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

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Date:   Sun, 23 Jan 2022 16:48:19 +0300
From:   Pavel Skripkin <paskripkin@...il.com>
To:     Dongliang Mu <mudongliangabcd@...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

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 :)




With regards,
Pavel Skripkin