CVE-2026-31579

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

access net->user_ns which remains valid throughout the entire

ops_undo_list sequence.

[ Jason: added __net_exit and __read_mostly annotations that were missing. ]