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

[Jakub Kicinski]

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@xxxxxxxxxx>

The driver has been removed. No point.