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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Clear (ClamAV 1.4.3/28103/Tue Aug 25 08:27:08 2026) On 8/25/26 5:21 PM, Khawar Ahemad wrote: > syzbot reported a circular locking dependency involving &net->xdp.lock, > &xs->mutex, and netdev_lock_ops(): > > -> #3 (&net->xdp.lock): > xsk_notifier > unregister_netdevice_many_notify > rtnl_dellink > > -> #2 (&port->pnodes_lock / netdev_lock): > ipvlan_device_event / bond / netdev_change_features > > -> #1 (netdev_lock_ops): > xsk_bind (holds xs->mutex, takes netdev_lock_ops(dev)) > > -> #0 (&xs->mutex): > xsk_diag_dump (holds net->xdp.lock, takes xs->mutex) > > In xsk_bind(), xs->mutex was acquired before dev_get_by_index() and > netdev_lock_ops(dev). However, in netdev notifier callbacks like > xsk_notifier(), netdev_lock_ops(dev) is held by the netdev core while > taking net->xdp.lock and then xs->mutex, creating an ABBA lock > inversion between xs->mutex and netdev_lock_ops(dev). > > Fix this by looking up the target net_device and acquiring > netdev_lock_ops(dev) before acquiring xs->mutex in xsk_bind(). This > aligns xsk_bind() with the global lock hierarchy: > rtnl_lock -> netdev_lock_ops(dev) -> net->xdp.lock -> xs->mutex. > > Fixes: 978939c08db1 ("xsk: use netdev_lock_ops in xsk_bind") > Reported-by: syzbot+aa48b5fe7bfda62d1682@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=aa48b5fe7bfda62d1682 > Signed-off-by: Khawar Ahemad This creates a deadlock with the change in the following: - xsk_bind() takes dev->lock -> xs->mutex - xsk_notifier() -> xp_clear_dev() takes xs->mutex -> dev->lock ... also Fixes tag does not exist.