kernel/events/core.c in the performance subsystem in the Linux kernel before 4.0 mismanages locks during certain migrations, which allows local users to gain privileges via a crafted application, aka Android internal bug 30955111.
https://github.com/torvalds/linux/commit/f63a8daa5812afef4f06c962351687e1ff9ccb2b
https://bugzilla.redhat.com/show_bug.cgi?id=1403842
http://www.securityfocus.com/bid/94679
http://www.debian.org/security/2017/dsa-3791