[PATCH v5 14/15] media: rc: Use after free in ir_raw_event_handle()

If rc_unregister_device() is called while IR is being processed, then
ir_raw_event_handle() could call wake_up_process(dev->raw->thread)
after kthread_stop(dev->raw->thread). Avoid use after free by using
get_task_struct().

Fixes: dccc0c3ddf8f ("media: rc: fix race between unregister and urb/irq callbacks")
Signed-off-by: Sean Young <[email protected]>
Cc: [email protected]
---
 drivers/media/rc/rc-ir-raw.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/media/rc/rc-ir-raw.c b/drivers/media/rc/rc-ir-raw.c
index 46c50f423798..86de1b26731d 100644
--- a/drivers/media/rc/rc-ir-raw.c
+++ b/drivers/media/rc/rc-ir-raw.c
@@ -630,8 +630,13 @@ int ir_raw_event_register(struct rc_dev *dev)
 
 void ir_raw_event_free(struct rc_dev *dev)
 {
-	kfree(dev->raw);
-	dev->raw = NULL;
+	if (dev->raw) {
+		timer_delete_sync(&dev->raw->edge_handle);
+		if (dev->raw->thread)
+			put_task_struct(dev->raw->thread);
+		kfree(dev->raw);
+		dev->raw = NULL;
+	}
 }
 
 void ir_raw_event_unregister(struct rc_dev *dev)
@@ -641,6 +646,13 @@ void ir_raw_event_unregister(struct rc_dev *dev)
 	if (!dev || !dev->raw)
 		return;
 
+	/*
+	 * After ir_raw_event_unregister() is called, an sync
+	 * call to ir_raw_event_handle() can still arrive. This function
+	 * may call wake_up_process(dev->raw->thread). Ensure this memory
+	 * is not freed by kthread_stop().
+	 */
+	get_task_struct(dev->raw->thread);
 	kthread_stop(dev->raw->thread);
 	timer_delete_sync(&dev->raw->edge_handle);
 
-- 
2.55.0