------------[ cut here ]------------
WARNING: CPU: 2 PID: 8882 at kernel/rcu/tree_stall.h:1050 rcu_check_gp_start_stall.part.0+0x1c4/0x4b0 kernel/rcu/tree_stall.h:1050
Modules linked in:
CPU: 2 UID: 0 PID: 8882 Comm: udevd 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:rcu_check_gp_start_stall.part.0+0x1c4/0x4b0 kernel/rcu/tree_stall.h:1050
Code: 88 61 01 00 00 be 04 00 00 00 48 c7 c7 c0 c0 b0 9a e8 a0 4e 82 00 b8 01 00 00 00 87 05 f5 02 0f 19 85 c0 0f 85 3d 01 00 00 90 <0f> 0b 90 48 c7 c3 34 7d 82 90 48 81 fd 00 f4 3c 8e 74 5a 48 b8 00
RSP: 0018:ffffc90000538df0 EFLAGS: 00010046
RAX: 0000000000000000 RBX: 0000000000002904 RCX: ffffffff81a1bdc0
RDX: fffffbfff3561818 RSI: 0000000000000004 RDI: ffffffff9ab0c0c0
RBP: ffffffff8e3cf400 R08: 0000000000000001 R09: fffffbfff3561818
R10: 0000000000000003 R11: 0000000000000001 R12: 1ffffffff1c02240
R13: 0000000000000246 R14: ffffffff8e3cf400 R15: ffff88802b43b492
FS:  00007fd8db1ef880(0000) GS:ffff888097a0d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555828cfd628 CR3: 0000000075da9000 CR4: 0000000000352ef0
Call Trace:
 <IRQ>
 rcu_check_gp_start_stall kernel/rcu/tree_stall.h:1013 [inline]
 rcu_core+0x4cf/0x1530 kernel/rcu/tree.c:2856
 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:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_many_cond+0xdfd/0x1600 kernel/smp.c:877
Code: 57 48 8b 54 24 10 4c 89 74 24 10 49 89 d5 48 89 d5 48 89 54 24 18 49 c1 ed 03 83 e5 07 4d 01 e5 83 c5 03 e8 45 04 0c 00 f3 90 <41> 0f b6 45 00 40 38 c5 7c 08 84 c0 0f 85 e0 05 00 00 8b 43 08 31
RSP: 0018:ffffc9000785f240 EFLAGS: 00000293
RAX: 0000000000000000 RBX: ffff88802b342500 RCX: ffffffff81b05371
RDX: ffff888024274900 RSI: ffffffff81b0534b RDI: 0000000000000005
RBP: 0000000000000003 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffffed10056684a1 R14: 0000000000000001 R15: 0000000000000001
 on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1043
 kvm_flush_tlb_multi+0x266/0x3b0 arch/x86/kernel/kvm.c:678
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:91 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:1381 [inline]
 flush_tlb_mm_range+0x4a0/0x17a0 arch/x86/mm/tlb.c:1471
 flush_tlb_batched_pending+0x93/0xd0 mm/rmap.c:748
 zap_pte_range mm/memory.c:1845 [inline]
 zap_pmd_range mm/memory.c:1947 [inline]
 zap_pud_range mm/memory.c:1976 [inline]
 zap_p4d_range mm/memory.c:1997 [inline]
 unmap_page_range+0xae4/0x41b0 mm/memory.c:2018
 unmap_single_vma.constprop.0+0x153/0x240 mm/memory.c:2061
 unmap_vmas+0x218/0x470 mm/memory.c:2105
 vms_clear_ptes+0x41f/0x770 mm/vma.c:1228
 vms_complete_munmap_vmas+0x1ca/0x970 mm/vma.c:1277
 do_vmi_align_munmap+0x446/0x7e0 mm/vma.c:1536
 do_vmi_munmap+0x204/0x3e0 mm/vma.c:1584
 __vm_munmap+0x196/0x380 mm/vma.c:3156
 __do_sys_munmap mm/mmap.c:1080 [inline]
 __se_sys_munmap mm/mmap.c:1077 [inline]
 __x64_sys_munmap+0x59/0x80 mm/mmap.c:1077
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd8dab1e097
Code: 73 01 c3 48 8b 0d 61 2d 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 31 2d 0d 00 f7 d8 64 89 01 48
RSP: 002b:00007ffc8243b148 EFLAGS: 00000206 ORIG_RAX: 000000000000000b
RAX: ffffffffffffffda RBX: 0000555828c9bbf0 RCX: 00007fd8dab1e097
RDX: 0000000000000000 RSI: 00000000009480e8 RDI: 00007fd8da000000
RBP: 0000555828c9b910 R08: 0000555828cae140 R09: 0000000000000006
R10: 0000000000000000 R11: 0000000000000206 R12: 000055580275d588
R13: 00007ffc8243b1d0 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
----------------
Code disassembly (best guess):
   0:	57                   	push   %rdi
   1:	48 8b 54 24 10       	mov    0x10(%rsp),%rdx
   6:	4c 89 74 24 10       	mov    %r14,0x10(%rsp)
   b:	49 89 d5             	mov    %rdx,%r13
   e:	48 89 d5             	mov    %rdx,%rbp
  11:	48 89 54 24 18       	mov    %rdx,0x18(%rsp)
  16:	49 c1 ed 03          	shr    $0x3,%r13
  1a:	83 e5 07             	and    $0x7,%ebp
  1d:	4d 01 e5             	add    %r12,%r13
  20:	83 c5 03             	add    $0x3,%ebp
  23:	e8 45 04 0c 00       	call   0xc046d
  28:	f3 90                	pause
* 2a:	41 0f b6 45 00       	movzbl 0x0(%r13),%eax <-- trapping instruction
  2f:	40 38 c5             	cmp    %al,%bpl
  32:	7c 08                	jl     0x3c
  34:	84 c0                	test   %al,%al
  36:	0f 85 e0 05 00 00    	jne    0x61c
  3c:	8b 43 08             	mov    0x8(%rbx),%eax
  3f:	31                   	.byte 0x31