[v6.1] WARNING in f2fs_rename2

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 50cbba13faa2 Linux 6.1.159
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=100e4b1a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=31ea1cecaf34f0db
dashboard link: https://syzkaller.appspot.com/bug?extid=bbc70371727b60dcc014
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ad0bd66715a/disk-50cbba13.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3284d626258e/vmlinux-50cbba13.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a1f92ca7bbfc/Image-50cbba13.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bbc703...@syzkaller.appspotmail.com

F2FS-fs (loop9): Try to recover 1th superblock, ret: 0
F2FS-fs (loop9): Mounted with checkpoint version = 48b305e4
F2FS-fs (loop9): f2fs_unlink: inode (ino=7) has zero i_nlink
------------[ cut here ]------------
WARNING: CPU: 1 PID: 5686 at fs/inode.c:332 drop_nlink+0xe4/0x138 fs/inode.c:332
Modules linked in:
CPU: 1 PID: 5686 Comm: syz.9.149 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : drop_nlink+0xe4/0x138 fs/inode.c:332
lr : drop_nlink+0xe4/0x138 fs/inode.c:332
sp : ffff8000210577a0
x29: ffff8000210577a0 x28: 0000000000000000 x27: ffff0000f5bc4700
x26: dfff800000000000 x25: ffff0000f5bc3e20 x24: 0000000000008000
x23: 1fffe0001eb788e9 x22: dfff800000000000 x21: 0000000000000000
x20: ffff0000f5bc4748 x19: ffff0000f5bc4700 x18: ffff800011a5bd40
x17: ffff800018184000 x16: ffff8000082cf240 x15: ffff800017c65000
x14: ffff0000cd20c218 x13: ffff0000cd20c2e0 x12: 0000000000080000
x11: 0000000000009e72 x10: ffff80002905e000 x9 : ffff8000089fdec0
x8 : 0000000000009e73 x7 : 0000000000000000 x6 : 0000000000000000
x5 : 0000000000000020 x4 : 0000000000000000 x3 : ffff8000082cf434
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
drop_nlink+0xe4/0x138 fs/inode.c:332
f2fs_i_links_write fs/f2fs/f2fs.h:3049 [inline]
f2fs_rename fs/f2fs/namei.c:992 [inline]
f2fs_rename2+0x11d4/0x1bd4 fs/f2fs/namei.c:1265
vfs_rename+0x954/0xdcc fs/namei.c:4882
do_renameat2+0x738/0xa54 fs/namei.c:5035
__do_sys_renameat2 fs/namei.c:5068 [inline]
__se_sys_renameat2 fs/namei.c:5065 [inline]
__arm64_sys_renameat2+0xe0/0xfc fs/namei.c:5065
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 284872
hardirqs last enabled at (284871): [<ffff8000083c0b24>] seqcount_lockdep_reader_access include/linux/seqlock.h:104 [inline]
hardirqs last enabled at (284871): [<ffff8000083c0b24>] ktime_get_coarse_real_ts64+0x114/0x244 kernel/time/timekeeping.c:2261
hardirqs last disabled at (284872): [<ffff8000118fa220>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last enabled at (284766): [<ffff8000080309e0>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (284764): [<ffff8000080309ac>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19
---[ end trace 0000000000000000 ]---


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 50cbba13faa2 Linux 6.1.159
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=17a9c3c2580000

kernel config: https://syzkaller.appspot.com/x/.config?x=31ea1cecaf34f0db
dashboard link: https://syzkaller.appspot.com/bug?extid=bbc70371727b60dcc014
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13383b1a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=179e4b1a580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7ad0bd66715a/disk-50cbba13.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3284d626258e/vmlinux-50cbba13.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a1f92ca7bbfc/Image-50cbba13.gz.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/32f82c28bb0d/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=12152e2a580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+bbc703...@syzkaller.appspotmail.com

F2FS-fs (loop0): Found nat_bits in checkpoint
F2FS-fs (loop0): Try to recover 1th superblock, ret: 0
F2FS-fs (loop0): Mounted with checkpoint version = 48b305e4
------------[ cut here ]------------
WARNING: CPU: 0 PID: 4531 at fs/inode.c:332 drop_nlink+0xe4/0x138 fs/inode.c:332
Modules linked in:
CPU: 0 PID: 4531 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : drop_nlink+0xe4/0x138 fs/inode.c:332
lr : drop_nlink+0xe4/0x138 fs/inode.c:332

sp : ffff8000214777a0
x29: ffff8000214777a0 x28: 0000000000000000 x27: ffff0000ea27a380
x26: dfff800000000000 x25: ffff0000ea2791c0 x24: 0000000000008000
x23: 1fffe0001d44f479 x22: dfff800000000000 x21: 0000000000000000
x20: ffff0000ea27a3c8 x19: ffff0000ea27a380 x18: ffff800011a5bd40

x17: ffff800018184000 x16: ffff8000082cf240 x15: ffff800017c65000

x14: ffff0000d4578a98 x13: ffff0000d4578b60 x12: 0000000000ff0100
x11: ff008000089fdec0 x10: 0000000000000000 x9 : ffff8000089fdec0
x8 : ffff0000d4578000 x7 : 0000000000000000 x6 : 0000000000000000
x5 : ffff80001833a7b0 x4 : 0000000000000002 x3 : ffff8000082cf434

x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
drop_nlink+0xe4/0x138 fs/inode.c:332
f2fs_i_links_write fs/f2fs/f2fs.h:3049 [inline]
f2fs_rename fs/f2fs/namei.c:992 [inline]
f2fs_rename2+0x11d4/0x1bd4 fs/f2fs/namei.c:1265
vfs_rename+0x954/0xdcc fs/namei.c:4882
do_renameat2+0x738/0xa54 fs/namei.c:5035
__do_sys_renameat2 fs/namei.c:5068 [inline]
__se_sys_renameat2 fs/namei.c:5065 [inline]
__arm64_sys_renameat2+0xe0/0xfc fs/namei.c:5065
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

irq event stamp: 272384
hardirqs last enabled at (272383): [<ffff8000083c0b24>] seqcount_lockdep_reader_access include/linux/seqlock.h:104 [inline]
hardirqs last enabled at (272383): [<ffff8000083c0b24>] ktime_get_coarse_real_ts64+0x114/0x244 kernel/time/timekeeping.c:2261
hardirqs last disabled at (272384): [<ffff8000118fa220>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last enabled at (272128): [<ffff8000080309e0>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (272126): [<ffff8000080309ac>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19

---[ end trace 0000000000000000 ]---


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