netdev - Re: [PATCH v0] ieee802154/adf7242: defer destroy

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Date:   Tue, 23 Aug 2022 10:03:00 +0200
From:   Stefan Schmidt <stefan@...enfreihafen.org>
To:     Lin Ma <linma@....edu.cn>, michael.hennerich@...log.com,
        alex.aring@...il.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, linux-wpan@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v0] ieee802154/adf7242: defer destroy_workqueue call

Hello.

On 08.08.22 05:42, Lin Ma wrote:
> There is a possible race condition (use-after-free) like below
> 
>    (FREE)                     |  (USE)
>    adf7242_remove             |  adf7242_channel
>     cancel_delayed_work_sync  |
>      destroy_workqueue (1)    |   adf7242_cmd_rx
>                               |    mod_delayed_work (2)
>                               |
> 
> The root cause for this race is that the upper layer (ieee802154) is
> unaware of this detaching event and the function adf7242_channel can
> be called without any checks.
> 
> To fix this, we can add a flag write at the beginning of adf7242_remove
> and add flag check in adf7242_channel. Or we can just defer the
> destructive operation like other commit 3e0588c291d6 ("hamradio: defer
> ax25 kfree after unregister_netdev") which let the
> ieee802154_unregister_hw() to handle the synchronization. This patch
> takes the second option.
> 
> Fixes: 58e9683d1475 ("net: ieee802154: adf7242: Fix OCL calibration
> runs")
> Signed-off-by: Lin Ma <linma@....edu.cn>


This patch has been applied to the wpan tree and will be
part of the next pull request to net. Thanks!

regards
Stefan Schmidt