vhci_hcd vhci_hcd.0: port 3 already used
vhci_hcd vhci_hcd.0: port 1 already used
vhci_hcd vhci_hcd.0: port 2 already used
vhci_hcd vhci_hcd.0: port 0 already used
vhci_hcd vhci_hcd.0: port 1 already used
BUG: unable to handle kernel NULL pointer dereference at 000000000000001c
vhci_hcd vhci_hcd.0: port 2 already used
IP: atomic_inc arch/x86/include/asm/atomic.h:92 [inline]
IP: kthread_stop+0x47/0x640 kernel/kthread.c:525
PGD a1042067 P4D a1042067 PUD a5b89067 PMD 0 
Oops: 0002 [#1] PREEMPT SMP KASAN
Modules linked in:
CPU: 1 PID: 25 Comm: kworker/u4:2 Not tainted 4.14.198-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: usbip_event event_handler
task: ffff8880a9ab66c0 task.stack: ffff8880a9ab8000
RIP: 0010:atomic_inc arch/x86/include/asm/atomic.h:92 [inline]
RIP: 0010:kthread_stop+0x47/0x640 kernel/kthread.c:525
vhci_hcd vhci_hcd.0: pdev(2) rhport(3) sockfd(9)
RSP: 0018:ffff8880a9abfc68 EFLAGS: 00010297
vhci_hcd vhci_hcd.0: devid(0) speed(2) speed_str(full-speed)
vhci_hcd vhci_hcd.0: port 0 already used
RAX: ffff8880a9ab66c0 RBX: 0000000000000001 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 00000000ffffffff RDI: 0000000000000286
RBP: fffffffffffffffc R08: ffffffff8951e65e R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88809fb24e18
R13: ffff88809fb24e08 R14: dead000000000100 R15: ffff88809fb24e20
FS:  0000000000000000(0000) GS:ffff8880aeb00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000000001c CR3: 000000009fe5e000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 vhci_shutdown_connection+0x117/0x1b0 drivers/usb/usbip/vhci_hcd.c:1035
vhci_hcd vhci_hcd.0: port 1 already used
 event_handler+0x18a/0x420 drivers/usb/usbip/usbip_event.c:92
vhci_hcd: connection closed
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
vhci_hcd vhci_hcd.0: port 1 already used
 kthread+0x30d/0x420 kernel/kthread.c:232
vhci_hcd vhci_hcd.0: port 2 already used
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Code: 00 65 8b 1d 2c a9 c4 7e 83 fb 3f 0f 87 5b 04 00 00 e8 fe be 1e 00 89 
vhci_hcd vhci_hcd.0: port 3 already used
db 48 0f a3 1d bc 22 56 07 0f 82 a2 03 00 00 e8 e9 be 1e 00 <f0> ff 45 20 48 8d 7d 24 48 b8 00 00 00 00 00 fc ff df 48 89 fa 
RIP: atomic_inc arch/x86/include/asm/atomic.h:92 [inline] RSP: ffff8880a9abfc68
RIP: kthread_stop+0x47/0x640 kernel/kthread.c:525 RSP: ffff8880a9abfc68
CR2: 000000000000001c
---[ end trace ce26a6397f249f38 ]---