CVE-2024-26765
NoneCVSS
—
EPSS
0.2%
Published
Apr 3, 2024
CISA due date
—
Cloudanix analysis
A timing problem in Linux on certain processors can cause errors or crashes when the system tries to turn CPUs on or off while running.
- Exploitation
- Local Privilege
- Attacker needs
- Local User
- Complexity
- Theoretical
- Impact
- Denial Of Service
- Component
- OS kernel
- Class
- Race Condition
- Remediation
- Upgrade
- Effort
- Medium
- Patch risk
- Low
What it actually does
Interrupts are enabled when init_fn() runs on non-boot CPUs during hotplug on LoongArch, allowing unexpected interrupts that hit rcu_cpu_starting and tlb_init before per-CPU state is ready and produce RCU warnings or errors.
Why it matters to the business
LoongArch systems may experience kernel warnings, instability, or crashes when CPUs are added or removed at runtime, affecting availability in virtualized or dynamically scaled deployments.
How an attack unfolds
An attacker with local access triggers CPU hotplug events while the kernel is starting secondary CPUs; the missing IRQ disable creates a window for interrupts that violate RCU assumptions and can be abused to panic the system.
How to fix it
Update the Linux kernel to a version containing commit a262b78dd085dbe9b3c75dc1d9c4cd102b110b53; rebuild and reboot all affected LoongArch systems.
How to confirm the fix worked
Confirm the fix commit is present in the running kernel source tree, then perform repeated CPU hotplug operations while monitoring for absence of rcu_cpu_starting and tlb_init warnings.
Typical attack path
- Obtain local unprivileged access on a LoongArch Linux host
- Trigger CPU online/offline via sysfs or hotplug tools
- Induce the race window before per-CPU trap and RCU initialization completes
- Observe or escalate resulting warnings into denial of service
How to detect it
Search kernel logs and dmesg for rcu_cpu_starting warnings, tlb_init call traces, and BRK exceptions on CPU 1+ during secondary CPU bring-up on LoongArch.
What your security team should do
- Prioritize kernel updates on all LoongArch production systems
- Restrict unprivileged access to CPU hotplug interfaces until patched
- Add kernel log monitoring for RCU and CPU-start warnings on LoongArch hosts
The record
In the Linux kernel, the following vulnerability has been resolved: LoongArch: Disable IRQ before init_fn() for nonboot CPUs Disable IRQ before init_fn() for nonboot CPUs when hotplug, in order to silence such warnings (and also avoid potential errors due to unexpected interrupts): WARNING: CPU: 1 PID: 0 at kernel/rcu/tree.c:4503 rcu_cpu_starting+0x214/0x280 CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.6.17+ #1198 pc 90000000048e3334 ra 90000000047bd56c tp 900000010039c000 sp 900000010039fdd0 a0 0000000000000001 a1 0000000000000006 a2 900000000802c040 a3 0000000000000000 a4 0000000000000001 a5 0000000000000004 a6 0000000000000000 a7 90000000048e3f4c t0 0000000000000001 t1 9000000005c70968 t2 0000000004000000 t3 000000000005e56e t4 00000000000002e4 t5 0000000000001000 t6 ffffffff80000000 t7 0000000000040000 t8 9000000007931638 u0 0000000000000006 s9 0000000000000004 s0 0000000000000001 s1 9000000006356ac0 s2 9000000007244000 s3 0000000000000001 s4 0000000000000001 s5 900000000636f000 s6 7fffffffffffffff s7 9000000002123940 s8 9000000001ca55f8 ra: 90000000047bd56c tlb_init+0x24c/0x528 ERA: 90000000048e3334 rcu_cpu_starting+0x214/0x280 CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) PRMD: 00000000 (PPLV0 -PIE -PWE) EUEN: 00000000 (-FPE -SXE -ASXE -BTE) ECFG: 00071000 (LIE=12 VS=7) ESTAT: 000c0000 [BRK] (IS= ECode=12 EsubCode=0) PRID: 0014c010 (Loongson-64bit, Loongson-3A5000) CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.6.17+ #1198 Stack : 0000000000000000 9000000006375000 9000000005b61878 900000010039c000 900000010039fa30 0000000000000000 900000010039fa38 900000000619a140 9000000006456888 9000000006456880 900000010039f950 0000000000000001 0000000000000001 cb0cb028ec7e52e1 0000000002b90000 9000000100348700 0000000000000000 0000000000000001 ffffffff916d12f1 0000000000000003 0000000000040000 9000000007930370 0000000002b90000 0000000000000004 9000000006366000 900000000619a140 0000000000000000 0000000000000004 0000000000000000 0000000000000009 ffffffffffc681f2 9000000002123940 9000000001ca55f8 9000000006366000 90000000047a4828 00007ffff057ded8 00000000000000b0 0000000000000000 0000000000000000 0000000000071000 ... Call Trace: [<90000000047a4828>] show_stack+0x48/0x1a0 [<9000000005b61874>] dump_stack_lvl+0x84/0xcc [<90000000047f60ac>] __warn+0x8c/0x1e0 [<9000000005b0ab34>] report_bug+0x1b4/0x280 [<9000000005b63110>] do_bp+0x2d0/0x480 [<90000000047a2e20>] handle_bp+0x120/0x1c0 [<90000000048e3334>] rcu_cpu_starting+0x214/0x280 [<90000000047bd568>] tlb_init+0x248/0x528 [<90000000047a4c44>] per_cpu_trap_init+0x124/0x160 [<90000000047a19f4>] cpu_probe+0x494/0xa00 [<90000000047b551c>] start_secondary+0x3c/0xc0 [<9000000005b66134>] smpboot_entry+0x50/0x58
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| Debian:11 | linux | 0 | No fix |
| Debian:12 | linux | 0 | 6.1.82-1 |
| Debian:13 | linux | 0 | 6.7.7-1 |
| Linux | Kernel | 5.19.0 | 6.1.80 |
| Ubuntu:16.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:18.04:LTS | linux-aws-5.0 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-aws-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-azure | 0 | No fix |
| Ubuntu:18.04:LTS | linux-azure-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-azure-edge | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gcp | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gcp-5.3 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gke-4.15 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gke-5.4 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-gkeop-5.4 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-hwe | 0 | No fix |
| Ubuntu:18.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:18.04:LTS | linux-oem | 0 | No fix |
| Ubuntu:18.04:LTS | linux-oracle-5.0 | 0 | No fix |
| Ubuntu:18.04:LTS | linux-oracle-5.3 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-aws-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-aws-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-aws-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-azure-fde | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gcp-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gcp-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gcp-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gke | 0 | No fix |
| Ubuntu:20.04:LTS | linux-gke-5.15 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-hwe-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-hwe-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-hwe-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-intel-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.10 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.14 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oem-5.6 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oracle-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oracle-5.13 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-oracle-5.8 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-raspi2 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-riscv | 0 | No fix |
| Ubuntu:20.04:LTS | linux-riscv-5.11 | 0 | No fix |
| Ubuntu:20.04:LTS | linux-riscv-5.8 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-allwinner-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-aws-6.8 | 0 | 6.8.0-1009.9~22.04.2 |
| Ubuntu:22.04:LTS | linux-azure-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-6.8 | 0 | 6.8.0-1008.8~22.04.1 |
| Ubuntu:22.04:LTS | linux-azure-fde-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-azure-fde-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-gcp-6.8 | 0 | 6.8.0-1010.11~22.04.1 |
| Ubuntu:22.04:LTS | linux-hwe-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-hwe-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-hwe-6.8 | 0 | 6.8.0-38.38~22.04.1 |
| Ubuntu:22.04:LTS | linux-intel-iot-realtime | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-lowlatency-hwe-6.8 | 0 | 6.8.0-38.38.1~22.04.2 |
| Ubuntu:22.04:LTS | linux-nvidia-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-nvidia-6.8 | 0 | 6.8.0-1008.8~22.04.1 |
| Ubuntu:22.04:LTS | linux-nvidia-tegra | 0 | No fix |
| Ubuntu:22.04:LTS | linux-nvidia-tegra-igx | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oem-5.17 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oem-6.0 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oem-6.1 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-oracle-6.8 | 0 | 6.8.0-1006.6~22.04.3 |
| Ubuntu:22.04:LTS | linux-realtime | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-riscv-6.8 | 0 | 6.8.0-38.38.1~22.04.1 |
| Ubuntu:22.04:LTS | linux-starfive-5.19 | 0 | No fix |
| Ubuntu:22.04:LTS | linux-starfive-6.2 | 0 | No fix |
| Ubuntu:22.04:LTS:for:NVIDIA:BlueField | linux-bluefield | 0 | No fix |
| Ubuntu:24.04:LTS | linux-gkeop | 0 | 6.8.0-1001.3 |
| Ubuntu:24.04:LTS | linux-nvidia | 0 | 6.8.0-1007.7 |
| Ubuntu:24.04:LTS | linux-nvidia-lowlatency | 0 | 6.8.0-1009.9.1 |
| Ubuntu:24.04:LTS | linux-oem-6.11 | 0 | 6.11.0-1007.7 |
| Ubuntu:24.04:LTS | linux-oem-6.8 | 0 | 6.8.0-1003.3 |
| Ubuntu:24.04:LTS | linux-raspi-realtime | 0 | No fix |
| Ubuntu:24.04:LTS | linux-realtime | 0 | 6.8.0-1008.19 |
| Ubuntu:24.10 | linux-realtime | 0 | 6.11.0-1001.1 |
| Ubuntu:25.10 | linux-azure-fde | 0 | No fix |
| Ubuntu:Pro:16.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-aws-5.0 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-aws-5.3 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-azure | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-azure-5.3 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-azure-edge | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gcp | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gcp-5.3 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gke-4.15 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gke-5.4 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-gkeop-5.4 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-hwe | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-hwe-edge | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-oem | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-oracle-5.0 | 0 | No fix |
| Ubuntu:Pro:18.04:LTS | linux-oracle-5.3 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-aws-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-aws-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-aws-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-azure-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-azure-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-azure-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-azure-fde | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gcp-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gcp-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gcp-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gke | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-gke-5.15 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-hwe-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-hwe-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-hwe-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-intel-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-nvidia-tegra-5.15 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oem-5.10 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oem-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oem-5.14 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oem-5.6 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oracle-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oracle-5.13 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-oracle-5.8 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-raspi2 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-riscv | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-riscv-5.11 | 0 | No fix |
| Ubuntu:Pro:20.04:LTS | linux-riscv-5.8 | 0 | No fix |
| Ubuntu:Pro:22.04:LTS:Realtime:Kernel | linux-intel-iot-realtime | 0 | No fix |
| Ubuntu:Pro:22.04:LTS:Realtime:Kernel | linux-realtime | 0 | No fix |
| Ubuntu:Pro:24.04:LTS:Realtime:Kernel | linux-raspi-realtime | 0 | 6.8.0-2002.2 |
| Ubuntu:Pro:FIPS-preview:22.04:LTS | linux-aws-fips | 0 | No fix |
| Ubuntu:Pro:FIPS-preview:22.04:LTS | linux-azure-fips | 0 | No fix |
| Ubuntu:Pro:FIPS-preview:22.04:LTS | linux-fips | 0 | No fix |
| Ubuntu:Pro:FIPS-preview:22.04:LTS | linux-gcp-fips | 0 | No fix |
| Ubuntu:Pro:FIPS-updates:22.04:LTS | linux-aws-fips | 0 | No fix |
| Ubuntu:Pro:FIPS-updates:22.04:LTS | linux-azure-fips | 0 | No fix |
| Ubuntu:Pro:FIPS-updates:22.04:LTS | linux-fips | 0 | No fix |
| Ubuntu:Pro:FIPS-updates:22.04:LTS | linux-gcp-fips | 0 | No fix |
| Ubuntu:Pro:Realtime:24.04:LTS | linux-raspi-realtime | 0 | 6.8.0-2002.2 |
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