======================================
| [  140.682605][    C2] page dumped because: VM_BUG_ON_PAGE(page_ref_count(page) == 0)
| [  140.682904][    C2] ------------[ cut here ]------------
| [  140.683131][    C2] kernel BUG at include/linux/mm.h:1140!
| [  140.683353][    C2] Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
[  140.683845][    C2] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014
[ 140.684240][ C2] RIP: 0010:__free_pages (./include/linux/mm.h:1140 ./include/linux/mm.h:1138 mm/page_alloc.c:4819) 
[ 140.684424][ C2] Code: 0f 94 c3 e9 ba fe ff ff 48 c7 c6 a0 18 98 ba 4c 89 e7 e8 df bf f4 ff 90 0f 0b 48 c7 c6 40 29 98 ba 4c 89 e7 e8 cd bf f4 ff 90 <0f> 0b 48 89 ef e8 72 03 09 00 e9 c5 fe ff ff e8 98 03 09 00 e9 35
All code
========
   0:	0f 94 c3             	sete   %bl
   3:	e9 ba fe ff ff       	jmp    0xfffffffffffffec2
   8:	48 c7 c6 a0 18 98 ba 	mov    $0xffffffffba9818a0,%rsi
   f:	4c 89 e7             	mov    %r12,%rdi
  12:	e8 df bf f4 ff       	call   0xfffffffffff4bff6
  17:	90                   	nop
  18:	0f 0b                	ud2
  1a:	48 c7 c6 40 29 98 ba 	mov    $0xffffffffba982940,%rsi
  21:	4c 89 e7             	mov    %r12,%rdi
  24:	e8 cd bf f4 ff       	call   0xfffffffffff4bff6
  29:	90                   	nop
  2a:*	0f 0b                	ud2		<-- trapping instruction
  2c:	48 89 ef             	mov    %rbp,%rdi
  2f:	e8 72 03 09 00       	call   0x903a6
  34:	e9 c5 fe ff ff       	jmp    0xfffffffffffffefe
  39:	e8 98 03 09 00       	call   0x903d6
  3e:	e9                   	.byte 0xe9
  3f:	35                   	.byte 0x35

Code starting with the faulting instruction
===========================================
   0:	0f 0b                	ud2
   2:	48 89 ef             	mov    %rbp,%rdi
   5:	e8 72 03 09 00       	call   0x9037c
   a:	e9 c5 fe ff ff       	jmp    0xfffffffffffffed4
   f:	e8 98 03 09 00       	call   0x903ac
  14:	e9                   	.byte 0xe9
  15:	35                   	.byte 0x35
[  140.685039][    C2] RSP: 0018:ffffc90000240df8 EFLAGS: 00010246
[  140.685262][    C2] RAX: 000000000000003e RBX: 0000000000000000 RCX: 1ffffffff76bb43c
[  140.685520][    C2] RDX: 0000000000000000 RSI: 0000000000000004 RDI: 0000000000000001
[  140.685781][    C2] RBP: ffffea0000275f34 R08: 0000000000000000 R09: fffffbfff76bb43c
[  140.686076][    C2] R10: 0000000000000003 R11: 205d324320202020 R12: ffffea0000275f00
[  140.686331][    C2] R13: ffffc90000240ec0 R14: 0000000000000000 R15: 000000000000015b
[  140.686583][    C2] FS:  0000000000000000(0000) GS:ffff88802f500000(0000) knlGS:0000000000000000
[  140.686972][    C2] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  140.687185][    C2] CR2: 000055f8e648fdec CR3: 0000000007cc0004 CR4: 0000000000772ef0
[  140.687449][    C2] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  140.687791][    C2] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  140.688053][    C2] PKRU: 55555554
[  140.688190][    C2] Call Trace:
[  140.688317][    C2]  <IRQ>
[ 140.688405][ C2] ? die (arch/x86/kernel/dumpstack.c:421 arch/x86/kernel/dumpstack.c:434 arch/x86/kernel/dumpstack.c:447) 
[ 140.688547][ C2] ? do_trap (arch/x86/kernel/traps.c:156 arch/x86/kernel/traps.c:197) 
[ 140.688763][ C2] ? __free_pages (./include/linux/mm.h:1140 ./include/linux/mm.h:1138 mm/page_alloc.c:4819) 
[ 140.688942][ C2] ? do_error_trap (./arch/x86/include/asm/traps.h:58 arch/x86/kernel/traps.c:218) 
[ 140.689112][ C2] ? __free_pages (./include/linux/mm.h:1140 ./include/linux/mm.h:1138 mm/page_alloc.c:4819) 
[ 140.689308][ C2] ? __free_pages (./include/linux/mm.h:1140 ./include/linux/mm.h:1138 mm/page_alloc.c:4819) 
[ 140.689478][ C2] ? handle_invalid_op (arch/x86/kernel/traps.c:256) 
[ 140.689648][ C2] ? __free_pages (./include/linux/mm.h:1140 ./include/linux/mm.h:1138 mm/page_alloc.c:4819) 
[ 140.689931][ C2] ? exc_invalid_op (arch/x86/kernel/traps.c:315) 
[ 140.690107][ C2] ? asm_exc_invalid_op (./arch/x86/include/asm/idtentry.h:621) 
[ 140.690385][ C2] ? __free_pages (./include/linux/mm.h:1140 ./include/linux/mm.h:1138 mm/page_alloc.c:4819) 
[ 140.690620][ C2] ? __free_pages (./include/linux/mm.h:1140 ./include/linux/mm.h:1138 mm/page_alloc.c:4819) 
[ 140.690788][ C2] ? rcu_do_batch (kernel/rcu/tree.c:2567) 
[ 140.690970][ C2] neigh_hash_free_rcu (net/core/neighbour.c:555) 
[ 140.691234][ C2] rcu_do_batch (kernel/rcu/tree.c:2567) 
[ 140.691447][ C2] ? __pfx_rcu_do_batch (kernel/rcu/tree.c:2491) 
[ 140.691617][ C2] ? lockdep_hardirqs_on_prepare (kernel/locking/lockdep.c:4339 kernel/locking/lockdep.c:4406) 
[ 140.691846][ C2] rcu_core (kernel/rcu/tree.c:2825) 
[ 140.691981][ C2] handle_softirqs (kernel/softirq.c:554) 
[ 140.692278][ C2] irq_exit_rcu (kernel/softirq.c:589 kernel/softirq.c:428 kernel/softirq.c:637 kernel/softirq.c:649) 
[ 140.692433][ C2] sysvec_apic_timer_interrupt (arch/x86/kernel/apic/apic.c:1037 arch/x86/kernel/apic/apic.c:1037) 
[  140.692619][    C2]  </IRQ>
[  140.692705][    C2]  <TASK>
[ 140.692792][ C2] asm_sysvec_apic_timer_interrupt (./arch/x86/include/asm/idtentry.h:702) 
[ 140.693012][ C2] RIP: 0010:default_idle (./arch/x86/include/asm/irqflags.h:37 ./arch/x86/include/asm/irqflags.h:92 arch/x86/kernel/process.c:743) 
[ 140.693194][ C2] Code: 4c 01 c7 4c 29 c2 e9 72 ff ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d e3 4e 3f 00 fb f4 <fa> c3 cc cc cc cc 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90
All code
========
   0:	4c 01 c7             	add    %r8,%rdi
   3:	4c 29 c2             	sub    %r8,%rdx
   6:	e9 72 ff ff ff       	jmp    0xffffffffffffff7d
   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:	66 90                	xchg   %ax,%ax
  21:	0f 00 2d e3 4e 3f 00 	verw   0x3f4ee3(%rip)        # 0x3f4f0b
  28:	fb                   	sti
  29:	f4                   	hlt
  2a:*	fa                   	cli		<-- trapping instruction
  2b:	c3                   	ret
  2c:	cc                   	int3
  2d:	cc                   	int3
  2e:	cc                   	int3
  2f:	cc                   	int3
  30:	66 66 2e 0f 1f 84 00 	data16 cs nopw 0x0(%rax,%rax,1)
  37:	00 00 00 00 
  3b:	90                   	nop
  3c:	90                   	nop
  3d:	90                   	nop
  3e:	90                   	nop
  3f:	90                   	nop

Code starting with the faulting instruction
===========================================
   0:	fa                   	cli
   1:	c3                   	ret
   2:	cc                   	int3
   3:	cc                   	int3
   4:	cc                   	int3
   5:	cc                   	int3
   6:	66 66 2e 0f 1f 84 00 	data16 cs nopw 0x0(%rax,%rax,1)
   d:	00 00 00 00 
  11:	90                   	nop
  12:	90                   	nop
  13:	90                   	nop
  14:	90                   	nop
  15:	90                   	nop
[  140.693963][    C2] RSP: 0018:ffffc9000016fdf8 EFLAGS: 00000246
[  140.694172][    C2] RAX: 000000000035f0c9 RBX: 1ffff9200002dfc1 RCX: ffffffffba46c435
[  140.694445][    C2] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffffb7cb1f94
[  140.694722][    C2] RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed1005ea70e2
[  140.695085][    C2] R10: ffff88802f538713 R11: ffff88802f53dd40 R12: 0000000000000000
[  140.695357][    C2] R13: ffff888001bb0040 R14: dffffc0000000000 R15: 0000000000000000
[ 140.695616][ C2] ? ct_kernel_exit.constprop.0 (kernel/context_tracking.c:147) 
[ 140.695784][ C2] ? cpuidle_idle_call (kernel/sched/idle.c:186) 
[ 140.695971][ C2] default_idle_call (./include/linux/cpuidle.h:143 kernel/sched/idle.c:118) 
[ 140.696328][ C2] cpuidle_idle_call (kernel/sched/idle.c:186) 
[ 140.696499][ C2] ? __pfx_cpuidle_idle_call (kernel/sched/idle.c:168) 
[ 140.696699][ C2] ? tsc_verify_tsc_adjust (arch/x86/kernel/tsc_sync.c:59) 
[ 140.696872][ C2] do_idle (kernel/sched/idle.c:326) 
[ 140.697013][ C2] cpu_startup_entry (kernel/sched/idle.c:423 (discriminator 1)) 
[ 140.697182][ C2] start_secondary (arch/x86/kernel/smpboot.c:202 arch/x86/kernel/smpboot.c:282) 
[ 140.697457][ C2] ? __pfx_start_secondary (arch/x86/kernel/smpboot.c:232) 


Finger prints:
__free_pages:neigh_hash_free_rcu:rcu_do_batch:rcu_core:handle_softirqs