linux-hardening - Re: [PATCH 2/2] wifi: ath9k: work around memset overflow warning

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Message-ID: <87wmpm12ka.fsf@toke.dk>
Date: Thu, 28 Mar 2024 22:14:45 +0100
From: Toke Høiland-Jørgensen <toke@...e.dk>
To: Arnd Bergmann <arnd@...nel.org>, Kees Cook <keescook@...omium.org>,
 Kalle Valo <kvalo@...nel.org>
Cc: linux-hardening@...r.kernel.org, linux-wireless@...r.kernel.org, Arnd
 Bergmann <arnd@...db.de>, Jeff Johnson <quic_jjohnson@...cinc.com>, Dmitry
 Antipov <dmantipov@...dex.ru>, Hancheng Yang <hyang@...ebox.fr>, Remi
 Pommarel <repk@...plefau.lt>, Johannes Berg <johannes.berg@...el.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] wifi: ath9k: work around memset overflow warning

Arnd Bergmann <arnd@...nel.org> writes:

> From: Arnd Bergmann <arnd@...db.de>
>
> gcc-9 and some other older versions produce a false-positive warning
> for zeroing two fields
>
> In file included from include/linux/string.h:369,
>                  from drivers/net/wireless/ath/ath9k/main.c:18:
> In function 'fortify_memset_chk',
>     inlined from 'ath9k_ps_wakeup' at drivers/net/wireless/ath/ath9k/main.c:140:3:
> include/linux/fortify-string.h:462:25: 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]
>   462 |                         __write_overflow_field(p_size_field, size);
>       |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Using a struct_group seems to reliably avoid the warning and
> not make the code much uglier. The combined memset() should even
> save a couple of cpu cycles.
>
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Acked-by: Toke Høiland-Jørgensen <toke@...e.dk>