A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers").
This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free.
Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix.
Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.
Fixes: 1f403699c40f ("drm/mediatek: Fix device/node reference count leaks in mtk_drm_get_all_drm_priv") Reported-by: Sjoerd Simons sjoerd@collabora.com Link: https://lore.kernel.org/r/20251003-mtk-drm-refcount-v1-1-3b3f2813b0db@collab... Cc: stable@vger.kernel.org Cc: Ma Ke make24@iscas.ac.cn Cc: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Johan Hovold johan@kernel.org --- drivers/gpu/drm/mediatek/mtk_drm_drv.c | 10 ---------- 1 file changed, 10 deletions(-)
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c index 384b0510272c..a94c51a83261 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c @@ -686,10 +686,6 @@ static int mtk_drm_bind(struct device *dev) 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; } @@ -697,18 +693,12 @@ static int mtk_drm_bind(struct device *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) { drm_dev_unregister(private->drm); 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;
Il 06/10/25 11:39, Johan Hovold ha scritto:
A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers").
This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free.
Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix.
Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.
Fixes: 1f403699c40f ("drm/mediatek: Fix device/node reference count leaks in mtk_drm_get_all_drm_priv") Reported-by: Sjoerd Simons sjoerd@collabora.com Link: https://lore.kernel.org/r/20251003-mtk-drm-refcount-v1-1-3b3f2813b0db@collab... Cc: stable@vger.kernel.org Cc: Ma Ke make24@iscas.ac.cn Cc: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Johan Hovold johan@kernel.org
Heh, nice!
Reviewed-by: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com
On Mon, 2025-10-06 at 11:39 +0200, Johan Hovold wrote:
A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers").
This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free.
Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix.
Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.
Thanks for correcting my "fix". This looks better and i can confirm it fixes the issue :)
Reviewed-By: Sjoerd Simons sjoerd@collabora.com Tested-By: Sjoerd Simons sjoerd@collabora.com
Fixes: 1f403699c40f ("drm/mediatek: Fix device/node reference count leaks in mtk_drm_get_all_drm_priv") Reported-by: Sjoerd Simons sjoerd@collabora.com Link: https://lore.kernel.org/r/20251003-mtk-drm-refcount-v1-1-3b3f2813b0db@collab... Cc: stable@vger.kernel.org Cc: Ma Ke make24@iscas.ac.cn Cc: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Johan Hovold johan@kernel.org
drivers/gpu/drm/mediatek/mtk_drm_drv.c | 10 ---------- 1 file changed, 10 deletions(-)
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c index 384b0510272c..a94c51a83261 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c @@ -686,10 +686,6 @@ static int mtk_drm_bind(struct device *dev) 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; } @@ -697,18 +693,12 @@ static int mtk_drm_bind(struct device *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) { drm_dev_unregister(private->drm); 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;
On Mon, 2025-10-06 at 11:39 +0200, Johan Hovold wrote:
A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers").
This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free.
Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix.
Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.
We ran into the same issue in mesaci[1] and have test validated this proposed fix. It was tested with Linux 6.17.3 + this fix.
[1] https://gitlab.freedesktop.org/RickXy/mesa/-/jobs/86389548
Tested-by: Ritesh Raj Sarraf ritesh.sarraf@collabora.com
Fixes: 1f403699c40f ("drm/mediatek: Fix device/node reference count leaks in mtk_drm_get_all_drm_priv") Reported-by: Sjoerd Simons sjoerd@collabora.com Link: https://lore.kernel.org/r/20251003-mtk-drm-refcount-v1-1-3b3f2813b0db@collab... Cc: stable@vger.kernel.org Cc: Ma Ke make24@iscas.ac.cn Cc: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Johan Hovold johan@kernel.org
Hi Chun-Kuang,
On Mon, Oct 06, 2025 at 11:39:37AM +0200, Johan Hovold wrote:
A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers").
This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free.
Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix.
Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.
Fixes: 1f403699c40f ("drm/mediatek: Fix device/node reference count leaks in mtk_drm_get_all_drm_priv") Reported-by: Sjoerd Simons sjoerd@collabora.com Link: https://lore.kernel.org/r/20251003-mtk-drm-refcount-v1-1-3b3f2813b0db@collab... Cc: stable@vger.kernel.org Cc: Ma Ke make24@iscas.ac.cn Cc: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Johan Hovold johan@kernel.org
This patch fixes a regression in 6.17-rc4 that apparently breaks boot for some users. To make things worse, the offending commit was also backported to the stable trees.
You need to get this one into mainline as soon as possible, that is, this week and into 6.18-rc4.
Johan
On Mon, 2025-10-06 at 11:39 +0200, Johan Hovold wrote:
External email : Please do not click links or open attachments until you have verified the sender or the content.
A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers").
This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free.
Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix.
Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.
Reviewed-by: CK Hu ck.hu@mediatek.com
Fixes: 1f403699c40f ("drm/mediatek: Fix device/node reference count leaks in mtk_drm_get_all_drm_priv") Reported-by: Sjoerd Simons sjoerd@collabora.com Link: https://lore.kernel.org/r/20251003-mtk-drm-refcount-v1-1-3b3f2813b0db@collab... Cc: stable@vger.kernel.org Cc: Ma Ke make24@iscas.ac.cn Cc: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Johan Hovold johan@kernel.org
drivers/gpu/drm/mediatek/mtk_drm_drv.c | 10 ---------- 1 file changed, 10 deletions(-)
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c index 384b0510272c..a94c51a83261 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c @@ -686,10 +686,6 @@ static int mtk_drm_bind(struct device *dev) 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;} @@ -697,18 +693,12 @@ static int mtk_drm_bind(struct device *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) { drm_dev_unregister(private->drm); 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;-- 2.49.1
Johan Hovold johan@kernel.org 於 2025年10月6日 週一 上午9:48寫道：
A recent change fixed device reference leaks when looking up drm platform device driver data during bind() but failed to remove a partial fix which had been added by commit 80805b62ea5b ("drm/mediatek: Fix kobject put for component sub-drivers").
This results in a reference imbalance on component bind() failures and on unbind() which could lead to a user-after-free.
Make sure to only drop the references after retrieving the driver data by effectively reverting the previous partial fix.
Note that holding a reference to a device does not prevent its driver data from going away so there is no point in keeping the reference.
Applied to mediatek-drm-fixes [1], thanks.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/log/?...
Regards, Chun-Kuang.
Fixes: 1f403699c40f ("drm/mediatek: Fix device/node reference count leaks in mtk_drm_get_all_drm_priv") Reported-by: Sjoerd Simons sjoerd@collabora.com Link: https://lore.kernel.org/r/20251003-mtk-drm-refcount-v1-1-3b3f2813b0db@collab... Cc: stable@vger.kernel.org Cc: Ma Ke make24@iscas.ac.cn Cc: AngeloGioacchino Del Regno angelogioacchino.delregno@collabora.com Signed-off-by: Johan Hovold johan@kernel.org
drivers/gpu/drm/mediatek/mtk_drm_drv.c | 10 ---------- 1 file changed, 10 deletions(-)
diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c index 384b0510272c..a94c51a83261 100644 --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c @@ -686,10 +686,6 @@ static int mtk_drm_bind(struct device *dev) 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;} @@ -697,18 +693,12 @@ static int mtk_drm_bind(struct device *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) { drm_dev_unregister(private->drm); 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;-- 2.49.1
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AngeloGioacchino Del Regno -
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