[PATCH v2 2/5] drm/bridge/panel: hold a reference to the wrapped panel

drm_panel_bridge_add_typed() stores a pointer to the drm_panel it
wraps, but never acquires a reference to it. If the panel device
goes away while a panel_bridge still exists, the dangling pointer can
be dereferenced through panel_bridge->panel.

Acquire a reference in drm_panel_bridge_add_typed() with drm_panel_get()
and release it in each teardown path.

Reviewed-by: Maxime Ripard <[email protected]>
Signed-off-by: Albert Esteve <[email protected]>
---
 drivers/gpu/drm/bridge/panel.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
index 4978ec98a0828..6b98ad19508df 100644
--- a/drivers/gpu/drm/bridge/panel.c
+++ b/drivers/gpu/drm/bridge/panel.c
@@ -294,7 +294,7 @@ struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel,
 		return (void *)panel_bridge;
 
 	panel_bridge->connector_type = connector_type;
-	panel_bridge->panel = panel;
+	panel_bridge->panel = drm_panel_get(panel);
 
 	panel_bridge->bridge.of_node = panel->dev->of_node;
 	panel_bridge->bridge.ops = DRM_BRIDGE_OP_MODES;
@@ -316,6 +316,7 @@ EXPORT_SYMBOL(drm_panel_bridge_add_typed);
 void drm_panel_bridge_remove(struct drm_bridge *bridge)
 {
 	struct panel_bridge *panel_bridge;
+	struct drm_panel *panel;
 
 	if (!bridge)
 		return;
@@ -326,10 +327,12 @@ void drm_panel_bridge_remove(struct drm_bridge *bridge)
 	}
 
 	panel_bridge = drm_bridge_to_panel_bridge(bridge);
+	panel = panel_bridge->panel;
 
 	drm_bridge_remove(bridge);
 	/* TODO remove this after reworking panel_bridge lifetime */
-	devm_drm_put_bridge(panel_bridge->panel->dev, bridge);
+	devm_drm_put_bridge(panel->dev, bridge);
+	drm_panel_put(panel);
 }
 EXPORT_SYMBOL(drm_panel_bridge_remove);
 
@@ -357,11 +360,14 @@ EXPORT_SYMBOL(drm_panel_bridge_set_orientation);
 static void devm_drm_panel_bridge_release(struct device *dev, void *res)
 {
 	struct drm_bridge *bridge = *(struct drm_bridge **)res;
+	struct panel_bridge *panel_bridge;
 
 	if (!bridge)
 		return;
 
+	panel_bridge = drm_bridge_to_panel_bridge(bridge);
 	drm_bridge_remove(bridge);
+	drm_panel_put(panel_bridge->panel);
 }
 
 /**

-- 
2.54.0