netdev - [PATCH net-next 1/3] net: ipvlan: fix potential UAF problem for phy

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Date:   Mon, 14 Mar 2022 19:12:12 +0800
From:   Ziyang Xuan <william.xuanziyang@...wei.com>
To:     <davem@...emloft.net>, <kuba@...nel.org>, <netdev@...r.kernel.org>
CC:     <edumazet@...gle.com>, <sakiwit@...il.com>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH net-next 1/3] net: ipvlan: fix potential UAF problem for phy_dev

Add the reference operation to phy_dev of ipvlan to avoid
the potential UAF problem under the following known scenario:

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

That likes as the scenario occurred by
commit 563bcbae3ba2 ("net: vlan: fix a UAF in vlan_dev_real_dev()").

Signed-off-by: Ziyang Xuan <william.xuanziyang@...wei.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