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

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: 8a3b4c17f863 ("drm/msm/dp: employ bridge mechanism for display enable and disable")
Cc: stable@vger.kernel.org	# 5.17
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/502664/
Link: https://lore.kernel.org/r/20220913085320.8577-3-johan+linaro@kernel.org
Signed-off-by: Abhinav Kumar <quic_abhinavk@quicinc.com>

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index bfd0aef..be9ed89 100644 (file)
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -1597,6 +1597,12 @@ int msm_dp_modeset_init(struct msm_dp *dp_display, 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;
+       }
+
        dp_display->drm_dev = dev;
 
        dp_priv = container_of(dp_display, struct dp_display_private, dp_display);