CVE-2021-28709

issues with partially successful P2M updates on x86 T[his CNA information
record relates to multiple CVEs; the text explains which
aspects/vulnerabilities correspond to which CVE.] x86 HVM and PVH guests
may be started in populate-on-demand (PoD) mode, to provide a way for them
to later easily have more memory assigned. Guests are permitted to control
certain P2M aspects of individual pages via hypercalls. These hypercalls
may act on ranges of pages specified via page orders (resulting in a
power-of-2 number of pages). In some cases the hypervisor carries out the
requests by splitting them into smaller chunks. Error handling in certain
PoD cases has been insufficient in that in particular partial success of
some operations was not properly accounted for. There are two code paths
affected - page removal (CVE-2021-28705) and insertion of new pages
(CVE-2021-28709). (We provide one patch which combines the fix to both
issues.)

Notes