linux-kernel - [ 20/99] tracing: Kill the unbalanced tr->ref++ in tracing_buffers

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Message-Id: <20130802100228.858921044@linuxfoundation.org>
Date:	Fri,  2 Aug 2013 18:07:33 +0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Steven Rostedt <rostedt@...dmis.org>
Subject: [ 20/99] tracing: Kill the unbalanced tr->ref++ in tracing_buffers_open()

3.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Oleg Nesterov <oleg@...hat.com>

commit e70e78e3c83b536730e31231dd9b979768d8df3c upstream.

tracing_buffers_open() does trace_array_get() and then it wrongly
inrcements tr->ref again under trace_types_lock. This means that
every caller leaks trace_array:

	# cd /sys/kernel/debug/tracing/
	# mkdir instances/X
	# true < instances/X/per_cpu/cpu0/trace_pipe_raw
	# rmdir instances/X
	rmdir: failed to remove `instances/X': Device or resource busy

Link: http://lkml.kernel.org/r/20130719153644.GA18899@redhat.com

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/trace/trace.c |    2 --
 1 file changed, 2 deletions(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4907,8 +4907,6 @@ static int tracing_buffers_open(struct i
 
 	mutex_lock(&trace_types_lock);
 
-	tr->ref++;
-
 	info->iter.tr		= tr;
 	info->iter.cpu_file	= tc->cpu;
 	info->iter.trace	= tr->current_trace;


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