Re: [PATCH][next] wifi: mt76: mt7996: Use DECLARE_FLEX_ARRAY() and fix -Warray-bounds warnings

From: Kees Cook <keescook@chromium.org>
To: Kalle Valo <kvalo@kernel.org>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>,
	Felix Fietkau <nbd@nbd.name>,
	Lorenzo Bianconi <lorenzo@kernel.org>,
	Ryder Lee <ryder.lee@mediatek.com>,
	Shayne Chen <shayne.chen@mediatek.com>,
	Sean Wang <sean.wang@mediatek.com>,
	Matthias Brugger <matthias.bgg@gmail.com>,
	AngeloGioacchino Del Regno
	<angelogioacchino.delregno@collabora.com>,
	linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH][next] wifi: mt76: mt7996: Use DECLARE_FLEX_ARRAY() and fix -Warray-bounds warnings
Date: Sat, 2 Dec 2023 13:27:54 -0800	[thread overview]
Message-ID: <202312021326.D3504C1@keescook> (raw)
In-Reply-To: <ZVaCNAohuieMmdq9@work>

On Thu, Nov 16, 2023 at 02:57:24PM -0600, Gustavo A. R. Silva wrote:
> Transform zero-length arrays `adm_stat` and `msdu_cnt` into proper
> flexible-array members in anonymous union in `struct
> mt7996_mcu_all_sta_info_event` via the DECLARE_FLEX_ARRAY()
> helper; and fix multiple -Warray-bounds warnings:
> 
> drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:483:61: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
> drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:490:58: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
> drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:492:58: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
> drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:469:61: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
> drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:477:66: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
> drivers/net/wireless/mediatek/mt76/mt7996/mcu.c:479:66: warning: array subscript <unknown> is outside array bounds of 'struct <anonymous>[0]' [-Warray-bounds=]
> 
> This results in no differences in binary output, helps with the ongoing
> efforts to globally enable -Warray-bounds.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

*thread ping*

Can wireless folks please pick this patch up?

-Kees

> ---
>  drivers/net/wireless/mediatek/mt76/mt7996/mcu.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.h b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.h
> index a88f6af323da..9f516f796d63 100644
> --- a/drivers/net/wireless/mediatek/mt76/mt7996/mcu.h
> +++ b/drivers/net/wireless/mediatek/mt76/mt7996/mcu.h
> @@ -163,19 +163,19 @@ struct mt7996_mcu_all_sta_info_event {
>  	u8 rsv3[2];
>  
>  	union {
> -		struct {
> +		DECLARE_FLEX_ARRAY(struct {
>  			__le16 wlan_idx;
>  			u8 rsv[2];
>  			__le32 tx_bytes[IEEE80211_NUM_ACS];
>  			__le32 rx_bytes[IEEE80211_NUM_ACS];
> -		} adm_stat[0];
> +		}, adm_stat);
>  
> -		struct {
> +		DECLARE_FLEX_ARRAY(struct {
>  			__le16 wlan_idx;
>  			u8 rsv[2];
>  			__le32 tx_msdu_cnt;
>  			__le32 rx_msdu_cnt;
> -		} msdu_cnt[0];
> +		}, msdu_cnt);
>  	};
>  } __packed;
>  
> -- 
> 2.34.1
> 

-- 
Kees Cook