[lkml]   [2020]   [Mar]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Patch in this message
Subject[PATCH][next] 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.

[3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <>
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 *
 \ /
  Last update: 2020-03-02 22:02    [W:0.067 / U:29.152 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site