linux-kernel - Re: [PATCH] spmi: hisi-spmi-controller: manage the OF node reference in device initialization and cleanup

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Message-ID: <da0122c8-20b9-4b8c-8de0-ed6d40aaa620@kernel.org>
Date: Tue, 17 Dec 2024 11:55:22 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Joe Hattori <joe@...is.s.u-tokyo.ac.jp>, mchehab+huawei@...nel.org,
 sboyd@...nel.org
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH] spmi: hisi-spmi-controller: manage the OF node reference
 in device initialization and cleanup

On 17/12/2024 05:26, Joe Hattori wrote:
> spmi_controller_probe() increments the refcount of an OF node, but does
> not release it. Instead, call of_node_get() in spmi_controller_alloc()
> and release it in spmi_ctrl_release() to avoid the reference leak.
> 
> This bug was found by an experimental static analysis tool that I am
> developing.
> 
> Fixes: e562cf3aea3e ("spmi: hisi-spmi-controller: move driver from staging")
> Signed-off-by: Joe Hattori <joe@...is.s.u-tokyo.ac.jp>
> ---
>  drivers/spmi/hisi-spmi-controller.c | 1 -
>  drivers/spmi/spmi.c                 | 3 ++-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/spmi/hisi-spmi-controller.c b/drivers/spmi/hisi-spmi-controller.c
> index 3cafdf22c909..dd21c5d1ca83 100644
> --- a/drivers/spmi/hisi-spmi-controller.c
> +++ b/drivers/spmi/hisi-spmi-controller.c
> @@ -301,7 +301,6 @@ static int spmi_controller_probe(struct platform_device *pdev)
>  	spin_lock_init(&spmi_controller->lock);
>  
>  	ctrl->dev.parent = pdev->dev.parent;
> -	ctrl->dev.of_node = of_node_get(pdev->dev.of_node);
>  
>  	/* Callbacks */
>  	ctrl->read_cmd = spmi_read_cmd;
> diff --git a/drivers/spmi/spmi.c b/drivers/spmi/spmi.c
> index fb0101da1485..e662a7a78df2 100644
> --- a/drivers/spmi/spmi.c
> +++ b/drivers/spmi/spmi.c
> @@ -36,6 +36,7 @@ static void spmi_ctrl_release(struct device *dev)
>  	struct spmi_controller *ctrl = to_spmi_controller(dev);
>  
>  	ida_free(&ctrl_ida, ctrl->nr);
> +	of_node_put(dev->of_node);


Aren't other drivers like PMIC arbiter overwriting this with different
value, thus basically you are dropping reference which was not obtained
and causing actual use-after-free?


Best regards,
Krzysztof