linux-kernel - Re: [PATCH 4.19 185/306] net: hns3: bugfix for buffer not free problem during resetting

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Date:   Fri, 29 Nov 2019 12:00:10 +0100
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Huazhong Tan <tanhuazhong@...wei.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 185/306] net: hns3: bugfix for buffer not free
 problem during resetting

Hi!

> From: Huazhong Tan <tanhuazhong@...wei.com>
> 
> [ Upstream commit 73b907a083b8a8c1c62cb494bc9fbe6ae086c460 ]
> 
> When hns3_get_ring_config()/hns3_queue_to_ring()/
> hns3_get_vector_ring_chain() failed during resetting, the allocated
> memory has not been freed before these three functions return. So
> this patch adds error handler in these functions to fix it.

Correct me if I'm wrong, but... this introduces use-after-free:

> @@ -2592,6 +2592,16 @@ static int hns3_get_vector_ring_chain(struct hns3_enet_tqp_vector *tqp_vector,
>  	}
>  
>  	return 0;
> +
> +err_free_chain:
> +	cur_chain = head->next;
> +	while (cur_chain) {
> +		chain = cur_chain->next;
> +		devm_kfree(&pdev->dev, chain);
> +		cur_chain = chain;
> +	}

Lets take two iterations:

> +		chain = cur_chain->next;
> +		devm_kfree(&pdev->dev, chain);
chain freed here.
> +		cur_chain = chain;

> +		chain = cur_chain->next;
chain->next accessed here, after free.
> +		devm_kfree(&pdev->dev, chain);
> +		cur_chain = chain;

Should it do devm_kfree(&pdev->dev, cur_chain); ?

Best regards,
									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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