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: 51 Comm: kworker/u4:3 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: 60000113
sp : 8467be48  ip : 8467bdf8  fp : 8467be64
r10: 846a8368  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: 86ebe800  DAC: fffffffd
Process kworker/u4:3 (pid: 51, stack limit = 0x8467a210)
Stack: (0x8467be48 to 0x8467c000)
be40:                   846a8360 839e8744 842cd4bc 839e8768 8467beac 8467be68
be60: 81200fc8 80273928 8467be94 811fcfd8 88fa6100 00000000 88fa6100 e6e5e17a
be80: 842cd4bc 846a8360 839e8744 842cd4bc 839e8768 00000100 82a9ab98 846a8368
bea0: 8467bedc 8467beb0 811fd00c 81200f4c 811fcf3c 839e8770 844d3200 84420000
bec0: 845b5c00 83ac7572 83822c98 00000088 8467bf3c 8467bee0 802696a4 811fcf48
bee0: 00000001 00000000 802695e4 84420000 00000000 00000000 839e8770 83fec88c
bf00: 00000000 82a9abf0 00000000 e6e5e17a 8213beb4 844d3200 84420000 844d3214
bf20: 84420038 83806d00 8467a000 00000088 8467bf74 8467bf40 80269dcc 802693dc
bf40: 8467bf74 83806d00 80271b6c 844d3280 844e12c0 8467a000 00000000 80269d68
bf60: 844d3200 84525e64 8467bfac 8467bf78 80271f40 80269d74 80258640 844d32c4
bf80: 00000000 844e12c0 80271dbc 00000000 00000000 00000000 00000000 00000000
bfa0: 00000000 8467bfb0 80200114 80271dc8 00000000 00000000 00000000 00000000
bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
bfe0: 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 r4:846a8360
[<81200f40>] (vhci_shutdown_connection) from [<811fd00c>] (event_handler+0xd0/0x1c0 drivers/usb/usbip/usbip_event.c:78)
 r10:846a8368 r9:82a9ab98 r8:00000100 r7:839e8768 r6:842cd4bc r5:839e8744
 r4:846a8360
[<811fcf3c>] (event_handler) from [<802696a4>] (process_one_work+0x2d4/0x998 kernel/workqueue.c:2275)
 r10:00000088 r9:83822c98 r8:83ac7572 r7:845b5c00 r6:84420000 r5:844d3200
 r4:839e8770 r3:811fcf3c
[<802693d0>] (process_one_work) from [<80269dcc>] (worker_thread+0x64/0x54c kernel/workqueue.c:2421)
 r10:00000088 r9:8467a000 r8:83806d00 r7:84420038 r6:844d3214 r5:84420000
 r4:844d3200
[<80269d68>] (worker_thread) from [<80271f40>] (kthread+0x184/0x1a4 kernel/kthread.c:292)
 r10:84525e64 r9:844d3200 r8:80269d68 r7:00000000 r6:8467a000 r5:844e12c0
 r4:844d3280
[<80271dbc>] (kthread) from [<80200114>] (ret_from_fork+0x14/0x20 arch/arm/kernel/entry-common.S:158)
Exception stack(0x8467bfb0 to 0x8467bff8)
bfa0:                                     00000000 00000000 00000000 00000000
bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
 r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:80271dbc
 r4:844e12c0
Code: e3130001 1a000079 e2845008 f595f000 (e1953f9f) 
---[ end trace aca94061110138b3 ]---