6.6-stable review patch. If anyone has any objections, please let me know.
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From: Ma Ke make24@iscas.ac.cn
[ Upstream commit 1f403699c40f0806a707a9a6eed3b8904224021a ]
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... Signed-off-by: Chun-Kuang Hu chunkuang.hu@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/mediatek/mtk_drm_drv.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c @@ -365,19 +365,19 @@ static bool mtk_drm_get_all_drm_priv(str
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; @@ -389,10 +389,17 @@ static bool mtk_drm_get_all_drm_priv(str 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) {