CVE-2025-68211

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

ksm: use range-walk function to jump over holes in scan_get_next_rmap_item

Currently, scan_get_next_rmap_item() walks every page address in a VMA to

locate mergeable pages. This becomes highly inefficient when scanning

large virtual memory areas that contain mostly unmapped regions, causing

ksmd to use large amount of cpu without deduplicating much pages.

This patch replaces the per-address lookup with a range walk using

walk_page_range(). The range walker allows KSM to skip over entire

unmapped holes in a VMA, avoiding unnecessary lookups. This problem was

previously discussed in [1].

Consider the following test program which creates a 32 TiB mapping in the

virtual address space but only populates a single page:

#include <unistd.h>

#include <stdio.h>

#include <sys/mman.h>

/* 32 TiB */

const size_t size = 32ul * 1024 * 1024 * 1024 * 1024;

int main() {

char *area = mmap(NULL, size, PROT_READ | PROT_WRI

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References