CVE-2025-40230
In the Linux kernel, the following vulnerability has been resolved:
mm: prevent poison consumption when splitting THP
When performing memory error injection on a THP (Transparent Huge Page) mapped to userspace on an x86 server, the kernel panics with the following trace. The expected behavior is to terminate the affected process instead of panicking the kernel, as the x86 Machine Check code can recover from an in-userspace #MC.
The root cause of this panic is that handling a memory failure triggered by an in-userspace #MC necessitates splitting the THP.
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The splitting process employs a mechanism, implemented in try_to_map_unused_to_zeropage(), which reads the pages in the THP to identify zero-filled pages. However, reading the pages in the THP results in a second in-kernel #MC, occurring before the initial memory_failure() completes, ultimately leading to a kernel panic. See the kernel panic call trace on the two #MCs.
[2] Call folio_set_has_hwpoisoned() before try_to_split_thp_page().
[3] Pass the RMP_USE_SHARED_ZEROPAGE remap flag to remap_page().
[4] Try to map the unused THP to zeropage.
[5] Re-access pages in the hw-poisoned THP in the kernel.
[6] Triggered in-kernel, leading to a panic kernel.
In Step[2], memory_failure() sets the poisoned flag on the page in the THP by TestSetPageHWPoison() before calling try_to_split_thp_page().
As suggested by David Hildenbrand, fix this panic by not accessing to the poisoned page in the THP during zeropage identification, while continuing to scan unaffected pages in the THP for possible zeropage mapping. This prevents a second in-kernel #MC that would cause kernel panic in Step[4].
Thanks to Andrew Zaborowski for his initial work on fixing this issue.
Detalles técnicos trazas, registros y código del informe original
mce: [Hardware Error]: CPU 0: Machine Check Exception: f Bank 3: bd80000000070134
mce: [Hardware Error]: RIP 10:<ffffffff8372f8bc> {memchr_inv+0x4c/0xf0}
mce: [Hardware Error]: TSC afff7bbff88a ADDR 1d301b000 MISC 80 PPIN 1e741e77539027db
mce: [Hardware Error]: PROCESSOR 0:d06d0 TIME 1758093249 SOCKET 0 APIC 0 microcode 80000320
mce: [Hardware Error]: Run the above through 'mcelog --ascii'
mce: [Hardware Error]: Machine check: Data load in unrecoverable area of kernel
Kernel panic - not syncing: Fatal local machine check
First Machine Check occurs // [1]
memory_failure() // [2]
try_to_split_thp_page()
split_huge_page()
split_huge_page_to_list_to_order()
__folio_split() // [3]
remap_page()
remove_migration_ptes()
remove_migration_pte()
try_to_map_unused_to_zeropage() // [4]
memchr_inv() // [5]
Second Machine Check occurs // [6]
Kernel panic
[1] Triggered by accessing a hardware-poisoned THP in userspace, which is
typically recoverable by terminating the affected process.CVSS
NVD no ha asignado puntuación CVSS a esta CVE (habitual desde el cambio de política de abril de 2026).
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.21%
- Percentil entre todas las CVEs puntuadas: 11
- Fecha de la puntuación: 6/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
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{
"id": "CVE-2025-40230",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "b1f202060afeb7fcb98473929d26fd3d2093b067",
"lessThan": "6fc0a7c99e973a50018c8b4be34914a1b5c7b383",
"versionType": "git"
},
{
"status": "affected",
"version": "b1f202060afeb7fcb98473929d26fd3d2093b067",
"lessThan": "92acf4b04f255d2f0f6770bb0d0a208d8ffb2b77",
"versionType": "git"
},
{
"status": "affected",
"version": "b1f202060afeb7fcb98473929d26fd3d2093b067",
"lessThan": "841a8bfcbad94bb1ba60f59ce34f75259074ae0d",
"versionType": "git"
}
],
"programFiles": [
"mm/huge_memory.c",
"mm/migrate.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.12"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.12",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.56",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.17.6",
"versionType": "semver",
"lessThanOrEqual": "6.17.*"
},
{
"status": "unaffected",
"version": "6.18",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"mm/huge_memory.c",
"mm/migrate.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2025-12-04T16:16:15.720",
"references": [
{
"url": "https://git.kernel.org/stable/c/6fc0a7c99e973a50018c8b4be34914a1b5c7b383",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/841a8bfcbad94bb1ba60f59ce34f75259074ae0d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/92acf4b04f255d2f0f6770bb0d0a208d8ffb2b77",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Deferred",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: prevent poison consumption when splitting THP\n\nWhen performing memory error injection on a THP (Transparent Huge Page)\nmapped to userspace on an x86 server, the kernel panics with the following\ntrace. The expected behavior is to terminate the affected process instead\nof panicking the kernel, as the x86 Machine Check code can recover from an\nin-userspace #MC.\n\n mce: [Hardware Error]: CPU 0: Machine Check Exception: f Bank 3: bd80000000070134\n mce: [Hardware Error]: RIP 10:<ffffffff8372f8bc> {memchr_inv+0x4c/0xf0}\n mce: [Hardware Error]: TSC afff7bbff88a ADDR 1d301b000 MISC 80 PPIN 1e741e77539027db\n mce: [Hardware Error]: PROCESSOR 0:d06d0 TIME 1758093249 SOCKET 0 APIC 0 microcode 80000320\n mce: [Hardware Error]: Run the above through 'mcelog --ascii'\n mce: [Hardware Error]: Machine check: Data load in unrecoverable area of kernel\n Kernel panic - not syncing: Fatal local machine check\n\nThe root cause of this panic is that handling a memory failure triggered\nby an in-userspace #MC necessitates splitting the THP. The splitting\nprocess employs a mechanism, implemented in\ntry_to_map_unused_to_zeropage(), which reads the pages in the THP to\nidentify zero-filled pages. However, reading the pages in the THP results\nin a second in-kernel #MC, occurring before the initial memory_failure()\ncompletes, ultimately leading to a kernel panic. See the kernel panic\ncall trace on the two #MCs.\n\n First Machine Check occurs // [1]\n memory_failure() // [2]\n try_to_split_thp_page()\n split_huge_page()\n split_huge_page_to_list_to_order()\n __folio_split() // [3]\n remap_page()\n remove_migration_ptes()\n remove_migration_pte()\n try_to_map_unused_to_zeropage() // [4]\n memchr_inv() // [5]\n Second Machine Check occurs // [6]\n Kernel panic\n\n[1] Triggered by accessing a hardware-poisoned THP in userspace, which is\n typically recoverable by terminating the affected process.\n\n[2] Call folio_set_has_hwpoisoned() before try_to_split_thp_page().\n\n[3] Pass the RMP_USE_SHARED_ZEROPAGE remap flag to remap_page().\n\n[4] Try to map the unused THP to zeropage.\n\n[5] Re-access pages in the hw-poisoned THP in the kernel.\n\n[6] Triggered in-kernel, leading to a panic kernel.\n\nIn Step[2], memory_failure() sets the poisoned flag on the page in the THP\nby TestSetPageHWPoison() before calling try_to_split_thp_page().\n\nAs suggested by David Hildenbrand, fix this panic by not accessing to the\npoisoned page in the THP during zeropage identification, while continuing\nto scan unaffected pages in the THP for possible zeropage mapping. This\nprevents a second in-kernel #MC that would cause kernel panic in Step[4].\n\nThanks to Andrew Zaborowski for his initial work on fixing this issue."
}
],
"lastModified": "2026-06-17T09:21:29.747",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}