[ 20/99] tracing: Kill the unbalanced tr->ref++ in tracing_buffers_open()

From: Greg Kroah-Hartman
Date: Fri Aug 02 2013 - 06:08:29 EST

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


From: Oleg Nesterov <oleg@xxxxxxxxxx>

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@xxxxxxxxxx

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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


- tr->ref++;
info->iter.tr = tr;
info->iter.cpu_file = tc->cpu;
info->iter.trace = tr->current_trace;

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