CVE-2023-46842

Unlike 32-bit PV guests, HVM guests may switch freely between 64-bit and<br /> other modes. This in particular means that they may set registers used<br /> to pass 32-bit-mode hypercall arguments to values outside of the range<br /> 32-bit code would be able to set them to.<br /> <br /> When processing of hypercalls takes a considerable amount of time,<br /> the hypervisor may choose to invoke a hypercall continuation. Doing so<br /> involves putting (perhaps updated) hypercall arguments in respective<br /> registers. For guests not running in 64-bit mode this further involves<br /> a certain amount of translation of the values.<br /> <br /> Unfortunately internal sanity checking of these translated values<br /> assumes high halves of registers to always be clear when invoking a<br /> hypercall. When this is found not to be the case, it triggers a<br /> consistency check in the hypervisor and causes a crash.<br />