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

commit 0958b33ef5a04ed91f61cef4760ac412080c4e08 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
index 4bc90965abb25f0cedd6c1cd3319377aa1b18dc2..e4340958da2dfa555a8825e58c065e1d8beb7ab4 100644 (file)
--- a/kernel/trace/trace_events_trigger.c
+++ b/kernel/trace/trace_events_trigger.c
@@ -1140,8 +1140,10 @@ register_snapshot_trigger(char *glob, struct event_trigger_ops *ops,
                          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, ops, data, file);
 }