WARNING: CPU: 1 PID: 3096 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: 3096 Comm: syzkaller730052 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:ffff8801db307768 EFLAGS: 00010206
RAX: ffff8801bc8f4400 RBX: ffff8801ccd260c0 RCX: ffffffff814937d2
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff8801ccd26248
RBP: ffff8801db307770 R08: 0000000000000000 R09: 1ffff1003b660ed4
R10: ffff8801bc8f4400 R11: 0000000000000001 R12: 1ffff1003b660ef0
R13: 1ffff1003b660ef4 R14: 0000000000000000 R15: ffff8801db3077e0
 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:kmem_cache_free+0x170/0x280 mm/slab.c:3752
RSP: 0018:ffff8801bc8ff068 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff11
RAX: 0000000000000007 RBX: ffff8801ce5967e0 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000286
RBP: ffff8801bc8ff088 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8801dac79680
R13: 0000000000000286 R14: ffffffff819e0faa R15: ffff8801ce5967f8
 anon_vma_chain_free mm/rmap.c:133 [inline]
 unlink_anon_vmas+0x5aa/0x9f0 mm/rmap.c:418
 free_pgtables+0xe7/0x330 mm/memory.c:621
 exit_mmap+0x2bf/0x530 mm/mmap.c:3022
 __mmput kernel/fork.c:966 [inline]
 mmput+0x223/0x6c0 kernel/fork.c:987
 exit_mm kernel/exit.c:544 [inline]
 do_exit+0x904/0x1ad0 kernel/exit.c:856
 do_group_exit+0x149/0x400 kernel/exit.c:972
 get_signal+0x73f/0x16d0 kernel/signal.c:2333
 do_signal+0x94/0x1ee0 arch/x86/kernel/signal.c:809
 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath+0x42f/0x510 arch/x86/entry/common.c:266
 ret_from_fork+0x15/0x40 arch/x86/entry/entry_64.S:424
RIP: 0033:0x448cd9
RSP: 002b:00007f191f922e70 EFLAGS: 00000202 ORIG_RAX: 0000000000000038
RAX: 0000000000000000 RBX: 00007f191f923700 RCX: 0000000000448cd9
RDX: 00007f191f9239d0 RSI: 00007f191f922e70 RDI: 00000000003d0f00
RBP: 00007ffc53717a80 R08: 00007f191f923700 R09: 00007f191f923700
R10: 00007f191f9239d0 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffc53717a7f R14: 00007f191f9239c0 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..