CVE-2024-35791: KVM: SVM: Flush pages under kvm->lock to fix UAF in svm_register_enc_region()

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2024-05-17 · updated 2026-08-04
Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Flush pages under kvm->lock to fix UAF in svm_register_enc_region() Do the cache flush of converted pages in svm_register_enc_region() before dropping kvm->lock to fix use-after-free issues where region and/or its array of pages could be freed by a different task, e.g. if userspace has __unregister_enc_region_locked() already queued up for the region. Note, the "obvious" alternative of using local variables doesn't fully resolve the bug, as region->pages is also dynamically allocated. I.e. the region structure itself would be fine, but region->pages could be freed. Flushing multiple pages under kvm->lock is unfortunate, but the entire flow is a rare slow path, and the manual flush is only needed on CPUs that lack coherency for encrypted memory.

Affected products

Debian Linux: 10.0
Linux kernel: from 4.19.176 before 4.20; from 5.4.98 before 5.5; from 5.10.15 before 5.10.215; from 5.11.1 before 5.15.154; from 5.16 before 6.1.84; from 6.2 before 6.6.24 — fixed in 4.20, 5.10.215, 5.15.154, 5.5, 6.1.84, 6.6.24

How to fix

Upgrade to a fixed version: Linux kernel 4.20, 5.10.215, 5.15.154, 5.5. Check the vendor advisory for mitigations.

References

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