Re: [PATCH] net/mlx5: Annotate struct mlx5_fc_bulk with __counted_by

[Justin Stitt]

On Tue, Oct 3, 2023 at 4:17 PM Kees Cook <keescook@xxxxxxxxxxxx> 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 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 mlx5_fc_bulk.
>
> Cc: Saeed Mahameed <saeedm@xxxxxxxxxx>
> Cc: Leon Romanovsky <leon@xxxxxxxxxx>
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
> Cc: Jakub Kicinski <kuba@xxxxxxxxxx>
> Cc: Paolo Abeni <pabeni@xxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: linux-rdma@xxxxxxxxxxxxxxx
> Link: https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci [1]
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c b/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
> index 17fe30a4c06c..0c26d707eed2 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/fs_counters.c
> @@ -539,7 +539,7 @@ struct mlx5_fc_bulk {
>         u32 base_id;
>         int bulk_len;
>         unsigned long *bitmask;
> -       struct mlx5_fc fcs[];
> +       struct mlx5_fc fcs[] __counted_by(bulk_len);
>  };

This looks good.

`bulk->bulk_len` is assigned before flexible array member `fcs` is accessed.

        bulk->bulk_len = bulk_len;
        for (i = 0; i < bulk_len; i++) {
                mlx5_fc_init(&bulk->fcs[i], bulk, base_id + i);
                set_bit(i, bulk->bitmask);
        }

Reviewed-by: Justin Stitt <justinstitt@xxxxxxxxxx>
>
>  static void mlx5_fc_init(struct mlx5_fc *counter, struct mlx5_fc_bulk *bulk,
> --
> 2.34.1
>
>
Thanks
Justin