[V3][PATCH 3/3] Use the counted_by attribute information in bound sanitizer[PR108896]

[Qing Zhao <qing.zhao@oracle.com>]

Use the counted_by attribute information in bound sanitizer.

gcc/c-family/ChangeLog:

	PR C/108896
	* c-ubsan.cc (ubsan_instrument_bounds): Use counted_by attribute
	information.

gcc/testsuite/ChangeLog:

	PR C/108896
	* gcc.dg/ubsan/flex-array-counted-by-bounds.c: New test.
	* gcc.dg/ubsan/flex-array-counted-by-bounds-2.c: New test.
---
 gcc/c-family/c-ubsan.cc                       | 16 +++++++
 .../ubsan/flex-array-counted-by-bounds-2.c    | 27 +++++++++++
 .../ubsan/flex-array-counted-by-bounds.c      | 46 +++++++++++++++++++
 3 files changed, 89 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds-2.c
 create mode 100644 gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds.c

diff --git a/gcc/c-family/c-ubsan.cc b/gcc/c-family/c-ubsan.cc
index 51aa83a378d2..a99e8433069f 100644
--- a/gcc/c-family/c-ubsan.cc
+++ b/gcc/c-family/c-ubsan.cc
@@ -362,6 +362,10 @@ ubsan_instrument_bounds (location_t loc, tree array, tree *index,
 {
   tree type = TREE_TYPE (array);
   tree domain = TYPE_DOMAIN (type);
+  /* whether the array ref is a flexible array member with valid counted_by
+     attribute.  */
+  bool fam_has_count_attr = false;
+  tree counted_by = NULL_TREE;
 
   if (domain == NULL_TREE)
     return NULL_TREE;
@@ -375,6 +379,17 @@ 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);
+      /* If the array ref is to flexible array member field which has
+	 counted_by attribute.  We can use the information from the
+	 attribute as the bound to instrument the reference.  */
+      else if ((counted_by = component_ref_get_counted_by (array))
+		!= NULL_TREE)
+	{
+	  fam_has_count_attr = true;
+	  bound = fold_build2 (MINUS_EXPR, TREE_TYPE (counted_by),
+			       counted_by,
+			       build_int_cst (TREE_TYPE (counted_by), 1));
+	}
       else
 	return NULL_TREE;
     }
@@ -387,6 +402,7 @@ ubsan_instrument_bounds (location_t loc, tree array, tree *index,
      -fsanitize=bounds-strict.  */
   tree base = get_base_address (array);
   if (!sanitize_flags_p (SANITIZE_BOUNDS_STRICT)
+      && !fam_has_count_attr
       && TREE_CODE (array) == COMPONENT_REF
       && base && (INDIRECT_REF_P (base) || TREE_CODE (base) == MEM_REF))
     {
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..77ec333509d0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/ubsan/flex-array-counted-by-bounds-2.c
@@ -0,0 +1,27 @@
+/* test the attribute counted_by and its usage in
+   bounds sanitizer combined with VLA.  */
+/* { dg-do run } */
+/* { dg-options "-fsanitize=bounds" } */
+
+#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;
+}
+
+int main(int argc, char *argv[])
+{
+  setup_and_test_vla (10, 11);
+  return 0;
+}
+
+/* { dg-output "17:8: runtime error: index 11 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" } */
-- 
2.31.1