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BUG: KCSAN: data-race in device_del / mm_update_next_owner

write to 0xffff8881037c4064 of 4 bytes by task 9811 on cpu 1:
 memalloc_noio_restore include/linux/sched/mm.h:211 [inline]
 device_del+0x9d0/0xa20 drivers/base/core.c:3131
 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:1119
 ipip_exit_batch_net+0x2a/0x30 net/ipv4/ipip.c:650
 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 0xffff8881037c4064 of 4 bytes by task 3835 on cpu 0:
 mm_update_next_owner+0x1e9/0x4c0 kernel/exit.c:387
 exit_mm+0x2b5/0x320 kernel/exit.c:482
 do_exit+0x3c2/0x15a0 kernel/exit.c:793
 do_group_exit+0x16f/0x170 kernel/exit.c:903
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:914
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:912
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:912
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3835 Comm: syz-executor.1 Not tainted 5.10.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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