[PATCH] drm/bridge: imx8qxp-pxl2dpi: avoid of_node_put() on ERR_PTR()

[PATCH] drm/bridge: imx8qxp-pxl2dpi: avoid of_node_put() on ERR_PTR()

[Guangshuo Li]

imx8qxp_pxl2dpi_get_available_ep_from_port() may return ERR_PTR(-ENODEV)
or ERR_PTR(-EINVAL). imx8qxp_pxl2dpi_find_next_bridge() stores that
value in a __free(device_node) variable and then immediately checks
IS_ERR(ep).

On the error path, returning from the function triggers the cleanup
handler for __free(device_node). Since the device_node cleanup helper
only checks for NULL before calling of_node_put(), this results in
of_node_put(ERR_PTR(...)), which may lead to an invalid kobject_put()
dereference and crash the kernel.

Fix it by avoiding __free(device_node) for the endpoint pointer and
releasing it explicitly after obtaining the remote port parent.

This issue was found by a custom static analysis tool.

Fixes: ceea3f7806a10 ("drm/bridge: imx8qxp-pxl2dpi: simplify put of device_node pointers")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
---
 drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c b/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
index 441fd32dc91c..3610ca94a8e6 100644
--- a/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
+++ b/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
@@ -264,12 +264,15 @@ imx8qxp_pxl2dpi_get_available_ep_from_port(struct imx8qxp_pxl2dpi *p2d,
 
 static int imx8qxp_pxl2dpi_find_next_bridge(struct imx8qxp_pxl2dpi *p2d)
 {
-	struct device_node *ep __free(device_node) =
-		imx8qxp_pxl2dpi_get_available_ep_from_port(p2d, 1);
+	struct device_node *ep;
+
+	ep = imx8qxp_pxl2dpi_get_available_ep_from_port(p2d, 1);
 	if (IS_ERR(ep))
 		return PTR_ERR(ep);
 
 	struct device_node *remote __free(device_node) = of_graph_get_remote_port_parent(ep);
+	of_node_put(ep);
+
 	if (!remote || !of_device_is_available(remote)) {
 		DRM_DEV_ERROR(p2d->dev, "no available remote\n");
 		return -ENODEV;
-- 
2.43.0

Re: [PATCH] drm/bridge: imx8qxp-pxl2dpi: avoid of_node_put() on ERR_PTR()

[Frank Li]

On Sun, Apr 19, 2026 at 08:21:34PM +0800, Guangshuo Li wrote:
> imx8qxp_pxl2dpi_get_available_ep_from_port() may return ERR_PTR(-ENODEV)
> or ERR_PTR(-EINVAL). imx8qxp_pxl2dpi_find_next_bridge() stores that
> value in a __free(device_node) variable and then immediately checks
> IS_ERR(ep).
>
> On the error path, returning from the function triggers the cleanup
> handler for __free(device_node). Since the device_node cleanup helper
> only checks for NULL before calling of_node_put(), this results in
> of_node_put(ERR_PTR(...)), which may lead to an invalid kobject_put()

Please fix
DEFINE_FREE(device_node, struct device_node *, if (_T) of_node_put(_T))

If (!IS_ERR(_T))

Frank
> dereference and crash the kernel.
>
> Fix it by avoiding __free(device_node) for the endpoint pointer and
> releasing it explicitly after obtaining the remote port parent.
>
> This issue was found by a custom static analysis tool.
>
> Fixes: ceea3f7806a10 ("drm/bridge: imx8qxp-pxl2dpi: simplify put of device_node pointers")
> Cc: stable@vger.kernel.org
> Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
> ---
>  drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c b/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
> index 441fd32dc91c..3610ca94a8e6 100644
> --- a/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
> +++ b/drivers/gpu/drm/bridge/imx/imx8qxp-pxl2dpi.c
> @@ -264,12 +264,15 @@ imx8qxp_pxl2dpi_get_available_ep_from_port(struct imx8qxp_pxl2dpi *p2d,
>
>  static int imx8qxp_pxl2dpi_find_next_bridge(struct imx8qxp_pxl2dpi *p2d)
>  {
> -	struct device_node *ep __free(device_node) =
> -		imx8qxp_pxl2dpi_get_available_ep_from_port(p2d, 1);
> +	struct device_node *ep;
> +
> +	ep = imx8qxp_pxl2dpi_get_available_ep_from_port(p2d, 1);
>  	if (IS_ERR(ep))
>  		return PTR_ERR(ep);
>
>  	struct device_node *remote __free(device_node) = of_graph_get_remote_port_parent(ep);
> +	of_node_put(ep);
> +
>  	if (!remote || !of_device_is_available(remote)) {
>  		DRM_DEV_ERROR(p2d->dev, "no available remote\n");
>  		return -ENODEV;
> --
> 2.43.0
>

Re: [PATCH] drm/bridge: imx8qxp-pxl2dpi: avoid of_node_put() on ERR_PTR()

[Guangshuo Li]

Hi Frank,

Thanks for the review.

On Mon, 20 Apr 2026 at 09:56, Frank Li <Frank.li@nxp.com> wrote:
>
>
> Please fix
> DEFINE_FREE(device_node, struct device_node *, if (_T) of_node_put(_T))
>
> If (!IS_ERR(_T))
>

You're right, fixing DEFINE_FREE(device_node, ...) is the proper way
to handle this:
if (_T && !IS_ERR(_T)) of_node_put(_T)

This is a better fix than handling it only in this driver.

I'll rework the patch based on your suggestion and send v2 later.

Thanks,
Guangshuo

Re: [PATCH] drm/bridge: imx8qxp-pxl2dpi: avoid of_node_put() on ERR_PTR()

[Liu Ying]

On Mon, Apr 20, 2026 at 10:19:35AM +0800, Guangshuo Li wrote:
> [You don't often get email from lgs201920130244@gmail.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> Hi Frank,
> 
> Thanks for the review.
> 
> On Mon, 20 Apr 2026 at 09:56, Frank Li <Frank.li@nxp.com> wrote:
>>
>>
>> Please fix
>> DEFINE_FREE(device_node, struct device_node *, if (_T) of_node_put(_T))
>>
>> If (!IS_ERR(_T))
>>
> 
> You're right, fixing DEFINE_FREE(device_node, ...) is the proper way
> to handle this:
> if (_T && !IS_ERR(_T)) of_node_put(_T)

This would be intrusive because it effectively changes the cleanup action.
A similar case[1] was handled by ensuring only NULL pointer was returned
on error.  And, this is actually what i2c_of_probe_get_i2c_node()[2] does
now.

[1] https://lore.kernel.org/all/Zw-VkQ3di5nFHiXB@smile.fi.intel.com/
[2] https://elixir.bootlin.com/linux/v7.0/source/drivers/i2c/i2c-core-of-prober.c#L38-L58

BTW, even if the cleanup action needs to be changed, the 'if' condition
should be '!IS_ERR_OR_NULL(_T)'.

> 
> This is a better fix than handling it only in this driver.
> 
> I'll rework the patch based on your suggestion and send v2 later.
> 
> Thanks,
> Guangshuo

-- 
Regards,
Liu Ying