--- x/net/core/flow_offload.c
+++ y/net/core/flow_offload.c
@@ -334,6 +334,7 @@ bool flow_block_cb_is_busy(flow_setup_cb
 }
 EXPORT_SYMBOL(flow_block_cb_is_busy);
 
+static DEFINE_MUTEX(setup_lock);
 int flow_block_cb_setup_simple(struct flow_block_offload *f,
 			       struct list_head *driver_block_list,
 			       flow_setup_cb_t *cb,
@@ -348,27 +349,37 @@ int flow_block_cb_setup_simple(struct fl
 
 	f->driver_block_list = driver_block_list;
 
+	mutex_lock(&setup_lock);
 	switch (f->command) {
 	case FLOW_BLOCK_BIND:
-		if (flow_block_cb_is_busy(cb, cb_ident, driver_block_list))
+		if (flow_block_cb_is_busy(cb, cb_ident, driver_block_list)) {
+			mutex_unlock(&setup_lock);
 			return -EBUSY;
+		}
 
 		block_cb = flow_block_cb_alloc(cb, cb_ident, cb_priv, NULL);
-		if (IS_ERR(block_cb))
+		if (IS_ERR(block_cb)) {
+			mutex_unlock(&setup_lock);
 			return PTR_ERR(block_cb);
+		}
 
 		flow_block_cb_add(block_cb, f);
 		list_add_tail(&block_cb->driver_list, driver_block_list);
+		mutex_unlock(&setup_lock);
 		return 0;
 	case FLOW_BLOCK_UNBIND:
 		block_cb = flow_block_cb_lookup(f->block, cb, cb_ident);
-		if (!block_cb)
+		if (!block_cb) {
+			mutex_unlock(&setup_lock);
 			return -ENOENT;
+		}
 
 		flow_block_cb_remove(block_cb, f);
 		list_del(&block_cb->driver_list);
+		mutex_unlock(&setup_lock);
 		return 0;
 	default:
+		mutex_unlock(&setup_lock);
 		return -EOPNOTSUPP;
 	}
 }