WARNING: CPU: 0 PID: 3003 at kernel/kthread.c:87 free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 3003 Comm: syzkaller912836 Not tainted 4.14.0-rc7-next-20171103+ #38
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 panic+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1c4/0x1e0 kernel/panic.c:546
 report_bug+0x211/0x2d0 lib/bug.c:184
 fixup_bug+0x40/0x90 arch/x86/kernel/traps.c:177
 do_trap_no_signal arch/x86/kernel/traps.c:211 [inline]
 do_trap+0x260/0x390 arch/x86/kernel/traps.c:260
 do_error_trap+0x120/0x390 arch/x86/kernel/traps.c:297
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:310
 invalid_op+0x18/0x20 arch/x86/entry/entry_64.S:906
RIP: 0010:free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
RSP: 0018:ffff8801db207768 EFLAGS: 00010206
RAX: ffff8801cf088300 RBX: ffff8801d5138cc0 RCX: ffffffff814937d2
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff8801d5138e48
RBP: ffff8801db207770 R08: 0000000000000000 R09: 1ffff1003b640ed4
R10: ffff8801cf088300 R11: 0000000000000001 R12: 1ffff1003b640ef0
R13: 1ffff1003b640ef4 R14: 0000000000000000 R15: ffff8801db2077e0
 free_task+0x134/0x1a0 kernel/fork.c:390
 __put_task_struct+0x229/0x3b0 kernel/fork.c:663
 put_task_struct include/linux/sched/task.h:96 [inline]
 delayed_put_task_struct+0xca/0x3d0 kernel/exit.c:180
 __rcu_reclaim kernel/rcu/rcu.h:172 [inline]
 rcu_do_batch kernel/rcu/tree.c:2676 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2935 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2902 [inline]
 rcu_process_callbacks+0xd74/0x17d0 kernel/rcu/tree.c:2919
 __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:1052
 apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:771
 </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:778 [inline]
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:160 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0x5e/0xba kernel/locking/spinlock.c:190
RSP: 0018:ffff8801ce9572c8 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff11
RAX: dffffc0000000000 RBX: 0000000000000286 RCX: 0000000000000000
RDX: 1ffffffff0bd9671 RSI: 0000000000000001 RDI: 0000000000000286
RBP: ffff8801ce9572d8 R08: ffff8801d4d5a400 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801d4d5aac0
R13: ffffffff8529acc0 R14: ffff8801d4d5a398 R15: ffff8801d4d5a300
 sched_fork+0x44b/0xc00 kernel/sched/core.c:2402
 copy_process.part.37+0x1730/0x4b30 kernel/fork.c:1767
 copy_process kernel/fork.c:1610 [inline]
 _do_fork+0x1ef/0xfe0 kernel/fork.c:2089
 SYSC_clone kernel/fork.c:2199 [inline]
 SyS_clone+0x37/0x50 kernel/fork.c:2193
 do_syscall_64+0x26c/0x8d0 arch/x86/entry/common.c:287
 entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x44951a
RSP: 002b:00007fff74b22810 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fff74b22810 RCX: 000000000044951a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007fff74b22850 R08: 0000000000000bbb R09: 00000000010f0880
R10: 00000000010f0b50 R11: 0000000000000246 R12: 0000000000000bbb
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..