Re: [PATCH] bcachefs: Annotate struct bucket_array with __counted_by()

Kees Cook
2024-08-22T17:35:57Z

On Wed, Aug 21, 2024 at 06:29:22PM +0200, Thorsten Blum wrote:
> Add the __counted_by compiler attribute to the flexible array member
> bucket to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
> CONFIG_FORTIFY_SOURCE.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
> ---
> fs/bcachefs/buckets_types.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/bcachefs/buckets_types.h b/fs/bcachefs/buckets_types.h
> index c9698cdf866f..a19460a1bb7c 100644
> --- a/fs/bcachefs/buckets_types.h
> +++ b/fs/bcachefs/buckets_types.h
> @@ -24,7 +24,7 @@ struct bucket_array {
> u16 first_bucket;
> size_t nbuckets;
> size_t nbuckets_minus_first;
> - struct bucket b[];
> + struct bucket b[] __counted_by(nbuckets);
> };
>
> struct bucket_gens {

I only see this being allocated in one place and nbuckets is immediately
assigned to the count of "b" elements, so this looks correct to me.

Reviewed-by: Kees Cook <kees@kernel.org>

--
Kees Cook