[PATCH v4 01/12] device: protect socket_init with device_update_lock

[Julian Orth <ju.orth@gmail.com>]

`set_port` in netlink.c races with `open` in device.c. This can cause
the following code flow:

* thread 1: set_port: device is not up
* thread 2: device is opened
* thread 2: open: called and calls socket_init with the original port
* thread 1: set_port: sets incoming_port to the new port and returns

incoming_port is then inconsistent. While this is not particularly
critical, it will become more critial when ste_port also sets the
transit namespace.
---
 src/device.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/device.c b/src/device.c
index 72b93c7..49f9634 100644
--- a/src/device.c
+++ b/src/device.c
@@ -53,17 +53,18 @@ static int open(struct net_device *dev)
 #endif
 #endif
 
+	mutex_lock(&wg->device_update_lock);
 	ret = wg_socket_init(wg, wg->incoming_port);
 	if (ret < 0)
-		return ret;
-	mutex_lock(&wg->device_update_lock);
+		goto out;
 	list_for_each_entry (peer, &wg->peer_list, peer_list) {
 		wg_packet_send_staged_packets(peer);
 		if (peer->persistent_keepalive_interval)
 			wg_packet_send_keepalive(peer);
 	}
+out:
 	mutex_unlock(&wg->device_update_lock);
-	return 0;
+	return ret;
 }
 
 #if defined(CONFIG_PM_SLEEP) && !defined(CONFIG_ANDROID)
-- 
2.19.0

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