linux-kernel - Re: [syzbot] [ntfs3?] INFO: task hung in __start

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Message-ID: <CAGudoHG9KjT=srh0H-fwmJDozZSAMiOph+npB938TJboatkWbA@mail.gmail.com>
Date: Mon, 24 Nov 2025 00:29:41 +0100
From: Mateusz Guzik <mjguzik@...il.com>
To: syzbot <syzbot+2fefb910d2c20c0698d8@...kaller.appspotmail.com>
Cc: agruenba@...hat.com, almaz.alexandrovich@...agon-software.com, 
	brauner@...nel.org, dhowells@...hat.com, gfs2@...ts.linux.dev, jack@...e.cz, 
	linux-afs@...ts.infradead.org, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, marc.dionne@...istor.com, ntfs3@...ts.linux.dev, 
	syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: Re: [syzbot] [ntfs3?] INFO: task hung in __start_renaming

On Sun, Nov 23, 2025 at 11:44 PM syzbot
<syzbot+2fefb910d2c20c0698d8@...kaller.appspotmail.com> wrote:
> NMI backtrace for cpu 1
> CPU: 1 UID: 0 PID: 6107 Comm: syz.3.20 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
> RIP: 0010:hlock_class kernel/locking/lockdep.c:234 [inline]
> RIP: 0010:mark_lock+0x3c/0x190 kernel/locking/lockdep.c:4731
> Code: 00 03 00 83 f9 01 bb 09 00 00 00 83 db 00 83 fa 08 0f 45 da bd 01 00 00 00 89 d9 d3 e5 25 ff 1f 00 00 48 0f a3 05 c4 46 df 11 <73> 10 48 69 c0 c8 00 00 00 48 8d 88 70 f3 1e 93 eb 48 83 3d 4b d6
> RSP: 0018:ffffc90003747518 EFLAGS: 00000007
> RAX: 0000000000000311 RBX: 0000000000000008 RCX: 0000000000000008
> RDX: 0000000000000008 RSI: ffff8880275f48a8 RDI: ffff8880275f3d00
> RBP: 0000000000000100 R08: 0000000000000000 R09: ffffffff8241cc56
> R10: dffffc0000000000 R11: ffffed100e650518 R12: 0000000000000004
> R13: 0000000000000003 R14: ffff8880275f48a8 R15: 0000000000000000
> FS:  00007fc3607da6c0(0000) GS:ffff888125fbc000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000558e8c347168 CR3: 0000000077b26000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  mark_usage kernel/locking/lockdep.c:4674 [inline]
>  __lock_acquire+0x6a8/0xd20 kernel/locking/lockdep.c:5191
>  lock_acquire+0x117/0x350 kernel/locking/lockdep.c:5868
>  __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
>  _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
>  spin_lock include/linux/spinlock.h:351 [inline]
>  insert_inode_locked+0x336/0x5d0 fs/inode.c:1837
>  ntfs_new_inode+0xc8/0x100 fs/ntfs3/fsntfs.c:1675
>  ntfs_create_inode+0x606/0x32a0 fs/ntfs3/inode.c:1309
>  ntfs_create+0x3d/0x50 fs/ntfs3/namei.c:110
>  lookup_open fs/namei.c:4409 [inline]
>  open_last_lookups fs/namei.c:4509 [inline]
>  path_openat+0x190f/0x3d90 fs/namei.c:4753
>  do_filp_open+0x1fa/0x410 fs/namei.c:4783
>  do_sys_openat2+0x121/0x1c0 fs/open.c:1432
>  do_sys_open fs/open.c:1447 [inline]
>  __do_sys_openat fs/open.c:1463 [inline]
>  __se_sys_openat fs/open.c:1458 [inline]
>  __x64_sys_openat+0x138/0x170 fs/open.c:1458
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fc35f98f749
> Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fc3607da038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
> RAX: ffffffffffffffda RBX: 00007fc35fbe5fa0 RCX: 00007fc35f98f749
> RDX: 000000000000275a RSI: 00002000000001c0 RDI: ffffffffffffff9c
> RBP: 00007fc35fa13f91 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007fc35fbe6038 R14: 00007fc35fbe5fa0 R15: 00007ffffeb34448
>  </TASK>
>

The bug is in ntfs. It calls d_instantiate instead of
d_instantiate_new and consequently there is no wakeup to begin with.

I'm going to chew on it a little bit, bare mininum d_instantiate
should warn about it and maybe some other fixups are warranted.