linux-kernel - Re: [PATCH] ath6kl: Replace zero-length arrays with DECLARE_FLEX

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Message-ID: <877cqeygca.fsf@kernel.org>
Date:   Tue, 01 Aug 2023 17:42:13 +0300
From:   Kalle Valo <kvalo@...nel.org>
To:     Greg KH <greg@...ah.com>
Cc:     Atul Raut <rauji.raut@...il.com>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ath6kl: Replace zero-length arrays with
 DECLARE_FLEX_ARRAY() helper

Greg KH <greg@...ah.com> writes:

> On Sun, Jul 30, 2023 at 06:29:41PM -0700, Atul Raut wrote:
>
>> Because zero-length arrays are obsolete, replacing them with
>> C99 flexible-array members.
>> Instead of defining a zero-length array, use the new
>> DECLARE_FLEX_ARRAY() auxiliary macro.
>> 
>> This fixes warnings such as:
>> ./drivers/net/wireless/ath/ath6kl/usb.c:109:8-12: WARNING use flexible-array member instead (https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays)
>> 
>> Signed-off-by: Atul Raut <rauji.raut@...il.com>
>> ---
>>  drivers/net/wireless/ath/ath6kl/usb.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/drivers/net/wireless/ath/ath6kl/usb.c b/drivers/net/wireless/ath/ath6kl/usb.c
>> index 5220809841a6..bb3771a3897c 100644
>> --- a/drivers/net/wireless/ath/ath6kl/usb.c
>> +++ b/drivers/net/wireless/ath/ath6kl/usb.c
>> @@ -106,7 +106,7 @@ struct ath6kl_usb_ctrl_diag_cmd_write {
>>  	__le32 cmd;
>>  	__le32 address;
>>  	__le32 value;
>> -	__le32 _pad[1];
>> +	DECLARE_FLEX_ARRAY(__le32, _pad);
>
> This is not a 0 length array, or a variable array.  Look at the work
> done on the hardening mailing list for more details, I think this is
> wrong.

I agree with Greg, this is just padding and _pad is not even used
anywhere in ath6kl. Though use of [1] is strange here, '__le32 _pad;'
would be enough.

-- 
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