linux-kernel - Re: [PATCH v3] staging: vt6655: check for memory allocation failures

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Date:   Fri, 30 Mar 2018 11:50:08 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     Ji-Hun Kim <ji_hun.kim@...sung.com>
Cc:     gregkh@...uxfoundation.org, forest@...ttletooquiet.net,
        dartnorris@...il.com, santhameena13@...il.com,
        julia.lawall@...6.fr, y.k.oh@...sung.com,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v3] staging: vt6655: check for memory allocation failures



On 2018/3/30 11:39, Ji-Hun Kim wrote:
> On Fri, Mar 30, 2018 at 11:15:03AM +0800, Jia-Ju Bai wrote:
>>
>> On 2018/3/30 10:44, Ji-Hun Kim wrote:
>>> @@ -1165,10 +1205,18 @@ static int vnt_start(struct ieee80211_hw *hw)
>>>   	}
>>>   	dev_dbg(&priv->pcid->dev, "call device init rd0 ring\n");
>>> -	device_init_rd0_ring(priv);
>>> -	device_init_rd1_ring(priv);
>>> -	device_init_td0_ring(priv);
>>> -	device_init_td1_ring(priv);
>>> +	ret = device_init_rd0_ring(priv);
>>> +	if (ret)
>>> +		goto error;
>>> +	ret = device_init_rd1_ring(priv);
>>> +	if (ret)
>>> +		goto error;
>>> +	ret = device_init_td0_ring(priv);
>>> +	if (ret)
>>> +		goto error;
>>> +	ret = device_init_td1_ring(priv);
>>> +	if (ret)
>>> +		goto error;
>>>   	device_init_registers(priv);
>>> @@ -1178,6 +1226,8 @@ static int vnt_start(struct ieee80211_hw *hw)
>>>   	ieee80211_wake_queues(hw);
>>>   	return 0;
>>> +error:
>>> +	return ret;
>>>   }
>> This code will lead to memory leaks when device_init_rd1_ring()
>> fails, because the memory allocated by device_init_rd0_ring() is not
>> freed.
>>
>> I think this one will be better:
>>      ret = device_init_rd0_ring(priv);
>>      if (ret)
>>          goto error_init_rd0_ring;
>>      ret = device_init_rd1_ring(priv);
>>      if (ret)
>>          goto error_init_rd1_ring;
>>      ret = device_init_td0_ring(priv);
>>      if (ret)
>>          goto error_init_td0_ring;
>>      ret = device_init_td1_ring(priv);
>>      if (ret)
>>          goto error_init_td1_ring;
>>      ......
>> error_init_td1_ring:
>>      device_free_td0_ring(priv);
>> error_init_td0_ring:
>>      device_free_rd1_ring(priv);
>> error_init_rd1_ring:
>>      device_free_rd0_ring(priv);
>> error_init_rd0_ring:
>>      return ret;
>>
>>
>> Best wishes,
>> Jia-Ju Bai
>>
>>
> But, those freeing function are already placed in the each device_init
> functions for allocation fail like below.

I think it is okay.
I suppose that, for each device_init function, you only free the 
resources allocated in this function, and do not handle the resources in 
other functions.

> @@ -550,20 +554,29 @@ static void device_init_rd0_ring(struct vnt_private *priv)
> +       return 0;
> +error:
> +       device_free_rd0_ring(priv);
> +       return ret;

This code is needed to free the resources allocated in this function.


Best wishes,
Jia-Ju Bai