Re: [PATCH v3] iio: adc: at91-sama5d2_adc: Fix potential use-after-free in sama5d2_adc driver

[Jonathan Cameron]

On Wed, 29 Oct 2025 10:40:16 +0800
Pei Xiao <xiaopei01@xxxxxxxxxx> 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 but
> quite a bit later. 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)     |
> //free indio_dev a bit later         |
>                                      | 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: 3ec2774f1cc ("iio: adc: at91-sama5d2_adc: add support for position and pressure channels")
This ID doesn't exist in my history  it should be
23ec2774f1cc

I'll fix that up whilst applying.  Ideally I'd like Eugen to take a look
but I'm fairly confident so I'll queue this up on the fixes-togreg branch
of iio.git and mark it for stable.

Thanks,

Jonathan



> Signed-off-by: Pei Xiao <xiaopei01@xxxxxxxxxx>
> ---
> changlog in v3: move cancel_work_sync after iio_device_unregister
> changlog in v2: use correct Fix id
> ---
>  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 b4c36e6a7490..aa4ba3f5a506 100644
> --- a/drivers/iio/adc/at91-sama5d2_adc.c
> +++ b/drivers/iio/adc/at91-sama5d2_adc.c
> @@ -2481,6 +2481,7 @@ static void at91_adc_remove(struct platform_device *pdev)
>  	struct at91_adc_state *st = iio_priv(indio_dev);
>  
>  	iio_device_unregister(indio_dev);
> +	cancel_work_sync(&st->touch_st.workq);
>  
>  	at91_adc_dma_disable(st);
>