linux-kernel - Re: [PATCH v4 2/3] mtd: rawnand: jz4780: fix possible object reference leak

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Message-ID: <20190207135332.4ef588d8@xps13>
Date:   Thu, 7 Feb 2019 13:53:32 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Wen Yang <yellowriver2010@...mail.com>
Cc:     "bbrezillon@...nel.org" <bbrezillon@...nel.org>,
        "tudor.ambarus@...rochip.com" <tudor.ambarus@...rochip.com>,
        "richard@....at" <richard@....at>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "computersforpeace@...il.com" <computersforpeace@...il.com>,
        "marek.vasut@...il.com" <marek.vasut@...il.com>,
        "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "ludovic.desroches@...rochip.com" <ludovic.desroches@...rochip.com>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/3] mtd: rawnand: jz4780: fix possible object
 reference leak

Hi Wen,

Wen Yang <yellowriver2010@...mail.com> wrote on Thu, 7 Feb 2019
12:02:45 +0000:

> of_find_device_by_node() takes a reference to the struct device
> when it finds a match via get_device, there is no need to call
> get_device() twice.
> We also should make sure to drop the reference to the device
> taken by of_find_device_by_node() on driver unbind.
> 
> Fixes: ae02ab00aa3c ("mtd: nand: jz4780: driver for NAND devices on JZ4780 SoCs")
> Signed-off-by: Wen Yang <yellowriver2010@...mail.com>
> ---
> v4->v3: Add people in Cc and remove all lines.
> v3->v2: Avoid two times of calling grtform_get_drvdata()
> v2->v1: Since there is the only one user, let's remove the err_put_device label.
> 
>  drivers/mtd/nand/raw/jz4780_bch.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/jz4780_bch.c b/drivers/mtd/nand/raw/jz4780_bch.c
> index 7201827..7aab851 100644
> --- a/drivers/mtd/nand/raw/jz4780_bch.c
> +++ b/drivers/mtd/nand/raw/jz4780_bch.c
> @@ -281,12 +281,14 @@ static struct jz4780_bch *jz4780_bch_get(struct device_node *np)
>  	struct jz4780_bch *bch;
>  
>  	pdev = of_find_device_by_node(np);
> -	if (!pdev || !platform_get_drvdata(pdev))
> +	if (!pdev)
>  		return ERR_PTR(-EPROBE_DEFER);
> -
> -	get_device(&pdev->dev);
> -

Please keep one blank line here.

>  	bch = platform_get_drvdata(pdev);
> +	if (!bch) {
> +		put_device(&pdev->dev);
> +		return ERR_PTR(-EPROBE_DEFER);
> +	}
> +
>  	clk_prepare_enable(bch->clk);
>  
>  	return bch;


Thanks,
Miquèl