netdev - [PATCH AUTOSEL 4.9 05/27] batman-adv: Fix refcnt leak in batadv_show_throughput

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Message-Id: <20200514185550.21462-5-sashal@kernel.org>
Date:   Thu, 14 May 2020 14:55:28 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Xin Tan <tanxin.ctf@...il.com>,
        Sven Eckelmann <sven@...fation.org>,
        Simon Wunderlich <sw@...onwunderlich.de>,
        Sasha Levin <sashal@...nel.org>,
        b.a.t.m.a.n@...ts.open-mesh.org, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 4.9 05/27] batman-adv: Fix refcnt leak in batadv_show_throughput_override

From: Xiyu Yang <xiyuyang19@...an.edu.cn>

[ Upstream commit f872de8185acf1b48b954ba5bd8f9bc0a0d14016 ]

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_show_throughput_override() returns, "hard_iface" becomes
invalid, so the refcount should be decreased to keep refcount balanced.

The issue happens in the normal path of
batadv_show_throughput_override(), which forgets to decrease the refcnt
increased by batadv_hardif_get_by_netdev() before the function returns,
causing a refcnt leak.

Fix this issue by calling batadv_hardif_put() before the
batadv_show_throughput_override() returns in the normal path.

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: Sasha Levin <sashal@...nel.org>
---
 net/batman-adv/sysfs.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/batman-adv/sysfs.c b/net/batman-adv/sysfs.c
index 31d7e239a1fd6..d3fb5396f9473 100644
--- a/net/batman-adv/sysfs.c
+++ b/net/batman-adv/sysfs.c
@@ -1120,6 +1120,7 @@ static ssize_t batadv_show_throughput_override(struct kobject *kobj,

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

+	batadv_hardif_put(hard_iface);
 	return sprintf(buff, "%u.%u MBit\n", tp_override / 10,
 		       tp_override % 10);
 }
-- 
2.20.1