netdev - [PATCH net] net: lapbether: fix issue of dev reference count leakage in lapbeth_device

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Date:   Thu, 3 Nov 2022 17:05:37 +0800
From:   Zhengchao Shao <shaozhengchao@...wei.com>
To:     <linux-x25@...r.kernel.org>, <netdev@...r.kernel.org>,
        <ms@....tdt.de>, <davem@...emloft.net>, <edumazet@...gle.com>,
        <kuba@...nel.org>, <pabeni@...hat.com>
CC:     <weiyongjun1@...wei.com>, <yuehaibing@...wei.com>,
        <shaozhengchao@...wei.com>
Subject: [PATCH net] net: lapbether: fix issue of dev reference count leakage in lapbeth_device_event()

When following tests are performed, it will cause dev reference counting
leakage.
a)ip link add bond2 type bond mode balance-rr
b)ip link set bond2 up
c)ifenslave -f bond2 rose1
d)ip link del bond2

When new bond device is created, the default type of the bond device is
ether. And the bond device is up, lapbeth_device_event() receives the
message and creates a new lapbeth device. In this case, the reference
count value of dev is hold once. But after "ifenslave -f bond2 rose1"
command is executed, the type of the bond device is changed to rose. When
the bond device is unregistered, lapbeth_device_event() will not put the
dev reference count.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
---
 drivers/net/wan/lapbether.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/wan/lapbether.c b/drivers/net/wan/lapbether.c
index 960f1393595c..cb360dca3250 100644
--- a/drivers/net/wan/lapbether.c
+++ b/drivers/net/wan/lapbether.c
@@ -446,7 +446,7 @@ static int lapbeth_device_event(struct notifier_block *this,
 	if (dev_net(dev) != &init_net)
 		return NOTIFY_DONE;

-	if (!dev_is_ethdev(dev))
+	if (!dev_is_ethdev(dev) && !lapbeth_get_x25_dev(dev))
 		return NOTIFY_DONE;

 	switch (event) {
-- 
2.17.1