[CVE-2026-63822][MODERATE 7.0] wifi: ath11k: fix warning when unbinding

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

CVE: CVE-2026-63822
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: wifi: ath11k: fix warning when unbinding
Commit: e569a5cb401a267168621aa9a1e7f07fcc9612c3
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e569a5cb401a267168621aa9a1e7f07fcc9612c3
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63822
Analysis date: Sun, 19 Jul 2026 10:00:11 -0400
ActionableScore: 5
ActionableScore lower bound: 3
Actionable bucket: Actionable Moderate at minimum
Manual review required: YES

Summary:
A double free in the ath11k driver cleanup path can occur after firmware or MSI related initialization failure when tx_status is freed once during error cleanup and again during later device unbind, causing a local privileged kernel warning or crash and requiring manual review due to memory corruption potential.

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

The original Linux kernel CVE announcement for CVE-2026-63822 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63822

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
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CVE-2026-63822	MODERATE	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-415;*CWE-664;CWE-703;CWE-415;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A double free can occur in the ath11k cleanup path because ath11k_dp_free() frees tx_status but leaves the pointer non NULL. If firmware or MSI related initialization fails, the buffer can be released during error cleanup and then released again during a later device unbind. The reliable impact is local denial of service via kernel warning or crash, especially with panic_on_warn or allocator hardening enabled. Because this is a kernel double free, worst case impact may include memory corruption and possible privilege escalation if an attacker can control the timing and heap state. For the CVSS the PR:L is used for the paranoid score because some deployments may delegate driver bind or unbind, hotplug, or device management to a local service or reduced admin role rather than full host administration. The issue is not network reachable and does not appear triggerable by normal Wi-Fi traffic alone.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4)	YES	REMOTE DANGER SIMPLEFIX NETWORK HARDWARE LINUS  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=5
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 5
* Final recommended bucket: **Actionable Moderate at minimum**::

## 2. Signal breakdown

Triggered signals:

* Generic memory corruption: +2
  The bug is explicitly a double free of `dp->tx_ring[i].tx_status`.

* Real lifetime corruption: +1
  The same allocation can be freed during an initialization error path and then freed again during later device unbind.

* Reliable kernel crash / strong DoS: +1
  The commit shows a reproducible SLUB warning in `free_large_kmalloc()` during `ath11k_pci_remove()`. With `panic_on_warn` or allocator hardening this can become a practical kernel crash.

* Privileged kernel/device-management memory corruption path: +1
  The corruption occurs in a trusted Wi-Fi driver cleanup path during firmware/MSI related initialization failure and PCI device removal.

* Weak LPE concern, paranoid only: +1
  Double free is a memory corruption class that can sometimes become exploitable if heap state and timing are controllable. However, this patch does not show attacker-controlled reclaim, object replacement, callback control, or an arbitrary write primitive.

Subtracted signals:

* Requires admin/root/CAP_* in typical deployments: -2
  Reliable triggering normally requires driver unbind/remove, PCI device management, module handling, or equivalent administrative control.

* Corruption primitive constrained or no demonstrated attacker-controlled payload: -1
  The patch shows double free and warning/crash behavior, but not controlled overwrite, controlled target selection, or demonstrated privilege escalation.

Net:

* Conservative: 2 + 1 + 1 + 1 - 2 - 1 = 2 to 3 range. I use 3 because the double free is explicit and reproducible.
* Paranoid: conservative 3 + weak LPE concern 1 + device/firmware-mediated uncertainty 1 = 5.

## 3. Reachability analysis

The realistic trigger is local and privileged. An attacker typically needs the ability to cause ath11k initialization failure and then unbind or remove the PCI device or driver. Normal Wi-Fi network traffic does not appear to reach this cleanup path directly.

Namespaces and containers usually do not make this reachable unless device management, driver binding, or PCI/sysfs control is delegated into the environment. A reduced-capability service or container root with device-management access could justify the paranoid PR:L interpretation, but ordinary unprivileged users should not be able to trigger this in typical deployments.

The affected path requires ath11k hardware or a VM/device setup where the initialization failure is reproducible. The commit notes that it is always reproducible from a VM because MSI addressing initialization fails, which improves reliability in that environment but does not make it remotely reachable.

Call-site confidence: high. The commit includes the relevant cleanup function, the exact double free prevention, and the observed call trace through `ath11k_dp_free`, `ath11k_core_deinit`, and `ath11k_pci_remove`.

## 4. Severity interpretation

This is not an ordinary low-risk warning fix because the underlying bug class is double free in kernel memory management. The realistic impact is local privileged DoS through warning or crash during driver cleanup. Theoretical memory corruption and privilege escalation are possible only in a paranoid interpretation, because the patch does not show controlled reclaim, controlled replacement, or a write primitive.

Overall this behaves like an Actionable Moderate issue, not a clear Important-class vulnerability. It should not be auto-closed without review because double free bugs are historically under-triaged when only the visible symptom is a warning.

## 5. One-sentence report phrase

A double free in the ath11k driver cleanup path can occur after firmware or MSI related initialization failure when tx_status is freed once during error cleanup and again during later device unbind, causing a local privileged kernel warning or crash and requiring manual review due to memory corruption potential.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: explicit kernel double free. Practical exploitation appears constrained and privileged, but memory lifetime corruption in a driver cleanup path warrants manual review before closure.

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

Patch: wifi: ath11k: fix warning when unbinding
Commit: e569a5cb401a267168621aa9a1e7f07fcc9612c3
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=e569a5cb401a267168621aa9a1e7f07fcc9612c3

Commit description:

If there is an error during some initialization related to firmware,
the buffers dp->tx_ring[i].tx_status are released.
However this is released again when the device is unbinded (ath11k_pci),
and we get:
WARNING: CPU: 0 PID: 6231 at mm/slub.c:4368 free_large_kmalloc+0x57/0x90
Call Trace:
free_large_kmalloc
ath11k_dp_free
ath11k_core_deinit
ath11k_pci_remove
...

The issue is always reproducible from a VM because the MSI addressing
initialization is failing.

In order to fix the issue, just set the buffers to NULL after releasing in
order to avoid the double free.

Fixes: d5c6515 ("ath11k: driver for Qualcomm IEEE 802.11ax devices")
Cc: stable@vger.kernel.org
Signed-off-by: Jose Ignacio Tornos Martinez <jtornosm@redhat.com>
Reviewed-by: Baochen Qiang <baochen.qiang@oss.qualcomm.com>
Reviewed-by: Rameshkumar Sundaram <rameshkumar.sundaram@oss.qualcomm.com>
Link: https://patch.msgid.link/20260420110130.509670-1-jtornosm@redhat.com
Signed-off-by: Jeff Johnson <jeff.johnson@oss.qualcomm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  mm/slub.c
  drivers/net/wireless/ath/ath11k/dp.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=e569a5cb401a267168621aa9a1e7f07fcc9612c3

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

The original Linux kernel CVE announcement for CVE-2026-63822 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63822

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: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: 3
  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: NO
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).