Upstream commit dab5855 ("perf_counter: Add mmap event hooks to 
mprotect()") is fundamentally wrong as mprotect_fixup() can free 'vma' 
due to merging. Fix the problem by moving perf_event_mmap() hook to 
mprotect_fixup(). In certain scenario, a local, unprivileged user could 
use this flaw to trigger a denial of service.

Upstream commit:
http://git.kernel.org/linus/63bfd7384b119409685a17d5c58f0b56e5dc03da

https://bugzilla.redhat.com/show_bug.cgi?id=651671