Re: [PATCH] iio: adc: at91-sama5d2_adc: Fix use-after-free in sama5d2_adc driver

[Eugen Hristev <eugen.hristev@linaro.org>]

Hello,

On 11/28/24 08:45, Pei Xiao wrote:
> at91_adc_interrupt can call at91_adc_touch_data_handler function
> to start the work by schedule_work(&st->touch_st.workq).
> 
> If we remove the module which will call at91_adc_remove to
> make cleanup, it will free indio_dev through iio_device_unregister
> while the work mentioned above will be used. The sequence of operations
> that may lead to a UAF bug is as follows:
> 
> CPU0                                      CPU1
> 
>                                      | at91_adc_workq_handler
> at91_adc_remove                      |
> iio_device_unregister(indio_dev)     |
> device_release                       |
> //free indio_dev                     |
>                                      | iio_push_to_buffers(indio_dev)
>                                      | //use indio_dev
> 
> Fix it by ensuring that the work is canceled before proceeding with
> the cleanup in at91_adc_remove.
> 
> Fixes: 27e177190891 ("iio:adc:at91_adc8xx: introduce new atmel adc driver")

I believe that the commit that introduced the workqueue is different
than the one you tagged here.

With that changed,

Reviewed-by: Eugen Hristev <eugen.hristev@linaro.org>

> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
> ---
>  drivers/iio/adc/at91-sama5d2_adc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
> index 8e5aaf15a921..4ba52b500054 100644
> --- a/drivers/iio/adc/at91-sama5d2_adc.c
> +++ b/drivers/iio/adc/at91-sama5d2_adc.c
> @@ -2491,6 +2491,7 @@ static void at91_adc_remove(struct platform_device *pdev)
>  	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
>  	struct at91_adc_state *st = iio_priv(indio_dev);
>  
> +	cancel_work_sync(&st->touch_st.workq);
>  	iio_device_unregister(indio_dev);
>  
>  	at91_adc_dma_disable(st);