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From: Steven Rostedt <rostedt@goodmis.org>
To: Oleg Nesterov <oleg@redhat.com>
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 18:42:28 -0400	[thread overview]
Message-ID: <1375310548.5418.21.camel@gandalf.local.home> (raw)
In-Reply-To: <20130731204003.GA30188@redhat.com>

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
patch set.

-- Steve



  reply	other threads:[~2013-07-31 22:42 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
2013-07-31 22:42       ` Steven Rostedt [this message]
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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