perf cgroup: Fix leak of file reference count

In perf_cgroup_connect(), fput_light() is missing in a failure path.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4D6F3461.6060406@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_event.c

@@ -404,8 +404,10 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event,
 		return -EBADF;
 
 	css = cgroup_css_from_dir(file, perf_subsys_id);
-	if (IS_ERR(css))
-		return PTR_ERR(css);
+	if (IS_ERR(css)) {
+		ret = PTR_ERR(css);
+		goto out;
+	}
 
 	cgrp = container_of(css, struct perf_cgroup, css);
 	event->cgrp = cgrp;
@@ -422,6 +424,7 @@ static inline int perf_cgroup_connect(int fd, struct perf_event *event,
 		/* must be done before we fput() the file */
 		perf_get_cgroup(event);
 	}
+out:
 	fput_light(file, fput_needed);
 	return ret;
 }