Re: [PATCH v2 12/63] thermal: intel: int340x_thermal: Use struct_group() for memcpy() region

[Rafael J. Wysocki]

On Wed, Aug 18, 2021 at 8:08 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memcpy(), avoid intentionally writing across
> neighboring fields.
>
> Use struct_group() in struct art around members weight, and ac[0-9]_max,
> so they can be referenced together. This will allow memcpy() and sizeof()
> to more easily reason about sizes, improve readability, and avoid future
> warnings about writing beyond the end of weight.
>
> "pahole" shows no size nor member offset changes to struct art.
> "objdump -d" shows no meaningful object code changes (i.e. only source
> line number induced differences).
>
> Cc: Zhang Rui <rui.zhang@xxxxxxxxx>
> Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> Cc: Amit Kucheria <amitk@xxxxxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>

Rui, Srinivas, any comments here?

> ---
>  .../intel/int340x_thermal/acpi_thermal_rel.c  |  5 +-
>  .../intel/int340x_thermal/acpi_thermal_rel.h  | 48 ++++++++++---------
>  2 files changed, 29 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
> index a478cff8162a..e90690a234c4 100644
> --- a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
> +++ b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.c
> @@ -250,8 +250,9 @@ static int fill_art(char __user *ubuf)
>                 get_single_name(arts[i].source, art_user[i].source_device);
>                 get_single_name(arts[i].target, art_user[i].target_device);
>                 /* copy the rest int data in addition to source and target */
> -               memcpy(&art_user[i].weight, &arts[i].weight,
> -                       sizeof(u64) * (ACPI_NR_ART_ELEMENTS - 2));
> +               BUILD_BUG_ON(sizeof(art_user[i].data) !=
> +                            sizeof(u64) * (ACPI_NR_ART_ELEMENTS - 2));
> +               memcpy(&art_user[i].data, &arts[i].data, sizeof(art_user[i].data));
>         }
>
>         if (copy_to_user(ubuf, art_user, art_len))
> diff --git a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.h b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.h
> index 58822575fd54..78d942477035 100644
> --- a/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.h
> +++ b/drivers/thermal/intel/int340x_thermal/acpi_thermal_rel.h
> @@ -17,17 +17,19 @@
>  struct art {
>         acpi_handle source;
>         acpi_handle target;
> -       u64 weight;
> -       u64 ac0_max;
> -       u64 ac1_max;
> -       u64 ac2_max;
> -       u64 ac3_max;
> -       u64 ac4_max;
> -       u64 ac5_max;
> -       u64 ac6_max;
> -       u64 ac7_max;
> -       u64 ac8_max;
> -       u64 ac9_max;
> +       struct_group(data,
> +               u64 weight;
> +               u64 ac0_max;
> +               u64 ac1_max;
> +               u64 ac2_max;
> +               u64 ac3_max;
> +               u64 ac4_max;
> +               u64 ac5_max;
> +               u64 ac6_max;
> +               u64 ac7_max;
> +               u64 ac8_max;
> +               u64 ac9_max;
> +       );
>  } __packed;
>
>  struct trt {
> @@ -47,17 +49,19 @@ union art_object {
>         struct {
>                 char source_device[8]; /* ACPI single name */
>                 char target_device[8]; /* ACPI single name */
> -               u64 weight;
> -               u64 ac0_max_level;
> -               u64 ac1_max_level;
> -               u64 ac2_max_level;
> -               u64 ac3_max_level;
> -               u64 ac4_max_level;
> -               u64 ac5_max_level;
> -               u64 ac6_max_level;
> -               u64 ac7_max_level;
> -               u64 ac8_max_level;
> -               u64 ac9_max_level;
> +               struct_group(data,
> +                       u64 weight;
> +                       u64 ac0_max_level;
> +                       u64 ac1_max_level;
> +                       u64 ac2_max_level;
> +                       u64 ac3_max_level;
> +                       u64 ac4_max_level;
> +                       u64 ac5_max_level;
> +                       u64 ac6_max_level;
> +                       u64 ac7_max_level;
> +                       u64 ac8_max_level;
> +                       u64 ac9_max_level;
> +               );
>         };
>         u64 __data[ACPI_NR_ART_ELEMENTS];
>  };
> --
> 2.30.2
>