From secunia advisory at $URL: Description A vulnerability has been reported in KVM, which can be exploited by malicious, local users in a guest virtual machine to cause a DoS (Denial of Service). The vulnerability is caused due a memory leak error when unpinning device mappings from the IOMMU. This can be exploited to exhaust memory and render the system unusable by unplugging and plugging certain devices. Solution Fixed in the GIT repository. Original Advisory https://lkml.org/lkml/2012/4/11/248
This bug is not in the user space component. This is a bug in the kernel. Please change it to the kernel and ask the gentoo-sources guys to fix it.
There are no longer any 2.x or <3.3.x kernels available in the repository with the exception of sys-kernel/xbox-sources which is unsupported by security.