On Tue, 29 Aug 2023 13:50:59 -0700 Guenter Roeck <groeck@xxxxxxxxxx> wrote: > On Mon, Aug 28, 2023 at 8:06 PM Tzung-Bi Shih <tzungbi@xxxxxxxxxx> wrote: > > > > cros_ec_sensors_push_data() reads `indio_dev->active_scan_mask` and > > calls iio_push_to_buffers_with_timestamp() without making sure the > > `indio_dev` stays in buffer mode. There is a race if `indio_dev` exits > > buffer mode right before cros_ec_sensors_push_data() accesses them. > > > > An use-after-free on `indio_dev->active_scan_mask` was observed. The > > call trace: > > [...] > > _find_next_bit > > cros_ec_sensors_push_data > > cros_ec_sensorhub_event > > blocking_notifier_call_chain > > cros_ec_irq_thread > > > > It was caused by a race condition: one thread just freed > > `active_scan_mask` at [1]; while another thread tried to access the > > memory at [2]. > > > > Fix it by calling iio_device_claim_buffer_mode() to ensure the > > `indio_dev` can't exit buffer mode during cros_ec_sensors_push_data(). > > > > [1]: https://elixir.bootlin.com/linux/v6.5/source/drivers/iio/industrialio-buffer.c#L1189 > > [2]: https://elixir.bootlin.com/linux/v6.5/source/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c#L198 > > > > Cc: stable@xxxxxxxxxxxxxxx > > Fixes: aa984f1ba4a4 ("iio: cros_ec: Register to cros_ec_sensorhub when EC supports FIFO") > > Signed-off-by: Tzung-Bi Shih <tzungbi@xxxxxxxxxx> > > Reviewed-by: Guenter Roeck <groeck@xxxxxxxxxxxx> Applied to the fixes-togreg branch of iio.git. Note I'll be rebasing that tree on rc1 before I send a pull request. So this will take a week or two to go upstream. Thanks, Jonathan > > > --- > > Changes from v1(https://patchwork.kernel.org/project/linux-iio/patch/20230828094339.1248472-1-tzungbi@xxxxxxxxxx/): > > - Use iio_device_{claim|release}_buffer_mode() instead of accessing `mlock`. > > > > drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c > > index b72d39fc2434..6bfe5d6847e7 100644 > > --- a/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c > > +++ b/drivers/iio/common/cros_ec_sensors/cros_ec_sensors_core.c > > @@ -190,8 +190,11 @@ int cros_ec_sensors_push_data(struct iio_dev *indio_dev, > > /* > > * Ignore samples if the buffer is not set: it is needed if the ODR is > > * set but the buffer is not enabled yet. > > + * > > + * Note: iio_device_claim_buffer_mode() returns -EBUSY if the buffer > > + * is not enabled. > > */ > > - if (!iio_buffer_enabled(indio_dev)) > > + if (iio_device_claim_buffer_mode(indio_dev) < 0) > > return 0; > > > > out = (s16 *)st->samples; > > @@ -210,6 +213,7 @@ int cros_ec_sensors_push_data(struct iio_dev *indio_dev, > > iio_push_to_buffers_with_timestamp(indio_dev, st->samples, > > timestamp + delta); > > > > + iio_device_release_buffer_mode(indio_dev); > > return 0; > > } > > EXPORT_SYMBOL_GPL(cros_ec_sensors_push_data); > > -- > > 2.42.0.rc2.253.gd59a3bf2b4-goog > >
