CVE-2022-48991: mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-10-21 · updated 2026-08-04
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: mm/khugepaged: invoke MMU notifiers in shmem/file collapse paths Any codepath that zaps page table entries must invoke MMU notifiers to ensure that secondary MMUs (like KVM) don't keep accessing pages which aren't mapped anymore. Secondary MMUs don't hold their own references to pages that are mirrored over, so failing to notify them can lead to page use-after-free. I'm marking this as addressing an issue introduced in commit f3f0e1d2150b ("khugepaged: add support of collapse for tmpfs/shmem pages"), but most of the security impact of this only came in commit 27e1f8273113 ("khugepaged: enable collapse pmd for pte-mapped THP"), which actually omitted flushes for the removal of present PTEs, not just for the removal of empty page tables.

Affected products

Linux kernel: from 4.8 before 4.9.337; from 4.10 before 4.14.303; from 4.15 before 4.19.270; from 4.20 before 5.4.227; from 5.5 before 5.10.159; from 5.11 before 5.15.83 — fixed in 4.14.303, 4.19.270, 4.9.337, 5.10.159, 5.15.83, 5.4.227

How to fix

Upgrade to a fixed version: Linux kernel 4.14.303, 4.19.270, 4.9.337, 5.10.159. Check the vendor advisory for mitigations.

References

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