drm/mediatek: Fix device/node reference count leaks in mtk_drm_get_all_drm_priv

Using device_find_child() and of_find_device_by_node() to locate
devices could cause an imbalance in the device's reference count.
device_find_child() and of_find_device_by_node() both call
get_device() to increment the reference count of the found device
before returning the pointer. In mtk_drm_get_all_drm_priv(), these
references are never released through put_device(), resulting in
permanent reference count increments. Additionally, the
for_each_child_of_node() iterator fails to release node references in
all code paths. This leaks device node references when loop
termination occurs before reaching MAX_CRTC. These reference count
leaks may prevent device/node resources from being properly released
during driver unbind operations.

As comment of device_find_child() says, 'NOTE: you will need to drop
the reference with put_device() after use'.

Cc: stable@vger.kernel.org
Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195 multi mmsys support")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
Reviewed-by: CK Hu <ck.hu@mediatek.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20250812071932.471730-1-make24@iscas.ac.cn/
Signed-off-by: Chun-Kuang Hu <chunkuang.hu@kernel.org>

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index d5e6bab364143540e1f59df481b9a9d559c39199..f8a817689e1626fe06a753c9e522114bc6b7fd28 100644 (file)
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -387,19 +387,19 @@ static bool mtk_drm_get_all_drm_priv(struct device *dev)
 
                of_id = of_match_node(mtk_drm_of_ids, node);
                if (!of_id)
-                       continue;
+                       goto next_put_node;
 
                pdev = of_find_device_by_node(node);
                if (!pdev)
-                       continue;
+                       goto next_put_node;
 
                drm_dev = device_find_child(&pdev->dev, NULL, mtk_drm_match);
                if (!drm_dev)
-                       continue;
+                       goto next_put_device_pdev_dev;
 
                temp_drm_priv = dev_get_drvdata(drm_dev);
                if (!temp_drm_priv)
-                       continue;
+                       goto next_put_device_drm_dev;
 
                if (temp_drm_priv->data->main_len)
                        all_drm_priv[CRTC_MAIN] = temp_drm_priv;
@@ -411,10 +411,17 @@ static bool mtk_drm_get_all_drm_priv(struct device *dev)
                if (temp_drm_priv->mtk_drm_bound)
                        cnt++;
 
-               if (cnt == MAX_CRTC) {
-                       of_node_put(node);
+next_put_device_drm_dev:
+               put_device(drm_dev);
+
+next_put_device_pdev_dev:
+               put_device(&pdev->dev);
+
+next_put_node:
+               of_node_put(node);
+
+               if (cnt == MAX_CRTC)
                        break;
-               }
        }
 
        if (drm_priv->data->mmsys_dev_num == cnt) {