ematch: Fix auto-loading of ematch modules.

commit 34eea79e upstream.

In tcf_em_validate(), after calling request_module() to load the
kind-specific module, set em->ops to NULL before returning -EAGAIN, so
that module_put() is not called again by tcf_em_tree_destroy().
Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Acked-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

net/sched/ematch.c

@@ -227,6 +227,7 @@ static int tcf_em_validate(struct tcf_proto *tp,
 				 * to replay the request.
 				 */
 				module_put(em->ops->owner);
+				em->ops = NULL;
 				err = -EAGAIN;
 			}
 #endif