CVE-2026-74599
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: mm/ptdump: always stabilise against page table freeing using init_mm Previous commits have established the invariant that kernel page table freeing is performed while an mmap read lock on init_mm is held, which fixes races between ptdump and kernel page table freeing over init_mm. However, x86 and arm64 can perform a ptdump over an mm other than init_mm via ptdump_walk_pgd() and since kernel memory ranges are shared across non-kernel mm's, this means that the race still exists for these cases. Fix this by acquiring a nested mmap write lock for init_mm in ptdump_walk_pgd(). This is safe as we take this after mmap write locking the mm, and nothing acquires the init_mm lock first before locking an arbitrary mm, so no deadlock is possible. Also update walk_page_range_debug() to assert that init_mm is write locked, add a comment explaining why and remove some redundant code, and eliminate the unnecessary and confusing invocation of walk_kernel_page_table_range(). We can safely remove the non-NULL check for walk.mm, as the mmap lock asserts would NULL pointer deref if it was (and of course no callers do this). The first point at which ptdump can race kernel page table freeing is commit b6bdb7517c3d ("mm/vmalloc: add interfaces to free unmapped page table"), so we target this in the Fixes tag.
Severity
Not scored
CVSS score
Not available
Vulnerability status
Received
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2026-08-22 16:16:32.303000
Last modified
2026-10-30 13:20:02.923000
View original CVE JSON
{
"id": "CVE-2026-74599",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2026-08-22T16:16:32.303",
"lastModified": "2026-10-30T13:20:02.923",
"vulnStatus": "Received",
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/ptdump: always stabilise against page table freeing using init_mm\n\nPrevious commits have established the invariant that kernel page table\nfreeing is performed while an mmap read lock on init_mm is held, which\nfixes races between ptdump and kernel page table freeing over init_mm.\n\nHowever, x86 and arm64 can perform a ptdump over an mm other than init_mm\nvia ptdump_walk_pgd() and since kernel memory ranges are shared across\nnon-kernel mm's, this means that the race still exists for these cases.\n\nFix this by acquiring a nested mmap write lock for init_mm in\nptdump_walk_pgd().\n\nThis is safe as we take this after mmap write locking the mm, and nothing\nacquires the init_mm lock first before locking an arbitrary mm, so no\ndeadlock is possible.\n\nAlso update walk_page_range_debug() to assert that init_mm is write\nlocked, add a comment explaining why and remove some redundant code, and\neliminate the unnecessary and confusing invocation of\nwalk_kernel_page_table_range().\n\nWe can safely remove the non-NULL check for walk.mm, as the mmap lock\nasserts would NULL pointer deref if it was (and of course no callers do\nthis).\n\nThe first point at which ptdump can race kernel page table freeing is\ncommit b6bdb7517c3d (\"mm/vmalloc: add interfaces to free unmapped page\ntable\"), so we target this in the Fixes tag."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nmm/ptdump: siempre estabilizar contra la liberación de tablas de páginas usando init_mm\n\nCommits anteriores han establecido el invariante de que la liberación de tablas de páginas del kernel se realiza mientras se mantiene un bloqueo de lectura mmap en init_mm, lo que corrige condiciones de carrera entre ptdump y la liberación de tablas de páginas del kernel sobre init_mm.\n\nSin embargo, x86 y arm64 pueden realizar un ptdump sobre un mm distinto de init_mm a través de ptdump_walk_pgd() y dado que los rangos de memoria del kernel se comparten entre mm's que no son del kernel, esto significa que la condición de carrera aún existe para estos casos.\n\nSolucione esto adquiriendo un bloqueo de escritura mmap anidado para init_mm en ptdump_walk_pgd().\n\nEsto es seguro ya que lo tomamos después de bloquear en escritura mmap el mm, y nada adquiere el bloqueo de init_mm primero antes de bloquear un mm arbitrario, por lo que no es posible un interbloqueo.\n\nTambién actualice walk_page_range_debug() para afirmar que init_mm está bloqueado en escritura, agregue un comentario explicando por qué y elimine código redundante, y elimine la invocación innecesaria y confusa de walk_kernel_page_table_range().\n\nPodemos eliminar de forma segura la comprobación de no-NULL para walk.mm, ya que las aserciones del bloqueo mmap desreferenciarían un puntero NULL si lo fuera (y por supuesto, ningún llamador hace esto).\n\nEl primer punto en el que ptdump puede competir con la liberación de tablas de páginas del kernel es el commit b6bdb7517c3d ('mm/vmalloc: add interfaces to free unmapped page table'), por lo que apuntamos a esto en la etiqueta Fixes."
}
],
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "unaffected",
"programFiles": [
"mm/pagewalk.c",
"mm/ptdump.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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{
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"lessThan": "3c0391b9a774cc0854f3152e484a9d4835b12b40",
"versionType": "git",
"status": "affected"
},
{
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"status": "affected"
},
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"versionType": "git",
"status": "affected"
},
{
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{
"version": "31895cfd79564111cdd5a9f48c5d491ae26a238e",
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{
"version": "9c7f7bdb1932f8c1e5f80d32c717184701afe701",
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{
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{
"version": "0454e2fad9306961540ee7e84da47a8e345b7d22",
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},
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},
{
"version": "4.9.91",
"lessThan": "4.10",
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"status": "affected"
},
{
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},
{
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"versionType": "semver",
"status": "affected"
}
]
},
{
"vendor": "Linux",
"product": "Linux",
"defaultStatus": "affected",
"programFiles": [
"mm/pagewalk.c",
"mm/ptdump.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"versions": [
{
"version": "4.16",
"status": "affected"
},
{
"version": "0",
"lessThan": "4.16",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.10.266",
"lessThanOrEqual": "5.10.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "5.15.217",
"lessThanOrEqual": "5.15.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.1.191",
"lessThanOrEqual": "6.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.6.153",
"lessThanOrEqual": "6.6.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.12.105",
"lessThanOrEqual": "6.12.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "6.18.45",
"lessThanOrEqual": "6.18.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.1.9",
"lessThanOrEqual": "7.1.*",
"versionType": "semver",
"status": "unaffected"
},
{
"version": "7.2",
"lessThanOrEqual": "*",
"versionType": "original_commit_for_fix",
"status": "unaffected"
}
]
}
]
}
],
"metrics": {},
"references": [
{
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"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
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}