macsec: use after free when deleting the underlying device

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 <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files 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;
         }