| Assigner | XEN |
| Reserved | 2023-10-27 |
| Published | 2024-05-16 |
| Updated | 2024-06-04 |
Description
Unlike 32-bit PV guests, HVM guests may switch freely between 64-bit and other modes. This in particular means that they may set registers used to pass 32-bit-mode hypercall arguments to values outside of the range 32-bit code would be able to set them to. When processing of hypercalls takes a considerable amount of time, the hypervisor may choose to invoke a hypercall continuation. Doing so involves putting (perhaps updated) hypercall arguments in respective registers. For guests not running in 64-bit mode this further involves a certain amount of translation of the values. Unfortunately internal sanity checking of these translated values assumes high halves of registers to always be clear when invoking a hypercall. When this is found not to be the case, it triggers a consistency check in the hypervisor and causes a crash.
Product status
consult Xen advisory XSA-454
Credits
This issue was discovered by Manuel Andreas of Technical University of
Munich.
References
https://xenbits.xenproject.org/xsa/advisory-454.html
