The DSI encoder sets dssdev->ops->dsi.set_config, which is stored at the
same offset as dssdev->ops->hdmi.set_hdmi_mode. The code in omap_encoder
only checks if dssdev->ops->hdmi.set_hdmi_mode is NULL. Due to the way
union works, it won't be NULL if dsi.set_config is set. This means
dsi_set_config will be called with config=hdmi_mode=false=NULL parameter
resulting in a NULL dereference. Also the dereference happens while
console is locked, so kernel hangs without any debug output (can be
avoided by fbmem's lockless_register_fb=1 parameter).
This fixes the issue by exiting early if the output type definitely
has no hdmi_set operations.
Fixes: 83910ad3f51fb ("drm/omap: Move most omap_dss_driver operations to omap_dss_device_ops")
Signed-off-by: Sebastian Reichel <sebastian.reichel@xxxxxxxxxxxxx>
---
drivers/gpu/drm/omapdrm/omap_encoder.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/drivers/gpu/drm/omapdrm/omap_encoder.c b/drivers/gpu/drm/omapdrm/omap_encoder.c
index 32bbe3a80e7d..ba0099f0644c 100644
--- a/drivers/gpu/drm/omapdrm/omap_encoder.c
+++ b/drivers/gpu/drm/omapdrm/omap_encoder.c
@@ -122,6 +122,14 @@ static void omap_encoder_mode_set(struct drm_encoder *encoder,
dssdev = omap_encoder->output;
+ /* The following operations access dssdev->ops->hdmi, which is a union
+ * also used by DSI. This ensures, that the field does not have data
+ * for DSI (or any other future output type).
+ */
+ if (dssdev->output_type != OMAP_DISPLAY_TYPE_HDMI &&
+ dssdev->output_type != OMAP_DISPLAY_TYPE_DVI)
+ return;
+
if (dssdev->ops->hdmi.set_hdmi_mode)
dssdev->ops->hdmi.set_hdmi_mode(dssdev, hdmi_mode);
--
2.19.1
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