Re: [PATCH 1/2] iio: temperature: hid-sensor-temperature: Use per-instance callbacks

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] iio: hid-sensor-temperature: Use-After-Free of callback struct on unbind
--

commit c0e839b50a28c72b4e45a4af57921da5a4656f96
Author: Christopher Hoover <ch@murgatroid.com>

iio: temperature: hid-sensor-temperature: Use per-instance callbacks

This patch moves the hid_sensor_hub_callbacks structure from a static
global variable to the dynamically allocated temperature_state structure
to fix an issue where platform devices are overwritten in a multi-sensor
setup.

Cc: stable@vger.kernel.org

> diff --git a/drivers/iio/temperature/hid-sensor-temperature.c b/drivers/iio/temperature/hid-sensor-temperature.c
> index 5e3262e461f46..35b8643305b9f 100644
> --- a/drivers/iio/temperature/hid-sensor-temperature.c
> +++ b/drivers/iio/temperature/hid-sensor-temperature.c
[ ... ]
> @@ -237,9 +233,11 @@ static int hid_temperature_probe(struct platform_device *pdev)
>  
>  	platform_set_drvdata(pdev, indio_dev);
>  
> -	temperature_callbacks.pdev = pdev;
> +	temp_st->callbacks.send_event = temperature_proc_event;
> +	temp_st->callbacks.capture_sample = temperature_capture_sample;
> +	temp_st->callbacks.pdev = pdev;
>  	ret = sensor_hub_register_callback(hsdev, HID_USAGE_SENSOR_TEMPERATURE,
> -					   &temperature_callbacks);
> +					   &temp_st->callbacks);

[Severity: High]
Could this change introduce a use-after-free during driver unbind?

Since temp_st is allocated using devm_iio_device_alloc(), its lifetime is now
tied to the driver bind lifecycle and it will be freed automatically after
the remove callback returns.

During unbind, hid_temperature_remove() calls sensor_hub_remove_callback().
This removes the callback from dyn_callback_list, but does not synchronize
with a concurrently executing sensor_hub_raw_event() on another CPU:

drivers/hid/hid-sensor-hub.c:sensor_hub_raw_event() {
    ...
    if (callback->capture_sample) {
        if (report->field[i]->logical)
            callback->capture_sample(hsdev, ...);
    ...
}

If sensor_hub_remove_callback() finishes and devres frees temp_st while
sensor_hub_raw_event() is still running, could the raw event path
dereference the freed callback function pointers?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261007072329.27806-1-ch@murgatroid.com?part=1