[PATCH] thermal/core: Fix refcount bugs in __thermal_cooling_device_register()

[Liang He <windhl@126.com>]

For each new reference of 'device_node', we should increase its
refcount. Otherwise, there will be premature free.

For example, in drivers\thermal\tegra\soctherm.c, the function
soctherm_init_hw_throt_cdev() will use for_each_child_of_node() to
iterate its child device_node which will be then passed into
 __thermal_cooling_device_register(). As for_each_xxx OF APIs will
automatically increase and decrease the refcount of 'device_node',
we should use additional of_node_get() to record the new refernece.

NOTE, we should also call the corresponding of_node_put() in fail path
or when the *_unregister() function is called.

Fixes: a116b5d44f14 ("thermal: core: introduce thermal_of_cooling_device_register")
Signed-off-by: Liang He <windhl@126.com>
---
 I cannot confirm, in *_unregister, we should put of_node_put() in or
out of the *_lock/*_unlock functions. Please check it carefully.

 drivers/thermal/thermal_core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
index cdc0552e8c42..c459e2958b7b 100644
--- a/drivers/thermal/thermal_core.c
+++ b/drivers/thermal/thermal_core.c
@@ -919,7 +919,7 @@ __thermal_cooling_device_register(struct device_node *np,
 
 	mutex_init(&cdev->lock);
 	INIT_LIST_HEAD(&cdev->thermal_instances);
-	cdev->np = np;
+	cdev->np = of_node_get(np);
 	cdev->ops = ops;
 	cdev->updated = false;
 	cdev->device.class = &thermal_class;
@@ -947,6 +947,7 @@ __thermal_cooling_device_register(struct device_node *np,
 	return cdev;
 
 out_kfree_type:
+	of_node_put(cdev->np);
 	thermal_cooling_device_destroy_sysfs(cdev);
 	kfree(cdev->type);
 	put_device(&cdev->device);
@@ -1111,6 +1112,7 @@ void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)
 
 	mutex_unlock(&thermal_list_lock);
 
+	of_node_put(cdev->np);
 	ida_simple_remove(&thermal_cdev_ida, cdev->id);
 	device_del(&cdev->device);
 	thermal_cooling_device_destroy_sysfs(cdev);
-- 
2.25.1