[syzbot] KASAN: null-ptr-deref Write in kill_f2fs_super

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    493ffd6605b2 Merge tag 'ucount-rlimits-cleanups-for-v5.19'..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=15fc0252880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d19f5d16783f901
dashboard link: https://syzkaller.appspot.com/bug?extid=729c925c2d9fc495ddee
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=15714978880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1152f7cc880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f1ff6481e26f/disk-493ffd66.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/101bd3c7ae47/vmlinux-493ffd66.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/dd1108445544/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+729c925c2d9fc495ddee@xxxxxxxxxxxxxxxxxxxxxxxxx

loop0: detected capacity change from 0 to 264192
F2FS-fs (loop0): invalid crc_offset: 0
F2FS-fs (loop0): Found nat_bits in checkpoint
F2FS-fs (loop0): Mounted with checkpoint version = 3651456e
==================================================================
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/linux/atomic/atomic-instrumented.h:116 [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:110 [inline]
BUG: KASAN: null-ptr-deref in kthread_stop+0x2a/0x210 kernel/kthread.c:703
Write of size 4 at addr 000000000000001c by task syz-executor364/3613

CPU: 1 PID: 3613 Comm: syz-executor364 Not tainted 6.0.0-syzkaller-09423-g493ffd6605b2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/22/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
 print_report+0xf1/0x1f0 mm/kasan/report.c:436
 kasan_report+0xc3/0xf0 mm/kasan/report.c:495
 kasan_check_range+0x2a7/0x2e0 mm/kasan/generic.c:189
 instrument_atomic_read_write include/linux/instrumented.h:101 [inline]
 atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:116 [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:110 [inline]
 kthread_stop+0x2a/0x210 kernel/kthread.c:703
 kill_f2fs_super+0xe6/0x3c0 fs/f2fs/super.c:4522
 deactivate_locked_super+0xa7/0xf0 fs/super.c:331
 cleanup_mnt+0x4ce/0x560 fs/namespace.c:1186
 task_work_run+0x146/0x1c0 kernel/task_work.c:177
 exit_task_work include/linux/task_work.h:38 [inline]
 do_exit+0x6b2/0x2280 kernel/exit.c:813
 do_group_exit+0x1fd/0x2b0 kernel/exit.c:943
 __do_sys_exit_group kernel/exit.c:954 [inline]
 __se_sys_exit_group kernel/exit.c:952 [inline]
 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:952
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f8264e76359
Code: Unable to access opcode bytes at 0x7f8264e7632f.
RSP: 002b:00007fffe8489448 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 00007f8264eee410 RCX: 00007f8264e76359
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffffffffffffffc0 R09: 0000000000000000
R10: 0000000000180020 R11: 0000000000000246 R12: 00007f8264eee410
R13: 0000000000000001 R14: 0000000000000000 R15: 0000000000000001
 </TASK>
==================================================================


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