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Subject: Re: [PATCH] mfd: core: fix UAF while using device of node
From:   Yang Yingliang <yangyingliang@huawei.com>
To:     <lee@kernel.org>, <krzysztof.kozlowski@canonical.com>
CC:     <linux-kernel@vger.kernel.org>
References: <20221116074116.1022139-1-yangyingliang@huawei.com>
Message-ID: <9ad01578-9982-fd55-14a3-a74bf0906165@huawei.com>
Date:   Thu, 8 Dec 2022 21:53:20 +0800
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Hi,

On 2022/11/16 15:41, Yang Yingliang wrote:
> I got the following UAF report:
>
>    refcount_t: underflow; use-after-free.
>    WARNING: CPU: 1 PID: 270 at lib/refcount.c:29 refcount_warn_saturate+0x121/0x180
>    ...
>    OF: ERROR: memory leak, expected refcount 1 instead of -1073741824,
>    of_node_get()/of_node_put() unbalanced - destroy cset entry:
>    attach overlay node /i2c/pmic@62/powerkey
>
> The of_node of device assigned in mfd_match_of_node_to_dev() need be
> get, and it will be put in platform_device_release().
>
> Fixes: 002be8114007 ("mfd: core: Add missing of_node_put for loop iteration")
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Is this patch good or do you have any suggestion ?

Thanks,
Yang
> ---
>   drivers/mfd/mfd-core.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mfd/mfd-core.c b/drivers/mfd/mfd-core.c
> index 16d1861e9682..8e57f67719cf 100644
> --- a/drivers/mfd/mfd-core.c
> +++ b/drivers/mfd/mfd-core.c
> @@ -161,7 +161,7 @@ static int mfd_match_of_node_to_dev(struct platform_device *pdev,
>   	of_entry->np = np;
>   	list_add_tail(&of_entry->list, &mfd_of_node_list);
>   
> -	pdev->dev.of_node = np;
> +	pdev->dev.of_node = of_node_get(np);
>   	pdev->dev.fwnode = &np->fwnode;
>   #endif
>   	return 0;