Comment # 1 on bug 1099012 from Jiri Slaby

And it seems to be reproducible, so full output:
> BUG: unable to handle kernel paging request at 000000100000004c
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP PTI
> Modules linked in: af_packet iscsi_ibft iscsi_boot_sysfs nls_iso8859_1 nls_cp437 vfat fat snd_hda_codec_generic virtio_gpu snd_hda_intel ttm snd_hda_codec snd_hda_core drm_kms_helper snd_hwdep drm snd_pcm snd_timer fb_sys_fops ppdev syscopyarea sysfillrect snd joydev sysimgblt virtio_input pcspkr virtio_balloon virtio_net soundcore parport_pc i2c_piix4 parport qemu_fw_cfg button ata_generic uhci_hcd ehci_pci ehci_hcd usbcore ata_piix virtio_scsi serio_raw floppy sg dm_multipath dm_mod scsi_dh_rdac scsi_dh_emc scsi_dh_alua virtio_rng
> CPU: 3 PID: 30 Comm: ksoftirqd/3 Not tainted 4.17.2-5.g33a2d86-default #1 openSUSE Tumbleweed (unreleased)
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.0.0-prebuilt.qemu-project.org 04/01/2014
> RIP: 0010:put_css_set_locked+0x7f/0x270
> RSP: 0000:ffffbda08073fda8 EFLAGS: 00010006
> RAX: 0000000fffffffe0 RBX: ffff9c6d36636cc8 RCX: 0000000000000040
> RDX: ffff9c6d0f20b0c8 RSI: 0000000000000000 RDI: ffff9c6d36636c00
> RBP: ffff9c6d36636c08 R08: ffff9c6dbf1e5900 R09: 0000000000000100
> R10: ffff9c6dbf1e5300 R11: ffff9c6dbf1e5e40 R12: ffff9c6d36636c00
> R13: ffff9c6d36636d88 R14: dead000000000200 R15: dead000000000100
> FS:  0000000000000000(0000) GS:ffff9c6dc6980000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 000000100000004c CR3: 00000000776ba000 CR4: 00000000000006e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  cgroup_free+0x90/0xb0
>  __put_task_struct+0x3d/0x140
>  rcu_process_callbacks+0x245/0x560
>  __do_softirq+0x110/0x36b
>  ? sort_range+0x20/0x20
>  run_ksoftirqd+0x2e/0x40
>  smpboot_thread_fn+0xf1/0x1e0
>  kthread+0x112/0x130
>  ? kthread_create_worker_on_cpu+0x40/0x40
>  ret_from_fork+0x3a/0x50
> Code: 00 ad de eb 0d 48 83 c3 10 48 83 c5 08 49 39 dd 74 52 48 8b 43 08 48 8b 13 48 89 42 08 48 89 10 4c 89 3b 4c 89 73 08 48 8b 45 00 <f6> 40 6c 01 75 d4 65 ff 05 04 88 ee 76 48 8b 50 18 f6 c2 03 0f
> RIP: put_css_set_locked+0x7f/0x270 RSP: ffffbda08073fda8
> CR2: 000000100000004c