IPoIB: Fix crash in dev_open error flow

If napi has never been enabled when calling ipoib_ib_dev_stop, a
kernel crash occurs, because the verbs layer completion handler
(ipoib_ib_completion) calls napi_schedule unconditionally.

If the napi structure passed in the napi_schedule call has not
been initialized, napi will crash.

The cleanest solution is to simply enable napi before calling
ipoib_ib_dev_stop in the dev_open error flow. (dev_stop then
immediately disables napi).
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/ulp/ipoib/ipoib_ib.c

@@ -685,15 +685,13 @@ int ipoib_ib_dev_open(struct net_device *dev)
 	ret = ipoib_ib_post_receives(dev);
 	if (ret) {
 		ipoib_warn(priv, "ipoib_ib_post_receives returned %d\n", ret);
-		ipoib_ib_dev_stop(dev, 1);
-		return -1;
+		goto dev_stop;
 	}
 
 	ret = ipoib_cm_dev_open(dev);
 	if (ret) {
 		ipoib_warn(priv, "ipoib_cm_dev_open returned %d\n", ret);
-		ipoib_ib_dev_stop(dev, 1);
-		return -1;
+		goto dev_stop;
 	}
 
 	clear_bit(IPOIB_STOP_REAPER, &priv->flags);
@@ -704,6 +702,11 @@ int ipoib_ib_dev_open(struct net_device *dev)
 		napi_enable(&priv->napi);
 
 	return 0;
+dev_stop:
+	if (!test_and_set_bit(IPOIB_FLAG_INITIALIZED, &priv->flags))
+		napi_enable(&priv->napi);
+	ipoib_ib_dev_stop(dev, 1);
+	return -1;
 }
 
 static void ipoib_pkey_dev_check_presence(struct net_device *dev)