linux-kernel - Re: [PATCH 5/6] wifi: ath10k: use flexible array in struct wmi_tdls_peer

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Message-ID: <a015d185-ece0-4608-821d-061d1296d4e7@embeddedor.com>
Date:   Wed, 13 Dec 2023 14:19:43 -0600
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Jeff Johnson <quic_jjohnson@...cinc.com>,
        Kalle Valo <kvalo@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>, ath10k@...ts.infradead.org,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] wifi: ath10k: use flexible array in struct
 wmi_tdls_peer_capabilities



On 12/13/23 11:06, 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@...cinc.com>

Reviewed-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Thanks!
--
Gustavo

> ---
>   drivers/net/wireless/ath/ath10k/wmi.h | 8 +++++++-
>   1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/ath/ath10k/wmi.h b/drivers/net/wireless/ath/ath10k/wmi.h
> index e16410e348ca..b64b6e214bae 100644
> --- a/drivers/net/wireless/ath/ath10k/wmi.h
> +++ b/drivers/net/wireless/ath/ath10k/wmi.h
> @@ -7162,7 +7162,13 @@ struct wmi_tdls_peer_capabilities {
>   	__le32 is_peer_responder;
>   	__le32 pref_offchan_num;
>   	__le32 pref_offchan_bw;
> -	struct wmi_channel peer_chan_list[1];
> +	union {
> +		/* to match legacy implementation allocate room for
> +		 * at least one record even if peer_chan_len is 0
> +		 */
> +		struct wmi_channel peer_chan_min_allocation;
> +		DECLARE_FLEX_ARRAY(struct wmi_channel, peer_chan_list);
> +	};
>   } __packed;
>   
>   struct wmi_10_4_tdls_peer_update_cmd {
>