[ 099/103] tracing: Protect ftrace_trace_arrays list in trace_events.c

[Greg Kroah-Hartman]

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

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

From: Alexander Z Lam <azl@xxxxxxxxxx>

commit a82274151af2b075163e3c42c828529dee311487 upstream.

There are multiple places where the ftrace_trace_arrays list is accessed in
trace_events.c without the trace_types_lock held.

Link: http://lkml.kernel.org/r/1372732674-22726-1-git-send-email-azl@xxxxxxxxxx

Signed-off-by: Alexander Z Lam <azl@xxxxxxxxxx>
Cc: Vaibhav Nagarnaik <vnagarnaik@xxxxxxxxxx>
Cc: David Sharp <dhsharp@xxxxxxxxxx>
Cc: Alexander Z Lam <lambchop468@xxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 kernel/trace/trace.c        |    2 +-
 kernel/trace/trace.h        |    2 ++
 kernel/trace/trace_events.c |   11 ++++++++++-
 3 files changed, 13 insertions(+), 2 deletions(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -240,7 +240,7 @@ static struct tracer		*trace_types __rea
 /*
  * trace_types_lock is used to protect the trace_types list.
  */
-static DEFINE_MUTEX(trace_types_lock);
+DEFINE_MUTEX(trace_types_lock);
 
 /*
  * serialize the access of the ring buffer
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -224,6 +224,8 @@ enum {
 
 extern struct list_head ftrace_trace_arrays;
 
+extern struct mutex trace_types_lock;
+
 /*
  * The global tracer (top) should be the first trace array added,
  * but we check the flag anyway.
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1011,6 +1011,7 @@ static int subsystem_open(struct inode *
 	int ret;
 
 	/* Make sure the system still exists */
+	mutex_lock(&trace_types_lock);
 	mutex_lock(&event_mutex);
 	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
 		list_for_each_entry(dir, &tr->systems, list) {
@@ -1026,6 +1027,7 @@ static int subsystem_open(struct inode *
 	}
  exit_loop:
 	mutex_unlock(&event_mutex);
+	mutex_unlock(&trace_types_lock);
 
 	if (!system)
 		return -ENODEV;
@@ -1620,6 +1622,7 @@ static void __add_event_to_tracers(struc
 int trace_add_event_call(struct ftrace_event_call *call)
 {
 	int ret;
+	mutex_lock(&trace_types_lock);
 	mutex_lock(&event_mutex);
 
 	ret = __register_event(call, NULL);
@@ -1627,11 +1630,13 @@ int trace_add_event_call(struct ftrace_e
 		__add_event_to_tracers(call, NULL);
 
 	mutex_unlock(&event_mutex);
+	mutex_unlock(&trace_types_lock);
 	return ret;
 }
 
 /*
- * Must be called under locking both of event_mutex and trace_event_sem.
+ * Must be called under locking of trace_types_lock, event_mutex and
+ * trace_event_sem.
  */
 static void __trace_remove_event_call(struct ftrace_event_call *call)
 {
@@ -1643,11 +1648,13 @@ static void __trace_remove_event_call(st
 /* Remove an event_call */
 void trace_remove_event_call(struct ftrace_event_call *call)
 {
+	mutex_lock(&trace_types_lock);
 	mutex_lock(&event_mutex);
 	down_write(&trace_event_sem);
 	__trace_remove_event_call(call);
 	up_write(&trace_event_sem);
 	mutex_unlock(&event_mutex);
+	mutex_unlock(&trace_types_lock);
 }
 
 #define for_each_event(event, start, end)			\
@@ -1791,6 +1798,7 @@ static int trace_module_notify(struct no
 {
 	struct module *mod = data;
 
+	mutex_lock(&trace_types_lock);
 	mutex_lock(&event_mutex);
 	switch (val) {
 	case MODULE_STATE_COMING:
@@ -1801,6 +1809,7 @@ static int trace_module_notify(struct no
 		break;
 	}
 	mutex_unlock(&event_mutex);
+	mutex_unlock(&trace_types_lock);
 
 	return 0;
 }


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