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Date:   Mon, 27 Apr 2020 17:00:37 +0200
From:   Simon Wunderlich <sw@...onwunderlich.de>
To:     davem@...emloft.net
Cc:     netdev@...r.kernel.org, b.a.t.m.a.n@...ts.open-mesh.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 2/4] batman-adv: Fix refcnt leak in batadv_show_throughput_override

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

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>
---
 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 c45962d8527b..c0b00268aac4 100644
--- a/net/batman-adv/sysfs.c
+++ b/net/batman-adv/sysfs.c
@@ -1190,6 +1190,7 @@ 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

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