tracing: Have current_trace inc the trace array ref count

The current_trace updates the trace array tracer. For an instance, if the
file is opened and the instance is deleted, reading or writing to the file
will cause a use after free.

Up the ref count of the trace array when current_trace is opened.

Link: https://lkml.kernel.org/r/[email protected]
Link: https://lore.kernel.org/all/[email protected]/

Cc: [email protected]
Cc: Masami Hiramatsu <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Zheng Yejian <[email protected]>
Fixes: 8530dec ("tracing: Add tracing_check_open_get_tr()")
Tested-by: Linux Kernel Functional Testing <[email protected]>
Tested-by: Naresh Kamboju <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: rostedt

kernel/trace/trace.c

@@ -7791,10 +7791,11 @@ static const struct file_operations tracing_max_lat_fops = {
 #endif
 
 static const struct file_operations set_tracer_fops = {
-	.open		= tracing_open_generic,
+	.open		= tracing_open_generic_tr,
 	.read		= tracing_set_trace_read,
 	.write		= tracing_set_trace_write,
 	.llseek		= generic_file_llseek,
+	.release	= tracing_release_generic_tr,
 };
 
 static const struct file_operations tracing_pipe_fops = {