linux-hardening - Re: [PATCH][next] wifi: mt76: mt7996: Use DECLARE_FLEX

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Date: Thu, 16 Nov 2023 13:05:07 -0800
From: Kees Cook <keescook@...omium.org>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Felix Fietkau <nbd@....name>, Lorenzo Bianconi <lorenzo@...nel.org>,
	Ryder Lee <ryder.lee@...iatek.com>,
	Shayne Chen <shayne.chen@...iatek.com>,
	Sean Wang <sean.wang@...iatek.com>, Kalle Valo <kvalo@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] wifi: mt76: mt7996: Use DECLARE_FLEX_ARRAY() and
 fix -Warray-bounds warnings

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@...nel.org>

The syntax looks a little funny initially, but yeah, that's how we need
to fix it for now.

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook