IPv6: ADDRCONF(NETDEV_UP): veth1_to_batadv: link is not ready
vhci_hcd vhci_hcd.0: pdev(3) rhport(1) sockfd(3)
vhci_hcd vhci_hcd.0: devid(0) speed(1) speed_str(low-speed)
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
vhci_hcd: connection closed
BUG: unable to handle kernel NULL pointer dereference at 000000000000001c
IP: atomic_inc arch/x86/include/asm/atomic.h:92 [inline]
IP: kthread_stop+0x47/0x640 kernel/kthread.c:525
PGD 6d3ed067 P4D 6d3ed067 PUD 6d3ee067 PMD 0 
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
Oops: 0002 [#1] PREEMPT SMP KASAN
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
Modules linked in:
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
CPU: 1 PID: 5434 Comm: kworker/u4:5 Not tainted 4.14.215-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: usbip_event event_handler
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
task: ffff8880a9fd4480 task.stack: ffff8880932e8000
RIP: 0010:atomic_inc arch/x86/include/asm/atomic.h:92 [inline]
RIP: 0010:kthread_stop+0x47/0x640 kernel/kthread.c:525
RSP: 0018:ffff8880932efc70 EFLAGS: 00010297
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
RAX: ffff8880a9fd4480 RBX: 0000000000000001 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000286
RBP: fffffffffffffffc R08: ffffffff8b9bd9f8 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff888237d64a18
R13: ffff888237d64a08 R14: fffffbfff1924320 R15: ffffffff898586c0
FS:  0000000000000000(0000) GS:ffff8880ba500000(0000) knlGS:0000000000000000
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
CR2: 000000000000001c CR3: 000000006d3ec000 CR4: 00000000001406e0
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3d) already exists on: batadv_slave_0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 vhci_shutdown_connection+0x12a/0x240 drivers/usb/usbip/vhci_hcd.c:1037
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
IPv6: ADDRCONF(NETDEV_UP): batadv_slave_0: link is not ready
 event_handler+0x1c3/0x4a0 drivers/usb/usbip/usbip_event.c:92
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
batman_adv: batadv0: Interface activated: batadv_slave_0
IPv6: ADDRCONF(NETDEV_CHANGE): macvtap0: link becomes ready
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
IPv6: ADDRCONF(NETDEV_CHANGE): macsec0: link becomes ready
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Code: 
IPv6: ADDRCONF(NETDEV_CHANGE): batadv_slave_0: link becomes ready
00 65 8b 1d cc 15 c9 7e 83 fb 07 0f 87 
IPv6: ADDRCONF(NETDEV_CHANGE): veth0_to_batadv: link becomes ready
5b 04 00 00 e8 1e d6 1e 00 89 db 48 
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1
0f a3 1d 9c 50 d0 08 0f 82 a2 03 00 00 e8 
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
09 
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1
d6 
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
1e 
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1
00 
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
<f0> 
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1
ff 45 20 48 8d 7d 24 48 b8 00 00 00 
batman_adv: It is strongly recommended to keep mac addresses unique to avoid problems!
00 00 fc ff df 48 89 fa 
RIP: atomic_inc arch/x86/include/asm/atomic.h:92 [inline] RSP: ffff8880932efc70
RIP: kthread_stop+0x47/0x640 kernel/kthread.c:525 RSP: ffff8880932efc70
batman_adv: The newly added mac address (aa:aa:aa:aa:aa:3e) already exists on: batadv_slave_1
CR2: 000000000000001c
---[ end trace 3072a113a50075ce ]---