The pciej_write function in hw/acpi_piix4.c in the PIIX4 Power Management emulation in qemu-kvm does not check if a device is hotpluggable before unplugging the PCI-ISA bridge, which allows privileged guest users to cause a denial of service (guest crash) and possibly execute arbitrary code by sending a crafted value to the 0xae08 (PCI_EJ_BASE) I/O port, which leads to a use-after-free related to "active qemu timers."
https://www.ubuntu.com/usn/USN-1145-1/
https://hermes.opensuse.org/messages/8572547
https://github.com/nelhage/virtunoid
https://bugzilla.redhat.com/show_bug.cgi?id=699773
http://www.securityfocus.com/bid/47927
http://www.openwall.com/lists/oss-security/2011/05/19/2
http://secunia.com/advisories/44900
http://secunia.com/advisories/44660
http://secunia.com/advisories/44658
http://secunia.com/advisories/44648
http://secunia.com/advisories/44458
http://secunia.com/advisories/44393
http://rhn.redhat.com/errata/RHSA-2011-0534.html
http://lists.opensuse.org/opensuse-updates/2011-05/msg00043.html
http://lists.nongnu.org/archive/html/qemu-devel/2011-05/msg01810.html