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Thu, 3 Apr 2025 12:47:45 +0200 (CEST)
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
To: chunkuang.hu@kernel.org
Cc: p.zabel@pengutronix.de,
airlied@gmail.com,
simona@ffwll.ch,
matthias.bgg@gmail.com,
angelogioacchino.delregno@collabora.com,
nancy.lin@mediatek.com,
ck.hu@mediatek.com,
djkurtz@chromium.org,
littlecvr@chromium.org,
bibby.hsieh@mediatek.com,
dri-devel@lists.freedesktop.org,
linux-mediatek@lists.infradead.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
wenst@chromium.org,
kernel@collabora.com
Subject: [PATCH v2 2/5] drm/mediatek: Fix kobject put for component
sub-drivers
Date: Thu, 3 Apr 2025 12:47:38 +0200
Message-ID: <20250403104741.71045-3-angelogioacchino.delregno@collabora.com>
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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 mm=
sys support")
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20250402083628.20111-3-angelogioacchino.del=
regno@collabora.com
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collab=
ora.com>
---
drivers/gpu/drm/mediatek/mtk_drm_drv.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/media=
tek/mtk_drm_drv.c
index a8fbccb50c74..6b31df587507 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -676,6 +676,10 @@ static int mtk_drm_bind(struct device *dev)
for (i =3D 0; i < private->data->mmsys_dev_num; i++)
private->all_drm_private[i]->drm =3D NULL;
err_put_dev:
+ for (i =3D 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;
}
@@ -683,6 +687,7 @@ static int mtk_drm_bind(struct device *dev)
static void mtk_drm_unbind(struct device *dev)
{
struct mtk_drm_private *private =3D dev_get_drvdata(dev);
+ int i;
=20
/* for multi mmsys dev, unregister drm dev in mmsys master */
if (private->drm_master) {
@@ -690,6 +695,10 @@ static void mtk_drm_unbind(struct device *dev)
mtk_drm_kms_deinit(private->drm);
drm_dev_put(private->drm);
=20
+ for (i =3D 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 =3D false;
--=20
2.48.1