Re: [RFC][PATCH 3/4] tracing/kprobes: Fail to unregister if probeevent files are open
From: Steven Rostedt
Date: Wed Jul 31 2013 - 18:42:36 EST
On Wed, 2013-07-31 at 22:40 +0200, Oleg Nesterov wrote:
> On 07/31, Steven Rostedt wrote:
> > On Wed, 2013-07-03 at 23:33 -0400, Steven Rostedt wrote:
> > > The above will corrupt the kprobe system, as the write to the enable
> > > file will happen after the kprobe was deleted.
> > Oleg,
> > The above no longer triggers the bug due to your changes. The race is
> > much tighter now
> Yes, the changelog should be updated...
> > and requires a process with the enable file opened and
> > races with a write to enable it where the removal of the trace file
> > checks the trace disabled, sees that it is, continues, but then the
> > write enables it just as it gets deleted.
> This should be fine. Either event_remove() path takes event_mutex
> first and then ->write() fails, or ftrace_event_enable_disable()
> actually disables this even successfully.
Actually I meant while in unregister_trace_probe(), it gets by the
trace_probe_is_enabled() part first, then the write succeeds (as the
event_mutex isn't taken till unregister_probe_event()). The the
unregister_probe_event fails, but the tp was freed. The event files
still reference the tp and this is where a crash can happen without this
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/