net: free_netdev: exit earlier if dummy

JIRA: https://issues.redhat.com/browse/RHEL-59092

commit f8d0567
Author: Breno Leitao <leitao@debian.org>
Date:   Mon Apr 22 05:38:55 2024 -0700

    net: free_netdev: exit earlier if dummy

    For dummy devices, exit earlier at free_netdev() instead of executing
    the whole function. This is necessary, because dummy devices are
    special, and shouldn't have the second part of the function executed.

    Otherwise reg_state, which is NETREG_DUMMY, will be overwritten and
    there will be no way to identify that this is a dummy device. Also, this
    device do not need the final put_device(), since dummy devices are not
    registered (through register_netdevice()), where the device reference is
    increased (at netdev_register_kobject()/device_add()).

    Suggested-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Breno Leitao <leitao@debian.org>
    Reviewed-by: Ido Schimmel <idosch@nvidia.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Izabela Bakollari <ibakolla@redhat.com>

Author: Izabela Bakollari

net/core/dev.c

@@ -10765,7 +10765,8 @@ void free_netdev(struct net_device *dev)
 	dev->xdp_bulkq = NULL;
 
 	/*  Compatibility with error handling in drivers */
-	if (dev->reg_state == NETREG_UNINITIALIZED) {
+	if (dev->reg_state == NETREG_UNINITIALIZED ||
+	    dev->reg_state == NETREG_DUMMY) {
 		netdev_freemem(dev);
 		return;
 	}