tracing: Simplify event_enable_func() goto out_free logic

The event_enable_func() function allocates the data descriptor early in
the function just to assign its data->count value via:

  kstrtoul(number, 0, &data->count);

This makes the code more complex as there are several error paths before
the data descriptor is actually used. This means there needs to be a
goto out_free; to clean it up.

Use a local variable "count" to do the update and move the data allocation
just before it is used. This removes the "out_free" label as the data can
be freed on the failure path of where it is used.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/20241219201345.190820140@goodmis.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index f4eff49faef64adb2883e76d4a8891d0e6a6cd41..43e9545b5cf31e957f6217d91bf5d02edc855481 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3758,6 +3758,7 @@ event_enable_func(struct trace_array *tr, struct ftrace_hash *hash,
        struct trace_event_file *file;
        struct ftrace_probe_ops *ops;
        struct event_probe_data *data;
+       unsigned long count = -1;
        const char *system;
        const char *event;
        char *number;
@@ -3798,14 +3799,6 @@ event_enable_func(struct trace_array *tr, struct ftrace_hash *hash,
 
        ret = -ENOMEM;
 
-       data = kzalloc(sizeof(*data), GFP_KERNEL);
-       if (!data)
-               goto out;
-
-       data->enable = enable;
-       data->count = -1;
-       data->file = file;
-
        if (!param)
                goto out_reg;
 
@@ -3813,28 +3806,36 @@ event_enable_func(struct trace_array *tr, struct ftrace_hash *hash,
 
        ret = -EINVAL;
        if (!strlen(number))
-               goto out_free;
+               goto out;
 
        /*
         * We use the callback data field (which is a pointer)
         * as our counter.
         */
-       ret = kstrtoul(number, 0, &data->count);
+       ret = kstrtoul(number, 0, &count);
        if (ret)
-               goto out_free;
+               goto out;
 
  out_reg:
        /* Don't let event modules unload while probe registered */
        ret = trace_event_try_get_ref(file->event_call);
        if (!ret) {
                ret = -EBUSY;
-               goto out_free;
+               goto out;
        }
 
        ret = __ftrace_event_enable_disable(file, 1, 1);
        if (ret < 0)
                goto out_put;
 
+       data = kzalloc(sizeof(*data), GFP_KERNEL);
+       if (!data)
+               goto out_put;
+
+       data->enable = enable;
+       data->count = count;
+       data->file = file;
+
        ret = register_ftrace_function_probe(glob, tr, ops, data);
        /*
         * The above returns on success the # of functions enabled,
@@ -3853,11 +3854,10 @@ event_enable_func(struct trace_array *tr, struct ftrace_hash *hash,
        return ret;
 
  out_disable:
+       kfree(data);
        __ftrace_event_enable_disable(file, 0, 1);
  out_put:
        trace_event_put_ref(file->event_call);
- out_free:
-       kfree(data);
        goto out;
 }