3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Imre Deak <imre.deak@xxxxxxxxx> commit 7f8b3987da54cb4d41ad2545cd4d7958b9a36bdf upstream. In case of an unknown broadcast message is sent mstb will remain unset, so check for this. Cc: Dave Airlie <airlied@xxxxxxxxxx> Cc: Lyude <lyude@xxxxxxxxxx> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> Reviewed-by: Lyude <lyude@xxxxxxxxxx> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx> Link: https://patchwork.freedesktop.org/patch/msgid/20170719114330.26540-3-imre.deak@xxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/drm_dp_mst_topology.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/drivers/gpu/drm/drm_dp_mst_topology.c +++ b/drivers/gpu/drm/drm_dp_mst_topology.c @@ -2209,7 +2209,9 @@ static int drm_dp_mst_handle_up_req(stru 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;