---
id: CVE-2026-72390
title: 'net/sched: sch_teql: Introduce slaves_lock to avoid race condition and UAF'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: sch_teql: Introduce slaves_lock to avoid race condition and UAF

  The teql master->slaves singly linked list is not protected against
  multiple writes. It can …
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    03c67781254c574ae7fa75e881239a78473bdf42
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    735567bde7401f82b064f9f107b52ee1bf84ed8c
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    11402e6e18e96df615cbcc58157818dd604b23ff
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    9b7d05cbaa60108642402100efa6aa288dd33023
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    b26aa9d993537a4c3167d8ceead3b7c69c3a0aac
  - >-
    Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 <
    e5b811fe793166aecc59b085c1b7c31262ef2316
  - Linux 2.6.12
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-10-16T18:48:26.249891Z'
published: '2026-08-15'
updated: '2026-10-16'
sourceUpdated: '2026-10-16T18:55:21.250Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-72390'
references:
  - url: 'https://git.kernel.org/stable/c/03c67781254c574ae7fa75e881239a78473bdf42'
  - url: 'https://git.kernel.org/stable/c/735567bde7401f82b064f9f107b52ee1bf84ed8c'
  - url: 'https://git.kernel.org/stable/c/11402e6e18e96df615cbcc58157818dd604b23ff'
  - url: 'https://git.kernel.org/stable/c/9b7d05cbaa60108642402100efa6aa288dd33023'
  - url: 'https://git.kernel.org/stable/c/b26aa9d993537a4c3167d8ceead3b7c69c3a0aac'
  - url: 'https://git.kernel.org/stable/c/e5b811fe793166aecc59b085c1b7c31262ef2316'
tags:
  - cve.org
epss: 0.00174
epssPercentile: 0.06419
ingestedAt: '2026-10-16T19:46:24.401Z'
---

## Overview

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

net/sched: sch_teql: Introduce slaves_lock to avoid race condition and UAF

The teql master->slaves singly linked list is not protected against
multiple writes. It can be mod'ed concurently from teql_master_xmit(),
teql_dequeue(), teql_init() and teql_destroy() without holding any list
lock or RCU protection.

zdi-disclosures@trendmicro.com has demonstrated that the qdisc is freed
after an RCU grace period, but teql_master_xmit() running on another
CPU can still hold a stale pointer into the list, resulting in a
slab-use-after-free:

BUG: KASAN: slab-use-after-free in teql_master_xmit+0xf0f/0x16b0
Read of size 8 at addr ffff888013fb0440 by task poc/332
Freed 512-byte region [ffff888013fb0400, ffff888013fb0600) (kmalloc-512)

The fix?
Add a per-master slaves_lock spinlock that serializes all mutations of
master->slaves and the NEXT_SLAVE() links in teql_destroy() and
teql_qdisc_init(). teql_master_xmit() also takes the same slaves_lock
around those updates.
Annotate master->slaves and the per-slave ->next pointer with __rcu and
use the appropriate RCU accessors everywhere they are touched:
rcu_assign_pointer() on the writer side (under slaves_lock),
rcu_dereference_protected() for the writer-side loads (also under
slaves_lock), rcu_dereference_bh() for the loads in teql_master_xmit() and
rtnl_dereference() for the loads in teql_master_open()/teql_master_mtu(),
which run under RTNL.
Pair this with rcu_read_lock_bh()/rcu_read_unlock_bh() around the list
traversal in teql_master_xmit(), so that readers either observe a fully
linked list or are deferred until the in-flight mutation completes. The two
early-return paths in teql_master_xmit() are updated to release the RCU-bh
read-side critical section before returning, since leaving it held would
disable BH on that CPU for good.

## Affected

- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 03c67781254c574ae7fa75e881239a78473bdf42`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 735567bde7401f82b064f9f107b52ee1bf84ed8c`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 11402e6e18e96df615cbcc58157818dd604b23ff`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < 9b7d05cbaa60108642402100efa6aa288dd33023`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < b26aa9d993537a4c3167d8ceead3b7c69c3a0aac`
- `Linux >= 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 < e5b811fe793166aecc59b085c1b7c31262ef2316`
- `Linux 2.6.12`

## Remediation

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