linux-kernel - Re: [PATCH net] ethernet: ixgb: fix use after free bugs caused by circular dependency problem

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Date:   Thu, 20 Apr 2023 07:36:19 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Duoming Zhou <duoming@....edu.cn>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com,
        davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
        intel-wired-lan@...ts.osuosl.org
Subject: Re: [PATCH net] ethernet: ixgb: fix use after free bugs caused by
 circular dependency problem

On Thu, 20 Apr 2023 22:01:57 +0800 Duoming Zhou wrote:
> The watchdog_timer can schedule tx_timeout_task and tx_timeout_task
> can also arm watchdog_timer. The process is shown below:
> 
> ----------- timer schedules work ------------
> ixgb_watchdog() //timer handler
>   schedule_work(&adapter->tx_timeout_task)
> 
> ----------- work arms timer ------------
> ixgb_tx_timeout_task() //workqueue callback function
>   ixgb_up()
>     mod_timer(&adapter->watchdog_timer,...)
> 
> When ixgb device is detaching, the timer and workqueue
> could still be rearmed. The process is shown below:
> 
>   (cleanup routine)           |  (timer and workqueue routine)
> ixgb_remove()                 |
>                               | ixgb_tx_timeout_task() //workqueue
>                               |   ixgb_up()
>                               |     mod_timer()
>   cancel_work_sync()          |
>   free_netdev(netdev) //FREE  | ixgb_watchdog() //timer
>                               |   netif_carrier_ok(netdev) //USE
> 
> This patch adds timer_shutdown_sync() in ixgb_remove(), which
> could prevent rearming of the timer from the workqueue.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Duoming Zhou <duoming@....edu.cn>

The driver has been removed. No point.