powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.
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: 4 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: Avoid nmi_enter/nmi_exit in real mode interrupt. nmi_enter()/nmi_exit() touches per cpu variables which can lead to kernel crash when invoked during real mode interrupt handling (e.g. early HMI/MCE interrupt handler) if percpu allocation comes from vmalloc area. Early HMI/MCE handlers are called through DEFINE_INTERRUPT_HANDLER_NMI() wrapper which invokes nmi_enter/nmi_exit calls. We don't see any issue when percpu allocation is from the embedded first chunk. However with CONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there are chances where percpu allocation can come from the vmalloc area. With kernel command line "percpu_alloc=page" we can force percpu allocation to come from vmalloc area and can see kernel crash in machine_check_early: [ 1.215714] NIP [c000000000e49eb4] rcu_nmi_enter+0x24/0x110 [ 1.215717] LR [c0000000000461a0] machine_check_early+0xf0/0x2c0 [ 1.215719] --- interrupt: 200 [ 1.215720] [c000000fffd73180] [0000000000000000] 0x0 (unreliable) [ 1.215722] [c000000fffd731b0] [0000000000000000] 0x0 [ 1.215724] [c000000fffd73210] [c000000000008364] machine_check_early_common+0x134/0x1f8 Fix this by avoiding use of nmi_enter()/nmi_exit() in real mode if percpu first chunk is not embedded.
Why it matters now
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
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 5.10 and later | 5.10.224, 5.15.165, 6.1.98, 6.6.39, 6.9.9, 6.10 | Patch available | CNA |
- Linux VendorLinux Affected 5.10 and later Fixed in 5.10.224, 5.15.165, 6.1.98, 6.6.39, 6.9.9, 6.10 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 5.10 to before 5.10.224; 5.11 to before 5.15.165; 5.16 to before 6.1.98; 6.2 to before 6.6.39; 6.7 to before 6.9.9 | Vulnerable | Linux |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 5.10 to before 5.10.224; 5.11 to before 5.15.165; 5.16 to before 6.1.98; 6.2 to before 6.6.39; 6.7 to before 6.9.9 Vulnerable ·Linux
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.10.224, 5.15.165, 6.1.98, 6.6.39, 6.9.9, 6.10
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Enterprise Linux 6 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 7 | Affected | No fix planned: Out of support scope |
| Red Hat Enterprise Linux 8 | Affected | No fix yet: Fix deferred |
| Red Hat Enterprise Linux 9 | Affected | No fix yet: Fix deferred |
Timeline
- 2026-10-02 Threatist record created from CVE-2024-42126
- 2026-10-03 Alias added: GHSA-vx4j-2p26-q8m4
References
Patch 6
- https://git.kernel.org/stable/c/fb6675db04c4b79883373edc578d5df7bbc84848
- https://git.kernel.org/stable/c/e2afb26615adf6c3ceaaa7732aa839bcd587a057
- https://git.kernel.org/stable/c/8d3f83dfb23674540c827a8d65fba20aa300b252
- https://git.kernel.org/stable/c/0f37946c62c48a907625348cbc720a7a0c547d1e
- https://git.kernel.org/stable/c/2c78c9411e685dbc9eac8c2845111b03501975b8
- https://git.kernel.org/stable/c/0db880fc865ffb522141ced4bfa66c12ab1fbb70
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Sources
- CVE-2024-42126 · CVE Program
- CVE-2024-42126 · NVD
- FIRST EPSS
- GHSA-vx4j-2p26-q8m4 · GitHub Advisory Database · CC BY 4.0
- CVE-2024-42126 · Red Hat security data · CC BY 4.0
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