[CVE-2026-80571][MODERATE 7.0] powerpc/pseries: papr-phy-attest - validate cmd.length, plug mem leak

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

CVE: CVE-2026-80571
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: powerpc/pseries: papr-phy-attest - validate cmd.length, plug mem leak
Commit: 828a8d1a9107aec6353d896882df8383accf7e80
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=828a8d1a9107aec6353d896882df8383accf7e80
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80571
Analysis date: Wed, 26 Aug 2026 12:18:07 -0400
ActionableScore: 7
ActionableScore lower bound: 5
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A user controlled length in the powerpc pseries papr physical attestation driver was not validated before use, allowing a local caller with access to the device to potentially trigger a kernel buffer overflow and crash or corrupt kernel memory.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-80571 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80571

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
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CVE-2026-80571	MODERATE	CHECK WITH IMPACT FROM ORIG NN 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:H/I:H/A:H';*CWE-787;CWE-120;*CWE-20;*CWE-401;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'A kernel buffer overflow may occur in the powerpc pseries papr physical attestation character driver because params cmd length is copied from user input and used without validating that it is non zero and within the size of the command structure. A local attacker with access to the papr physical attestation device can provide an oversized length value and may corrupt kernel memory during the attestation command handling path. For the CVSS the PR:L is used because reliable triggering requires local code execution and access to the exposed character device or its ioctl path, but it does not necessarily require full administrator privileges if device permissions or delegated service access allow use by a non root process. The issue is not network reachable and is limited to local systems on affected powerpc pseries configurations where this driver is present and accessible. Impact is at least a local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel memory corruption, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 7)	YES	LEAK UAF HARDWARE LINUS  KPANIC INCREASED_TO_MODERATE_FROM_LOW_BASED_ON_GUESSCVSS KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN6 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP	YES	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=5

## 1. ActionableScore

* Conservative score: 5
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged trigger: +1. The vulnerable value comes from a userspace supplied command passed to a character driver ioctl or file operation, assuming the device node is accessible to a non-root user or delegated service.
* Constrained kernel buffer overwrite: +1. The patch explicitly says the unchecked `cmd.length` can result in a buffer overflow, but the diff alone does not show a fully controlled target or payload.
* Reliable kernel crash / strong DoS: +1. A kernel-side overflow in a pseries RTAS attestation path can plausibly crash the kernel.
* Privileged kernel/device-management memory corruption path: +1. The bug is in a platform attestation driver interacting with trusted pseries/RTAS functionality.
* Confidentiality impact plausible: +1. Limited C impact is defensible because kernel memory corruption may expose adjacent state, but no direct info leak is shown.
* Integrity impact plausible: +1. Limited I impact is defensible because the unchecked length may corrupt kernel memory.
* Rare AND difficult-to-reach subsystem/configuration: -1. This is limited to affected powerpc pseries systems with the papr physical attestation driver present and reachable.

Paranoid additions:

* Memory corruption, strong corruption primitive: +2 instead of constrained +1. The commit explicitly identifies a buffer overflow from a user-controlled length field before validation.
* Privilege escalation plausible: +1. LPE is not demonstrated, but kernel buffer overflow from local input is sufficient for manual-review sensitivity.

## 3. Reachability analysis

The likely trigger is a local user or local service able to open and use the papr physical attestation character device. It is not network reachable. Namespace or container impact depends on whether the device node is passed into the container or exposed to a reduced-privilege service. If only full host root can access the device, practical severity drops. If non-root users, service accounts, or containerized workloads can access it, PR:L is appropriate. The affected platform is not broad-default Linux exposure, but it is security-relevant on IBM powerpc pseries systems using physical attestation.

Call-site confidence: medium. The changed function and direct user-controlled length validation are visible, but the downstream use of `cmd_len` is not included in the supplied diff.

## 4. Severity interpretation

This is more than ordinary Moderate because the patch explicitly fixes a user-controlled length validation bug described as a buffer overflow in kernel code. The conservative view treats the overflow as constrained because the exact overwrite target and payload control are not shown. The paranoid view treats it as a Strong Important candidate because local kernel buffer overflows can become privilege escalation candidates and should not be auto-closed without manual review.

## 5. One-sentence report phrase

A user controlled length in the powerpc pseries papr physical attestation driver was not validated before use, allowing a local caller with access to the device to potentially trigger a kernel buffer overflow and crash or corrupt kernel memory.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED. The patch explicitly describes a buffer overflow from user-controlled input in kernel device-management code, so the exact downstream copy path and overwrite controllability should be reviewed manually before downgrading.

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

Patch: powerpc/pseries: papr-phy-attest - validate cmd.length, plug mem leak
Commit: 828a8d1a9107aec6353d896882df8383accf7e80
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=828a8d1a9107aec6353d896882df8383accf7e80

Commit description:

In papr_phy_attest_create_handle(), the params->cmd.length is not
validated before use, which can result in a buffer overlow.  Check it and
return -EINVAL if it is either 0 or exceeds sizeof(params->cmd).

Also, params is freed on the success path but not error. Free it on
errors after memory allocation.  And free it on negative fd.

Fixes: 86900ab ("powerpc/pseries: Add a char driver for physical-attestation RTAS")
Acked-by: Haren Myneni <haren@linux.ibm.com>
Acked-by: Nayna Jain <nayna@linux.ibm.com>
Tested-by: R Nageswara Sastry <rnsastry@linux.ibm.com>
Cc: stable@vger.kernel.org # 6.16
Signed-off-by: George Wilson <gcwilson@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  arch/powerpc/platforms/pseries/papr-phy-attest.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=828a8d1a9107aec6353d896882df8383accf7e80

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

The original Linux kernel CVE announcement for CVE-2026-80571 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80571

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:L/UI:N/S:U/C:L/I:L/A:H
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 7.8

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: 5
  Paranoid ActionableScore: 7

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).