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

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Message-ID: <Z4UK7__tlAZrucRd@shell.armlinux.org.uk>
Date: Mon, 13 Jan 2025 12:45:35 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Ma Ke <make24@...as.ac.cn>
Cc: sumit.garg@...aro.org, gregkh@...uxfoundation.org, elder@...nel.org,
	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 Wed, Jan 08, 2025 at 11:30:49AM +0800, 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'.

I reviewed a previous version of this patch, and commented about the
commit message:

 The commit message is not quite correct:

 "After calling device_register(), the correct way to dispose of the
 device is to call put_device() as per the device_register()
 documentation rather than kfree()."

Alex Elder also commented about this. Please fix the commit message.
What device_add() doesn't matter, this code isn't calling device_add(),
it's calling device_register(), and the comments against
device_register() should be appearing in the commit message, not
the comments against device_add().

Thanks.

> 
> 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>
> ---
> 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;
>  }
>  
> -- 
> 2.25.1
> 
> 

-- 
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