netdev - Re: [PATCH][next] mwifiex: usb: Replace one-element array with flexible-array member

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Message-ID: <CA+ASDXO+GbP_WWVdO0=Uavh036ZhZiziE8DwGRKP-ooofd2QVw@mail.gmail.com>
Date:   Mon, 9 Aug 2021 14:24:07 -0700
From:   Brian Norris <briannorris@...omium.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Amitkumar Karwar <amitkarwar@...il.com>,
        Ganapathi Bhat <ganapathi017@...il.com>,
        Sharvari Harisangam <sharvari.harisangam@....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>,
        "<netdev@...r.kernel.org>" <netdev@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] mwifiex: usb: Replace one-element array with
 flexible-array member

On Mon, Aug 9, 2021 at 2:08 PM Gustavo A. R. Silva
<gustavoars@...nel.org> wrote:
>
> There is a regular need in the kernel to provide a way to declare having
> a dynamically sized set of trailing elements in a structure. Kernel code
> should always use “flexible array members”[1] for these cases. The older
> style of one-element or zero-length arrays should no longer be used[2].
>
> This helps with the ongoing efforts to globally enable -Warray-bounds
> and get us closer to being able to tighten the FORTIFY_SOURCE routines
> on memcpy().
>
> This issue was found with the help of Coccinelle and audited and fixed,
> manually.
>
> [1] https://en.wikipedia.org/wiki/Flexible_array_member
> [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays
>
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/109
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

An important part of your patch rationale should include determining
that the 1-length wasn't actually important anywhere. I double checked
for you, and nobody seemed to be relying on 'sizeof struct fw_data' at
all, so this should be OK:

Reviewed-by: Brian Norris <briannorris@...omium.org>