drm/mediatek: Fix kobject put for component sub-drivers

In function mtk_drm_get_all_drm_priv(), this driver is incrementing
the refcount for the sub-drivers of mediatek-drm with a call to
device_find_child() when taking a reference to all of those child
devices.

When the component bind fails multiple times this results in a
refcount_t overflow, as the reference count is never decremented:
fix that by adding a call to put_device() for all of the mmsys
devices in a loop, in error cases of mtk_drm_bind() and in the
mtk_drm_unbind() callback.

Fixes: 1ef7ed48356c ("drm/mediatek: Modify mediatek-drm for mt8195 multi mmsys support")
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Link: https://patchwork.kernel.org/project/dri-devel/patch/20250403104741.71045-3-angelogioacchino.delregno@collabora.com/
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 5994e2a97dc135bf4f4e046c6ebe56fec31e5ed0..593193555c07efeb9a4e925083332c091cbfee8a 100644 (file)
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -682,6 +682,10 @@ err_free:
        for (i = 0; i < private->data->mmsys_dev_num; i++)
                private->all_drm_private[i]->drm = NULL;
 err_put_dev:
+       for (i = 0; i < private->data->mmsys_dev_num; i++) {
+               /* For device_find_child in mtk_drm_get_all_priv() */
+               put_device(private->all_drm_private[i]->dev);
+       }
        put_device(private->mutex_dev);
        return ret;
 }
@@ -689,6 +693,7 @@ err_put_dev:
 static void mtk_drm_unbind(struct device *dev)
 {
        struct mtk_drm_private *private = dev_get_drvdata(dev);
+       int i;
 
        /* for multi mmsys dev, unregister drm dev in mmsys master */
        if (private->drm_master) {
@@ -696,6 +701,10 @@ static void mtk_drm_unbind(struct device *dev)
                mtk_drm_kms_deinit(private->drm);
                drm_dev_put(private->drm);
 
+               for (i = 0; i < private->data->mmsys_dev_num; i++) {
+                       /* For device_find_child in mtk_drm_get_all_priv() */
+                       put_device(private->all_drm_private[i]->dev);
+               }
                put_device(private->mutex_dev);
        }
        private->mtk_drm_bound = false;