ftrace: Fix regression with module command in stack_trace_filter

When doing the following command:

 # echo ":mod:kvm_intel" > /sys/kernel/tracing/stack_trace_filter

it triggered a crash.

This happened with the clean up of probes. It required all callers to the
regex function (doing ftrace filtering) to have ops->private be a pointer to
a trace_array. But for the stack tracer, that is not the case.

Allow for the ops->private to be NULL, and change the function command
callbacks to handle the trace_array pointer being NULL as well.

Fixes: d2afd57a ("tracing/ftrace: Allow instances to have their own function probes")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

kernel/trace/ftrace.c

@@ -4337,9 +4337,6 @@ static int ftrace_process_regex(struct ftrace_iterator *iter,
 
 	command = strsep(&next, ":");
 
-	if (WARN_ON_ONCE(!tr))
-		return -EINVAL;
-
 	mutex_lock(&ftrace_cmd_mutex);
 	list_for_each_entry(p, &ftrace_commands, list) {
 		if (strcmp(p->name, command) == 0) {

kernel/trace/trace.c

@@ -6881,6 +6881,9 @@ ftrace_trace_snapshot_callback(struct trace_array *tr, struct ftrace_hash *hash,
 	char *number;
 	int ret;
 
+	if (!tr)
+		return -ENODEV;
+
 	/* hash funcs only work with set_ftrace_filter */
 	if (!enable)
 		return -EINVAL;

kernel/trace/trace_functions.c

@@ -654,6 +654,9 @@ ftrace_trace_onoff_callback(struct trace_array *tr, struct ftrace_hash *hash,
 {
 	struct ftrace_probe_ops *ops;
 
+	if (!tr)
+		return -ENODEV;
+
 	/* we register both traceon and traceoff to this callback */
 	if (strcmp(cmd, "traceon") == 0)
 		ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;
@@ -670,6 +673,9 @@ ftrace_stacktrace_callback(struct trace_array *tr, struct ftrace_hash *hash,
 {
 	struct ftrace_probe_ops *ops;
 
+	if (!tr)
+		return -ENODEV;
+
 	ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;
 
 	return ftrace_trace_probe_callback(tr, ops, hash, glob, cmd,
@@ -682,6 +688,9 @@ ftrace_dump_callback(struct trace_array *tr, struct ftrace_hash *hash,
 {
 	struct ftrace_probe_ops *ops;
 
+	if (!tr)
+		return -ENODEV;
+
 	ops = &dump_probe_ops;
 
 	/* Only dump once. */
@@ -695,6 +704,9 @@ ftrace_cpudump_callback(struct trace_array *tr, struct ftrace_hash *hash,
 {
 	struct ftrace_probe_ops *ops;
 
+	if (!tr)
+		return -ENODEV;
+
 	ops = &cpudump_probe_ops;
 
 	/* Only dump once. */

kernel/trace/trace_stack.c

@@ -409,7 +409,9 @@ static const struct file_operations stack_trace_fops = {
 static int
 stack_trace_filter_open(struct inode *inode, struct file *file)
 {
-	return ftrace_regex_open(&trace_ops, FTRACE_ITER_FILTER,
+	struct ftrace_ops *ops = inode->i_private;
+
+	return ftrace_regex_open(ops, FTRACE_ITER_FILTER,
 				 inode, file);
 }
 
@@ -476,7 +478,7 @@ static __init int stack_trace_init(void)
 			NULL, &stack_trace_fops);
 
 	trace_create_file("stack_trace_filter", 0444, d_tracer,
-			NULL, &stack_trace_filter_fops);
+			  &trace_ops, &stack_trace_filter_fops);
 
 	if (stack_trace_filter_buf[0])
 		ftrace_set_early_filter(&trace_ops, stack_trace_filter_buf, 1);