---
id: CVE-2026-45845
title: 'net/sched: taprio: fix NULL pointer dereference in class dump'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net/sched: taprio: fix NULL pointer dereference in class dump

  When a TAPRIO child qdisc is deleted via RTM_DELQDISC, taprio_graft()
  is called with new == NULL and stor…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 <
    ec2501e361b08b50bcb1e7b3253fc861abbda28d
  - >-
    Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 <
    d02e2fbf60de46678e2ea698a6a904fd21e1cc31
  - >-
    Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 <
    48b26d48e76221dc90b02bf5428bab53643461ca
  - >-
    Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 <
    8f1ff8866cb9f655e5faea6994eb902960be8e04
  - >-
    Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 <
    3d07ca5c0fae311226f737963984bd94bb159a87
  - Linux 6.6
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-06T15:41:59.608192Z'
published: '2026-05-27'
updated: '2026-11-06'
sourceUpdated: '2026-11-06T15:42:59.407Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-45845'
references:
  - url: 'https://git.kernel.org/stable/c/ec2501e361b08b50bcb1e7b3253fc861abbda28d'
  - url: 'https://git.kernel.org/stable/c/d02e2fbf60de46678e2ea698a6a904fd21e1cc31'
  - url: 'https://git.kernel.org/stable/c/48b26d48e76221dc90b02bf5428bab53643461ca'
  - url: 'https://git.kernel.org/stable/c/8f1ff8866cb9f655e5faea6994eb902960be8e04'
  - url: 'https://git.kernel.org/stable/c/3d07ca5c0fae311226f737963984bd94bb159a87'
tags:
  - cve.org
epss: 0.0012
epssPercentile: 0.01813
ingestedAt: '2026-11-06T15:54:03.881Z'
---

## Overview

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

net/sched: taprio: fix NULL pointer dereference in class dump

When a TAPRIO child qdisc is deleted via RTM_DELQDISC, taprio_graft()
is called with new == NULL and stores NULL into q->qdiscs[cl - 1].
Subsequent RTM_GETTCLASS dump operations walk all classes via
taprio_walk() and call taprio_dump_class(), which calls taprio_leaf()
returning the NULL pointer, then dereferences it to read child->handle,
causing a kernel NULL pointer dereference.

The bug is reachable with namespace-scoped CAP_NET_ADMIN on any kernel
with CONFIG_NET_SCH_TAPRIO enabled. On systems with unprivileged user
namespaces enabled, an unprivileged local user can trigger a kernel
panic by creating a taprio qdisc inside a new network namespace,
grafting an explicit child qdisc, deleting it, and requesting a class
dump. The RTM_GETTCLASS dump itself requires no capability.

 Oops: general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] SMP KASAN NOPTI
 KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
 RIP: 0010:taprio_dump_class (net/sched/sch_taprio.c:2478)
 Call Trace:
  <TASK>
  tc_fill_tclass (net/sched/sch_api.c:1966)
  qdisc_class_dump (net/sched/sch_api.c:2326)
  taprio_walk (net/sched/sch_taprio.c:2514)
  tc_dump_tclass_qdisc (net/sched/sch_api.c:2352)
  tc_dump_tclass_root (net/sched/sch_api.c:2370)
  tc_dump_tclass (net/sched/sch_api.c:2431)
  rtnl_dumpit (net/core/rtnetlink.c:6864)
  netlink_dump (net/netlink/af_netlink.c:2325)
  rtnetlink_rcv_msg (net/core/rtnetlink.c:6959)
  netlink_rcv_skb (net/netlink/af_netlink.c:2550)
  </TASK>

Fix this by substituting &noop_qdisc when new is NULL in
taprio_graft(), a common pattern used by other qdiscs (e.g.,
multiq_graft()) to ensure the q->qdiscs[] slots are never NULL.
This makes control-plane dump paths safe without requiring individual
NULL checks.

Since the data-plane paths (taprio_enqueue and taprio_dequeue_from_txq)
previously had explicit NULL guards that would drop/skip the packet
cleanly, update those checks to test for &noop_qdisc instead. Without
this, packets would reach taprio_enqueue_one() which increments the root
qdisc's qlen and backlog before calling the child's enqueue; noop_qdisc
drops the packet but those counters are never rolled back, permanently
inflating the root qdisc's statistics.

After this change *old can be a valid qdisc, NULL, or &noop_qdisc.
Only call qdisc_put(*old) in the first case to avoid decreasing
noop_qdisc's refcount, which was never increased.

## Affected

- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < ec2501e361b08b50bcb1e7b3253fc861abbda28d`
- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < d02e2fbf60de46678e2ea698a6a904fd21e1cc31`
- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < 48b26d48e76221dc90b02bf5428bab53643461ca`
- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < 8f1ff8866cb9f655e5faea6994eb902960be8e04`
- `Linux >= 665338b2a7a0139337d1f85be65ed16e487f84c1 < 3d07ca5c0fae311226f737963984bd94bb159a87`
- `Linux 6.6`

## Remediation

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