WARNING: CPU: 0 PID: 3049 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: 3049 Comm: syz-executor4 Not tainted 4.14.0-rc7-next-20171103+ #10
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 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:ffff88003ec07768 EFLAGS: 00010206
RAX: ffff88006b69a440 RBX: ffff88003d77ccc0 RCX: ffffffff814937d2
RDX: 0000000000000100 RSI: 0000000000000000 RDI: ffff88003d77ce48
RBP: ffff88003ec07770 R08: 0000000000000000 R09: 1ffff10007d80ed4
R10: ffff88006b69a440 R11: 0000000000000002 R12: 1ffff10007d80ef0
R13: 1ffff10007d80ef4 R14: 0000000000000000 R15: ffff88003ec077e0
 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:578
 </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:ffff880069967a18 EFLAGS: 00000286 ORIG_RAX: ffffffffffffff11
RAX: 0000000000000007 RBX: ffff88006d39f250 RCX: 0000000000000006
RDX: 0000000000000000 RSI: 1ffff1000d6d359d RDI: 0000000000000286
RBP: ffff880069967a38 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88006d831c40
R13: 0000000000000286 R14: ffffffff819b8582 R15: dffffc0000000000
 remove_vma+0x162/0x1b0 mm/mmap.c:176
 remove_vma_list mm/mmap.c:2475 [inline]
 do_munmap+0x82a/0xdf0 mm/mmap.c:2714
 mmap_region+0x59e/0x15a0 mm/mmap.c:1631
 do_mmap+0x6a1/0xd50 mm/mmap.c:1468
 do_mmap_pgoff include/linux/mm.h:2200 [inline]
 vm_mmap_pgoff+0x1de/0x280 mm/util.c:333
 SYSC_mmap_pgoff mm/mmap.c:1518 [inline]
 SyS_mmap_pgoff+0x23b/0x5f0 mm/mmap.c:1476
 SYSC_mmap arch/x86/kernel/sys_x86_64.c:100 [inline]
 SyS_mmap+0x16/0x20 arch/x86/kernel/sys_x86_64.c:91
 entry_SYSCALL_64_fastpath+0x1f/0xbe
RIP: 0033:0x447c89
RSP: 002b:00007f68cd277bd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f68cd2786cc RCX: 0000000000447c89
RDX: 0000000000000003 RSI: 0000000000fff000 RDI: 0000000020000000
RBP: 0000000000000086 R08: ffffffffffffffff R09: 0000000000000000
R10: 0000000000000032 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f68cd2789c0 R15: 00007f68cd278700
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..