CVE-2026-98718KVM: SEV: Do cache maintenance on the source VM *before* clearing SEV state

Official description

In the Linux kernel, the following vulnerability has been resolved: KVM: SEV: Do cache maintenance on the source VM *before* clearing SEV state Explicitly flush caches after intra-host migration before clearing "SEV active" on the source VM, as doing cache maintenance afterwards creates a tiny window where memory reclaim could return memory to the host without performing a cache flush, e.g. as pointed out by Sashiko: CPU1 in sev_migrate_from(): src->active = false; CPU2 running concurrent unmap: Since active is false, the automatic cache flush in sev_guest_memory_reclaimed is skipped. The host frees and reallocates the page. CPU1 in sev_migrate_from(): sev_writeback_caches(src_kvm); Executes a hardware cache flush (wbnoinvd), which writes the guest's old dirty ciphertext over the new page owner's data.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/8b7d4f68fef96cebe0b6dbb6e5607772337f7369
• https://git.kernel.org/stable/c/de83ff6a4d8f3618473bedb3c4400020c22e8a8a
• https://git.kernel.org/stable/c/973ea70393e885e540f714904e51bc6cac80e3d7