CVE-2024-35804: In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Mark target gfn of emulated atomic instruction as dirty When emulating...

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Mark target gfn of emulated atomic instruction as dirty When emulating an atomic access on behalf of the guest, mark the target gfn dirty if the CMPXCHG by KVM is attempted and doesn't fault. This fixes a bug where KVM effectively corrupts guest memory during live migration by writing to guest memory without informing userspace that the page is dirty. Marking the page dirty got unintentionally dropped when KVM's emulated CMPXCHG was converted to do a user access. Before that, KVM explicitly mapped the guest page into kernel memory, and marked the page dirty during the unmap phase. Mark the page dirty even if the CMPXCHG fails, as the old data is written back on failure, i.e. the page is still written. The value written is guaranteed to be the same because the operation is atomic, but KVM's ABI is that all writes are dirty logged regardless of the value written. And more importantly, that's what KVM did before the buggy commit. Huge kudos to the folks on the Cc list (and many others), who did all the actual work of triaging and debugging. base-commit: 6769ea8da8a93ed4630f1ce64df6aafcaabfce64

Metrics

CVSS 3.1

5.5/10

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.22%

13.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-401

Affected Software

Vendor	Product	Versions	Update
Linux	Linux Kernel	>= 5.15.58, < 5.15.154	—
Linux	Linux Kernel	>= 5.17.13, < 5.18	—
Linux	Linux Kernel	>= 5.18.2, < 6.1.84	—
Linux	Linux Kernel	>= 6.2, < 6.6.24	—
Linux	Linux Kernel	>= 6.7, < 6.7.12	—
Linux	Linux Kernel	6.8	Rc1

References

Timeline

Published: May 17, 2024
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2024-35804?

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: Mark target gfn of emulated atomic instruction as dirty When emulating an atomic access on behalf of the guest, mark the target gfn dirty if the CMPXCHG by KVM is attempted and doesn't fault. This fixes a bug where KVM effectively corrupts guest memory during live migration by writing to guest memory without informing userspace that the page is dirty. Marking the page dirty got unintentionally dropped when KVM's emulated CMPXCHG was converted to do a user access. Before that, KVM explicitly mapped the guest page into kernel memory, and marked the page dirty during the unmap phase. Mark the page dirty even if the CMPXCHG fails, as the old data is written back on failure, i.e. the page is still written. The value written is guaranteed to be the same because the operation is atomic, but KVM's ABI is that all writes are dirty logged regardless of the value written. And more importantly, that's what KVM did before the buggy commit. Huge kudos to the folks on the Cc list (and many others), who did all the actual work of triaging and debugging. base-commit: 6769ea8da8a93ed4630f1ce64df6aafcaabfce64

How severe is CVE-2024-35804?

CVE-2024-35804 has a CVSS score of 5.5/10 (MEDIUM severity). The EPSS model estimates a 0.22% probability of exploitation in the next 30 days.

How do I fix CVE-2024-35804?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.