WARNING: CPU: 0 PID: 4042 at kernel/kthread.c:87 free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4042 Comm: syz-executor3 Not tainted 4.14.0-rc2-mm1+ #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:52
 panic+0x1e4/0x417 kernel/panic.c:181
 __warn+0x1c4/0x1d9 kernel/panic.c:542
 report_bug+0x211/0x2d0 lib/bug.c:183
 fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:178
 do_trap_no_signal arch/x86/kernel/traps.c:212 [inline]
 do_trap+0x260/0x390 arch/x86/kernel/traps.c:261
 do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:298
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:311
 invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:905
RIP: 0010:free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
RSP: 0018:ffff8801db207768 EFLAGS: 00010206
RAX: ffff8801d1ad0200 RBX: ffff8801d562a300 RCX: 1ffff1003b640ee1
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff8801d562a488
RBP: ffff8801db207770 R08: 0000000000000000 R09: 1ffff1003b640ed4
R10: ffff8801d1ad0200 R11: 0000000000000001 R12: 1ffff1003b640ef0
R13: 1ffff1003b640ef4 R14: 0000000000000000 R15: ffff8801db2077e0
 free_task+0x134/0x1a0 kernel/fork.c:386
 __put_task_struct+0x229/0x3b0 kernel/fork.c:667
 put_task_struct include/linux/sched/task.h:95 [inline]
 delayed_put_task_struct+0xca/0x3d0 kernel/exit.c:180
 __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
 rcu_do_batch kernel/rcu/tree.c:2758 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:3012 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2979 [inline]
 rcu_process_callbacks+0xd74/0x17d0 kernel/rcu/tree.c:2996
 __do_softirq+0x29d/0xbb2 kernel/softirq.c:284
 invoke_softirq kernel/softirq.c:364 [inline]
 irq_exit+0x1d3/0x210 kernel/softirq.c:405
 exiting_irq arch/x86/include/asm/apic.h:540 [inline]
 smp_apic_timer_interrupt+0x16b/0x700 arch/x86/kernel/apic/apic.c:1041
 apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:770
 </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:777 [inline]
RIP: 0010:kfree+0xf7/0x250 mm/slab.c:3822
RSP: 0018:ffff8801d39870b0 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff11
RAX: 0000000000000007 RBX: ffff8801b4760d40 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000286
RBP: ffff8801d39870d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000286
R13: ffff8801dac02500 R14: ffffffff8192b526 R15: ffff8801b4720da8
 kvfree+0x36/0x60 mm/util.c:416
 kvm_free_memslots+0xaf/0xd0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:544
 kvm_destroy_vm arch/x86/kvm/../../../virt/kvm/kvm_main.c:730 [inline]
 kvm_put_kvm+0x916/0xde0 arch/x86/kvm/../../../virt/kvm/kvm_main.c:748
 kvm_vm_release+0x42/0x50 arch/x86/kvm/../../../virt/kvm/kvm_main.c:759
 __fput+0x333/0x7f0 fs/file_table.c:210
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x199/0x270 kernel/task_work.c:112
 exit_task_work include/linux/task_work.h:21 [inline]
 do_exit+0x9c8/0x1b00 kernel/exit.c:865
 do_group_exit+0x149/0x400 kernel/exit.c:968
 get_signal+0x73f/0x16d0 kernel/signal.c:2334
 do_signal+0x94/0x1ee0 arch/x86/kernel/signal.c:808
 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath+0x42f/0x510 arch/x86/entry/common.c:266
 entry_SYSCALL_64_fastpath+0xbc/0xbe
RIP: 0033:0x4520a9
RSP: 002b:00007f9024112c08 EFLAGS: 00000216 ORIG_RAX: 0000000000000010
RAX: fffffffffffffff4 RBX: 0000000000718000 RCX: 00000000004520a9
RDX: 000000002057afc0 RSI: 000000004040ae77 RDI: 0000000000000007
RBP: 0000000000002240 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000216 R12: 00000000004b8bfa
R13: 00000000ffffffff R14: 0000000000000007 R15: 000000004040ae77
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..