The perf_callchain_user_64 function in arch/powerpc/perf/callchain.c in the Linux kernel before 4.0.2 on ppc64 platforms allows local users to cause a denial of service (infinite loop) via a deep 64-bit userspace backtrace.
https://github.com/torvalds/linux/commit/9a5cbce421a283e6aea3c4007f141735bf9da8c3
https://bugzilla.redhat.com/show_bug.cgi?id=1218454
http://www.ubuntu.com/usn/USN-2760-1
http://www.ubuntu.com/usn/USN-2759-1
http://www.securitytracker.com/id/1033728
http://www.securityfocus.com/bid/76401
http://www.oracle.com/technetwork/topics/security/linuxbulletinoct2015-2719645.html
http://www.openwall.com/lists/oss-security/2015/08/18/4