Patch "xen-netfront: Improve error handling during initialization" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

xen-netfront: Improve error handling during initialization

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
xen-netfront-improve-error-handling-during-initialization.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Ross Lagerwall <[email protected]>
Date: Wed, 8 Feb 2017 10:57:37 +0000
Subject: xen-netfront: Improve error handling during initialization

From: Ross Lagerwall <[email protected]>

[ Upstream commit e2e004acc7cbe3c531e752a270a74e95cde3ea48 ]

This fixes a crash when running out of grant refs when creating many queues across many netdevs.

* If creating queues fails (i.e. there are no grant refs available), call xenbus_dev_fatal() to ensure that the xenbus device is set to the closed state.
* If no queues are created, don't call xennet_disconnect_backend as netdev->real_num_tx_queues will not have been set correctly.
* If setup_netfront() fails, ensure that all the queues created are cleaned up, not just those that have been set up.
* If any queues were set up and an error occurs, call xennet_destroy_queues() to clean up the napi context.
* If any fatal error occurs, unregister and destroy the netdev to avoid leaving around a half setup network device.

---
 drivers/net/xen-netfront.c |   29 +++++++++++------------------
 1 file changed, 11 insertions(+), 18 deletions(-)

@@ -1840,27 +1840,19 @@ static int talk_to_netback(struct xenbus
 		xennet_destroy_queues(info);
 
 	err = xennet_create_queues(info, &num_queues);
-	if (err < 0)
-		goto destroy_ring;
+	if (err < 0) {
+		xenbus_dev_fatal(dev, err, "creating queues");
+		kfree(info->queues);
+		info->queues = NULL;
+		goto out;
+	}
 
 	/* Create shared ring, alloc event channel -- for each queue */
 	for (i = 0; i < num_queues; ++i) {
 		queue = &info->queues[i];
 		err = setup_netfront(dev, queue, feature_split_evtchn);
-		if (err) {
-			/* setup_netfront() will tidy up the current
-			 * queue on error, but we need to clean up
-			 * those already allocated.
-			 */
-			if (i > 0) {
-				rtnl_lock();
-				netif_set_real_num_tx_queues(info->netdev, i);
-				rtnl_unlock();
-				goto destroy_ring;
-			} else {
-				goto out;
-			}
-		}
+		if (err)
+			goto destroy_ring;
 	}
 
 again:

@@ -1950,9 +1942,10 @@ abort_transaction_no_dev_fatal:
 	xenbus_transaction_end(xbt, 1);
  destroy_ring:
 	xennet_disconnect_backend(info);
-	kfree(info->queues);
-	info->queues = NULL;
+	xennet_destroy_queues(info);
  out:
+	unregister_netdev(info->netdev);
+	xennet_free_netdev(info->netdev);
 	return err;
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/xen-netfront-improve-error-handling-during-initialization.patch