Re: [syzbot] [ntfs3?] INFO: task hung in __start_renaming

On Sun, Nov 23, 2025 at 02:44:29PM -0800, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    fe4d0dea039f Add linux-next specific files for 20251119
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=142c0514580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=f20a6db7594dcad7
> dashboard link: https://syzkaller.appspot.com/bug?extid=2fefb910d2c20c0698d8
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11cd7692580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17615658580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/ce4f26d91a01/disk-fe4d0dea.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/6c9b53acf521/vmlinux-fe4d0dea.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/64d37d01cd64/bzImage-fe4d0dea.xz
> mounted in repro: https://storage.googleapis.com/syzbot-assets/a91529a880b1/mount_0.gz
> 
> The issue was bisected to:
> 
> commit 1e3c3784221ac86401aea72e2bae36057062fc9c
> Author: Mateusz Guzik <[email protected]>
> Date:   Fri Oct 10 22:17:36 2025 +0000
> 
>     fs: rework I_NEW handling to operate without fences
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=17739742580000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=14f39742580000
> console output: https://syzkaller.appspot.com/x/log.txt?x=10f39742580000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
> Fixes: 1e3c3784221a ("fs: rework I_NEW handling to operate without fences")
> 
> INFO: task syz.0.17:6022 blocked for more than 143 seconds.
>       Not tainted syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz.0.17        state:D stack:28744 pid:6022  tgid:6020  ppid:5945   task_flags:0x400040 flags:0x00080002
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5263 [inline]
>  __schedule+0x1836/0x4ed0 kernel/sched/core.c:6871
>  __schedule_loop kernel/sched/core.c:6953 [inline]
>  schedule+0x165/0x360 kernel/sched/core.c:6968
>  schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7025
>  rwsem_down_write_slowpath+0x872/0xfe0 kernel/locking/rwsem.c:1185
>  __down_write_common kernel/locking/rwsem.c:1317 [inline]
>  __down_write kernel/locking/rwsem.c:1326 [inline]
>  down_write_nested+0x1b5/0x200 kernel/locking/rwsem.c:1707
>  inode_lock_nested include/linux/fs.h:1072 [inline]
>  lock_rename fs/namei.c:3681 [inline]
>  __start_renaming+0x148/0x410 fs/namei.c:3777
>  do_renameat2+0x399/0x8e0 fs/namei.c:5991
>  __do_sys_rename fs/namei.c:6059 [inline]
>  __se_sys_rename fs/namei.c:6057 [inline]
>  __x64_sys_rename+0x82/0x90 fs/namei.c:6057
>  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: 0033:0x7f7ba9b8f749
> RSP: 002b:00007f7ba91dd038 EFLAGS: 00000246 ORIG_RAX: 0000000000000052
> RAX: ffffffffffffffda RBX: 00007f7ba9de6090 RCX: 00007f7ba9b8f749
> RDX: 0000000000000000 RSI: 0000200000000080 RDI: 0000200000000340
> RBP: 00007f7ba9c13f91 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007f7ba9de6128 R14: 00007f7ba9de6090 R15: 00007fff2ce8d188
>  </TASK>
> 
> Showing all locks held in the system:
> 1 lock held by khungtaskd/31:
>  #0: ffffffff8df3d740 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
>  #0: ffffffff8df3d740 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
>  #0: ffffffff8df3d740 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
> 2 locks held by getty/5589:
>  #0: ffff88814d56c0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
>  #1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
> 3 locks held by syz.0.17/6021:
> 2 locks held by syz.0.17/6022:
>  #0: ffff888030718420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:509
>  #1: ffff8880631e3dd8 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
>  #1: ffff8880631e3dd8 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3681 [inline]
>  #1: ffff8880631e3dd8 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_renaming+0x148/0x410 fs/namei.c:3777
> 3 locks held by syz.1.18/6048:
> 2 locks held by syz.1.18/6049:
>  #0: ffff888077cbe420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:509
>  #1: ffff8880632db690 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
>  #1: ffff8880632db690 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3681 [inline]
>  #1: ffff8880632db690 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_renaming+0x148/0x410 fs/namei.c:3777
> 3 locks held by syz.2.19/6082:
> 2 locks held by syz.2.19/6083:
>  #0: ffff88807945e420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:509
>  #1: ffff888073281970 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
>  #1: ffff888073281970 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3681 [inline]
>  #1: ffff888073281970 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_renaming+0x148/0x410 fs/namei.c:3777
> 3 locks held by syz.3.20/6107:
> 2 locks held by syz.3.20/6108:
>  #0: ffff88807b0a4420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:509
>  #1: ffff8880631e1228 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
>  #1: ffff8880631e1228 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3681 [inline]
>  #1: ffff8880631e1228 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_renaming+0x148/0x410 fs/namei.c:3777
> 3 locks held by syz.4.21/6138:
> 2 locks held by syz.4.21/6139:
>  #0: ffff8880587fe420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:509
>  #1: ffff8880632d8ae0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
>  #1: ffff8880632d8ae0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3681 [inline]
>  #1: ffff8880632d8ae0 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_renaming+0x148/0x410 fs/namei.c:3777
> 3 locks held by syz.5.22/6176:
> 2 locks held by syz.5.22/6177:
>  #0: ffff888026cec420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:509
>  #1: ffff8880631ce240 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
>  #1: ffff8880631ce240 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3681 [inline]
>  #1: ffff8880631ce240 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_renaming+0x148/0x410 fs/namei.c:3777
> 3 locks held by syz.6.23/6211:
> 2 locks held by syz.6.23/6212:
>  #0: ffff888027d88420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:509
>  #1: ffff8880631c9228 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
>  #1: ffff8880631c9228 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3681 [inline]
>  #1: ffff8880631c9228 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_renaming+0x148/0x410 fs/namei.c:3777
> 3 locks held by syz.7.24/6244:
> 2 locks held by syz.7.24/6245:
>  #0: ffff88807d516420 (sb_writers#12){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:509
>  #1: ffff8880631bdaf8 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1072 [inline]
>  #1: ffff8880631bdaf8 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: lock_rename fs/namei.c:3681 [inline]
>  #1: ffff8880631bdaf8 (&type->i_mutex_dir_key#8/1){+.+.}-{4:4}, at: __start_renaming+0x148/0x410 fs/namei.c:3777
> 
> =============================================
> 
> NMI backtrace for cpu 0
> CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
> Call Trace:
>  <TASK>
>  dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
>  nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
>  nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
>  trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
>  __sys_info lib/sys_info.c:157 [inline]
>  sys_info+0x135/0x170 lib/sys_info.c:165
>  check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
>  watchdog+0xfb5/0x1000 kernel/hung_task.c:515
>  kthread+0x711/0x8a0 kernel/kthread.c:463
>  ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
>  </TASK>
> Sending NMI from CPU 0 to CPUs 1:
> 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>
> 
> 
> ---

#syz test

diff --git a/fs/inode.c b/fs/inode.c
index 0f3a56ea8f48..80298f048117 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1311,12 +1311,11 @@ struct inode *inode_insert5(struct inode *inode, unsigned long hashval,
 		spin_unlock(&inode_hash_lock);
 		if (IS_ERR(old))
 			return NULL;
-		if (unlikely(isnew)) {
+		if (unlikely(isnew))
 			wait_on_new_inode(old);
-			if (unlikely(inode_unhashed(old))) {
-				iput(old);
-				goto again;
-			}
+		if (unlikely(inode_unhashed(old))) {
+			iput(old);
+			goto again;
 		}
 		return old;
 	}
@@ -1413,12 +1412,11 @@ struct inode *iget5_locked_rcu(struct super_block *sb, unsigned long hashval,
 	if (inode) {
 		if (IS_ERR(inode))
 			return NULL;
-		if (unlikely(isnew)) {
+		if (unlikely(isnew))
 			wait_on_new_inode(inode);
-			if (unlikely(inode_unhashed(inode))) {
-				iput(inode);
-				goto again;
-			}
+		if (unlikely(inode_unhashed(inode))) {
+			iput(inode);
+			goto again;
 		}
 		return inode;
 	}
@@ -1459,12 +1457,11 @@ struct inode *iget_locked(struct super_block *sb, unsigned long ino)
 	if (inode) {
 		if (IS_ERR(inode))
 			return NULL;
-		if (unlikely(isnew)) {
+		if (unlikely(isnew))
 			wait_on_new_inode(inode);
-			if (unlikely(inode_unhashed(inode))) {
-				iput(inode);
-				goto again;
-			}
+		if (unlikely(inode_unhashed(inode))) {
+			iput(inode);
+			goto again;
 		}
 		return inode;
 	}
@@ -1501,12 +1498,11 @@ struct inode *iget_locked(struct super_block *sb, unsigned long ino)
 		if (IS_ERR(old))
 			return NULL;
 		inode = old;
-		if (unlikely(isnew)) {
+		if (unlikely(isnew))
 			wait_on_new_inode(inode);
-			if (unlikely(inode_unhashed(inode))) {
-				iput(inode);
-				goto again;
-			}
+		if (unlikely(inode_unhashed(inode))) {
+			iput(inode);
+			goto again;
 		}
 	}
 	return inode;
@@ -1648,12 +1644,11 @@ struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
 again:
 	inode = ilookup5_nowait(sb, hashval, test, data, &isnew);
 	if (inode) {
-		if (unlikely(isnew)) {
+		if (unlikely(isnew))
 			wait_on_new_inode(inode);
-			if (unlikely(inode_unhashed(inode))) {
-				iput(inode);
-				goto again;
-			}
+		if (unlikely(inode_unhashed(inode))) {
+			iput(inode);
+			goto again;
 		}
 	}
 	return inode;
@@ -1682,12 +1677,11 @@ struct inode *ilookup(struct super_block *sb, unsigned long ino)
 	if (inode) {
 		if (IS_ERR(inode))
 			return NULL;
-		if (unlikely(isnew)) {
+		if (unlikely(isnew))
 			wait_on_new_inode(inode);
-			if (unlikely(inode_unhashed(inode))) {
-				iput(inode);
-				goto again;
-			}
+		if (unlikely(inode_unhashed(inode))) {
+			iput(inode);
+			goto again;
 		}
 	}
 	return inode;
@@ -1863,12 +1857,11 @@ int insert_inode_locked(struct inode *inode)
 		isnew = !!(inode_state_read(old) & I_NEW);
 		spin_unlock(&old->i_lock);
 		spin_unlock(&inode_hash_lock);
-		if (isnew) {
+		if (isnew)
 			wait_on_new_inode(old);
-			if (unlikely(!inode_unhashed(old))) {
-				iput(old);
-				return -EBUSY;
-			}
+		if (unlikely(!inode_unhashed(old))) {
+			iput(old);
+			return -EBUSY;
 		}
 		iput(old);
 	}