CVE-2025-39899
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: mm/userfaultfd: fix kmap_local LIFO ordering for CONFIG_HIGHPTE With CONFIG_HIGHPTE on 32-bit ARM, move_pages_pte() maps PTE pages using kmap_local_page(), which requires unmapping in Last-In-First-Out order. The current code maps dst_pte first, then src_pte, but unmaps them in the same order (dst_pte, src_pte), violating the LIFO requirement. This causes the warning in kunmap_local_indexed(): WARNING: CPU: 0 PID: 604 at mm/highmem.c:622 kunmap_local_indexed+0x178/0x17c addr \!= __fix_to_virt(FIX_KMAP_BEGIN + idx) Fix this by reversing the unmap order to respect LIFO ordering. This issue follows the same pattern as similar fixes: - commit eca6828403b8 ("crypto: skcipher - fix mismatch between mapping and unmapping order") - commit 8cf57c6df818 ("nilfs2: eliminate staggered calls to kunmap in nilfs_rename") Both of which addressed the same fundamental requirement that kmap_local operations must follow LIFO ordering.
Severity
MEDIUM
CVSS score
5.5
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-10-01 08:15:32.620000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON
{
"id": "CVE-2025-39899",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-10-01T08:15:32.620",
"lastModified": "2026-10-19T21:10:00.160",
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"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/userfaultfd: fix kmap_local LIFO ordering for CONFIG_HIGHPTE\n\nWith CONFIG_HIGHPTE on 32-bit ARM, move_pages_pte() maps PTE pages using\nkmap_local_page(), which requires unmapping in Last-In-First-Out order.\n\nThe current code maps dst_pte first, then src_pte, but unmaps them in the\nsame order (dst_pte, src_pte), violating the LIFO requirement. This\ncauses the warning in kunmap_local_indexed():\n\n WARNING: CPU: 0 PID: 604 at mm/highmem.c:622 kunmap_local_indexed+0x178/0x17c\n addr \\!= __fix_to_virt(FIX_KMAP_BEGIN + idx)\n\nFix this by reversing the unmap order to respect LIFO ordering.\n\nThis issue follows the same pattern as similar fixes:\n- commit eca6828403b8 (\"crypto: skcipher - fix mismatch between mapping and unmapping order\")\n- commit 8cf57c6df818 (\"nilfs2: eliminate staggered calls to kunmap in nilfs_rename\")\n\nBoth of which addressed the same fundamental requirement that kmap_local\noperations must follow LIFO ordering."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nmm/userfaultfd: corregir el orden LIFO de kmap_local para CONFIG_HIGHPTE\n\nCon CONFIG_HIGHPTE en ARM de 32 bits, move_pages_pte() mapea páginas PTE usando kmap_local_page(), lo que requiere desmapear en orden Último en Entrar, Primero en Salir.\n\nEl código actual mapea dst_pte primero, luego src_pte, pero los desmapea en el mismo orden (dst_pte, src_pte), violando el requisito LIFO. Esto causa la advertencia en kunmap_local_indexed():\n\n WARNING: CPU: 0 PID: 604 at mm/highmem.c:622 kunmap_local_indexed+0x178/0x17c\n addr \\!= __fix_to_virt(FIX_KMAP_BEGIN + idx)\n\nCorregir esto invirtiendo el orden de desmapeo para respetar el orden LIFO.\n\nEste problema sigue el mismo patrón que correcciones similares:\n- commit eca6828403b8 ('crypto: skcipher - corregir la falta de coincidencia entre el orden de mapeo y desmapeo')\n- commit 8cf57c6df818 ('nilfs2: eliminar llamadas escalonadas a kunmap en nilfs_rename')\n\nAmbos abordaron el mismo requisito fundamental de que las operaciones de kmap_local deben seguir el orden LIFO."
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