kvm: multiple vulnerabilities

The x86 emulator implementation was missing a check for the Current Privilege Level (CPL) and I/O Privilege Level (IOPL). A user in a guest could leverage these flaws to cause a denial of service (guest crash) or possibly escalate their privileges within that guest. (CVE-2010-0298, CVE-2010-0306)

A flaw was found in the Programmable Interval Timer (PIT) emulation. Access to the internal data structure pit_state, which represents the data state of the emulated PIT, was not properly validated in the pit_ioport_read() function. A privileged guest user could use this flaw to crash the host. (CVE-2010-0309)

A flaw was found in the USB passthrough handling code. A specially-crafted USB packet sent from inside a guest could be used to trigger a buffer overflow in the usb_host_handle_control() function, which runs under the QEMU-KVM context on the host. A user in a guest could leverage this flaw to cause a denial of service (guest hang or crash) or possibly escalate their privileges within the host. (CVE-2010-0297)