Description: tracing: Check for no filter when processing event filters
References:
 https://bugzilla.kernel.org/show_bug.cgi?id=200019
 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-12714
Notes:
 bwh> Almost certainly introduced by commit 80765597bc58
 bwh> "tracing: Rewrite filter logic to be simpler and faster",
 bwh> although the old code may well have had other vulnerabilities.
Bugs:
upstream: released (4.18-rc2) [70303420b5721c38998cf987e6b7d30cc62d4ff1]
4.9-upstream-stable: N/A "Vulnerability introduced later"
3.16-upstream-stable: N/A "Vulnerability introduced later"
sid: N/A "Vulnerability introduced later"
4.9-stretch-security: N/A "Vulnerability introduced later"
3.16-jessie-security: N/A "Vulnerability introduced later"