From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Mon, 2 Mar 2020 15:04:37 -0600
Subject: net: mlxfw: Replace zero-length array with flexible-array member
Patch-mainline: v5.7-rc1
Git-commit: 30a87f150bd605feca716c056ef9a9ebb1fee1f9
References: jsc#SLE-15172

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 <gustavo@embeddedor.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 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(-)

--- 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_comp_data {
 	struct mlxfw_mfa2_component comp;
-	u8 buff[0];
+	u8 buff[];
 };
 
 static const struct mlxfw_mfa2_tlv_component_descriptor *
--- 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 *