Received-SPF: pass (google.com: domain of linux-wireless+bounces-754-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Date: Wed, 13 Dec 2023 11:11:37 -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 2/6] wifi: ath10k: use flexible arrays for WMI start scan
 TLVs
Message-ID: <202312131111.256FE1A@keescook>
References: <20231213-wmi_host_mem_chunks_flexarray-v1-0-92922d92fa2c@quicinc.com>
 <20231213-wmi_host_mem_chunks_flexarray-v1-2-92922d92fa2c@quicinc.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20231213-wmi_host_mem_chunks_flexarray-v1-2-92922d92fa2c@quicinc.com>

On Wed, Dec 13, 2023 at 09:06:40AM -0800, Jeff Johnson wrote:
> Currently ath10k defines the following struct:
> 	struct wmi_start_scan_tlvs {
> 		u8 tlvs[0];
> 	} __packed;
> 
> Per the guidance in [1] this should be a flexible array. However, a
> direct replace to u8 tlvs[] results in the compilation error:
>        flexible array member in a struct with no named members
> 
> This is because C99 6.7.2.1 (16) requires that a structure containing
> a flexible array member must have more than one named member.
> 
> So rather than defining a separate struct wmi_start_scan_tlvs which
> contains the flexible tlvs[] array, just define the tlvs[] array where
> struct wmi_start_scan_tlvs is being used.
> 
> No functional changes, compile tested only.
> 
> [1] https://docs.kernel.org/process/deprecated.html#zero-length-and-one-element-arrays
> 
> Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>

Yeah, this too looks like the right approach: keeping the flex array
close instead of externalized into a no-op struct.

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

-- 
Kees Cook