[Mesa-dev] [PATCH 1/2] glsl: fix use-after free bug/crash in ast_declarator_list::hir()

[Ian Romanick]

On 05/23/2014 02:22 PM, Brian Paul wrote:
> The call to get_variable_being_redeclared() may delete 'var' so we
> can't reference var->name afterward.  We fix that by examining the
> var's name before making that call.
> 
> Fixes valgrind warnings and possible crash when running the piglit
> tests/spec/glsl-1.30/execution/clipping/vs-clip-distance-in-param.shader_test
> test (and probably others).
> 
> Cc: "10.1 10.2" <mesa-stable at lists.freedesktop.org>
> ---
>  src/glsl/ast_to_hir.cpp |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/src/glsl/ast_to_hir.cpp b/src/glsl/ast_to_hir.cpp
> index 0128b3f..e06f9b4 100644
> --- a/src/glsl/ast_to_hir.cpp
> +++ b/src/glsl/ast_to_hir.cpp
> @@ -3651,11 +3651,15 @@ ast_declarator_list::hir(exec_list *instructions,
>         * instruction stream.
>         */
>        exec_list initializer_instructions;
> +
> +      /* Examine var name here since var may get deleted in the next call */
> +      bool var_is_gl_id = (strncmp(var->name, "gl_", 3) == 0);
> +
>        ir_variable *earlier =
>           get_variable_being_redeclared(var, decl->get_location(), state,
>                                         false /* allow_all_redeclarations */);
>        if (earlier != NULL) {
> -         if (strncmp(var->name, "gl_", 3) == 0 &&
> +         if (var_is_gl_id &&

I think this could also be

         if (strncmp(earlier->name, "gl_", 3) == 0 &&

since var and earlier are supposed to be the same variable.  Either way,

Reviewed-by: Ian Romanick <ian.d.romanick at intel.com>

>               earlier->data.how_declared == ir_var_declared_in_block) {
>              _mesa_glsl_error(&loc, state,
>                               "`%s' has already been redeclared using "
>