tracing/trigger: Fix to return error if failed to alloc snapshot

Fix register_snapshot_trigger() to return error code if it failed to
allocate a snapshot instead of 0 (success). Unless that, it will register
snapshot trigger without an error.

Link: https://lore.kernel.org/linux-trace-kernel/170622977792.270660.2789298642759362200.stgit@devnote2
Fixes: 0bbe7f719985 ("tracing: Fix the race between registering 'snapshot' event trigger and triggering 'snapshot' operation")
Cc: stable@vger.kernel.org
Cc: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 46439e3bcec4d20b45ae8202d7a68888778fa208..b33c3861fbbbf303e78f740a0fcc41caa2a77d77 100644 (file)
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1470,8 +1470,10 @@ register_snapshot_trigger(char *glob,
                          struct event_trigger_data *data,
                          struct trace_event_file *file)
 {
-       if (tracing_alloc_snapshot_instance(file->tr) != 0)
-               return 0;
+       int ret = tracing_alloc_snapshot_instance(file->tr);
+
+       if (ret < 0)
+               return ret;
 
        return register_trigger(glob, data, file);
 }