WARNING: CPU: 1 PID: 3143 at kernel/kthread.c:87 free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3143 Comm: syz-executor2 Not tainted 4.14.0-rc2-next-20170927+ #30
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: 0000:ffff8801db307710 EFLAGS: 00010206
RAX: ffff8801caab0440 RBX: ffff8801ca9ab340 RCX: 1ffff1003b660ed6
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff8801ca9ab4c8
RBP: ffff8801db307718 R08: 0000000000000000 R09: 1ffff1003b660ec9
R10: ffff8801caab0440 R11: 0000000000000004 R12: 1ffff1003b660ee5
R13: 1ffff1003b660ee9 R14: 0000000000000000 R15: ffff8801db307788
 free_task+0x134/0x1a0 kernel/fork.c:384
 __put_task_struct+0x240/0x5b0 kernel/fork.c:422
 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:lock_is_held_type+0x18b/0x210 kernel/locking/lockdep.c:4042
RSP: 0000:ffff8801caa27668 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff11
RAX: dffffc0000000000 RBX: 0000000000000286 RCX: 0000000000000000
RDX: 1ffffffff0b59705 RSI: ffffffff85b3c240 RDI: 0000000000000286
RBP: ffff8801caa27688 R08: ffff8801caa270e8 R09: ffff8801caa270e0
R10: ffff8801caa27058 R11: 1ffff1003955631b R12: ffff8801caab0440
R13: 0000000000000000 R14: 00000000000001dc R15: dffffc0000000000
 lock_is_held include/linux/lockdep.h:436 [inline]
 rcu_preempt_sleep_check include/linux/rcupdate.h:301 [inline]
 ___might_sleep+0x35e/0x470 kernel/sched/core.c:5990
 __might_sleep+0x95/0x190 kernel/sched/core.c:5978
 lock_page include/linux/pagemap.h:476 [inline]
 block_page_mkwrite+0xe8/0x3a0 fs/buffer.c:2524
 ext4_page_mkwrite+0xd60/0x1240 fs/ext4/inode.c:6029
 do_page_mkwrite+0x141/0x490 mm/memory.c:2353
 do_shared_fault mm/memory.c:3645 [inline]
 do_fault mm/memory.c:3684 [inline]
 handle_pte_fault mm/memory.c:3910 [inline]
 __handle_mm_fault+0x1aab/0x39c0 mm/memory.c:4034
 handle_mm_fault+0x334/0x8d0 mm/memory.c:4071
 __do_page_fault+0x5bd/0xd60 arch/x86/mm/fault.c:1444
 do_page_fault+0xee/0x720 arch/x86/mm/fault.c:1520
 page_fault+0x22/0x30 arch/x86/entry/entry_64.S:1066
RIP: 0033:0x40125d
RSP: 002b:00007ffc87ef2e80 EFLAGS: 00010287
RAX: 0000001ddcc20000 RBX: 00000000021f8914 RCX: 000000000040c3e0
RDX: 0000001ddbc20000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 00000000021f8940
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000c23
R13: 0000000000000007 R14: 00000000000087c5 R15: 0000000000000016
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..