CVE-2026-64285

In the Linux kernel, the following vulnerability has been resolved:

KVM: SEV: Pin source page for write when adding CPUID data for SNP guest

When populating a guest_memfd instance with the initial CPUID data for an

SNP guest, acquire a writable pin on the source page as KVM will write back

the "correct" CPUID information if the userspace provided data is rejected

by trusted firmware. Because KVM writes to the source page using a kernel

mapping, pinning for read could result in KVM clobbering read-only memory.

Note, well-behaved VMMs are unlikely to be affected, as CPUID information

is almost always dynamically generated by userspace, i.e. it's unlikely for

the CPUID information to be backed by a read-only mapping.

[sean: rewrite shortlog and changelog, tag for stable@]