tracing: Increase trace array ref count on enable and filter files

When the trace event enable and filter files are opened, increment the
trace array ref counter, otherwise they can be accessed when the trace
array is being deleted. The ref counter keeps the trace array from being
deleted while those files are 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]>
Fixes: 8530dec ("tracing: Add tracing_check_open_get_tr()")
Tested-by: Linux Kernel Functional Testing <[email protected]>
Tested-by: Naresh Kamboju <[email protected]>
Reported-by: Zheng Yejian <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

kernel/trace/trace.c

@@ -4973,6 +4973,33 @@ int tracing_open_generic_tr(struct inode *inode, struct file *filp)
 	return 0;
 }
 
+/*
+ * The private pointer of the inode is the trace_event_file.
+ * Update the tr ref count associated to it.
+ */
+int tracing_open_file_tr(struct inode *inode, struct file *filp)
+{
+	struct trace_event_file *file = inode->i_private;
+	int ret;
+
+	ret = tracing_check_open_get_tr(file->tr);
+	if (ret)
+		return ret;
+
+	filp->private_data = inode->i_private;
+
+	return 0;
+}
+
+int tracing_release_file_tr(struct inode *inode, struct file *filp)
+{
+	struct trace_event_file *file = inode->i_private;
+
+	trace_array_put(file->tr);
+
+	return 0;
+}
+
 static int tracing_mark_open(struct inode *inode, struct file *filp)
 {
 	stream_open(inode, filp);

kernel/trace/trace.h

@@ -610,6 +610,8 @@ void tracing_reset_all_online_cpus(void);
 void tracing_reset_all_online_cpus_unlocked(void);
 int tracing_open_generic(struct inode *inode, struct file *filp);
 int tracing_open_generic_tr(struct inode *inode, struct file *filp);
+int tracing_open_file_tr(struct inode *inode, struct file *filp);
+int tracing_release_file_tr(struct inode *inode, struct file *filp);
 bool tracing_is_disabled(void);
 bool tracer_tracing_is_on(struct trace_array *tr);
 void tracer_tracing_on(struct trace_array *tr);

kernel/trace/trace_events.c

@@ -2103,9 +2103,10 @@ static const struct file_operations ftrace_set_event_notrace_pid_fops = {
 };
 
 static const struct file_operations ftrace_enable_fops = {
-	.open = tracing_open_generic,
+	.open = tracing_open_file_tr,
 	.read = event_enable_read,
 	.write = event_enable_write,
+	.release = tracing_release_file_tr,
 	.llseek = default_llseek,
 };
 
@@ -2122,9 +2123,10 @@ static const struct file_operations ftrace_event_id_fops = {
 };
 
 static const struct file_operations ftrace_event_filter_fops = {
-	.open = tracing_open_generic,
+	.open = tracing_open_file_tr,
 	.read = event_filter_read,
 	.write = event_filter_write,
+	.release = tracing_release_file_tr,
 	.llseek = default_llseek,
 };