linux-kernel - Re: [PATCH v4] [ARM] fix reference leak in locomo_init_one

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Message-ID: <229506bf-e675-4f17-b1fa-f9f7d62fcd45@ieee.org>
Date: Wed, 8 Jan 2025 21:06:16 -0600
From: Alex Elder <elder@...e.org>
To: Ma Ke <make24@...as.ac.cn>, linux@...linux.org.uk, sumit.garg@...aro.org,
 gregkh@...uxfoundation.org, elder@...nel.org
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH v4] [ARM] fix reference leak in locomo_init_one_child()

On 1/7/25 9:30 PM, Ma Ke wrote:
> Once device_register() failed, we should call put_device() to
> decrement reference count for cleanup. Or it could cause memory leak.
> 
> device_register() includes device_add(). As comment of device_add()
> says, 'if device_add() succeeds, you should call device_del() when you
> want to get rid of it. If device_add() has not succeeded, use only
> put_device() to drop the reference count'.

And above device_register() it says:

  * NOTE: _Never_ directly free @dev after calling this function, even
  * if it returned an error! Always use put_device() to give up the
  * reference initialized in this function instead.

> Found by code review.
> 
> Cc: stable@...r.kernel.org
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Ma Ke <make24@...as.ac.cn>

Looks good to me.  Much cleaner result.

Reviewed-by: Alex Elder <elder@...nel.org>

> ---
> Changes in v4:
> - deleted the redundant initialization;
> Changes in v3:
> - modified the patch as suggestions;
> Changes in v2:
> - modified the patch as suggestions.
> ---
>   arch/arm/common/locomo.c | 13 +++++--------
>   1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/arm/common/locomo.c b/arch/arm/common/locomo.c
> index cb6ef449b987..45106066a17f 100644
> --- a/arch/arm/common/locomo.c
> +++ b/arch/arm/common/locomo.c
> @@ -223,10 +223,8 @@ locomo_init_one_child(struct locomo *lchip, struct locomo_dev_info *info)
>   	int ret;
>   
>   	dev = kzalloc(sizeof(struct locomo_dev), GFP_KERNEL);
> -	if (!dev) {
> -		ret = -ENOMEM;
> -		goto out;
> -	}
> +	if (!dev)
> +		return -ENOMEM;
>   
>   	/*
>   	 * If the parent device has a DMA mask associated with it,
> @@ -254,10 +252,9 @@ locomo_init_one_child(struct locomo *lchip, struct locomo_dev_info *info)
>   			NO_IRQ : lchip->irq_base + info->irq[0];
>   
>   	ret = device_register(&dev->dev);
> -	if (ret) {
> - out:
> -		kfree(dev);
> -	}
> +	if (ret)
> +		put_device(&dev->dev);
> +
>   	return ret;
>   }
>