xfrm: Take xfrm_state_lock in xfrm_migrate_state_find

A comment on xfrm_migrate_state_find() says that xfrm_state_lock
is held. This is apparently not the case, but we need it to
traverse through the state lists.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

net/xfrm/xfrm_state.c

@@ -1215,11 +1215,12 @@ static struct xfrm_state *xfrm_state_clone(struct xfrm_state *orig, int *errp)
 	return NULL;
 }
 
-/* net->xfrm.xfrm_state_lock is held */
 struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *net)
 {
 	unsigned int h;
-	struct xfrm_state *x;
+	struct xfrm_state *x = NULL;
+
+	spin_lock_bh(&net->xfrm.xfrm_state_lock);
 
 	if (m->reqid) {
 		h = xfrm_dst_hash(net, &m->old_daddr, &m->old_saddr,
@@ -1236,7 +1237,7 @@ struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *n
 					     m->old_family))
 				continue;
 			xfrm_state_hold(x);
-			return x;
+			break;
 		}
 	} else {
 		h = xfrm_src_hash(net, &m->old_daddr, &m->old_saddr,
@@ -1251,11 +1252,13 @@ struct xfrm_state *xfrm_migrate_state_find(struct xfrm_migrate *m, struct net *n
 					     m->old_family))
 				continue;
 			xfrm_state_hold(x);
-			return x;
+			break;
 		}
 	}
 
-	return NULL;
+	spin_unlock_bh(&net->xfrm.xfrm_state_lock);
+
+	return x;
 }
 EXPORT_SYMBOL(xfrm_migrate_state_find);