linux-kernel - Re: [PATCH v3] i2c: busses/i2c-pxa.c: fix potential null pointer dereference error

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Date:	Thu, 21 Mar 2013 11:54:29 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Cong Ding <dinggnu@...il.com>
Cc:	Haojian Zhuang <haojian.zhuang@...il.com>,
	Kyungmin Park <kmpark@...radead.org>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Karol Lewandowski <k.lewandowsk@...sung.com>,
	Haojian Zhuang <haojian.zhuang@...vell.com>,
	linux-i2c@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] i2c: busses/i2c-pxa.c: fix potential null pointer
 dereference error

On Thu, Feb 14, 2013 at 12:28:18PM +0100, Cong Ding wrote:
> If it goes to eclk through line 1107, the variable res would be NULL. It will
> cause a null pointer dereference error if we call release_mem_region. The
> correct way should be using devm_kzalloc rather than kzalloc to allocate
> memory.
> 
> Signed-off-by: Cong Ding <dinggnu@...il.com>
> ---
>  drivers/i2c/busses/i2c-pxa.c |   22 ++++++++--------------
>  1 file changed, 8 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-pxa.c b/drivers/i2c/busses/i2c-pxa.c
> index 1034d93..dd2d640 100644
> --- a/drivers/i2c/busses/i2c-pxa.c
> +++ b/drivers/i2c/busses/i2c-pxa.c
> @@ -1094,29 +1094,23 @@ static int i2c_pxa_probe(struct platform_device *dev)
>  	struct resource *res = NULL;
>  	int ret, irq;
>  
> -	i2c = kzalloc(sizeof(struct pxa_i2c), GFP_KERNEL);
> -	if (!i2c) {
> -		ret = -ENOMEM;
> -		goto emalloc;
> -	}
> +	i2c = devm_kzalloc(sizeof(struct pxa_i2c), GFP_KERNEL);

You are using devm_kzalloc here but plain kfree is used later. This
won't work.

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