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

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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: 1ef7ed4835 ("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>
This commit is contained in:
Ma Ke 2025-08-12 15:19:32 +08:00 committed by Chun-Kuang Hu
parent f5b1819193
commit 1f403699c4
1 changed files with 14 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
drivers/gpu/drm/mediatek/mtk_drm_drv.c
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@ -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) {