linux-kernel - Re: [PATCH] net/mlx5e: Replace 0-length array with flexible array

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Message-ID: <Y7hHxKgX24+pGCsI@work>
Date:   Fri, 6 Jan 2023 10:09:40 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH] net/mlx5e: Replace 0-length array with flexible array

On Thu, Jan 05, 2023 at 02:36:43PM -0800, Kees Cook wrote:
> Zero-length arrays are deprecated[1]. Replace struct mlx5e_rx_wqe_cyc's
> "data" 0-length array with a flexible array. Detected with GCC 13,
> using -fstrict-flex-arrays=3:
> 
> drivers/net/ethernet/mellanox/mlx5/core/en_main.c: In function 'mlx5e_alloc_rq':
> drivers/net/ethernet/mellanox/mlx5/core/en_main.c:827:42: warning: array subscript f is outside array bounds of 'struct mlx5_wqe_data_seg[0]' [-Warray-bounds=]
>   827 |                                 wqe->data[f].byte_count = 0;
>       |                                 ~~~~~~~~~^~~
> In file included from drivers/net/ethernet/mellanox/mlx5/core/en/tc_ct.h:11,
>                  from drivers/net/ethernet/mellanox/mlx5/core/eswitch.h:48,
>                  from drivers/net/ethernet/mellanox/mlx5/core/en_main.c:42:
> drivers/net/ethernet/mellanox/mlx5/core/en.h:250:39: note: while referencing 'data'
>   250 |         struct mlx5_wqe_data_seg      data[0];
>       |                                       ^~~~
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Cc: Saeed Mahameed <saeedm@...dia.com>
> Cc: Leon Romanovsky <leon@...nel.org>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
> Cc: netdev@...r.kernel.org
> Cc: linux-rdma@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>

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

Thanks!
--
Gustavo

> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> index 2d77fb8a8a01..37cf3b1bb144 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> @@ -247,7 +247,7 @@ struct mlx5e_rx_wqe_ll {
>  };
>  
>  struct mlx5e_rx_wqe_cyc {
> -	struct mlx5_wqe_data_seg      data[0];
> +	DECLARE_FLEX_ARRAY(struct mlx5_wqe_data_seg, data);
>  };
>  
>  struct mlx5e_umr_wqe {
> -- 
> 2.34.1
>