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BUG: KCSAN: data-race in exit_signals / kthread_unpark

write to 0xffff888014738064 of 4 bytes by task 19516 on cpu 1:
 exit_signals+0x124/0x580 kernel/signal.c:2831
 do_exit+0x19f/0x16e0 kernel/exit.c:761
 kthread+0x215/0x230 kernel/kthread.c:293
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

read to 0xffff888014738064 of 4 bytes by task 19497 on cpu 0:
 to_kthread kernel/kthread.c:82 [inline]
 kthread_unpark+0x1f/0x150 kernel/kthread.c:510
 kthread_stop+0xa3/0x310 kernel/kthread.c:593
 kvm_mmu_pre_destroy_vm+0x2e/0x40 arch/x86/kvm/mmu/mmu.c:6396
 kvm_arch_pre_destroy_vm+0x11/0x20 arch/x86/kvm/x86.c:9986
 kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:806 [inline]
 kvm_put_kvm+0x20f/0xad0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:843
 kvm_vm_release+0x2c/0x30 arch/x86/kvm/../../../virt/kvm/kvm_main.c:866
 __fput+0x1df/0x460 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:239 [inline]
 __prepare_exit_to_usermode+0x1c6/0x230 arch/x86/entry/common.c:269
 __syscall_return_slowpath+0x47/0x60 arch/x86/entry/common.c:352
 do_syscall_64+0x5d/0xb0 arch/x86/entry/common.c:393
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 19497 Comm: syz-executor.1 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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