[CVE-2026-81008][MODERATE 7.0] interconnect: Fix use after free in icc_get() and of_icc_get_by_index()

[CVE-2026-81008][MODERATE 7.0] interconnect: Fix use after free in icc_get() and of_icc_get_by_index()

[AL-KERNEL]

CVE: CVE-2026-81008
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: interconnect: Fix use after free in icc_get() and of_icc_get_by_index()
Commit: a4e9aa7907ade87d1d96853d14e05dcf682f8363
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a4e9aa7907ade87d1d96853d14e05dcf682f8363
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-81008
Analysis date: Sat, 12 Sep 2026 01:26:18 -0400
ActionableScore: 5
ActionableScore lower bound: 4
Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review
Manual review required: YES

Summary:
No one-sentence report phrase was found.

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

The original Linux kernel CVE announcement for CVE-2026-81008 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-81008

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.

======================================================================
AL-KERNEL CLASSIFICATION RESULT
======================================================================

CVE-2026-81008	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-81008 CHECK WITH IMPACT FROM ORIG NN MODERATE	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-416;*CWE-672;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7';DESCR 'An interconnect path allocation error can leave dangling hlist entries because icc_get and of_icc_get_by_index free the path object directly after kasprintf failure even though path_init has already linked path requests into node request lists. A later icc_get or icc_set_bw can traverse or modify those stale list entries and trigger a slab use-after-free with a write to freed memory. For the CVSS the PR:L is used for the paranoid score because a local actor with access to debugfs fault injection delegated test interfaces or similar local control paths may be able to trigger the affected interconnect path without full host administration in some deployments. The issue is not network reachable and requires local execution or local control of a kernel facing test or device management path. Impact is at least local denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to kernel memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 5)	YES	LOCK DEADLOCK DANGER NOMEMCHK ERRORPATH UAF HARDWARE DEBUGFS LINUS KPANIC 	YES	NO	checked

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

ActionableScore=5
ActionableScoreLower=4
PrimitiveClass=CLASS_B
RealUAF=YES
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=YES
ManualReview=REQUIRED
AutoDowngradeAllowed=NO

1. ActionableScore

* Raw conservative score: 4
* Conservative score: 4
* Raw paranoid score: 5
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**::

No floor or cap changed the conservative score. No floor or cap changed the paranoid score.

2. Signal breakdown

Conservative signals:

* +2 Real UAF / lifetime violation. `path_init()` links requests into interconnect node `req_list` via `hlist_add_head()`, but the error path uses `kfree(path)` instead of the proper teardown. This leaves dangling hlist entries.
* +1 Reliable kernel crash / strong DoS. KASAN reports `slab-use-after-free` and the bug can lead to kernel fault or crash when the corrupted list is later traversed or modified.
* +1 Active list/object corruption beyond a shallow NULL dereference. A subsequent `icc_get()` or `icc_set_bw()` can traverse or modify the stale hlist entries, and the supplied KASAN trace shows a write of size 8 to freed memory.
* 0 Local unprivileged trigger not awarded. Reproduction is described via debugfs, but the supplied evidence does not prove ordinary unprivileged reachability.
* 0 Strong LPE leverage not awarded. Controlled reclaim, attacker-shaped replacement object, arbitrary write, callback control, or credential manipulation is not demonstrated.
* 0 Confidentiality and integrity not awarded as separate signals. The UAF write is real, but no concrete disclosure or unauthorized modification of security-sensitive state is established.
* 0 Extra Availability not awarded. The same crash is already counted once.

Paranoid additional signal:

* +1 Unresolved post-free active hlist mutation. The stale object is not fixed passive storage. It remains linked into active kernel lists and later operations may write through list pointers in freed storage. This is stronger than crash-only stale dereference, but still not enough for CLASS_A without controlled reclaim or directed corruption.

Non-awarded repeated-release/refcount checks:

* First release can end lifetime: yes, direct `kfree(path)` frees the path object.
* Exact same reference survives: no exact surviving local reference is shown, but embedded hlist entries remain reachable from node request lists.
* Second operation is a real lifetime/refcount mutation: no, the later operation is list traversal or list modification, not a second `put` or refcount decrement on the exact same object.
* Concrete repeated release/refcount +1 awarded: no.
* Paranoid repeated-refcount leverage +1 awarded: no.
* FLOOR 5 for repeated release/refcount applied: no.

3. Reachability analysis

The demonstrated reproducer path uses debugfs via `icc_get_set`, and debugfs access is commonly restricted, but the supplied material does not positively establish that host-admin-equivalent privilege is required for every possible affected interconnect caller. Therefore `HostAdminRequired=UNKNOWN`, not `YES`.

The issue is local, not network reachable. There is no evidence that packets, remote storage traffic, or firmware input directly reaches this path.

Namespace-scoped privilege is not established. No user namespace, network namespace, or namespace-scoped capability chain is shown.

The practical trigger requires causing `kasprintf()` allocation failure after `path_init()` has already linked the path requests. This may require fault injection, memory pressure, or a privileged test/control path. The error path is ordered rather than a hard race, so no race penalty is applied.

No special rare hardware penalty is applied. Interconnect is platform/device dependent, but the bug class is in generic interconnect core lifetime handling, and the supplied evidence does not prove a rare physical-only requirement.

4. Primitive and severity interpretation

The exact primitive is a real slab use-after-free caused by freeing `struct icc_path` while its embedded requests remain linked into interconnect node hlist structures.

This is an active structured-object lifetime bug, not fixed stale storage. The stale hlist entries can be reached by later `icc_get()` or `icc_set_bw()` and may be traversed or modified.

The demonstrated consequence is kernel memory corruption with KASAN-detected UAF and likely local DoS. The speculative consequence is privilege escalation or broader C/I impact if an attacker can combine the dangling hlist entry with useful heap reuse or list manipulation, but that stronger chain is not demonstrated.

PrimitiveClass is CLASS_B. The patch establishes a real UAF and post-free list mutation, but not controlled reclaim, arbitrary read/write, callback hijack, refcount takeover, or demonstrated LPE.

ImportantCandidate is YES because the issue is a concrete kernel UAF with active list corruption and unresolved exploitation leverage beyond a simple NULL dereference. Manual review is required to determine whether the freed `icc_path` storage can be reclaimed or shaped in a useful way.

AutoDowngradeAllowed is NO because automatically closing this as ordinary crash-only DoS would lose a real active-object UAF with a write to freed memory and unresolved post-lifetime corruption behavior.

Likely operational severity is Actionable Moderate, with Strong Important candidacy depending on whether below-host-admin triggering and useful reclaim or post-free field control can be established.

5. One-sentence report phrase

An interconnect allocation error can leave freed `icc_path` request entries linked in active node lists, allowing later `icc_get()` or `icc_set_bw()` operations to trigger a slab use-after-free and post-free list modification, causing local DoS and requiring manual review for possible stronger memory-corruption impact.

6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: real UAF is established, the stale object remains in active hlist structures, and later operations can modify freed memory. Controlled exploitation is not proven, but automatic downgrade would be unsafe.

7. Call-site confidence

Call-site confidence: high

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

Patch: interconnect: Fix use after free in icc_get() and of_icc_get_by_index()
Commit: a4e9aa7907ade87d1d96853d14e05dcf682f8363
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a4e9aa7907ade87d1d96853d14e05dcf682f8363

Commit description:

In of_icc_get_by_index() and icc_get(), if the dynamic allocation for
path->name fails via kasprintf(), the error handling path directly
calls kfree(path) to free the path object and returns an error.

However, prior to this point, path_find() calls path_init(), which
already links the path's requests into the req_list of the respective
interconnect nodes via hlist_add_head(). Directly invoking kfree(path)
leaves dangling pointers in the hlist. A subsequent call to icc_get()
or icc_set_bw() will traverse or modify these corrupted lists, triggering
a slab use afterfree.

KASAN report showing the vulnerability when reproducing via debugfs:

  BUG: KASAN: slab-use-after-free in path_find+0x6f8/0xcfc
  Write of size 8 at addr fff000000d43f748 by task sh/1
  ...
  Call trace:
   kasan_report+0xac/0xfc
   path_find+0x6f8/0xcfc
   icc_get+0x148/0x380
   icc_get_set+0xf8/0x2d0
  ...
  Freed by task 1:
   kfree+0x1a0/0x4a4
   icc_get+0x2cc/0x380
   icc_get_set+0xf8/0x2d0

Fix this by replacing kfree(path) with the proper teardown function,
icc_put(path), which safely removes the requests from the req_list using
hlist_del() and drops the provider usage references before freeing the
memory.

Additionally, in icc_get(), ensure that the icc_lock mutex is released
prior to calling icc_put(path) to avoid a deadlock, as icc_put()
internally acquires the same lock.

Fixes: 3791163 ("interconnect: Handle memory allocation errors")
Cc: stable@vger.kernel.org
Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Link: https://patch.msgid.link/20260416190840.1753468-1-visitorckw@gmail.com
Signed-off-by: Georgi Djakov <djakov@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/interconnect/core.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=a4e9aa7907ade87d1d96853d14e05dcf682f8363

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

The original Linux kernel CVE announcement for CVE-2026-81008 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-81008

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:L/I:L/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).