From: Xin Long lucien.xin@gmail.com
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 --- net/8021q/vlan_dev.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c index cf66be83fb77..ad2d3ad34b7d 100644 --- a/net/8021q/vlan_dev.c +++ b/net/8021q/vlan_dev.c @@ -638,7 +638,12 @@ 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, @@ -851,9 +856,6 @@ 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)