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authorAndrea Righi <andrea.righi@canonical.com>2020-07-24 11:59:10 +0300
committerDavid S. Miller <davem@davemloft.net>2020-07-25 03:02:01 +0300
commitc2c633106453611be07821f53dff9e93a9d1c3f0 (patch)
tree8061aa72536c8acdca4d693a078a66129de423dd
parentc2b69f24ebd166a13cdc9909b50f33228895998b (diff)
downloadlinux-sunxi-c2c633106453611be07821f53dff9e93a9d1c3f0.tar.xz
xen-netfront: fix potential deadlock in xennet_remove()
There's a potential race in xennet_remove(); this is what the driver is doing upon unregistering a network device: 1. state = read bus state 2. if state is not "Closed": 3. request to set state to "Closing" 4. wait for state to be set to "Closing" 5. request to set state to "Closed" 6. wait for state to be set to "Closed" If the state changes to "Closed" immediately after step 1 we are stuck forever in step 4, because the state will never go back from "Closed" to "Closing". Make sure to check also for state == "Closed" in step 4 to prevent the deadlock. Also add a 5 sec timeout any time we wait for the bus state to change, to avoid getting stuck forever in wait_event(). Signed-off-by: Andrea Righi <andrea.righi@canonical.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/xen-netfront.c64
1 files changed, 42 insertions, 22 deletions
diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 482c6c8b0fb7..88280057e032 100644
--- a/drivers/net/xen-netfront.c
+++ b/drivers/net/xen-netfront.c
@@ -63,6 +63,8 @@ module_param_named(max_queues, xennet_max_queues, uint, 0644);
MODULE_PARM_DESC(max_queues,
"Maximum number of queues per virtual interface");
+#define XENNET_TIMEOUT (5 * HZ)
+
static const struct ethtool_ops xennet_ethtool_ops;
struct netfront_cb {
@@ -1334,12 +1336,15 @@ static struct net_device *xennet_create_dev(struct xenbus_device *dev)
netif_carrier_off(netdev);
- xenbus_switch_state(dev, XenbusStateInitialising);
- wait_event(module_wq,
- xenbus_read_driver_state(dev->otherend) !=
- XenbusStateClosed &&
- xenbus_read_driver_state(dev->otherend) !=
- XenbusStateUnknown);
+ do {
+ xenbus_switch_state(dev, XenbusStateInitialising);
+ err = wait_event_timeout(module_wq,
+ xenbus_read_driver_state(dev->otherend) !=
+ XenbusStateClosed &&
+ xenbus_read_driver_state(dev->otherend) !=
+ XenbusStateUnknown, XENNET_TIMEOUT);
+ } while (!err);
+
return netdev;
exit:
@@ -2139,28 +2144,43 @@ static const struct attribute_group xennet_dev_group = {
};
#endif /* CONFIG_SYSFS */
-static int xennet_remove(struct xenbus_device *dev)
+static void xennet_bus_close(struct xenbus_device *dev)
{
- struct netfront_info *info = dev_get_drvdata(&dev->dev);
-
- dev_dbg(&dev->dev, "%s\n", dev->nodename);
+ int ret;
- if (xenbus_read_driver_state(dev->otherend) != XenbusStateClosed) {
+ if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
+ return;
+ do {
xenbus_switch_state(dev, XenbusStateClosing);
- wait_event(module_wq,
- xenbus_read_driver_state(dev->otherend) ==
- XenbusStateClosing ||
- xenbus_read_driver_state(dev->otherend) ==
- XenbusStateUnknown);
+ ret = wait_event_timeout(module_wq,
+ xenbus_read_driver_state(dev->otherend) ==
+ XenbusStateClosing ||
+ xenbus_read_driver_state(dev->otherend) ==
+ XenbusStateClosed ||
+ xenbus_read_driver_state(dev->otherend) ==
+ XenbusStateUnknown,
+ XENNET_TIMEOUT);
+ } while (!ret);
+
+ if (xenbus_read_driver_state(dev->otherend) == XenbusStateClosed)
+ return;
+ do {
xenbus_switch_state(dev, XenbusStateClosed);
- wait_event(module_wq,
- xenbus_read_driver_state(dev->otherend) ==
- XenbusStateClosed ||
- xenbus_read_driver_state(dev->otherend) ==
- XenbusStateUnknown);
- }
+ ret = wait_event_timeout(module_wq,
+ xenbus_read_driver_state(dev->otherend) ==
+ XenbusStateClosed ||
+ xenbus_read_driver_state(dev->otherend) ==
+ XenbusStateUnknown,
+ XENNET_TIMEOUT);
+ } while (!ret);
+}
+
+static int xennet_remove(struct xenbus_device *dev)
+{
+ struct netfront_info *info = dev_get_drvdata(&dev->dev);
+ xennet_bus_close(dev);
xennet_disconnect_backend(info);
if (info->netdev->reg_state == NETREG_REGISTERED)