From 53efdc9cb9e6a6f693a81da005280df92b813933 Mon Sep 17 00:00:00 2001
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Thu, 19 Mar 2020 18:06:17 -0500
Subject: [PATCH] wl3501_cs: Replace zero-length array with flexible-array member
Git-commit: 53efdc9cb9e6a6f693a81da005280df92b813933
Patch-mainline: v5.7-rc1
References: jsc#SLE-13430

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>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200319230617.GA15035@embeddedor.com
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/net/wireless/wl3501.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wireless/wl3501.h b/drivers/net/wireless/wl3501.h
index efdce9ae36ea..b446cb369557 100644
--- a/drivers/net/wireless/wl3501.h
+++ b/drivers/net/wireless/wl3501.h
@@ -231,7 +231,7 @@ struct iw_mgmt_info_element {
 	u8 id; /* one of enum iw_mgmt_info_element_ids,
 		  but sizeof(enum) > sizeof(u8) :-( */
 	u8 len;
-	u8 data[0];
+	u8 data[];
 } __packed;
 
 struct iw_mgmt_essid_pset {
-- 
2.16.4