From: AL-KERNEL <[email protected]>
To: [email protected]
Subject: [CVE-2026-99145][LOW] drm/xe: Don't transfer shrinker pages for pinned bos on purgeable state change
Date: Fri, 30 Oct 2026 11:14:20 -0400 [thread overview]
Message-ID: <[email protected]> (raw)
CVE: CVE-2026-99145
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: drm/xe: Don't transfer shrinker pages for pinned bos on purgeable state change
Commit: 135e998dd1e66b8854db7bd356b6563baf8b9d51
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=135e998dd1e66b8854db7bd356b6563baf8b9d51
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99145
Analysis date: Fri, 30 Oct 2026 11:14:20 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO
Summary:
A local DRM user can change the purgeable state of a pinned Xe BO and corrupt shrinker accounting, potentially degrading reclaim behavior under memory pressure.
======================================================================
ABOUT THIS REPORT
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99145 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99145
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-2026-99145 LOW https://www.kernelcve.org/list/?q=CVE-2026-99145 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT LOW AEGIS_AS=1 LEGACY=LOW RESULT=SAME (final reconciliation agrees; DECISION: both 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:L';CWE-682;CWE-191;**CWE-400;BEST CVSS score: '3.3';DESCR 'An accounting logic bug in drm xe allows a purgeable state change on a pinned BO to transfer pages between shrinker counters even though pinned BO pages are not currently accounted. A local user able to manage the relevant DRM BO and change its VMA state to DONTNEED while the BO remains pinned as a scanout buffer can underflow one counter and leave another counter permanently inflated after unpin. For the CVSS the PR:L value reflects the required local DRM user context and control of the affected BO. The issue is not directly network reachable and no UAF, OOB access, information leak, arbitrary write, or privilege escalation primitive is supported. Impact is limited to inaccurate reclaim accounting and possible availability degradation under memory pressure. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 3.3 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. No severity changing production threshold or specialist override was recorded. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was LOW. The shadow agreed with the final production impact and aggregation did not change that impact. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE OOB SIMPLEFIX LEAK HARDWARE - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=NO
NamespaceScopedPrivilege=NO
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=NO
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw base score: 1.
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1.
* Paranoid score: 1; no stronger technically supported consequence.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
* **+1 possible availability degradation:** changing purgeability while a BO is pinned underflows one shrinker count and leaves the other permanently inflated after unpin. Incorrect reclaim accounting can impair memory-pressure handling.
* **+0 weak bookkeeping corruption:** the changed state consists of shrinker counters and a purgeability flag; no pointer, allocation boundary, object lifetime, or security-sensitive field is corrupted.
* No reliable kernel crash, host-wide exhaustion, persistent resource/reference leak, UAF, OOB access, arbitrary write, disclosure, authorization bypass, or privilege escalation is shown.
* NEW52/B5-R does not apply: there is no retry-accumulated heap OOB write or later consumption of an overwritten descriptor.
* NEW53/B3-PENDING does not apply: no shared/file-backed storage write is involved.
* No extra availability point is awarded because only speculative degradation under memory pressure is supported.
3. Reachability analysis
The commit identifies a userspace-triggered sequence: apply DONTNEED to a VMA belonging to a BO that remains pinned as a scanout buffer. The supplied triage evidence characterizes this as a local DRM user context with control of the affected BO, supporting below-host-administrator reachability and no host UID 0 requirement. It does not involve namespace-scoped capabilities or network access.
A pinned scanout BO and affected Intel Xe hardware are prerequisites, but the hardware is not established as rare and no timing race is required. Exact DRM master/render-node permission details are not visible in the patch.
4. Primitive and severity reading
The primitive is persistent but passive reclaim-accounting corruption: pages are transferred between counters despite pinned BO pages being excluded from accounting. The fix uses zero pages for pinned BOs while still updating the purgeability flag.
This is CLASS_C bookkeeping/availability behavior, not active structured-state corruption consumed as a memory-safety primitive. The shown effect is inaccurate shrinker accounting; stronger memory exhaustion or a crash remains unproven. ImportantCandidate is therefore NO, and automatic downgrade is safe.
5. One-sentence report phrase
A local DRM user can change the purgeable state of a pinned Xe BO and corrupt shrinker accounting, potentially degrading reclaim behavior under memory pressure.
6. Manual review advice
NO MANUAL CHECK NEEDED
The patch supports only constrained accounting corruption with low availability impact and no unresolved security primitive.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: drm/xe: Don't transfer shrinker pages for pinned bos on purgeable state change
Commit: 135e998dd1e66b8854db7bd356b6563baf8b9d51
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=135e998dd1e66b8854db7bd356b6563baf8b9d51
Commit description:
Pinned bos have their pages removed from the shrinker's shrinkable /
purgeable counts on pin, and added back on unpin according to the
bo's purgeable state at that time.
However, xe_bo_set_purgeable_shrinker() unconditionally transfers
pages between the shrinkable and purgeable counts. If the purgeable
state of a pinned bo changes, for example by userspace madvising
DONTNEED on a VMA of a bo that is also pinned as a scanout buffer,
this underflows one count and, after unpin, leaves the other one
permanently inflated.
Only update the purgeable flag for pinned bos, and leave the page
accounting to unpin.
Fixes: 536a2ea ("drm/xe/bo: Add purgeable shrinker state helpers")
Cc: Arvind Yadav <[email protected]>
Cc: Matthew Brost <[email protected]>
Cc: Himal Prasad Ghimiray <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Matthew Auld <[email protected]>
Cc: [email protected]
Cc: <[email protected]> # v7.1+
Assisted-by: LLM
Signed-off-by: Thomas Hellström <[email protected]>
Reviewed-by: Matthew Auld <[email protected]>
Link: https://patch.msgid.link/[email protected]
(cherry picked from commit afe6bc012034123fd838328668e609bf57e46bd3)
Signed-off-by: Rodrigo Vivi <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Changed files:
drivers/gpu/drm/xe/xe_bo.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=135e998dd1e66b8854db7bd356b6563baf8b9d51
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-99145 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99145
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: Not available
The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L
The Best / paranoid CVSS score: 3.3
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: 1
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 [email protected] (and both
send reply to CVE record itself too and see "reply" button below for howto reply).
reply other threads:[~2026-10-30 15:14 UTC|newest]
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