[CVE-2026-46298][LOW] pseries/papr-hvpipe: Fix race with interrupt handler

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

CVE: CVE-2026-46298
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: pseries/papr-hvpipe: Fix race with interrupt handler
Commit: 342c966f81cfc3cb6c297e80b37a9f3a5d637d2c
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=342c966f81cfc3cb6c297e80b37a9f3a5d637d2c
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46298
Analysis date: Mon, 08 Jun 2026 15:04:21 -0400
ActionableScore: 1
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-46298 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46298

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
======================================================================

CVE-2026-46298	LOW	CHECK	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-667;CWE-362;*CWE-833;BEST CVSS score: '4.7';DESCR 'A local deadlock can occur in the powerpc pseries papr-hvpipe character driver because ioctl or release paths used a normal spin lock while an interrupt handler on the same CPU could try to take the same lock. This can lock the CPU in the kernel and cause denial of service on affected pseries systems with the HVPIPE driver enabled. For the CVSS the PR:L is used because an attacker needs local access to the device interface or a process context able to trigger the relevant ioctl or file release path, but full administrative privileges are not necessarily implied by the code path itself. The issue is not network reachable and is not a memory corruption primitive. Impact is availability only via local kernel deadlock, with no supported path to information disclosure or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) 	MAYBE	LOCK DEADLOCK SIMPLEFIX RACE HARDWARE LINUS  DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS_AND_CIANNH	-	-	checked

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

ActionableScore=1
ActionableScoreLower=1

1. ActionableScore
* Conservative score: 1
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**::

2. Signal breakdown
* Local unprivileged trigger: +1. A local process with access to the papr-hvpipe character device can enter ioctl or release paths.
* Reliable kernel crash / strong DoS: +1. The bug can deadlock the CPU if an interrupt handler tries to take the same spinlock while the process path already holds it.
* Hard or unreliable race / special timing required: -1. The deadlock requires an interrupt to fire on the same CPU during a narrow lock-held window.
* Rare AND difficult-to-reach subsystem/configuration: -1. This is limited to powerpc pseries systems with the papr-hvpipe HVPIPE driver enabled and reachable.
* No memory corruption: 0. The patch only changes spin_lock to spin_lock_irqsave and corresponding unlocks. No UAF, OOB write, object confusion, or lifetime corruption is indicated.
* No privilege escalation plausible: 0. The primitive is a local IRQ locking deadlock, not a corruption or policy-bypass primitive.

3. Reachability analysis
A local process must be able to open/use the papr-hvpipe device and trigger ioctl or file release. This is not network reachable. Namespace/container relevance appears low unless the device node is explicitly exposed into a container. The affected path is platform-specific to powerpc pseries HVPIPE support, so exposure is narrow compared with common kernel subsystems.

4. Severity interpretation
This behaves like an ordinary Moderate or Low-like local DoS issue. The theoretical impact is a CPU or kernel hang from lock recursion with interrupts enabled, but there is no evidence of memory corruption, sensitive data exposure, privilege escalation, or cross-boundary bypass. The practical risk is mainly availability loss on affected pseries systems.

5. One-sentence report phrase
A local deadlock in the powerpc pseries papr-hvpipe driver can occur when ioctl or release holds a spinlock and a same-CPU interrupt handler tries to acquire it, causing a local denial of service on affected systems.

6. Manual review recommendation
NO MANUAL CHECK NEEDED. This is a platform-specific local DoS-only locking bug with no supported memory-corruption or privilege-escalation primitive.

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

Patch: pseries/papr-hvpipe: Fix race with interrupt handler
Commit: 342c966f81cfc3cb6c297e80b37a9f3a5d637d2c
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=342c966f81cfc3cb6c297e80b37a9f3a5d637d2c

Commit description:

While executing ->ioctl handler or ->release handler, if an interrupt
fires on the same cpu, then we can enter into a deadlock.

This patch fixes both these handlers to take spin_lock_irq{save|restore}
versions of the lock to prevent this deadlock.

Cc: stable@vger.kernel.org
Fixes: 814ef09 ("powerpc/pseries: Add papr-hvpipe char driver for HVPIPE interfaces")
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/e4ed435c44fc191f2eb23c7907ba6f72f193e6aa.1777606826.git.ritesh.list@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  arch/powerpc/platforms/pseries/papr-hvpipe.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=342c966f81cfc3cb6c297e80b37a9f3a5d637d2c

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

The original Linux kernel CVE announcement for CVE-2026-46298 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46298

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: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: 1
  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).