[next] wifi: rtw89: coex: Fix __write_overflow_field error

  One-element arrays as fake flexible arrays are deprecated, and we are
moving towards adopting C99 flexible-array members instead.

Fix the following error seen under GCC-13 and -fstrict-flex-arrays=3:
In function ‘fortify_memcpy_chk’,
    inlined from ‘_append_tdma’ at drivers/net/wireless/realtek/rtw89/coex.c:1579:3:
include/linux/fortify-string.h:583:25: error: call to ‘__write_overflow_field’ declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror=attribute-warning]
  583 |                         __write_overflow_field(p_size_field, size);
      |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
routines on memcpy() and help us make progress towards globally
enabling -fstrict-flex-arrays=3 [1].

This results in no differences in binary output.

Link: https://github.com/KSPP/linux/issues/21
Link: https://github.com/KSPP/linux/issues/299
Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 drivers/net/wireless/realtek/rtw89/coex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
  

> -----Original Message-----
> From: Gustavo A. R. Silva <gustavoars@kernel.org>
> Sent: Wednesday, May 24, 2023 10:13 AM
> To: Ping-Ke Shih <pkshih@realtek.com>; Kalle Valo <kvalo@kernel.org>
> Cc: linux-wireless@vger.kernel.org; linux-kernel@vger.kernel.org; Gustavo A. R. Silva
> <gustavoars@kernel.org>; linux-hardening@vger.kernel.org
> Subject: [PATCH][next] wifi: rtw89: coex: Fix __write_overflow_field error
> 
> One-element arrays as fake flexible arrays are deprecated, and we are
> moving towards adopting C99 flexible-array members instead.
> 
> Fix the following error seen under GCC-13 and -fstrict-flex-arrays=3:
> In function ‘fortify_memcpy_chk’,
>     inlined from ‘_append_tdma’ at drivers/net/wireless/realtek/rtw89/coex.c:1579:3:
> include/linux/fortify-string.h:583:25: error: call to ‘__write_overflow_field’ declared with attribute
> warning: detected write beyond size of field (1st parameter); maybe use struct_group()?
> [-Werror=attribute-warning]
>   583 |                         __write_overflow_field(p_size_field, size);
>       |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
> routines on memcpy() and help us make progress towards globally
> enabling -fstrict-flex-arrays=3 [1].
> 
> This results in no differences in binary output.
> 
> Link: https://github.com/KSPP/linux/issues/21
> Link: https://github.com/KSPP/linux/issues/299
> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> ---
>  drivers/net/wireless/realtek/rtw89/coex.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/realtek/rtw89/coex.c b/drivers/net/wireless/realtek/rtw89/coex.c
> index 3a586a971e8f..bda0e1e99a8c 100644
> --- a/drivers/net/wireless/realtek/rtw89/coex.c
> +++ b/drivers/net/wireless/realtek/rtw89/coex.c
> @@ -206,7 +206,7 @@ static const struct rtw89_btc_ver rtw89_btc_ver_defs[] = {
>  struct rtw89_btc_btf_tlv {
>         u8 type;
>         u8 len;
> -       u8 val[1];
> +       u8 val[];
>  } __packed;
> 
>  enum btc_btf_set_report_en {

Arnd has sent the same patch [1] as yours. 

[1] https://lore.kernel.org/linux-wireless/27a7010de8be4006a3e4b95e851781c6@realtek.com/T/#mca619c8261b87b88eedd391ceafb34c40d513ce5
  

On 5/23/23 20:21, Ping-Ke Shih wrote:
> 
> 
>> -----Original Message-----
>> From: Gustavo A. R. Silva <gustavoars@kernel.org>
>> Sent: Wednesday, May 24, 2023 10:13 AM
>> To: Ping-Ke Shih <pkshih@realtek.com>; Kalle Valo <kvalo@kernel.org>
>> Cc: linux-wireless@vger.kernel.org; linux-kernel@vger.kernel.org; Gustavo A. R. Silva
>> <gustavoars@kernel.org>; linux-hardening@vger.kernel.org
>> Subject: [PATCH][next] wifi: rtw89: coex: Fix __write_overflow_field error
>>
>> One-element arrays as fake flexible arrays are deprecated, and we are
>> moving towards adopting C99 flexible-array members instead.
>>
>> Fix the following error seen under GCC-13 and -fstrict-flex-arrays=3:
>> In function ‘fortify_memcpy_chk’,
>>      inlined from ‘_append_tdma’ at drivers/net/wireless/realtek/rtw89/coex.c:1579:3:
>> include/linux/fortify-string.h:583:25: error: call to ‘__write_overflow_field’ declared with attribute
>> warning: detected write beyond size of field (1st parameter); maybe use struct_group()?
>> [-Werror=attribute-warning]
>>    583 |                         __write_overflow_field(p_size_field, size);
>>        |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> This helps with the ongoing efforts to tighten the FORTIFY_SOURCE
>> routines on memcpy() and help us make progress towards globally
>> enabling -fstrict-flex-arrays=3 [1].
>>
>> This results in no differences in binary output.
>>
>> Link: https://github.com/KSPP/linux/issues/21
>> Link: https://github.com/KSPP/linux/issues/299
>> Link: https://gcc.gnu.org/pipermail/gcc-patches/2022-October/602902.html [1]
>> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
>> ---
>>   drivers/net/wireless/realtek/rtw89/coex.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/wireless/realtek/rtw89/coex.c b/drivers/net/wireless/realtek/rtw89/coex.c
>> index 3a586a971e8f..bda0e1e99a8c 100644
>> --- a/drivers/net/wireless/realtek/rtw89/coex.c
>> +++ b/drivers/net/wireless/realtek/rtw89/coex.c
>> @@ -206,7 +206,7 @@ static const struct rtw89_btc_ver rtw89_btc_ver_defs[] = {
>>   struct rtw89_btc_btf_tlv {
>>          u8 type;
>>          u8 len;
>> -       u8 val[1];
>> +       u8 val[];
>>   } __packed;
>>
>>   enum btc_btf_set_report_en {
> 
> Arnd has sent the same patch [1] as yours.

Oh that's great! What a coincidence. :)

Thanks for letting me know.
--
Gustavo

> 
> [1] https://lore.kernel.org/linux-wireless/27a7010de8be4006a3e4b95e851781c6@realtek.com/T/#mca619c8261b87b88eedd391ceafb34c40d513ce5
>