[CVE-2026-98533][IMPORTANT] ipe: protect the dm-verity root hash with RCU

[AL-KERNEL <alkernel@kernelcve.org>]

CVE: CVE-2026-98533
Priority: IMPORTANT
AL-KERNEL base severity: IMPORTANT
KPANIC flag: YES
Patch: ipe: protect the dm-verity root hash with RCU
Commit: 3bd335ed62444bec61201df7d368a0779e5bd300
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3bd335ed62444bec61201df7d368a0779e5bd300
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98533
Analysis date: Sun, 18 Oct 2026 23:04:08 -0400
ActionableScore: 6
ActionableScore lower bound: 5
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
A concrete RCU lifetime race allows IPE policy evaluation to read a freed dm-verity root hash, creating a kernel-crash risk and an unresolved possibility of an incorrect integrity-policy decision.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-98533 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98533

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: IMPORTANT
Manual review required: YES

A detailed explanation of the methodology and priority rules is included
at the end of this message.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-98533	IMPORTANT	https://www.kernelcve.org/list/?q=CVE-2026-98533 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=0 LEGACY=IMPORTANT RESULT=DIFF INDEPENDENT_LEGACY=IMPORTANT INDEPENDENT_RESULT=DIFF TEMP_KPANIC_MERGE=IMPORTANT_WINS_DISAGREEMENT PRE_MERGE_LEGACY=IMPORTANT (final Legacy and Aegis differ; FINAL: IMPORTANT, Aegis: MODERATE_KPANIC)	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-416;CWE-362;*CWE-672;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:L/A:H';BEST CVSS score: '7';DESCR 'A race in IPE dm verity trust evaluation can cause a use after free because ipe_bdev_setintegrity may free the previous root hash while ipe_digest_eval is still reading it. The concrete primitive is a dereference and comparison of a freed digest_info object under an RCU read side critical section that was not honored by the writer. This can cause a kernel crash or an incorrect IPE policy result. Because the root hash is used to decide whether content satisfies an integrity policy, controlled reuse of the freed object may theoretically affect an authorization decision, although the code does not provide a direct arbitrary write primitive. For the CVSS the PR:L is used for the paranoid score because an ordinary local process can invoke IPE evaluation while root hash replacement may be performed concurrently by a management service or a reduced capability administrative context. AC:H applies because successful triggering depends on a narrow race window and useful reuse of the freed allocation. Impact is at least a local denial of service via kernel crash and in the worst case may allow confidentiality or integrity impact due to memory corruption and should be reviewed manually. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 7 and the production ActionableScore returned 6 with recommendation Actionable Moderate / Strong Important candidate requiring manual review. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage LOW to MODERATE_KPANIC because the ActionableScore threshold rule was applied. ActionableScore thresholds stage MODERATE_KPANIC to IMPORTANT because the ActionableScore threshold rule was applied. The legacy KP specialist produced a review artifact and its decision was processed by the applicable KP rules. The legacy FD or DH downgrade specialist produced a review artifact and its decision was processed by the applicable downgrade and preservation rules. Exact triggered rule markers were INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 and INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 and TEMP_KPANIC_MERGE_IMPORTANT_WINS. The independent weaker Aegis shadow evaluated CVSS 2.0 and ActionableScore 0 with primitive class CLASS_B and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. Cross model aggregation changed the production result under an enabled evidence gated merge rule. The final reported impact is IMPORTANT.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6)	MAYBE	INIT HARDWARE LINUS  KPANIC INCREASED_TO_MODERATE7_FROM_LOW_BASED_ON_GUESSCVSS_AND_ACTIONABLESCOREHIGHER4 KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 TEMP_KPANIC_MERGE_IMPORTANT_WINS	-	-	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=6
ActionableScoreLower=5
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 5
* Raw paranoid score: 5
* Paranoid score: 6
* Applied conservative real UAF and RCU active-state floor: 4 -> 5.
* Applied paranoid active structured RCU calibration: 5 -> 6.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2 Real UAF. The writer frees the old `digest_info` while an RCU reader can still dereference it in `ipe_digest_eval()`.
* +1 Concrete RCU referenced-object lifetime mismatch. `ipe_bdev` remains visible while its referenced `root_hash` is freed before completion of the reader grace period. The fix explicitly adds `rcu_replace_pointer()` and `synchronize_rcu()`.
* +1 Realistic kernel crash. Reading the released digest structure can produce an invalid memory access.
* Raw conservative total: 4. The active structured RCU floor raises this to 5 because host-admin-only reachability is not established.

Additional paranoid signal:

* +1 Weak security-policy leverage. The stale object is actively consumed as a dm-verity trust digest, so corrupted digest fields or bytes can affect an IPE policy comparison rather than merely causing cleanup failure.
* Raw paranoid total: 5. The unresolved active security-state consumption supports the RCU calibration to 6.

Not awarded:

* No controlled reclaim or attacker-shaped replacement object is demonstrated.
* No arbitrary or directed write is demonstrated.
* No confidentiality impact, privilege escalation, or reliable policy bypass is established.
* No concrete DENY-to-ALLOW transition is established, so B4-PENDING does not apply.
* No repeated release or refcount mutation exists. The stale operation is a digest read and comparison.
* No remote reachability or namespace-scoped complete trigger is established.
* No extra Availability point is awarded for the same possible kernel crash.
* V33 is not independently established because attacker-influenced corruption or replacement of the active state is not shown.

3. Reachability analysis

The reader is the IPE policy-evaluation path and may run for ordinary file execution or access operations, but the supplied patch does not show the exact attacker-facing hook or prove that an ordinary user controls the complete trigger.

The writer runs when dm-verity publishes a new root hash during `preresume`. Device-mapper lifecycle operations commonly involve a privileged management component, but the supplied evidence does not establish the exact capability check or prove that the attacker must possess host-admin-equivalent privileges. The evaluated scenario is therefore a compound interaction between policy evaluation and dm-verity state replacement.

No evidence shows that the complete operation is available through an attacker-created user or network namespace. IPE and dm-verity must already be configured, which is a prior deployment prerequisite. No special hardware is required. Exploitation depends on concurrent evaluation during root-hash replacement, but a materially uncontrollable one-shot race is not established, so no race penalty is applied.

4. Primitive and severity interpretation

The exact primitive is a read-side use-after-free of an active `digest_info` object. The old root hash is freed immediately, while a reader that obtained the pointer under `rcu_read_lock()` can continue into `ipe_digest_eval()`.

This is active structured security state, not fixed stale storage and not a cleanup-only dereference. The stale fields and digest bytes participate in an IPE trust decision. There is no second release, refcount operation, or other lifetime mutation through the stale pointer.

The issue is CLASS_B because a concrete RCU lifetime violation exists, but controlled reclaim, arbitrary kernel access, and a confirmed authorization bypass are absent. Demonstrated consequences are potential invalid reads, kernel crash, and unreliable policy evaluation. A useful policy bypass remains an unresolved worst case rather than an established outcome.

ImportantCandidate is YES because an active UAF affects security-policy input and its post-reuse behavior requires manual analysis. AutoDowngradeAllowed is NO because automatically reducing it to crash-only would discard the unresolved security-state consequence. The likely operational severity is Actionable Moderate, with Important-class candidacy requiring source and call-path review.

5. One-sentence report phrase

A concrete RCU lifetime race allows IPE policy evaluation to read a freed dm-verity root hash, creating a kernel-crash risk and an unresolved possibility of an incorrect integrity-policy decision.

6. Manual review recommendation

MANUAL CHECK REQUIRED

The UAF is concrete and occurs while active security-policy state is consumed, but attacker control over replacement memory and a practical DENY-to-ALLOW outcome remain unresolved.

7. Call-site confidence

Call-site confidence: medium

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UPSTREAM PATCH SUMMARY
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Patch: ipe: protect the dm-verity root hash with RCU
Commit: 3bd335ed62444bec61201df7d368a0779e5bd300
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=3bd335ed62444bec61201df7d368a0779e5bd300

Commit description:

ipe_bdev_setintegrity() frees the old root hash when dm-verity publishes
a new one on ->preresume, while policy evaluation can still be
dereferencing it.

Protect the root hash with RCU. The evaluation path already runs under
rcu_read_lock().

Fixes: e155858 ("ipe: add support for dm-verity as a trust provider")
Cc: stable@vger.kernel.org
Assisted-by: LLM
[FW: remove model name according to latest guideline]
Signed-off-by: Fan Wu <wufan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  security/ipe/eval.c
  security/ipe/eval.h
  security/ipe/hooks.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=3bd335ed62444bec61201df7d368a0779e5bd300

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DETAILED REPORT METHODOLOGY
======================================================================

The original Linux kernel CVE announcement for CVE-2026-98533 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98533

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:L/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: 5
  Paranoid ActionableScore: 6

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: IMPORTANT
KPANIC detected for this report: YES
Published priority for this report (same as in Subject): IMPORTANT

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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).