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

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Message-ID: <6d412b92-c076-4b34-9c88-600ca28547cd@pf.is.s.u-tokyo.ac.jp>
Date: Wed, 18 Dec 2024 12:42:01 +0900
From: Joe Hattori <joe@...is.s.u-tokyo.ac.jp>
To: Krzysztof Kozlowski <krzk@...nel.org>, 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

Thank you for your review.

On 12/17/24 19:55, Krzysztof Kozlowski wrote:
> 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?

Should have caught this one. It is actually storing the same OF node 
pointer so it doesn't cause UAF, but is very confusing anyway. Addressed 
in the v2 patch.

> 
> 
> Best regards,
> Krzysztof

Best,
Joe