[CVE-2026-80737][MODERATE 7.0] serial: amba-pl011: synchronize DMA teardown [ Upstream

[CVE-2026-80737][MODERATE 7.0] serial: amba-pl011: synchronize DMA teardown [ Upstream

[AL-KERNEL]

CVE: CVE-2026-80737
Priority: MODERATE 7.0
AL-KERNEL base severity: MODERATE
KPANIC flag: YES
Patch: serial: amba-pl011: synchronize DMA teardown [ Upstream
Commit: a38fae9d212e2d3ed5e9ec0ef773f8c0a27fb76e
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a38fae9d212e2d3ed5e9ec0ef773f8c0a27fb76e
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80737
Analysis date: Thu, 03 Sep 2026 05:30:35 -0400
ActionableScore: 7
ActionableScore lower bound: 4
Actionable bucket: Strong Important candidate / Actionable Moderate at minimum
Manual review required: YES

Summary:
A race in ARM PL011 DMA teardown can allow a TX DMA callback or RX poll timer to access DMA buffers after they are freed, causing a kernel use after free with realistic local DoS impact and possible memory corruption concerns on systems using PL011 DMA.

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ABOUT THIS REPORT
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The original Linux kernel CVE announcement for CVE-2026-80737 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80737

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-2026-80737	MODERATE	https://www.kernelcve.org/list/?q=CVE-2026-80737 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-362;CWE-667;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'A use after free can occur in the ARM PL011 serial driver during DMA shutdown because dmaengine_terminate_all does not wait for a running DMA callback. The TX callback may still access the TX buffer after it has been freed, and the RX poll timer may read RX DMA buffers without the port lock while teardown is freeing them. For the CVSS the PR:L is used because triggering normally requires a local process with access to the affected serial port or another local path that can drive UART DMA shutdown. The issue is not network reachable and depends on systems using PL011 with DMA enabled. Impact is at least local denial of service via kernel crash. In the paranoid interpretation, the explicit use after free makes confidentiality and integrity impact plausible enough for manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 6)	YES	PRINTF-TTY SIMPLEFIX DMAorINTERRUPT TIMER LINUS KPANIC MEMORY  KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFDH	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=7
ActionableScoreLower=4

## 1. ActionableScore

* Conservative score: 4
* Paranoid score: 7
* Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**::

## 2. Signal breakdown

Conservative signals:

* Local unprivileged or low privileged trigger: +1. A local process with access to the affected PL011 serial device may be able to drive open close or shutdown paths.
* Memory corruption, strong corruption primitive: +2. The commit explicitly describes a use after free where a TX DMA callback can access a freed TX buffer.
* Real lifetime corruption: +1. This is an async teardown lifetime mismatch involving DMA callbacks and an RX timer.
* Reliable kernel crash / strong DoS: +1. Kernel UAF in DMA teardown is a realistic crash class.
* Hard or unreliable race / special timing required: -1. Triggering depends on teardown racing with a running DMA callback or timer.
* Rare or configuration dependent path: -1. Requires ARM PL011 with DMA enabled and relevant serial activity.
* Privileged kernel/device-management memory corruption path: +1. The bug is in DMA adjacent serial driver teardown.

Conservative total: 4

Paranoid additional signals:

* Weak LPE concern: +1. The UAF involves stale async callback or timer access after buffer free, but no controlled reclaim or arbitrary write is demonstrated.
* Confidentiality impact plausible: +1. In a paranoid interpretation, stale reads from freed RX buffers may expose limited kernel data depending on reuse.
* Integrity impact plausible: +1. In a paranoid interpretation, stale callback activity on freed DMA buffers may corrupt reused kernel memory.

Paranoid total: 7

## 3. Reachability analysis

The issue is local and not network reachable. The practical trigger requires a system using the ARM PL011 serial driver with DMA enabled, and a local path that can cause PL011 DMA shutdown while TX DMA callbacks or RX poll timers are still active. Access may be limited to users with permission to the serial device, or to service or container contexts that are allowed to interact with that UART. It does not normally require full host root if the affected tty device is exposed to a lower privileged process, but reliable triggering is timing dependent and platform specific.

Namespaces do not automatically make this broadly reachable. If the physical serial device is passed into a container or exposed to a reduced privilege service, the practical PR can remain low. If only host root can access or reconfigure the port, the operational risk is lower.

Call-site confidence: medium. The patch shows the vulnerable teardown function and the unsafe ordering, but not all callers that reach `pl011_dma_shutdown()`.

## 4. Severity interpretation

This is more serious than an ordinary Moderate cleanup bug because the patch directly fixes a use after free caused by asynchronous DMA callback and timer lifetime rules. Realistically, the most likely impact is local denial of service through kernel crash. Theoretical privilege escalation is not demonstrated, but the explicit UAF in kernel memory is sufficient to keep this out of auto-close handling and justify manual review.

## 5. One-sentence report phrase

A race in ARM PL011 DMA teardown can allow a TX DMA callback or RX poll timer to access DMA buffers after they are freed, causing a kernel use after free with realistic local DoS impact and possible memory corruption concerns on systems using PL011 DMA.

## 6. Manual review recommendation

MANUAL CHECK REQUIRED

Reason: the patch explicitly describes post-free access by asynchronous DMA callback and timer paths. The realistic impact is likely local DoS, but the kernel UAF and DMA teardown context make the issue important enough for manual review.

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

Patch: serial: amba-pl011: synchronize DMA teardown [ Upstream
Commit: a38fae9d212e2d3ed5e9ec0ef773f8c0a27fb76e
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a38fae9d212e2d3ed5e9ec0ef773f8c0a27fb76e

Changed files:
  drivers/tty/serial/amba-pl011.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=a38fae9d212e2d3ed5e9ec0ef773f8c0a27fb76e

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

The original Linux kernel CVE announcement for CVE-2026-80737 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80737

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: 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).