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

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Message-id: <20180330033933.GA26489@ubuntu>
Date:   Fri, 30 Mar 2018 12:39:33 +0900
From:   Ji-Hun Kim <ji_hun.kim@...sung.com>
To:     Jia-Ju Bai <baijiaju1990@...il.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 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. 

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

Would freeing in the vnt_start() be better instead of freeing in
device_init_rd0_ring function?

Best regards,
Ji-Hun