From 53efdc9cb9e6a6f693a81da005280df92b813933 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 19 Mar 2020 18:06:17 -0500 Subject: [PATCH] wl3501_cs: 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. [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 Signed-off-by: Kalle Valo Link: https://lore.kernel.org/r/20200319230617.GA15035@embeddedor.com --- 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 { -- 2.30.2