lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Wed, 29 Mar 2017 11:42:27 +0900 From: Namhyung Kim <namhyung@...nel.org> To: Steven Rostedt <rostedt@...dmis.org> Cc: Ingo Molnar <mingo@...nel.org>, Masami Hiramatsu <mhiramat@...nel.org>, LKML <linux-kernel@...r.kernel.org>, kernel-team@....com Subject: Re: [PATCH 1/4] ftrace: Fix function pid filter on instances On Tue, Mar 28, 2017 at 10:28:55PM -0400, Steven Rostedt wrote: > On Wed, 29 Mar 2017 11:20:37 +0900 > Namhyung Kim <namhyung@...nel.org> wrote: > > > > > Actually, if this is called after event_trace_del_tracer(), the tr is > > > already invisible and nothing new should change. > > > > I don't follow. After event_trace_del_tracer(), the tr is invisible > > from the probe of event tracing but still is visible from the probe of > > function tracing, right? > > Well, nothing should be able to get to the set_ftrace_filter file when > there. Because of the tr->ref count. But keeping the lock is safer > regardless, and it's not a fast path, so the extra overhead if the lock > isn't needed is no big deal. Oh, I meant if a pid filter was already set when removing the instance. Function filters should be inactive since function tracer was finished (via tracing_set_nop), but the probe on sched_switch event (for pid filter) is still active and references the tr. Thanks, Namhyung > > > > > > > > > Make a wrapper around clear_ftrace_pids() and call that instead. We > > > don't even need to take a lock, but as I see there's a lockdep test for > > > ftrace_lock, we should still do so just to be safe. > > > > Right, that's why I call ftrace_pid_reset() instead of > > clear_ftrace_pids(). So do you prefer adding a new wrapper like below > > rather than reusing ftrace_pid_reset() with a new argument? > > Yes, because the bool passed in is confusing. A separate function like > below is more descriptive. > > -- Steve > > > > > Thanks, > > Namhyung > > > > > > > > > > void ftrace_clear_pids(struct trace_array *tr) > > > { > > > mutex_lock(&ftrace_lock); > > > > > > clear_ftrace_pids(tr); > > > > > > mutex_unlock(&ftrace_lock); > > > }
Powered by blists - more mailing lists