linux-kernel - [PATCH] drm/msm: Initialize mode

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Date:   Thu, 12 Jan 2023 20:10:51 -0800
From:   Bjorn Andersson <quic_bjorande@...cinc.com>
To:     Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Johan Hovold <johan@...nel.org>
CC:     Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        "Daniel Vetter" <daniel@...ll.ch>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: [PATCH] drm/msm: Initialize mode_config earlier

Invoking drm_bridge_hpd_notify() on a drm_bridge with a HPD-enabled
bridge_connector ends up in drm_bridge_connector_hpd_cb() calling
drm_kms_helper_hotplug_event(), which assumes that the associated
drm_device's mode_config.funcs is a valid pointer.

But in the MSM DisplayPort driver the HPD enablement happens at bind
time and mode_config.funcs is initialized late in msm_drm_init(). This
means that there's a window for hot plug events to dereference a NULL
mode_config.funcs.

Move the assignment of mode_config.funcs before the bind, to avoid this
scenario.

Reported-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
---
 drivers/gpu/drm/msm/msm_drv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/msm_drv.c b/drivers/gpu/drm/msm/msm_drv.c
index ee2f60b6f09b..7ac670f3e6ab 100644
--- a/drivers/gpu/drm/msm/msm_drv.c
+++ b/drivers/gpu/drm/msm/msm_drv.c
@@ -438,6 +438,9 @@ static int msm_drm_init(struct device *dev, const struct drm_driver *drv)
 
 	drm_mode_config_init(ddev);
 
+	ddev->mode_config.funcs = &mode_config_funcs;
+	ddev->mode_config.helper_private = &mode_config_helper_funcs;
+
 	ret = msm_init_vram(ddev);
 	if (ret)
 		return ret;
@@ -479,9 +482,6 @@ static int msm_drm_init(struct device *dev, const struct drm_driver *drv)
 
 	drm_helper_move_panel_connectors_to_head(ddev);
 
-	ddev->mode_config.funcs = &mode_config_funcs;
-	ddev->mode_config.helper_private = &mode_config_helper_funcs;
-
 	for (i = 0; i < priv->num_crtcs; i++) {
 		/* initialize event thread */
 		priv->event_thread[i].crtc_id = priv->crtcs[i]->base.id;
-- 
2.37.3