[PATCH net] macsec: use after free when deleting the underlying device

[Sabrina Dubroca]

macsec_notify() loops over the list of macsec devices configured on the
underlying device when this device is being removed.  This list is part
of the rx_handler data.

However, macsec_dellink unregisters the rx_handler and frees the
rx_handler data when the last macsec device is removed from the
underlying device.

Add macsec_common_dellink() to delete macsec devices without
unregistering the rx_handler and freeing the associated data.

Fixes: 960d5848dbf1 ("macsec: fix memory leaks around rx_handler 
(un)registration")
Signed-off-by: Sabrina Dubroca <s...@queasysnail.net>
---
 drivers/net/macsec.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index d13e6e15d7b5..dbd590a8177f 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -3047,22 +3047,29 @@ static void macsec_del_dev(struct macsec_dev *macsec)
        }
 }
 
+static void macsec_common_dellink(struct net_device *dev, struct list_head 
*head)
+{
+       struct macsec_dev *macsec = macsec_priv(dev);
+
+       unregister_netdevice_queue(dev, head);
+       list_del_rcu(&macsec->secys);
+       macsec_del_dev(macsec);
+
+       macsec_generation++;
+}
+
 static void macsec_dellink(struct net_device *dev, struct list_head *head)
 {
        struct macsec_dev *macsec = macsec_priv(dev);
        struct net_device *real_dev = macsec->real_dev;
        struct macsec_rxh_data *rxd = macsec_data_rtnl(real_dev);
 
-       macsec_generation++;
+       macsec_common_dellink(dev, head);
 
-       unregister_netdevice_queue(dev, head);
-       list_del_rcu(&macsec->secys);
        if (list_empty(&rxd->secys)) {
                netdev_rx_handler_unregister(real_dev);
                kfree(rxd);
        }
-
-       macsec_del_dev(macsec);
 }
 
 static int register_macsec_dev(struct net_device *real_dev,
@@ -3382,8 +3389,12 @@ static int macsec_notify(struct notifier_block *this, 
unsigned long event,
 
                rxd = macsec_data_rtnl(real_dev);
                list_for_each_entry_safe(m, n, &rxd->secys, secys) {
-                       macsec_dellink(m->secy.netdev, &head);
+                       macsec_common_dellink(m->secy.netdev, &head);
                }
+
+               netdev_rx_handler_unregister(real_dev);
+               kfree(rxd);
+
                unregister_netdevice_many(&head);
                break;
        }
-- 
2.9.2