Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct mmp_path.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Helge Deller <deller@gmx.de>
Cc: linux-fbdev@vger.kernel.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/video/mmp_disp.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/video/mmp_disp.h b/include/video/mmp_disp.h
index 77252cb46361..a722dcbf5073 100644
--- a/include/video/mmp_disp.h
+++ b/include/video/mmp_disp.h
@@ -231,7 +231,7 @@ struct mmp_path {
 
 	/* layers */
 	int overlay_num;
-	struct mmp_overlay overlays[];
+	struct mmp_overlay overlays[] __counted_by(overlay_num);
 };
 
 extern struct mmp_path *mmp_get_path(const char *name);
-- 
2.34.1

On 9/22/23 11:51, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct mmp_path.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Helge Deller <deller@gmx.de>
> Cc: linux-fbdev@vger.kernel.org
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
-- 
Gustavo

> ---
>   include/video/mmp_disp.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/video/mmp_disp.h b/include/video/mmp_disp.h
> index 77252cb46361..a722dcbf5073 100644
> --- a/include/video/mmp_disp.h
> +++ b/include/video/mmp_disp.h
> @@ -231,7 +231,7 @@ struct mmp_path {
>   
>   	/* layers */
>   	int overlay_num;
> -	struct mmp_overlay overlays[];
> +	struct mmp_overlay overlays[] __counted_by(overlay_num);
>   };
>   
>   extern struct mmp_path *mmp_get_path(const char *name);