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CVE-2025-68211— ksm: use range-walk function to jump over holes in scan_get_next_rmap_item

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ksm扫描VMA时未跳过未映射区域，可能导致CPU资源浪费。

AI Predicted 5.9 Difficulty: Moderate EPSS 0.15% · P4

Possible ATT&CK Techniques 1 AI

T1496 · Resource Hijacking

Affected Version Matrix 16

VendorProduct Version RangeStatus
Linux Linux 31dbd01f314364b70c2e026a5793a29a4da8a9dc< 220cb3e425e17587f560335924cba9f16a842c64 affected
31dbd01f314364b70c2e026a5793a29a4da8a9dc< 10644e8839544dd5699c03c8fb1aeeefc41602fd affected
31dbd01f314364b70c2e026a5793a29a4da8a9dc< 67137b715b7db28d82e4ed07a7092c2fa6ba7adb affected
31dbd01f314364b70c2e026a5793a29a4da8a9dc< 9c2f8a9b68024e5ebb4813665845ec0a95f2eac3 affected
31dbd01f314364b70c2e026a5793a29a4da8a9dc< 74f78421c925b6d17695566f0c5941de57fd44b3 affected
31dbd01f314364b70c2e026a5793a29a4da8a9dc< f62973e0767e4fcd6799087787fca08ca2a85b8c affected
31dbd01f314364b70c2e026a5793a29a4da8a9dc< f5548c318d6520d4fa3c5ed6003eeb710763cbc5 affected
2.6.32 affected
… +8 more rows
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I. Basic Information for CVE-2025-68211

Vulnerability Information
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Vulnerability Title
ksm: use range-walk function to jump over holes in scan_get_next_rmap_item
Source: CVE Program / CVE List V5
Vulnerability 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_WRITE, MAP_NORESERVE | MAP_PRIVATE | MAP_ANON, -1, 0); if (area == MAP_FAILED) { perror("mmap() failed\n"); return -1; } /* Populate a single page such that we get an anon_vma. */ *area = 0; /* Enable KSM. */ madvise(area, size, MADV_MERGEABLE); pause(); return 0; } $ ./ksm-sparse & $ echo 1 > /sys/kernel/mm/ksm/run Without this patch ksmd uses 100% of the cpu for a long time (more then 1 hour in my test machine) scanning all the 32 TiB virtual address space that contain only one mapped page. This makes ksmd essentially deadlocked not able to deduplicate anything of value. With this patch ksmd walks only the one mapped page and skips the rest of the 32 TiB virtual address space, making the scan fast using little cpu.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ksm扫描VMA时未跳过未映射区域，可能导致CPU资源浪费。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 31dbd01f314364b70c2e026a5793a29a4da8a9dc ~ 220cb3e425e17587f560335924cba9f16a842c64 -
Linux Linux 2.6.32 -

II. Public POCs for CVE-2025-68211

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III. Intelligence Information for CVE-2025-68211

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Other References for CVE-2025-68211 (3)

Same Patch Batch · Linux · 2025-12-16 · 156 CVEs total

CVE-2025-68284 9.8 CRITICAL libceph: prevent potential out-of-bounds writes in handle_auth_session_key()
CVE-2025-40350 9.8 CRITICAL net/mlx5e: RX, Fix generating skb from non-linear xdp_buff for striding RQ
CVE-2025-68263 9.8 CRITICAL ksmbd: ipc: fix use-after-free in ipc_msg_send_request
CVE-2025-68301 9.8 CRITICAL net: atlantic: fix fragment overflow handling in RX path
CVE-2025-68192 9.8 CRITICAL net: usb: qmi_wwan: initialize MAC header offset in qmimux_rx_fixup
CVE-2025-68285 9.8 CRITICAL libceph: fix potential use-after-free in have_mon_and_osd_map()
CVE-2025-68315 9.8 CRITICAL f2fs: fix to detect potential corrupted nid in free_nid_list
CVE-2025-68255 8.8 HIGH staging: rtl8723bs: fix stack buffer overflow in OnAssocReq IE parsing
CVE-2025-68256 8.8 HIGH staging: rtl8723bs: fix out-of-bounds read in rtw_get_ie() parser
CVE-2025-68226 8.8 HIGH smb: client: fix incomplete backport in cfids_invalidation_worker()
CVE-2025-68304 8.8 HIGH Bluetooth: hci_core: lookup hci_conn on RX path on protocol side
CVE-2025-68314 8.8 HIGH drm/msm: make sure last_fence is always updated
CVE-2025-40362 8.8 HIGH ceph: fix multifs mds auth caps issue
CVE-2025-68250 8.2 HIGH hung_task: fix warnings caused by unaligned lock pointers
CVE-2025-68183 7.8 HIGH ima: don't clear IMA_DIGSIG flag when setting or removing non-IMA xattr
CVE-2025-68212 7.8 HIGH fs: Fix uninitialized 'offp' in statmount_string()
CVE-2025-68208 7.8 HIGH bpf: account for current allocated stack depth in widen_imprecise_scalars()
CVE-2025-68207 7.8 HIGH drm/xe/guc: Synchronize Dead CT worker with unbind
CVE-2025-68303 7.8 HIGH platform/x86: intel: punit_ipc: fix memory corruption
CVE-2025-68181 7.8 HIGH drm/radeon: Remove calls to drm_put_dev()

Showing top 20 of 156 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-68211

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