[ 20/74] tracing: Change tracing_pipe_fops() to rely on tracing_get_cpu()

[Greg Kroah-Hartman]

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

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

From: Oleg Nesterov <oleg@xxxxxxxxxx>

commit 15544209cb0b5312e5220a9337a1fe61d1a1f2d9 upstream.

tracing_open_pipe() is racy, the memory inode->i_private points to
can be already freed.

Change debugfs_create_file("trace_pipe", data) callers to to pass
"data = tr", tracing_open_pipe() can use tracing_get_cpu().

Link: http://lkml.kernel.org/r/20130723152557.GA23717@xxxxxxxxxx

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/trace/trace.c |   16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3950,8 +3950,7 @@ tracing_max_lat_write(struct file *filp,
 
 static int tracing_open_pipe(struct inode *inode, struct file *filp)
 {
-	struct trace_cpu *tc = inode->i_private;
-	struct trace_array *tr = tc->tr;
+	struct trace_array *tr = inode->i_private;
 	struct trace_iterator *iter;
 	int ret = 0;
 
@@ -3997,9 +3996,9 @@ static int tracing_open_pipe(struct inod
 	if (trace_clocks[tr->clock_id].in_ns)
 		iter->iter_flags |= TRACE_FILE_TIME_IN_NS;
 
-	iter->cpu_file = tc->cpu;
-	iter->tr = tc->tr;
-	iter->trace_buffer = &tc->tr->trace_buffer;
+	iter->tr = tr;
+	iter->trace_buffer = &tr->trace_buffer;
+	iter->cpu_file = tracing_get_cpu(inode);
 	mutex_init(&iter->mutex);
 	filp->private_data = iter;
 
@@ -4022,8 +4021,7 @@ fail:
 static int tracing_release_pipe(struct inode *inode, struct file *file)
 {
 	struct trace_iterator *iter = file->private_data;
-	struct trace_cpu *tc = inode->i_private;
-	struct trace_array *tr = tc->tr;
+	struct trace_array *tr = inode->i_private;
 
 	mutex_lock(&trace_types_lock);
 
@@ -5563,7 +5561,7 @@ tracing_init_debugfs_percpu(struct trace
 
 	/* per cpu trace_pipe */
 	trace_create_cpu_file("trace_pipe", 0444, d_cpu,
-				&data->trace_cpu, cpu, &tracing_pipe_fops);
+				tr, cpu, &tracing_pipe_fops);
 
 	/* per cpu trace */
 	trace_create_cpu_file("trace", 0644, d_cpu,
@@ -6149,7 +6147,7 @@ init_tracer_debugfs(struct trace_array *
 			(void *)&tr->trace_cpu, &tracing_fops);
 
 	trace_create_file("trace_pipe", 0444, d_tracer,
-			(void *)&tr->trace_cpu, &tracing_pipe_fops);
+			  tr, &tracing_pipe_fops);
 
 	trace_create_file("buffer_size_kb", 0644, d_tracer,
 			(void *)&tr->trace_cpu, &tracing_entries_fops);


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