From: Ziyang Xuan william.xuanziyang@huawei.com
[ Upstream commit 01d9cc2dea3fde3bad6d27f464eff463496e2b00 ]
Inject error before dev_hold(real_dev) in register_vlan_dev(), and execute the following testcase:
ip link add dev dummy1 type dummy ip link add name dummy1.100 link dummy1 type vlan id 100 ip link del dev dummy1
When the dummy netdevice is removed, we will get a WARNING as following:
======================================================================= refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 2 PID: 0 at lib/refcount.c:31 refcount_warn_saturate+0xbf/0x1e0
and an endless loop of:
======================================================================= unregister_netdevice: waiting for dummy1 to become free. Usage count = -1073741824
That is because dev_put(real_dev) in vlan_dev_free() be called without dev_hold(real_dev) in register_vlan_dev(). It makes the refcnt of real_dev underflow.
Move the dev_hold(real_dev) to vlan_dev_init() which is the call-back of ndo_init(). That makes dev_hold() and dev_put() for vlan's real_dev symmetrical.
Fixes: 563bcbae3ba2 ("net: vlan: fix a UAF in vlan_dev_real_dev()") Reported-by: Petr Machata petrm@nvidia.com Suggested-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Ziyang Xuan william.xuanziyang@huawei.com Link: https://lore.kernel.org/r/20211126015942.2918542-1-william.xuanziyang@huawei... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/8021q/vlan.c | 3 --- net/8021q/vlan_dev.c | 3 +++ 2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c index ad3780067a7d8..d12c9a8a9953e 100644 --- a/net/8021q/vlan.c +++ b/net/8021q/vlan.c @@ -181,9 +181,6 @@ int register_vlan_dev(struct net_device *dev, struct netlink_ext_ack *extack) if (err) goto out_unregister_netdev;
- /* Account for reference in struct vlan_dev_priv */ - dev_hold(real_dev); - vlan_stacked_transfer_operstate(real_dev, dev, vlan); linkwatch_fire_event(dev); /* _MUST_ call rfc2863_policy() */
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c index c7eba7dab0938..86a1c99025ea0 100644 --- a/net/8021q/vlan_dev.c +++ b/net/8021q/vlan_dev.c @@ -606,6 +606,9 @@ static int vlan_dev_init(struct net_device *dev) if (!vlan->vlan_pcpu_stats) return -ENOMEM;
+ /* Get vlan's reference to real_dev */ + dev_hold(real_dev); + return 0; }