linux-kernel - [PATCH 4.9 21/90] batman-adv: Fix refcnt leak in batadv_store_throughput

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Message-Id: <20200518173455.473188193@linuxfoundation.org>
Date:   Mon, 18 May 2020 19:35:59 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.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: [PATCH 4.9 21/90] batman-adv: Fix refcnt leak in batadv_store_throughput_override

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.

Fixes: 0b5ecc6811bd ("batman-adv: add throughput override attribute to hard_ifaces")
Signed-off-by: Xiyu Yang <xiyuyang19@...an.edu.cn>
Signed-off-by: Xin Tan <tanxin.ctf@...il.com>
Signed-off-by: Sven Eckelmann <sven@...fation.org>
Signed-off-by: Simon Wunderlich <sw@...onwunderlich.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/batman-adv/sysfs.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/batman-adv/sysfs.c
+++ b/net/batman-adv/sysfs.c
@@ -1087,7 +1087,7 @@ static ssize_t batadv_store_throughput_o
 	ret = batadv_parse_throughput(net_dev, buff, "throughput_override",
 				      &tp_override);
 	if (!ret)
-		return count;
+		goto out;

 	old_tp_override = atomic_read(&hard_iface->bat_v.throughput_override);
 	if (old_tp_override == tp_override)