linux-hardening - [PATCH v2][next] wifi: ath6kl: wmi: Avoid -Wflex-array-member-not-at-end warning

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Message-ID: <aZP4RI-uN2001cBh@kspp>
Date: Tue, 17 Feb 2026 14:10:28 +0900
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Jeff Johnson <jeff.johnson@....qualcomm.com>,
	Kalle Valo <quic_kvalo@...cinc.com>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-hardening@...r.kernel.org
Subject: [PATCH v2][next] wifi: ath6kl: wmi: Avoid
 -Wflex-array-member-not-at-end warning

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

struct bss_bias_info is a flexible structure, this is a structure
that contains a flexible-array member (struct bss_bias bss_bias[]).

Since struct roam_ctrl_cmd is defined by hardware, we create the new
struct bss_bias_info_hdr type, and use it to replace the object type
causing trouble in struct roam_ctrl_cmd, namely struct bss_bias_info.

Also, once -fms-extensions is enabled, we can use transparent struct
members in struct bss_bias_info.

Notice that the newly created type does not contain the flex-array
member `bss_bias`, which is the object causing the -Wfamnae warning.

After these changes, the size of struct roam_ctrl_cmd, along
with its member's offsets remain the same, hence the memory layout
doesn't change:

Before changes:
struct roam_ctrl_cmd {
	union {
		u8                 bssid[6];             /*     0     6 */
		u8                 roam_mode;            /*     0     1 */
		struct bss_bias_info bss;            	 /*     0     1 */
		struct low_rssi_scan_params params;      /*     0     8 */
	} info;                                          /*     0     8 */
	u8                         roam_ctrl;            /*     8     1 */

	/* size: 9, cachelines: 1, members: 2 */
	/* last cacheline: 9 bytes */
} __attribute__((__packed__));

After changes:
struct roam_ctrl_cmd {
	union {
		u8                 bssid[6];             /*     0     6 */
		u8                 roam_mode;            /*     0     1 */
		struct bss_bias_info_hdr bss;            /*     0     1 */
		struct low_rssi_scan_params params;      /*     0     8 */
	} info;                                          /*     0     8 */
	u8                         roam_ctrl;            /*     8     1 */

	/* size: 9, cachelines: 1, members: 2 */
	/* last cacheline: 9 bytes */
} __attribute__((__packed__));

With these changes fix the following warning:

drivers/net/wireless/ath/ath6kl/wmi.h:1658:20: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
Changes in v2:
 - Create new separate struct bss_bias_info_hdr, and use
   transparent struct members (in struct bss_bias_info)
   instead of rearranging members in struct roam_ctrl_cmd.
 - Update subject line - Add 'wifi:' prefix.

v1:
 - Link: https://lore.kernel.org/linux-hardening/aR153k4ExCD-QTMq@kspp/

 drivers/net/wireless/ath/ath6kl/wmi.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath6kl/wmi.h b/drivers/net/wireless/ath/ath6kl/wmi.h
index 3080d82e25cc..d2a5c96fc878 100644
--- a/drivers/net/wireless/ath/ath6kl/wmi.h
+++ b/drivers/net/wireless/ath/ath6kl/wmi.h
@@ -1635,8 +1635,12 @@ struct bss_bias {
 	s8 bias;
 } __packed;
 
-struct bss_bias_info {
+struct bss_bias_info_hdr {
 	u8 num_bss;
+} __packed;
+
+struct bss_bias_info {
+	struct bss_bias_info_hdr;
 	struct bss_bias bss_bias[];
 } __packed;
 
@@ -1652,7 +1656,7 @@ struct roam_ctrl_cmd {
 	union {
 		u8 bssid[ETH_ALEN]; /* WMI_FORCE_ROAM */
 		u8 roam_mode; /* WMI_SET_ROAM_MODE */
-		struct bss_bias_info bss; /* WMI_SET_HOST_BIAS */
+		struct bss_bias_info_hdr bss; /* WMI_SET_HOST_BIAS */
 		struct low_rssi_scan_params params; /* WMI_SET_LRSSI_SCAN_PARAMS
 						     */
 	} __packed info;
-- 
2.43.0