function-graph: prevent more than one tracer registering
Impact: prevent crash due to multiple function graph tracers
The function graph tracer can currently only handle a single tracer
being registered. If another tracer registers with the function
graph tracer it can crash the system.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 7847806..c81a759 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -2643,6 +2643,12 @@
mutex_lock(&ftrace_lock);
+ /* we currently allow only one tracer registered at a time */
+ if (atomic_read(&ftrace_graph_active)) {
+ ret = -EBUSY;
+ goto out;
+ }
+
ftrace_suspend_notifier.notifier_call = ftrace_suspend_notifier_call;
register_pm_notifier(&ftrace_suspend_notifier);