Em Tue, Aug 02, 2016 at 11:52:43AM +0200, Peter Zijlstra escreveu: > On Wed, Jul 27, 2016 at 07:45:46AM -0700, Jeff Vander Stoep wrote: > > When kernel.perf_event_paranoid is set to 3 (or greater), disallow > > all access to performance events by users without CAP_SYS_ADMIN. > > This new level of restriction is intended to reduce the attack > > surface of the kernel. Perf is a valuable tool for developers but > > is generally unnecessary and unused on production systems. Perf may > > open up an attack vector to vulnerable device-specific drivers as > > recently demonstrated in CVE-2016-0805, CVE-2016-0819, > > CVE-2016-0843, CVE-2016-3768, and CVE-2016-3843. > We have bugs we fix them, we don't kill complete infrastructure because > of them. > > This new level of > > restriction allows for a safe default to be set on production systems > > while leaving a simple means for developers to grant access [1]. > So the problem I have with this is that it will completely inhibit > development of things like JITs that self-profile to re-compile > frequently used code. Or reimplement strace with sys_perf_event_open(), speeding it up greatly by not using ptrace (see 'perf trace', one such attempt), combining it with sys_bpf(), which can run unpriviledged as well, provides lots of possibilities for efficient tooling that would be greatly stiffled by such big hammer restrictions :-( > I would much rather have an LSM hook where the security stuff can do > more fine grained control of things. Allowing some apps perf usage while > denying others. - Arnaldo -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
