CVE-2022-49562: KVM: x86: Use __try_cmpxchg_user() to update guest PTE A/D bits

Severity: medium (CVSS 5.5 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: 2025-02-26 · updated 2026-08-04

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Use __try_cmpxchg_user() to update guest PTE A/D bits Use the recently introduced __try_cmpxchg_user() to update guest PTE A/D bits instead of mapping the PTE into kernel address space. The VM_PFNMAP path is broken as it assumes that vm_pgoff is the base pfn of the mapped VMA range, which is conceptually wrong as vm_pgoff is the offset relative to the file and has nothing to do with the pfn. The horrific hack worked for the original use case (backing guest memory with /dev/mem), but leads to accessing "random" pfns for pretty much any other VM_PFNMAP case.

Affected products

Linux kernel: from 5.2 before 5.17.13; from 5.18 before 5.18.2 — fixed in 5.17.13, 5.18.2

How to fix

Upgrade to a fixed version: Linux kernel 5.17.13, 5.18.2. Check the vendor advisory for mitigations.

References

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