netdev - Re: [PATCH] NetCP: Deletion of unnecessary checks before two function calls

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Date:	Thu, 5 Feb 2015 15:01:38 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Wingman Kwok <w-kwok2@...com>
Cc:	SF Markus Elfring <elfring@...rs.sourceforge.net>,
	Murali Karicheri <m-karicheri2@...com>,
	Wingman Kwok <w-kwok2@...com>, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	kernel-janitors@...r.kernel.org,
	Julia Lawall <julia.lawall@...6.fr>
Subject: Re: [PATCH] NetCP: Deletion of unnecessary checks before two
 function calls

Hi Wingman,

There are some bugs in this error handling.

On Tue, Feb 03, 2015 at 08:22:23PM +0100, SF Markus Elfring wrote:
> diff --git a/drivers/net/ethernet/ti/netcp_ethss.c b/drivers/net/ethernet/ti/netcp_ethss.c
> index fa1041a..cbd6dde 100644
> --- a/drivers/net/ethernet/ti/netcp_ethss.c
> +++ b/drivers/net/ethernet/ti/netcp_ethss.c
> @@ -2010,12 +2010,10 @@ static int gbe_probe(struct netcp_device *netcp_device, struct device *dev,
>  quit:
>  	if (gbe_dev->hw_stats)
>  		devm_kfree(dev, gbe_dev->hw_stats);
> -	if (gbe_dev->ale)
> -		cpsw_ale_destroy(gbe_dev->ale);
> +	cpsw_ale_destroy(gbe_dev->ale);
>  	if (gbe_dev->ss_regs)
>  		devm_iounmap(dev, gbe_dev->ss_regs);
> -	if (interfaces)
> -		of_node_put(interfaces);
> +	of_node_put(interfaces);
                    ^^^^^^^^^^
"interfaces" is sometimes unintialized in this code.  I don't know why
GCC doesn't catch this...  :(

This is a "one rrr bug", which is caused because you just have one error
label "quit" which handles all the error handling.  Please read my
Google+ comment on error handling.

https://plus.google.com/106378716002406849458/posts/dnanfhQ4mHQ

>  	devm_kfree(dev, gbe_dev);
        ^^^^^^^^^^^^^^^^^^^^^^^^
This is not the right way to use the devm_ interface.  These things are
freed automatically on error or when we are done with them.  This driver
is double freeing pretty much everything.  Grep for devm_kfree() and
fix everything.

I don't know why kbuild didn't catch this...

regards
dan carpenter

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