In the Linux kernel, the following vulnerability has been resolved:
wireguard: device: use exit_rtnl callback instead of manual rtnl_lock in pre_exit
wg_netns_pre_exit() manually acquires rtnl_lock() inside the pernet .pre_exit callback. This causes a hung task when another thread holds rtnl_mutex - the cleanup_net workqueue (or the setup_net failure rollback path) blocks indefinitely in wg_netns_pre_exit() waiting to acquire the lock.
Convert to .exit_rtnl, introduced in commit 7a60d91c690b ("net: Add ->exit_rtnl() hook to struct pernet_operations."), where the framework already holds RTNL and batches all callbacks under a single rtnl_lock()/rtnl_unlock() pair, eliminating the contention window.
The rcu_assign_pointer(wg->creating_net, NULL) is safe to move from .pre_exit to .exit_rtnl (which runs after synchronize_rcu()) because all RCU readers of creating_net either use maybe_get_net()
- which returns NULL for a dying namespace with zero refcount - or
[ Jason: added __net_exit and __read_mostly annotations that were missing. ]