CVE-2021-47454
powerpc/smp: do not decrement idle task preempt count in CPU offline
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.
INFO
Published Date :
May 22, 2024, 7:15 a.m.
Last Modified :
Sept. 29, 2025, 4:48 p.m.
Remotely Exploit :
No
Source :
416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update the affected Linux packages.
- Reboot the system for changes to take effect.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2021-47454.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2021-47454 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2021-47454
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2021-47454 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2021-47454 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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Initial Analysis by [email protected]
Sep. 29, 2025
Action Type Old Value New Value Added CVSS V3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Added CWE NVD-CWE-noinfo Added CPE Configuration OR *cpe:2.3:o:linux:linux_kernel:5.15:rc2:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.15:rc3:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.15:rc5:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.15:rc1:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.15:rc4:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:5.15:rc6:*:*:*:*:*:* *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.10.50 up to (excluding) 5.10.76 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.12.17 up to (excluding) 5.13 *cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* versions from (including) 5.13.2 up to (excluding) 5.14.15 Added Reference Type CVE: https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934 Types: Patch Added Reference Type CVE: https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58 Types: Patch Added Reference Type CVE: https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440 Types: Patch Added Reference Type kernel.org: https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440 Types: Patch -
CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Nov. 21, 2024
Action Type Old Value New Value Added Reference https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934 Added Reference https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58 Added Reference https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440 -
CVE Modified by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
May. 28, 2024
Action Type Old Value New Value -
CVE Received by 416baaa9-dc9f-4396-8d5f-8c081fb06d67
May. 22, 2024
Action Type Old Value New Value Added 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. Added Reference kernel.org https://git.kernel.org/stable/c/53770a411559cf7bc0906d1df319cc533d2f4f58 [No types assigned] Added Reference kernel.org https://git.kernel.org/stable/c/3ea0b497a7a2fff6a4b7090310c9f52c91975934 [No types assigned] Added Reference kernel.org https://git.kernel.org/stable/c/787252a10d9422f3058df9a4821f389e5326c440 [No types assigned]