---
id: CVE-2026-31691
title: 'igb: remove napi_synchronize() in igb_down()'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  igb: remove napi_synchronize() in igb_down()

  When an AF_XDP zero-copy application terminates abruptly (e.g., kill -9),
  the XSK buffer pool is destroyed but NAPI pollin…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 2c6196013f84651772388a86dfd4bb033d0c0d45 <
    4700471775746058c962ded6e659bf908fd76e13
  - >-
    Linux >= 2c6196013f84651772388a86dfd4bb033d0c0d45 <
    27f5997686ee7fb7ac01be72b2010f168a3409fc
  - >-
    Linux >= 2c6196013f84651772388a86dfd4bb033d0c0d45 <
    b1e067240379f950a0022208e0685f3465c211cb
  - Linux 6.14
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T15:24:22.822570Z'
published: '2026-04-27'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T15:32:23.128Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-31691'
references:
  - url: 'https://git.kernel.org/stable/c/4700471775746058c962ded6e659bf908fd76e13'
  - url: 'https://git.kernel.org/stable/c/27f5997686ee7fb7ac01be72b2010f168a3409fc'
  - url: 'https://git.kernel.org/stable/c/b1e067240379f950a0022208e0685f3465c211cb'
tags:
  - cve.org
epss: 0.00112
epssPercentile: 0.01403
ingestedAt: '2026-11-06T15:54:04.045Z'
---

## Overview

In the Linux kernel, the following vulnerability has been resolved:

igb: remove napi_synchronize() in igb_down()

When an AF_XDP zero-copy application terminates abruptly (e.g., kill -9),
the XSK buffer pool is destroyed but NAPI polling continues.
igb_clean_rx_irq_zc() repeatedly returns the full budget, preventing
napi_complete_done() from clearing NAPI_STATE_SCHED.

igb_down() calls napi_synchronize() before napi_disable() for each queue
vector. napi_synchronize() spins waiting for NAPI_STATE_SCHED to clear,
which never happens. igb_down() blocks indefinitely, the TX watchdog
fires, and the TX queue remains permanently stalled.

napi_disable() already handles this correctly: it sets NAPI_STATE_DISABLE.
After a full-budget poll, __napi_poll() checks napi_disable_pending(). If
set, it forces completion and clears NAPI_STATE_SCHED, breaking the loop
that napi_synchronize() cannot.

napi_synchronize() was added in commit 41f149a285da ("igb: Fix possible
panic caused by Rx traffic arrival while interface is down").
napi_disable() provides stronger guarantees: it prevents further
scheduling and waits for any active poll to exit.
Other Intel drivers (ixgbe, ice, i40e) use napi_disable() without a
preceding napi_synchronize() in their down paths.

Remove redundant napi_synchronize() call and reorder napi_disable()
before igb_set_queue_napi() so the queue-to-NAPI mapping is only
cleared after polling has fully stopped.

## Affected

- `Linux >= 2c6196013f84651772388a86dfd4bb033d0c0d45 < 4700471775746058c962ded6e659bf908fd76e13`
- `Linux >= 2c6196013f84651772388a86dfd4bb033d0c0d45 < 27f5997686ee7fb7ac01be72b2010f168a3409fc`
- `Linux >= 2c6196013f84651772388a86dfd4bb033d0c0d45 < b1e067240379f950a0022208e0685f3465c211cb`
- `Linux 6.14`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.