[CVE-2026-68129][MODERATE REGULAR] gve: fix Rx queue stall on alloc failure

[CVE-2026-68129][MODERATE REGULAR] gve: fix Rx queue stall on alloc failure

[AL-KERNEL]

CVE: CVE-2026-68129
Priority: MODERATE REGULAR
AL-KERNEL base severity: MODERATE
KPANIC flag: NO
Patch: gve: fix Rx queue stall on alloc failure
Commit: 299d5728a7312fdd02059b074aebbe4ebbd391e4
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=299d5728a7312fdd02059b074aebbe4ebbd391e4
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68129
Analysis date: Mon, 10 Aug 2026 12:26:16 -0400
ActionableScore: 4
ActionableScore lower bound: 3
Actionable bucket: Borderline, manual review recommended / Ordinary Moderate with network DoS relevance
Manual review required: YES

Summary:
A gve Rx queue can permanently stall after Rx buffer refill allocation failures under extreme memory pressure, allowing network availability degradation when traffic reaches an affected interface, but the patch does not indicate memory corruption or privilege escalation.

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

The original Linux kernel CVE announcement for CVE-2026-68129 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68129

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 REGULAR
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
======================================================================

CVE-2026-68129	MODERATE	CHECK WITH IMPACT FROM ORIG NN MODERATE	Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H';**CWE-400;CWE-703;CWE-754;Other CVSS 'AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.9';DESCR 'The gve Rx path can permanently stall when page allocation failures happen during Rx buffer refill under extreme memory pressure. If too few descriptors remain visible to hardware, incoming packets may be dropped, no Rx completions are generated, NAPI is not scheduled again, and the queue may not recover even after memory is freed. For the CVSS the PR:N is used because a remote peer does not need a local account on the target to send traffic to the exposed interface, although reliable triggering also depends on memory pressure and driver state. The issue is network related but not a packet parser memory corruption bug. Impact is denial of service through loss of receive queue or interface availability, with no supported confidentiality or integrity impact.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended / Ordinary Moderate with network DoS relevance (with actual score 4)	YES	REMOTE DANGER INIT NETWORK TIMER HARDWARE IPV6 PACKET  DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5	NO	NO	checked

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

ActionableScore=4
ActionableScoreLower=3

## 1. ActionableScore

* Conservative score: 3
* Paranoid score: 4
* Final recommended bucket: **Borderline, manual review recommended / Ordinary Moderate with network DoS relevance**::

## 2. Signal breakdown

Conservative scoring:

* Remote reachable / network-triggerable: +2. Incoming traffic can contribute to Rx descriptor consumption and packet drops, but reliable triggering also depends on extreme memory pressure.
* Reliable kernel crash / strong DoS: +1. This is not a crash, but the described result is a permanent Rx queue stall that may not recover after memory is freed.
* Availability impact realistic: +1. The stall is persistent for the affected receive queue and can cause loss of network availability.
* Hard or unreliable condition required: -1. The trigger requires page allocation failures under extreme memory pressure plus the Rx queue falling below the descriptor threshold.

Conservative total: 3

Paranoid additional signal:

* Broad/default/common deployment exposure: +1. gve is a production virtual NIC driver used in cloud environments, so affected systems may be operationally important even though this is not a core networking path.

Paranoid total: 4

No memory corruption, UAF, OOB write, info leak, Dirty Pipe like primitive, privilege escalation, or security boundary bypass is supported by this patch.

## 3. Reachability analysis

A remote peer can send traffic to the affected interface, so PR is effectively none for the traffic source. However, the stall requires the target system to be under extreme memory pressure and to hit Rx refill allocation failures, so the trigger is not a simple packet parser bug and has high environmental dependency.

Namespaces and containers do not materially lower privilege requirements for the remote traffic component. A local unprivileged user or co tenant that can create memory pressure could make the condition more realistic, but the patch itself does not show a local kernel memory corruption or privilege boundary bypass.

The path is enabled only on systems using the Google gve driver and the affected DQO Rx path. This is not rare in some cloud deployments, but it is driver specific rather than a generic Linux networking core issue.

Call-site confidence: high. The patch shows the affected Rx refill path, the added timer, timer shutdown during ring stop, and the direct NAPI rescheduling behavior.

## 4. Severity interpretation

This behaves like an ordinary Moderate to borderline actionable Moderate issue. The practical impact is network availability loss through a persistent Rx queue stall.

Theoretical risk is limited to DoS based on the provided patch. There is no evidence of memory corruption, attacker-controlled overwrite, stale pointer reuse, confidentiality impact, integrity impact, or privilege escalation. The main reason not to auto-close immediately is that the bug is network influenced and can create a persistent receive-side failure in a production NIC driver.

## 5. One-sentence report phrase

A gve Rx queue can permanently stall after Rx buffer refill allocation failures under extreme memory pressure, allowing network availability degradation when traffic reaches an affected interface, but the patch does not indicate memory corruption or privilege escalation.

## 6. Manual review recommendation

MANUAL CHECK RECOMMENDED

Manual review is recommended because the issue is network related and can cause persistent interface or queue availability loss, but it does not currently justify Important severity without evidence of memory corruption, broader system-wide DoS, or privilege escalation.

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

Patch: gve: fix Rx queue stall on alloc failure
Commit: 299d5728a7312fdd02059b074aebbe4ebbd391e4
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=299d5728a7312fdd02059b074aebbe4ebbd391e4

Commit description:

When the system is under extreme memory pressure, page allocations can
fail during the Rx buffer refill loop. If the number of buffers posted
to hardware falls below a critical low threshold and the refill loop
exits due to allocation failures, the queue can stall:

1. The device drops incoming packets because there are no descriptors.
2. Since no packets are processed, no Rx completions are generated.
3. Because no completions occur, NAPI is never scheduled, preventing
   the refill loop from running again even after memory is freed.

This results in a permanent queue stall.

Resolve this by introducing a starvation recovery timer for each Rx queue.
If the number of buffers posted to hardware falls below a critical low
threshold, start a timer to periodically reschedule NAPI. Once NAPI runs
and successfully refills the queue above the threshold, the timer is
not rescheduled.

The threshold is set to 32 because a single maximum-sized Receive Segment
Coalescing (RSC) packet can consume up to 19 descriptors in the Rx path.
Lower thresholds (such as 8 or 16) would be insufficient to process a
complete maximum-sized RSC packet, risking packet drops or unexpected
hardware behavior under memory pressure. Setting the threshold to 32
guarantees a safe margin to handle at least one full RSC packet.

Cc: stable@vger.kernel.org
Fixes: 9b8dd5e ("gve: DQO: Add RX path")
Reviewed-by: Jordan Rhee <jordanrhee@google.com>
Signed-off-by: Eddie Phillips <eddiephillips@google.com>
Signed-off-by: Harshitha Ramamurthy <hramamurthy@google.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Link: https://patch.msgid.link/20260709211906.3322883-1-hramamurthy@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Changed files:
  drivers/net/ethernet/google/gve/gve.h
  net/xdp.h
  drivers/net/ethernet/google/gve/gve_main.c
  drivers/net/ethernet/google/gve/gve_rx_dqo.c
  net/ipv6.h
  net/tcp.h

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=299d5728a7312fdd02059b074aebbe4ebbd391e4

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

The original Linux kernel CVE announcement for CVE-2026-68129 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68129

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:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
  The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
  The Best / paranoid CVSS score: 5.9

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: 4

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 REGULAR

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).