From b0c40588161dafdafdbac537b4441be02c15aff2 Mon Sep 17 00:00:00 2001
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Thu, 19 Mar 2020 17:51:33 -0500
Subject: [PATCH] atmel: at76c50x: Replace zero-length array with flexible-array member
Git-commit: b0c40588161dafdafdbac537b4441be02c15aff2
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/20200319225133.GA29672@embeddedor.com
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/net/wireless/atmel/at76c50x-usb.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/wireless/atmel/at76c50x-usb.h b/drivers/net/wireless/atmel/at76c50x-usb.h
index f56863403b05..746e64dfd8aa 100644
--- a/drivers/net/wireless/atmel/at76c50x-usb.h
+++ b/drivers/net/wireless/atmel/at76c50x-usb.h
@@ -151,7 +151,7 @@ struct at76_command {
u8 cmd;
u8 reserved;
__le16 size;
- u8 data[0];
+ u8 data[];
} __packed;
/* Length of Atmel-specific Rx header before 802.11 frame */
--
2.16.4