WARNING: CPU: 0 PID: 14915 at kernel/fork.c:449 free_task+0x1b3/0x1f0 kernel/fork.c:449
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 14915 Comm: syz-executor0 Not tainted 4.19.0-rc7-next-20181012+ #93
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x244/0x3ab lib/dump_stack.c:113
 panic+0x238/0x4e7 kernel/panic.c:184
 __warn.cold.8+0x163/0x1ba kernel/panic.c:536
 report_bug+0x254/0x2d0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
 do_invalid_op+0x36/0x40 arch/x86/kernel/traps.c:290
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:969
RIP: 0010:free_task+0x1b3/0x1f0 kernel/fork.c:449
kobject: 'loop2' (00000000a066beb8): kobject_uevent_env
Code: 25 28 00 00 00 75 4e 48 83 c4 60 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 8c 59 37 00 48 89 df e8 64 a2 0b 00 eb ac e8 7d 59 37 00 <0f> 0b e9 3f ff ff ff e8 81 e0 7b 00 e9 7c ff ff ff 4c 89 e7 e8 14
RSP: 0018:ffff8801dae07498 EFLAGS: 00010206
RAX: ffff88017dc54240 RBX: ffff8801cd32e200 RCX: ffffffff81471010
RDX: 0000000000000100 RSI: ffffffff814710d3 RDI: 0000000000000005
RBP: ffff8801dae07520 R08: ffff88017dc54240 R09: ffffed0039a65ea7
R10: ffffed0039a65ea7 R11: ffff8801cd32f53b R12: 1ffff1003b5c0e97
R13: 1ffff1003b5c0e93 R14: 0000000000000001 R15: ffff8801dae074f8
kobject: 'loop2' (00000000a066beb8): fill_kobj_path: path = '/devices/virtual/block/loop2'
 __put_task_struct+0x2e6/0x620 kernel/fork.c:730
 put_task_struct include/linux/sched/task.h:96 [inline]
 delayed_put_task_struct+0x2fa/0x4b0 kernel/exit.c:181
 __rcu_reclaim kernel/rcu/rcu.h:240 [inline]
 rcu_do_batch kernel/rcu/tree.c:2437 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2716 [inline]
 rcu_process_callbacks+0x1006/0x1ac0 kernel/rcu/tree.c:2697
 __do_softirq+0x30d/0xb26 kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0x17f/0x1c0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0x1cb/0x750 arch/x86/kernel/apic/apic.c:1061
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:804
 </IRQ>
RIP: 0010:compound_head include/linux/page-flags.h:143 [inline]
RIP: 0010:PageSwapBacked include/linux/page-flags.h:307 [inline]
RIP: 0010:PageSwapCache include/linux/page-flags.h:352 [inline]
RIP: 0010:free_swap_cache mm/swap_state.c:266 [inline]
RIP: 0010:free_pages_and_swap_cache+0x115/0x6f0 mm/swap_state.c:294
Code: 89 85 60 fe ff ff 48 8d 85 d8 fe ff ff 48 c1 e8 03 48 01 d8 48 89 85 70 fe ff ff 48 8d 45 98 48 c1 e8 03 48 89 85 68 fe ff ff <e8> 76 a3 c3 ff 48 8b 85 60 fe ff ff 48 c1 e8 03 80 3c 18 00 0f 85
RSP: 0018:ffff88017c516a78 EFLAGS: 00000202 ORIG_RAX: ffffffffffffff13
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: ffffffff81baca0d
RDX: 0000000000000022 RSI: 00000000000001fe RDI: 0000000000000004
RBP: ffff88017c516c48 R08: ffff88017dc54240 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffea0007014c00
R13: 00000000000001fe R14: 0000000000000022 R15: ffff88017c516c20
 tlb_flush_mmu_free+0xff/0x1b0 mm/mmu_gather.c:74
 zap_pte_range mm/memory.c:1158 [inline]
 zap_pmd_range mm/memory.c:1193 [inline]
 zap_pud_range mm/memory.c:1222 [inline]
 zap_p4d_range mm/memory.c:1243 [inline]
 unmap_page_range+0x1fa6/0x2870 mm/memory.c:1264
 unmap_single_vma+0x19b/0x310 mm/memory.c:1309
 unmap_vmas+0x125/0x200 mm/memory.c:1339
 exit_mmap+0x2be/0x590 mm/mmap.c:3142
 __mmput kernel/fork.c:1045 [inline]
 mmput+0x247/0x610 kernel/fork.c:1066
 exit_mm kernel/exit.c:545 [inline]
 do_exit+0xe6f/0x2610 kernel/exit.c:854
 do_group_exit+0x177/0x440 kernel/exit.c:970
 get_signal+0x8a8/0x1970 kernel/signal.c:2517
 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457569
Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fbd16db8cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000072bfa8 RCX: 0000000000457569
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 000000000072bfa8
RBP: 000000000072bfa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000072bfac
R13: 00007fff2a985d6f R14: 00007fbd16db99c0 R15: 0000000000000001
Kernel Offset: disabled
Rebooting in 86400 seconds..