drm/i915: Fix possible race in intel_dp_add_mst_connector()

BugLink: https://bugs.launchpad.net/bugs/1836802
commit 7c4512300cfa5a4dcc8c1c52ae61e3fa4bd11a39 upstream.

This hasn't caused any issues yet that I'm aware of, but as Ville
Syrjälä pointed out - we need to make sure that
intel_connector->mst_port is set before initializing MST connectors,
since in theory we could potentially check intel_connector->mst_port in
i915_hpd_poll_init_work() after registering the connector but before
having written it's value.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: stable@vger.kernel.org
Link: https://patchwork.freedesktop.org/patch/msgid/20181106213017.14563-2-lyude@redhat.com
(cherry picked from commit 66a5ab1034be801630816d1fa6cfc30db1a2f0b0)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index fd36015f8b83a771f4801d68b2543f83b794d25b..37878f27191ed86095d986972ca708c7d116959c 100644 (file)
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -470,6 +470,10 @@ static struct drm_connector *intel_dp_add_mst_connector(struct drm_dp_mst_topolo
        if (!intel_connector)
                return NULL;
 
+       intel_connector->get_hw_state = intel_dp_mst_get_hw_state;
+       intel_connector->mst_port = intel_dp;
+       intel_connector->port = port;
+
        connector = &intel_connector->base;
        ret = drm_connector_init(dev, connector, &intel_dp_mst_connector_funcs,
                                 DRM_MODE_CONNECTOR_DisplayPort);
@@ -480,10 +484,6 @@ static struct drm_connector *intel_dp_add_mst_connector(struct drm_dp_mst_topolo
 
        drm_connector_helper_add(connector, &intel_dp_mst_connector_helper_funcs);
 
-       intel_connector->get_hw_state = intel_dp_mst_get_hw_state;
-       intel_connector->mst_port = intel_dp;
-       intel_connector->port = port;
-
        for_each_pipe(dev_priv, pipe) {
                struct drm_encoder *enc =
                        &intel_dp->mst_encoders[pipe]->base.base;