netdev - Re: [PATCH] net: ethernet: enetc: Add missing put

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Date:   Tue, 19 Apr 2022 10:22:34 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Yihao Han <hanyihao@...o.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     kernel@...o.com
Subject: Re: [PATCH] net: ethernet: enetc: Add missing put_device() call

On Fri, 2022-04-15 at 06:36 -0700, Yihao Han wrote:
> A coccicheck run provided information like the following.
> 
> drivers/net/ethernet/freescale/enetc/enetc_pf.c:1180:1-7:
> ERROR: missing put_device; call of_find_device_by_node
> on line 1174, but without a corresponding object release
> within this function.
> 
> Generated by: scripts/coccinelle/free/put_device.cocci
> 
> Signed-off-by: Yihao Han <hanyihao@...o.com>
> ---
>  drivers/net/ethernet/freescale/enetc/enetc_pf.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc_pf.c b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
> index a0c75c717073..d6e18afda69a 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc_pf.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc_pf.c
> @@ -1177,6 +1177,7 @@ static int enetc_pf_register_with_ierb(struct pci_dev *pdev)
>  	if (!ierb_pdev)
>  		return -EPROBE_DEFER;
>  
> +	put_device(ierb_pdev);

put_device() gets a 'struct device' argument, e.g. ierb_pdev->dev.

Have a look at the patchwork checks they catch this sort of issue.

>  	return enetc_ierb_register_pf(ierb_pdev, pdev);

enetc_ierb_register_pf() uses/dereference ierb_pdev, you need to
release the device reference after the above call, or you may hit UaF,
I guess.

Thanks,

Paolo