Re: [PATCH v3 3/5] phy: rockchip: phy-rockchip-typec: Add DRM AUX bridge

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Double-free and reference count underflow of the `child_np` device tree node reference due to conflicting ownership with `drm_aux_bridge_register_from_node()`.
--

--- Patch [3]: [PATCH v3 3/5] phy: rockchip: phy-rockchip-typec: Add DRM AUX bridge ---
commit 7121c384753e095d5a040f2bd93021b7ae8110d7
Author: Chaoyi Chen <chaoyi.chen@rock-chips.com>

phy: rockchip: phy-rockchip-typec: Add DRM AUX bridge
    
Using the DRM_AUX_BRIDGE helper to create the transparent DRM bridge
device.

> diff --git a/drivers/phy/rockchip/phy-rockchip-typec.c b/drivers/phy/rockchip/phy-rockchip-typec.c
> index d9701b6106d55..48070b50416e5 100644
> --- a/drivers/phy/rockchip/phy-rockchip-typec.c
> +++ b/drivers/phy/rockchip/phy-rockchip-typec.c
> @@ -1162,16 +1163,24 @@ static int rockchip_typec_phy_probe(struct platform_device *pdev)
>  
>  	for_each_available_child_of_node(np, child_np) {
>  		struct phy *phy;
> +		ret = 0;
>  
> -		if (of_node_name_eq(child_np, "dp-port"))
> +		if (of_node_name_eq(child_np, "dp-port")) {
>  			phy = devm_phy_create(dev, child_np,
>  					      &rockchip_dp_phy_ops);
> -		else if (of_node_name_eq(child_np, "usb3-port"))
> +			ret = drm_aux_bridge_register_from_node(dev, child_np);
> +		} else if (of_node_name_eq(child_np, "usb3-port"))
>  			phy = devm_phy_create(dev, child_np,
>  					      &rockchip_usb3_phy_ops);
>  		else
>  			continue;
>  
> +		if (ret) {
> +			pm_runtime_disable(dev);
> +			of_node_put(child_np);

[Severity: High]
Does this cause a reference count underflow for the child_np device node?

drm_aux_bridge_register_from_node() assigns the node to an auxiliary device,
and its error and release paths in drm/bridge/aux-bridge.c unconditionally
call of_node_put() to drop the reference.

However, the for_each_available_child_of_node() iterator owns the reference
to child_np during this loop iteration. Passing it to
drm_aux_bridge_register_from_node() without acquiring an additional reference
via of_node_get() appears to hand off a reference the bridge doesn't own.

If drm_aux_bridge_register_from_node() succeeds, the loop advances and drops
the iterator's reference, leading to a double-put when the bridge is
eventually released.

If drm_aux_bridge_register_from_node() fails, it drops the reference
internally. The explicit of_node_put(child_np) here in the error block would
then cause an immediate double-put.

> +			return ret;
> +		}

[ ... ]

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260717072323.96-1-kernel@airkyi.com?part=3

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