* [CVE-2026-89997][MODERATE 7.0] dm: fix resume-vs-remove race
@ 2026-09-16 11:23 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-09-16 11:23 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-89997
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: dm: fix resume-vs-remove race
Commit: 9757367bcf1d5d2c50b94d005abca21f3eedd7c3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9757367bcf1d5d2c50b94d005abca21f3eedd7c3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89997
Analysis date: Wed, 16 Sep 2026 07:23:25 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES
Summary:
A resume-vs-remove race in device mapper can skip target postsuspend handling, leaving dm-integrity reboot notifier state registered after the target is freed and creating a local host-admin-triggered UAF with kernel crash risk and unresolved exploitation leverage.
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ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89997 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89997
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
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CVE-2026-89997 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-89997 CHECK WITH IMPACT FROM ORIG NN MODERATE 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-672;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 device mapper can occur when resume ioctl and remove ioctl are issued at the same time. The mapped device may be resumed after it was suspended in __dm_destroy, so the active table can be destroyed without calling the target postsuspend callback. Some dm targets rely on postsuspend as part of their removal lifetime rules. In dm-integrity this can leave a reboot notifier registered after the target object is freed, creating a use after free condition. For the CVSS the PR:L is used for the higher risk interpretation because device mapper control is normally administrative, but it may be reachable by a delegated local storage service account or a reduced capability root context in some deployments. The issue is not network reachable. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel use after free, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 4) YES DISK INIT RACE UAF HARDWARE LINUS BOOT DECREASED_TO_MODERATEREG_BASED_ON_FALSEPOSCHECKOFKP NO NO checked
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ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=5
ActionableScoreLower=3
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=YES
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
## 1. ActionableScore
* Raw conservative score: 3
* Conservative score: 3
* Raw paranoid score: 4
* Paranoid score: 5
* Applied paranoid floor/cap: manual-review safety floor for active structured UAF with stale notifier registration, 4 -> 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::
## 2. Signal breakdown
Conservative signals:
* +2: Real UAF / lifetime violation. The commit explicitly states that skipping `postsuspend` can leave the `dm-integrity` reboot notifier registered after the target object is freed.
* +1: Reliable kernel crash / strong DoS. A stale reboot notifier callback after object free can realistically lead to kernel fault or crash.
* +1: Secondary registration / notifier staleness. The bug leaves an active notifier-chain registration associated with an object whose target lifetime has ended.
* +1: Active structured stale object. The stale object is not just passive metadata. It remains reachable through a kernel notifier chain and may be consumed later.
* -2: Host-admin-equivalent privilege. Device-mapper resume/remove ioctls are normally controlled through host administrative device-mapper management privileges.
Paranoid additional signal:
* +1: Attacker-influenced repeatable lifetime manipulation. A caller with device-mapper control can attempt concurrent resume/remove operations repeatedly against the affected mapped device lifecycle.
Not awarded:
* Controlled reclaim not demonstrated.
* Arbitrary read/write not demonstrated.
* Confidentiality or integrity impact not awarded as a direct signal.
* Concrete repeated release/refcount mutation not established. This is a stale notifier/UAF case, not a visible second `put` or `release` on the exact same dangling reference.
* Extra availability point not awarded because the crash/DoS is already counted.
* Remote reachability not established.
* Namespace-scoped privilege not established.
Repeated-release/refcount check:
* First release can end lifetime: yes, target/table destruction can free target state.
* Exact same reference survives to second lifetime mutation: not established.
* Second operation is real lifetime/refcount mutation: not established.
* +1 Concrete repeated release/refcount awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 from repeated-release rule applied: no.
## 3. Reachability analysis
The trigger is local control-plane activity through device-mapper ioctls: resume and remove issued concurrently for the same mapped device. This is not packet-driven and not remotely reachable by itself.
The complete trigger normally requires host-level device-mapper administration, effectively host root or equivalent `CAP_SYS_ADMIN` over device-mapper control. Device-mapper block devices are not meaningfully namespace-scoped in the way required to claim `NamespaceScopedPrivilege=YES`.
Prior setup is likely required: an affected mapped device and a target such as `dm-integrity` must exist. This setup is also normally administrative. No special physical hardware is required beyond normal block/device-mapper use.
The race requires concurrent resume-vs-remove timing, but the same privileged actor can repeat attempts. Therefore I did not apply a hard-race penalty.
## 4. Primitive and severity interpretation
The exact primitive is a race-induced lifecycle violation in device mapper. `dm_resume()` could proceed while the mapped device is being destroyed, allowing the table to be destroyed without the target `postsuspend` callback. For `dm-integrity`, this can leave a reboot notifier registered after the target object is freed, creating a real UAF.
This is an active structured-object UAF rather than fixed stale storage. The stale state remains registered in a notifier chain and can be consumed later by kernel notifier traversal. It is stronger than a simple immediate NULL dereference, but the supplied patch does not establish controlled reclaim, arbitrary kernel read/write, callback hijack, or demonstrated local privilege escalation.
Primitive class is `CLASS_B`: a real kernel lifetime/UAF primitive exists and exploitation-leverage analysis is required. It is not `CLASS_A` because no controlled replacement, directed corruption, arbitrary write, or demonstrated LPE is supplied.
`ImportantCandidate=YES` because a stale active notifier registration after free is meaningful unresolved kernel lifetime corruption, even though the normal trigger is host-admin-gated. `AutoDowngradeAllowed=NO` because automatically treating this as ordinary crash-only cleanup would discard the unresolved UAF/notifier-chain primitive.
Likely operational severity is Actionable Moderate. It may become an Important-class issue only if additional evidence shows below-host-admin reachability, controlled reclaim/reuse, or a practical privilege-escalation chain.
## 5. One-sentence report phrase
A resume-vs-remove race in device mapper can skip target postsuspend handling, leaving dm-integrity reboot notifier state registered after the target is freed and creating a local host-admin-triggered UAF with kernel crash risk and unresolved exploitation leverage.
## 6. Manual review recommendation
MANUAL CHECK REQUIRED
Reason: the patch establishes a real UAF involving an active notifier-chain registration. Even though normal reachability appears host-admin-gated, the stale callback registration makes this unsafe to automatically downgrade without checking target-specific lifetime behavior and possible delegated storage-management exposure.
## 7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: dm: fix resume-vs-remove race
Commit: 9757367bcf1d5d2c50b94d005abca21f3eedd7c3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9757367bcf1d5d2c50b94d005abca21f3eedd7c3
Commit description:
If the user issues the resume ioctl and the remove ioctl at the same
time, it may be possible that the device is resumed after it is suspended
in __dm_destroy. The result is that the table is destroyed without
calling the postsuspend method.
Dm targets expect that they may be removed only after the postsuspend
method method was called. If we break this expectation, it can cause
misbehavior in various targets. For example - in the dm-integrity target,
the reboot notifier is not unregistered, leading to use-after-free.
Fix this bug by refusing to resume if the device is being destroyed.
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=9757367bcf1d5d2c50b94d005abca21f3eedd7c3
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-89997 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89997
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: 3
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: NO
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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