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Commit c5a44a12 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
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tracing: Change f_start() to take event_mutex and verify i_private != NULL 

trace_format_open() and trace_format_seq_ops are racy, nothing
protects ftrace_event_call from trace_remove_event_call().

Change f_start() to take event_mutex and verify i_private != NULL,
change f_stop() to drop this lock.

This fixes nothing, but now we can change debugfs_remove("format")
callers to nullify ->i_private and fix the the problem.

Note: the usage of event_mutex is sub-optimal but simple, we can
change this later.

Link: http://lkml.kernel.org/r/20130726172543.GA3622@redhat.com



Reviewed-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent e2912b09

kernel/trace/trace_events.c

+9 −4
Original line number Diff line number Diff line
@@ -840,7 +840,7 @@ enum { 


static void *f_next(struct seq_file *m, void *v, loff_t *pos)

{

	struct ftrace_event_call *call = m->private;

	struct ftrace_event_call *call = event_file_data(m->private);

	struct list_head *common_head = &ftrace_common_fields;

	struct list_head *head = trace_get_fields(call);

	struct list_head *node = v;
@@ -872,7 +872,7 @@ static void *f_next(struct seq_file *m, void *v, loff_t *pos) 


static int f_show(struct seq_file *m, void *v)

{

	struct ftrace_event_call *call = m->private;

	struct ftrace_event_call *call = event_file_data(m->private);

	struct ftrace_event_field *field;

	const char *array_descriptor;
@@ -925,6 +925,11 @@ static void *f_start(struct seq_file *m, loff_t *pos) 
	void *p = (void *)FORMAT_HEADER;

	loff_t l = 0;



	/* ->stop() is called even if ->start() fails */

	mutex_lock(&event_mutex);

	if (!event_file_data(m->private))

		return ERR_PTR(-ENODEV);



	while (l < *pos && p)

		p = f_next(m, p, &l);
@@ -933,6 +938,7 @@ static void *f_start(struct seq_file *m, loff_t *pos) 


static void f_stop(struct seq_file *m, void *p)

{

	mutex_unlock(&event_mutex);

}



static const struct seq_operations trace_format_seq_ops = {
@@ -944,7 +950,6 @@ static const struct seq_operations trace_format_seq_ops = { 


static int trace_format_open(struct inode *inode, struct file *file)

{

	struct ftrace_event_call *call = inode->i_private;

	struct seq_file *m;

	int ret;
@@ -953,7 +958,7 @@ static int trace_format_open(struct inode *inode, struct file *file) 
		return ret;



	m = file->private_data;

	m->private = call;

	m->private = file;



	return 0;

}