CVE-2024-35791

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.