Re: [syzbot] [nilfs?] WARNING in nilfs_rmdir (3)

[syzbot <syzbot+c388db0347b7fc88fa7a@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    67f0943b394d Merge tag 'selinux-pr-20261005' of git://git...
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=11cb9835580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=341a98f91c13ec9
dashboard link: https://syzkaller.appspot.com/bug?extid=c388db0347b7fc88fa7a
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=11d47ec9580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c388db0347b7fc88fa7a@syzkaller.appspotmail.com

NILFS (loop0): broken superblock, retrying with spare superblock (blocksize = 1024)
NILFS (loop0): broken superblock, retrying with spare superblock (blocksize = 4096)
------------[ cut here ]------------
inode->i_nlink == 0
WARNING: fs/inode.c:408 at drop_nlink+0xc5/0x110 fs/inode.c:408, CPU#1: syz-executor166/5936
Modules linked in:
CPU: 1 UID: 0 PID: 5936 Comm: syz-executor166 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
RIP: 0010:drop_nlink+0xc5/0x110 fs/inode.c:408
Code: 50 09 00 00 be 08 00 00 00 e8 e7 45 e9 ff f0 48 ff 83 50 09 00 00 5b 41 5c 41 5e 41 5f 5d c3 cc cc cc cc cc e8 bc 47 7d ff 90 <0f> 0b 90 eb 81 44 89 f1 80 e1 07 80 c1 03 38 c1 0f 8c 5b ff ff ff
RSP: 0018:ffffc9000392fc70 EFLAGS: 00010293
RAX: ffffffff82498df4 RBX: ffff88805e9c9558 RCX: ffff888032d7ddc0
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: ffffed100535792b R12: 1ffff1100bd392b4
R13: ffff88805e9c9558 R14: ffff88805e9c95a0 R15: dffffc0000000000
FS:  000055555fff0400(0000) GS:ffff888125cc2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb871d39286 CR3: 00000000361f2000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 nilfs_rmdir+0x1b4/0x250 fs/nilfs2/namei.c:347
 vfs_rmdir+0x3e9/0x6b0 fs/namei.c:5515
 filename_rmdir+0x292/0x520 fs/namei.c:5572
 __do_sys_rmdir fs/namei.c:5595 [inline]
 __se_sys_rmdir+0x2e/0x140 fs/namei.c:5592
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8f87bafa97
Code: 00 00 90 48 83 ec 10 48 63 ff 45 31 c9 45 31 c0 6a 00 31 c9 e8 4a 07 02 00 48 83 c4 18 c3 0f 1f 44 00 00 b8 54 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 d8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffd6579c7f8 EFLAGS: 00000206 ORIG_RAX: 0000000000000054
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f8f87bafa97
RDX: 0000000000000000 RSI: 00007f8f87c393a3 RDI: 00007f8f87c0cc45
RBP: 00007f8f87c0cbee R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 00007ffd6579c800
R13: 0000000000000000 R14: 00007f8f87c34cc0 R15: 0000000000000002
 </TASK>


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