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: 14568 Comm: kworker/u4:2 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 : [<8027398c>]    lr : [<82135db4>]    psr: 60000013
sp : 8910be48  ip : 8910bdf8  fp : 8910be64
r10: 8464c368  r9 : 82a9b7d8  r8 : 00000100
r7 : 839e88d0  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: 88f56580  DAC: fffffffd
Process kworker/u4:2 (pid: 14568, stack limit = 0x8910a210)
Stack: (0x8910be48 to 0x8910c000)
be40:                   8464c360 839e88ac 842cd56c 839e88d0 8910beac 8910be68
be60: 81203a98 80273938 8910be94 811ffaa8 89078440 00000000 89078440 e6e5e17a
be80: 842cd56c 8464c360 839e88ac 842cd56c 839e88d0 00000100 82a9b7d8 8464c368
bea0: 8910bedc 8910beb0 811ffadc 81203a1c 811ffa0c 839e88d8 89063d00 84420000
bec0: 84f09400 83ac76b2 83822c98 00000088 8910bf3c 8910bee0 802696b4 811ffa18
bee0: 00000001 00000000 802695f4 84420000 00000000 00000000 839e88d8 83ff2520
bf00: 00000000 82a9b830 00000000 e6e5e17a 8213eb04 89063d00 84420000 89063d14
bf20: 84420038 83806d00 8910a000 00000088 8910bf74 8910bf40 80269ddc 802693ec
bf40: 8910bf74 83806d00 80271b7c 890e5f80 88f7d540 8910a000 00000000 80269d78
bf60: 89063d00 89139e64 8910bfac 8910bf78 80271f50 80269d84 80258650 890e5fc4
bf80: 00000000 88f7d540 80271dcc 00000000 00000000 00000000 00000000 00000000
bfa0: 00000000 8910bfb0 80200114 80271dd8 00000000 00000000 00000000 00000000
bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
bfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
Backtrace: 
[<8027392c>] (kthread_stop) from [<81203a98>] (vhci_shutdown_connection+0x88/0x3a0 drivers/usb/usbip/vhci_hcd.c:1023)
 r7:839e88d0 r6:842cd56c r5:839e88ac r4:8464c360
[<81203a10>] (vhci_shutdown_connection) from [<811ffadc>] (event_handler+0xd0/0x1c0 drivers/usb/usbip/usbip_event.c:78)
 r10:8464c368 r9:82a9b7d8 r8:00000100 r7:839e88d0 r6:842cd56c r5:839e88ac
 r4:8464c360
[<811ffa0c>] (event_handler) from [<802696b4>] (process_one_work+0x2d4/0x998 kernel/workqueue.c:2275)
 r10:00000088 r9:83822c98 r8:83ac76b2 r7:84f09400 r6:84420000 r5:89063d00
 r4:839e88d8 r3:811ffa0c
[<802693e0>] (process_one_work) from [<80269ddc>] (worker_thread+0x64/0x54c kernel/workqueue.c:2421)
 r10:00000088 r9:8910a000 r8:83806d00 r7:84420038 r6:89063d14 r5:84420000
 r4:89063d00
[<80269d78>] (worker_thread) from [<80271f50>] (kthread+0x184/0x1a4 kernel/kthread.c:292)
 r10:89139e64 r9:89063d00 r8:80269d78 r7:00000000 r6:8910a000 r5:88f7d540
 r4:890e5f80
[<80271dcc>] (kthread) from [<80200114>] (ret_from_fork+0x14/0x20 arch/arm/kernel/entry-common.S:158)
Exception stack(0x8910bfb0 to 0x8910bff8)
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 r5:80271dcc
 r4:88f7d540
Code: e3130001 1a000079 e2845008 f595f000 (e1953f9f) 
---[ end trace 195d440f6843ff19 ]---