drm/dp/mst: Remove port after removing connector.

The port is removed synchronously, but the connector delayed.
This causes a use after free which can cause a kernel BUG with
slug_debug=FPZU. This is fixed by freeing the port after the
connector.

This fixes a regression introduced with
6b8eeca65b18ae77e175cc2b6571731f0ee413bf
"drm/dp/mst: close deadlock in connector destruction."

Cc: stable@vger.kernel.org
Cc: Dave Airlie <airlied@redhat.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

2 files changed, 13 insertions, 8 deletions

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 778bbb6425b8..1325eecb0510 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -873,9 +873,10 @@ static void drm_dp_destroy_port(struct kref *kref)
                    from an EDID retrieval */
                 if (port->connector) {
                         mutex_lock(&mgr->destroy_connector_lock);
-                        list_add(&port->connector->destroy_list, &mgr->destroy_connector_list);
+                        list_add(&port->next, &mgr->destroy_connector_list);
                         mutex_unlock(&mgr->destroy_connector_lock);
                         schedule_work(&mgr->destroy_connector_work);
+                        return;
                 }
                 drm_dp_port_teardown_pdt(port, port->pdt);
 
@@ -2660,7 +2661,7 @@ static void drm_dp_tx_work(struct work_struct *work)
 static void drm_dp_destroy_connector_work(struct work_struct *work)
 {
         struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct drm_dp_mst_topology_mgr, destroy_connector_work);
-        struct drm_connector *connector;
+        struct drm_dp_mst_port *port;
 
         /*
          * Not a regular list traverse as we have to drop the destroy
@@ -2669,15 +2670,21 @@ static void drm_dp_destroy_connector_work(struct work_struct *work)
          */
         for (;;) {
                 mutex_lock(&mgr->destroy_connector_lock);
-                connector = list_first_entry_or_null(&mgr->destroy_connector_list, struct drm_connector, destroy_list);
-                if (!connector) {
+                port = list_first_entry_or_null(&mgr->destroy_connector_list, struct drm_dp_mst_port, next);
+                if (!port) {
                         mutex_unlock(&mgr->destroy_connector_lock);
                         break;
                 }
-                list_del(&connector->destroy_list);
+                list_del(&port->next);
                 mutex_unlock(&mgr->destroy_connector_lock);
 
-                mgr->cbs->destroy_connector(mgr, connector);
+                mgr->cbs->destroy_connector(mgr, port->connector);
+
+                drm_dp_port_teardown_pdt(port, port->pdt);
+
+                if (!port->input && port->vcpi.vcpi > 0)
+                        drm_dp_mst_put_payload_id(mgr, port->vcpi.vcpi);
+                kfree(port);
         }
 }
 
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 57ca8cc383a6..3b4d8a4a23fb 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -743,8 +743,6 @@ struct drm_connector {
         uint8_t num_h_tile, num_v_tile;
         uint8_t tile_h_loc, tile_v_loc;
         uint16_t tile_h_size, tile_v_size;
-
-        struct list_head destroy_list;
 };
 
 /**