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TI-2021-22109 Aliases CVE-2021-47454GHSA-rcm4-5vxv-3g8q

powerpc/smp: do not decrement idle task preempt count in CPU offline

Priority LOW 24Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 5 fixed, 3 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00225 13th percentileScored 2026-11-07
Fix Partial Linux (Linux): 5.10.76, 5.13, 5.14 +2Red Hat: 1 advisoryRed Hat: 5 fixed, 3 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux5.10.50 to before 5.10.76; 5.12.17 to before 5.13; 5.13.2 to before 5.145.10.76, 5.13, 5.14Patch availableCNA
LinuxLinux5.14 and later5.10.76, 5.14.15, 5.15Patch availableCNA
  • Linux VendorLinux Affected 5.10.50 to before 5.10.76; 5.12.17 to before 5.13; 5.13.2 to before 5.14 Fixed in 5.10.76, 5.13, 5.14 Patch available CNA
  • Linux VendorLinux Affected 5.14 and later Fixed in 5.10.76, 5.14.15, 5.15 Patch available CNA

CPE configurations NVD · 7

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*5.10.50 to before 5.10.76; 5.12.17 to before 5.13; 5.13.2 to before 5.14.15VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.15:rc1:*:*:*:*:*:*5.15 rc1VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.15:rc2:*:*:*:*:*:*5.15 rc2VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.15:rc3:*:*:*:*:*:*5.15 rc3VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.15:rc4:*:*:*:*:*:*5.15 rc4VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.15:rc5:*:*:*:*:*:*5.15 rc5VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.15:rc6:*:*:*:*:*:*5.15 rc6VulnerableLinux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 5.10.50 to before 5.10.76; 5.12.17 to before 5.13; 5.13.2 to before 5.14.15 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.15:rc1:*:*:*:*:*:* Versions 5.15 rc1 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.15:rc2:*:*:*:*:*:* Versions 5.15 rc2 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.15:rc3:*:*:*:*:*:* Versions 5.15 rc3 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.15:rc4:*:*:*:*:*:* Versions 5.15 rc4 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.15:rc5:*:*:*:*:*:* Versions 5.15 rc5 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.15:rc6:*:*:*:*:*:* Versions 5.15 rc6 Vulnerable ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 5.10.76, 5.13, 5.14
  • Fix · CNA Linux (Linux) Fixed in 5.10.76, 5.14.15, 5.15

Red Hat 1 advisory

  • RHSA-2024:9315 Released 2024-11-12 · Red Hat rating Moderate
    kernel security update
    • Red Hat CodeReady Linux Builder (v. 9) kernel-cross-headers-5.14.0-503.11.1.el9_5, kernel-tools-libs-devel-5.14.0-503.11.1.el9_5, libperf-5.14.0-503.11.1.el9_5
    • Red Hat Enterprise Linux AppStream (v. 9) kernel-64k-debug-devel-5.14.0-503.11.1.el9_5, kernel-64k-debug-devel-matched-5.14.0-503.11.1.el9_5, kernel-64k-devel-5.14.0-503.11.1.el9_5 +12
    • Red Hat Enterprise Linux BaseOS (v. 9) bpftool-7.4.0-503.11.1.el9_5, kernel-5.14.0-503.11.1.el9_5, kernel-64k-5.14.0-503.11.1.el9_5 +30
    • Red Hat Enterprise Linux Real Time (v. 9) kernel-rt-5.14.0-503.11.1.el9_5, kernel-rt-core-5.14.0-503.11.1.el9_5, kernel-rt-debug-5.14.0-503.11.1.el9_5 +9
    • Red Hat Enterprise Linux Real Time for NFV (v. 9) kernel-rt-5.14.0-503.11.1.el9_5, kernel-rt-core-5.14.0-503.11.1.el9_5, kernel-rt-debug-5.14.0-503.11.1.el9_5 +11

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 7AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 9AffectedNo fix yet
Red Hat CodeReady Linux Builder (v. 9)Fixed RHSA-2024:9315
Red Hat Enterprise Linux AppStream (v. 9)Fixed RHSA-2024:9315
Red Hat Enterprise Linux BaseOS (v. 9)Fixed RHSA-2024:9315
Red Hat Enterprise Linux Real Time (v. 9)Fixed RHSA-2024:9315
Red Hat Enterprise Linux Real Time for NFV (v. 9)Fixed RHSA-2024:9315
Not affected: 3 products
  • Red Hat CodeReady Linux Builder (v. 9)
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux AppStream (v. 9)

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-47454
  2. 2026-10-03 Alias added: GHSA-rcm4-5vxv-3g8q

References

Patch 3

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
  • TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
See all 15278 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences