[CVE-2026-64352][LOW] bpf: Allow LPM map access from sleepable BPF programs [ Upstream

[CVE-2026-64352][LOW] bpf: Allow LPM map access from sleepable BPF programs [ Upstream

[AL-KERNEL]

CVE: CVE-2026-64352
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: bpf: Allow LPM map access from sleepable BPF programs [ Upstream
Commit: f0967d4f1ba4323a3cb7dc8fdba74dd3a8caaf04
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f0967d4f1ba4323a3cb7dc8fdba74dd3a8caaf04
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64352
Analysis date: Sat, 25 Jul 2026 10:07:10 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like. Auto-close candidate
Manual review required: NO

Summary:
A sleepable BPF program accessing an LPM trie can trigger lockdep suspicious RCU warnings because lpm_trie used annotations that did not recognize Tasks Trace RCU, but the issue is described as lockdep-only with no UAF and practical impact is limited to warning spam or debug-kernel DoS.

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

The original Linux kernel CVE announcement for CVE-2026-64352 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64352

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-2026-64352	LOW	CHECK WITH IMPACT FROM ORIG NN 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-667;CWE-703;CWE-662;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'Sleepable BPF programs can access an LPM trie while holding only Tasks Trace RCU, but lpm_trie used RCU checks that accepted classic or BH RCU contexts only. On debug kernels this can trigger suspicious RCU usage warnings when a sleepable BPF LSM hook touches an LPM map. The issue is described as lockdep only and the source context does not indicate a real UAF because Tasks Trace RCU still serializes against the trie reclaim path. For the CVSS the PR:L is used for the higher sensitivity case because a local user may trigger an already installed sleepable BPF LSM hook, while loading such a program normally requires administrative BPF privileges. The issue is not network reachable by itself. Impact is denial of service at most through warning spam or kernel panic only if panic_on_warn or similar debug policy is enabled.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like. Auto-close candidate (with actual score 1)	YES	LOCK BPF UAF LINUS 	NO	NO	checked

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

ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

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

## 2. Signal breakdown

Conservative signals:

* Requires admin/root/CAP_* in typical deployments: -2. Loading or attaching the relevant sleepable BPF LSM program normally requires privileged BPF capabilities or root-controlled configuration.
* Legacy / non-default execution mode: -1. The described impact is lockdep-only on debug kernels, with practical crash relevance mainly if panic_on_warn or similar policy is enabled.
* No generic memory corruption: +0. The commit explicitly states no UAF, and Tasks Trace RCU still serializes against the trie reclaim path.
* No privilege escalation plausible: +0. No reclaim, stale object reuse, callback control, type confusion, write primitive, or refcount abuse is shown.
* No reliable kernel crash / strong DoS: +0. Warning spam is possible, but a production host-wide crash is not demonstrated.

Paranoid-only signals:

* Local unprivileged trigger: +1. If an administrator has already installed a sleepable BPF LSM program that touches an LPM trie, a local user may trigger the hook through ordinary syscalls such as connect.
* Availability impact realistic: +1 only in debug or panic_on_warn style configurations, due to warning spam or warning-induced panic.
* Non-default/debug condition: -1. The observed failure mode depends on lockdep/debug warning behavior.

Call-site confidence: high. The relevant lookup, update, and delete paths plus the warning stack are present in the input.

## 3. Reachability analysis

The bug is not remotely reachable by itself. It requires a sleepable BPF program that accesses an LPM trie, and such programs are normally loaded by privileged users with BPF-related capabilities or root. A local unprivileged user may only be able to trigger the warning indirectly if such a BPF LSM hook is already installed and reachable from ordinary syscalls. Namespaces or containers do not materially lower the requirement unless the evaluated product explicitly delegates BPF loading or LSM attachment, which is uncommon and usually disabled.

## 4. Severity interpretation

This behaves like a Low-like or ordinary Moderate issue, not an Actionable Moderate and not an Important candidate. Theoretical RCU/lifetime concern is addressed by the patch, but the commit explicitly says this is lockdep-only and no UAF exists because Tasks Trace RCU protects the reclaim path. Realistic impact is warning spam on debug kernels, with possible DoS only under panic_on_warn or similar non-default policy.

## 5. One-sentence report phrase

A sleepable BPF program accessing an LPM trie can trigger lockdep suspicious RCU warnings because lpm_trie used annotations that did not recognize Tasks Trace RCU, but the issue is described as lockdep-only with no UAF and practical impact is limited to warning spam or debug-kernel DoS.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This can be auto-closed for practical triage unless the target product enables unprivileged BPF loading or runs production kernels with panic_on_warn and deployed sleepable BPF LSM programs using LPM trie maps.

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

Patch: bpf: Allow LPM map access from sleepable BPF programs [ Upstream
Commit: f0967d4f1ba4323a3cb7dc8fdba74dd3a8caaf04
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=f0967d4f1ba4323a3cb7dc8fdba74dd3a8caaf04

Changed files:
  kernel/bpf/lpm_trie.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=f0967d4f1ba4323a3cb7dc8fdba74dd3a8caaf04

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

The original Linux kernel CVE announcement for CVE-2026-64352 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64352

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:L
  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: 0
  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).