netdev - [PATCH AUTOSEL 4.9 06/27] batman-adv: Fix refcnt leak in batadv_store_throughput

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Date:   Thu, 14 May 2020 14:55:29 -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 06/27] batman-adv: Fix refcnt leak in batadv_store_throughput_override

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

[ Upstream commit 6107c5da0fca8b50b4d3215e94d619d38cc4a18c ]

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: Sasha Levin <sashal@...nel.org>
---
 net/batman-adv/sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/batman-adv/sysfs.c b/net/batman-adv/sysfs.c
index d3fb5396f9473..121e9e7d28cc5 100644
--- a/net/batman-adv/sysfs.c
+++ b/net/batman-adv/sysfs.c
@@ -1087,7 +1087,7 @@ static ssize_t batadv_store_throughput_override(struct kobject *kobj,
 	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)
-- 
2.20.1