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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:104 [inline]
BUG: KASAN: null-ptr-deref in kthread_stop+0xb8/0x860 kernel/kthread.c:616
Write of size 4 at addr 000000000000001c by task kworker/u4:0/7

CPU: 1 PID: 7 Comm: kworker/u4:0 Not tainted 5.12.0-rc2-syzkaller-00059-g144c79ef3353 #0
Hardware name: linux,dummy-virt (DT)
Workqueue: usbip_event event_handler
Call trace:
 dump_backtrace+0x0/0x3e0 arch/arm64/include/asm/pointer_auth.h:76
 show_stack+0x18/0x70 arch/arm64/kernel/stacktrace.c:191
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x120/0x1a8 lib/dump_stack.c:120
 __kasan_report mm/kasan/report.c:403 [inline]
 kasan_report+0x128/0x200 mm/kasan/report.c:416
 check_region_inline mm/kasan/generic.c:170 [inline]
 kasan_check_range+0xfc/0x1a4 mm/kasan/generic.c:186
 __kasan_check_write+0x34/0x60 mm/kasan/shadow.c:37
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:142 [inline]
 __refcount_add include/linux/refcount.h:193 [inline]
 __refcount_inc include/linux/refcount.h:250 [inline]
 refcount_inc include/linux/refcount.h:267 [inline]
 get_task_struct include/linux/sched/task.h:104 [inline]
 kthread_stop+0xb8/0x860 kernel/kthread.c:616
 vhci_shutdown_connection+0x108/0x854 drivers/usb/usbip/vhci_hcd.c:1023
 event_handler+0x174/0x3d0 drivers/usb/usbip/usbip_event.c:78
 process_one_work+0x798/0x1764 kernel/workqueue.c:2275
 worker_thread+0x3d4/0xcd0 kernel/workqueue.c:2421
 kthread+0x320/0x3bc kernel/kthread.c:292
 ret_from_fork+0x10/0x3c arch/arm64/kernel/entry.S:958
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