xfrm: fix a read lock imbalance in make_blackhole

[ Upstream commit 433a19548061bb5457b6ab77ed7ea58ca6e43ddb ]

if xfrm_policy_get_afinfo returns 0, it has already released the read
lock, xfrm_policy_put_afinfo should not be called again.

Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index a15d2a0..71c80c7 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1761,7 +1761,7 @@
 
 	if (!afinfo) {
 		dst_release(dst_orig);
-		ret = ERR_PTR(-EINVAL);
+		return ERR_PTR(-EINVAL);
 	} else {
 		ret = afinfo->blackhole_route(net, dst_orig);
 	}