vlan: move dev_put into vlan_dev_uninit

commit d6ff94afd90b0ce8d1715f8ef77d4347d7a7f2c0 upstream.

Shuang Li reported an QinQ issue by simply doing:

  # ip link add dummy0 type dummy
  # ip link add link dummy0 name dummy0.1 type vlan id 1
  # ip link add link dummy0.1 name dummy0.1.2 type vlan id 2
  # rmmod 8021q

 unregister_netdevice: waiting for dummy0.1 to become free. Usage count = 1

When rmmods 8021q, all vlan devs are deleted from their real_dev's vlan grp
and added into list_kill by unregister_vlan_dev(). dummy0.1 is unregistered
before dummy0.1.2, as it's using for_each_netdev() in __rtnl_kill_links().

When unregisters dummy0.1, dummy0.1.2 is not unregistered in the event of
NETDEV_UNREGISTER, as it's been deleted from dummy0.1's vlan grp. However,
due to dummy0.1.2 still holding dummy0.1, dummy0.1 will keep waiting in
netdev_wait_allrefs(), while dummy0.1.2 will never get unregistered and
release dummy0.1, as it delays dev_put until calling dev->priv_destructor,
vlan_dev_free().

This issue was introduced by Commit 563bcbae3ba2 ("net: vlan: fix a UAF in
vlan_dev_real_dev()"), and this patch is to fix it by moving dev_put() into
vlan_dev_uninit(), which is called after NETDEV_UNREGISTER event but before
netdev_wait_allrefs().

Fixes: 563bcbae3ba2 ("net: vlan: fix a UAF in vlan_dev_real_dev()")
Reported-by: Shuang Li <shuali@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Signed-off-by: Ivan Delalande <colona@arista.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index fefc5ed6704d3ef5e0796843c5494f88983d8b75..b7cf430006e558c7473ccc89cf02fdc075faf87d 100644 (file)
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -629,7 +629,12 @@ void vlan_dev_free_egress_priority(const struct net_device *dev)
 
 static void vlan_dev_uninit(struct net_device *dev)
 {
+       struct vlan_dev_priv *vlan = vlan_dev_priv(dev);
+
        vlan_dev_free_egress_priority(dev);
+
+       /* Get rid of the vlan's reference to real_dev */
+       dev_put(vlan->real_dev);
 }
 
 static netdev_features_t vlan_dev_fix_features(struct net_device *dev,
@@ -821,9 +826,6 @@ static void vlan_dev_free(struct net_device *dev)
 
        free_percpu(vlan->vlan_pcpu_stats);
        vlan->vlan_pcpu_stats = NULL;
-
-       /* Get rid of the vlan's reference to real_dev */
-       dev_put(vlan->real_dev);
 }
 
 void vlan_setup(struct net_device *dev)