3.16.61-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Ross Lagerwall ross.lagerwall@citrix.com
commit f599c64fdf7d9c108e8717fb04bc41c680120da4 upstream.
When a netfront device is set up it registers a netdev fairly early on, before it has set up the queues and is actually usable. A userspace tool like NetworkManager will immediately try to open it and access its state as soon as it appears. The bug can be reproduced by hotplugging VIFs until the VM runs out of grant refs. It registers the netdev but fails to set up any queues (since there are no more grant refs). In the meantime, NetworkManager opens the device and the kernel crashes trying to access the queues (of which there are none).
Fix this in two ways: * For initial setup, register the netdev much later, after the queues are setup. This avoids the race entirely. * During a suspend/resume cycle, the frontend reconnects to the backend and the queues are recreated. It is possible (though highly unlikely) to race with something opening the device and accessing the queues after they have been destroyed but before they have been recreated. Extend the region covered by the rtnl semaphore to protect against this race. There is a possibility that we fail to recreate the queues so check for this in the open function.
Signed-off-by: Ross Lagerwall ross.lagerwall@citrix.com Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Signed-off-by: Juergen Gross jgross@suse.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/net/xen-netfront.c | 46 ++++++++++++++++++++------------------ 1 file changed, 24 insertions(+), 22 deletions(-)
--- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -369,6 +369,9 @@ static int xennet_open(struct net_device unsigned int i = 0; struct netfront_queue *queue = NULL;
+ if (!np->queues) + return -ENODEV; + for (i = 0; i < num_queues; ++i) { queue = &np->queues[i]; napi_enable(&queue->napi); @@ -1394,18 +1397,8 @@ static int netfront_probe(struct xenbus_ #ifdef CONFIG_SYSFS info->netdev->sysfs_groups[0] = &xennet_dev_group; #endif - err = register_netdev(info->netdev); - if (err) { - pr_warn("%s: register_netdev err=%d\n", __func__, err); - goto fail; - }
return 0; - - fail: - xennet_free_netdev(netdev); - dev_set_drvdata(&dev->dev, NULL); - return err; }
static void xennet_end_access(int ref, void *page) @@ -1779,8 +1772,6 @@ static void xennet_destroy_queues(struct { unsigned int i;
- rtnl_lock(); - for (i = 0; i < info->netdev->real_num_tx_queues; i++) { struct netfront_queue *queue = &info->queues[i];
@@ -1789,8 +1780,6 @@ static void xennet_destroy_queues(struct netif_napi_del(&queue->napi); }
- rtnl_unlock(); - kfree(info->queues); info->queues = NULL; } @@ -1806,8 +1795,6 @@ static int xennet_create_queues(struct n if (!info->queues) return -ENOMEM;
- rtnl_lock(); - for (i = 0; i < *num_queues; i++) { struct netfront_queue *queue = &info->queues[i];
@@ -1816,7 +1803,7 @@ static int xennet_create_queues(struct n
ret = xennet_init_queue(queue); if (ret < 0) { - dev_warn(&info->netdev->dev, + dev_warn(&info->xbdev->dev, "only created %d queues\n", i); *num_queues = i; break; @@ -1830,10 +1817,8 @@ static int xennet_create_queues(struct n
netif_set_real_num_tx_queues(info->netdev, *num_queues);
- rtnl_unlock(); - if (*num_queues == 0) { - dev_err(&info->netdev->dev, "no queues\n"); + dev_err(&info->xbdev->dev, "no queues\n"); return -EINVAL; } return 0; @@ -1875,6 +1860,7 @@ static int talk_to_netback(struct xenbus goto out; }
+ rtnl_lock(); if (info->queues) xennet_destroy_queues(info);
@@ -1885,6 +1871,7 @@ static int talk_to_netback(struct xenbus info->queues = NULL; goto out; } + rtnl_unlock();
/* Create shared ring, alloc event channel -- for each queue */ for (i = 0; i < num_queues; ++i) { @@ -1978,8 +1965,10 @@ abort_transaction_no_dev_fatal: xenbus_transaction_end(xbt, 1); destroy_ring: xennet_disconnect_backend(info); + rtnl_lock(); xennet_destroy_queues(info); out: + rtnl_unlock(); device_unregister(&dev->dev); return err; } @@ -2015,6 +2004,15 @@ static int xennet_connect(struct net_dev netdev_update_features(dev); rtnl_unlock();
+ if (dev->reg_state == NETREG_UNINITIALIZED) { + err = register_netdev(dev); + if (err) { + pr_warn("%s: register_netdev err=%d\n", __func__, err); + device_unregister(&np->xbdev->dev); + return err; + } + } + /* * All public and private state should now be sane. Get * ready to start sending and receiving packets and give the driver @@ -2284,10 +2282,14 @@ static int xennet_remove(struct xenbus_d
xennet_disconnect_backend(info);
- unregister_netdev(info->netdev); + if (info->netdev->reg_state == NETREG_REGISTERED) + unregister_netdev(info->netdev);
- if (info->queues) + if (info->queues) { + rtnl_lock(); xennet_destroy_queues(info); + rtnl_unlock(); + } xennet_free_netdev(info->netdev);
return 0;