On Fri, 28 Aug 2026 12:34:52 -0400
Steven Rostedt <[email protected]> wrote:
> > trace_create_file("set_ftrace_filter", TRACE_MODE_WRITE, parent,
> > - ops, &ftrace_filter_fops);
> > + ops->private, &ftrace_filter_fops);
>
> But this also assumes that ops->private is always a trace_array. Which may
> someday change and we will get a hidden bug if it does.
>
> This is the exact reason I want to look deeper at it.
Something like this is more robust:
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index f9d80c7bd9f1..a417ad0f3f24 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -4786,24 +4786,48 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
}
static int
-ftrace_filter_open(struct inode *inode, struct file *file)
+__ftrace_regex_open(struct trace_array *tr, int flag,
+ struct inode *inode, struct file *file)
{
- struct ftrace_ops *ops = inode->i_private;
+ struct ftrace_ops *ops;
+ int ret;
+
+ if (trace_array_get(tr) < 0)
+ return -ENODEV;
+
+ ret = -EINVAL;
+ ops = tr->ops;
+ if (!ops)
+ goto fail;
/* Checks for tracefs lockdown */
- return ftrace_regex_open(ops,
- FTRACE_ITER_FILTER | FTRACE_ITER_DO_PROBES,
- inode, file);
+ ret = ftrace_regex_open(ops, flag, inode, file);
+ if (ret < 0)
+ goto fail;
+
+ return ret;
+ fail:
+ trace_array_put(tr);
+ return ret;
+}
+
+static int
+ftrace_filter_open(struct inode *inode, struct file *file)
+{
+ struct trace_array *tr = inode->i_private;
+
+ return __ftrace_regex_open(tr,
+ FTRACE_ITER_FILTER | FTRACE_ITER_DO_PROBES,
+ inode, file);
}
static int
ftrace_notrace_open(struct inode *inode, struct file *file)
{
- struct ftrace_ops *ops = inode->i_private;
+ struct trace_array *tr = inode->i_private;
- /* Checks for tracefs lockdown */
- return ftrace_regex_open(ops, FTRACE_ITER_NOTRACE,
- inode, file);
+ return __ftrace_regex_open(tr, FTRACE_ITER_NOTRACE,
+ inode, file);
}
/* Type for quick search ftrace basic regexes (globs) from filter_parse_regex
*/
@@ -7492,15 +7516,15 @@ static const struct file_operations
ftrace_graph_notrace_fops = {
};
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
-void ftrace_create_filter_files(struct ftrace_ops *ops,
+void ftrace_create_filter_files(struct trace_array *tr,
struct dentry *parent)
{
trace_create_file("set_ftrace_filter", TRACE_MODE_WRITE, parent,
- ops, &ftrace_filter_fops);
+ tr, &ftrace_filter_fops);
trace_create_file("set_ftrace_notrace", TRACE_MODE_WRITE, parent,
- ops, &ftrace_notrace_fops);
+ tr, &ftrace_notrace_fops);
}
/*
@@ -7525,6 +7549,7 @@ void ftrace_destroy_filter_files(struct ftrace_ops *ops)
static __init int ftrace_init_dyn_tracefs(struct dentry *d_tracer)
{
+ struct trace_array *tr;
trace_create_file("available_filter_functions", TRACE_MODE_READ,
d_tracer, NULL, &ftrace_avail_fops);
@@ -7538,7 +7563,9 @@ static __init int ftrace_init_dyn_tracefs(struct dentry
*d_tracer)
trace_create_file("touched_functions", TRACE_MODE_READ,
d_tracer, NULL, &ftrace_touched_fops);
- ftrace_create_filter_files(&global_ops, d_tracer);
+ tr = global_ops.private;
+ if (!WARN_ON(tr == NULL))
+ ftrace_create_filter_files(tr, d_tracer);
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
trace_create_file("set_graph_function", TRACE_MODE_WRITE, d_tracer,
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 74a7a50d1e78..3c111ca88e32 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -1340,7 +1340,7 @@ extern void clear_ftrace_function_probes(struct
trace_array *tr);
int register_ftrace_command(struct ftrace_func_command *cmd);
int unregister_ftrace_command(struct ftrace_func_command *cmd);
-void ftrace_create_filter_files(struct ftrace_ops *ops,
+void ftrace_create_filter_files(struct trace_array *tr,
struct dentry *parent);
void ftrace_destroy_filter_files(struct ftrace_ops *ops);
@@ -1363,11 +1363,12 @@ static inline void clear_ftrace_function_probes(struct
trace_array *tr)
{
}
+static inline void ftrace_create_filter_files(struct trace_array *tr,
+ struct dentry *parent) { }
/*
* The ops parameter passed in is usually undefined.
* This must be a macro.
*/
-#define ftrace_create_filter_files(ops, parent) do { } while (0)
#define ftrace_destroy_filter_files(ops) do { } while (0)
#endif /* CONFIG_FUNCTION_TRACER && CONFIG_DYNAMIC_FTRACE */
diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index cd37f2013758..c879d43a5fbb 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -101,7 +101,7 @@ int ftrace_create_function_files(struct trace_array *tr,
return ret;
}
- ftrace_create_filter_files(tr->ops, parent);
+ ftrace_create_filter_files(tr, parent);
return 0;
}
-- Steve
