[PATCH 4.9 15/29] iio: trigger: sysfs: fix use-after-free on remove

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Vincent Whitchurch <vincent.whitchurch@axis.com>

commit 78601726d4a59a291acc5a52da1d3a0a6831e4e8 upstream.

Ensure that the irq_work has completed before the trigger is freed.

 ==================================================================
 BUG: KASAN: use-after-free in irq_work_run_list
 Read of size 8 at addr 0000000064702248 by task python3/25

 Call Trace:
  irq_work_run_list
  irq_work_tick
  update_process_times
  tick_sched_handle
  tick_sched_timer
  __hrtimer_run_queues
  hrtimer_interrupt

 Allocated by task 25:
  kmem_cache_alloc_trace
  iio_sysfs_trig_add
  dev_attr_store
  sysfs_kf_write
  kernfs_fop_write_iter
  new_sync_write
  vfs_write
  ksys_write
  sys_write

 Freed by task 25:
  kfree
  iio_sysfs_trig_remove
  dev_attr_store
  sysfs_kf_write
  kernfs_fop_write_iter
  new_sync_write
  vfs_write
  ksys_write
  sys_write

 ==================================================================

Fixes: f38bc926d022 ("staging:iio:sysfs-trigger: Use irq_work to properly active trigger")
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Link: https://lore.kernel.org/r/20220519091925.1053897-1-vincent.whitchurch@axis.com
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/iio/trigger/iio-trig-sysfs.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/iio/trigger/iio-trig-sysfs.c
+++ b/drivers/iio/trigger/iio-trig-sysfs.c
@@ -199,6 +199,7 @@ static int iio_sysfs_trigger_remove(int
 	}
 
 	iio_trigger_unregister(t->trig);
+	irq_work_sync(&t->work);
 	iio_trigger_free(t->trig);
 
 	list_del(&t->l);