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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:111 [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+0x58/0x4f0 kernel/kthread.c:643
Write of size 4 at addr 000000000000001c by task syz-executor.0/5779

CPU: 1 PID: 5779 Comm: syz-executor.0 Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022
Call Trace:
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x57/0x7d lib/dump_stack.c:105
 __kasan_report mm/kasan/report.c:423 [inline]
 kasan_report.cold+0x66/0xdf mm/kasan/report.c:436
 check_region_inline mm/kasan/generic.c:183 [inline]
 kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_fetch_add_relaxed include/asm-generic/atomic-instrumented.h:111 [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+0x58/0x4f0 kernel/kthread.c:643
 kill_f2fs_super+0xd3/0x340 fs/f2fs/super.c:4409
 deactivate_locked_super+0x7b/0x130 fs/super.c:335
 cleanup_mnt+0x324/0x4d0 fs/namespace.c:1136
 task_work_run+0xc0/0x160 kernel/task_work.c:164
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:175 [inline]
 exit_to_user_mode_prepare+0x27e/0x290 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:302
 do_syscall_64+0x42/0x80 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x7f4888dbda67
Code: ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 31 f6 e9 09 00 00 00 66 0f 1f 84 00 00 00 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe9bd642f8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007f4888dbda67
RDX: 00007ffe9bd643c9 RSI: 000000000000000a RDI: 00007ffe9bd643c0
RBP: 00007ffe9bd643c0 R08: 00000000ffffffff R09: 00007ffe9bd64190
R10: 0000555556b918b3 R11: 0000000000000246 R12: 00007f4888e16826
R13: 00007ffe9bd65480 R14: 0000555556b91810 R15: 00007ffe9bd654c0
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