On 2/16/2026 9:10 PM, Gustavo A. R. Silva wrote:
> -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 <[email protected]>
> ---
> 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;
That bss member appears to be completely unused
(bssid, roam_mode, and params are used)
So IMO the better solution is to remove bss from the union.
And I think struct bss_bias and struct bss_bias_info can also be removed.
/jeff
