audit: allow audit code to satisfy getname requests from its names_list

Currently, if we call getname() on a userland string more than once,
we'll get multiple copies of the string and multiple audit_names
records.

Add a function that will allow the audit_names code to satisfy getname
requests using info from the audit_names list, avoiding a new allocation
and audit_names records.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namei.c b/fs/namei.c
index ec638d2..5dbc3f83 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -130,6 +130,10 @@
 	char *kname;
 	int len;
 
+	result = audit_reusename(filename);
+	if (result)
+		return result;
+
 	/* FIXME: create dedicated slabcache? */
 	result = kzalloc(sizeof(*result), GFP_KERNEL);
 	if (unlikely(!result))