* [CVE-2026-98344][LOW] dmaengine: Fix device kref underflow in dma_chan_put() [ Upstream
@ 2026-10-10 13:38 21% AL-KERNEL
0 siblings, 0 replies; 1+ results
From: AL-KERNEL @ 2026-10-10 13:38 UTC (permalink / raw)
To: kernel-cve
CVE: CVE-2026-98344
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: dmaengine: Fix device kref underflow in dma_chan_put() [ Upstream
Commit: 036b527f92570206da4b8c40b38f8d689e29d0f3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=036b527f92570206da4b8c40b38f8d689e29d0f3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98344
Analysis date: Sat, 10 Oct 2026 09:38:41 -0400
ActionableScore: 1
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-2026-98344 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98344
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-2026-98344 LOW https://www.kernelcve.org/list/?q=CVE-2026-98344 CHECK WITH IMPACT FROM ORIG NN LOW | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (independent Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE_KPANIC) 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-911;CWE-682;*CWE-664;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'An imbalance between dma_chan_get and dma_chan_put can drop one extra DMA device reference for every fast path get and put pair. The issue requires a non-private provider with one persistent client and another client that repeatedly cycles DMA engine acquisition and release. The device kref can eventually reach zero while the provider module remains loaded, after which dma_find_channel can no longer return the affected channel. This can make DMA dependent functionality unavailable and may cause a denial of service if the affected provider is required by critical workloads. For the CVSS the PR:L value in the paranoid score represents environments where a restricted local service or user controlled consumer can repeatedly reach the DMA client path without full administrative control. The issue is not network reachable by itself. No confidentiality or integrity impact is assigned because the demonstrated primitive is premature reference depletion rather than UAF, OOB access, or arbitrary memory modification.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1) MAYBE OOB HARDWARE MEMORY DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED - - checked
======================================================================
ACTIONABLESCORE ANALYSIS
======================================================================
ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO
1. ActionableScore
* Raw conservative score: 1
* Conservative score: 1
* Raw paranoid score: 1
* Paranoid score: 1
* No floor or cap applied.
* Final recommended bucket: **Ordinary Moderate**::
2. Signal breakdown
Positive signals:
* +1 Availability impact realistic. Repeated fast-path get and put cycles can prematurely reduce the DMA device kref to zero, after which `dma_find_channel()` returns NULL and DMA-dependent functionality becomes unavailable.
Negative signals:
* No negative points applied. The privilege boundary, hardware dependency, and userspace reachability are unresolved rather than proven restrictive.
Important non-awarded signals:
* Real UAF +2 not awarded. The supplied evidence establishes premature kref depletion, but not freeing of `struct dma_device` followed by stale access.
* Concrete repeated release/refcount +1 not awarded. Repeated `dma_device_put()` calls are concrete, but the supplied and normally established DMA-engine semantics show the zero transition primarily invoking the device release completion. Actual object destruction or freeing followed by mutation through a dangling reference is not established.
* Reliable kernel crash +1 not awarded. The demonstrated consequence is channel lookup failure and device unavailability, not panic or host-wide fatal fault.
* Strong or constrained overwrite not awarded. There is no heap OOB write, attacker-selected payload, or target.
* Resource-leak signal not awarded. This is premature reference depletion rather than a missing release.
* No C/I, controlled reclaim, arbitrary write, callback influence, authorization bypass, or privilege escalation is established.
* B5-R does not apply because no retry-accumulated heap OOB write exists.
* B3-PENDING does not apply because no shared-backing write exists.
* B4-PENDING does not apply because no DENY-to-ALLOW authorization decision is changed.
* No extra paranoid point was awarded merely because additional puts could encounter an already exhausted kref.
Repeated-refcount checks:
* First release can end object lifetime: not established for this DMA device object.
* Exact same device reference survives: the channel continues to contain `chan->device`, but dangling-object status is not established.
* Second operation mutates the kref: yes, repeated fast-path cycles can invoke another `dma_device_put()`.
* Dedicated repeated-release/refcount +1: withheld because the first zero transition is not shown to free or destroy the referenced object.
* Paranoid repeated-refcount leverage +1: withheld for the same reason.
* FLOOR 5: not applicable because RealUAF is not established.
3. Reachability analysis
The complete trigger requires a non-private DMA provider, one persistent kernel client keeping `client_count` above zero, and another client repeatedly cycling `dmaengine_get()` and `dmaengine_put()`. No ordinary userspace API, ioctl, namespace capability, or network path that allows an attacker to perform this complete sequence is supplied.
Host-admin privilege is not positively established, but below-host-admin reachability is also not established. Therefore `HostAdminRequired=UNKNOWN`. No namespace-scoped trigger chain, prior setup boundary, specific hardware rarity, or timing race is demonstrated. The issue is deterministic once the required client arrangement and repeated get/put activity exist.
4. Primitive and severity interpretation
The exact primitive is unbalanced reference-count mutation. The slow path obtains one device kref, while every fast-path put incorrectly drops another kref. This can force the reference count to zero while a persistent client still uses the provider and can make subsequent channel discovery fail.
This is an invalid lifetime-accounting state, but not a demonstrated post-free access. It therefore differs from a repeated-release UAF where the first put frees an object and a second put mutates reclaimed storage. `PrimitiveClass=CLASS_C` is appropriate because the demonstrated security consequence is device or service unavailability without an independently useful corruption primitive.
`ImportantCandidate=NO` because no memory overwrite, real UAF, security-boundary bypass, controlled lifetime takeover, or host-wide crash is established. `AutoDowngradeAllowed=YES` because no meaningful unresolved Important-grade primitive would be lost by treating this as an ordinary availability issue.
Likely operational severity is Low to ordinary Moderate, depending on how critical the affected DMA provider is to the system.
5. One-sentence report phrase
An imbalance between dma_chan_get and dma_chan_put can prematurely exhaust a DMA device kref and make its channels unavailable, but the supplied evidence establishes device-level denial of service rather than UAF, memory corruption, or privilege escalation.
6. Manual review recommendation
NO MANUAL CHECK NEEDED
The demonstrated primitive is deterministic reference-accounting failure with device unavailability, and no Important-preserving corruption or authorization primitive is established.
7. Call-site confidence
Call-site confidence: medium
======================================================================
UPSTREAM PATCH SUMMARY
======================================================================
Patch: dmaengine: Fix device kref underflow in dma_chan_put() [ Upstream
Commit: 036b527f92570206da4b8c40b38f8d689e29d0f3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=036b527f92570206da4b8c40b38f8d689e29d0f3
Changed files:
drivers/dma/dmaengine.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=036b527f92570206da4b8c40b38f8d689e29d0f3
======================================================================
DETAILED REPORT METHODOLOGY
======================================================================
The original Linux kernel CVE announcement for CVE-2026-98344 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-98344
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:H/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: 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).
^ permalink raw reply [relevance 21%]
Results 1-1 of 1 | reverse | sort options + mbox downloads above
-- links below jump to the message on this page --
2026-10-10 13:38 21% [CVE-2026-98344][LOW] dmaengine: Fix device kref underflow in dma_chan_put() [ Upstream AL-KERNEL
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox