vhci_hcd: disconnect device
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: 8660 Comm: kworker/u4:7 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: 60000113
sp : 87e47e48  ip : 87e47df8  fp : 87e47e64
r10: 84737368  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: 88a04980  DAC: 00000000
Process kworker/u4:7 (pid: 8660, stack limit = 0x87e46210)
Stack: (0x87e47e48 to 0x87e48000)
7e40:                   84737360 839e88ac 842cd56c 839e88d0 87e47eac 87e47e68
7e60: 812035f8 80273928 87e47e94 811ff608 892abac0 00000000 892abac0 e6e5e17a
7e80: 842cd56c 84737360 839e88ac 842cd56c 839e88d0 00000100 82a9b834 84737368
7ea0: 87e47edc 87e47eb0 811ff63c 8120357c 811ff56c 839e88d8 8907f480 84420000
7ec0: 8478d200 83ac76b2 83822c98 00000088 87e47f3c 87e47ee0 802696a4 811ff578
7ee0: 00000001 00000000 802695e4 84420000 00000000 00000000 839e88d8 83ff5bd0
7f00: 00000000 82a9b88c 00000000 e6e5e17a 8213e4e4 8907f480 84420000 8907f494
7f20: 84420038 83806d00 87e46000 00000088 87e47f74 87e47f40 80269dcc 802693dc
7f40: 87e47f74 83806d00 80271b6c 8907f500 88f4cf40 87e46000 00000000 80269d68
7f60: 8907f480 846d3e64 87e47fac 87e47f78 80271f40 80269d74 80258640 8907f544
7f80: 00000000 88f4cf40 80271dbc 00000000 00000000 00000000 00000000 00000000
7fa0: 00000000 87e47fb0 80200114 80271dc8 00000000 00000000 00000000 00000000
7fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
7fe0: 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 r4:84737360
[<81203570>] (vhci_shutdown_connection) from [<811ff63c>] (event_handler+0xd0/0x1c0 drivers/usb/usbip/usbip_event.c:78)
 r10:84737368 r9:82a9b834 r8:00000100 r7:839e88d0 r6:842cd56c r5:839e88ac
 r4:84737360
[<811ff56c>] (event_handler) from [<802696a4>] (process_one_work+0x2d4/0x998 kernel/workqueue.c:2275)
 r10:00000088 r9:83822c98 r8:83ac76b2 r7:8478d200 r6:84420000 r5:8907f480
 r4:839e88d8 r3:811ff56c
[<802693d0>] (process_one_work) from [<80269dcc>] (worker_thread+0x64/0x54c kernel/workqueue.c:2421)
 r10:00000088 r9:87e46000 r8:83806d00 r7:84420038 r6:8907f494 r5:84420000
 r4:8907f480
[<80269d68>] (worker_thread) from [<80271f40>] (kthread+0x184/0x1a4 kernel/kthread.c:292)
 r10:846d3e64 r9:8907f480 r8:80269d68 r7:00000000 r6:87e46000 r5:88f4cf40
 r4:8907f500
[<80271dbc>] (kthread) from [<80200114>] (ret_from_fork+0x14/0x20 arch/arm/kernel/entry-common.S:158)
Exception stack(0x87e47fb0 to 0x87e47ff8)
7fa0:                                     00000000 00000000 00000000 00000000
7fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
7fe0: 00000000 00000000 00000000 00000000 00000013 00000000
 r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:80271dbc
 r4:88f4cf40
Code: e3130001 1a000079 e2845008 f595f000 (e1953f9f) 
---[ end trace 3865d2f297e31bfe ]---