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Date:   Tue, 11 Feb 2020 15:08:22 -0600
From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To:     Tomas Winkler <tomas.winkler@intel.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org,
        "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] mei: bus: replace zero-length array with flexible-array
 member
Message-ID: <20200211210822.GA31368@embeddedor>
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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
inadvertenly introduced[3] to the codebase from now on.

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>
---
 drivers/misc/mei/bus-fixup.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/mei/bus-fixup.c b/drivers/misc/mei/bus-fixup.c
index 5fcac02233af..aa3648d59a8a 100644
--- a/drivers/misc/mei/bus-fixup.c
+++ b/drivers/misc/mei/bus-fixup.c
@@ -107,7 +107,7 @@ struct mkhi_rule_id {
 struct mkhi_fwcaps {
 	struct mkhi_rule_id id;
 	u8 len;
-	u8 data[0];
+	u8 data[];
 } __packed;
 
 struct mkhi_fw_ver_block {
@@ -135,7 +135,7 @@ struct mkhi_msg_hdr {
 
 struct mkhi_msg {
 	struct mkhi_msg_hdr hdr;
-	u8 data[0];
+	u8 data[];
 } __packed;
 
 #define MKHI_OSVER_BUF_LEN (sizeof(struct mkhi_msg_hdr) + \
-- 
2.25.0