Subject: [PATCH AUTOSEL 4.14 05/39] batman-adv: Fix refcnt leak in batadv_show_throughput_override

From: Sasha Levin <[email-masked]>
Date: Thu, 14 May 2020 14:54:22 -0400

From: Xiyu Yang <[email-masked]>

[ 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 <[email-masked]>
Signed-off-by: Xin Tan <[email-masked]>
Signed-off-by: Sven Eckelmann <[email-masked]>
Signed-off-by: Simon Wunderlich <[email-masked]>
Signed-off-by: Sasha Levin <[email-masked]>
---
 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 2ef9b136fc394..e44a7f29d598e 100644
--- a/net/batman-adv/sysfs.c
+++ b/net/batman-adv/sysfs.c
@@ -1114,6 +1114,7 @@ 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