[CVE-2026-89553][MODERATE 7.0] nouveau/gem: reserve the bo in the info ioctl around the vma lookup

[CVE-2026-89553][MODERATE 7.0] nouveau/gem: reserve the bo in the info ioctl around the vma lookup

[AL-KERNEL]

CVE: CVE-2026-89553
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: nouveau/gem: reserve the bo in the info ioctl around the vma lookup
Commit: 208867763843aa82efcbe3b771f1b8e6c7aa820a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=208867763843aa82efcbe3b771f1b8e6c7aa820a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89553
Analysis date: Fri, 11 Sep 2026 18:46:02 -0400
ActionableScore: 6
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.

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

The original Linux kernel CVE announcement for CVE-2026-89553 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89553

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.

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

CVE-2026-89553	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-89553 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-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '7';DESCR 'A use-after-free race exists in the nouveau GEM info ioctl path because nouveau_gem_info() can look up a VMA while the GEM close path concurrently closes and frees the same VMA. A local process with access to the nouveau DRM device can potentially trigger the race by invoking the info ioctl while another path closes the GEM mapping. For the CVSS the PR:L is used because reliable triggering requires local code execution and access to the DRM device, not full administrator privileges. The issue is not network reachable. Impact is at least a local denial of service via kernel crash or memory fault, with possible limited confidentiality exposure from stale VMA data. In the paranoid interpretation, a kernel use-after-free race may also have integrity and privilege escalation relevance if freed memory can be reused in a controlled way, so manual review is recommended.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	YES	RACE UAF HARDWARE LINUS KPANIC 	NO	NO	checked

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

ActionableScore=6
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4. No floor or cap changed the score.
* Raw paranoid score: 6
* Paranoid score: 6. No floor or cap changed the score.
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

2. Signal breakdown

Conservative signals:

* +2 Real UAF / active lifetime violation. The commit directly states a race where nouveau_gem_info() finds a VMA and the GEM close path can close/free that VMA before use.
* +1 Local below-host-admin reachability. The vulnerable path is a DRM GEM info ioctl reachable by a local process with access to the nouveau DRM device, not by host-admin-only kernel configuration.
* +1 Reliable kernel crash / strong DoS. A kernel use-after-free in an ioctl path can realistically cause a fault or crash, even though the patch does not demonstrate a stronger primitive.

Paranoid additional signals:

* +1 Attacker-influenced repeatable lifetime manipulation. The same local DRM client model can repeatedly drive GEM info lookups and GEM close/lifetime transitions, making the race more than a one-shot teardown event.
* +1 Structured stale-object leverage / limited stale-field exposure concern. The stale object is an active nouveau VMA and the stale use reads vma->addr into the ioctl reply, so there is unresolved leverage beyond a pure immediate NULL dereference.

Non-awarded signals:

* Controlled reclaim not demonstrated.
* Arbitrary write not demonstrated.
* Callback or function-pointer control not demonstrated.
* Concrete repeated release/refcount mutation not established. The stale use is a read of vma->addr, not a second put/free/refcount operation.
* Weak LPE was not separately awarded because privilege escalation is not established by the patch.
* Extra Availability was not awarded because the same crash/DoS is already counted once.
* C/I were not awarded as separate strong consequences. Possible stale data exposure is treated only as a paranoid unresolved leverage signal.
* Remote reachability not established.

3. Reachability analysis

The evaluated attacker is a local process with access to the nouveau DRM device. This is commonly below host administrator in desktop or graphics workloads, for example a logged-in user, compositor-related process, or user in the appropriate DRM/render access group. The complete operation is an ioctl on an existing nouveau GEM object and does not require network access.

HostAdminRequired=NO because the supplied context and normal DRM GEM ioctl model support below-host-admin access for a process that can open the relevant DRM device. NamespaceScopedPrivilege=NO because no namespace-scoped capability path is involved or needed. Prior host setup may exist in the ordinary sense that the nouveau driver and device must be present, but that is not a separate attacker privilege prerequisite. The race is timing-dependent, but the attacker can plausibly repeat the relevant ioctl/close operations, so no hard-race penalty is applied.

4. Primitive and severity interpretation

The exact primitive is a race-induced use-after-free of a nouveau VMA object in nouveau_gem_info(). The object is active structured state rather than fixed stale storage. The stale use is narrower than a strong corruption primitive: the code performs nouveau_vma_find(), then reads vma->addr after the close path may have freed the VMA.

This is CLASS_B because a real kernel lifetime violation exists, but controlled reclaim, arbitrary read/write, callback hijack, or demonstrated LPE are not established. The demonstrated practical consequence is local DoS via kernel fault/crash. The speculative consequence is stronger exploitation if a local attacker can reliably shape reuse of the freed VMA storage or obtain useful stale data from the returned offset field.

ImportantCandidate=YES because this is a real locally reachable DRM kernel UAF with unresolved active-object lifetime leverage. AutoDowngradeAllowed=NO because automatic closure would discard a concrete kernel UAF primitive reachable below host admin, even though it is not yet a proven Strong Important exploit.

5. One-sentence report phrase

A local nouveau DRM user can race GEM info ioctl VMA lookup against GEM close so that nouveau_gem_info() reads vma->addr from a freed VMA object, causing at least local kernel DoS and requiring manual review for possible stale object reuse or limited disclosure leverage.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a concrete local kernel use-after-free in a DRM ioctl path with below-host-admin reachability and unresolved active-object exploitation leverage.

7. Call-site confidence

Call-site confidence: medium

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

Patch: nouveau/gem: reserve the bo in the info ioctl around the vma lookup
Commit: 208867763843aa82efcbe3b771f1b8e6c7aa820a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=208867763843aa82efcbe3b771f1b8e6c7aa820a

Commit description:

In the non-uvmm path, there could be a race between the info lookup
finding the vma, and the gem close path closing the vma leading
to a use-after-free.

Spotted with the help of Opus 4.6.

Signed-off-by: Dave Airlie <airlied@redhat.com>
Fixes: e758a31 ("drm/nouveau: fixup gem_info ioctl to return client-specific bo virtual")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260612020658.3176270-1-airlied@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_gem.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=208867763843aa82efcbe3b771f1b8e6c7aa820a

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

The original Linux kernel CVE announcement for CVE-2026-89553 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-89553

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:L/UI:N/S:U/C:L/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: 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: 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 alexanjelausa@gmail.com (and both
send reply to CVE record itself too and see "reply" button below for howto reply).