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iio: proximity: as3935: fix use-after-free on device remove

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This driver's probe() uses a mix of devm_ and non-devm_ functions. This
means that the remove order will not be the exact opposite of the probe
order.

Remove order:
1. remove() executes:
	iio_device_unregister
	iio_triggered_buffer_cleanup
	iio_trigger_unregister
	(A)
2. core frees devm resources in reverse order:
	free_irq
	iio_trigger_free
	iio_device_free

In (A) the trigger has been unregistered, but the irq handler is still
registered and active, so the trigger may still be touched via
interrupt -> as3935_event_work. This is a potential use-after-unregister.

Given that the delayed work is never canceled explicitly, it may run even
after iio_device_free. This is a potential use-after-free.

Solution: convert all probe functions to their devm_ equivalents.
Add a devm callback, called by the core on remove right after irq_free,
which explicitly cancels the delayed work. This will guarantee that all
resources are freed in the correct order.

As an added bonus, some boilerplate code can be removed.

Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
This commit is contained in:
Sven Van Asbroeck 2019-03-08 12:59:35 -05:00 committed by Jonathan Cameron
parent 71a7766b36
commit 11362b7a43
1 changed files with 21 additions and 29 deletions
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50
drivers/iio/proximity/as3935.c
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@ -345,6 +345,14 @@ static SIMPLE_DEV_PM_OPS(as3935_pm_ops, as3935_suspend, as3935_resume);
#define AS3935_PM_OPS NULL
#endif
static void as3935_stop_work(void *data)
{
struct iio_dev *indio_dev = data;
struct as3935_state *st = iio_priv(indio_dev);
cancel_delayed_work_sync(&st->work);
}
static int as3935_probe(struct spi_device *spi)
{
struct iio_dev *indio_dev;
@ -368,7 +376,6 @@ static int as3935_probe(struct spi_device *spi)
spi_set_drvdata(spi, indio_dev);
mutex_init(&st->lock);
INIT_DELAYED_WORK(&st->work, as3935_event_work);
ret = of_property_read_u32(np,
"ams,tuning-capacitor-pf", &st->tune_cap);
@ -414,22 +421,28 @@ static int as3935_probe(struct spi_device *spi)
iio_trigger_set_drvdata(trig, indio_dev);
trig->ops = &iio_interrupt_trigger_ops;
ret = iio_trigger_register(trig);
ret = devm_iio_trigger_register(&spi->dev, trig);
if (ret) {
dev_err(&spi->dev, "failed to register trigger\n");
return ret;
}
ret = iio_triggered_buffer_setup(indio_dev, iio_pollfunc_store_time,
&as3935_trigger_handler, NULL);
ret = devm_iio_triggered_buffer_setup(&spi->dev, indio_dev,
iio_pollfunc_store_time,
as3935_trigger_handler, NULL);
if (ret) {
dev_err(&spi->dev, "cannot setup iio trigger\n");
goto unregister_trigger;
return ret;
}
calibrate_as3935(st);
INIT_DELAYED_WORK(&st->work, as3935_event_work);
ret = devm_add_action(&spi->dev, as3935_stop_work, indio_dev);
if (ret)
return ret;
ret = devm_request_irq(&spi->dev, spi->irq,
&as3935_interrupt_handler,
IRQF_TRIGGER_RISING,
@ -438,35 +451,15 @@ static int as3935_probe(struct spi_device *spi)
if (ret) {
dev_err(&spi->dev, "unable to request irq\n");
goto unregister_buffer;
return ret;
}
ret = iio_device_register(indio_dev);
ret = devm_iio_device_register(&spi->dev, indio_dev);
if (ret < 0) {
dev_err(&spi->dev, "unable to register device\n");
goto unregister_buffer;
return ret;
}
return 0;
unregister_buffer:
iio_triggered_buffer_cleanup(indio_dev);
unregister_trigger:
iio_trigger_unregister(st->trig);
return ret;
}
static int as3935_remove(struct spi_device *spi)
{
struct iio_dev *indio_dev = spi_get_drvdata(spi);
struct as3935_state *st = iio_priv(indio_dev);
iio_device_unregister(indio_dev);
iio_triggered_buffer_cleanup(indio_dev);
iio_trigger_unregister(st->trig);
return 0;
}
static const struct of_device_id as3935_of_match[] = {
@ -488,7 +481,6 @@ static struct spi_driver as3935_driver = {
.pm = AS3935_PM_OPS,
},
.probe = as3935_probe,
.remove = as3935_remove,
.id_table = as3935_id,
};
module_spi_driver(as3935_driver);