[CVE-2026-46268][LOW] PCI/P2PDMA: Fix p2pmem_alloc_mmap() warning condition [ Upstream

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

CVE: CVE-2026-46268
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: PCI/P2PDMA: Fix p2pmem_alloc_mmap() warning condition [ Upstream
Commit: eb9aa9f8010465d927864f5a35bdc5604b0ff51a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eb9aa9f8010465d927864f5a35bdc5604b0ff51a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46268
Analysis date: Wed, 03 Jun 2026 15:59:50 -0400
ActionableScore: 2
ActionableScore lower bound: 0
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-2026-46268 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46268

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-2026-46268	LOW	CHECK	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-617;CWE-703;CWE-754;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'p2pmem_alloc_mmap() used an inverted VM warning condition after P2PDMA pages changed to an initial refcount of zero. A local caller that can reach the p2pmem mmap path can trigger a false CONFIG_DEBUG_VM warning on the expected zero refcount before the code sets the page count and inserts the page into the VMA. For the CVSS the PR:L is used in the paranoid score because a local process with permission to mmap the exposed p2pmem interface may be enough, although typical deployments restrict this path to administrative users. The issue is not network reachable. Impact is mainly a warning and at worst denial of service if panic_on_warn or similar debug policy turns the warning into a kernel panic.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) 	MAYBE	READ WARNONLY SIMPLEFIX HARDWARE  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	-	-	checked

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

ActionableScore=2
ActionableScoreLower=0

1. ActionableScore
* Conservative score: 0
* Paranoid score: 2
* Final recommended bucket: **Ordinary Moderate / Low-like**::

2. Signal breakdown
* Reliable kernel crash / strong DoS: +1 only in paranoid interpretation. The warning can become a panic if CONFIG_DEBUG_VM and panic_on_warn or similar policy are enabled.
* Local unprivileged trigger: +1 only in paranoid interpretation. This assumes a local process has permission to mmap the exposed p2pmem interface.
* Requires admin/root/CAP level access in typical deployments: -2 for conservative scoring. Access to PCI P2PDMA p2pmem is normally not broadly available to unprivileged users.
* Rare and difficult-to-reach subsystem/configuration: -1 to -2. P2PDMA requires suitable PCI peer-to-peer memory hardware and the visible impact depends on debug warning behavior.
* No generic memory corruption signal. The patch flips a VM_WARN_ON_ONCE_PAGE condition before set_page_count() and vm_insert_page(). It does not show UAF, double-free, OOB write, arbitrary write, or page-cache corruption.

3. Reachability analysis
The path is local and requires reaching p2pmem_alloc_mmap(). In typical systems this requires specialized PCI P2PDMA hardware and privileged or explicitly delegated access to the p2pmem interface. It is not network reachable and not a common default attack surface. Namespaces or containers do not normally make this path available unless the device node or related file interface is intentionally passed through. Realistic exploitation is mainly triggering a false warning, with DoS only if the system is configured to panic on warnings.

4. Severity interpretation
This behaves like a Low-like or ordinary Moderate issue, not an Important-class vulnerability. The theoretical worst case is local DoS through warning-to-panic behavior under debug or strict panic policy. There is no realistic evidence of confidentiality impact, integrity impact, privilege escalation, or memory corruption from the patch context.

5. One-sentence report phrase
An inverted VM warning condition in p2pmem_alloc_mmap() can cause a false CONFIG_DEBUG_VM warning for the expected zero refcount of a newly allocated P2PDMA page, and at worst may cause local DoS on systems configured to panic on warnings.

6. Manual review recommendation
NO MANUAL CHECK NEEDED. The issue is a false warning condition in a specialized PCI/P2PDMA path, with no supported memory corruption or privilege escalation primitive, and can be handled as low-priority unless the environment widely exposes p2pmem mmap with panic_on_warn enabled.

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

Patch: PCI/P2PDMA: Fix p2pmem_alloc_mmap() warning condition [ Upstream
Commit: eb9aa9f8010465d927864f5a35bdc5604b0ff51a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=eb9aa9f8010465d927864f5a35bdc5604b0ff51a

Changed files:
  drivers/pci/p2pdma.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=eb9aa9f8010465d927864f5a35bdc5604b0ff51a

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

The original Linux kernel CVE announcement for CVE-2026-46268 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46268

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: 0
  Paranoid ActionableScore: 2

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).