iio: adc: at91-sama5d2_adc: Fix potential use-after-free in sama5d2_adc driver

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: 23ec2774f1cc ("iio: adc: at91-sama5d2_adc: add support for position and pressure channels")
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
index b4c36e6a7490aa9002a702e70a8b37ee3eae6324..aa4ba3f5a50603c42f4c00a5c0005f02d73a9dab 100644 (file)
--- 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);