[PATCH] drm/dp: look up the mstb passed into work function

[Dave Airlie]

From: Dave Airlie <airlied at redhat.com>

We should validate the passed in mstb under the lock
this should stop us getting an invalid mstb here.

(first attempt with cancelling work has lockdep issues).
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89366

Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index fb65f5d..ad0d1bf 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1198,9 +1198,14 @@ static struct drm_dp_mst_branch *drm_dp_get_mst_branch_device(struct drm_dp_mst_
 }
 
 static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *mgr,
-					       struct drm_dp_mst_branch *mstb)
+					       struct drm_dp_mst_branch *mstb_in)
 {
 	struct drm_dp_mst_port *port;
+	struct drm_dp_mst_branch *mstb;
+
+	mstb = drm_dp_get_validated_mstb_ref(mgr, mstb_in);
+	if (!mstb)
+		return;
 
 	if (!mstb->link_address_sent) {
 		drm_dp_send_link_address(mgr, mstb);
@@ -1219,6 +1224,7 @@ static void drm_dp_check_and_send_link_address(struct drm_dp_mst_topology_mgr *m
 		if (port->mstb)
 			drm_dp_check_and_send_link_address(mgr, port->mstb);
 	}
+	drm_dp_put_mst_branch_device(mstb);
 }
 
 static void drm_dp_mst_link_probe_work(struct work_struct *work)
-- 
2.4.1