tracing: Protect ftrace_trace_arrays list in trace_events.c

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@google.com

Cc: Vaibhav Nagarnaik <vnagarnaik@google.com>
Cc: David Sharp <dhsharp@google.com>
Cc: Alexander Z Lam <lambchop468@gmail.com>
Cc: stable@vger.kernel.org # 3.10
Signed-off-by: Alexander Z Lam <azl@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

3 files changed, 13 insertions, 2 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e04e7119633d..e36da7ff59bf 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -266,7 +266,7 @@ static struct tracer		*trace_types __read_mostly;
 /*
  * 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
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index a88939e666b7..2c3cba59552d 100644
--- 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.
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 5892470bc2ee..35c6f23c71b2 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1008,6 +1008,7 @@ static int subsystem_open(struct inode *inode, struct file *filp)
         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) {
@@ -1023,6 +1024,7 @@ static int subsystem_open(struct inode *inode, struct file *filp)
         }
  exit_loop:
         mutex_unlock(&event_mutex);
+        mutex_unlock(&trace_types_lock);
 
         if (!system)
                 return -ENODEV;
@@ -1617,6 +1619,7 @@ static void __add_event_to_tracers(struct ftrace_event_call *call,
 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);
@@ -1624,11 +1627,13 @@ int trace_add_event_call(struct ftrace_event_call *call)
                 __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)
 {
@@ -1640,11 +1645,13 @@ static void __trace_remove_event_call(struct ftrace_event_call *call)
 /* 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)                       \
@@ -1788,6 +1795,7 @@ static int trace_module_notify(struct notifier_block *self,
 {
         struct module *mod = data;
 
+        mutex_lock(&trace_types_lock);
         mutex_lock(&event_mutex);
         switch (val) {
         case MODULE_STATE_COMING:
@@ -1798,6 +1806,7 @@ static int trace_module_notify(struct notifier_block *self,
                 break;
         }
         mutex_unlock(&event_mutex);
+        mutex_unlock(&trace_types_lock);
 
         return 0;
 }