linux-hardening - Re: [PATCH v2 2/5] treewide: Replace open-coded flex arrays in unions

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Message-ID: <20210827170837.mu4hql5bev2f5x2o@pengutronix.de>
Date:   Fri, 27 Aug 2021 19:08:37 +0200
From:   Marc Kleine-Budde <mkl@...gutronix.de>
To:     Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Ayush Sawal <ayush.sawal@...lsio.com>,
        Vinay Kumar Yadav <vinay.yadav@...lsio.com>,
        Rohit Maheshwari <rohitm@...lsio.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Kalle Valo <kvalo@...eaurora.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Stanislaw Gruszka <stf_xl@...pl>,
        Luca Coelho <luciano.coelho@...el.com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Johannes Berg <johannes.berg@...el.com>,
        Mordechay Goodstein <mordechay.goodstein@...el.com>,
        Lee Jones <lee.jones@...aro.org>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Arunachalam Santhanam <arunachalam.santhanam@...bosch.com>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        Mikulas Patocka <mikulas@...ax.karlin.mff.cuni.cz>,
        linux-crypto@...r.kernel.org, ath10k@...ts.infradead.org,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-can@...r.kernel.org,
        bpf@...r.kernel.org, Rasmus Villemoes <linux@...musvillemoes.dk>,
        Keith Packard <keithp@...thp.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        clang-built-linux@...glegroups.com, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2 2/5] treewide: Replace open-coded flex arrays in unions

On 27.08.2021 09:08:19, Kees Cook wrote:
> > BTW: Is there opportunity for conversion, too?
> > 
> > | drivers/net/can/peak_canfd/peak_pciefd_main.c:146:32: warning: array of flexible structures
> 
> Oh, hrmpf. This isn't a sane use of flex arrays:
> 
> struct __packed pucan_rx_msg {
> 	...
> 	__le32	can_id;
> 	u8	d[];
> };
> 
> struct pciefd_rx_dma {
>         __le32 irq_status;
>         __le32 sys_time_low;
>         __le32 sys_time_high;
>         struct pucan_rx_msg msg[];
> } __packed __aligned(4);
> 
> I think that needs to be handled separately. How are you building to get
> that warning, by the way? I haven't seen that in my builds...

If compiling with C=1, sparse will complain about this.

regards,
Marc

-- 
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |

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