Re: [PATCH][ubsan] Add VLA bound instrumentation

[Marek Polacek <polacek@redhat.com>]

Ping.

On Wed, Sep 25, 2013 at 02:41:32PM +0200, Marek Polacek wrote:
> On Thu, Sep 12, 2013 at 02:26:55PM +0200, Marek Polacek wrote:
> > This patch adds the instrumentation of VLA bounds.  Basically, it just checks that
> > the size of a VLA is positive.  I.e., We also issue an error if the size of the
> > VLA is 0.  It catches e.g.
> > 
> > int i = 1;
> > int a[i][i - 2];
> > 
> > It is pretty straightforward, but I had
> > issues in the C++ FE, mainly choosing the right spot where to instrument...
> > Hopefully I picked up the right one.  Also note that in C++1y we throw
> > an exception when the size of a VLA is negative; hence no need to perform
> > the instrumentation if -std=c++1y is in effect.
> > 
> > Regtested/ran bootstrap-ubsan on x86_64-linux, also
> > make check -C gcc RUNTESTFLAGS='--target_board=unix\{-m32,-m64\} ubsan.exp'
> > passes.
> > 
> > Ok for trunk?
> 
> I'd like to ping this patch; below is rebased version with the ubsan.c
> hunk omitted, since that part was already fixed by another patch.
> 
> (It still doesn't contain alloca/SIZE_MAX/... checking, since that
> very much relies on libubsan.  Still, it'd be felicitous to get at
> least the basic VLA checking in.)
> 
> Ran ubsan testsuite + bootstrap-ubsan on x86_64-linux.
> 
> 2013-09-25  Marek Polacek  <polacek@redhat.com>
> 
> 	* opts.c (common_handle_option): Handle vla-bound.
> 	* sanitizer.def (BUILT_IN_UBSAN_HANDLE_VLA_BOUND_NOT_POSITIVE):
> 	Define.
> 	* flag-types.h (enum sanitize_code): Add SANITIZE_VLA.
> 	* asan.c (initialize_sanitizer_builtins): Build BT_FN_VOID_PTR_PTR.
> c-family/
> 	* c-ubsan.c: Don't include hash-table.h.
> 	(ubsan_instrument_vla): New function.
> 	* c-ubsan.h: Declare it.
> cp/
> 	* decl.c (create_array_type_for_decl): Add VLA instrumentation.
> c/
> 	* c-decl.c (grokdeclarator): Add VLA instrumentation.
> testsuite/
> 	* g++.dg/ubsan/cxx1y-vla.C: New test.
> 	* c-c++-common/ubsan/vla-3.c: New test.
> 	* c-c++-common/ubsan/vla-2.c: New test.
> 	* c-c++-common/ubsan/vla-4.c: New test.
> 	* c-c++-common/ubsan/vla-1.c: New test.
> 
> --- gcc/opts.c.mp	2013-09-25 14:06:58.531276511 +0200
> +++ gcc/opts.c	2013-09-25 14:07:03.580294566 +0200
> @@ -1428,6 +1428,7 @@ common_handle_option (struct gcc_options
>  	      { "undefined", SANITIZE_UNDEFINED, sizeof "undefined" - 1 },
>  	      { "unreachable", SANITIZE_UNREACHABLE,
>  		sizeof "unreachable" - 1 },
> +	      { "vla-bound", SANITIZE_VLA, sizeof "vla-bound" - 1 },
>  	      { NULL, 0, 0 }
>  	    };
>  	    const char *comma;
> --- gcc/c-family/c-ubsan.c.mp	2013-09-25 14:06:58.535276527 +0200
> +++ gcc/c-family/c-ubsan.c	2013-09-25 14:07:03.580294566 +0200
> @@ -25,7 +25,6 @@ along with GCC; see the file COPYING3.
>  #include "alloc-pool.h"
>  #include "cgraph.h"
>  #include "gimple.h"
> -#include "hash-table.h"
>  #include "output.h"
>  #include "toplev.h"
>  #include "ubsan.h"
> @@ -86,8 +85,7 @@ ubsan_instrument_division (location_t lo
>    return t;
>  }
>  
> -/* Instrument left and right shifts.  If not instrumenting, return
> -   NULL_TREE.  */
> +/* Instrument left and right shifts.  */
>  
>  tree
>  ubsan_instrument_shift (location_t loc, enum tree_code code,
> @@ -157,4 +155,23 @@ ubsan_instrument_shift (location_t loc,
>    t = fold_build3 (COND_EXPR, void_type_node, t, tt, void_zero_node);
>  
>    return t;
> +}
> +
> +/* Instrument variable length array bound.  */
> +
> +tree
> +ubsan_instrument_vla (location_t loc, tree size)
> +{
> +  tree type = TREE_TYPE (size);
> +  tree t, tt;
> +
> +  t = fold_build2 (LE_EXPR, boolean_type_node, size, build_int_cst (type, 0));
> +  tree data = ubsan_create_data ("__ubsan_vla_data",
> +				 loc, ubsan_type_descriptor (type), NULL_TREE);
> +  data = build_fold_addr_expr_loc (loc, data);
> +  tt = builtin_decl_explicit (BUILT_IN_UBSAN_HANDLE_VLA_BOUND_NOT_POSITIVE);
> +  tt = build_call_expr_loc (loc, tt, 2, data, ubsan_encode_value (size));
> +  t = fold_build3 (COND_EXPR, void_type_node, t, tt, void_zero_node);
> +
> +  return t;
>  }
> --- gcc/c-family/c-ubsan.h.mp	2013-09-25 14:06:58.538276539 +0200
> +++ gcc/c-family/c-ubsan.h	2013-09-25 14:07:03.595294628 +0200
> @@ -23,5 +23,6 @@ along with GCC; see the file COPYING3.
>  
>  extern tree ubsan_instrument_division (location_t, tree, tree);
>  extern tree ubsan_instrument_shift (location_t, enum tree_code, tree, tree);
> +extern tree ubsan_instrument_vla (location_t, tree);
>  
>  #endif  /* GCC_C_UBSAN_H  */
> --- gcc/sanitizer.def.mp	2013-09-25 14:06:58.542276558 +0200
> +++ gcc/sanitizer.def	2013-09-25 14:07:03.628294753 +0200
> @@ -297,3 +297,7 @@ DEF_SANITIZER_BUILTIN(BUILT_IN_UBSAN_HAN
>  		      "__ubsan_handle_builtin_unreachable",
>  		      BT_FN_VOID_PTR,
>  		      ATTR_COLD_NORETURN_NOTHROW_LEAF_LIST)
> +DEF_SANITIZER_BUILTIN(BUILT_IN_UBSAN_HANDLE_VLA_BOUND_NOT_POSITIVE,
> +		      "__ubsan_handle_vla_bound_not_positive",
> +		      BT_FN_VOID_PTR_PTR,
> +		      ATTR_COLD_NOTHROW_LEAF_LIST)
> --- gcc/flag-types.h.mp	2013-09-25 14:06:58.546276575 +0200
> +++ gcc/flag-types.h	2013-09-25 14:07:03.629294757 +0200
> @@ -201,7 +201,9 @@ enum sanitize_code {
>    SANITIZE_SHIFT = 1 << 2,
>    SANITIZE_DIVIDE = 1 << 3,
>    SANITIZE_UNREACHABLE = 1 << 4,
> +  SANITIZE_VLA = 1 << 5,
>    SANITIZE_UNDEFINED = SANITIZE_SHIFT | SANITIZE_DIVIDE | SANITIZE_UNREACHABLE
> +		       | SANITIZE_VLA
>  };
>  
>  /* flag_vtable_verify initialization levels. */
> --- gcc/cp/decl.c.mp	2013-09-25 14:06:58.549276587 +0200
> +++ gcc/cp/decl.c	2013-09-25 14:07:20.640355737 +0200
> @@ -45,6 +45,7 @@ along with GCC; see the file COPYING3.
>  #include "c-family/c-objc.h"
>  #include "c-family/c-pragma.h"
>  #include "c-family/c-target.h"
> +#include "c-family/c-ubsan.h"
>  #include "diagnostic.h"
>  #include "intl.h"
>  #include "debug.h"
> @@ -8465,6 +8466,24 @@ create_array_type_for_decl (tree name, t
>    if (cxx_dialect >= cxx1y && array_of_runtime_bound_p (type))
>      pedwarn (input_location, OPT_Wvla, "array of array of runtime bound");
>  
> +  /* Do the instrumentation of VLAs if desired.  */
> +  if ((flag_sanitize & SANITIZE_VLA)
> +      && size && !TREE_CONSTANT (size)
> +      /* From C++1y onwards, we throw an exception on a negative length size
> +         of an array.  */
> +      && cxx_dialect < cxx1y)
> +    {
> +      /* Prevent bogus set-but-not-used warnings: we're definitely using
> +         the variable.  */
> +      if (VAR_P (size))
> +        DECL_READ_P (size) = 1;
> +      /* Evaluate the array size only once.  */
> +      size = cp_save_expr (size);
> +      size = fold_build2 (COMPOUND_EXPR, TREE_TYPE (size),
> +			  ubsan_instrument_vla (input_location, size),
> +			  size);
> +    }
> +
>    /* Figure out the index type for the array.  */
>    if (size)
>      itype = compute_array_index_type (name, size, tf_warning_or_error);
> --- gcc/c/c-decl.c.mp	2013-09-25 14:06:58.550276591 +0200
> +++ gcc/c/c-decl.c	2013-09-25 14:07:03.644294820 +0200
> @@ -45,6 +45,7 @@ along with GCC; see the file COPYING3.
>  #include "c-family/c-common.h"
>  #include "c-family/c-objc.h"
>  #include "c-family/c-pragma.h"
> +#include "c-family/c-ubsan.h"
>  #include "c-lang.h"
>  #include "langhooks.h"
>  #include "tree-iterator.h"
> @@ -5378,6 +5379,16 @@ grokdeclarator (const struct c_declarato
>  		       with known value.  */
>  		    this_size_varies = size_varies = true;
>  		    warn_variable_length_array (name, size);
> +		    if (flag_sanitize & SANITIZE_VLA
> +		        && decl_context == NORMAL)
> +		      {
> +			/* Evaluate the array size only once.  */
> +			size = c_save_expr (size);
> +			size = c_fully_fold (size, false, NULL);
> +		        size = fold_build2 (COMPOUND_EXPR, TREE_TYPE (size),
> +					    ubsan_instrument_vla (loc, size),
> +					    size);
> +		      }
>  		  }
>  
>  		if (integer_zerop (size) && !this_size_varies)
> --- gcc/testsuite/g++.dg/ubsan/cxx1y-vla.C.mp	2013-09-25 14:08:33.263616709 +0200
> +++ gcc/testsuite/g++.dg/ubsan/cxx1y-vla.C	2013-09-25 14:07:03.650294845 +0200
> @@ -0,0 +1,13 @@
> +/* { dg-do run } */
> +/* { dg-options "-fsanitize=vla-bound -w -std=c++1y" } */
> +/* { dg-shouldfail "ubsan" } */
> +
> +int
> +main (void)
> +{
> +  int y = -18;
> +  int a[y];
> +  return 0;
> +}
> +
> +/* { dg-output "terminate called after throwing an instance" } */
> --- gcc/testsuite/c-c++-common/ubsan/vla-3.c.mp	2013-09-25 14:08:25.364588140 +0200
> +++ gcc/testsuite/c-c++-common/ubsan/vla-3.c	2013-09-25 14:07:03.650294845 +0200
> @@ -0,0 +1,16 @@
> +/* { dg-do run } */
> +/* { dg-options "-fsanitize=vla-bound -w" } */
> +
> +/* Don't instrument the arrays here.  */
> +int
> +foo (int n, int a[])
> +{
> +  return a[n - 1];
> +}
> +
> +int
> +main (void)
> +{
> +  int a[6] = { };
> +  return foo (3, a);
> +}
> --- gcc/testsuite/c-c++-common/ubsan/vla-2.c.mp	2013-09-25 14:08:23.458581265 +0200
> +++ gcc/testsuite/c-c++-common/ubsan/vla-2.c	2013-09-25 14:07:03.651294849 +0200
> @@ -0,0 +1,15 @@
> +/* { dg-do run } */
> +/* { dg-options "-fsanitize=vla-bound -w" } */
> +
> +int
> +main (void)
> +{
> +  const int t = 0;
> +  struct s {
> +    int x;
> +    /* Don't instrument this one.  */
> +    int g[t];
> +  };
> +
> +  return 0;
> +}
> --- gcc/testsuite/c-c++-common/ubsan/vla-4.c.mp	2013-09-25 14:08:27.367595369 +0200
> +++ gcc/testsuite/c-c++-common/ubsan/vla-4.c	2013-09-25 14:07:03.652294853 +0200
> @@ -0,0 +1,13 @@
> +/* { dg-do run } */
> +/* { dg-options "-fsanitize=vla-bound" } */
> +
> +int
> +main (void)
> +{
> +  int x = 1;
> +  /* Check that the size of an array is evaluated only once.  */
> +  int a[++x];
> +  if (x != 2)
> +    __builtin_abort ();
> +  return 0;
> +}
> --- gcc/testsuite/c-c++-common/ubsan/vla-1.c.mp	2013-09-25 14:08:21.341573677 +0200
> +++ gcc/testsuite/c-c++-common/ubsan/vla-1.c	2013-09-25 14:07:03.652294853 +0200
> @@ -0,0 +1,48 @@
> +/* { dg-do run } */
> +/* { dg-options "-fsanitize=vla-bound -w" } */
> +
> +static int
> +bar (void)
> +{
> +  return -42;
> +}
> +
> +typedef long int V;
> +int
> +main (void)
> +{
> +  int x = -1;
> +  double di = -3.2;
> +  V v = -666;
> +
> +  int a[x];
> +  int aa[x][x];
> +  int aaa[x][x][x];
> +  int b[x - 4];
> +  int c[(int) di];
> +  int d[1 + x];
> +  int e[1 ? x : -1];
> +  int f[++x];
> +  int g[(signed char) --x];
> +  int h[(++x, --x, x)];
> +  int i[v];
> +  int j[bar ()];
> +
> +  return 0;
> +}
> +
> +/* { dg-output "variable length array bound evaluates to non-positive value -1(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -1(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -1(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -1(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -1(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -1(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -5(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -3(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value 0(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -1(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value 0(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -1(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -1(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -666(\n|\r\n|\r)" } */
> +/* { dg-output "\[^\n\r]*variable length array bound evaluates to non-positive value -42(\n|\r\n|\r)" } */
> --- gcc/asan.c.mp	2013-09-25 14:06:58.557276623 +0200
> +++ gcc/asan.c	2013-09-25 14:07:03.653294857 +0200
> @@ -2018,6 +2018,9 @@ initialize_sanitizer_builtins (void)
>    tree BT_FN_VOID = build_function_type_list (void_type_node, NULL_TREE);
>    tree BT_FN_VOID_PTR
>      = build_function_type_list (void_type_node, ptr_type_node, NULL_TREE);
> +  tree BT_FN_VOID_PTR_PTR
> +    = build_function_type_list (void_type_node, ptr_type_node,
> +				ptr_type_node, NULL_TREE);
>    tree BT_FN_VOID_PTR_PTR_PTR
>      = build_function_type_list (void_type_node, ptr_type_node,
>  				ptr_type_node, ptr_type_node, NULL_TREE);
> 
> 	Marek

	Marek