From 30a87f150bd605feca716c056ef9a9ebb1fee1f9 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 2 Mar 2020 15:04:37 -0600 Subject: [PATCH] net: mlxfw: Replace zero-length array with flexible-array member The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Reviewed-by: Jiri Pirko Signed-off-by: David S. Miller --- drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2.c | 2 +- drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv.h | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2.c b/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2.c index 79057af4fe99..5d9ddf36fb4e 100644 --- a/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2.c +++ b/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2.c @@ -496,7 +496,7 @@ mlxfw_mfa2_file_component_tlv_get(const struct mlxfw_mfa2_file *mfa2_file, struct mlxfw_mfa2_comp_data { struct mlxfw_mfa2_component comp; - u8 buff[0]; + u8 buff[]; }; static const struct mlxfw_mfa2_tlv_component_descriptor * diff --git a/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv.h b/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv.h index 33c971190bba..2014a5de5a01 100644 --- a/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv.h +++ b/drivers/net/ethernet/mellanox/mlxfw/mlxfw_mfa2_tlv.h @@ -11,7 +11,7 @@ struct mlxfw_mfa2_tlv { u8 version; u8 type; __be16 len; - u8 data[0]; + u8 data[]; } __packed; static inline const struct mlxfw_mfa2_tlv * -- 2.30.2