When kernel.perf_event_open is set to 3 (or greater), disallow all
access to performance events by users without CAP_SYS_ADMIN.
Add a Kconfig symbol CONFIG_SECURITY_PERF_EVENTS_RESTRICT that
makes this value the default.
This is based on a similar feature in grsecurity
(CONFIG_GRKERNSEC_PERF_HARDEN). This version doesn't include making
the variable read-only. It also allows enabling further restriction
at run-time regardless of whether the default is changed.
https://lkml.org/lkml/2016/1/11/587
Bug: 29054680
Bug: 120445712
Change-Id: Iff5bff4fc1042e85866df9faa01bce8d04335ab8
[jeffv: Upstream doesn't want it https://lkml.org/lkml/2016/6/17/101]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
8e5e42d5ae