8<--- cut here ---
Unable to handle kernel NULL pointer dereference at virtual address 00000004
pgd = 8cd9f6fb
[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: 24 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 : [<82773fac>]    psr: 60000013
sp : 851f1e48  ip : 851f1df8  fp : 851f1e64
r10: 851db368  r9 : 832100f4  r8 : 00000100
r7 : 8427dc88  r6 : 8404ec98  r5 : 00000004  r4 : fffffffc
r3 : 00000000  r2 : 00000000  r1 : 5a109000  r0 : 00000001
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 30c5387d  Table: 8a309bc0  DAC: 00000000
Process kworker/u4:1 (pid: 24, stack limit = 0x61e1d256)
Stack: (0x851f1e48 to 0x851f2000)
1e40:                   851db360 8427dc64 84bdb07c 8427dc88 851f1eac 851f1e68
1e60: 8179f3f8 80273928 851f1e94 8179b408 8b074300 00000000 8b074300 79568410
1e80: 84bdb07c 851db360 8427dc64 84bdb07c 8427dc88 00000100 832100f4 851db368
1ea0: 851f1edc 851f1eb0 8179b43c 8179f37c 8179b36c 8427dc90 850f5100 85020000
1ec0: 851c7200 84367a02 8404ec98 00000088 851f1f3c 851f1ee0 802696a4 8179b378
1ee0: 00000001 00000000 802695e4 85020000 00000000 00000000 8427dc90 848c2960
1f00: 00000000 8321014c 00000000 79568410 8277ccfc 850f5100 85020000 850f5114
1f20: 85020038 84006d00 851f0000 00000088 851f1f74 851f1f40 80269dcc 802693dc
1f40: 851f1f74 84006d00 80271b6c 850f5180 850f4a40 851f0000 00000000 80269d68
1f60: 850f5100 85147e64 851f1fac 851f1f78 80271f40 80269d74 80258640 850f51c4
1f80: 00000000 850f4a40 80271dbc 00000000 00000000 00000000 00000000 00000000
1fa0: 00000000 851f1fb0 80200114 80271dc8 00000000 00000000 00000000 00000000
1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
1fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
Backtrace: 
[<8027391c>] (kthread_stop) from [<8179f3f8>] (vhci_shutdown_connection+0x88/0x3a0 drivers/usb/usbip/vhci_hcd.c:1023)
 r7:8427dc88 r6:84bdb07c r5:8427dc64 r4:851db360
[<8179f370>] (vhci_shutdown_connection) from [<8179b43c>] (event_handler+0xd0/0x1c0 drivers/usb/usbip/usbip_event.c:78)
 r10:851db368 r9:832100f4 r8:00000100 r7:8427dc88 r6:84bdb07c r5:8427dc64
 r4:851db360
[<8179b36c>] (event_handler) from [<802696a4>] (process_one_work+0x2d4/0x998 kernel/workqueue.c:2275)
 r10:00000088 r9:8404ec98 r8:84367a02 r7:851c7200 r6:85020000 r5:850f5100
 r4:8427dc90 r3:8179b36c
[<802693d0>] (process_one_work) from [<80269dcc>] (worker_thread+0x64/0x54c kernel/workqueue.c:2421)
 r10:00000088 r9:851f0000 r8:84006d00 r7:85020038 r6:850f5114 r5:85020000
 r4:850f5100
[<80269d68>] (worker_thread) from [<80271f40>] (kthread+0x184/0x1a4 kernel/kthread.c:292)
 r10:85147e64 r9:850f5100 r8:80269d68 r7:00000000 r6:851f0000 r5:850f4a40
 r4:850f5180
[<80271dbc>] (kthread) from [<80200114>] (ret_from_fork+0x14/0x20 arch/arm/kernel/entry-common.S:158)
Exception stack(0x851f1fb0 to 0x851f1ff8)
1fa0:                                     00000000 00000000 00000000 00000000
1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
1fe0: 00000000 00000000 00000000 00000000 00000013 00000000
 r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:80271dbc
 r4:850f4a40
Code: e3130001 1a000079 e2845008 f595f000 (e1953f9f) 
---[ end trace 67de7b7cc43ae9f2 ]---