{"id":"CVE-2024-42126","summary":"powerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.","details":"In the Linux kernel, the following vulnerability has been resolved:\n\npowerpc: Avoid nmi_enter/nmi_exit in real mode interrupt.\n\nnmi_enter()/nmi_exit() touches per cpu variables which can lead to kernel\ncrash when invoked during real mode interrupt handling (e.g. early HMI/MCE\ninterrupt handler) if percpu allocation comes from vmalloc area.\n\nEarly HMI/MCE handlers are called through DEFINE_INTERRUPT_HANDLER_NMI()\nwrapper which invokes nmi_enter/nmi_exit calls. We don't see any issue when\npercpu allocation is from the embedded first chunk. However with\nCONFIG_NEED_PER_CPU_PAGE_FIRST_CHUNK enabled there are chances where percpu\nallocation can come from the vmalloc area.\n\nWith kernel command line \"percpu_alloc=page\" we can force percpu allocation\nto come from vmalloc area and can see kernel crash in machine_check_early:\n\n[    1.215714] NIP [c000000000e49eb4] rcu_nmi_enter+0x24/0x110\n[    1.215717] LR [c0000000000461a0] machine_check_early+0xf0/0x2c0\n[    1.215719] --- interrupt: 200\n[    1.215720] [c000000fffd73180] [0000000000000000] 0x0 (unreliable)\n[    1.215722] [c000000fffd731b0] [0000000000000000] 0x0\n[    1.215724] [c000000fffd73210] [c000000000008364] machine_check_early_common+0x134/0x1f8\n\nFix this by avoiding use of nmi_enter()/nmi_exit() in real mode if percpu\nfirst chunk is not embedded.","modified":"2026-04-16T04:39:55.824382189Z","published":"2024-07-30T07:46:23.179Z","related":["SUSE-SU-2024:3190-1","SUSE-SU-2024:3194-1","SUSE-SU-2024:3195-1","SUSE-SU-2024:3209-1","SUSE-SU-2024:3227-1","SUSE-SU-2024:3383-1","SUSE-SU-2024:3408-1","SUSE-SU-2024:3483-1","SUSE-SU-2025:20044-1","SUSE-SU-2025:20047-1"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/42xxx/CVE-2024-42126.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0db880fc865ffb522141ced4bfa66c12ab1fbb70"},{"type":"WEB","url":"https://git.kernel.org/stable/c/0f37946c62c48a907625348cbc720a7a0c547d1e"},{"type":"WEB","url":"https://git.kernel.org/stable/c/2c78c9411e685dbc9eac8c2845111b03501975b8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/8d3f83dfb23674540c827a8d65fba20aa300b252"},{"type":"WEB","url":"https://git.kernel.org/stable/c/e2afb26615adf6c3ceaaa7732aa839bcd587a057"},{"type":"WEB","url":"https://git.kernel.org/stable/c/fb6675db04c4b79883373edc578d5df7bbc84848"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/42xxx/CVE-2024-42126.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-42126"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"eb553f16973ade990d05946af9ae191394712c8a"},{"fixed":"fb6675db04c4b79883373edc578d5df7bbc84848"},{"fixed":"e2afb26615adf6c3ceaaa7732aa839bcd587a057"},{"fixed":"8d3f83dfb23674540c827a8d65fba20aa300b252"},{"fixed":"0f37946c62c48a907625348cbc720a7a0c547d1e"},{"fixed":"2c78c9411e685dbc9eac8c2845111b03501975b8"},{"fixed":"0db880fc865ffb522141ced4bfa66c12ab1fbb70"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-42126.json"}}],"schema_version":"1.7.5"}