On Mon, Oct 17, 2016 at 6:44 AM, Mark Rutland <mark.rutland@xxxxxxx> wrote: > Hi, > > Attempt to revive discussions below... > > 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. 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]. >> >> This feature is derived from CONFIG_GRKERNSEC_PERF_HARDEN by Brad >> Spengler. It is based on a patch by Ben Hutchings [2]. Ben's patches >> have been modified and split up to address on-list feedback. >> >> kernel.perf_event_paranoid=3 is the default on both Debian [2] and >> Android [3]. > > While people weren't particularly happy with this global toggle > approach, my understanding from face-to-face discussions at LSS2016 was > that people were happy with a more scoped restriction (e.g. using > capabilities or some other access control mechanism), but no-one had the > time to work on that. > > Does that match everyone's understanding, or am I mistaken? That's correct: some kind of finer-grain control would be preferred to the maintainer, but no one has had time to work on it. (The =3 sysctl setting present in Android, Debian, and Ubuntu satisfies most people.) -Kees -- Kees Cook Nexus Security -- 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
