net/virtio-user: fix leak when initialisation fails

[ upstream commit c8254ef1a96c4897293b1d1db8c8a786dfb19e9d ]

Caught with ASan.
If initialising a virtio_user port fails, we may leak the ifname passed
via a devargs.

Fixes: 4214a1b ("net/virtio-user: support changing tap interface name")

Signed-off-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Tyler Retzlaff <roretzla@linux.microsoft.com>

drivers/net/virtio/virtio_user/virtio_user_dev.c

@@ -585,11 +585,7 @@ virtio_user_dev_init(struct virtio_user_dev *dev, char *path, int queues,
 	dev->frontend_features = 0;
 	dev->unsupported_features = 0;
 	dev->backend_type = backend_type;
-
-	if (*ifname) {
-		dev->ifname = *ifname;
-		*ifname = NULL;
-	}
+	dev->ifname = *ifname;
 
 	if (virtio_user_dev_setup(dev) < 0) {
 		PMD_INIT_LOG(ERR, "(%s) backend set up fails", dev->path);
@@ -662,6 +658,7 @@ virtio_user_dev_init(struct virtio_user_dev *dev, char *path, int queues,
 		}
 	}
 
+	*ifname = NULL;
 	return 0;
 }