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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
To:     Dmitry Antipov <dmantipov@yandex.ru>
Cc:     Kalle Valo <kvalo@kernel.org>, linux-wireless@vger.kernel.org,
        Dmitry Antipov <dmantipov@yandex.ru>,
        Johannes Berg <johannes@sipsolutions.net>
Subject: Re: [PATCH 2/2] [v2] wifi: ath9k: fix fortify warnings
In-Reply-To: <20230620080855.396851-2-dmantipov@yandex.ru>
References: <20230620080855.396851-1-dmantipov@yandex.ru>
 <20230620080855.396851-2-dmantipov@yandex.ru>
Date:   Tue, 20 Jun 2023 14:05:31 +0200
Message-ID: <877crye3uc.fsf@toke.dk>
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Dmitry Antipov <dmantipov@yandex.ru> writes:

> When compiling with gcc 13.1 and CONFIG_FORTIFY_SOURCE=3Dy,
> I've noticed the following:
>
> In function =E2=80=98fortify_memcpy_chk=E2=80=99,
>     inlined from =E2=80=98ath_tx_complete_aggr=E2=80=99 at drivers/net/wi=
reless/ath/ath9k/xmit.c:556:4,
>     inlined from =E2=80=98ath_tx_process_buffer=E2=80=99 at drivers/net/w=
ireless/ath/ath9k/xmit.c:773:3:
> ./include/linux/fortify-string.h:529:25: warning: call to =E2=80=98__read=
_overflow2_field=E2=80=99
> declared with attribute warning: detected read beyond size of field (2nd =
parameter);
> maybe use struct_group()? [-Wattribute-warning]
>   529 |                         __read_overflow2_field(q_size_field, size=
);
>       |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> In function =E2=80=98fortify_memcpy_chk=E2=80=99,
>     inlined from =E2=80=98ath_tx_count_frames=E2=80=99 at drivers/net/wir=
eless/ath/ath9k/xmit.c:473:3,
>     inlined from =E2=80=98ath_tx_complete_aggr=E2=80=99 at drivers/net/wi=
reless/ath/ath9k/xmit.c:572:2,
>     inlined from =E2=80=98ath_tx_process_buffer=E2=80=99 at drivers/net/w=
ireless/ath/ath9k/xmit.c:773:3:
> ./include/linux/fortify-string.h:529:25: warning: call to =E2=80=98__read=
_overflow2_field=E2=80=99
> declared with attribute warning: detected read beyond size of field (2nd =
parameter);
> maybe use struct_group()? [-Wattribute-warning]
>   529 |                         __read_overflow2_field(q_size_field, size=
);
>       |                         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> In both cases, the compiler complains on:
>
> memcpy(ba, &ts->ba_low, WME_BA_BMP_SIZE >> 3);
>
> which is the legal way to copy both 'ba_low' and following 'ba_high'
> members of 'struct ath_tx_status' at once (that is, issue one 8-byte
> 'memcpy()' for two 4-byte fields). Since the fortification logic seems
> interprets this trick as an attempt to overread 4-byte 'ba_low', silence
> relevant warnings by using the convenient 'struct_group()' quirk.
>
> Suggested-by: Johannes Berg <johannes@sipsolutions.net>
> Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>

Acked-by: Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk>