[CVE-2026-99202][LOW] scsi: libsas: Fix SMP IO deadlock during HA resume [ Upstream

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

CVE: CVE-2026-99202
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: scsi: libsas: Fix SMP IO deadlock during HA resume [ Upstream
Commit: c9fb89246d9922ac0a45d504adb03e0bb971310c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9fb89246d9922ac0a45d504adb03e0bb971310c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99202
Analysis date: Wed, 28 Oct 2026 23:52:17 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
A synchronous runtime-PM resume during libsas HA resume can deadlock SMP PHY CONTROL and leave expander-attached SATA storage unavailable.

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

The original Linux kernel CVE announcement for CVE-2026-99202 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99202

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.

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AL-KERNEL CLASSIFICATION RESULT
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CVE-2026-99202	LOW	https://www.kernelcve.org/list/?q=CVE-2026-99202 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:H/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-833;CWE-667;CWE-662;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '4.7';DESCR 'A circular wait in libsas can deadlock HA resume when an expander attached SATA disk requires SMP PHY CONTROL. smp_execute_task_sg requests synchronous runtime PM resume while the device is already RPM_RESUMING, so it waits for resume while sas_drain_work waits for the same SMP command. For the CVSS the PR:L value in the paranoid vector reflects a local user or managed process that can request suspend or resume where system policy permits, while the base uses PR:H because reliable control of power transitions normally requires administrative authorization. The demonstrated impact is availability loss through a stuck HA resume and inaccessible storage. There is no invalid memory access, information leak, or write primitive. Automated impact decision path. The original SimpleNet classifier selected LOW. The primary LLM estimated paranoid CVSS 4.7 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 1.9 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	LOCK DEADLOCK RACE LEAK HARDWARE 	-	-	checked

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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 base score: 1
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1
* Paranoid score: 1; unsupported low-priv reachability is not scored.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Reliable strong DoS: synchronous runtime-PM resume creates a circular wait against `sas_drain_work()`, leaving HA resume and affected storage stuck.
* No additional availability point: inaccessible storage is the consequence of the same deadlock.
* No memory-corruption points: the patch shows no UAF, OOB access, overwrite, stale object, or lifetime mutation.
* No authorization points: the fix changes runtime-PM reference/resume behavior, not a DENY-to-ALLOW security decision.
* No privilege penalty: host-administrator control of the complete trigger is not positively established.
* No race penalty: this is a defined circular-wait sequence, not evidence of a narrow, unreliable timing race.
* No hardware penalty: an expander-attached SATA topology is required, but the evidence does not establish rare or attacker-supplied hardware.

3. Reachability analysis

The vulnerable sequence requires HA resume, an expander-attached SATA disk, ATA error-handler reset, and SMP PHY CONTROL. The BSG path is separately fixed to resume an autosuspended host, but the supplied evidence does not show that an ordinary local user can induce the complete HA-resume deadlock. Administrative power-management control is also not conclusively required. Thus host privilege and UID-0 requirements remain unknown. No namespace-scoped trigger, remote path, special sysctl, or attacker-controlled retry sequence is shown.

4. Primitive and severity reading

The exact defect is a runtime-PM lock-order/circular-wait deadlock. It is CLASS_C availability behavior, not active-state corruption or a retry-accumulated OOB write. The demonstrated effect is stalled HA resume and unavailable storage; kernel panic, memory corruption, confidentiality loss, integrity loss, and privilege escalation are unproven. ImportantCandidate is therefore NO, and automatic Moderate downgrade is safe.

5. One-sentence report phrase

A synchronous runtime-PM resume during libsas HA resume can deadlock SMP PHY CONTROL and leave expander-attached SATA storage unavailable.

6. Manual review advice

NO MANUAL CHECK NEEDED

The patch establishes a configuration-dependent availability deadlock without a corruption or security-boundary primitive.

7. Call-site confidence

Call-site confidence: high

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

Patch: scsi: libsas: Fix SMP IO deadlock during HA resume [ Upstream
Commit: c9fb89246d9922ac0a45d504adb03e0bb971310c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c9fb89246d9922ac0a45d504adb03e0bb971310c

Changed files:
  drivers/scsi/libsas/sas_expander.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=c9fb89246d9922ac0a45d504adb03e0bb971310c

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

The original Linux kernel CVE announcement for CVE-2026-99202 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99202

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:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.7

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