qemu: multiple issues

• CVE-2015-3214 (information disclosure, arbitrary code execution)

An out-of-bounds memory access flaw, leading to memory corruption or
possibly an information leak, was found in QEMU’s pit_ioport_read()
function. A privileged guest user in a QEMU guest, which had QEMU PIT
emulation enabled, could potentially, in rare cases, use this flaw to
execute arbitrary code on the host with the privileges of the hosting
QEMU process.

• CVE-2015-5154 (arbitrary code execution)

A heap overflow flaw was found in the way QEMU’s IDE subsystem handled
I/O buffer access while processing certain ATAPI commands. A privileged
guest user in a guest with CDROM drive enabled could potentially use
this flaw to execute arbitrary code on the host with the privileges of
the host’s QEMU process corresponding to the guest.

• CVE-2015-5158 (denial of service)

This is a guest-triggerable buffer overflow. The scsi_cdb_length returns
-1 as an error value, but the caller does not check it. Luckily, the
massive overflow means that QEMU will just SIGSEGV, leading to denial of
service of the guest system.