linux-kernel - Re: [PATCH] ata: pata_octeon_cf: Fix refcount leak in octeon_cf

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Message-ID: <6122a113-9ea2-c3b3-153d-dac1f6a38dbb@opensource.wdc.com>
Date:   Wed, 11 May 2022 09:36:36 +0200
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Miaoqian Lin <linmq006@...il.com>,
        Sergey Shtylyov <s.shtylyov@....ru>,
        Jeff Garzik <jgarzik@...hat.com>,
        David Daney <david.daney@...ium.com>,
        linux-ide@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ata: pata_octeon_cf: Fix refcount leak in octeon_cf_probe

On 2022/05/11 8:27, Miaoqian Lin wrote:
> of_find_device_by_node() takes reference, we should use put_device()
> to release it when not need anymore.
> Add missing put_device() in error path to avoid refcount
> leak.
> 
> Fixes: 43f01da0f279 ("MIPS/OCTEON/ata: Convert pata_octeon_cf.c to use device tree.")
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---
>  drivers/ata/pata_octeon_cf.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/ata/pata_octeon_cf.c b/drivers/ata/pata_octeon_cf.c
> index 6b5ed3046b44..65688459acf1 100644
> --- a/drivers/ata/pata_octeon_cf.c
> +++ b/drivers/ata/pata_octeon_cf.c
> @@ -857,12 +857,14 @@ static int octeon_cf_probe(struct platform_device *pdev)
>  				res_dma = platform_get_resource(dma_dev, IORESOURCE_MEM, 0);
>  				if (!res_dma) {
>  					of_node_put(dma_node);
> +					put_device(&dma_dev->dev);
>  					return -EINVAL;
>  				}
>  				cf_port->dma_base = (u64)devm_ioremap(&pdev->dev, res_dma->start,
>  									 resource_size(res_dma));
>  				if (!cf_port->dma_base) {
>  					of_node_put(dma_node);
> +					put_device(&dma_dev->dev);
>  					return -EINVAL;
>  				}
>  

The extra reference should also be dropped at the end of the "if (dma_node)"
too, no ? Otherwise, early returns due to errors after that "if (dma_node)" will
also leak the extra ref.

Note that looking around at places where of_find_device_by_node() is being used,
very few users call put_device()... Looks like there are lots of device ref
leaks with that.

-- 
Damien Le Moal
Western Digital Research