CVE-2026-98539 - Vulnerability Details

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

Description

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.

Published: 2026-10-18

Score: n/a

EPSS: n/a

KEV: No

Impact:

Action:

Analysis

Impact

The vulnerability resides in the Linux kernel’s NTFS‑3 file system driver. During the creation of a new directory on a freshly mounted NTFS image, a race condition between the directory creation path and a concurrent mount operation can corrupt an inode’s read‑write lock. The lock’s count is under‑decremented during an unsafe unlock sequence, causing a warning and preventing subsequent inode locks. This corruption can result in deadlocks and potentially corrupt path resolution, leading to a loss of file system integrity and service availability.

Affected Systems

All Linux kernel builds that include the NTFS‑3 driver are potentially affected. No specific version range is provided; the issue is fixed in the latest kernel releases that replace the legacy d_instantiate() call with d_instantiate_new() and remove unnecessary unlock calls.

Risk and Exploitability

The bug can only be triggered in a local context where a user can perform both a directory creation and a mount operation on the same NTFS volume. Typical mitigation requires privileged mount access (CAP_SYS_ADMIN or root). No publicly known exploits or exploits in the wild are documented, and the EPSS score is currently not available. The risk level remains moderate to high for systems that expose untrusted NTFS content to privileged users. The Kernel Integrity Vulnerability (KEV) list does not currently include this issue, and the vendor's fix provides complete remediation.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`82cae269cfa953032fbb8980a7d554d60fb00b17`	affected	< 6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e
`82cae269cfa953032fbb8980a7d554d60fb00b17`	affected	< 37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f
`82cae269cfa953032fbb8980a7d554d60fb00b17`	affected	< 1ae2a242c15b03470b1b16289298e597bbe3bb29
`82cae269cfa953032fbb8980a7d554d60fb00b17`	affected	< 1abd643f3783ea8f8e273c18697ff0413aa92dc7

Linux

affected

Version	Status	Constraints
`5.15`	affected	—
`0`	unaffected	< 5.15
`6.12.112`	unaffected	≤ 6.12.*
`6.18.55`	unaffected	≤ 6.18.*
`7.2.9`	unaffected	≤ 7.2.*
`7.3-rc5`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[82cae269cfa953032fbb8980a7d554d60fb00b17,6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e)`	affected	code_commit	—
`[82cae269cfa953032fbb8980a7d554d60fb00b17,37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f)`	affected	code_commit	—
`[82cae269cfa953032fbb8980a7d554d60fb00b17,1ae2a242c15b03470b1b16289298e597bbe3bb29)`	affected	code_commit	—
`[82cae269cfa953032fbb8980a7d554d60fb00b17,1abd643f3783ea8f8e273c18697ff0413aa92dc7)`	affected	code_commit	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`5.15`	affected	generic	—
`[0,5.15)`	unaffected	generic	—
`[6.12.112,6.13.0)`	unaffected	semver	—
`[6.18.55,6.19.0)`	unaffected	semver	—
`[7.2.9,7.3.0)`	unaffected	semver	—
`[7.3-rc5,*]`	unaffected	generic	—

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Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Upgrade to the latest Linux kernel that includes the ntfs3 driver fix which replaces d_instantiate() with d_instantiate_new() and removes the unsafe unlock sequence.
Reboot the system to ensure the patched kernel is active and unloaded any old ntfs3 modules.
If the environment relies on legacy ntfs3 modules or custom mounts, use mount options to restrict concurrent directory creation and mount operations, or disable the ntfs3 driver until the patch is applied.

Generated by OpenCVE AI on October 19, 2026 at 00:00 UTC.

Tracking

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Advisories

No advisories yet.

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/1abd643f3783ea8f8e273c18697ff0413aa92dc7
https://git.kernel.org/stable/c/1ae2a242c15b03470b1b16289298e597bbe3bb29
https://git.kernel.org/stable/c/37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f
https://git.kernel.org/stable/c/6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e

History

Mon, 19 Oct 2026 00:30:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-665

Sun, 18 Oct 2026 15:30:00 +0000

Type	Values Removed	Values Added
Description		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.
Title		fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot's "WARNING in do_new_mount" saga
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/1abd643f3783ea8f8e273c18697ff0413aa92dc7 https://git.kernel.org/stable/c/1ae2a242c15b03470b1b16289298e597bbe3bb29 https://git.kernel.org/stable/c/37ec7353f4ac495b28284b0fcb0e53d21d1b3f3f https://git.kernel.org/stable/c/6fda7121cb6a8ea6fbd77d0f787f04b8e8b5358e

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-10-18T15:18:06.921Z

Updated: 2026-10-18T15:18:06.921Z

Reserved: 2026-09-25T10:25:14.356Z

Link: CVE-2026-98539

Vulnrichment

No data.

NVD

Status : Received

Published: 2026-10-18T16:17:05.733

Modified: 2026-10-18T16:17:05.733

Link: CVE-2026-98539

Redhat

No data.

OpenCVE Enrichment

Updated: 2026-10-19T03:15:14Z

Weaknesses

CWE-665
Improper Initialization

Impact

Affected Systems

Risk and Exploitability

Tracking

Subscriptions

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