Re: [PATCH net v3] atm: fore200e: fix use-after-free in tasklets during device removal

[Jijie Shao <shaojijie@huawei.com>]

on 2026/2/9 17:45, 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(). Finally,
> it only needs to do tasklet_kill() when the fore200e state is greater
> than or equal to FORE200E_STATE_IRQ, since tasklets are uninitialized
> in earlier states.
>
> This bug was identified through static analysis.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable@kernel.org
> Suggested-by: Jijie Shao <shaojijie@huawei.com>
> Signed-off-by: Duoming Zhou <duoming@zju.edu.cn>
> ---
> Changes in v3:
>    - Only do tasklet_kill() when state >= FORE200E_STATE_IRQ.
>    - Make the commit messages clearer.
>
>   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..eb386ec6b5e 100644
> --- a/drivers/atm/fore200e.c
> +++ b/drivers/atm/fore200e.c
> @@ -363,7 +363,12 @@ fore200e_shutdown(struct fore200e* fore200e)
>   	/* first, reset the board to prevent further interrupts or data transfers */
>   	fore200e_reset(fore200e, 0);
>       }
> -
> +#ifdef FORE200E_USE_TASKLET
> +	if (fore200e->state >= FORE200E_STATE_IRQ) {
> +		tasklet_kill(&fore200e->tx_tasklet);
> +		tasklet_kill(&fore200e->rx_tasklet);
> +	}
> +#endif

The code appears to be misaligned.
I see that in the original driver code, the first level of indentation uses 4 spaces,
and the second level uses a TAB (8-character width).
In your code, the first level uses a TAB, and the second level uses two TABs.
Of course, your code complies with the current coding standards.

Additionally, I think a better modification would be to do tasklet_kill()
in the "switch(fore200e->state)-case FORE200E_STATE_IRQ" branch,
because "fore200e->tx_tasklet" is initialized together with "fore200e->irq".

Of course, your current change also looks fine, so
Reviewed-by: Jijie Shao <shaojijie@huawei.com>