linux-kernel - Re: [PATCH] HID: axff: add cleanup allocated struct axff

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Message-ID: <fv32i2ejsupm64mpadzsfudaeuzkavkazpmnn2e4ijqeobl4gs@porr2zpxn4aj>
Date: Mon, 18 Aug 2025 10:20:17 -0700
From: Dmitry Torokhov <dtor@...l.ru>
To: Jeongjun Park <aha310510@...il.com>
Cc: jikos@...nel.org, bentiss@...nel.org, x0r@...life.ru, 
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: axff: add cleanup allocated struct axff_device heap

Hi Jeongjun,

On Tue, Aug 19, 2025 at 12:43:02AM +0900, Jeongjun Park wrote:
> Currently, acrux hid driver allocates heap memory equal to
> sizeof(struct axff_device) to support force feedback, but there's no code
> to free this memory except when initialization fails. This causes the
> allocated memory to not be freed even if the driver is detached.
> 
> Therefore, to properly clean up and safely manage the allocated heap,
> must be modified to use devm_kzalloc().

You have not tested this, have you? The private data that is passed to
input_ff_create_memless() is freed by ml_ff_destroy() which is invoked
when input core calls input_ff_destroy() as part of input device
teardown. Your change introduces double-free. 

> 
> Fixes: c0dbcc33c652 ("HID: add ACRUX game controller force feedback support")
> Signed-off-by: Jeongjun Park <aha310510@...il.com>
> ---
>  drivers/hid/hid-axff.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/hid/hid-axff.c b/drivers/hid/hid-axff.c
> index fbe4e16ab029..b8202737f4c8 100644
> --- a/drivers/hid/hid-axff.c
> +++ b/drivers/hid/hid-axff.c
> @@ -96,7 +96,7 @@ static int axff_init(struct hid_device *hid)
>  		return -ENODEV;
>  	}
>  
> -	axff = kzalloc(sizeof(struct axff_device), GFP_KERNEL);
> +	axff = devm_kzalloc(&hid->dev, sizeof(struct axff_device), GFP_KERNEL);
>  	if (!axff)
>  		return -ENOMEM;
>  
> @@ -104,7 +104,7 @@ static int axff_init(struct hid_device *hid)
>  
>  	error = input_ff_create_memless(dev, axff, axff_play);
>  	if (error)
> -		goto err_free_mem;
> +		return error;
>  
>  	axff->report = report;
>  	hid_hw_request(hid, axff->report, HID_REQ_SET_REPORT);
> @@ -112,10 +112,6 @@ static int axff_init(struct hid_device *hid)
>  	hid_info(hid, "Force Feedback for ACRUX game controllers by Sergei Kolzun <x0r@...life.ru>\n");
>  
>  	return 0;
> -
> -err_free_mem:
> -	kfree(axff);
> -	return error;
>  }
>  #else
>  static inline int axff_init(struct hid_device *hid)
> --
> 

Thanks.

-- 
Dmitry