Comment 8 for bug 1736390

Stacktrace from artful:

Dec 13 12:06:09 artful-i386-testing kernel: [ 160.913030] BUG: unable to handle kernel NULL pointer dereference at (null)
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.915102] IP: igmp_group_dropped+0x21/0x220
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.916317] *pdpt = 0000000000000000 *pde = f000ff53f000ff53
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.916329]
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.917728] Oops: 0000 [#1] SMP
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.918345] Modules linked in: veth openvswitch nf_conntrack_ipv6 nf_nat_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_defrag_ipv6 nf_nat nf_conntrack ppdev kvm_intel kvm irqbypass crc32_pclmul input_leds serio_raw joydev parport_pc parport ib_iser rdma_cm iw_cm ib_cm ib_core iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables x_tables autofs4 btrfs raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_generic usbhid aesni_intel hid aes_i586 crypto_simd cryptd virtio_blk psmouse virtio_net floppy
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.931511] CPU: 0 PID: 29 Comm: kworker/u2:1 Tainted: G W 4.13.0-16-generic #19-Ubuntu
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.933321] Hardware name: OpenStack Foundation OpenStack Nova, BIOS 1.10.1-1ubuntu1~cloud0 04/01/2014
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.934970] Workqueue: netns cleanup_net
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.937847] task: f577c200 task.stack: f4c5a000
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.938694] EIP: igmp_group_dropped+0x21/0x220
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.940625] EFLAGS: 00010202 CPU: 0
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.941432] EAX: 00000000 EBX: f2b32c60 ECX: f4c5be68 EDX: 00000002
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.942712] ESI: 00000000 EDI: f29c1700 EBP: f4c5bdc8 ESP: f4c5bd90
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.944471] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.945612] CR0: 80050033 CR2: 00000000 CR3: 1ad8a000 CR4: 000406f0
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.946879] Call Trace:
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.949247] ? __wake_up+0x36/0x40
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.950074] ip_mc_down+0x27/0x90
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.951557] inetdev_event+0x398/0x4e0
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.953391] ? skb_dequeue+0x5b/0x70
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.954246] ? wireless_nlevent_flush+0x4c/0x90
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.955656] notifier_call_chain+0x4e/0x70
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.956814] raw_notifier_call_chain+0x11/0x20
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.957803] call_netdevice_notifiers_info+0x2a/0x60
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.958886] dev_close_many+0x9d/0xe0
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.962228] rollback_registered_many+0xd7/0x380
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.963690] unregister_netdevice_many.part.102+0x10/0x80
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.964981] default_device_exit_batch+0x134/0x160
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.966026] ? do_wait_intr_irq+0x80/0x80
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.966937] ops_exit_list.isra.8+0x4d/0x60
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.969310] cleanup_net+0x18e/0x260
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.973290] process_one_work+0x1a0/0x390
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.975236] worker_thread+0x37/0x440
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.976998] kthread+0xf3/0x110
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.977853] ? process_one_work+0x390/0x390
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.978803] ? kthread_create_on_node+0x20/0x20
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.980521] ret_from_fork+0x19/0x24
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.981350] Code: 90 90 90 90 90 90 90 90 90 90 66 66 66 66 90 55 89 e5 57 56 53 89 c3 83 ec 2c 8b 33 65 a1 14 00 00 00 89 45 f0 31 c0 80 7b 4b 00 <8b> 06 8b b8 20 03 00 00 8b 43 04 0f 85 5e 01 00 00 3d e0 00 00
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.987207] EIP: igmp_group_dropped+0x21/0x220 SS:ESP: 0068:f4c5bd90
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.988793] CR2: 0000000000000000
Dec 13 12:06:09 artful-i386-testing kernel: [ 160.989603] ---[ end trace 9fe78986aa6abc43 ]---
Dec 13 12:12:22 artful-i386-testing kernel: [ 0.000000] random: get_random_bytes called from start_kernel+0x35/0x41e with crng_init=0
Dec 13 12:12:22 artful-i386-testing kernel: [ 0.000000] Linux version 4.13.0-16-generic (buildd@lgw01-amd64-011) (gcc version 7.2.0 (Ubuntu 7.2.0-8ubuntu2)) #19-Ubuntu SMP Wed Oct 11 18:33:49 UTC 2017 (Ubuntu 4.13.0-16.19-generic 4.13.4)