ath6kl: Replace zero-length arrays with DECLARE_FLEX_ARRAY() helper

[PATCH] ath6kl: Replace zero-length arrays with DECLARE_FLEX_ARRAY() helper

Posted by Atul Raut 2 years, 6 months ago

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@gmail.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);
 } __packed;
 
 struct ath6kl_usb_ctrl_diag_cmd_read {
-- 
2.34.1

Re: [PATCH] ath6kl: Replace zero-length arrays with DECLARE_FLEX_ARRAY() helper

Posted by Greg KH 2 years, 6 months ago

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@gmail.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.

good luck!

greg k-h

Re: [PATCH] ath6kl: Replace zero-length arrays with DECLARE_FLEX_ARRAY() helper

Posted by Kalle Valo 2 years, 6 months ago

Greg KH <greg@kroah.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@gmail.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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