CVE-2025-39941
Full vulnerability record from the local CVENow database.
Description
In the Linux kernel, the following vulnerability has been resolved: zram: fix slot write race condition Parallel concurrent writes to the same zram index result in leaked zsmalloc handles. Schematically we can have something like this: CPU0 CPU1 zram_slot_lock() zs_free(handle) zram_slot_lock() zram_slot_lock() zs_free(handle) zram_slot_lock() compress compress handle = zs_malloc() handle = zs_malloc() zram_slot_lock zram_set_handle(handle) zram_slot_lock zram_slot_lock zram_set_handle(handle) zram_slot_lock Either CPU0 or CPU1 zsmalloc handle will leak because zs_free() is done too early. In fact, we need to reset zram entry right before we set its new handle, all under the same slot lock scope.
Severity
MEDIUM
CVSS score
4.7
(v3.1)
Vulnerability status
Modified
Source identifier
416baaa9-dc9f-4396-8d5f-8c081fb06d67
Published
2025-10-04 08:15:47.103000
Last modified
2026-10-19 21:10:00.160000
View original CVE JSON
{
"id": "CVE-2025-39941",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"published": "2025-10-04T08:15:47.103",
"lastModified": "2026-10-19T21:10:00.160",
"vulnStatus": "Modified",
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{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nzram: fix slot write race condition\n\nParallel concurrent writes to the same zram index result in leaked\nzsmalloc handles. Schematically we can have something like this:\n\nCPU0 CPU1\nzram_slot_lock()\nzs_free(handle)\nzram_slot_lock()\n\t\t\t\tzram_slot_lock()\n\t\t\t\tzs_free(handle)\n\t\t\t\tzram_slot_lock()\n\ncompress\t\t\tcompress\nhandle = zs_malloc()\t\thandle = zs_malloc()\nzram_slot_lock\nzram_set_handle(handle)\nzram_slot_lock\n\t\t\t\tzram_slot_lock\n\t\t\t\tzram_set_handle(handle)\n\t\t\t\tzram_slot_lock\n\nEither CPU0 or CPU1 zsmalloc handle will leak because zs_free() is done\ntoo early. In fact, we need to reset zram entry right before we set its\nnew handle, all under the same slot lock scope."
},
{
"lang": "es",
"value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nzram: corregir condición de carrera de escritura de slot\n\nLas escrituras concurrentes paralelas al mismo índice de zram resultan en handles de zsmalloc filtrados. Esquemáticamente podemos tener algo como esto:\n\nCPU0 CPU1\nzram_slot_lock()\nzs_free(handle)\nzram_slot_lock()\n\t\t\t\tzram_slot_lock()\n\t\t\t\tzs_free(handle)\n\t\t\t\tzram_slot_lock()\n\ncompress\t\t\tcompress\nhandle = zs_malloc()\t\thandle = zs_malloc()\nzram_slot_lock\nzram_set_handle(handle)\nzram_slot_lock\n\t\t\t\tzram_slot_lock\n\t\t\t\tzram_set_handle(handle)\n\t\t\t\tzram_slot_lock\n\nEl handle de zsmalloc de la CPU0 o la CPU1 se filtrará porque zs_free() se ejecuta demasiado pronto. De hecho, necesitamos restablecer la entrada de zram justo antes de establecer su nuevo handle, todo bajo el mismo ámbito de bloqueo de slot."
}
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"source": "[email protected]",
"type": "Primary",
"description": [
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