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Date:   Fri, 6 Jan 2023 10:12:44 -0600
From:   "Gustavo A. R. Silva" <gustavoars@kernel.org>
To:     Kees Cook <keescook@chromium.org>
Cc:     Ido Schimmel <idosch@nvidia.com>, Petr Machata <petrm@nvidia.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH] mlxsw: spectrum_router: Replace 0-length array with
 flexible array
Message-ID: <Y7hIfF8uyU59/94l@work>
References: <20230105232224.never.150-kees@kernel.org>
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On Thu, Jan 05, 2023 at 03:22:29PM -0800, Kees Cook wrote:
> Zero-length arrays are deprecated[1]. Replace struct
> mlxsw_sp_nexthop_group_info's "nexthops" 0-length array with a flexible
> array. Detected with GCC 13, using -fstrict-flex-arrays=3:
> 
> drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c: In function 'mlxsw_sp_nexthop_group_hash_obj':
> drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:3278:38: warning: array subscript i is outside array bounds of 'struct mlxsw_sp_nexthop[0]' [-Warray-bounds=]
>  3278 |                         val ^= jhash(&nh->ifindex, sizeof(nh->ifindex), seed);
>       |                                      ^~~~~~~~~~~~
> drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c:2954:33: note: while referencing 'nexthops'
>  2954 |         struct mlxsw_sp_nexthop nexthops[0];
>       |                                 ^~~~~~~~
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Cc: Ido Schimmel <idosch@nvidia.com>
> Cc: Petr Machata <petrm@nvidia.com>
> Cc: "David S. Miller" <davem@davemloft.net>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Jakub Kicinski <kuba@kernel.org>
> Cc: Paolo Abeni <pabeni@redhat.com>
> Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
> Cc: netdev@vger.kernel.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

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

Thanks!
--
Gustavo

> ---
>  drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
> index c22c3ac4e2a1..09e32778b012 100644
> --- a/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
> +++ b/drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c
> @@ -2951,7 +2951,7 @@ struct mlxsw_sp_nexthop_group_info {
>  	   gateway:1, /* routes using the group use a gateway */
>  	   is_resilient:1;
>  	struct list_head list; /* member in nh_res_grp_list */
> -	struct mlxsw_sp_nexthop nexthops[0];
> +	struct mlxsw_sp_nexthop nexthops[];
>  #define nh_rif	nexthops[0].rif
>  };
>  
> -- 
> 2.34.1
>