[CVE-2026-53083][LOW] bpf: Fix RCU stall in bpf_fd_array_map_clear() [ Upstream

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

CVE: CVE-2026-53083
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: bpf: Fix RCU stall in bpf_fd_array_map_clear() [ Upstream
Commit: b1f7158a86f3cbac4d5a32beb55ca0f8027d44cd
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1f7158a86f3cbac4d5a32beb55ca0f8027d44cd
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53083
Analysis date: Wed, 24 Jun 2026 14:25:44 -0400
ActionableScore: 3
ActionableScore lower bound: 1
Actionable bucket: Ordinary Moderate / Low-like, Actionable only with untrusted delegated BPF access
Manual review required: NO

Summary:
A missing cond_resched in bpf_fd_array_map_clear can let a large PROG_ARRAY cleanup monopolize CPU time and trigger RCU stalls, causing local denial of service when the attacker has BPF map control.

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

The original Linux kernel CVE announcement for CVE-2026-53083 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53083

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-2026-53083	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-400;CWE-834;CWE-407;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'bpf_fd_array_map_clear can run for a long time when clearing a large PROG_ARRAY map because each entry deletion may invoke expensive prog_array_map_poke_run work without yielding the CPU. Under load this can produce RCU stalls or soft lockups in the deferred clear workqueue and degrade system responsiveness. For the CVSS the PR:L paranoid value is used because some deployments delegate BPF capabilities or allow local service accounts to create and clear BPF maps, although many default systems require CAP_BPF or CAP_SYS_ADMIN. The issue is not network reachable and requires local BPF map control. Impact is denial of service only through CPU starvation or scheduler latency, with no supported memory corruption, information disclosure, or privilege escalation primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like, Actionable only with untrusted delegated BPF access (with actual score 2)	YES	BPF HARDWARE LINUS  INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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

ActionableScore=3
ActionableScoreLower=1

## 1. ActionableScore

* Conservative score: 1
* Paranoid score: 3
* Final recommended bucket: **Ordinary Moderate / Low-like, Actionable only with untrusted delegated BPF access**

## 2. Signal breakdown

Conservative signals:

* Reliable kernel stall / DoS concern: +1. The loop can run too long while clearing large PROG_ARRAY maps and can trigger RCU stalls or soft lockups.
* Requires admin or BPF capabilities in typical deployments: -2. Creating and managing relevant BPF maps generally requires CAP_BPF, CAP_SYS_ADMIN, or equivalent BPF privileges on modern systems.
* Broad subsystem exposure: +1. BPF is widely deployed, but this specific path still requires BPF map control.

Conservative total is effectively 1 after considering that this is privileged DoS-only behavior.

Paranoid signals:

* Local delegated trigger: +1. Some environments delegate BPF capabilities to local services or constrained users, making PR:L plausible.
* Reliable strong DoS concern: +1. Under load, clearing a large PROG_ARRAY without yielding can cause RCU stalls and system responsiveness degradation.
* Local high-control BPF API: +1. The attacker can influence map size and contents enough to create expensive per-entry cleanup work, but this does not imply memory corruption.

No added signals for LPE, memory corruption, confidentiality, integrity, remote reachability, Dirty-Pipe-like behavior, or lifetime corruption.

## 3. Reachability analysis

The bug is local and requires control over BPF PROG_ARRAY map creation and cleanup. In typical production deployments, unprivileged BPF is disabled and this path requires CAP_BPF, CAP_SYS_ADMIN, or an equivalent privileged service context. Containers usually do not receive these capabilities by default, but some observability, tracing, or networking platforms may delegate BPF privileges to non-root service accounts.

The issue is not network reachable. It is triggered through BPF control-plane activity, not packet processing. Realistic exploitation conditions require the ability to create a large PROG_ARRAY and cause it to be cleared under load.

## 4. Severity interpretation

This behaves like ordinary Moderate or Low-like resource-exhaustion DoS in standard deployments. The patch adds a missing reschedule point and does not indicate UAF, OOB access, refcount misuse, type confusion, arbitrary write, or any privilege-escalation primitive.

Theoretical impact is limited to CPU starvation, RCU stalls, or soft lockups. Realistic impact is availability degradation only. The paranoid score is higher only for environments where untrusted local users or reduced-privilege services are allowed to manage BPF maps.

## 5. One-sentence report phrase

A missing cond_resched in bpf_fd_array_map_clear can let a large PROG_ARRAY cleanup monopolize CPU time and trigger RCU stalls, causing local denial of service when the attacker has BPF map control.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is DoS-only resource consumption with no supported memory corruption, no confidentiality or integrity impact, no remote reachability, and typical privileged BPF requirements. Manual review is only useful if the target environment delegates BPF map creation to untrusted users or service accounts.

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

Patch: bpf: Fix RCU stall in bpf_fd_array_map_clear() [ Upstream
Commit: b1f7158a86f3cbac4d5a32beb55ca0f8027d44cd
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1f7158a86f3cbac4d5a32beb55ca0f8027d44cd

Changed files:
  kernel/kcov.c
  kernel/bpf/arraymap.c
  kernel/workqueue.c
  kernel/kthread.c
  arch/x86/kernel/process.c
  arch/x86/entry/entry_64.S

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=b1f7158a86f3cbac4d5a32beb55ca0f8027d44cd

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

The original Linux kernel CVE announcement for CVE-2026-53083 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53083

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: 1
  Paranoid ActionableScore: 3

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).