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

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Message-ID: <202601151627.99DFE54@keescook>
Date: Thu, 15 Jan 2026 16:27:54 -0800
From: Kees Cook <kees@...nel.org>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Jeff Johnson <jeff.johnson@....qualcomm.com>,
	Kalle Valo <quic_kvalo@...cinc.com>, linux-wireless@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] ath6kl: wmi: Avoid -Wflex-array-member-not-at-end
 warning

On Wed, Nov 19, 2025 at 05:03:42PM +0900, 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.
> 
> Move the conflicting declaration (which happens to be in a union, so
> we're moving the entire union) to the end of the corresponding
> structure. Notice that `struct bss_bias_info` is a flexible structure,
> this is a structure that contains a flexible-array member.
> 
> 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>
> ---
>  drivers/net/wireless/ath/ath6kl/wmi.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/ath/ath6kl/wmi.h b/drivers/net/wireless/ath/ath6kl/wmi.h
> index 3080d82e25cc..0e7810b9372f 100644
> --- a/drivers/net/wireless/ath/ath6kl/wmi.h
> +++ b/drivers/net/wireless/ath/ath6kl/wmi.h
> @@ -1649,6 +1649,9 @@ struct low_rssi_scan_params {
>  } __packed;
>  
>  struct roam_ctrl_cmd {
> +	u8 roam_ctrl;
> +
> +	/* Must be last as it ends in a flexible-array member. */
>  	union {
>  		u8 bssid[ETH_ALEN]; /* WMI_FORCE_ROAM */
>  		u8 roam_mode; /* WMI_SET_ROAM_MODE */
> @@ -1656,7 +1659,6 @@ struct roam_ctrl_cmd {
>  		struct low_rssi_scan_params params; /* WMI_SET_LRSSI_SCAN_PARAMS
>  						     */
>  	} __packed info;
> -	u8 roam_ctrl;
>  } __packed;

It looks like this is a hardware interface, so I don't think roam_ctrl
can be moved like that. See ath6kl_wmi_set_roam_lrssi_cmd().

-Kees

-- 
Kees Cook