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From:   Ziyang Xuan <william.xuanziyang@huawei.com>
To:     <davem@davemloft.net>, <kuba@kernel.org>, <pabeni@redhat.com>,
        <netdev@vger.kernel.org>
CC:     <edumazet@google.com>, <brianvv@google.com>,
        <linux-kernel@vger.kernel.org>
Subject: [PATCH net-next v3 1/3] net: ipvlan: fix potential UAF problem for phy_dev
Date:   Sat, 19 Mar 2022 17:52:37 +0800
Message-ID: <abef9f7ad2c6e6b8ae053225766d34f3fc930ddf.1647664114.git.william.xuanziyang@huawei.com>
In-Reply-To: <cover.1647664114.git.william.xuanziyang@huawei.com>
References: <cover.1647664114.git.william.xuanziyang@huawei.com>
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There is a known scenario can trigger UAF problem for lower
netdevice as following:

Someone module puts the NETDEV_UNREGISTER event handler to a
work, and lower netdevice is accessed in the work handler. But
when the work is excuted, lower netdevice has been destroyed
because upper netdevice did not get reference to lower netdevice
correctly.

Although it can not happen for ipvlan now because there is no
way to access phy_dev outside ipvlan. But it is necessary to
add the reference operation to phy_dev to avoid the potential
UAF problem in the future.

Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
---
 drivers/net/ipvlan/ipvlan_main.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
index 696e245f6d00..dcdc01403f22 100644
--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -158,6 +158,10 @@ static int ipvlan_init(struct net_device *dev)
 	}
 	port = ipvlan_port_get_rtnl(phy_dev);
 	port->count += 1;
+
+	/* Get ipvlan's reference to phy_dev */
+	dev_hold(phy_dev);
+
 	return 0;
 }
 
@@ -665,6 +669,14 @@ void ipvlan_link_delete(struct net_device *dev, struct list_head *head)
 }
 EXPORT_SYMBOL_GPL(ipvlan_link_delete);
 
+static void ipvlan_dev_free(struct net_device *dev)
+{
+	struct ipvl_dev *ipvlan = netdev_priv(dev);
+
+	/* Get rid of the ipvlan's reference to phy_dev */
+	dev_put(ipvlan->phy_dev);
+}
+
 void ipvlan_link_setup(struct net_device *dev)
 {
 	ether_setup(dev);
@@ -674,6 +686,7 @@ void ipvlan_link_setup(struct net_device *dev)
 	dev->priv_flags |= IFF_UNICAST_FLT | IFF_NO_QUEUE;
 	dev->netdev_ops = &ipvlan_netdev_ops;
 	dev->needs_free_netdev = true;
+	dev->priv_destructor = ipvlan_dev_free;
 	dev->header_ops = &ipvlan_header_ops;
 	dev->ethtool_ops = &ipvlan_ethtool_ops;
 }
-- 
2.25.1