linux-kernel - Re: [PATCH] drivers: net: remove a dangling pointer in peak_usb_create

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Date:   Mon, 24 Jan 2022 14:04:38 +0800
From:   Dongliang Mu <mudongliangabcd@...il.com>
To:     Pavel Skripkin <paskripkin@...il.com>
Cc:     Dongliang Mu <dzm91@...t.edu.cn>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Stephane Grosjean <s.grosjean@...k-system.com>,
        Stefan Mätje <stefan.maetje@....eu>,
        Vincent Mailhol <mailhol.vincent@...adoo.fr>,
        linux-can@...r.kernel.org,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drivers: net: remove a dangling pointer in peak_usb_create_dev

On Sun, Jan 23, 2022 at 9:48 PM Pavel Skripkin <paskripkin@...il.com> wrote:
>
> Hi Dongliang,
>
> On 1/22/22 09:45, Dongliang Mu wrote:
> [...]
>
> >> Yeah, it seems like (at least based on code), that this dangling pointer
> >> is not dangerous, since nothing accesses it. And next_siblings
> >> _guaranteed_ to be NULL, since dev->next_siblings is set NULL in
> >> disconnect()
> >
> > Yes, you're right. As a security researcher, I am sensitive to such
> > dangling pointers.
> >
> > As its nullifying site is across functions, I suggest developers
> > remove this dangling pointer in case that any newly added code in this
> > function or before the nullifying location would touch next_siblings.
> >
>
> Based on git blame this driver is very old (was added in 2012), so, I
> guess, nothing really new will come up.
>
> Anyway, I am absolutely not a security person and if you think, that
> this dangling pointer can be somehow used in exploitation you should
> state it in commit message.
>
>
> > If Pavel and others think it's fine, then it's time to close this patch.
> >
>
> I don't have any big objections on the code itself. Maybe only 'if' can
> be removed to just speed up the code, but I don't see why this change is
> needed :)

OK, let's move on. Leave alone this patch.

>
>
>
>
> With regards,
> Pavel Skripkin