linux-kernel - Re: [PATCH] marvell/mwifiex: replace one-element array with flexible-array member.

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Date:   Tue, 19 Jan 2021 11:15:19 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Jiapeng Zhong <abaci-bugfix@...ux.alibaba.com>
Cc:     amit karwar <amitkarwar@...il.com>,
        Ganapathi Bhat <ganapathi.bhat@....com>,
        Xinming Hu <huxinming820@...il.com>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-wireless <linux-wireless@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] marvell/mwifiex: replace one-element array with
 flexible-array member.

One more thing, for context:

On Tue, Jan 19, 2021 at 11:11 AM Brian Norris <briannorris@...omium.org> wrote:
> On Fri, Jan 15, 2021 at 1:39 AM Jiapeng Zhong
> <abaci-bugfix@...ux.alibaba.com> wrote:
> >
> > Fix the follow coccicheck warnings:
> >
> > ./drivers/net/wireless/marvell/mwifiex/fw.h: WARNING use flexible-array
> > member instead(https://www.kernel.org/doc/html/latest/process/
> > deprecated.html#zero-length-and-one-element-arrays)
> >
> > Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> > Signed-off-by: Jiapeng Zhong <abaci-bugfix@...ux.alibaba.com>
>
> Past experience unfortunately requires me to ask: did you test your
> changes? I understand that's a mostly legit warning, and a good
> deprecation notice, but that doesn't mean this is the right fix. One
> probably should instead audit the usage sites to see if they *are*
> already making proper sizeof (or other) comparisons, and if not, fix
> those first. And if any sites *are* doing correct sizeof computations
> using the existing struct layouts, then you are probably breaking
> them.
>
> Or if you have audited the usage of these structs, it's nice to make a
> small explanation of why this is correct, so I (and other readers)
> don't have to ask these questions :)

FYI, there are others who I believe are making similar blind changes
to this code:

[PATCH 1/1] mwifiex: Fix possible buffer overflows in mwifiex_config_scan
https://lore.kernel.org/linux-wireless/CA+ASDXPkLg2GGFJTt25YO7wae==YAHftf8JXu520pL_vZaT3ug@mail.gmail.com/

For that particular case (the 'ssid' field in
mwifiex_ie_types_wildcard_ssid_params), the previous patch-er was
incorrect, and I believe your change is a better one. But neither of
you provided useful analysis.

Brian