---
id: CVE-2026-90248
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: cls_api: fix teardown of an adopted proto on insert-race loss

  In tc_new_tfilter() the create branch sets tp_created = 1 before calling
  tcf_chain_tp_insert_u…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: cls_api: fix teardown of an adopted proto on insert-race loss

  In tc_new_tfilter() the create branch sets tp_created = 1 before calling
  tcf_chain_tp_insert_u…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 <
    a68e664ddf16ecae6d769d6a2eb356f8abab75c9
  - >-
    Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 <
    df02b6dc136af45e92ee4c86f4aa6c9a60790b1e
  - >-
    Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 <
    bee2208276c8e0e40a249ffdcf6e5434a79a847c
  - >-
    Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 <
    219c87aeefdcc8c1caf28cc99e9b361ce7393d3a
  - >-
    Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 <
    bbe2fd6d77df630356185406a97317f6aa6a92cf
  - >-
    Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 <
    dc8b33b819cb02a75936940c120aa669ad89942d
  - >-
    Linux >= 8b64678e0af8f4d62a40149baedebe78503a5255 <
    d4e359b3608a0e184bbe8d61a5c3b50d0831c44a
  - Linux 5.1
published: '2026-09-17'
updated: '2026-09-17'
sourceUpdated: '2026-09-17T17:17:20.947'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-90248'
references:
  - url: 'https://git.kernel.org/stable/c/219c87aeefdcc8c1caf28cc99e9b361ce7393d3a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/a68e664ddf16ecae6d769d6a2eb356f8abab75c9'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bbe2fd6d77df630356185406a97317f6aa6a92cf'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/bee2208276c8e0e40a249ffdcf6e5434a79a847c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/d4e359b3608a0e184bbe8d61a5c3b50d0831c44a'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/dc8b33b819cb02a75936940c120aa669ad89942d'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/df02b6dc136af45e92ee4c86f4aa6c9a60790b1e'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
ingestedAt: '2026-09-17T16:21:47.845Z'
epss: 0.00215
epssPercentile: 0.10476
---

## Overview

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

net/sched: cls_api: fix teardown of an adopted proto on insert-race loss

In tc_new_tfilter() the create branch sets tp_created = 1 before calling
tcf_chain_tp_insert_unique(). When the caller loses the race (another
request inserted a proto at the same chain/prio first), insert_unique()
destroys the caller's own tp_new and returns the winner's proto with an
extra reference. tp_created was never cleared, so the loser's errout
path treated the winner's live proto as its own and called
tcf_chain_tp_delete_empty() on it, silently unlinking an active
classifier that the winning request already advertised via
RTM_NEWTFILTER.

Track the outcome of the insert step in a single tri-state variable so
each errout path reacts correctly:

- TP_NOT_CREATED: no proto created; pursue the old path.
- TP_CREATED: proto inserted successfully; same code path as before.
- TP_NOT_OWNED: New - lost the insert race; tp is another request's proto
  (chain ref already released by tp_new's destroy)

Both errout reactions are single expressions derived from the state.

This fix is motivated by the Sashiko's automated review of Patch
(net/sched: cls_api: Always acquire rtnl_lock when destroying locked
classifiers) [1][2]. The review identified the silent-unlink behaviour of
an adopted proto's teardown when a request loses the
tcf_chain_tp_insert_unique() race.

[1] https://sashiko.dev/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com
[2] https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260801125632.360365-1-jhs%40mojatatu.com

## Remediation

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