From: Oleg Nesterov <oleg@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
"zhangwei(Jovi)" <jovi.zhangwei@huawei.com>,
Jiri Olsa <jolsa@redhat.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC][PATCH 3/4] tracing/kprobes: Fail to unregister if probe event files are open
Date: Wed, 31 Jul 2013 22:40:03 +0200 [thread overview]
Message-ID: <20130731204003.GA30188@redhat.com> (raw)
In-Reply-To: <1375300192.5418.17.camel@gandalf.local.home>
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.
> Do you know of a way to trigger this bug?
I'll try to think more tomorrow, but most probably no. The race is
unlikely.
We need perf_trace_event_init() or ":enable_event:this-event" right
before trace_remove_event_call() takes the mutex.
And right after the caller (kprobes) checks "disabled".
> Hmm, what happens without this patch now? If it is active, and we delete
> it? It will call back into the kprobes and access a tracepoint that does
> not exist? Would this cause a crash?
I think yes, the crash is possible.
perf or FL_SOFT_MODE, this call/file has the external references, and
we are going to free it.
Oleg.
next prev parent reply other threads:[~2013-07-31 20:45 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-04 3:33 [RFC][PATCH 0/4] tracing/kprobes/uprobes: Fix race between opening probe event files and deleting probe Steven Rostedt
2013-07-04 3:33 ` [RFC][PATCH 1/4] tracing: Add ref count to ftrace_event_call Steven Rostedt
2013-07-04 4:22 ` Masami Hiramatsu
2013-07-04 11:55 ` [RFC PATCH] tracing: Atomically get refcounts of event_call and trace_array Masami Hiramatsu
2013-07-04 12:12 ` Masami Hiramatsu
2013-07-04 12:23 ` Steven Rostedt
2013-07-05 0:32 ` Oleg Nesterov
2013-07-05 2:32 ` Masami Hiramatsu
2013-07-09 7:55 ` [RFC PATCH V2] tracing: Check f_dentry before accessing event_file/call in inode->i_private Masami Hiramatsu
2013-07-15 18:16 ` Oleg Nesterov
2013-07-17 2:10 ` Masami Hiramatsu
2013-07-17 14:51 ` Oleg Nesterov
2013-07-18 2:20 ` Masami Hiramatsu
2013-07-18 14:51 ` Oleg Nesterov
2013-07-19 5:21 ` Masami Hiramatsu
2013-07-19 13:33 ` Oleg Nesterov
2013-07-22 9:57 ` Masami Hiramatsu
2013-07-22 17:04 ` Oleg Nesterov
2013-07-23 21:04 ` Oleg Nesterov
2013-07-04 3:33 ` [RFC][PATCH 2/4] tracing: trace_remove_event_call() should fail if call/file is in use Steven Rostedt
2013-07-04 12:48 ` Masami Hiramatsu
2013-07-04 3:33 ` [RFC][PATCH 3/4] tracing/kprobes: Fail to unregister if probe event files are open Steven Rostedt
2013-07-04 12:45 ` Masami Hiramatsu
2013-07-04 18:48 ` Oleg Nesterov
2013-07-05 2:53 ` Masami Hiramatsu
2013-07-05 17:26 ` Oleg Nesterov
2013-07-08 2:36 ` Masami Hiramatsu
2013-07-08 14:25 ` Oleg Nesterov
2013-07-09 8:01 ` [RFC PATCH] tracing/kprobe: Wait for disabling all running kprobe handlers Masami Hiramatsu
2013-07-09 8:07 ` Peter Zijlstra
2013-07-09 8:20 ` Masami Hiramatsu
2013-07-09 8:21 ` Peter Zijlstra
2013-07-09 8:50 ` Masami Hiramatsu
2013-07-09 9:35 ` [RFC PATCH V2] " Masami Hiramatsu
2013-07-15 18:20 ` Oleg Nesterov
2013-07-18 12:07 ` Masami Hiramatsu
2013-07-18 14:35 ` Steven Rostedt
2013-07-30 8:15 ` [RFC][PATCH 3/4] tracing/kprobes: Fail to unregister if probe event files are open Masami Hiramatsu
2013-07-31 19:49 ` Steven Rostedt
2013-07-31 20:40 ` Oleg Nesterov [this message]
2013-07-31 22:42 ` Steven Rostedt
2013-08-01 2:07 ` Steven Rostedt
2013-08-01 2:50 ` Steven Rostedt
2013-08-01 3:48 ` Masami Hiramatsu
2013-08-01 13:34 ` Oleg Nesterov
2013-08-01 13:49 ` Oleg Nesterov
2013-08-01 14:17 ` Steven Rostedt
2013-08-01 14:33 ` Oleg Nesterov
2013-08-01 14:45 ` Steven Rostedt
2013-08-01 14:46 ` Oleg Nesterov
2013-08-02 4:57 ` Masami Hiramatsu
2013-08-01 13:10 ` Oleg Nesterov
2013-07-04 3:33 ` [RFC][PATCH 4/4] tracing/uprobes: " Steven Rostedt
2013-08-01 3:40 ` Steven Rostedt
2013-08-01 14:08 ` Oleg Nesterov
2013-08-01 14:25 ` Steven Rostedt
2013-07-04 4:00 ` [RFC][PATCH 0/4] tracing/kprobes/uprobes: Fix race between opening probe event files and deleting probe Masami Hiramatsu
2013-07-04 6:14 ` Masami Hiramatsu
2013-07-12 13:09 ` Masami Hiramatsu
2013-07-12 17:53 ` Oleg Nesterov
2013-07-15 18:01 ` Oleg Nesterov
2013-07-16 16:38 ` Oleg Nesterov
2013-07-16 19:10 ` Steven Rostedt
2013-07-16 19:22 ` Oleg Nesterov
2013-07-16 19:38 ` Steven Rostedt
2013-07-17 16:03 ` Steven Rostedt
2013-07-17 17:37 ` Oleg Nesterov
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