counted_by (b)));
+} *array_annotated;
+
+void __attribute__((__noinline__)) setup (int annotated_count)
+{
+  array_annotated
+    = (struct annotated *)malloc (sizeof (struct annotated));
+  array_annotated->b = annotated_count;
+
+  return;
+}
+
+void __attribute__((__noinline__)) test (int annotated_index)
+{
+  array_annotated->c[annotated_index] = 2;
+}
+
+int main(int argc, char *argv[])
+{
+  setup (-3);   
+  test (2);
+  return 0;
+}
+
+/* { dg-output "24:21: runtime error: index 2 out of bounds for type" } */
diff --git a/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds.c b/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds.c
new file mode 100644
index 000000000000..81eaeb3f2681
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds.c
@@ -0,0 +1,46 @@
+/* test the attribute counted_by and its usage in
+   bounds sanitizer.  */
+/* { dg-do run } */
+/* { dg-options "-fsanitize=bounds" } */
+
+#include <stdlib.h>
+
+struct flex {
+  int b;
+  int c[];
+} *array_flex;
+
+struct annotated {
+  int b;
+  int c[] __attribute__ ((counted_by (b)));
+} *array_annotated;
+
+void __attribute__((__noinline__)) setup (int normal_count, int annotated_count)
+{
+  array_flex
+    = (struct flex *)malloc (sizeof (struct flex)
+			     + normal_count *  sizeof (int));
+  array_flex->b = normal_count;
+
+  array_annotated
+    = (struct annotated *)malloc (sizeof (struct annotated)
+				  + annotated_count *  sizeof (int));
+  array_annotated->b = annotated_count;
+
+  return;
+}
+
+void __attribute__((__noinline__)) test (int normal_index, int annotated_index)
+{
+  array_flex->c[normal_index] = 1;
+  array_annotated->c[annotated_index] = 2;
+}
+
+int main(int argc, char *argv[])
+{
+  setup (10, 10);   
+  test (10, 10);
+  return 0;
+}
+
+/* { dg-output "36:21: runtime error: index 10 out of bounds for type" } */
