[PATCH v9 24/61] drm/rockchip: dw_hdmi_qp: Fix NULL deref in PM ops on incomplete bind

The system-sleep PM callbacks fetch the driver state via
dev_get_drvdata() and dereference it unconditionally.  However, they can
run while the device is not fully bound.  If the system suspends before
the component framework invokes the bind callback (e.g. during a
deferred probe waiting for the VOP), dev_get_drvdata() returns NULL.
Moreover, if dw_hdmi_qp_bind() fails, drvdata is already set but
hdmi->hdmi is left holding an error pointer.

In either case dw_hdmi_qp_rockchip_resume() dereferences an invalid
pointer, causing a kernel panic; the suspend path is equally affected.

Guard both callbacks against NULL checks, and reset hdmi->hdmi to NULL
when dw_hdmi_qp_bind() fails so the guards are effective.
hdmi->ctrl_ops is assigned before platform_set_drvdata(), so it is safe
to use whenever drvdata is non-NULL.

Fixes: 128a9bf8ace2 ("drm/rockchip: Add basic RK3588 HDMI output support")
Reported-by: Sashiko <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Signed-off-by: Cristian Ciocaltea <[email protected]>
---
 drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c b/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c
index 9c4cf68d79d5..7c9d26d79664 100644
--- a/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c
+++ b/drivers/gpu/drm/rockchip/dw_hdmi_qp-rockchip.c
@@ -686,9 +686,12 @@ static int dw_hdmi_qp_rockchip_bind(struct device *dev, struct device *master,
 	platform_set_drvdata(pdev, hdmi);
 
 	hdmi->hdmi = dw_hdmi_qp_bind(pdev, encoder, &plat_data);
-	if (IS_ERR(hdmi->hdmi))
-		return dev_err_probe(hdmi->dev, PTR_ERR(hdmi->hdmi),
+	if (IS_ERR(hdmi->hdmi)) {
+		ret = PTR_ERR(hdmi->hdmi);
+		hdmi->hdmi = NULL;
+		return dev_err_probe(hdmi->dev, ret,
 				     "Failed to bind dw-hdmi-qp");
+	}
 
 	connector = drm_bridge_connector_init(drm, encoder);
 	if (IS_ERR(connector))
@@ -726,7 +729,8 @@ static int __maybe_unused dw_hdmi_qp_rockchip_suspend(struct device *dev)
 {
 	struct rockchip_hdmi_qp *hdmi = dev_get_drvdata(dev);
 
-	dw_hdmi_qp_suspend(dev, hdmi->hdmi);
+	if (hdmi && hdmi->hdmi)
+		dw_hdmi_qp_suspend(dev, hdmi->hdmi);
 
 	return 0;
 }
@@ -735,12 +739,15 @@ static int __maybe_unused dw_hdmi_qp_rockchip_resume(struct device *dev)
 {
 	struct rockchip_hdmi_qp *hdmi = dev_get_drvdata(dev);
 
-	hdmi->ctrl_ops->io_init(hdmi);
+	if (hdmi) {
+		hdmi->ctrl_ops->io_init(hdmi);
 
-	dw_hdmi_qp_resume(dev, hdmi->hdmi);
+		if (hdmi->hdmi)
+			dw_hdmi_qp_resume(dev, hdmi->hdmi);
 
-	if (hdmi->encoder.encoder.dev)
-		drm_helper_hpd_irq_event(hdmi->encoder.encoder.dev);
+		if (hdmi->encoder.encoder.dev)
+			drm_helper_hpd_irq_event(hdmi->encoder.encoder.dev);
+	}
 
 	return 0;
 }

-- 
2.55.0