net: mgmt: Fix memory corruption in wait_on_iface

The net_mgmt subsystem offers a function which waits (blocks)
until a specified net event occurs. An event callback is
pushed to the stack, then added to the net_mgmt_event_callback
list. If the event occurs, the net_mgmt thread calls the
callback and deletes the callback from the list. However, if
the event does not occur within the timeout specified when
invoking mgmt_event_wait_call() the function will return,
corrupting the callback structure the stack is reused.

This PR fixes the issue by deleting the callback before exiting
in case the event does not occur.

Signed-off-by: Bjarki Arge Andreasen <bjarkix123@gmail.com>

Author: Bjarki Arge Andreasen

subsys/net/ip/net_mgmt.c

@@ -236,29 +236,32 @@ static int mgmt_event_wait_call(struct net_if *iface,
 	net_mgmt_add_event_callback(&sync);
 
 	ret = k_sem_take(sync.sync_call, timeout);
-	if (ret == -EAGAIN) {
-		ret = -ETIMEDOUT;
-	} else {
-		if (!ret) {
-			if (raised_event) {
-				*raised_event = sync.raised_event;
-			}
+	if (ret < 0) {
+		if (ret == -EAGAIN) {
+			ret = -ETIMEDOUT;
+		}
 
-			if (event_iface) {
-				*event_iface = sync_data.iface;
-			}
+		net_mgmt_del_event_callback(&sync);
+		return ret;
+	}
+
+	if (raised_event) {
+		*raised_event = sync.raised_event;
+	}
+
+	if (event_iface) {
+		*event_iface = sync_data.iface;
+	}
 
 #ifdef CONFIG_NET_MGMT_EVENT_INFO
-			if (info) {
-				*info = sync.info;
+	if (info) {
+		*info = sync.info;
 
-				if (info_length) {
-					*info_length = sync.info_length;
-				}
-			}
-#endif /* CONFIG_NET_MGMT_EVENT_INFO */
+		if (info_length) {
+			*info_length = sync.info_length;
 		}
 	}
+#endif /* CONFIG_NET_MGMT_EVENT_INFO */
 
 	return ret;
 }