5.5

CVE-2021-47454: powerpc/smp: do not decrement idle task preempt count in CPU offline

Analyzed
AliasesUBUNTU-CVE-2021-47454DEBIAN-CVE-2021-47454
Published 22-05-2024Last modified 23-05-2026

Vulnerability summary

CVE-2021-47454 is a medium (CVSS 5.5) vulnerability in linux. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 13.2% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
5.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.22%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 6 · Related 5
RHSA-2024:9315SUSE-SU-2024:2008-1SUSE-SU-2024:2011-1SUSE-SU-2024:2019-1SUSE-SU-2024:2189-1SUSE-SU-2024:2190-1

Timeline

  1. 22-05-2024
    PublishedVulnerability first disclosed.
  2. 23-05-2026
    Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: powerpc/smp: do not decrement idle task preempt count in CPU offline With PREEMPT_COUNT=y, when a CPU is offlined and then onlined again, we get: BUG: scheduling while atomic: swapper/1/0/0x00000000 no locks held by swapper/1/0. CPU: 1 PID: 0 Comm: swapper/1 Not tainted 5.15.0-rc2+ #100 Call Trace: dump_stack_lvl+0xac/0x108 __schedule_bug+0xac/0xe0 __schedule+0xcf8/0x10d0 schedule_idle+0x3c/0x70 do_idle+0x2d8/0x4a0 cpu_startup_entry+0x38/0x40 start_secondary+0x2ec/0x3a0 start_secondary_prolog+0x10/0x14 This is because powerpc's arch_cpu_idle_dead() decrements the idle task's preempt count, for reasons explained in commit a7c2bb8279d2 ("powerpc: Re-enable preemption before cpu_die()"), specifically "start_secondary() expects a preempt_count() of 0." However, since commit 2c669ef6979c ("powerpc/preempt: Don't touch the idle task's preempt_count during hotplug") and commit f1a0a376ca0c ("sched/core: Initialize the idle task with preemption disabled"), that justification no longer holds. The idle task isn't supposed to re-enable preemption, so remove the vestigial preempt_enable() from the CPU offline path. Tested with pseries and powernv in qemu, and pseries on PowerVM.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.22%

Chance of exploitation in the next 30 days

Percentile

13%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.22% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

No weakness data has been published for this record.

Affected systems

Version check

Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.

Ubuntu62 products
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
  • linux-aws-5.13All versions (No fix recorded)
  • linux-aws-5.19All versions (No fix recorded)
Linux2 products
  • linux≥ bdf4d33e8342b90386156204e1da0cdfdb4bf146, < 53770a411559cf7bc0906d1df319cc533d2f4f58 | ≥ 2c669ef6979c370f98d4b876e54f19613c81e075, < 3ea0b497a7a2fff6a4b7090310c9f52c91975934 | ≥ 2c669ef6979c370f98d4b876e54f19613c81e075, < 787252a10d9422f3058df9a4821f389e5326c440 | 2b6148ef2bd6d8ddc76e7873114f7769b6aa25f0 | 20a015e948b825afb47855de2efce7cae7c2608f | ≥ 5.10.50, < 5.10.76 | ≥ 5.12.17, < 5.13 | ≥ 5.13.2, < 5.14 | 5.14
  • linux_kernel≥ 5.10.50, < 5.10.76 | ≥ 5.12.17, < 5.13 | ≥ 5.13.2, < 5.14.15 | 5.15:rc1 | 5.15:rc2 | 5.15:rc3 | 5.15:rc4 | 5.15:rc5 | 5.15:rc6
Debian1 product
  • linux< 5.14.16-1

3 vendors · 65 products

References

7 links