discover: Pass UUID to discover_device_create()

Currently discover_device_create() will search for existing discover
devices by id to determine if a new device is required. However it is
possible under some circumstances for distinct devices to have the same
name. This is especially troublesome if the following network events are
seen in network_handle_nlmsg():

	- New interface, 'foo' with uuid x:x:x:x:x:x
		-> new discover device created with
			dev->device->id = 'foo'
			dev->uuid = x:x:x:x:x:x
	- New interface, 'foo' with uuid y:y:y:y:y:y
		-> existing device 'foo' found
			dev->uuid = y:y:y:y:y:y

This can occur if an interface rename event arrives *after* an old name
is reused, where temporarily Petitboot will see two distinct network
interfaces with the same name. Now the two interfaces point to the same
discover device, which can quickly result in a segfault if a 'remove'
event occurs for one of the interfaces and the discover device is freed.

To generally avoid this a 'uuid' parameter is added to
discover_device_create(), which if present allows existing devices to be
looked up by UUID rather than just their name.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>

1 files changed, 9 insertions, 4 deletions

diff --git a/discover/device-handler.c b/discover/device-handler.c
index 54a1986..70e4506 100644
--- a/discover/device-handler.c
+++ b/discover/device-handler.c
@@ -221,17 +221,22 @@ static int destroy_device(void *arg)
 }
 
 struct discover_device *discover_device_create(struct device_handler *handler,
-		const char *id)
+		const char *uuid, const char *id)
 {
 	struct discover_device *dev;
 
-	dev = device_lookup_by_id(handler, id);
+	if (uuid)
+		dev = device_lookup_by_uuid(handler, uuid);
+	else
+		dev = device_lookup_by_id(handler, id);
+
 	if (dev)
 		return dev;
 
 	dev = talloc_zero(handler, struct discover_device);
 	dev->device = talloc_zero(dev, struct device);
 	dev->device->id = talloc_strdup(dev->device, id);
+	dev->uuid = talloc_strdup(dev, uuid);
 	list_init(&dev->params);
 	list_init(&dev->boot_options);
 
@@ -1138,7 +1143,7 @@ void device_handler_process_url(struct device_handler *handler,
 		goto msg;
 	}
 
-	dev = discover_device_create(handler, event->device);
+	dev = discover_device_create(handler, mac, event->device);
 	if (pb_url->scheme == pb_url_file)
 		dev->device->type = DEVICE_TYPE_ANY;
 	ctx = device_handler_discover_context_create(handler, dev);
@@ -1171,7 +1176,7 @@ void device_handler_discover_context_commit(struct device_handler *handler,
 	struct discover_device *dev = ctx->device;
 	struct discover_boot_option *opt, *tmp;
 
-	if (!device_lookup_by_id(handler, dev->device->id))
+	if (!device_lookup_by_uuid(handler, dev->uuid))
 		device_handler_add_device(handler, dev);
 
 	/* move boot options from the context to the device */