CVE-2015-8339: Error handling in the operation may involve handing back pages to the domain. This operation may fail when in parallel the domain gets torn down. So far this failure unconditionally resulted in the host being brought down due to an internal error being assumed. CVE-2015-8340: Furthermore error handling so far wrongly included the release of a lock. That lock, however, was either not acquired or already released on all paths leading to the error handling sequence. A malicious guest administrator may be able to deny service by crashing the host or causing a deadlock. All Xen versions from at least 3.2 onwards are vulnerable. Older versions have not been inspected. The vulnerability can be avoided if the guest kernel is controlled by the host rather than guest administrator, provided that further steps are taken to prevent the guest administrator from loading code into the kernel (e.g. by disabling loadable modules etc) or from using other mechanisms which allow them to run code at kernel privilege. In Xen HVM, controlling the guest's kernel would involve locking down the bootloader.
Created attachment 1098198 [details] xen-unstable, Xen 4.6.x, Xen 4.5.x, Xen 4.4.x, Xen 4.3.x
External References: http://xenbits.xen.org/xsa/advisory-159.html
Created xen tracking bugs for this issue: Affects: fedora-all [bug 1289568]
xen-4.5.2-5.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.
xen-4.5.2-5.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.
Statement:
Statement: This issue does not affect the Linux kernel packages as shipped with Red Hat Enterprise Linux 6, 7, MRG-2 and realtime kernels. At this time, there is no plans to fix this issue, if you feel that this issue is affecting your deployment and have an EUS subscription, please contact support to have this issue correctly prioritized
Mitigation: The vulnerability can be avoided if the guest kernel is controlled by the host rather than guest administrator, provided that further steps are taken to prevent the guest administrator from loading code into the kernel (e.g. by disabling loadable modules etc) or from using other mechanisms which allow them to run code at kernel privilege. In Xen HVM, controlling the guest's kernel would involve locking down the bootloader.