Re: [PATCH v4 3/3] mtd: rawnand: mtk: fix possible object reference leak

From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Wen Yang <yellowriver2010@hotmail.com>
Cc: "alexandre.belloni@bootlin.com" <alexandre.belloni@bootlin.com>,
	"tudor.ambarus@microchip.com" <tudor.ambarus@microchip.com>,
	"richard@nod.at" <richard@nod.at>,
	"bbrezillon@kernel.org" <bbrezillon@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"marek.vasut@gmail.com" <marek.vasut@gmail.com>,
	"ludovic.desroches@microchip.com"
	<ludovic.desroches@microchip.com>,
	"linux-mtd@lists.infradead.org" <linux-mtd@lists.infradead.org>,
	"computersforpeace@gmail.com" <computersforpeace@gmail.com>,
	"dwmw2@infradead.org" <dwmw2@infradead.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v4 3/3] mtd: rawnand: mtk: fix possible object reference leak
Date: Thu, 7 Feb 2019 13:53:55 +0100	[thread overview]
Message-ID: <20190207135355.19fa523f@xps13> (raw)
In-Reply-To: <HK0PR02MB36348C5317C4DDC7C3262FF5B2680@HK0PR02MB3634.apcprd02.prod.outlook.com>

Hi Wen,

Wen Yang <yellowriver2010@hotmail.com> wrote on Thu, 7 Feb 2019
12:02:52 +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: 1d6b1e464950 ("mtd: mediatek: driver for MTK Smart Device")
> Signed-off-by: Wen Yang <yellowriver2010@hotmail.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/mtk_ecc.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/mtd/nand/raw/mtk_ecc.c b/drivers/mtd/nand/raw/mtk_ecc.c
> index 6432bd7..db804fe 100644
> --- a/drivers/mtd/nand/raw/mtk_ecc.c
> +++ b/drivers/mtd/nand/raw/mtk_ecc.c
> @@ -267,11 +267,14 @@ static struct mtk_ecc *mtk_ecc_get(struct device_node *np)
>  	struct mtk_ecc *ecc;
>  
>  	pdev = of_find_device_by_node(np);
> -	if (!pdev || !platform_get_drvdata(pdev))
> +	if (!pdev)
>  		return ERR_PTR(-EPROBE_DEFER);
> -

Please keep this blank line.

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

Thanks,
Miquèl

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