---
id: "CVE-2026-98539"
kind: "vulnerability"
aliases: ["CVE-2026-98539"]
title: "Linux kernel ntfs3: directory lock race lets mount hang or crash the kernel"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["linux-kernel", "linux-servers", "ntfs3", "runtime", "self-hosted"]
not_affected_if: ["default-config", "ntfs3-not-used"]
published_at: "2026-10-18T16:17:05+00:00"
first_seen_at: "2026-10-23T21:57:15+00:00"
updated_at: "2026-10-25T05:23:44+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98539", "first_seen_at": "2026-10-23T21:57:15+00:00"}]
---

# Linux kernel ntfs3: directory lock race lets mount hang or crash the kernel

In the ntfs3 filesystem driver, a new directory is made visible to other processes before its inode lock is set up, so a concurrent mount or path lookup can corrupt that lock. The result is a kernel warning on mount and a later hang when the directory's lock is taken.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- `uname -r` and compare against the kernel version that carries the fix
- `lsmod | grep ntfs3` to see whether the ntfs3 driver is loaded
- Check whether ntfs3 mounts are used: `mount -t ntfs3`

## Fix

- Update the Linux kernel to a release that includes the commit 'fs/ntfs3: use d_instantiate_new() in ntfs_create_inode()'
- Until updated, avoid mounting untrusted NTFS images with ntfs3 (unknown fixed version numbers in sources)

## Timeline

- 2026-10-23T21:57:15+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-98539

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot's "WARNING in do_new_mount" saga

ntfs_create_inode() creates a new inode via ntfs_new_inode(). It hashes
it with insert_inode_locked() and so it's marked as I_NEW until
unlock_new_inode().

ntfs 3 calls d_instantiate() in between though... Since the dentry was
already hashed by the lookup before the create any path walk finds it
without touching the parent's i_rwsem and so can lock the inode.

If the inode is a directory unlock_new_inode() calls
lockdep_annotate_inode_mutex_key() and marks i_rwsem with the
i_mutex_dir_key class.

That resets the count and the owner of a lock somebody else may already
hold by now...

syzbot has been spamming us with the same godforsaken bug

  "WARNING in do_new_mount"

since 2023. I can't take it anymore so I went looking. Afaict, syzbot's
executor chdirs into a freshly mounted ntfs3 image, creates a
directory and then mounts some pseudofs on it. Everytime the mkdir()
takes longer than syzbot waits mount() runs concurrently:

  mkdir("./sys")                        mount(NULL, "./sys", "sysfs")
  ntfs_create_inode()
    d_instantiate()
                                        user_path_at() finds the dentry
                                        do_lock_mount()
                                          inode_lock(inode)
                                          namespace_lock()
    unlock_new_inode()
      lockdep_annotate_inode_mutex_key()
        init_rwsem(&inode->i_rwsem)
                                        unlock_mount()
                                          inode_unlock(inode)

The mount side then releases a lock that according to the rwsem nobody
holds:

  DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) && ...):
  count = 0x0, magic = 0xffff888043a854e8, owner = 0x0,
  curr 0xffff888000244880, list empty
  WARNING: CPU: 0 PID: 5346 at kernel/locking/rwsem.c:1368 __up_write
  Call Trace:
   inode_unlock include/linux/fs.h:877 [inline]
   unlock_mount fs/namespace.c:2892 [inline]
   do_new_mount_fc fs/namespace.c:3828 [inline]
   do_new_mount+0x777/0xa40 fs/namespace.c:3887

On PREEMPT_RT the same thing shows up as

  DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current)
  WARNING: kernel/locking/rtmutex_common.h:193 at rt_mutex_slowunlock

The up_write() underflows the reset count. A following inode_lock() on
that directory then never returns. A path walk into the new directory
racing with the mkdir() corrupts the lock the same way via
inode_lock_shared() in lookup_slow().

Switch to d_instantiate_new() and drop the trailing unlock_new_inode().
All error paths bail out before that point with I_NEW still set and
keep using discard_new_inode().

May we never see this fscking bug report again.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_