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: 0 PID: 11721 Comm: kworker/u4:0 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 : [<82133164>]    psr: 60000013
sp : 84525e48  ip : 84525df8  fp : 84525e64
r10: 846d8368  r9 : 82a9ab98  r8 : 00000100
r7 : 839e8768  r6 : 83822c98  r5 : 00000004  r4 : fffffffc
r3 : 00000000  r2 : 00000000  r1 : 5a905000  r0 : 00000001
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
Control: 30c5387d  Table: 88a15a00  DAC: fffffffd
Process kworker/u4:0 (pid: 11721, stack limit = 0x84524210)
Stack: (0x84525e48 to 0x84526000)
5e40:                   846d8360 839e8744 842cd4bc 839e8768 84525eac 84525e68
5e60: 81200fc8 80273928 84525e94 811fcfd8 88f54300 00000000 88f54300 e6e5e17a
5e80: 842cd4bc 846d8360 839e8744 842cd4bc 839e8768 00000100 82a9ab98 846d8368
5ea0: 84525edc 84525eb0 811fd00c 81200f4c 811fcf3c 839e8770 8877b080 84420000
5ec0: 84417e00 83ac7572 83822c98 00000088 84525f3c 84525ee0 802696a4 811fcf48
5ee0: 00000001 00000000 802695e4 84420000 00000000 00000000 839e8770 83ff1e7c
5f00: 00000000 82a9abf0 00000000 e6e5e17a 8213beb4 8877b080 84420000 8877b094
5f20: 84420038 83806d00 84524000 00000088 84525f74 84525f40 80269dcc 802693dc
5f40: 84525f74 83806d00 80271b6c 8877b380 88a4e880 84524000 00000000 80269d68
5f60: 8877b080 8909de64 84525fac 84525f78 80271f40 80269d74 80258640 8877b3c4
5f80: 00000000 88a4e880 80271dbc 00000000 00000000 00000000 00000000 00000000
5fa0: 00000000 84525fb0 80200114 80271dc8 00000000 00000000 00000000 00000000
5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
5fe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
Backtrace: 
[<8027391c>] (kthread_stop) from [<81200fc8>] (vhci_shutdown_connection+0x88/0x3a0 drivers/usb/usbip/vhci_hcd.c:1023)
 r7:839e8768 r6:842cd4bc r5:839e8744 r4:846d8360
[<81200f40>] (vhci_shutdown_connection) from [<811fd00c>] (event_handler+0xd0/0x1c0 drivers/usb/usbip/usbip_event.c:78)
 r10:846d8368 r9:82a9ab98 r8:00000100 r7:839e8768 r6:842cd4bc r5:839e8744
 r4:846d8360
[<811fcf3c>] (event_handler) from [<802696a4>] (process_one_work+0x2d4/0x998 kernel/workqueue.c:2275)
 r10:00000088 r9:83822c98 r8:83ac7572 r7:84417e00 r6:84420000 r5:8877b080
 r4:839e8770 r3:811fcf3c
[<802693d0>] (process_one_work) from [<80269dcc>] (worker_thread+0x64/0x54c kernel/workqueue.c:2421)
 r10:00000088 r9:84524000 r8:83806d00 r7:84420038 r6:8877b094 r5:84420000
 r4:8877b080
[<80269d68>] (worker_thread) from [<80271f40>] (kthread+0x184/0x1a4 kernel/kthread.c:292)
 r10:8909de64 r9:8877b080 r8:80269d68 r7:00000000 r6:84524000 r5:88a4e880
 r4:8877b380
[<80271dbc>] (kthread) from [<80200114>] (ret_from_fork+0x14/0x20 arch/arm/kernel/entry-common.S:158)
Exception stack(0x84525fb0 to 0x84525ff8)
5fa0:                                     00000000 00000000 00000000 00000000
5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
 r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:80271dbc
 r4:88a4e880
Code: e3130001 1a000079 e2845008 f595f000 (e1953f9f) 
---[ end trace 4f55bd8c829edd07 ]---