The workaround for the Meltdown vulnerability (XSA-254) failed to deal
with an error code path connecting the INT 80 handling with general
exception handling. This results in an unconditional write attempt of
the value zero to an address near 2^64, in cases where a PV guest has no
handler installed for INT 80 on one of its vCPU-s.
A malicious or buggy guest may cause a hypervisor crash, resulting in
a Denial of Service (DoS) affecting the entire host.
All Xen versions which the XSA-254 fixes were applied to are vulnerable.
Only x86 systems are vulnerable. ARM systems are not vulnerable.
Only x86 PV guests can exploit the vulnerability. x86 PVH and HVM
guests cannot exploit the vulnerability.
Running only PVH or HVM guests avoids the vulnerability.
Name: the Xen project
Upstream: Andrew Cooper (Citrix)
Created xen tracking bugs for this issue:
Affects: fedora-all [bug 1571878]