[CVE-2026-64192][MODERATE 7.0] bpf: Reject BPF_MAP_TYPE_INODE_STORAGE creation if BPF LSM is uninitialized

[CVE-2026-64192][MODERATE 7.0] bpf: Reject BPF_MAP_TYPE_INODE_STORAGE creation if BPF LSM is uninitialized

[AL-KERNEL]

CVE: CVE-2026-64192
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: bpf: Reject BPF_MAP_TYPE_INODE_STORAGE creation if BPF LSM is uninitialized
Commit: c76b8abce575e0c6e4096957220b4515ed847d89
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c76b8abce575e0c6e4096957220b4515ed847d89
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64192
Analysis date: Mon, 20 Jul 2026 13:00:02 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A privileged or delegated BPF user can create BPF inode storage maps while BPF LSM is uninitialized, causing an invalid inode security blob offset that corrupts an RCU callback pointer and can panic the kernel during later cleanup.

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

The original Linux kernel CVE announcement for CVE-2026-64192 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64192

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
======================================================================

CVE-2026-64192	MODERATE	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:H/I:H/A:H';CWE-665;*CWE-787;CWE-824;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'BPF inode storage maps can be created when CONFIG_BPF_LSM is built in but the BPF LSM was not initialized at boot. In that state the inode security blob offset used by bpf_inode is not prepared and points into the reserved rcu_head area of inode i_security. Updating or cleaning an inode storage map can corrupt the rcu_head.func callback pointer and later rcu_do_batch may attempt to execute a NULL or invalid callback, causing a kernel panic. For the CVSS the PR:L is used because a local user or service with delegated BPF permissions can be sufficient in some deployments, even if many default systems restrict this path to privileged users. The issue is not network reachable and requires local code execution plus the affected boot configuration. Impact is at least local denial of service and in the paranoid case may include confidentiality and integrity impact because the bug corrupts security blob memory and a callback pointer, so privilege escalation cannot be ruled out without manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	OOB INIT BPF  KPANIC INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK	NO	NO	checked

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

ActionableScore=5
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 5
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**

## 2. Signal breakdown

Conservative signals:

* Generic memory corruption / security-blob corruption: +2
  The invalid BPF LSM inode blob offset aliases `inode->i_security` into the reserved `struct rcu_head` area and can corrupt `rcu_head.func`.

* Reliable kernel crash / strong DoS: +1
  The commit describes `rcu_do_batch()` later attempting to execute a NULL callback pointer, causing immediate kernel panic.

* Availability impact realistic: +1
  This is not just a WARN or validation failure. The described consequence is a host kernel panic after map cleanup or inode destruction.

* Weak LPE concern: +1
  The corruption affects a security blob area and an RCU callback pointer. The write appears constrained, but the target is control-flow-sensitive enough to require manual review.

* Privileged BPF access / capability-gated path: -1
  The trigger requires creating and updating `BPF_MAP_TYPE_INODE_STORAGE`. In many product configurations this requires privileged BPF access, CAP_BPF, CAP_SYS_ADMIN, or root-controlled policy. I use -1 rather than -2 because reduced-capability service accounts or delegated BPF permissions may still be meaningful PR:L contexts.

Paranoid adjustment:

* Paranoid score keeps the same bug class but treats the callback-pointer corruption as requiring Actionable Moderate handling. No arbitrary code execution is assumed.

## 3. Reachability analysis

The bug is local-only and is not network reachable. A trigger requires local code execution plus the ability to create and update BPF inode storage maps. In typical hardened deployments, unprivileged BPF is disabled and this path is restricted to privileged users or services with BPF-related capabilities.

Namespaces and containers matter if a container root, service account, or reduced-capability workload is granted BPF access without full host-root equivalence. In that case, the issue is more relevant than a pure host-root-only DoS because it can corrupt host kernel state from a delegated privilege boundary.

The affected configuration also requires `CONFIG_BPF_LSM=y` while the BPF LSM is not actually initialized at boot, for example because it is omitted from `lsm=`. This is a configuration precondition, but the downstream failure mode is concrete.

## 4. Severity interpretation

This is stronger than an ordinary Moderate DoS because the patch context shows concrete corruption of `inode->i_security` and the RCU callback pointer, not merely invalid input rejection. Realistic demonstrated impact is kernel panic. Privilege escalation is not demonstrated, and the apparent overwrite is constrained rather than attacker-controlled.

Conservative interpretation: borderline/manual-review Moderate due to privileged BPF gating.
Paranoid interpretation: Actionable Moderate at minimum because callback-pointer corruption inside a security blob can be under-triaged if treated as DoS-only.

## 5. One-sentence report phrase

A privileged or delegated BPF user can create BPF inode storage maps while BPF LSM is uninitialized, causing an invalid inode security blob offset that corrupts an RCU callback pointer and can panic the kernel during later cleanup.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED.

Reason: the issue has a concrete memory-corruption sink involving `inode->i_security` and `rcu_head.func`, with reliable kernel panic and plausible but unproven LPE concern. The privileged BPF gating lowers practical exposure, but it should not be auto-closed without checking product BPF policy and whether reduced-privilege workloads can reach this map type.

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

Patch: bpf: Reject BPF_MAP_TYPE_INODE_STORAGE creation if BPF LSM is uninitialized
Commit: c76b8abce575e0c6e4096957220b4515ed847d89
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=c76b8abce575e0c6e4096957220b4515ed847d89

Commit description:

When CONFIG_BPF_LSM=y is set, BPF inode storage maps
(BPF_MAP_TYPE_INODE_STORAGE) are compiled into the kernel. However,
if the BPF LSM is not explicitly enabled at boot time (e.g. omitted
from the "lsm=" boot parameter), lsm_prepare() is never executed for
the BPF LSM.

Consequently, the BPF inode security blob offset
(bpf_lsm_blob_sizes.lbs_inode) is never initialized and remains at
its default compiled size of 8 bytes instead of being updated to a
valid offset past the reserved struct rcu_head (typically 16 bytes
or more).

When a privileged user creates and updates a BPF_MAP_TYPE_INODE_STORAGE
map, bpf_inode() evaluates inode->i_security + 8. This erroneously
aliases the struct rcu_head.func callback pointer at the beginning
of the inode->i_security blob. During subsequent map element cleanup
or inode destruction, writing NULL to owner_storage clears the queued
RCU callback pointer. When rcu_do_batch() later executes the queued
callback, it attempts an instruction fetch at address 0x0, triggering
an immediate kernel panic.

Fix this by introducing a global bpf_lsm_initialized boolean flag
marked with __ro_after_init. Set this flag to true inside bpf_lsm_init()
when the LSM framework successfully registers the BPF LSM. Gate map
allocation in inode_storage_map_alloc() on this flag, returning
-EOPNOTSUPP if the BPF LSM is in turn uninitialized.

This fail-fast approach prevents userspace from allocating inode
storage maps when the supporting BPF LSM infrastructure is absent,
avoiding zombie map states.

Fixes: 8ea6368 ("bpf: Implement bpf_local_storage for inodes")
Reported-by: oxsignal <awo@kakao.com>
Signed-off-by: Matt Bobrowski <mattbobrowski@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Reviewed-by: Amery Hung <ameryhung@gmail.com>
Link: https://lore.kernel.org/bpf/20260628201103.3624525-1-mattbobrowski@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  include/linux/bpf_lsm.h
  kernel/bpf/bpf_inode_storage.c
  security/bpf/hooks.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=c76b8abce575e0c6e4096957220b4515ed847d89

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

The original Linux kernel CVE announcement for CVE-2026-64192 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64192

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:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
  The Best / paranoid CVSS score: 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: 4
  Paranoid ActionableScore: 5

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).