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

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Message-ID: <b68a6d51-a416-4252-848e-0f3a8a3216bd@huawei.com>
Date: Fri, 6 Feb 2026 11:48:49 +0800
From: Jijie Shao <shaojijie@...wei.com>
To: Duoming Zhou <duoming@....edu.cn>, <netdev@...r.kernel.org>
CC: <shaojijie@...wei.com>, <linux-atm-general@...ts.sourceforge.net>,
	<linux-kernel@...r.kernel.org>, <3chas3@...il.com>
Subject: Re: [PATCH net] atm: fore200e: fix use-after-free in tasklets during
 device removal


on 2026/2/5 11:03, Duoming Zhou wrote:
> When the PCA-200E or SBA-200E adapters 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.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Duoming Zhou <duoming@....edu.cn>
> ---
>   drivers/atm/fore200e.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/atm/fore200e.c b/drivers/atm/fore200e.c
> index f62e3857144..7470daf9469 100644
> --- a/drivers/atm/fore200e.c
> +++ b/drivers/atm/fore200e.c
> @@ -358,7 +358,12 @@ fore200e_shutdown(struct fore200e* fore200e)
>       printk(FORE200E "removing device %s at 0x%lx, IRQ %s\n",
>   	   fore200e->name, fore200e->phys_base,
>   	   fore200e_irq_itoa(fore200e->irq));
> -
> +
> +#ifdef FORE200E_USE_TASKLET
> +	tasklet_kill(&fore200e->tx_tasklet);
> +	tasklet_kill(&fore200e->rx_tasklet);
> +#endif
> +
>       if (fore200e->state > FORE200E_STATE_RESET) {
>   	/* first, reset the board to prevent further interrupts or data transfers */
>   	fore200e_reset(fore200e, 0);

Hi,

I personally think that tasklet_kill() should be moved here.
According to the code comments, there will be no data transfers or interrupts after fore200e_reset(),
otherwise fore200e->tx_tasklet may be rescheduled again in fore200e_interrupt().

Jijie Shao