kernel/trace/trace_syscalls.c in the Linux kernel through 3.17.2 does not properly handle private syscall numbers during use of the perf subsystem, which allows local users to cause a denial of service (out-of-bounds read and OOPS) or bypass the ASLR protection mechanism via a crafted application.
http://rhn.redhat.com/errata/RHSA-2014-1943.html
http://rhn.redhat.com/errata/RHSA-2015-0290.html
http://rhn.redhat.com/errata/RHSA-2015-0864.html
https://bugzilla.redhat.com/show_bug.cgi?id=1161565
https://exchange.xforce.ibmcloud.com/vulnerabilities/98557
https://github.com/torvalds/linux/commit/086ba77a6db00ed858ff07451bedee197df868c9