* [CVE-2026-89998][MODERATE 7.0] dm: fix race when loading and unloading a table
@ 2026-09-16 18:12 21% AL-KERNEL
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From: AL-KERNEL @ 2026-09-16 18:12 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89998
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: dm: fix race when loading and unloading a table
Commit: b02e35b81176c7d61dd441cc7a2e5c324a82444b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b02e35b81176c7d61dd441cc7a2e5c324a82444b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89998
Analysis date: Wed, 16 Sep 2026 14:12:13 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
No one-sentence report phrase was found.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89998 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89998
The original announcement does not normally provide a security severity
estimate, CVSS assessment, or enough information to determine whether the
reported kernel bug represents a practically relevant security issue.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin. It combines
an autonomous classifier with LLM-assisted technical analysis and a
separate ActionableScore mechanism.
The purpose of this report is to prioritize Linux kernel CVEs before
manual review, identify cases that require prompt investigation, and
support automatic closure of issues that are unlikely to have meaningful
security impact.
Published priority for this report: MODERATE 7.0
Manual review required: YES
A detailed explanation of the methodology and priority rules is included
at the end of this message.
======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================
CVE-2026-89998 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89998 CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;CWE-667;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A race in the device mapper table load path can occur when two concurrent table load ioctls run and one succeeds while the other fails. dm_setup_md_queue walked md table_devices without holding table_devices_lock across the full list traversal, while the failing path could destroy the table and release devices through dm_table_destroy, free_devices, and dm_put_table_device. This creates an access to invalid memory and should be treated as a use-after-free candidate rather than a pure logic bug. For the CVSS the PR:L is used for the paranoid score because some deployments may expose device mapper operations through delegated storage management, container root, or reduced-capability service accounts instead of full host administration. The issue is local and not network reachable. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to memory corruption and should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5) YES LOCK DISK SIMPLEFIX RACE HARDWARE LINUS KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 NO NO checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
1. ActionableScore
* Raw conservative score: 3
* Conservative score: 4
* Applied conservative floor/cap: Real UAF floor 4 applied because access to invalid memory is established and host-admin-only reachability is not proven from supplied evidence.
* Raw paranoid score: 5
* Paranoid score: 5
* Applied paranoid floor/cap: none.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
2. Signal breakdown
Positive conservative signals:
* +2 Real UAF / lifetime violation: `dm_setup_md_queue()` walks `md->table_devices` while a concurrent failing table-load path can run `dm_table_destroy -> free_devices -> dm_put_table_device`, making list entries invalid during traversal.
* +1 Reliable kernel crash / strong DoS: the commit explicitly states access to invalid memory, which realistically supports kernel fault or crash.
Positive paranoid signals:
* +2 Real UAF / lifetime violation: same as conservative.
* +1 Reliable kernel crash / strong DoS: same as conservative.
* +1 Structured stale-object exploitation leverage: the stale `table_device` entries are active structured objects, and the walker consumes their list links and `td->dm_dev.bdev` for holder registration rather than merely touching passive metadata.
* +1 Attacker-influenced repeatable lifetime manipulation: the same userspace actor able to issue concurrent table load ioctls can repeatedly drive the success/failure race that frees one table while another path walks shared device state.
Negative signals:
* No host-admin penalty applied because the supplied patch text does not include the device-mapper ioctl authorization path. Device-mapper control is commonly host-admin or CAP_SYS_ADMIN gated, but the complete privilege boundary is not established in the supplied evidence.
* No race penalty applied. This is a race, but both concurrent ioctls are attacker-driven once the interface is reachable, and the evidence does not establish a one-shot or externally uncontrollable timing window.
* No rare subsystem penalty applied. Device mapper is a common storage subsystem.
Non-awarded signals:
* Strong LPE / strong exploitation leverage +2 not awarded. Controlled reclaim, arbitrary write, callback control, refcount takeover, or demonstrated privilege escalation is not established.
* Concrete repeated release/refcount +1 not awarded. The race establishes stale traversal after `dm_put_table_device`, but the supplied control flow does not show the exact same dangling reference receiving a second concrete put/free/refcount mutation.
* Structured leverage is awarded only in the paranoid score because the stale path consumes active fields, but no controlled replacement is demonstrated.
* Extra availability point not awarded because the same invalid-memory crash is already counted once.
* Confidentiality and integrity impact not awarded as standalone signals. They remain unresolved theoretical consequences of the UAF, not demonstrated effects.
* Remote reachability not awarded. The trigger is local device-mapper control, not packet input.
* FLOOR 5 from repeated-release does not apply because no second lifetime/refcount mutation on the exact same reference is established.
3. Reachability analysis
The direct trigger is two concurrent device-mapper table load ioctls where one succeeds far enough to run `dm_setup_md_queue()` and the other fails and destroys table devices. This is a local control-plane operation.
Device-mapper table loading is normally an administrative storage-management operation and commonly requires root or CAP_SYS_ADMIN plus access to `/dev/mapper/control`. However, the supplied patch does not show the authorization checks, and practical deployments may delegate storage management to service accounts or constrained management components. Therefore `HostAdminRequired=UNKNOWN` is used rather than assuming either full host admin or ordinary unprivileged reachability.
No evidence shows that the complete trigger chain is namespace-scoped. The presence of userspace ioctls alone does not prove attacker-obtainable namespace capability, so `NamespaceScopedPrivilege=UNKNOWN`.
No prior special hardware is required beyond use of device mapper. No network path is established. The race appears repeatable by an actor who can issue the relevant ioctls, so no hard timing penalty is applied.
4. Primitive and severity interpretation
The exact primitive is a race-induced stale traversal of `md->table_devices`. One path walks the list in `dm_setup_md_queue()` without holding `table_devices_lock` across the full list walk, while another path can destroy the table and release the corresponding table devices.
This is an active structured-object UAF candidate, not fixed stale storage. The stale object is a `table_device` list element whose fields and list linkage participate in active block-layer holder registration and rollback. The demonstrated consequence is invalid memory access and likely kernel crash or DoS.
This is not a concrete repeated-release/refcount case based on the supplied diff. The first lifetime operation may free table-device state through `dm_put_table_device`, but the visible stale operation is traversal and field consumption, not a second `put` or `free` on the exact same dangling reference.
Primitive class is CLASS_B. The bug is more than a passive logic error, but not CLASS_A because controlled reclaim, directed corruption, arbitrary read/write, security-boundary bypass, or demonstrated LPE is not established.
ImportantCandidate=YES because an active structured UAF in a core storage path has unresolved exploitation leverage beyond a trivial immediate NULL dereference, especially if reachable through delegated storage-management contexts. AutoDowngradeAllowed=NO because automatically closing it as ordinary Moderate would discard a concrete kernel lifetime-corruption primitive that still needs manual Important-vs-Moderate review.
Likely operational severity is Actionable Moderate, with Strong Important review justified if product-specific reachability shows below-host-admin access or if further analysis finds controlled object reuse or a second lifetime mutation.
5. One-sentence report phrase
A race in the device-mapper table load path can let `dm_setup_md_queue()` traverse `md->table_devices` while a concurrent failed load destroys and releases those devices, creating a local active-object UAF candidate that can crash the kernel and requires manual review for possible stronger exploitation.
6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: the patch establishes access to invalid memory from a real race in an active storage object list, and the exact privilege boundary plus post-free exploitation leverage are unresolved.
7. Call-site confidence
Call-site confidence: high
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: dm: fix race when loading and unloading a table
Commit: b02e35b81176c7d61dd441cc7a2e5c324a82444b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b02e35b81176c7d61dd441cc7a2e5c324a82444b
Commit description:
If the userspace calls two concurrent table load ioctls and one of them
succeeds and the other fails, there is a race condition because
dm_setup_md_queue walks &md->table_devices without any lock. If the walk
races with dm_table_destroy -> free_devices -> dm_put_table_device, there
is access to invalid memory.
Fix this race by extending the lock over the list walk.
Signed-off-by: Mikulas Patocka <[email protected]>
Cc: [email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/md/dm.c
Diff excerpt:
Not included in this email. See the upstream URL for the full patch.
Full patch:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b02e35b81176c7d61dd441cc7a2e5c324a82444b
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89998 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89998
The original CVE announcement normally does not include a security-level
estimate. In particular, it may not contain a CVSS assessment, an impact
level, or enough information to determine whether the reported bug is a
practically relevant security issue. One purpose of this parallel CVE list
is to provide that missing technical and prioritization information.
The original goal of the AL-KERNEL project was to prioritize Linux kernel
CVE analysis automatically before manual review. The system can also help
identify non-security issues that may be suitable for automatic closure.
This report was generated by AL-KERNEL, an AI-assisted Linux kernel
vulnerability analysis system developed by Alexander Larkin.
The first analysis stage combines an autonomous classifier with additional
LLM-based analysis. The autonomous classifier runs locally on a CPU and is
based on a backpropagation neural network. Together, these mechanisms
produce a technical vulnerability description, identify likely weakness
types, estimate CVSS severity, and provide input for ActionableScore.
Two CVSS estimates are retained because incomplete kernel vulnerability
information often permits more than one defensible interpretation:
Conservative CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H
The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
The Best / paranoid CVSS score: 7
The conservative vector represents a lower-impact interpretation.
The Best/paranoid vector intentionally represents a plausible upper-bound
interpretation and should not automatically be treated as demonstrated
real-world impact.
CVSS may also need to be adjusted for a particular Linux deployment,
because actual reachability, privileges, enabled kernel configuration,
hardware, namespaces, exposed device nodes, and other environmental
conditions can differ significantly between systems.
A separate ActionableScore mechanism evaluates practical remediation
urgency. Its analysis may include reachability, attack prerequisites,
subsystem exposure, memory-corruption characteristics, denial-of-service
reliability, and possible confidentiality, integrity, or
privilege-escalation impact.
Conservative ActionableScore: 4
Paranoid ActionableScore: 5
The final base severity is taken directly from the second tab-separated
field of the AL-KERNEL classification result. ActionableScore does not
replace or independently override that final AL-KERNEL decision, and
if ActionableScore adjusted impact level of ALKERNEL, then you would see
self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7.
For an AL-KERNEL result of MODERATE, this report uses the following
additional presentation split:
ActionableScore below 5 -> MODERATE REGULAR
ActionableScore 5 or more -> MODERATE 7.0
The distinction between MODERATE REGULAR and MODERATE 7.0 makes it
possible to identify Moderate issues that should receive manual analysis
and fixes before lower-priority MODERATE REGULAR issues. In many cases,
MODERATE REGULAR fixes may wait for a later rebase or routine update.
There is one override in which MODERATE REGULAR becomes MODERATE 7.0
even when the ActionableScore is below 5. When the AL-KERNEL result
contains the KPANIC flag, a MODERATE result is always presented as
MODERATE 7.0. The KPANIC flag selected with few regexps without
usage of AI at all, so it helps to detect cases when Kernel Crash happens
and similar (to filter False-Negative results from the LLM usage).
KPANIC indicates that a reliable kernel crash, kernel panic, or similarly
serious kernel availability impact was identified by the classification
workflow.
AL-KERNEL base severity for this report: MODERATE
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): MODERATE 7.0
These results are intended to support engineering triage. They are
machine-generated estimates, and cases marked for manual review should
be validated by a human security engineer before final disposition.
For more info read docs linked from here: https://kernelcve.org/
(and you can submit you own patch there to generate such a report
for non-existant CVE-id yet).
Note that in many cases this AI tool selects higher severity, than
real is (means you can expect Importants instead of Moderate 7.0 or
Moderates 7.0 instead of regular Moderates). If you see such cases,
please use reply email interface to add additional manual analyses
info to this particular CVE.
And please, please, let me know when you see Lows instead of Importants
or Important instead of Low (because particular for such cases I
need to tune this AI tool to make it better for this one and next similar).
My contact email for such notifications is [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
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