[CVE-2026-68192][MODERATE 7.0] wifi: brcmfmac: make release_scratchbuffers idempotent

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

CVE: CVE-2026-68192
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: wifi: brcmfmac: make release_scratchbuffers idempotent
Commit: b7d1d8cb1bdca56aecebacd2896615da0acc126a
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b7d1d8cb1bdca56aecebacd2896615da0acc126a
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68192
Analysis date: Mon, 10 Aug 2026 16:09:27 -0400
ActionableScore: 7
ActionableScore lower bound: 3
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
brcmfmac PCIe scratch DMA buffers may be freed twice when firmware crash reset teardown is followed by device removal, causing a kernel double-free condition that is most likely a privileged local DoS but may warrant Important-level review due to possible allocator corruption.

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

The original Linux kernel CVE announcement for CVE-2026-68192 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68192

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-2026-68192	MODERATE	CHECK WITH IMPACT FROM ORIG NN IMPORTANT	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-763;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'brcmfmac PCIe scratch DMA buffers can be freed twice because brcmf_pcie_release_scratchbuffers() releases shared scratch and shared ringupd but previously left the saved pointers non NULL. A firmware crash reset can run brcmf_pcie_reset and release the buffers, and a later brcmf_pcie_remove path can release the same DMA allocations again. This is a kernel double free candidate and can cause a crash or allocator state corruption depending on timing and DMA allocator behavior. For the CVSS the PR:L is used in the paranoid score because reliable triggering may be possible from a local user or delegated network management context that can force WiFi reset and teardown paths, while the typical administrative remove path is PR:H. The issue is not directly reachable from the IP network, but adjacent WiFi activity may be relevant if it can induce firmware crash on affected hardware. Impact is at least denial of service and worst case may include confidentiality or integrity impact due to kernel memory corruption, so this should be manually reviewed.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5)	YES	REMOTE DANGER UAF NETWORK DMAorINTERRUPT KERNEL_PANIC_PLUS_UAF KPANIC MEMORY  KPANIC DECREASED_TO_MODERATE70_BASED_ON_ACTIONABLESCORELOWERTHAN7	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Memory corruption, Strong corruption primitive: +2. The patch prevents a second dma_free_coherent() on the same saved DMA buffer pointers, which is a double-free class bug.
* Real lifetime corruption: +1. The issue is caused by stale non-NULL pointers surviving after the first release.
* Reliable kernel crash / strong DoS: +1. A second DMA free can plausibly crash or corrupt allocator state.
* Privileged kernel/device-management memory corruption path: +1. The bug is in PCIe WiFi driver teardown and DMA coherent buffer management.
* Requires admin/root/CAP_* in typical deployments: -2. The documented second call path involves device removal or driver teardown, which is normally administrative.
* Hard or special condition required: -1. The problematic sequence requires firmware crash reset teardown before later remove teardown.

Paranoid additional interpretation:

* Firmware-mediated external influence: +1. The first release path is tied to firmware crash reset, and WiFi firmware state may be influenced by adjacent wireless activity in some environments.
* Local unprivileged or delegated management trigger concern: +1. In desktop, service-managed, or delegated network-management setups, a non-root user may influence WiFi reset/recovery conditions even if final remove is normally privileged.
* Weak LPE concern: +1. Double-free in kernel DMA allocation state is a memory corruption class where allocator corruption could theoretically affect confidentiality or integrity, although no controlled reclaim or overwrite primitive is demonstrated.

Paranoid deductions:

* Corruption primitive constrained or no attacker-controlled payload: -1. The freed object is a fixed DMA coherent allocation and the patch does not show attacker-chosen overwrite data or target selection.
* Special sequence required: -1. Exploitation depends on reset teardown followed by removal teardown.

## 3. Reachability analysis

The documented reliable trigger is local and privileged in normal deployments, because brcmf_pcie_remove() and driver or device teardown are typically controlled by root or a privileged device-management stack. The first release can occur through brcmf_pcie_reset() after a firmware crash, which creates a possible firmware-mediated exposure path, but the patch does not prove that an unauthenticated remote WiFi attacker can reliably force the full double-free sequence.

Namespaces do not usually make PCIe WiFi device removal directly available to unprivileged containers. However, reduced-capability service accounts, desktop network managers, or delegated device-control environments may lower the practical privilege boundary compared with full host root. The affected path is hardware and driver specific, not a default core networking path, but brcmfmac is common enough on some systems that this should not be dismissed as purely theoretical.

Call-site confidence: medium. The commit message explicitly names both brcmf_pcie_reset() and brcmf_pcie_remove() as callers, but the full reset-work lifetime and remove sequencing are not included in the provided diff.

## 4. Severity interpretation

This is not an ordinary resource leak or validation-only fix. It is a double-free candidate in a kernel DMA coherent allocation release path. The conservative view is a privileged local DoS with special sequencing, which lands in borderline Moderate territory.

The paranoid view is stronger because double-free is a real memory lifetime corruption primitive, and the first release path is tied to firmware crash reset. There is not enough evidence to claim a strong LPE primitive such as controlled reclaim, arbitrary write, callback hijack, or type confusion. However, because the bug class is kernel double-free in a device DMA path, it should be treated as Actionable Moderate at minimum and an Important candidate for manual review.

## 5. One-sentence report phrase

brcmfmac PCIe scratch DMA buffers may be freed twice when firmware crash reset teardown is followed by device removal, causing a kernel double-free condition that is most likely a privileged local DoS but may warrant Important-level review due to possible allocator corruption.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: this is a concrete double-free in a kernel DMA allocation path, not just a warning or cleanup issue. The realistic trigger appears constrained and often privileged, but the memory corruption class and firmware-reset involvement make auto-closing unsafe.

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

Patch: wifi: brcmfmac: make release_scratchbuffers idempotent
Commit: b7d1d8cb1bdca56aecebacd2896615da0acc126a
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b7d1d8cb1bdca56aecebacd2896615da0acc126a

Commit description:

brcmf_pcie_release_scratchbuffers() frees the shared.scratch and
shared.ringupd DMA buffers with dma_free_coherent() but does not clear
the pointers afterwards, unlike the sibling release_ringbuffers() which
NULLs commonrings/flowrings/idxbuf on release.

Both the bus_reset .reset callback (brcmf_pcie_reset) and
brcmf_pcie_remove() call release_scratchbuffers.  When reset teardown
has run before removal, remove's own teardown would call
dma_free_coherent() a second time on the already-freed DMA allocation.

NULL the pointers after free, matching release_ringbuffers(), so a later
release observes that the allocation has already been released.  This
patch makes repeated sequential release safe; the reset-work lifetime is
handled separately by the following patch.

This issue was found by an in-house static analysis tool.

Fixes: 4684997 ("brcmfmac: reset PCIe bus on a firmware crash")
Cc: stable@vger.kernel.org
Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>
Assisted-by: Codex:gpt-5.6
Acked-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Link: https://patch.msgid.link/20260718024353.3147201-2-fanwu01@zju.edu.cn
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/wireless/broadcom/brcm80211/brcmfmac/pcie.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=b7d1d8cb1bdca56aecebacd2896615da0acc126a

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

The original Linux kernel CVE announcement for CVE-2026-68192 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68192

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: 7

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).