drm/mst: Avoid dereferencing a NULL mstb in drm_dp_mst_handle_up_req()

In case of an unknown broadcast message is sent mstb will remain unset, so check for this. Cc: Dave Airlie <[email protected]> Cc: Lyude <[email protected]> Cc: Daniel Vetter <[email protected]> Signed-off-by: Imre Deak <[email protected]> Reviewed-by: Lyude <[email protected]> Cc: [email protected] Signed-off-by: Daniel Vetter <[email protected]> Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
gibsson · Jul 20, 2017 · 7f8b398 · 7f8b398
1 parent 448421b
commit 7f8b398
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -2324,7 +2324,9 @@ static int drm_dp_mst_handle_up_req(struct drm_dp_mst_topology_mgr *mgr)
 			DRM_DEBUG_KMS("Got RSN: pn: %d avail_pbn %d\n", msg.u.resource_stat.port_number, msg.u.resource_stat.available_pbn);
 		}
 
-		drm_dp_put_mst_branch_device(mstb);
+		if (mstb)
+			drm_dp_put_mst_branch_device(mstb);
+
 		memset(&mgr->up_req_recv, 0, sizeof(struct drm_dp_sideband_msg_rx));
 	}
 	return ret;