Re: [PATCH net v2] atm: fore200e: fix use-after-free in tasklets during device removal

[Jijie Shao]

on 2026/2/6 17:48, Duoming Zhou wrote:
> When the PCA-200E or SBA-200E adapter is being detached, the fore200e
> is deallocated. However, the tx_tasklet or rx_tasklet may still be running
> or pending, leading to use-after-free bug when the already freed fore200e
> is accessed again in fore200e_tx_tasklet() or fore200e_rx_tasklet().
>
> One of the race conditions can occur as follows:
>
> CPU 0 (cleanup)           | CPU 1 (tasklet)
> fore200e_pca_remove_one() | fore200e_interrupt()
>    fore200e_shutdown()     |   tasklet_schedule()
>      kfree(fore200e)       | fore200e_tx_tasklet()
>                            |   fore200e-> // UAF
>
> Fix this by ensuring tx_tasklet or rx_tasklet is properly canceled before
> the fore200e is released. Add tasklet_kill() in fore200e_shutdown() to
> synchronize with any pending or running tasklets. Moreover, since
> fore200e_reset() could prevent further interrupts or data transfers,
> the tasklet_kill() should be placed after fore200e_reset() to prevent
> the tasklet from being rescheduled in fore200e_interrupt().
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Duoming Zhou <duoming@xxxxxxxxxx>
> ---
> Changes in v2:
>    - Move tasklet_kill() after fore200e_reset().
>
>   drivers/atm/fore200e.c | 4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/drivers/atm/fore200e.c b/drivers/atm/fore200e.c
> index f62e3857144..de04c407921 100644
> --- a/drivers/atm/fore200e.c
> +++ b/drivers/atm/fore200e.c
> @@ -362,6 +362,10 @@ fore200e_shutdown(struct fore200e* fore200e)
>       if (fore200e->state > FORE200E_STATE_RESET) {
>   	/* first, reset the board to prevent further interrupts or data transfers */
>   	fore200e_reset(fore200e, 0);
> +#ifdef FORE200E_USE_TASKLET
> +	tasklet_kill(&fore200e->tx_tasklet);
> +	tasklet_kill(&fore200e->rx_tasklet);
> +#endif
>       }

I'm sorry if I gave you a confusing comment.

If (fore200e->state <= FORE200E_STATE_RESET), is there no need to do tasklet_kill()?

Tips: If you need to send v3, please don’t repost your patche within one 24h period:
  https://www.kernel.org/doc/html/next/process/maintainer-netdev.html

  Jijie Shao