CVE-2026-74348 - Vulnerability Details

- ocfs2/dlm: require a ref for locking_state debugfs open

Description

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

ocfs2/dlm: require a ref for locking_state debugfs open

debug_lockres_open() copies inode->i_private into struct debug_lockres and
debug_lockres_release() later drops that pointer with dlm_put(). That
only works if open successfully pins the struct dlm_ctxt.

Today open calls dlm_grab(dlm) but ignores its return value. Once the
last domain unregister has removed the context from dlm_domains,
dlm_grab() returns NULL, yet open still stores the raw pointer and returns
success. The later release path is outside the debugfs removal barrier,
so it can call dlm_put() after dlm_free_ctxt_mem() has freed the context.
KASAN reports this as a slab-use-after-free in dlm_put() called from
debug_lockres_release().

Fail the open when dlm_grab() cannot acquire the reference and unwind the
seq_file private state before returning. That keeps locking_state from
handing out a file descriptor whose release path does not own the
dlm_ctxt.

The buggy scenario involves two paths, with each column showing the order
within that path:

locking_state debugfs open: last domain unregister:
1. debug_lockres_open() reads 1. dlm_unregister_domain() calls
inode->i_private. dlm_complete_dlm_shutdown().
2. debug_lockres_open() calls 2. shutdown removes the dlm_ctxt from
dlm_grab(dlm) and gets NULL. dlm_domains.
3. open still stores the raw dlm 3. final teardown reaches
pointer in dl->dl_ctxt and dlm_free_ctxt_mem() and frees it.
returns success.
4. debug_lockres_release() later
calls dlm_put(dl->dl_ctxt).

Validation reproduced this kernel report:
KASAN slab-use-after-free in dlm_put+0x82/0x200
RIP: 0033:0x7f4d349bc9e0
The buggy address belongs to the object at ffff888103a3c000 which belongs
to the cache kmalloc-2k of size 2048
The buggy address is located 816 bytes inside of freed 2048-byte region
[ffff888103a3c000, ffff888103a3c800)
Write of size 4
Call trace:
dump_stack_lvl+0x66/0xa0 (?:?)
print_report+0xd0/0x630 (?:?)
dlm_put+0x82/0x200 (?:?)
srso_alias_return_thunk+0x5/0xfbef5 (?:?)
__virt_addr_valid+0x188/0x2f0 (?:?)
kasan_report+0xe4/0x120 (?:?)
kasan_check_range+0x105/0x1b0 (?:?)
debug_lockres_release+0x53/0x80 (fs/ocfs2/dlm/dlmdebug.c:587)
dlm_put+0x9/0x200 (?:?)
debug_lockres_release+0x5c/0x80 (fs/ocfs2/dlm/dlmdebug.c:587)
full_proxy_release+0x67/0x90 (?:?)
__fput+0x1df/0x4b0 (?:?)
do_raw_spin_lock+0x10f/0x1b0 (?:?)
fput_close_sync+0xd2/0x170 (?:?)
__x64_sys_close+0x55/0x90 (?:?)
do_syscall_64+0x10c/0x640 (arch/x86/entry/syscall_64.c:87)
irqentry_exit+0xac/0x6e0 (?:?)
entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)
Freed by task stack:
kasan_save_stack+0x33/0x60 (?:?)
kasan_save_track+0x14/0x30 (?:?)
kasan_save_free_info+0x3b/0x60 (?:?)
__kasan_slab_free+0x5f/0x80 (?:?)
kfree+0x30f/0x580 (?:?)
dlm_put+0x1ce/0x200 (?:?)
dlm_unregister_domain+0xf6/0xb30 (?:?)
o2cb_cluster_disconnect+0x6b/0x90 (?:?)
ocfs2_cluster_disconnect+0x41/0x70 (?:?)
ocfs2_dlm_shutdown+0x1c4/0x220 (?:?)
ocfs2_dismount_volume+0x38a/0x550 (?:?)
generic_shutdown_super+0xc3/0x220 (?:?)
kill_block_super+0x29/0x60 (?:?)
deactivate_locked_super+0x66/0xe0 (?:?)
cleanup_mnt+0x13d/0x210 (?:?)
task_work_run+0xfa/0x170 (?:?)
exit_to_user_mode_loop+0xd6/0x430 (?:?)
do_syscall_64+0x3cb/0x640 (arch/x86/entry/syscall_64.c:87)
entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)

Published: 2026-08-15

Score: 5.5 Medium

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

In the Linux kernel, an improper reference count handling in the OCFS2 Distributed Lock Manager (DLM) debugfs interface allows a use‑after‑free condition when a debugfs file is opened after the corresponding DLM domain has been unregistered. The flaw arises because the open path ignores the failure of dlm_grab(), storing a dangling pointer that later triggers a KASAN slab‑use‑after‑free when the file is closed. This kernel memory corruption can lead to arbitrary code execution or system instability, corresponding to CWE‑416.

Affected Systems

Affected systems are any Linux kernel installations that provide the OCFS2 filesystem with the DLM component compiled in. The issue is present in all kernel releases before the patch that enforces a reference check during debugfs open; no specific upstream version range is listed, so all kernels prior to the resolution should be considered vulnerable.

Risk and Exploitability

With a CVSS score of 5.5, the flaw presents a moderate risk. The EPSS score of < 1% and its absence from the KEV catalog suggest it is not yet widely exploited. The flaw requires privilege to open the ocfs2/dlm debugfs entry and a concurrent domain shutdown to create the dangling reference, implying a local or privileged attacker could trigger the use‑after‑free. If successfully triggered, the memory corruption could allow arbitrary kernel code execution, presenting a moderate risk to affected systems.

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
`4e3d24ed1a1285fe3289653aacc965642706bacb`	affected	< 6cc93dea4078cbcddee63fa2234e382a76600464
`4e3d24ed1a1285fe3289653aacc965642706bacb`	affected	< 90a6512425414098a63fc97b77bed089c75d106b
`4e3d24ed1a1285fe3289653aacc965642706bacb`	affected	< 5bee5d5f67aedd26d2b72e00e49dd93331fbcc30
`4e3d24ed1a1285fe3289653aacc965642706bacb`	affected	< aa7883b6a3c76301a3299deb34de948e73bb6a08
`4e3d24ed1a1285fe3289653aacc965642706bacb`	affected	< 9c81c1a61a52b6ecf0d14f1dbd95f154a7a9e92a
`4e3d24ed1a1285fe3289653aacc965642706bacb`	affected	< a087b2d3411e7f9df71ba3293596923ee2c70d65
`4e3d24ed1a1285fe3289653aacc965642706bacb`	affected	< a09831214912a1f270663d935613910fafd8d883
`4e3d24ed1a1285fe3289653aacc965642706bacb`	affected	< 03ad858ce8064861ea580021976dc19b7aabb549

Linux

affected

Version	Status	Constraints
`2.6.26`	affected	—
`0`	unaffected	< 2.6.26
`5.10.261`	unaffected	≤ 5.10.*
`5.15.212`	unaffected	≤ 5.15.*
`6.1.178`	unaffected	≤ 6.1.*
`6.6.145`	unaffected	≤ 6.6.*
`6.12.97`	unaffected	≤ 6.12.*
`6.18.40`	unaffected	≤ 6.18.*
`7.1.5`	unaffected	≤ 7.1.*
`7.2`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[4e3d24ed1a1285fe3289653aacc965642706bacb,6cc93dea4078cbcddee63fa2234e382a76600464)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,90a6512425414098a63fc97b77bed089c75d106b)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,5bee5d5f67aedd26d2b72e00e49dd93331fbcc30)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,aa7883b6a3c76301a3299deb34de948e73bb6a08)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,9c81c1a61a52b6ecf0d14f1dbd95f154a7a9e92a)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,a087b2d3411e7f9df71ba3293596923ee2c70d65)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,a09831214912a1f270663d935613910fafd8d883)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,03ad858ce8064861ea580021976dc19b7aabb549)`	affected	code_commit	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[4e3d24ed1a1285fe3289653aacc965642706bacb,6cc93dea4078cbcddee63fa2234e382a76600464)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,90a6512425414098a63fc97b77bed089c75d106b)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,5bee5d5f67aedd26d2b72e00e49dd93331fbcc30)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,aa7883b6a3c76301a3299deb34de948e73bb6a08)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,9c81c1a61a52b6ecf0d14f1dbd95f154a7a9e92a)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,a087b2d3411e7f9df71ba3293596923ee2c70d65)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,a09831214912a1f270663d935613910fafd8d883)`	affected	code_commit	—
`[4e3d24ed1a1285fe3289653aacc965642706bacb,03ad858ce8064861ea580021976dc19b7aabb549)`	affected	code_commit	—
`2.6.26`	affected	semver	—
`[0,2.6.26)`	unaffected	semver	—
`[5.10.261,5.11.0]`	unaffected	semver	—
`[5.15.212,5.16.0]`	unaffected	semver	—
`[6.1.178,6.2.0]`	unaffected	semver	—
`[6.6.145,6.7.0]`	unaffected	semver	—
`[6.12.97,6.13.0]`	unaffected	semver	—
`[6.18.40,6.19.0]`	unaffected	semver	—
`[7.1.5,7.2.0]`	unaffected	semver	—
`[7.2-rc1,*]`	unaffected	generic	—

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Remediation

No vendor fix or workaround currently provided.

OpenCVE Recommended Actions

Apply the latest kernel patch that corrects the DLM debugfs open path to reject failures from dlm_grab().
If immediate kernel upgrade is not possible, revoke access to the ocfs2/dlm debugfs interface by tightening directory permissions so only root can read/write.
Disable the OCFS2 DLM debugging interface entirely if it is not required, for example by editing /proc/sys/kernel/debugfs_permissions or by compiling the kernel without OCFS2 debugging support.
Ensure that all OCFS2 volumes are cleanly unmounted before shutting down the kernel or removing storage devices to avoid accidental domain unregistration while debugging.

Generated by OpenCVE AI on August 21, 2026 at 23:57 UTC.

Tracking

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Advisories

No advisories yet.

No CVSS v4.0

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00177.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/03ad858ce8064861ea580021976dc19b7aabb549
https://git.kernel.org/stable/c/5bee5d5f67aedd26d2b72e00e49dd93331fbcc30
https://git.kernel.org/stable/c/6cc93dea4078cbcddee63fa2234e382a76600464
https://git.kernel.org/stable/c/90a6512425414098a63fc97b77bed089c75d106b
https://git.kernel.org/stable/c/9c81c1a61a52b6ecf0d14f1dbd95f154a7a9e92a
https://git.kernel.org/stable/c/a087b2d3411e7f9df71ba3293596923ee2c70d65
https://git.kernel.org/stable/c/a09831214912a1f270663d935613910fafd8d883
https://git.kernel.org/stable/c/aa7883b6a3c76301a3299deb34de948e73bb6a08
https://lore.kernel.org/linux-cve-announce/2026081559-CVE-2026-74348-3c99@gregkh/T
https://nvd.nist.gov/vuln/detail/CVE-2026-74348
https://www.cve.org/CVERecord?id=CVE-2026-74348

History

Fri, 21 Aug 2026 00:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-825
References		https://lore.kernel.org/linux-cve-announce/2026081559-CVE-2026-74348-3c99@gregkh/T https://nvd.nist.gov/vuln/detail/CVE-2026-74348 https://www.cve.org/CVERecord?id=CVE-2026-74348
Metrics	threat_severity `None`	cvssV3_1 `{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}` threat_severity `Moderate`

Sat, 15 Aug 2026 16:45:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-416

Sat, 15 Aug 2026 06:15:00 +0000

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: ocfs2/dlm: require a ref for locking_state debugfs open debug_lockres_open() copies inode->i_private into struct debug_lockres and debug_lockres_release() later drops that pointer with dlm_put(). That only works if open successfully pins the struct dlm_ctxt. Today open calls dlm_grab(dlm) but ignores its return value. Once the last domain unregister has removed the context from dlm_domains, dlm_grab() returns NULL, yet open still stores the raw pointer and returns success. The later release path is outside the debugfs removal barrier, so it can call dlm_put() after dlm_free_ctxt_mem() has freed the context. KASAN reports this as a slab-use-after-free in dlm_put() called from debug_lockres_release(). Fail the open when dlm_grab() cannot acquire the reference and unwind the seq_file private state before returning. That keeps locking_state from handing out a file descriptor whose release path does not own the dlm_ctxt. The buggy scenario involves two paths, with each column showing the order within that path: locking_state debugfs open: last domain unregister: 1. debug_lockres_open() reads 1. dlm_unregister_domain() calls inode->i_private. dlm_complete_dlm_shutdown(). 2. debug_lockres_open() calls 2. shutdown removes the dlm_ctxt from dlm_grab(dlm) and gets NULL. dlm_domains. 3. open still stores the raw dlm 3. final teardown reaches pointer in dl->dl_ctxt and dlm_free_ctxt_mem() and frees it. returns success. 4. debug_lockres_release() later calls dlm_put(dl->dl_ctxt). Validation reproduced this kernel report: KASAN slab-use-after-free in dlm_put+0x82/0x200 RIP: 0033:0x7f4d349bc9e0 The buggy address belongs to the object at ffff888103a3c000 which belongs to the cache kmalloc-2k of size 2048 The buggy address is located 816 bytes inside of freed 2048-byte region [ffff888103a3c000, ffff888103a3c800) Write of size 4 Call trace: dump_stack_lvl+0x66/0xa0 (?:?) print_report+0xd0/0x630 (?:?) dlm_put+0x82/0x200 (?:?) srso_alias_return_thunk+0x5/0xfbef5 (?:?) __virt_addr_valid+0x188/0x2f0 (?:?) kasan_report+0xe4/0x120 (?:?) kasan_check_range+0x105/0x1b0 (?:?) debug_lockres_release+0x53/0x80 (fs/ocfs2/dlm/dlmdebug.c:587) dlm_put+0x9/0x200 (?:?) debug_lockres_release+0x5c/0x80 (fs/ocfs2/dlm/dlmdebug.c:587) full_proxy_release+0x67/0x90 (?:?) __fput+0x1df/0x4b0 (?:?) do_raw_spin_lock+0x10f/0x1b0 (?:?) fput_close_sync+0xd2/0x170 (?:?) __x64_sys_close+0x55/0x90 (?:?) do_syscall_64+0x10c/0x640 (arch/x86/entry/syscall_64.c:87) irqentry_exit+0xac/0x6e0 (?:?) entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?) Freed by task stack: kasan_save_stack+0x33/0x60 (?:?) kasan_save_track+0x14/0x30 (?:?) kasan_save_free_info+0x3b/0x60 (?:?) __kasan_slab_free+0x5f/0x80 (?:?) kfree+0x30f/0x580 (?:?) dlm_put+0x1ce/0x200 (?:?) dlm_unregister_domain+0xf6/0xb30 (?:?) o2cb_cluster_disconnect+0x6b/0x90 (?:?) ocfs2_cluster_disconnect+0x41/0x70 (?:?) ocfs2_dlm_shutdown+0x1c4/0x220 (?:?) ocfs2_dismount_volume+0x38a/0x550 (?:?) generic_shutdown_super+0xc3/0x220 (?:?) kill_block_super+0x29/0x60 (?:?) deactivate_locked_super+0x66/0xe0 (?:?) cleanup_mnt+0x13d/0x210 (?:?) task_work_run+0xfa/0x170 (?:?) exit_to_user_mode_loop+0xd6/0x430 (?:?) do_syscall_64+0x3cb/0x640 (arch/x86/entry/syscall_64.c:87) entry_SYSCALL_64_after_hwframe+0x77/0x7f (?:?)
Title		ocfs2/dlm: require a ref for locking_state debugfs open
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/03ad858ce8064861ea580021976dc19b7aabb549 https://git.kernel.org/stable/c/5bee5d5f67aedd26d2b72e00e49dd93331fbcc30 https://git.kernel.org/stable/c/6cc93dea4078cbcddee63fa2234e382a76600464 https://git.kernel.org/stable/c/90a6512425414098a63fc97b77bed089c75d106b https://git.kernel.org/stable/c/9c81c1a61a52b6ecf0d14f1dbd95f154a7a9e92a https://git.kernel.org/stable/c/a087b2d3411e7f9df71ba3293596923ee2c70d65 https://git.kernel.org/stable/c/a09831214912a1f270663d935613910fafd8d883 https://git.kernel.org/stable/c/aa7883b6a3c76301a3299deb34de948e73bb6a08

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-08-15T05:58:35.977Z

Updated: 2026-08-17T05:17:41.148Z

Reserved: 2026-08-15T05:44:03.886Z

Link: CVE-2026-74348

Vulnrichment

No data.

NVD

Status : Received

Published: 2026-08-15T06:22:35.970

Modified: 2026-08-17T06:19:29.400

Link: CVE-2026-74348

Redhat

Severity : Moderate

Publid Date: 2026-08-15T00:00:00Z

Links: CVE-2026-74348 - Bugzilla

OpenCVE Enrichment

Updated: 2026-08-22T00:00:16Z

Weaknesses

CWE-416
Use After Free
CWE-825
Expired Pointer Dereference

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Local

Attack Complexity Low

Privileges Required Low

Scope Unchanged

Confidentiality Impact None

Integrity Impact None

Availability Impact High

User Interaction None

Subscriptions

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