netdev - [PATCH net] ipvlan: hold lower dev to avoid possible use-after-free

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Message-ID: <20221116011914.96240-1-maheshb@google.com>
Date:   Tue, 15 Nov 2022 17:19:14 -0800
From:   Mahesh Bandewar <maheshb@...gle.com>
To:     Netdev <netdev@...r.kernel.org>
Cc:     Eric Dumazet <edumazet@...gle.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Mahesh Bandewar <mahesh@...dewar.net>,
        Mahesh Bandewar <maheshb@...gle.com>
Subject: [PATCH net] ipvlan: hold lower dev to avoid possible use-after-free

Recently syzkaller discovered the issue of disappearing lower
device (NETDEV_UNREGISTER) while the virtual device (like
macvlan) is still having it as a lower device. So it's just
a matter of time similar discovery will be made for IPvlan
device setup. So fixing it preemptively. Also while at it,
add a refcount tracker.

Fixes: 2ad7bf363841 ("ipvlan: Initial check-in of the IPVLAN driver.")

Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
---
 drivers/net/ipvlan/ipvlan.h      | 1 +
 drivers/net/ipvlan/ipvlan_main.c | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/drivers/net/ipvlan/ipvlan.h b/drivers/net/ipvlan/ipvlan.h
index de94921cbef9..025e0c19ec25 100644
--- a/drivers/net/ipvlan/ipvlan.h
+++ b/drivers/net/ipvlan/ipvlan.h
@@ -98,6 +98,7 @@ struct ipvl_port {
 	struct sk_buff_head	backlog;
 	int			count;
 	struct ida		ida;
+	netdevice_tracker	dev_tracker;
 };
 
 struct ipvl_skb_cb {
diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
index b6bfa9fdca62..b15dd9a3ad54 100644
--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -83,6 +83,7 @@ static int ipvlan_port_create(struct net_device *dev)
 	if (err)
 		goto err;
 
+	netdev_hold(dev, &port->dev_tracker, GFP_KERNEL);
 	return 0;
 
 err:
@@ -95,6 +96,7 @@ static void ipvlan_port_destroy(struct net_device *dev)
 	struct ipvl_port *port = ipvlan_port_get_rtnl(dev);
 	struct sk_buff *skb;
 
+	netdev_put(dev, &port->dev_tracker);
 	if (port->mode == IPVLAN_MODE_L3S)
 		ipvlan_l3s_unregister(port);
 	netdev_rx_handler_unregister(dev);
-- 
2.38.1.431.g37b22c650d-goog