[PATCH 4.18 170/171] drm/i915: Fix possible race in intel_dp_add_mst_connector()

Greg Kroah-Hartman
2018-11-19T16:46:43Z

From: Lyude Paul <lyude@redhat.com>

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>

---
drivers/gpu/drm/i915/intel_dp_mst.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -464,6 +464,10 @@ static struct drm_connector *intel_dp_ad
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);
@@ -474,10 +478,6 @@ static struct drm_connector *intel_dp_ad

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;