Bug 2281956 (CVE-2023-46842, XSA-454)

Summary: CVE-2023-46842 xen: x86 HVM hypercalls may trigger Xen bug check
Product: [Other] Security Response Reporter: Pedro Sampaio <psampaio>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Description Pedro Sampaio 2024-05-20 17:35:15 UTC 
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.

https://xenbits.xenproject.org/xsa/advisory-454.html
Comment 1 Pedro Sampaio 2024-05-20 17:35:32 UTC 
Created xen tracking bugs for this issue:

Affects: fedora-all [bug 2281957]