kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
vkms_vblank_simulate: vblank timer overrun
------------[ cut here ]------------
WARNING: CPU: 1 PID: 0 at lib/ref_tracker.c:323 ref_tracker_free+0x61a/0x830 lib/ref_tracker.c:323
Modules linked in:
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:ref_tracker_free+0x61a/0x830 lib/ref_tracker.c:323
Code: 00 44 8b 73 18 31 ff 44 89 f6 e8 01 8e e6 fc 45 85 f6 0f 85 a6 00 00 00 e8 b3 92 e6 fc 48 8b 34 24 48 89 ef e8 c7 0f 8a 06 90 <0f> 0b 90 bb ea ff ff ff e9 50 fd ff ff e8 94 92 e6 fc 4c 8d 6d 44
RSP: 0000:ffffc90000590a80 EFLAGS: 00010202
RAX: 0000000000000101 RBX: ffff888049ab22c0 RCX: 0000000000000000
RDX: 0000000000000102 RSI: ffffffff8da27d97 RDI: 0000000000000001
RBP: ffff888043860618 R08: 0000000000000001 R09: 0000000000000001
R10: ffffffff90823ad7 R11: 0000000000000001 R12: 1ffff920000b2152
R13: ffffc90000590ab0 R14: 0000000003d00300 R15: ffff888049ab22d8
FS:  0000000000000000(0000) GS:ffff888097910000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000c82fe41 CR3: 000000004b85c000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 netdev_tracker_free include/linux/netdevice.h:4395 [inline]
 netdev_put include/linux/netdevice.h:4412 [inline]
 netdev_put include/linux/netdevice.h:4408 [inline]
 dev_watchdog+0x1dd/0xa10 net/sched/sch_generic.c:552
 call_timer_fn+0x19a/0x620 kernel/time/timer.c:1747
 expire_timers kernel/time/timer.c:1798 [inline]
 __run_timers+0x6ef/0x960 kernel/time/timer.c:2372
 __run_timer_base kernel/time/timer.c:2384 [inline]
 __run_timer_base kernel/time/timer.c:2376 [inline]
 run_timer_base+0x114/0x190 kernel/time/timer.c:2393
 run_timer_softirq+0x1a/0x40 kernel/time/timer.c:2403
 handle_softirqs+0x219/0x8e0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x109/0x170 kernel/softirq.c:723
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1052
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:82
Code: b7 6f 02 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa eb 07 0f 00 2d a3 e4 2c 00 fb f4 <e9> 3c 0a 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0000:ffffc9000046fde8 EFLAGS: 00000286
RAX: 0000000000365e09 RBX: 0000000000000001 RCX: ffffffff8b5d42a9
RDX: 0000000000000000 RSI: ffffffff8da27d97 RDI: ffffffff8bf075c0
RBP: ffffed1003b57490 R08: 0000000000000001 R09: ffffed1005666655
R10: ffff88802b3332ab R11: 0000000000000001 R12: 0000000000000001
R13: ffff88801daba480 R14: ffffffff90823ad0 R15: 0000000000000000
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:190 [inline]
 do_idle+0x38d/0x500 kernel/sched/idle.c:330
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:428
 start_secondary+0x21d/0x2b0 arch/x86/kernel/smpboot.c:315
 common_startup_64+0x13e/0x148
 </TASK>
----------------
Code disassembly (best guess):
   0:	b7 6f                	mov    $0x6f,%bh
   2:	02 c3                	add    %bl,%al
   4:	cc                   	int3
   5:	cc                   	int3
   6:	cc                   	int3
   7:	cc                   	int3
   8:	0f 1f 00             	nopl   (%rax)
   b:	90                   	nop
   c:	90                   	nop
   d:	90                   	nop
   e:	90                   	nop
   f:	90                   	nop
  10:	90                   	nop
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
  16:	90                   	nop
  17:	90                   	nop
  18:	90                   	nop
  19:	90                   	nop
  1a:	90                   	nop
  1b:	f3 0f 1e fa          	endbr64
  1f:	eb 07                	jmp    0x28
  21:	0f 00 2d a3 e4 2c 00 	verw   0x2ce4a3(%rip)        # 0x2ce4cb
  28:	fb                   	sti
  29:	f4                   	hlt
* 2a:	e9 3c 0a 03 00       	jmp    0x30a6b <-- trapping instruction
  2f:	66 2e 0f 1f 84 00 00 	cs nopw 0x0(%rax,%rax,1)
  36:	00 00 00
  39:	66 90                	xchg   %ax,%ax
  3b:	90                   	nop
  3c:	90                   	nop
  3d:	90                   	nop
  3e:	90                   	nop
  3f:	90                   	nop