The qdisk PV disk backend in the qemu-xen flavour of qemu ("upstream qemu") can be influenced by a malicious frontend to leak mapped grant references. A malicious HVM guest can cause the backend domain to run out of grant references, leading to a DoS for any other domain which shares that driver domain. Acknowledgements: Red Hat would like to thank the Xen project for reporting this issue.
Statement: Not vulnerable. This issue does not affect the versions of the xen package as shipped with Red Hat Enterprise Linux 5 as it does not provide support for the qdisk PV backend. This issue does not affect the versions of qemu-kvm as shipped with Red Hat Enterprise Linux 6 as they did not include the upstream commit that introduced this flaw. This issue does not affect Red Hat Enterprise MRG 2.
External Reference: http://xenbits.xen.org/xsa/advisory-71.html
Created xen tracking bugs for this issue: Affects: fedora-all [bug 1017843]
Created qemu tracking bugs for this issue: Affects: fedora-all [bug 1017844]
xen-4.2.3-4.fc18 has been pushed to the Fedora 18 stable repository. If problems still persist, please make note of it in this bug report.
xen-4.2.3-4.fc19 has been pushed to the Fedora 19 stable repository. If problems still persist, please make note of it in this bug report.