linux-kernel - [PATCH v3 1/5] drm/i915: Fix possible race in intel_dp_add_mst

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Date:   Fri,  2 Nov 2018 20:19:04 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     intel-gfx@...ts.freedesktop.org
Cc:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3 1/5] drm/i915: Fix possible race in intel_dp_add_mst_connector()

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@...hat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
---
 drivers/gpu/drm/i915/intel_dp_mst.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_dp_mst.c b/drivers/gpu/drm/i915/intel_dp_mst.c
index 8b71d64ebd9d..8cb4093f8bcc 100644
--- a/drivers/gpu/drm/i915/intel_dp_mst.c
+++ b/drivers/gpu/drm/i915/intel_dp_mst.c
@@ -441,6 +441,10 @@ 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);
@@ -451,10 +455,6 @@ 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;
-- 
2.19.1