linux-kernel - Re: [PATCH 4.19 35/48] batman-adv: Fix refcnt leak in batadv_store_throughput

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Date:   Wed, 13 May 2020 23:03:11 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>,
        Sven Eckelmann <sven@...fation.org>,
        Simon Wunderlich <sw@...onwunderlich.de>
Subject: Re: [PATCH 4.19 35/48] batman-adv: Fix refcnt leak in
 batadv_store_throughput_override

Hi!

> From: Xiyu Yang <xiyuyang19@...an.edu.cn>
> 
> commit 6107c5da0fca8b50b4d3215e94d619d38cc4a18c upstream.
> 
> batadv_show_throughput_override() invokes batadv_hardif_get_by_netdev(),
> which gets a batadv_hard_iface object from net_dev with increased refcnt
> and its reference is assigned to a local pointer 'hard_iface'.
> 
> When batadv_store_throughput_override() returns, "hard_iface" becomes
> invalid, so the refcount should be decreased to keep refcount balanced.
> 
> The issue happens in one error path of
> batadv_store_throughput_override(). When batadv_parse_throughput()
> returns NULL, the refcnt increased by batadv_hardif_get_by_netdev() is
> not decreased, causing a refcnt leak.
> 
> Fix this issue by jumping to "out" label when batadv_parse_throughput()
> returns NULL.

Ok, this fixes the issue, but it brings up a question:


> --- a/net/batman-adv/sysfs.c
> +++ b/net/batman-adv/sysfs.c
> @@ -1093,7 +1093,7 @@ static ssize_t batadv_store_throughput_o
>  	ret = batadv_parse_throughput(net_dev, buff, "throughput_override",
>  				      &tp_override);
>  	if (!ret)
> -		return count;
> +		goto out;
>

If parsing of value from userspace failed we are currently returning
success. That seems wrong. Should we return -EINVAL instead?

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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