linux-hardening - Re: [PATCH][next] net/mlx4_en: Replace fake flex-array with flexible-array member

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Date:   Tue, 7 Mar 2023 08:07:46 +0200
From:   Tariq Toukan <ttoukan.linux@...il.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Tariq Toukan <tariqt@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] net/mlx4_en: Replace fake flex-array with
 flexible-array member



On 07/03/2023 1:51, Gustavo A. R. Silva wrote:
> Zero-length arrays as fake flexible arrays are deprecated and we are
> moving towards adopting C99 flexible-array members instead.
> 
> Transform zero-length array into flexible-array member in struct
> mlx4_en_rx_desc.
> 
> Address the following warnings found with GCC-13 and
> -fstrict-flex-arrays=3 enabled:
> drivers/net/ethernet/mellanox/mlx4/en_rx.c:88:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
> drivers/net/ethernet/mellanox/mlx4/en_rx.c:149:30: warning: array subscript 0 is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
> drivers/net/ethernet/mellanox/mlx4/en_rx.c:127:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
> drivers/net/ethernet/mellanox/mlx4/en_rx.c:128:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
> drivers/net/ethernet/mellanox/mlx4/en_rx.c:129:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
> drivers/net/ethernet/mellanox/mlx4/en_rx.c:117:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
> drivers/net/ethernet/mellanox/mlx4/en_rx.c:119:30: warning: array subscript i is outside array bounds of ‘struct mlx4_wqe_data_seg[0]’ [-Warray-bounds=]
> 
> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
> routines on memcpy() and help us make progress towards globally
> enabling -fstrict-flex-arrays=3 [1].
> 
> Link: https://github.com/KSPP/linux/issues/21
> Link: https://github.com/KSPP/linux/issues/264
> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
>   drivers/net/ethernet/mellanox/mlx4/mlx4_en.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> index 544e09b97483..034733b13b1a 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> +++ b/drivers/net/ethernet/mellanox/mlx4/mlx4_en.h
> @@ -323,7 +323,7 @@ struct mlx4_en_tx_ring {
>   
>   struct mlx4_en_rx_desc {
>   	/* actual number of entries depends on rx ring stride */
> -	struct mlx4_wqe_data_seg data[0];
> +	DECLARE_FLEX_ARRAY(struct mlx4_wqe_data_seg, data);
>   };
>   
>   struct mlx4_en_rx_ring {

Reviewed-by: Tariq Toukan <tariqt@...dia.com>

Thanks for your patch.