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Date: Wed, 13 Dec 2023 11:13:03 -0800
From: Kees Cook <keescook@chromium.org>
To: Jeff Johnson <quic_jjohnson@quicinc.com>
Cc: Kalle Valo <kvalo@kernel.org>,
	"Gustavo A. R. Silva" <gustavo@embeddedor.com>,
	ath10k@lists.infradead.org, linux-wireless@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 5/6] wifi: ath10k: use flexible array in struct
 wmi_tdls_peer_capabilities
Message-ID: <202312131112.F4A76DD3C@keescook>
References: <20231213-wmi_host_mem_chunks_flexarray-v1-0-92922d92fa2c@quicinc.com>
 <20231213-wmi_host_mem_chunks_flexarray-v1-5-92922d92fa2c@quicinc.com>
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In-Reply-To: <20231213-wmi_host_mem_chunks_flexarray-v1-5-92922d92fa2c@quicinc.com>

On Wed, Dec 13, 2023 at 09:06:43AM -0800, Jeff Johnson wrote:
> Currently struct wmi_tdls_peer_capabilities defines:
> 	struct wmi_channel peer_chan_list[1];
> 
> Per the guidance in [1] this should be a flexible array, and at one
> point Gustavo was trying to fix this [2], but had questions about the
> correct behavior when the associated peer_chan_len is 0.
> 
> I have been unable to determine if firmware requires that at least one
> record be present even if peer_chan_len is 0. But since that is the
> current behavior, follow the example from [3] and replace the
> one-element array with a union that contains both a flexible array and
> a single instance of the array element. This results in a struct that
> has the same footprint as the original, so no other driver changes are
> required.
> 
> No functional changes, compile tested only.
> 
> [1] https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays
> [2] https://lore.kernel.org/linux-wireless/626ae2e7-66f8-423b-b17f-e75c1a6d29b3@embeddedor.com/
> [3] https://lore.kernel.org/linux-wireless/202308301529.AC90A9EF98@keescook/
> 
> Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>

Again, good to keep the struct the same size.

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

-- 
Kees Cook