Re: [PATCH v2 19/20] [RFC] task_struct: Allow randomized layout

[Linus Torvalds]

On Fri, May 26, 2017 at 1:17 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> This marks most of the layout of task_struct as randomizable, but leaves
> thread_info and scheduler state untouched at the start, and thread_struct
> untouched at the end.

I think you want to abstract this out somehow, because this is both
ugly and bad:

> +       /* This begins the randomizable portion of task_struct... */
> +#if GCC_VERSION >= 40600
> +       struct {
> +#endif

when you could instead just introduce something like

#if GCC_VERSION >= 40600
  #define randomized_struct_fields_start struct {
  #define randomized_struct_fields_end } __randomize_layout;
#else
  #define randomized_struct_fields_start
  #define randomized_struct_fields_end
#endif

and then this pattern is
 (a) more-or-less self-documenting
 (b) usable in other places too.
 (c) maybe some future compiler wants that struct field to have some
"randomize-me attribute" or something

Hmm?