Xen Security Advisory XSA-116
xen crash due to use after free on hvm guest teardown
Certain data accessible (via hypercalls) by the domain controlling the
execution of a HVM domain is being freed prematurely, leading to the
respective memory regions to possibly be read from and written to in
ways unexpected by their new owner(s).
Malicious or buggy stub domain kernels or tool stacks otherwise living
outside of Domain0 can mount a denial of service attack which, if
successful, can affect the whole system.
Only domains controlling HVM guests can exploit this vulnerability.
(This includes domains providing hardware emulation services to HVM
Xen versions from 4.2 onwards are vulnerable on x86 systems.
ARM systems are not vulnerable.
This vulnerability is only applicable to Xen systems using stub domains
or other forms of disaggregation of control domains for HVM guests.
Running only PV guests will avoid this issue.
(The security of a Xen system using stub domains is still better than
with a qemu-dm running as an unrestricted dom0 process. Therefore
users with these configurations should not switch to an unrestricted
The issue was discovered by Mihai Donțu from Bitdefender who also
supplied the fix.
Applying the appropriate attached patch resolves this issue.
xsa116.patch xen-unstable, Xen 4.4.x
xsa116-4.3-4.2.patch Xen 4.3.x, Xen 4.2.x
$ sha256sum xsa116*.patch
Created attachment 971110 [details]
Created attachment 971111 [details]
Red Hat would like to thank the Xen project for reporting this issue.
Created xen tracking bugs for this issue:
Affects: fedora-all [bug 1179221]
xen-4.4.1-12.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.
xen-4.3.3-9.fc20 has been pushed to the Fedora 20 stable repository. If problems still persist, please make note of it in this bug report.
This issue does not affect the kernel-xen packages as shipped with Red Hat Enterprise Linux 5.