From: Dave Airlie <airl...@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

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