8<--- cut here ---
Unable to handle kernel NULL pointer dereference at virtual address 00000004
pgd = 80003000
[00000004] *pgd=80000080004003, *pmd=00000000
Internal error: Oops: 207 [#1] PREEMPT SMP ARM
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 1 PID: 4943 Comm: kworker/u4:1 Not tainted 5.12.0-rc2-syzkaller #0
Hardware name: ARM-Versatile Express
Workqueue: usbip_event event_handler
PC is at atomic_fetch_add_relaxed arch/arm/include/asm/atomic.h:223 [inline]
PC is at __refcount_add include/linux/refcount.h:193 [inline]
PC is at __refcount_inc include/linux/refcount.h:250 [inline]
PC is at refcount_inc include/linux/refcount.h:267 [inline]
PC is at get_task_struct include/linux/sched/task.h:104 [inline]
PC is at kthread_stop+0x60/0x4e4 kernel/kthread.c:616
LR is at __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:70
pc : [<8027397c>]    lr : [<82135794>]    psr: 60000013
sp : 8902de48  ip : 8902ddf8  fp : 8902de64
r10: 846a3368  r9 : 82a9b834  r8 : 00000100
r7 : 839e88d0  r6 : 83822c98  r5 : 00000004  r4 : fffffffc
r3 : 00000000  r2 : 00000000  r1 : 5a91b000  r0 : 00000001
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 30c5387d  Table: 886a2000  DAC: 00000000
Process kworker/u4:1 (pid: 4943, stack limit = 0x8902c210)
Stack: (0x8902de48 to 0x8902e000)
de40:                   846a3360 839e88ac 842cd56c 839e88d0 8902deac 8902de68
de60: 812035f8 80273928 8902de94 811ff608 891705c0 00000000 891705c0 e6e5e17a
de80: 842cd56c 846a3360 839e88ac 842cd56c 839e88d0 00000100 82a9b834 846a3368
dea0: 8902dedc 8902deb0 811ff63c 8120357c 811ff56c 839e88d8 88ec0580 84420000
dec0: 86a10200 83ac76b2 83822c98 00000088 8902df3c 8902dee0 802696a4 811ff578
dee0: 00000001 00000000 802695e4 84420000 00000000 00000000 839e88d8 83fecbac
df00: 00000000 82a9b88c 00000000 e6e5e17a 8213e4e4 88ec0580 84420000 88ec0594
df20: 84420038 83806d00 8902c000 00000088 8902df74 8902df40 80269dcc 802693dc
df40: 8902df74 83806d00 80271b6c 88ec0300 88ef41c0 8902c000 00000000 80269d68
df60: 88ec0580 845bde64 8902dfac 8902df78 80271f40 80269d74 80258640 88ec0344
df80: 00000000 88ef41c0 80271dbc 00000000 00000000 00000000 00000000 00000000
dfa0: 00000000 8902dfb0 80200114 80271dc8 00000000 00000000 00000000 00000000
dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
Backtrace: 
[<8027391c>] (kthread_stop) from [<812035f8>] (vhci_shutdown_connection+0x88/0x3a0 drivers/usb/usbip/vhci_hcd.c:1023)
 r7:839e88d0 r6:842cd56c r5:839e88ac r4:846a3360
[<81203570>] (vhci_shutdown_connection) from [<811ff63c>] (event_handler+0xd0/0x1c0 drivers/usb/usbip/usbip_event.c:78)
 r10:846a3368 r9:82a9b834 r8:00000100 r7:839e88d0 r6:842cd56c r5:839e88ac
 r4:846a3360
[<811ff56c>] (event_handler) from [<802696a4>] (process_one_work+0x2d4/0x998 kernel/workqueue.c:2275)
 r10:00000088 r9:83822c98 r8:83ac76b2 r7:86a10200 r6:84420000 r5:88ec0580
 r4:839e88d8 r3:811ff56c
[<802693d0>] (process_one_work) from [<80269dcc>] (worker_thread+0x64/0x54c kernel/workqueue.c:2421)
 r10:00000088 r9:8902c000 r8:83806d00 r7:84420038 r6:88ec0594 r5:84420000
 r4:88ec0580
[<80269d68>] (worker_thread) from [<80271f40>] (kthread+0x184/0x1a4 kernel/kthread.c:292)
 r10:845bde64 r9:88ec0580 r8:80269d68 r7:00000000 r6:8902c000 r5:88ef41c0
 r4:88ec0300
[<80271dbc>] (kthread) from [<80200114>] (ret_from_fork+0x14/0x20 arch/arm/kernel/entry-common.S:158)
Exception stack(0x8902dfb0 to 0x8902dff8)
dfa0:                                     00000000 00000000 00000000 00000000
dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
dfe0: 00000000 00000000 00000000 00000000 00000013 00000000
 r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:80271dbc
 r4:88ef41c0
Code: e3130001 1a000079 e2845008 f595f000 (e1953f9f) 
---[ end trace 307887731c58bfd7 ]---