[PATCH] drm/bridge: properly refcount DT nodes in aux bridge drivers

[Dmitry Baryshkov]

The aux-bridge and aux-hpd-bridge drivers didn't call of_node_get() on
the device nodes further used for dev->of_node and platform data. When
bridge devices are released, the reference counts are decreased,
resulting in refcount underflow / use-after-free warnings. Get
corresponding refcounts during AUX bridge allocation.

Reported-by: Luca Weiss <luca.we...@fairphone.com>
Fixes: 2a04739139b2 ("drm/bridge: add transparent bridge helper")
Fixes: 26f4bac3d884 ("drm/bridge: aux-hpd: Replace of_device.h with explicit 
include")
Signed-off-by: Dmitry Baryshkov <dmitry.barysh...@linaro.org>
---
 drivers/gpu/drm/bridge/aux-bridge.c     | 2 +-
 drivers/gpu/drm/bridge/aux-hpd-bridge.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/aux-bridge.c 
b/drivers/gpu/drm/bridge/aux-bridge.c
index 49d7c2ab1ecc..54d721db0ea6 100644
--- a/drivers/gpu/drm/bridge/aux-bridge.c
+++ b/drivers/gpu/drm/bridge/aux-bridge.c
@@ -57,7 +57,7 @@ int drm_aux_bridge_register(struct device *parent)
        adev->id = ret;
        adev->name = "aux_bridge";
        adev->dev.parent = parent;
-       adev->dev.of_node = parent->of_node;
+       adev->dev.of_node = of_node_get(parent->of_node);
        adev->dev.release = drm_aux_bridge_release;
 
        ret = auxiliary_device_init(adev);
diff --git a/drivers/gpu/drm/bridge/aux-hpd-bridge.c 
b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
index 1999a053d59b..bb55f697a181 100644
--- a/drivers/gpu/drm/bridge/aux-hpd-bridge.c
+++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
@@ -68,9 +68,9 @@ struct device *drm_dp_hpd_bridge_register(struct device 
*parent,
        adev->id = ret;
        adev->name = "dp_hpd_bridge";
        adev->dev.parent = parent;
-       adev->dev.of_node = parent->of_node;
+       adev->dev.of_node = of_node_get(parent->of_node);
        adev->dev.release = drm_aux_hpd_bridge_release;
-       adev->dev.platform_data = np;
+       adev->dev.platform_data = of_node_get(np);
 
        ret = auxiliary_device_init(adev);
        if (ret) {
-- 
2.39.2