Re: [PATCH v3 28/54] dyndbg: restore classmap protection when theres a controlling_param

[Sean Paul]

On Thu, Apr 3, 2025 at 9:48 AM Jim Cromie <jim.cromie@xxxxxxxxx> wrote:
>

\snip

>
> -static void ddebug_match_apply_kparam(const struct kernel_param *kp,
> -                                     const struct _ddebug_class_map *map,
> -                                     const char *mod_name)
> +static struct _ddebug_class_param *
> +ddebug_get_classmap_kparam(const struct kernel_param *kp,
> +                          const struct _ddebug_class_map *map)
>  {
>         struct _ddebug_class_param *dcp;
>
>         if (kp->ops != &param_ops_dyndbg_classes)
> -               return;
> +               return false;

Return type is struct _ddebug_class_param *, should this be NULL?

>
>         dcp = (struct _ddebug_class_param *)kp->arg;
>
> -       if (map == dcp->map) {
> +       return (map == dcp->map)
> +               ? dcp : (struct _ddebug_class_param *)NULL;
> +}
> +
> +static void ddebug_match_apply_kparam(const struct kernel_param *kp,
> +                                     struct _ddebug_class_map *map,
> +                                     const char *mod_name)
> +{
> +       struct _ddebug_class_param *dcp = ddebug_get_classmap_kparam(kp, map);
> +
> +       if (dcp) {
> +               map->controlling_param = dcp;
>                 v2pr_info(" kp:%s.%s =0x%lx", mod_name, kp->name, *dcp->bits);
>                 vpr_cm_info(map, " %s mapped to: ", mod_name);
>                 ddebug_sync_classbits(kp, mod_name);
>         }
>  }
>
> -static void ddebug_apply_params(const struct _ddebug_class_map *cm, const char *mod_name)
> +static void ddebug_apply_params(struct _ddebug_class_map *cm, const char *mod_name)
>  {
>         const struct kernel_param *kp;
>  #if IS_ENABLED(CONFIG_MODULES)
> @@ -1266,6 +1288,13 @@ static void ddebug_apply_params(const struct _ddebug_class_map *cm, const char *
>         }
>  }
>
> +/*
> + * called from add_module, ie early. it can find controlling kparams,
> + * which can/does? enable protection of this classmap from class-less
> + * queries, on the grounds that the user created the kparam, means to
> + * use it, and expects it to reflect reality.  We should oblige him,
> + * and protect those classmaps from classless "-p" changes.
> + */
>  static void ddebug_apply_class_maps(const struct _ddebug_info *di)
>  {
>         struct _ddebug_class_map *cm;
> --
> 2.49.0
>