batman_adv: batadv0: Removing interface: batadv_slave_1
============================================
WARNING: possible recursive locking detected
6.15.0-rc1-syzkaller-g2fe2b96c3818 #0 Not tainted
--------------------------------------------
kworker/u8:12/7050 is trying to acquire lock:
ffff0000eddb4d30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2751 [inline]
ffff0000eddb4d30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
ffff0000eddb4d30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: dev_set_allmulti+0xfc/0x218 net/core/dev_api.c:288

but task is already holding lock:
ffff0000eddb4d30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2751 [inline]
ffff0000eddb4d30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
ffff0000eddb4d30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: unregister_netdevice_many_notify+0x4b8/0x210c net/core/dev.c:11947
and the lock comparison function returns 0:

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&dev_instance_lock_key#3);
  lock(&dev_instance_lock_key#3);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

5 locks held by kworker/u8:12/7050:
 #0: ffff0000c183a148 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x674/0x1638 kernel/workqueue.c:3212
 #1: ffff8000a13c7b80 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x708/0x1638 kernel/workqueue.c:3212
 #2: ffff800093074a90 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0x148/0xa48 net/core/net_namespace.c:608
 #3: ffff8000930815a8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x20/0x2c net/core/rtnetlink.c:80
 #4: ffff0000eddb4d30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock include/linux/netdevice.h:2751 [inline]
 #4: ffff0000eddb4d30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: netdev_lock_ops include/net/netdev_lock.h:42 [inline]
 #4: ffff0000eddb4d30 (&dev_instance_lock_key#3){+.+.}-{4:4}, at: unregister_netdevice_many_notify+0x4b8/0x210c net/core/dev.c:11947

stack backtrace:
CPU: 0 UID: 0 PID: 7050 Comm: kworker/u8:12 Not tainted 6.15.0-rc1-syzkaller-g2fe2b96c3818 #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: netns cleanup_net
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (C)
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:120
 dump_stack+0x1c/0x28 lib/dump_stack.c:129
 print_deadlock_bug+0x338/0x340 kernel/locking/lockdep.c:3042
 check_deadlock kernel/locking/lockdep.c:3094 [inline]
 validate_chain kernel/locking/lockdep.c:3896 [inline]
 __lock_acquire+0x164c/0x32c4 kernel/locking/lockdep.c:5235
 lock_acquire+0x150/0x2e8 kernel/locking/lockdep.c:5866
 __mutex_lock_common+0x1f0/0x2604 kernel/locking/mutex.c:601
 __mutex_lock kernel/locking/mutex.c:746 [inline]
 mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:798
 netdev_lock include/linux/netdevice.h:2751 [inline]
 netdev_lock_ops include/net/netdev_lock.h:42 [inline]
 dev_set_allmulti+0xfc/0x218 net/core/dev_api.c:288
 macvlan_stop+0x194/0x368 drivers/net/macvlan.c:704
 __dev_close_many+0x428/0x76c net/core/dev.c:1709
 dev_close_many+0x1e0/0x474 net/core/dev.c:1734
 unregister_netdevice_many_notify+0x52c/0x210c net/core/dev.c:11949
 unregister_netdevice_many net/core/dev.c:12044 [inline]
 default_device_exit_batch+0x904/0x984 net/core/dev.c:12536
 ops_exit_list net/core/net_namespace.c:177 [inline]
 cleanup_net+0x6c4/0xa48 net/core/net_namespace.c:654
 process_one_work+0x810/0x1638 kernel/workqueue.c:3238
 process_scheduled_works kernel/workqueue.c:3319 [inline]
 worker_thread+0x97c/0xf08 kernel/workqueue.c:3400
 kthread+0x674/0x7dc kernel/kthread.c:464
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:862