Description
In the Linux kernel, the following vulnerability has been resolved:
s390/idle: mark arch_cpu_idle() noinstr
linux-next commit ("cpuidle: tracing: Warn about !rcu_is_watching()")
adds a new warning which hits on s390's arch_cpu_idle() function:
RCU not on for: arch_cpu_idle+0x0/0x28
WARNING: CPU: 2 PID: 0 at include/linux/trace_recursion.h:162 arch_ftrace_ops_list_func+0x24c/0x258
Modules linked in:
CPU: 2 PID: 0 Comm: swapper/2 Not tainted 6.2.0-rc6-next-20230202 #4
Hardware name: IBM 8561 T01 703 (z/VM 7.3.0)
Krnl PSW : 0404d00180000000 00000000002b55c0 (arch_ftrace_ops_list_func+0x250/0x258)
R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:3 CC:1 PM:0 RI:0 EA:3
Krnl GPRS: c0000000ffffbfff 0000000080000002 0000000000000026 0000000000000000
0000037ffffe3a28 0000037ffffe3a20 0000000000000000 0000000000000000
0000000000000000 0000000000f4acf6 00000000001044f0 0000037ffffe3cb0
0000000000000000 0000000000000000 00000000002b55bc 0000037ffffe3bb8
Krnl Code: 00000000002b55b0: c02000840051 larl %r2,0000000001335652
00000000002b55b6: c0e5fff512d1 brasl %r14,0000000000157b58
#00000000002b55bc: af000000 mc 0,0
>00000000002b55c0: a7f4ffe7 brc 15,00000000002b558e
00000000002b55c4: 0707 bcr 0,%r7
00000000002b55c6: 0707 bcr 0,%r7
00000000002b55c8: eb6ff0480024 stmg %r6,%r15,72(%r15)
00000000002b55ce: b90400ef lgr %r14,%r15
Call Trace:
[<00000000002b55c0>] arch_ftrace_ops_list_func+0x250/0x258
([<00000000002b55bc>] arch_ftrace_ops_list_func+0x24c/0x258)
[<0000000000f5f0fc>] ftrace_common+0x1c/0x20
[<00000000001044f6>] arch_cpu_idle+0x6/0x28
[<0000000000f4acf6>] default_idle_call+0x76/0x128
[<00000000001cc374>] do_idle+0xf4/0x1b0
[<00000000001cc6ce>] cpu_startup_entry+0x36/0x40
[<0000000000119d00>] smp_start_secondary+0x140/0x150
[<0000000000f5d2ae>] restart_int_handler+0x6e/0x90
Mark arch_cpu_idle() noinstr like all other architectures with
CONFIG_ARCH_WANTS_NO_INSTR (should) have it to fix this.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Linux | Linux | 4.19.297 – < 4.20, 5.9 | 4.20 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | linux | 6.1.20-1 | — |
| Debian 13 | linux | 6.1.20-1 | — |
| Debian 12 | linux | 6.1.20-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Nvidia-BlueField 22.04 LTS | linux-bluefield | 5.15.0-1019.21 | — |
| Ubuntu 24.04 LTS | linux-riscv +10 | No fix yet | — |
| Ubuntu 22.04 LTS | linux +1 | 5.15.0-75.82 | — |
| Ubuntu 22.04 LTS | linux-aws | 5.15.0-1038.43 | — |
| Ubuntu 22.04 LTS | linux-azure | 5.15.0-1040.47 | — |
| Ubuntu 22.04 LTS | linux-azure-fde | 5.15.0-1041.48.1 | — |
| Ubuntu 22.04 LTS | linux-gcp | 5.15.0-1036.44 | — |
| Ubuntu 22.04 LTS | linux-gke | 5.15.0-1036.41 | — |
| Ubuntu 22.04 LTS | linux-gkeop | 5.15.0-1022.27 | — |
| Ubuntu 22.04 LTS | linux-ibm +1 | 5.15.0-1032.35 | — |
| Ubuntu 22.04 LTS | linux-intel-iotg | 5.15.0-1033.38 | — |
| Ubuntu 22.04 LTS | linux-kvm | 5.15.0-1035.40 | — |
| Ubuntu 22.04 LTS | linux-nvidia | 5.15.0-1027.27 | — |
| Ubuntu 22.04 LTS | linux-nvidia-tegra | 5.15.0-1015.15 | — |
| Ubuntu 22.04 LTS | linux-oracle | 5.15.0-1037.43 | — |
| Ubuntu 22.04 LTS | linux-riscv +32 | No fix yet | — |
| Ubuntu 20.04 LTS | linux-aws-5.15 | 5.15.0-1038.43~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-azure-5.15 | 5.15.0-1040.47~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-gcp-5.15 | 5.15.0-1036.44~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-gke +28 | No fix yet | — |
| Ubuntu 20.04 LTS | linux-hwe-5.15 +1 | 5.15.0-75.82~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-intel-iotg-5.15 | 5.15.0-1033.38~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-nvidia-tegra-5.15 | 5.15.0-1015.15~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-oracle-5.15 | 5.15.0-1037.43~20.04.1 | — |
| Ubuntu 20.04 LTS | linux-riscv-5.15 | 5.15.0-1035.39~20.04.1 | — |
| Ubuntu 18.04 LTS | linux-gcp +14 | No fix yet | — |
Show 3 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
| Ubuntu Pro Realtime 22.04 LTS | linux-intel-iot-realtime | 5.15.0-1033.35 | — |
| Ubuntu Pro Realtime 22.04 LTS | linux-realtime | 5.15.0-1040.45 | — |
| Ubuntu Pro FIPS-preview 22.04 LTS | linux-fips | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9 | rv +77 | 5.14.0-570.12.1.el9_6 | RHSA-2025:6966 |
Advisories 2
- RHSA-2025:6966 Red Hat Security Advisory: kernel security update Red Hat Security Advisories (RHSA) · Nov 13, 2026
- WID-SEC-2025-2765 Linux Kernel: Mehrere Schwachstellen ermöglichen Denial of Service BSI CERT-Bund (WID) · Nov 12, 2026