linux-hardening - Re: [PATCH v2 12/63] thermal: intel: int340x_thermal: Use struct

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Date:   Tue, 23 Nov 2021 14:19:25 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Kees Cook <keescook@...omium.org>, Zhang Rui <rui.zhang@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Amit Kucheria <amitk@...nel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "open list:NETWORKING DRIVERS (WIRELESS)" 
        <linux-wireless@...r.kernel.org>, netdev <netdev@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-staging@...ts.linux.dev, linux-block@...r.kernel.org,
        linux-kbuild@...r.kernel.org, clang-built-linux@...glegroups.com,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 12/63] thermal: intel: int340x_thermal: Use
 struct_group() for memcpy() region

On Wed, Aug 18, 2021 at 8:08 AM Kees Cook <keescook@...omium.org> 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@...el.com>
> Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
> Cc: Amit Kucheria <amitk@...nel.org>
> Cc: linux-pm@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

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
>