unregister_netdevice: waiting for lo to become free. Usage count = 2
leaked reference.
=====================================================
BUG: KMSAN: uninit-value in __is_kernel include/asm-generic/sections.h:224 [inline]
BUG: KMSAN: uninit-value in is_kernel include/linux/kallsyms.h:36 [inline]
BUG: KMSAN: uninit-value in is_ksym_addr include/linux/kallsyms.h:44 [inline]
BUG: KMSAN: uninit-value in kallsyms_lookup_buildid+0x1fb/0xca0 kernel/kallsyms.c:414
 __is_kernel include/asm-generic/sections.h:224 [inline]
 is_kernel include/linux/kallsyms.h:36 [inline]
 is_ksym_addr include/linux/kallsyms.h:44 [inline]
 kallsyms_lookup_buildid+0x1fb/0xca0 kernel/kallsyms.c:414
 __sprint_symbol+0x166/0x650 kernel/kallsyms.c:527
 sprint_symbol+0x80/0x90 kernel/kallsyms.c:570
 symbol_string+0x44a/0x6e0 lib/vsprintf.c:1000
 pointer+0x17af/0x2970 lib/vsprintf.c:2394
 vsnprintf+0x1d4b/0x3510 lib/vsprintf.c:2800
 vprintk_store+0x571/0x18e0 kernel/printk/printk.c:2243
 vprintk_emit+0x290/0xab0 kernel/printk/printk.c:2340
 vprintk_default+0x8a/0xa0 kernel/printk/printk.c:2370
 vprintk+0x163/0x180 kernel/printk/printk_safe.c:50
 _printk+0x191/0x1e0 kernel/printk/printk.c:2380
 stack_trace_print+0x14e/0x1e0 kernel/stacktrace.c:33
 stack_depot_print+0x59/0x60 lib/stackdepot.c:351
 ref_tracker_dir_print+0x1f9/0x390 lib/ref_tracker.c:57
 netdev_wait_allrefs_any net/core/dev.c:10268 [inline]
 netdev_run_todo+0x1138/0x18f0 net/core/dev.c:10341
 rtnl_unlock+0x17/0x20 net/core/rtnetlink.c:148
 default_device_exit_batch+0xc6e/0xd40 net/core/dev.c:11349
 ops_exit_list net/core/net_namespace.c:174 [inline]
 cleanup_net+0xd77/0x1860 net/core/net_namespace.c:606
 process_one_work+0xe73/0x18d0 kernel/workqueue.c:2289
 worker_thread+0x10fc/0x2230 kernel/workqueue.c:2436
 kthread+0x3c7/0x500 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308

Uninit was created at:
 __alloc_pages+0x926/0x10a0 mm/page_alloc.c:5572
 alloc_pages+0xb4b/0xec0
 __stack_depot_save+0x440/0x4b0 lib/stackdepot.c:474
 stack_depot_save+0x17/0x20 lib/stackdepot.c:533
 ref_tracker_alloc+0x31a/0x9a0 lib/ref_tracker.c:92
 __netns_tracker_alloc include/net/net_namespace.h:331 [inline]
 netns_tracker_alloc include/net/net_namespace.h:340 [inline]
 nf_nat_masq_schedule+0x609/0xa10 net/netfilter/nf_nat_masquerade.c:126
 masq_device_event+0x137/0x1a0 net/netfilter/nf_nat_masquerade.c:162
 notifier_call_chain kernel/notifier.c:87 [inline]
 raw_notifier_call_chain+0x11b/0x2a0 kernel/notifier.c:455
 call_netdevice_notifiers_info net/core/dev.c:1944 [inline]
 call_netdevice_notifiers_extack net/core/dev.c:1982 [inline]
 call_netdevice_notifiers net/core/dev.c:1996 [inline]
 dev_close_many+0x725/0xb40 net/core/dev.c:1530
 unregister_netdevice_many_notify+0x8e9/0x3500 net/core/dev.c:10813
 unregister_netdevice_many net/core/dev.c:10895 [inline]
 unregister_netdevice_queue+0x5a3/0x750 net/core/dev.c:10776
 unregister_netdevice include/linux/netdevice.h:3059 [inline]
 nsim_destroy+0x7e/0x240 drivers/net/netdevsim/netdev.c:374
 __nsim_dev_port_del+0x21b/0x370 drivers/net/netdevsim/dev.c:1428
 nsim_dev_port_del_all drivers/net/netdevsim/dev.c:1440 [inline]
 nsim_dev_reload_destroy+0x4ed/0x8c0 drivers/net/netdevsim/dev.c:1657
 nsim_drv_remove+0xd9/0x2f0 drivers/net/netdevsim/dev.c:1673
 nsim_bus_remove+0x3b/0x50 drivers/net/netdevsim/bus.c:246
 device_remove drivers/base/dd.c:548 [inline]
 __device_release_driver drivers/base/dd.c:1253 [inline]
 device_release_driver_internal+0x91f/0xfe0 drivers/base/dd.c:1279
 device_release_driver+0x4f/0x60 drivers/base/dd.c:1302
 bus_remove_device+0x5d9/0x6a0 drivers/base/bus.c:529
 device_del+0xbfc/0x1c00 drivers/base/core.c:3666
 device_unregister+0x3b/0x90 drivers/base/core.c:3698
 nsim_bus_dev_del drivers/net/netdevsim/bus.c:310 [inline]
 del_device_store+0x547/0x660 drivers/net/netdevsim/bus.c:219
 bus_attr_store+0x10f/0x170 drivers/base/bus.c:122
 sysfs_kf_write+0x24a/0x2c0 fs/sysfs/file.c:136
 kernfs_fop_write_iter+0x5ea/0x990 fs/kernfs/file.c:334
 call_write_iter include/linux/fs.h:2189 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0xc5c/0x1a60 fs/read_write.c:584
 ksys_write+0x28f/0x510 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __ia32_sys_write+0xdf/0x120 fs/read_write.c:646
 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
 __do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:178
 do_fast_syscall_32+0x37/0x80 arch/x86/entry/common.c:203
 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:246
 entry_SYSENTER_compat_after_hwframe+0x70/0x82

CPU: 0 PID: 2065 Comm: kworker/u4:6 Not tainted 6.2.0-rc7-syzkaller-80760-g8c89ecf5c13b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
Workqueue: netns cleanup_net
=====================================================