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

This change “drm/dp/mst: Remove port after removing connector.” in Linux kernel is authored by Maarten Lankhorst <maarten.lankhorst [at] linux.intel.com> on Tue Aug 11 09:54:29 2015 +0200.

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>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit 4772ff0.

There are 21 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/gpu/drm/drm_dp_mst_topology.c | 19 +++++++++++++------
 include/drm/drm_crtc.h                |  2 --
 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 778bbb6..1325eec 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 57ca8cc..3b4d8a4 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;
 };
 
 /**

The commit for this change in Linux stable tree is 4772ff0 (patch).

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