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

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

Ping.

thanks.

Qing

> On Aug 25, 2023, at 11:24 AM, Qing Zhao <qing.zhao@oracle.com> wrote:
> 
> 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
>