rcu/rcuscale: Stop kfree_scale_thread thread(s) after unloading rcuscale

published 2025-09-16 13 mo ago modified 2026-06-17 4 mo ago also EUVD-2023-59898

cvss: 5.5; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 4%
public exploits: 0; none known

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

Running the 'kfree_rcu_test' test case [1] results in a splat [2]. The root cause is the kfree_scale_thread thread(s) continue running after unloading the rcuscale module. This commit fixes that isue by invoking kfree_scale_cleanup() from rcu_scale_cleanup() when removing the rcuscale module.

[1] modprobe rcuscale kfree_rcu_test=1 // After some time rmmod rcuscale rmmod torture

[2] BUG: unable to handle page fault for address: ffffffffc0601a87 #PF: supervisor instruction fetch in kernel mode #PF: error_code(0x0010) - not-present page PGD 11de4f067 P4D 11de4f067 PUD 11de51067 PMD 112f4d067 PTE 0 Oops: 0010 [#1] PREEMPT SMP NOPTI CPU: 1 PID: 1798 Comm: kfree_scale_thr Not tainted 6.3.0-rc1-rcu+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 RIP: 0010:0xffffffffc0601a87 Code: Unable to access opcode bytes at 0xffffffffc0601a5d. RSP: 0018:ffffb25bc2e57e18 EFLAGS: 00010297 RAX: 0000000000000000 RBX: ffffffffc061f0b6 RCX: 0000000000000000 RDX: 0000000000000000 RSI: ffffffff962fd0de RDI: ffffffff962fd0de RBP: ffffb25bc2e57ea8 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000 R13: 0000000000000000 R14: 000000000000000a R15: 00000000001c1dbe FS: 0000000000000000(0000) GS:ffff921fa2200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffffffc0601a5d CR3: 000000011de4c006 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <TASK> ? kvfree_call_rcu+0xf0/0x3a0 ? kthread+0xf3/0x120 ? kthread_complete_and_exit+0x20/0x20 ? ret_from_fork+0x1f/0x30 </TASK> Modules linked in: rfkill sunrpc ... [last unloaded: torture] CR2: ffffffffc0601a87 ---[ end trace 0000000000000000 ]---

Patch / fix

fixed in 1 distros 4 links 6

Linux Linux 5.10.188, 5.15.121, 6.1.39, 6.3.13, 6.4.4, 6.5

debian ubuntu red hat suse

linux Debian 12 6.1.52-1
linux Debian 14, Debian 13 6.4.4-1

debian advisories DEBIAN-CVE-2023-53291

linux Ubuntu 22.04 LTS 5.15.0-86.96
linux-aws Ubuntu 22.04 LTS 5.15.0-1047.52
linux-gcp Ubuntu 22.04 LTS 5.15.0-1044.52
linux-gke Ubuntu 22.04 LTS 5.15.0-1044.49
linux-ibm Ubuntu 22.04 LTS 5.15.0-1040.43
linux-kvm Ubuntu 22.04 LTS 5.15.0-1044.49
linux-azure Ubuntu 22.04 LTS 5.15.0-1049.56
linux-gkeop Ubuntu 22.04 LTS 5.15.0-1030.35

ubuntu advisories UBUNTU-CVE-2023-53291

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

kernel RHEL 9 5.14.0-503.11.1.el9_5
rv RHEL 9 5.14.0-503.11.1.el9_5
perf RHEL 9 5.14.0-503.11.1.el9_5
rtla RHEL 9 5.14.0-503.11.1.el9_5
bpftool RHEL 9 7.4.0-503.11.1.el9_5
libperf RHEL 9 5.14.0-503.11.1.el9_5
kernel-rt RHEL 9 5.14.0-503.11.1.el9_5
kernel-64k RHEL 9 5.14.0-503.11.1.el9_5

red hat advisories RHSA-2024:9315

kernel-rt Real Time Module 15 SP7 6.4.0-150700.7.22.1
kernel-syms-rt Real Time Module 15 SP7 6.4.0-150700.7.22.1
kernel-source-rt Real Time Module 15 SP7 6.4.0-150700.7.22.1
kernel-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.18.1
kernel-syms-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.18.1
kernel-source-azure SLE Module for Public Cloud 15 SP7 6.4.0-150700.20.18.1
kernel-64kb SLE Module for Basesystem 15 SP7 6.4.0-150700.53.22.1
kernel-syms SLE Module for Development Tools 15 SP7 6.4.0-150700.53.22.1

suse advisories SUSE-SU-2025:4141-1 SUSE-SU-2025:4132-1 SUSE-SU-2025:4057-1 SUSE-SU-2025:20870-1 SUSE-SU-2025:20898-1 SUSE-SU-2025:3751-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2023-53291 updated 2026-11-07 cvss 5.5

kernel: Linux kernel: Denial of Service due to improper thread termination in rcuscale module

Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 more
affected: no fix available “Fix deferred”
Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 10 kernel
not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation: none
Automatable: no
Technical impact: partial
Assessed: 9 mo ago (2026-01-14)

Exploit prediction

0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CISA ADP	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CNA	3.1	5.5	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Affected products

Linux Linux

Classification

Technology feeds

Linux kernel rss critical rss

References

Sources

CVE List CVE-2023-53291
NVD CVE-2023-53291

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary