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. Reported-by: syzbot+f2fbf7478a35a94c8b7c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?id=cb64c22a492202ca929e18262fdb8cb89e635c70 Signed-off-by: Shardul Bankar --- v2: Fix incorrect Reported-by email address drivers/net/wireguard/device.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/net/wireguard/device.c b/drivers/net/wireguard/device.c index 46a71ec36af8..eb854c5294a3 100644 --- a/drivers/net/wireguard/device.c +++ b/drivers/net/wireguard/device.c @@ -411,12 +411,11 @@ static struct rtnl_link_ops link_ops __read_mostly = { .newlink = wg_newlink, }; -static void wg_netns_pre_exit(struct net *net) +static void wg_netns_exit_rtnl(struct net *net, struct list_head *dev_kill_list) { struct wg_device *wg; struct wg_peer *peer; - rtnl_lock(); list_for_each_entry(wg, &device_list, device_list) { if (rcu_access_pointer(wg->creating_net) == net) { pr_debug("%s: Creating namespace exiting\n", wg->dev->name); @@ -429,11 +428,10 @@ static void wg_netns_pre_exit(struct net *net) mutex_unlock(&wg->device_update_lock); } } - rtnl_unlock(); } static struct pernet_operations pernet_ops = { - .pre_exit = wg_netns_pre_exit + .exit_rtnl = wg_netns_exit_rtnl }; int __init wg_device_init(void) -- 2.34.1