[syzbot] [f2fs?] kernel BUG in f2fs_put_super (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ccd1cdca5cd4 Merge tag 'nfsd-6.19-1' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=136b2f1a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1f2b6fe1fdf1a00b
dashboard link: https://syzkaller.appspot.com/bug?extid=c0a575209250b34549be
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f9756bdd2faf/disk-ccd1cdca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f03680f500a5/vmlinux-ccd1cdca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ed5a6d62c5ac/bzImage-ccd1cdca.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c0a575...@syzkaller.appspotmail.com

F2FS-fs (loop5): detect filesystem reference count leak during umount, type: 2, count: -1
------------[ cut here ]------------
kernel BUG at fs/f2fs/super.c:2008!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 0 UID: 0 PID: 5980 Comm: syz-executor Not tainted syzkaller #0 PREEMPT_{RT,(full)}
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:f2fs_put_super+0x1165/0x1170 fs/f2fs/super.c:2008
Code: fd 41 bf 0c 00 00 00 48 89 df 44 89 fe e8 23 3f 00 00 48 89 df 31 f6 48 c7 c2 00 da 33 8b 44 89 f9 49 89 c0 e8 7c 70 fd ff 90 <0f> 0b 66 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900056579a0 EFLAGS: 00010246
RAX: b18dcddbdfba5600 RBX: ffff88805e754000 RCX: b18dcddbdfba5600
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90005657b98 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff52000acaebd R12: ffff88805e754000
R13: dffffc0000000000 R14: 00000000ffffffff R15: 0000000000000002
FS: 000055556c854500(0000) GS:ffff888126cef000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fad42ebb000 CR3: 0000000029164000 CR4: 00000000003526f0
Call Trace:
<TASK>
generic_shutdown_super+0x135/0x2c0 fs/super.c:643
kill_block_super+0x44/0x90 fs/super.c:1722
kill_f2fs_super+0x39f/0x6c0 fs/f2fs/super.c:5454
deactivate_locked_super+0xbc/0x130 fs/super.c:474
cleanup_mnt+0x425/0x4c0 fs/namespace.c:1318
task_work_run+0x1d4/0x260 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
exit_to_user_mode_loop+0xef/0x4e0 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x2b7/0xf80 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f142cea0a77
Code: a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 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 00 f0 ff ff 77 01 c3 48 c7 c2 a8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffc21036858 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 00007f142cf23d7d RCX: 00007f142cea0a77
RDX: 0000000000000000 RSI: 0000000000000009 RDI: 00007ffc21036910
RBP: 00007ffc21036910 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007ffc210379a0
R13: 00007f142cf23d7d R14: 000000000002714a R15: 00007ffc210379e0
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:f2fs_put_super+0x1165/0x1170 fs/f2fs/super.c:2008
Code: fd 41 bf 0c 00 00 00 48 89 df 44 89 fe e8 23 3f 00 00 48 89 df 31 f6 48 c7 c2 00 da 33 8b 44 89 f9 49 89 c0 e8 7c 70 fd ff 90 <0f> 0b 66 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900056579a0 EFLAGS: 00010246
RAX: b18dcddbdfba5600 RBX: ffff88805e754000 RCX: b18dcddbdfba5600
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90005657b98 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffff52000acaebd R12: ffff88805e754000
R13: dffffc0000000000 R14: 00000000ffffffff R15: 0000000000000002
FS: 000055556c854500(0000) GS:ffff888126def000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fab7d2756c0 CR3: 0000000029164000 CR4: 00000000003526f0


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