Race condition in the ion_ioctl function in drivers/staging/android/ion/ion.c in the Linux kernel before 4.6 allows local users to gain privileges or cause a denial of service (use-after-free) by calling ION_IOC_FREE on two CPUs at the same time.
https://github.com/torvalds/linux/commit/9590232bb4f4cc824f3425a6e1349afbe6d6d2b7
http://www.securityfocus.com/bid/94669