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: d2afd57a4b96 ("tracing/ftrace: Allow instances to have their own function probes")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 76aa04d4c925..b4a751e8f9d6 100644
--- a/kernel/trace/trace_stack.c
+++ b/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);