linux-kernel - [PATCH 3.19.y-ckt 053/102] drm/dp/mst: Remove port after removing connector.

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Message-Id: <1442944358-1248-54-git-send-email-kamal@canonical.com>
Date:	Tue, 22 Sep 2015 10:51:49 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Dave Airlie <airlied@...hat.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.19.y-ckt 053/102] drm/dp/mst: Remove port after removing connector.

3.19.8-ckt7 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>

commit 4772ff03df8094fd99d28de5fcf5df3a3e9c68bb upstream.

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: Dave Airlie <airlied@...hat.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
Signed-off-by: Jani Nikula <jani.nikula@...el.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 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 8239563..6c0a1b0 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -869,9 +869,10 @@ 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);
 
@@ -2641,7 +2642,7 @@ 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
@@ -2650,15 +2651,21 @@ 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 3dab77c..b863298 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -689,8 +689,6 @@ 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;
 };
 
 /**
-- 
1.9.1

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