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BUG: KCSAN: data-race in device_del / mm_update_next_owner

write to 0xffff8881378c6024 of 4 bytes by task 30271 on cpu 0:
 memalloc_noio_restore include/linux/sched/mm.h:211 [inline]
 device_del+0x950/0x9a0 drivers/base/core.c:3129
 netdev_unregister_kobject+0xdb/0xf0 net/core/net-sysfs.c:1864
 rollback_registered_many+0xbd0/0xe40 net/core/dev.c:9449
 unregister_netdevice_many+0x2e/0x1a0 net/core/dev.c:10626
 ip_tunnel_delete_nets+0x24a/0x280 net/ipv4/ip_tunnel.c:1116
 vti_exit_batch_net+0x2a/0x30 net/ipv4/ip_vti.c:512
 ops_exit_list net/core/net_namespace.c:190 [inline]
 cleanup_net+0x4cc/0x8a0 net/core/net_namespace.c:604
 process_one_work+0x3e1/0x950 kernel/workqueue.c:2272
 worker_thread+0x635/0xb90 kernel/workqueue.c:2418
 kthread+0x1fa/0x220 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296

read to 0xffff8881378c6024 of 4 bytes by task 2462 on cpu 1:
 mm_update_next_owner+0x1e9/0x4c0 kernel/exit.c:387
 exit_mm+0x2ff/0x370 kernel/exit.c:485
 do_exit+0x3c2/0x15a0 kernel/exit.c:796
 do_group_exit+0xc8/0x170 kernel/exit.c:906
 get_signal+0xf9b/0x1510 kernel/signal.c:2758
 arch_do_signal+0x25/0x260 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0xde/0x170 kernel/entry/common.c:191
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2462 Comm: syz-executor.4 Not tainted 5.10.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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