The mp_get_count function in drivers/staging/sb105x/sb_pci_mp.c in the Linux kernel before 3.12 does not initialize a certain data structure, which allows local users to obtain sensitive information from kernel stack memory via a TIOCGICOUNT ioctl call.
https://www.kernel.org/pub/linux/kernel/v3.x/patch-3.12.bz2
http://www.ubuntu.com/usn/USN-2075-1
http://www.ubuntu.com/usn/USN-2073-1
http://www.ubuntu.com/usn/USN-2070-1
http://www.ubuntu.com/usn/USN-2069-1