[CIFS] Add destroy routine for dns_resolver

Otherwise, we're leaking the payload memory.

CC: Stable Kernel <stable@vger.kernel.org>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/dns_resolve.c b/fs/cifs/dns_resolve.c
index f730ef3..a2e0673 100644
--- a/fs/cifs/dns_resolve.c
+++ b/fs/cifs/dns_resolve.c
@@ -47,11 +47,18 @@
 	return rc;
 }
 
+static void
+dns_resolver_destroy(struct key *key)
+{
+	kfree(key->payload.data);
+}
+
 struct key_type key_type_dns_resolver = {
 	.name        = "dns_resolver",
 	.def_datalen = sizeof(struct in_addr),
 	.describe    = user_describe,
 	.instantiate = dns_resolver_instantiate,
+	.destroy     = dns_resolver_destroy,
 	.match       = user_match,
 };