WARNING: CPU: 1 PID: 5124 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: 5124 Comm: syzkaller953061 Not tainted 4.14.0-rc5-mm1+ #20
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+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1c4/0x1e0 kernel/panic.c:546
 report_bug+0x211/0x2d0 lib/bug.c:183
 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:905
RIP: 0010:free_kthread_struct+0xa2/0xe0 kernel/kthread.c:87
RSP: 0018:ffff8801db307768 EFLAGS: 00010206
RAX: ffff8801c1b38280 RBX: ffff8801d52b8b00 RCX: ffffffff8148d7e2
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff8801d52b8bb8
RBP: ffff8801db307770 R08: 0000000000000001 R09: 1ffff1003b660edc
R10: ffff8801db3076a8 R11: 0000000000000002 R12: 1ffff1003b660ef0
R13: 1ffff1003b660ef4 R14: 0000000000000000 R15: ffff8801db3077e0
 free_task+0x134/0x1a0 kernel/fork.c:390
 __put_task_struct+0x229/0x3b0 kernel/fork.c:668
 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:172 [inline]
 rcu_do_batch kernel/rcu/tree.c:2676 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2930 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2897 [inline]
 rcu_process_callbacks+0xd74/0x17d0 kernel/rcu/tree.c:2914
 __do_softirq+0x2d7/0xb85 kernel/softirq.c:284
 invoke_softirq kernel/softirq.c:364 [inline]
 irq_exit+0x1cc/0x200 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:770
 </IRQ>
RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:777 [inline]
RIP: 0010:lock_release+0x505/0xa40 kernel/locking/lockdep.c:4013
RSP: 0018:ffff8801bf0e6e90 EFLAGS: 00000282 ORIG_RAX: ffffffffffffff11
RAX: dffffc0000000000 RBX: ffff8801c1b38280 RCX: 1ffff1003836715c
RDX: 1ffffffff0b58f39 RSI: 0000000000000002 RDI: 0000000000000282
RBP: ffff8801bf0e6fc0 R08: 0000000000000001 R09: 1ffff10037e1cddb
R10: ffff8801bf0e6e10 R11: 0000000000000001 R12: 4029b9c22318321e
R13: ffff8801c1b38280 R14: ffff8801bf0e6ed8 R15: 1ffff10037e1cdd7
 rcu_lock_release include/linux/rcupdate.h:249 [inline]
 rcu_read_unlock include/linux/rcupdate.h:687 [inline]
 __unlock_page_memcg+0x72/0x100 mm/memcontrol.c:1697
 unlock_page_memcg+0x2c/0x40 mm/memcontrol.c:1706
 page_remove_file_rmap mm/rmap.c:1247 [inline]
 page_remove_rmap+0x3b7/0xcb0 mm/rmap.c:1298
 zap_pte_range mm/memory.c:1334 [inline]
 zap_pmd_range mm/memory.c:1438 [inline]
 zap_pud_range mm/memory.c:1467 [inline]
 zap_p4d_range mm/memory.c:1488 [inline]
 unmap_page_range+0xfc3/0x22e0 mm/memory.c:1509
 unmap_single_vma+0x15f/0x2d0 mm/memory.c:1554
 unmap_vmas+0xf1/0x1b0 mm/memory.c:1584
 exit_mmap+0x232/0x530 mm/mmap.c:3003
 __mmput kernel/fork.c:971 [inline]
 mmput+0x223/0x6c0 kernel/fork.c:992
 exit_mm kernel/exit.c:544 [inline]
 do_exit+0x904/0x1ad0 kernel/exit.c:856
 do_group_exit+0x149/0x400 kernel/exit.c:972
 SYSC_exit_group kernel/exit.c:983 [inline]
 SyS_exit_group+0x1d/0x20 kernel/exit.c:981
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x44c739
RSP: 002b:00007fff2443dde8 EFLAGS: 00000206 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000007 RCX: 000000000044c739
RDX: 000000000044adc1 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000082 R08: 00000000006dd1c0 R09: 0000000000000000
R10: 00000000006dd144 R11: 0000000000000206 R12: 0000000000000000
R13: 00007fff2443dd8f R14: 00007f9780f1f9c0 R15: 0000000000000000
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..