[CVE-2026-99048][LOW] gve: fix napi_disable deadlock when attempting to disable XSK pools

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

CVE: CVE-2026-99048
Priority: LOW
AL-KERNEL base severity: LOW
KPANIC flag: NO
Patch: gve: fix napi_disable deadlock when attempting to disable XSK pools
Commit: 42935a61001927aa01db10b53b420efd37eaa99b
Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=42935a61001927aa01db10b53b420efd37eaa99b
Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99048
Analysis date: Mon, 26 Oct 2026 20:58:41 -0400
ActionableScore: 1
ActionableScore lower bound: unknown
Actionable bucket: Ordinary Moderate
Manual review required: NO

Summary:
GVE can self-deadlock its network-device control path when disabling an XSK pool by calling lock-taking NAPI helpers while the netdev lock is already held.

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

The original Linux kernel CVE announcement for CVE-2026-99048 is available here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99048

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
======================================================================

CVE-2026-99048	LOW	https://www.kernelcve.org/list/?q=CVE-2026-99048 CHECK WITH IMPACT FROM ORIG NN MODERATE | AEGIS IMPACT MODERATE_KPANIC AEGIS_AS=1 LEGACY=LOW RESULT=DIFF TEMP_DISTANCE_MERGE_SKIP=AEGIS_NO_POSITIVE_SEVERITY_EVIDENCE (final Legacy and Aegis differ; FINAL: LOW, Aegis: MODERATE_KPANIC)	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-667;*CWE-833;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'GVE can self deadlock while disabling an XSK pool because ndo_bpf is entered with the netdev lock already held and gve_xsk_pool_disable calls NAPI helpers that attempt to acquire the same lock again. The confirmed impact is a local denial of service affecting the XSK disable operation and network device control path. The paranoid availability rating allows for an indefinite lock hold that can prevent critical reconfiguration or recovery of the affected network interface. For the CVSS the PR:L value reflects that a local process with permission to create or manage the AF_XDP and XSK binding is required. The issue is not directly network reachable and there is no supported UAF, OOB access, information leak, or memory write primitive. Automated impact decision path. The original SimpleNet classifier selected MODERATE_KPANIC. The primary LLM estimated paranoid CVSS 5.5 and the production ActionableScore returned 1 with recommendation Ordinary Moderate. The production rules then evaluated CVSS thresholds and ActionableScore thresholds. Recorded rule transitions were CVSS and initial triage stage MODERATE_KPANIC to MODERATE because the CVSS score, vector or bug class threshold rule was applied. ActionableScore thresholds stage MODERATE to LOW because the ActionableScore threshold rule was applied. final reconciliation stage LOW to LOW because KP specialist did not establish a qualifying panic and the cross model evidence reconciliation rule was applied. The legacy KP specialist has no review artifact for this run. The legacy FD or DH downgrade specialist has no review artifact for this run. Exact triggered rule markers were DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH and DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 and KPANIC_UNSUPPORTED_REMOVED and V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED. The independent weaker Aegis shadow evaluated CVSS 3.3 and ActionableScore 1 with primitive class CLASS_C and manual review REQUIRED. Its independently reconciled impact was MODERATE_KPANIC. The models disagreed but the aggregation rules retained the production result. The final reported impact is LOW.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 1)	MAYBE	REMOTE DEADLOCK SIMPLEFIX NETWORK LINUS DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 KPANIC_UNSUPPORTED_REMOVED V64_AEGIS_UNSUPPORTED_PROMOTION_BLOCKED	-	-	checked

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

ActionableScore=1
PrimitiveClass=CLASS_C
RealUAF=NO
HostAdminRequired=UNKNOWN
NamespaceScopedPrivilege=UNKNOWN
ImportantCandidate=NO
ManualReview=NO
AutoDowngradeAllowed=YES
RequiresHostUID0=UNKNOWN
AuthorizationDecisionBypass=NO
ProtectedResourceImpact=NONE
B4PendingReview=NO
B4PendingConfirmed=NO

1. ActionableScore

* Raw base score: 1
* Conservative score: 1; no floor or cap applied.
* Raw paranoid score: 1
* Paranoid score: 1; no distinct additional availability effect is shown.
* Final recommended bucket: **Ordinary Moderate**::

2. Signal breakdown

* +1 Reliable DoS: `ndo_bpf` already holds the netdev lock, while `napi_disable()` attempts to acquire it again, producing the documented self-deadlock during XSK-pool disable.
* No extra availability point: indefinite interface reconfiguration blockage is the consequence of the same deadlock.
* No corruption points: the patch shows no UAF, OOB access, invalid write, stale object, or lifetime violation.
* No remote or ordinary-unprivileged bonus: the operation is local and requires authority to manage the AF_XDP/XSK binding, but the exact permission model is not supplied.
* No privilege penalty: host-administrator-equivalent privilege is not positively established.
* No authorization signal: this changes lock-aware NAPI helper selection, not an access-control decision.
* NEW52/B5-R and NEW53/B3-PENDING do not apply: there is neither an OOB write nor a shared-backing write.

3. Reachability analysis

The trigger is XSK-pool disable through the GVE `ndo_bpf` control path. A local actor able to manage the relevant AF_XDP/XSK binding can invoke it, but the evidence does not establish whether the complete operation requires host CAP_NET_ADMIN, delegated authority, or namespace-scoped capability. Prior setup and UID 0 requirements are likewise unresolved. There is no timing race: the recursive lock acquisition follows deterministically once this path is entered. GVE device availability is required, but no rare-hardware penalty is justified.

4. Primitive and severity reading

The exact defect is a same-thread recursive netdev-lock acquisition causing deadlock. It is CLASS_C availability behavior, not memory corruption or an authorization bypass. The shown impact is blockage of XSK disable and potentially related interface control/recovery. Host panic, confidentiality loss, integrity loss, and privilege escalation are unsupported. ImportantCandidate is NO and auto-downgrade is allowed because no material corruption or unresolved security-boundary primitive exists.

5. One-sentence report phrase

GVE can self-deadlock its network-device control path when disabling an XSK pool by calling lock-taking NAPI helpers while the netdev lock is already held.

6. Manual review advice

NO MANUAL CHECK NEEDED

The patch and commit establish a constrained local availability defect without memory corruption or authorization impact.

7. Call-site confidence

Call-site confidence: high

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

Patch: gve: fix napi_disable deadlock when attempting to disable XSK pools
Commit: 42935a61001927aa01db10b53b420efd37eaa99b
Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=42935a61001927aa01db10b53b420efd37eaa99b

Commit description:

When disabling XSK pools, GVE calls the unlocked versions of
napi_disable and napi_enable. However, the netdev lock has already been
acquired before ndo_bpf is called because GVE supports queue management
ops. Calling the unlocked versions of napi_disable/enable results in a
deadlock when attempting to disable XSK pools, as the thread attempts to
re-acquire a lock it already holds.

Update the NAPI calls to use the locked versions.

This issue was found in production.

Fixes: 606048c ("net: designate XSK pool pointers in queues as "ops protected"")
Cc: stable@vger.kernel.org
Reviewed-by: Harshitha Ramamurthy <hramamurthy@google.com>
Reviewed-by: Jordan Rhee <jordanrhee@google.com>
Signed-off-by: Joshua Washington <joshwash@google.com>
Link: https://patch.msgid.link/20260930214735.3288780-4-joshwash@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Changed files:
  drivers/net/ethernet/google/gve/gve_main.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=42935a61001927aa01db10b53b420efd37eaa99b

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

The original Linux kernel CVE announcement for CVE-2026-99048 can be found here:
https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-99048

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:L/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: unknown
  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).