linux-kernel - Re: [PATCH 11/20] ethernet: ucc_geth: fix use-after-free in ucc_geth

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Message-ID: <15915cb7-45bb-f62a-e603-0250053b7aeb@prevas.dk>
Date:   Sat, 5 Dec 2020 22:35:18 +0100
From:   Rasmus Villemoes <rasmus.villemoes@...vas.dk>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Li Yang <leoyang.li@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Zhao Qiang <qiang.zhao@....com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/20] ethernet: ucc_geth: fix use-after-free in
 ucc_geth_remove()

On 05/12/2020 22.19, Jakub Kicinski wrote:
> On Sat, 5 Dec 2020 22:04:28 +0100 Rasmus Villemoes wrote:
>> On 05/12/2020 21.48, Jakub Kicinski wrote:
>>> On Sat,  5 Dec 2020 20:17:34 +0100 Rasmus Villemoes wrote:  
>>>> -	unregister_netdev(dev);
>>>> -	free_netdev(dev);
>>>>  	ucc_geth_memclean(ugeth);
>>>>  	if (of_phy_is_fixed_link(np))
>>>>  		of_phy_deregister_fixed_link(np);
>>>>  	of_node_put(ugeth->ug_info->tbi_node);
>>>>  	of_node_put(ugeth->ug_info->phy_node);
>>>> +	unregister_netdev(dev);
>>>> +	free_netdev(dev);  
>>>
>>> Are you sure you want to move the unregister_netdev() as well as the
>>> free?
>>
>> Hm, dunno, I don't think it's needed per se, but it also shouldn't hurt
>> from what I can tell. It seems more natural that they go together, but
>> if you prefer a minimal patch that's of course also possible.
> 
> I was concerned about the fact that we free things and release
> references while the device may still be up (given that it's
> unregister_netdev() that will take it down).

I guess you're right. I'll fix it locally (and pull the patch earlier)
and wait a few days with sending an updated version to give Li Yang some
time to say if he wants to handle the series or not.

Thanks,
Rasmus