linux-hardening - Re: [PATCH v3] ethtool: Replace 0-length array with flexible array

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Message-ID: <202301052224.D2569E38@keescook>
Date:   Thu, 5 Jan 2023 22:25:31 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Vincent MAILHOL <mailhol.vincent@...adoo.fr>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        kernel test robot <lkp@...el.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Sean Anderson <sean.anderson@...o.com>,
        Alexandru Tachici <alexandru.tachici@...log.com>,
        Amit Cohen <amcohen@...dia.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3] ethtool: Replace 0-length array with flexible array

On Fri, Jan 06, 2023 at 02:47:35PM +0900, Vincent MAILHOL wrote:
> On Fri. 6 Jan 2023 at 13:28, Kees Cook <keescook@...omium.org> wrote:
> > Zero-length arrays are deprecated[1]. Replace struct ethtool_rxnfc's
> > "rule_locs" 0-length array with a flexible array. Detected with GCC 13,
> > using -fstrict-flex-arrays=3:
> >
> > net/ethtool/common.c: In function 'ethtool_get_max_rxnfc_channel':
> > net/ethtool/common.c:558:55: warning: array subscript i is outside array bounds of '__u32[0]' {aka 'unsigned int[]'} [-Warray-bounds=]
> >   558 |                         .fs.location = info->rule_locs[i],
> >       |                                        ~~~~~~~~~~~~~~~^~~
> > In file included from include/linux/ethtool.h:19,
> >                  from include/uapi/linux/ethtool_netlink.h:12,
> >                  from include/linux/ethtool_netlink.h:6,
> >                  from net/ethtool/common.c:3:
> > include/uapi/linux/ethtool.h:1186:41: note: while referencing
> > 'rule_locs'
> >  1186 |         __u32                           rule_locs[0];
> >       |                                         ^~~~~~~~~
> >
> > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays
> >
> > Cc: "David S. Miller" <davem@...emloft.net>
> > Cc: Jakub Kicinski <kuba@...nel.org>
> > Cc: Andrew Lunn <andrew@...n.ch>
> > Cc: kernel test robot <lkp@...el.com>
> > Cc: Oleksij Rempel <linux@...pel-privat.de>
> > Cc: Sean Anderson <sean.anderson@...o.com>
> > Cc: Alexandru Tachici <alexandru.tachici@...log.com>
> > Cc: Amit Cohen <amcohen@...dia.com>
> > Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
> > Cc: Vincent Mailhol <mailhol.vincent@...adoo.fr>
> > Cc: netdev@...r.kernel.org
> > Signed-off-by: Kees Cook <keescook@...omium.org>
> > ---
> > v3: don't use helper (vincent)
> 
> v1: https://lore.kernel.org/all/20230105214126.never.757-kees@kernel.org
>                                                ^^^^^
> > v2: https://lore.kernel.org/lkml/20230105233420.gonna.036-kees@kernel.org
>                                                   ^^^^^
> v3: https://lore.kernel.org/netdev/20230106042844.give.885-kees@kernel.org
>                                                   ^^^^
> 
> Seriously... :)

Hurray! Someone noticed and it's not even April yet. :) *celebrate*

-Kees

-- 
Kees Cook