drm/msm/hdmi: fix memory corruption with too many bridges

commit 4c1294d upstream.

Add the missing sanity check on the bridge counter to avoid corrupting
data beyond the fixed-sized bridge array in case there are ever more
than eight bridges.

Fixes: a3376e3 ("drm/msm: convert to drm_bridge")
Cc: [email protected]	# 3.12
Signed-off-by: Johan Hovold <[email protected]>
Tested-by: Kuogee Hsieh <[email protected]>
Reviewed-by: Kuogee Hsieh <[email protected]>
Reviewed-by: Dmitry Baryshkov <[email protected]>
Patchwork: https://patchwork.freedesktop.org/patch/502670/
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Abhinav Kumar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: jhovold

drivers/gpu/drm/msm/hdmi/hdmi.c

@@ -295,6 +295,11 @@ int msm_hdmi_modeset_init(struct hdmi *hdmi,
 	struct platform_device *pdev = hdmi->pdev;
 	int ret;
 
+	if (priv->num_bridges == ARRAY_SIZE(priv->bridges)) {
+		DRM_DEV_ERROR(dev->dev, "too many bridges\n");
+		return -ENOSPC;
+	}
+
 	hdmi->dev = dev;
 	hdmi->encoder = encoder;