Unknown

CVE-2026-98939 — x86/mm: Drop unnecessary PMD page copy when freeing

In the Linux kernel, the following vulnerability has been resolved: x86/mm: Drop unnecessary PMD page copy when freeing On a box with a discrete GPU, lockdep reports a possible deadlock as soon as kswapd shrinks the TTM page pool. The immediate cause is an x86 commit that added an mmap_read_lock() to kernel page protection munging code. The huge vmap code holds the same lock over a GFP_KERNEL allocation, which is a no-no now that reclaim can take it. That allocation is in a page table *free* path and ends up being for dubious purposes[1]. Basically, it tries to avoid hardware setting Accessed=1 in page table entries that are unreachable by the hardware, a non-issue. Remove the PMD copy. Detach the original PMD page at the PUD, flush the mid-level caches, and free the PTE tables straight from the detached PMD page. With no allocation left, the locking issue is gone. Lockdep splat/analysis: WARNING: possible circular locking dependency detected 7.3.0-rc3-f6e7b42bf05b+ #183 Tainted: G U ------------------------------------------------------ kswapd0/269 is trying to acquire lock: ((init_mm).mmap_lock){++++}-{4:4}, at: change_page_attr_set_clr+0x29a/0x4a0 but task is already holding lock: (pool_shrink_rwsem){.+.+}-{4:4}, at: ttm_pool_shrink+0xb2/0x330 [ttm] Chain exists of: (init_mm).mmap_lock --> fs_reclaim --> pool_shrink_rwsem The cycle is built from three edges: 1) pool_shrink_rwsem -> (init_mm).mmap_lock The TTM shrinker restores the caching attribute of every page it frees, while holding pool_shrink_rwsem: ttm_pool_shrink() -> ttm_pool_dispose_list() -> ttm_pool_free_page() -> set_pages_wb() -> change_page_attr_set_clr() [ init_mm mmap read lock ] 2) fs_reclaim -> pool_shrink_rwsem The same shrinker, called from reclaim. 3) (init_mm).mmap_lock -> fs_reclaim ioremap() installing a huge PUD mapping over an existing PMD table: ioremap_page_range() -> vmap_range_noflush() -> vmap_try_huge_pud() [ init_mm mmap read lock ] -> pud_free_pmd_page() -> __get_free_page(GFP_KERNEL) [ enters reclaim ] [ dhansen: Lots of changelog munging/trimming and merged comments from my version of the fix. ]

Published Oct 23, 2026 · Updated Oct 23, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.2% (30-day exploitation probability)+1

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.17%

ahead of 6% of scored CVEs · Oct 30, 2026

Affects

Linux

CVSS base

—

Score not published yet.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	≥ e21a9ea81426a85fdb0cdcfcc99d5d9c16b402ab and < d3c2d2692bdf4af94bb27bc7a3aa0a348a567606≥ cc73b2043d106b467accd38e9b1fc09e0607c056 and < f38c57a28ebbd057471573e39555d5aa11ab03cf≥ d5d8b8662e6e5a565b47a0388640e88402f23274 and < e3ee38c1bc0b11a8d3e63dce7050759b61864286≥ 6.18.53 and < 6.18.56≥ 7.2.7 and < 7.2.10	Vulnerable	CVE Program (cve.org) e CISA ADP

EPSS over time FIRST

Oct 24, 2026 → Oct 30, 2026 · 7 reading(s) · max 0.21%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Not enough vector or weakness data: use the affected application’s logs as a starting point.

application logs

Timeline

What happened to this CVE, newest first.

2026
Record published
Oct 23, 2026
Affected products added · linux/linux
Oct 23, 2026 · CVE Program (cve.org) e CISA ADP
Source status changed · → Received
Oct 23, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 23, 2026 · Alertas do Telegram
CVE published
Oct 23, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

1× References added · Oct 23, 2026 – Oct 23, 2026
1× Official description updated · Oct 23, 2026 – Oct 23, 2026

References

3 on the record

git.kernel.org/stable/c/f38c57a28ebbd057471573e39555d5aa11ab03cf
NIST National Vulnerability Database
git.kernel.org/stable/c/e3ee38c1bc0b11a8d3e63dce7050759b61864286
NIST National Vulnerability Database
git.kernel.org/stable/c/d3c2d2692bdf4af94bb27bc7a3aa0a348a567606
NIST National Vulnerability Database

Elsewhere on this site

Linux
every CVE for this vendor

Related CVEs (same products)

Unknown CVE-2026-99216 Drivers: hv: Don't reset VMBus connection state on error/exit paths 2d
Unknown CVE-2026-99215 power: supply: core: prevent unregistering a power supply while a callback runs 2d
Unknown CVE-2026-99207 scsi: target: Disable interrupts while holding delayed_cmd_lock 2d
Unknown CVE-2026-99208 drm/xe/oa: Zero OA buffer at allocation 2d
Unknown CVE-2026-99209 drm/xe: skip eviction of a BO with no resource 2d
Unknown CVE-2026-99210 accel/rocket: clear rdev on device init failure 2d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CVSS score published by NVD, the CNA, CISA or GitHub so far.
No fixed version, patch or mitigation documented.
No CISA SSVC assessment.
No CWE classification.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-98939 is "x86/mm: Drop unnecessary PMD page copy when freeing", rated Unknown. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. EPSS 0.17% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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