From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757260Ab3HMLpY (ORCPT ); Tue, 13 Aug 2013 07:45:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34811 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756899Ab3HMLpW (ORCPT ); Tue, 13 Aug 2013 07:45:22 -0400 Date: Tue, 13 Aug 2013 07:45:03 -0400 From: Dave Jones To: Ingo Molnar Cc: Steven Rostedt , Linus Torvalds , LKML , Frederic Weisbecker , Masami Hiramatsu , Oleg Nesterov , Andrew Morton , Greg Kroah-Hartman Subject: Re: [GIT PULL] tracing: final fixes for events and some Message-ID: <20130813114503.GA31585@redhat.com> Mail-Followup-To: Dave Jones , Ingo Molnar , Steven Rostedt , Linus Torvalds , LKML , Frederic Weisbecker , Masami Hiramatsu , Oleg Nesterov , Andrew Morton , Greg Kroah-Hartman References: <1375712355.22073.45.camel@gandalf.local.home> <20130805143257.GA32639@gmail.com> <1375714329.22073.63.camel@gandalf.local.home> <20130812181325.GA19405@gmail.com> <20130813023922.GA1042@redhat.com> <20130812231443.52563398@gandalf.local.home> <20130813110618.GA3300@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130813110618.GA3300@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 13, 2013 at 01:06:18PM +0200, Ingo Molnar wrote: > > * Steven Rostedt wrote: > > > On Mon, 12 Aug 2013 22:39:22 -0400 > > Dave Jones wrote: > > > > > > > I'm not sure why I got cc'd on this, but for my part, the perf/tracing > > > related bugs I've found recently may have been there for ages, but > > > they were triggerable as non-root users. > > > > Which bug was able to trigger with non-root? The hash one that you > > reported? That is something with the function tracer. Are you able to > > enable function tracing as non-root? > > > > Or is it because you gave more permissions for non-root to use extra > > perf commands. Because no one but root should be able to enable function > > tracing, as that can add a large overhead to the system. > > Hm, also, tracepoints should in general only be accessible to root - all > sorts of random privileged info leaks through tracepoints, a thorough > review and sanitizing is needed to expose that to users. (and that does > not consider the complication caused by exposing timing info.) With the benefit of sleep, I might take that back, though I'm working from memory of a bug that I've not seen in over a month. I may have been chasing a user-triggerable bug, and used tracing (as root) to diagnose and then walked into one of these. But the recent fix where you had a test-case that did module unloads didn't really seem to fit the profile of what I was seeing. It's feasible that my fuzzer can trigger module _loads_, but I don't think there's any way we can trigger an rmmod. Dave