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

commit 2e786eb2f9cebb07e317226b60054df510b60c65 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: a689554ba6ed ("drm/msm: Initial add DSI connector support")
Cc: stable@vger.kernel.org	# 4.1
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/502668/
Link: https://lore.kernel.org/r/20220913085320.8577-4-johan+linaro@kernel.org
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/msm/dsi/dsi.c b/drivers/gpu/drm/msm/dsi/dsi.c
index 1625328fa43024e66fa1f67a90a747e4d5ce5fbb..3db85b5c0febd8543ea1819b375bb5c879edccdb 100644 (file)
--- a/drivers/gpu/drm/msm/dsi/dsi.c
+++ b/drivers/gpu/drm/msm/dsi/dsi.c
@@ -227,6 +227,12 @@ int msm_dsi_modeset_init(struct msm_dsi *msm_dsi, struct drm_device *dev,
                return -EINVAL;
 
        priv = dev->dev_private;
+
+       if (priv->num_bridges == ARRAY_SIZE(priv->bridges)) {
+               DRM_DEV_ERROR(dev->dev, "too many bridges\n");
+               return -ENOSPC;
+       }
+
        msm_dsi->dev = dev;
 
        ret = msm_dsi_host_modeset_init(msm_dsi->host, dev);