linux-kernel - Re: [PATCH] fpga: stratix10-soc: fix use-after-free on s10

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Message-ID: <20190424002155.GA15154@archbook>
Date:   Tue, 23 Apr 2019 17:21:55 -0700
From:   Moritz Fischer <mdf@...nel.org>
To:     Wen Yang <wen.yang99@....com.cn>
Cc:     linux-kernel@...r.kernel.org, wang.yi59@....com.cn,
        Alan Tull <atull@...nel.org>, Moritz Fischer <mdf@...nel.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        linux-fpga@...r.kernel.org
Subject: Re: [PATCH] fpga: stratix10-soc: fix use-after-free on s10_init()

Hi Wen,

On Wed, Apr 24, 2019 at 07:32:05AM +0800, Wen Yang wrote:
> The refcount of fw_np has already been decreased by of_find_matching_node()
> so it shouldn't be used anymore.
> This patch adds an of_node_get() before of_find_matching_node() to avoid
> the use-after-free problem.
> 
> Fixes: e7eef1d7633a ("fpga: add intel stratix10 soc fpga manager driver")
> Signed-off-by: Wen Yang <wen.yang99@....com.cn>
> Cc: Alan Tull <atull@...nel.org>
> Cc: Moritz Fischer <mdf@...nel.org>
> Cc: Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
> Cc: linux-fpga@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org

Reviewed-by: Moritz Fischer <mdf@...nel.org>
> ---
>  drivers/fpga/stratix10-soc.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/fpga/stratix10-soc.c b/drivers/fpga/stratix10-soc.c
> index 13851b3..215d337 100644
> --- a/drivers/fpga/stratix10-soc.c
> +++ b/drivers/fpga/stratix10-soc.c
> @@ -507,12 +507,16 @@ static int __init s10_init(void)
>  	if (!fw_np)
>  		return -ENODEV;
>  
> +	of_node_get(fw_np);
>  	np = of_find_matching_node(fw_np, s10_of_match);
> -	if (!np)
> +	if (!np) {
> +		of_node_put(fw_np);
>  		return -ENODEV;
> +	}
>  
>  	of_node_put(np);
>  	ret = of_platform_populate(fw_np, s10_of_match, NULL, NULL);
> +	of_node_put(fw_np);
>  	if (ret)
>  		return ret;
>  
> -- 
> 2.9.5
> 

Thanks,
Moritz