[CVE-2026-89800][LOW] drm/nouveau/uvmm: clear the dirty flag when unwinding an OP_UNMAP_SPARSE

[CVE-2026-89800][LOW] drm/nouveau/uvmm: clear the dirty flag when unwinding an OP_UNMAP_SPARSE

[AL-KERNEL]

CVE: CVE-2026-89800
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/nouveau/uvmm: clear the dirty flag when unwinding an OP_UNMAP_SPARSE
Commit: a129b2b875c148aba233ace8447a0c36ca3bae07
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a129b2b875c148aba233ace8447a0c36ca3bae07
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89800
Analysis date: Wed, 16 Sep 2026 10:14:52 -0400
ActionableScore: 2
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
No one-sentence report phrase was found.

======================================================================
ABOUT THIS REPORT
======================================================================

The original Linux kernel CVE announcement for CVE-2026-89800 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89800

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: LOW
Manual review required: NO

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

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-89800	LOW	https://www.kernelcve.org/list/?q=CVE-2026-89800 CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-459;CWE-703;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'A stale dirty state in the nouveau VM_BIND unwind path can leave a sparse unmap region permanently dirty after a later operation in the same job fails. Later binds over the affected range can then fail with ENOENT or EINVAL, or block in wait_for_completion for the lifetime of the uvmm. For the CVSS the PR:L is used because triggering requires local access to the nouveau DRM VM_BIND interface, commonly through render node or GPU device permissions, but not full administrator privileges. The issue is not network reachable and is triggered through local GPU control plane operations. Impact is denial of service against the affected GPU VM context or process state, with no clear memory corruption primitive or privilege escalation path supported by the patch context.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2)	YES	SIMPLEFIX HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	YES	NO	checked

======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================

ActionableScore=2
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES

1. ActionableScore

* Raw conservative score: 2
* Conservative score: 2. No floor or cap applied.
* Raw paranoid score: 2
* Paranoid score: 2. No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

Positive signals:

* +1 Local below-host-admin trigger. The issue is reachable through the nouveau DRM VM_BIND userspace interface, normally available to a local process with GPU render node or device access rather than full host administrator privileges.
* +1 Persistent local availability impact. The stale dirty flag can make later binds fail permanently for the lifetime of the uvmm or cause an unkillable wait_for_completion in bind_validate_region.

Negative signals:

* 0 No host-admin penalty. Host administrator privilege is not positively established as required for the complete trigger.
* 0 No race penalty. This is an ordered rollback/unwind state bug, not a narrow timing race.
* 0 No rare hardware penalty. Nouveau is hardware-specific, but the input does not establish rare or physical-only access.

Important non-awarded signals:

* RealUAF not awarded. The patch establishes a stale dirty state, not post-free object use.
* Controlled reclaim not demonstrated.
* Arbitrary or directed kernel write not demonstrated.
* Confidentiality and integrity impact not awarded. The evidence supports availability loss only.
* Remote reachability not established. This is a local DRM GPU control-plane path.
* Concrete repeated release/refcount not present. There is no first release that may end lifetime followed by a second lifetime mutation on the same dangling reference.
* Structured stale-object leverage not awarded. The stale state is a dirty flag and completion/state-machine inconsistency, not a consumed post-free structured object.
* Extra availability not awarded. The permanent bind failure and wait are the same availability consequence already counted.

3. Reachability analysis

The likely trigger is a local process that can use the nouveau VM_BIND uAPI and submit a bind job containing OP_UNMAP_SPARSE followed by a later failing operation. This does not require network access.

The relevant actor is a local graphics/GPU user, render client, compositor-adjacent process, or service with access to the nouveau DRM device. It is not shown to require host root or broad host administrator privileges, so HostAdminRequired=NO is appropriate for this triage. No namespace-scoped capability path is involved, so NamespaceScopedPrivilege=NO.

No prior host setup beyond having the nouveau driver and VM_BIND capable device in use is established. The bug is not a race and does not depend on special timing. It is a deterministic state-restoration failure in the unwind path.

4. Primitive and severity interpretation

The exact primitive is an invalid persistent state after rollback: OP_UNMAP_SPARSE marks a uvmm region dirty, a later job operation fails, the unwind path reinserts the region but previously failed to clear reg->dirty, and cleanup skips teardown because op->reg is cleared.

This is not active structured UAF and not fixed stale storage UAF. It is not a repeated release/refcount bug. The first operation does not free the object and no second lifetime-mutating operation on a dangling reference is shown.

PrimitiveClass=CLASS_C because the demonstrated behavior is invalid-state DoS: later binds fail with ENOENT or EINVAL or wait indefinitely for completion. The demonstrated consequence is local denial of service against the affected GPU VM context or process. A broader host compromise, information leak, arbitrary write, or privilege escalation is not supported by the supplied patch context.

ImportantCandidate=NO because there is no concrete memory corruption, ownership violation, authorization bypass, UAF, repeated lifetime mutation, or security-boundary primitive. AutoDowngradeAllowed=YES because the issue is a constrained local state cleanup DoS and no unresolved Important-grade exploitation leverage remains.

Likely operational severity is ordinary Moderate or Low-like depending on product exposure, because impact is limited to local GPU VM_BIND functionality and availability of the affected uvmm context.

5. One-sentence report phrase

A stale dirty flag in the nouveau VM_BIND OP_UNMAP_SPARSE unwind path can leave a uvmm region permanently dirty after a later job failure, causing subsequent binds over that range to fail or block indefinitely and resulting in local denial of service.

6. Manual review recommendation

NO MANUAL CHECK NEEDED

Reason: the patch supports a local state-consistency DoS only, with no UAF, no OOB access, no concrete kernel memory corruption, no authorization bypass, and no plausible privilege-escalation primitive requiring manual Important-class review.

7. Call-site confidence

Call-site confidence: high

======================================================================
UPSTREAM PATCH SUMMARY
======================================================================

Patch: drm/nouveau/uvmm: clear the dirty flag when unwinding an OP_UNMAP_SPARSE
Commit: a129b2b875c148aba233ace8447a0c36ca3bae07
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a129b2b875c148aba233ace8447a0c36ca3bae07

Commit description:

A successful OP_UNMAP_SPARSE marks its region dirty with
nouveau_uvma_region_dirty() and defers the teardown to
nouveau_uvmm_bind_job_cleanup(); it does not remove the region from
uvmm->region_mt.

If a later op in the job fails, the unwind path never clears reg->dirty
(set in one place, cleared nowhere) and sets op->reg = NULL, so cleanup
skips the teardown. The region is left in the tree with dirty set and its
completion never signalled. Later binds over that range then fail
permanently -- -ENOENT or -EINVAL from the dirty checks, or an unkillable
wait_for_completion() in bind_validate_region() -- for the lifetime of
the uvmm.

Clear reg->dirty when the unwind reverts the sparse unmap, restoring the
region to the state it was found in.

Fixes: b88baab ("drm/nouveau: implement new VM_BIND uAPI")
Reported-by: Yuhao Jiang <danisjiang@gmail.com>
Assisted-by: Claude:claude-opus-5
Cc: stable@vger.kernel.org
Signed-off-by: Zhenhao Wan <whi4ed0g@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Link: https://patch.msgid.link/20260811-nouveau-uvmm-vmbind-fixes-v2-3-aaee4b395d04@gmail.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/gpu/drm/nouveau/nouveau_uvmm.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=a129b2b875c148aba233ace8447a0c36ca3bae07

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

The original Linux kernel CVE announcement for CVE-2026-89800 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89800

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:L/PR:L/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: unknown
  Paranoid ActionableScore: 2

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).