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 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: xen-netfront-improve-error-handling-during-initialization.patch and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Wed Dec 6 17:39:55 CET 2017

From: Ross Lagerwall ross.lagerwall@citrix.com Date: Wed, 8 Feb 2017 10:57:37 +0000 Subject: xen-netfront: Improve error handling during initialization

From: Ross Lagerwall ross.lagerwall@citrix.com

[ 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.

Signed-off-by: Ross Lagerwall ross.lagerwall@citrix.com Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/xen-netfront.c | 29 +++++++++++------------------ 1 file changed, 11 insertions(+), 18 deletions(-)

--- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -1854,27 +1854,19 @@ 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: @@ -1964,9 +1956,10 @@ 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 ross.lagerwall@citrix.com are

queue-4.9/xen-netfront-improve-error-handling-during-initialization.patch