[CVE-2026-74622][LOW] net: atlantic: free RX pages of consumed but not refilled buffers

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

CVE: CVE-2026-74622
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: net: atlantic: free RX pages of consumed but not refilled buffers
Commit: 1e58b0bab40dcbdfc04acaba6a221d40801c3770
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1e58b0bab40dcbdfc04acaba6a221d40801c3770
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74622
Analysis date: Sat, 22 Aug 2026 17:22:08 -0400
ActionableScore: 1
ActionableScore lower bound: 0
Actionable bucket: Ordinary Moderate / Low-like
Manual review required: NO

Summary:
The atlantic driver could leak RX pages and DMA mappings on interface down because consumed but not refilled RX buffers were skipped during deinit, allowing a privileged local actor with network-device control to cause resource-exhaustion DoS through repeated down/up cycles.

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

The original Linux kernel CVE announcement for CVE-2026-74622 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74622

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: LOW
Manual review required: NO

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-2026-74622	LOW	CHECK WITH IMPACT FROM ORIG NN LOW	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H';*CWE-401;*CWE-772;**CWE-400;**CWE-476;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'The atlantic driver can leak RX pages and DMA mappings when an interface is brought down because aq_ring_rx_deinit only walked the posted hardware range while consumed but not yet refilled buffers could remain in the complementary ring gap. Repeated interface down and up cycles after RX activity may gradually exhaust memory or DMA mapping resources and cause denial of service. For the CVSS the PR:L is used in the paranoid score because some deployments delegate network administration to a container root or service account rather than full host root. The issue is not directly network reachable because packet traffic alone does not deinitialize the ring. Impact is resource exhaustion and availability loss only, with no evidence of an arbitrary write, UAF primitive, or privilege escalation path.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1)	YES	REMOTE LEAK NETWORK DMAorINTERRUPT HARDWARE LINUS  DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3	NO	NO	checked

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ACTIONABLESCORE ANALYSIS
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ActionableScore=1
ActionableScoreLower=0

## 1. ActionableScore

* Conservative score: 0
* Paranoid score: 1
* Final recommended bucket: **Ordinary Moderate / Low-like**::

## 2. Signal breakdown

Conservative signals:

* Availability impact realistic: +1
  Repeated interface down events can leak RX pages and DMA mappings, eventually causing resource exhaustion.
* Requires admin/root/CAP_NET_ADMIN in typical deployments: -2
  Reliable triggering requires bringing the interface down or otherwise controlling the NIC lifecycle, which is normally administrative.

Conservative total is clamped to 0.

Paranoid signals:

* Reliable resource-exhaustion DoS concern: +1
  If an attacker can repeatedly force down/up cycles after RX activity, leaked pages and DMA mappings may accumulate.
* Requires privileged network-device control: -1
  In delegated environments, container root or a service account with network administration rights may be less than full host root, so the full -2 penalty is softened.

Paranoid total: 1.

Not awarded:

* No remote reachable signal. Packet traffic may help populate RX buffers, but traffic alone does not trigger ring deinit.
* No generic memory corruption. The patch fixes a leak and a defensive NULL check, not UAF, double-free, OOB write, or type confusion.
* No privilege escalation plausible signal. No reclaim, overwrite, stale callback, refcount takeover, or attacker-controlled object replacement is shown.
* No confidentiality or integrity impact. The supported impact is resource exhaustion only.

Call-site confidence: high. The affected function and deinit behavior are directly shown in the patch and commit message.

## 3. Reachability analysis

The bug is reachable when the Aquantia Atlantic driver is used and the RX ring is deinitialized after RX activity leaves consumed but not refilled buffers in the ring gap. A normal remote peer cannot directly trigger the vulnerable cleanup path. Local administrative control over the network interface is typically required.

Namespaces and containers may matter if CAP_NET_ADMIN or equivalent device-management control is delegated to a less trusted context. In normal host deployments this remains a privileged local issue. The affected hardware is device-specific, so exposure is limited to systems using the atlantic driver.

## 4. Severity interpretation

This behaves like an ordinary Moderate or Low-like resource leak rather than an Important-class vulnerability. The realistic impact is gradual memory or DMA mapping exhaustion through repeated interface lifecycle operations. The patch does not support a memory corruption primitive or a practical privilege-escalation path.

The partial allocation unwind NULL check prevents a possible crash on an error path, but the described primary issue is still cleanup incompleteness and resource leakage, not attacker-controlled corruption.

## 5. One-sentence report phrase

The atlantic driver could leak RX pages and DMA mappings on interface down because consumed but not refilled RX buffers were skipped during deinit, allowing a privileged local actor with network-device control to cause resource-exhaustion DoS through repeated down/up cycles.

## 6. Manual review recommendation

NO MANUAL CHECK NEEDED

This is a resource leak in a device-specific driver cleanup path with typical CAP_NET_ADMIN requirements and no supported memory-corruption, confidentiality, integrity, or privilege-escalation primitive.

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

Patch: net: atlantic: free RX pages of consumed but not refilled buffers
Commit: 1e58b0bab40dcbdfc04acaba6a221d40801c3770
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1e58b0bab40dcbdfc04acaba6a221d40801c3770

Commit description:

aq_ring_rx_deinit() only walks [sw_head, sw_tail), the region posted to
hardware. Since the page reuse strategy was added, a cleaned RX buffer
keeps its page (and its DMA mapping) in the ring for reuse, and refill
is batched: aq_ring_rx_fill() returns early until AQ_CFG_RX_REFILL_THRES
slots are free. Slots that were consumed but not yet reposted therefore
sit in the complementary [sw_tail, sw_head) gap with a live page, and
the deinit walk never visits them: up to a refill batch worth of pages
and DMA mappings leak on every interface down.

Walk the whole ring instead and release whatever is still there. Also
bail out if the buffer ring is already gone: a partial
aq_ptp_ring_alloc() failure frees the ring but leaves aq_nic set, so
aq_ptp_ring_deinit() still gets here on the unwind path.

Cc: stable@vger.kernel.org # v5.2+
Fixes: 46f4c29 ("net: aquantia: optimize rx performance by page reuse strategy")
Reviewed-by: Sukhdeep Singh <sukhdeeps@marvell.com>
Signed-off-by: Yangyu Chen <cyy@cyyself.name>
Acked-by: Mina Almasry <almasrymina@google.com>
Link: https://patch.msgid.link/tencent_607CBA8237DA438E36B844318B21538DE008@qq.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/ethernet/aquantia/atlantic/aq_ring.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=1e58b0bab40dcbdfc04acaba6a221d40801c3770

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

The original Linux kernel CVE announcement for CVE-2026-74622 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74622

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:L/PR:H/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.5

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: 0
  Paranoid ActionableScore: 1

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: LOW
KPANIC detected for this report: NO
Published priority for this report (same as in Subject): LOW

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).