KASAN: null-ptr-deref Write in corrupted

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    eda809ae Merge tag 'scsi-fixes' of git://git.kernel.org/pu..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15fb35db500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=940a11083ffdc81
dashboard link: https://syzkaller.appspot.com/bug?extid=500bfbdf35e54e9b35f7
compiler:       gcc (GCC) 10.1.0-syz 20200507
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14255e0b500000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+500bfbdf35e54e9b35f7@xxxxxxxxxxxxxxxxxxxxxxxxx

vhci_hcd: stop threads
vhci_hcd: release socket
vhci_hcd: disconnect device
==================================================================
BUG: KASAN: null-ptr-deref in instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
BUG: KASAN: null-ptr-deref in atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:142 [inline]
BUG: KASAN: null-ptr-deref in __refcount_add include/linux/refcount.h:193 [inline]
BUG: KASAN: null-ptr-deref in __refcount_inc include/linux/refcount.h:250 [inline]
BUG: KASAN: null-ptr-deref in refcount_inc include/linux/refcount.h:267 [inline]
BUG: KASAN: null-ptr-deref in get_task_struct include/linux/sched/task.h:102 [inline]
BUG: KASAN: null-ptr-deref in kthread_stop+0x90/0x720 kernel/kthread.c:591
Write of size 4 at addr 0000000000000024 by task kworker/u4:11/471

CPU: 0 PID: 471 Comm: kworker/u4:11 Not tainted 5.11.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: usbip_event event_handler
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 __kasan_report mm/kasan/report.c:400 [inline]
 kasan_report.cold+0x5f/0xd5 mm/kasan/report.c:413


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