CVE-2026-89484
Received Received - Intake

Null Pointer Dereference in Linux Kernel NLM Locking

Publication date: 2026-09-11

Last updated on: 2026-09-11

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: lockd: fix NULL dereference on lockowner allocation failure nlmclnt_locks_init_private() installs NLM file lock operations even when nlmclnt_find_lockowner() fails to allocate a lockowner. nlmclnt_proc() then returns -ENOMEM, but the VFS still tears down the partially initialized file_lock and calls locks_release_private(). That invokes nlmclnt_locks_release_private(), which dereferences fl->fl_u.nfs_fl.owner and crashes because the owner was never installed. Clear fl_ops before attempting to initialize the NLM private state, and install the NLM lock operations only after a lockowner has been allocated successfully.

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Meta Information

Published
2026-09-11
Last Modified
2026-09-11
Generated
2026-09-12
AI Q&A
2026-09-11
EPSS Evaluated
N/A
NVD
CVE-2026-89484
EUVD
EUVD-2026-76390

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a NULL pointer dereference in the lockd component. When allocating a lockowner fails, the system still attempts to use partially initialized file locks, leading to a crash when accessing uninitialized memory.

Detection Guidance

This vulnerability is specific to the Linux kernel's lockd subsystem and may not have direct detection commands. Monitor kernel logs for crashes related to lockd or NLM operations, particularly after file lock operations. Check for kernel oops or panic messages involving nlmclnt_locks_release_private or fl_u.nfs_fl.owner dereferencing.

Impact Analysis

This could cause system crashes or instability when file locking operations are attempted, potentially leading to denial of service or data corruption if the kernel panics.

Mitigation Strategies

Apply the latest Linux kernel patches that address this issue. If immediate patching is not possible, consider disabling the NLM (Network Lock Manager) service if it is not required. Monitor system stability and kernel logs for signs of exploitation or crashes.

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