linux-kernel - [PATCH 4.18 170/171] drm/i915: Fix possible race in intel_dp_add_mst

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Date:   Mon, 19 Nov 2018 17:29:26 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lyude Paul <lyude@...hat.com>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Subject: [PATCH 4.18 170/171] drm/i915: Fix possible race in intel_dp_add_mst_connector()

4.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lyude Paul <lyude@...hat.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@...hat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@...el.com>
Cc: stable@...r.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@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.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;