The snd_ctl_elem_add function in sound/core/control.c in the ALSA control implementation in the Linux kernel before 3.15.2 does not properly maintain the user_ctl_count value, which allows local users to cause a denial of service (integer overflow and limit bypass) by leveraging /dev/snd/controlCX access for a large number of SNDRV_CTL_IOCTL_ELEM_REPLACE ioctl calls.
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.