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

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Message-Id: <20230105223642.never.980-kees@kernel.org>
Date:   Thu,  5 Jan 2023 14:36:43 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Saeed Mahameed <saeedm@...dia.com>
Cc:     Kees Cook <keescook@...omium.org>,
        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>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        netdev@...r.kernel.org, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] net/mlx5e: Replace 0-length array with flexible array

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>
---
 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