Re: [PATCH][next] nouveau/gsp: replace zero-length array with flex-array member and use __counted_by

Kees Cook
2023-11-16T18:28:41Z

On Thu, Nov 16, 2023 at 12:11:43PM -0600, Gustavo A. R. Silva wrote:
> Fake flexible arrays (zero-length and one-element arrays) are deprecated,
> and should be replaced by flexible-array members. So, replace
> zero-length array with a flexible-array member in `struct
> PACKED_REGISTRY_TABLE`.
>
> Also annotate array `entries` with `__counted_by()` to 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 via `CONFIG_UBSAN_BOUNDS` (for array
> indexing) and `CONFIG_FORTIFY_SOURCE` (for strcpy/memcpy-family functions).
>
> This fixes multiple -Warray-bounds warnings:
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1069:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1070:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1071:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
> drivers/gpu/drm/nouveau/nvkm/subdev/gsp/r535.c:1072:29: warning: array subscript 0 is outside array bounds of 'PACKED_REGISTRY_ENTRY[0]' [-Warray-bounds=]
>
> While there, also make use of the struct_size() helper, and address
> checkpatch.pl warning:
> WARNING: please, no spaces at the start of a line
>
> This results in no differences in binary output.
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Looks nice to me.

Reviewed-by: Kees Cook <keescook@chromium.org>

--
Kees Cook