[CVE-2026-64254][LOW] NTB: epf: Avoid pci_iounmap() with offset when PEER_SPAD and CONFIG share BAR

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

CVE: CVE-2026-64254
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: NTB: epf: Avoid pci_iounmap() with offset when PEER_SPAD and CONFIG share BAR
Commit: eb47b9bffd07a47b84910847cb5ea066ce184055
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eb47b9bffd07a47b84910847cb5ea066ce184055
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64254
Analysis date: Fri, 24 Jul 2026 11:51:50 -0400
ActionableScore: 0
ActionableScore lower bound: unknown
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-2026-64254 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64254

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-2026-64254	LOW	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:H/UI:N/S:U/C:N/I:N/A:H';CWE-763;CWE-404;*CWE-664;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.4';DESCR 'NTB epf teardown can call pci_iounmap on peer_spad_reg even when PEER_SPAD and CONFIG share the same PCI BAR. In that layout peer_spad_reg is an offset inside an existing mapped BAR rather than a separately mapped vm area, so module removal can trigger a kernel warning in vunmap. For the CVSS the PR:H is used because reliable triggering normally requires administrative control over module unload or PCI driver teardown. The issue is not network reachable and is tied to local device driver removal. Impact is mainly availability limited to a warning or a crash only on systems that treat WARN as fatal.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 0)  SKIP CVE-2026-64254 UNKNOWN SKIP No affected files built, so skip this CVE NO  - - unknown 	MAYBE	WARNONLY HARDWARE 	-	-	checked

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

ActionableScore=0

1. ActionableScore
* Conservative score: 0
* Paranoid score: 0
* Final recommended bucket: **Ordinary Moderate / Low-like**::

2. Signal breakdown
* Requires admin/root/CAP in typical deployments: -2. Triggering requires module unload, driver teardown, or PCI driver management, normally requiring host administrative privileges.
* Rare AND difficult-to-reach subsystem/configuration: -1. NTB EPF hardware and this shared BAR layout are not broadly exposed default paths.
* Reliable kernel crash / strong DoS: +0. The commit shows a WARN from `vunmap()` on an invalid iounmap address, not a demonstrated Oops, panic, UAF, double free, or attacker-controlled corruption.
* Availability impact realistic: +0. Availability impact is mainly relevant on `panic_on_warn` systems, so it is not counted as a strong default signal.
* Generic memory corruption: +0. The patch prevents an invalid `pci_iounmap()` call on an offset into an already mapped BAR, but does not show a reclaim primitive, overwrite, stale object reuse, or type confusion.
* Call-site confidence: high. The teardown call site is present in the patch and the failure mode is directly described by the warning trace.

3. Reachability analysis
The bug is triggered during NTB EPF PCI driver teardown when `BAR_PEER_SPAD` and `BAR_CONFIG` share the same PCI BAR. A normal local unprivileged user cannot reliably trigger this path because module removal and PCI driver detach are privileged operations. Containers or namespaces do not materially reduce the privilege requirement unless a container is explicitly delegated host-level device or module management, which is uncommon. The path is not network reachable and depends on specific NTB EPF hardware and BAR configuration.

4. Severity interpretation
This behaves like a low-priority correctness and teardown robustness issue rather than an Important-class kernel vulnerability. The theoretical impact is a warning or, on hardened systems with `panic_on_warn`, a local privileged DoS. The patch does not support privilege escalation, confidentiality impact, integrity impact, or a practical memory corruption primitive.

5. One-sentence report phrase
NTB EPF driver teardown may call `pci_iounmap()` on an offset inside a shared PCI BAR, causing a kernel warning during privileged module or driver removal, with practical impact limited to local privileged DoS on configurations that treat WARN as fatal.

6. Manual review recommendation
NO MANUAL CHECK NEEDED. The issue requires privileged local teardown of a rare device path and shows only a WARN-level failure without evidence of exploitable memory corruption or security-boundary bypass.

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

Patch: NTB: epf: Avoid pci_iounmap() with offset when PEER_SPAD and CONFIG share BAR
Commit: eb47b9bffd07a47b84910847cb5ea066ce184055
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eb47b9bffd07a47b84910847cb5ea066ce184055

Commit description:

When BAR_PEER_SPAD and BAR_CONFIG share one PCI BAR, the module teardown
path ends up calling pci_iounmap() on the same iomem with some offset,
which is unnecessary and triggers a kernel warning like the following:

  Trying to vunmap() nonexistent vm area (0000000069a5ffe8)
  WARNING: mm/vmalloc.c:3470 at vunmap+0x58/0x68, CPU#5: modprobe/2937
  [...]
  Call trace:
   vunmap+0x58/0x68 (P)
   iounmap+0x34/0x48
   pci_iounmap+0x2c/0x40
   ntb_epf_pci_remove+0x44/0x80 [ntb_hw_epf]
   pci_device_remove+0x48/0xf8
   device_remove+0x50/0x88
   device_release_driver_internal+0x1c8/0x228
   driver_detach+0x50/0xb0
   bus_remove_driver+0x74/0x100
   driver_unregister+0x34/0x68
   pci_unregister_driver+0x34/0xa0
   ntb_epf_pci_driver_exit+0x14/0xfe0 [ntb_hw_epf]
  [...]

Fix it by unmapping only when PEER_SPAD and CONFIG use difference bars.

Cc: stable@vger.kernel.org
Fixes: e75d5ae ("NTB: epf: Allow more flexibility in the memory BAR map method")
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  mm/vmalloc.c
  drivers/ntb/hw/epf/ntb_hw_epf.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=eb47b9bffd07a47b84910847cb5ea066ce184055

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

The original Linux kernel CVE announcement for CVE-2026-64254 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64254

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:H/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 4.4

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: 0

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).