netvsc: use ERR_PTR to avoid dereference issues

The rndis_filter_device_add function is called both in
probe context and RTNL context,and creates the netvsc_device
inner structure. It is easier to get the RTNL lock annotation
correct if it returns the object directly, rather than implicitly
by updating network device private data.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/hyperv_net.h

@@ -183,7 +183,7 @@ struct rndis_device {
 /* Interface */
 struct rndis_message;
 struct netvsc_device;
-int netvsc_device_add(struct hv_device *device,
+struct netvsc_device *netvsc_device_add(struct hv_device *device,
 					const struct netvsc_device_info *info);
 void netvsc_device_remove(struct hv_device *device);
 int netvsc_send(struct hv_device *device,
@@ -203,7 +203,7 @@ int netvsc_poll(struct napi_struct *napi, int budget);
 bool rndis_filter_opened(const struct netvsc_device *nvdev);
 int rndis_filter_open(struct netvsc_device *nvdev);
 int rndis_filter_close(struct netvsc_device *nvdev);
-int rndis_filter_device_add(struct hv_device *dev,
+struct netvsc_device *rndis_filter_device_add(struct hv_device *dev,
 					      struct netvsc_device_info *info);
 void rndis_filter_update(struct netvsc_device *nvdev);
 void rndis_filter_device_remove(struct hv_device *dev,

drivers/net/hyperv/netvsc.c

@@ -29,6 +29,8 @@
 #include <linux/netdevice.h>
 #include <linux/if_ether.h>
 #include <linux/vmalloc.h>
+#include <linux/rtnetlink.h>
+
 #include <asm/sync_bitops.h>
 
 #include "hyperv_net.h"
@@ -1272,7 +1274,7 @@ void netvsc_channel_cb(void *context)
  * netvsc_device_add - Callback when the device belonging to this
  * driver is added
  */
-int netvsc_device_add(struct hv_device *device,
+struct netvsc_device *netvsc_device_add(struct hv_device *device,
 				const struct netvsc_device_info *device_info)
 {
 	int i, ret = 0;
@@ -1283,7 +1285,7 @@ int netvsc_device_add(struct hv_device *device,
 
 	net_device = alloc_net_device();
 	if (!net_device)
-		return -ENOMEM;
+		return ERR_PTR(-ENOMEM);
 
 	net_device->ring_size = ring_size;
 
@@ -1339,7 +1341,7 @@ int netvsc_device_add(struct hv_device *device,
 		goto close;
 	}
 
-	return ret;
+	return net_device;
 
 close:
 	netif_napi_del(&net_device->chan_table[0].napi);
@@ -1350,6 +1352,5 @@ int netvsc_device_add(struct hv_device *device,
 cleanup:
 	free_netvsc_device(&net_device->rcu);
 
-	return ret;
-
+	return ERR_PTR(ret);
 }

drivers/net/hyperv/netvsc_drv.c

@@ -717,6 +717,7 @@ static int netvsc_set_queues(struct net_device *net, struct hv_device *dev,
 			     u32 num_chn)
 {
 	struct netvsc_device_info device_info;
+	struct netvsc_device *net_device;
 	int ret;
 
 	memset(&device_info, 0, sizeof(device_info));
@@ -732,7 +733,8 @@ static int netvsc_set_queues(struct net_device *net, struct hv_device *dev,
 	if (ret)
 		return ret;
 
-	return rndis_filter_device_add(dev, &device_info);
+	net_device = rndis_filter_device_add(dev, &device_info);
+	return IS_ERR(net_device) ? PTR_ERR(net_device) : 0;
 }
 
 static int netvsc_set_channels(struct net_device *net,
@@ -845,8 +847,10 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 	struct net_device_context *ndevctx = netdev_priv(ndev);
 	struct netvsc_device *nvdev = rtnl_dereference(ndevctx->nvdev);
 	struct hv_device *hdev = ndevctx->device_ctx;
+	int orig_mtu = ndev->mtu;
 	struct netvsc_device_info device_info;
 	bool was_opened;
+	int ret = 0;
 
 	if (!nvdev || nvdev->destroy)
 		return -ENODEV;
@@ -863,16 +867,16 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 
 	rndis_filter_device_remove(hdev, nvdev);
 
-	/* 'nvdev' has been freed in rndis_filter_device_remove() ->
-	 * netvsc_device_remove () -> free_netvsc_device().
-	 * We mustn't access it before it's re-created in
-	 * rndis_filter_device_add() -> netvsc_device_add().
-	 */
-
 	ndev->mtu = mtu;
 
+	nvdev = rndis_filter_device_add(hdev, &device_info);
+	if (IS_ERR(nvdev)) {
+		ret = PTR_ERR(nvdev);
+
+		/* Attempt rollback to original MTU */
+		ndev->mtu = orig_mtu;
 		rndis_filter_device_add(hdev, &device_info);
-	nvdev = rtnl_dereference(ndevctx->nvdev);
+	}
 
 	if (was_opened)
 		rndis_filter_open(nvdev);
@@ -882,7 +886,7 @@ static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 	/* We may have missed link change notifications */
 	schedule_delayed_work(&ndevctx->dwork, 0);
 
-	return 0;
+	return ret;
 }
 
 static void netvsc_get_stats64(struct net_device *net,
@@ -1525,8 +1529,10 @@ static int netvsc_probe(struct hv_device *dev,
 	memset(&device_info, 0, sizeof(device_info));
 	device_info.ring_size = ring_size;
 	device_info.num_chn = VRSS_CHANNEL_DEFAULT;
-	ret = rndis_filter_device_add(dev, &device_info);
-	if (ret != 0) {
+
+	nvdev = rndis_filter_device_add(dev, &device_info);
+	if (IS_ERR(nvdev)) {
+		ret = PTR_ERR(nvdev);
 		netdev_err(net, "unable to add netvsc device (ret %d)\n", ret);
 		free_netdev(net);
 		hv_set_drvdata(dev, NULL);
@@ -1540,11 +1546,11 @@ static int netvsc_probe(struct hv_device *dev,
 		NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_CTAG_RX;
 	net->vlan_features = net->features;
 
-	/* RCU not necessary here, device not registered */
-	nvdev = net_device_ctx->nvdev;
 	netif_set_real_num_tx_queues(net, nvdev->num_chn);
 	netif_set_real_num_rx_queues(net, nvdev->num_chn);
 
+	netdev_lockdep_set_classes(net);
+
 	/* MTU range: 68 - 1500 or 65521 */
 	net->min_mtu = NETVSC_MTU_MIN;
 	if (nvdev->nvsp_version >= NVSP_PROTOCOL_VERSION_2)

drivers/net/hyperv/rndis_filter.c

@@ -658,9 +658,9 @@ int rndis_filter_set_device_mac(struct net_device *ndev, char *mac)
 
 static int
 rndis_filter_set_offload_params(struct net_device *ndev,
+				struct netvsc_device *nvdev,
 				struct ndis_offload_params *req_offloads)
 {
-	struct netvsc_device *nvdev = net_device_to_netvsc_device(ndev);
 	struct rndis_device *rdev = nvdev->extension;
 	struct rndis_request *request;
 	struct rndis_set_request *set;
@@ -1052,7 +1052,7 @@ static void netvsc_sc_open(struct vmbus_channel *new_sc)
 		complete(&nvscdev->channel_init_wait);
 }
 
-int rndis_filter_device_add(struct hv_device *dev,
+struct netvsc_device *rndis_filter_device_add(struct hv_device *dev,
 				      struct netvsc_device_info *device_info)
 {
 	struct net_device *net = hv_get_drvdata(dev);
@@ -1072,21 +1072,20 @@ int rndis_filter_device_add(struct hv_device *dev,
 
 	rndis_device = get_rndis_device();
 	if (!rndis_device)
-		return -ENODEV;
+		return ERR_PTR(-ENODEV);
 
 	/*
 	 * Let the inner driver handle this first to create the netvsc channel
 	 * NOTE! Once the channel is created, we may get a receive callback
 	 * (RndisFilterOnReceive()) before this call is completed
 	 */
-	ret = netvsc_device_add(dev, device_info);
-	if (ret != 0) {
+	net_device = netvsc_device_add(dev, device_info);
+	if (IS_ERR(net_device)) {
 		kfree(rndis_device);
-		return ret;
+		return net_device;
 	}
 
 	/* Initialize the rndis device */
-	net_device = net_device_ctx->nvdev;
 	net_device->max_chn = 1;
 	net_device->num_chn = 1;
 
@@ -1097,10 +1096,8 @@ int rndis_filter_device_add(struct hv_device *dev,
 
 	/* Send the rndis initialization message */
 	ret = rndis_filter_init_device(rndis_device);
-	if (ret != 0) {
-		rndis_filter_device_remove(dev, net_device);
-		return ret;
-	}
+	if (ret != 0)
+		goto err_dev_remv;
 
 	/* Get the MTU from the host */
 	size = sizeof(u32);
@@ -1112,19 +1109,15 @@ int rndis_filter_device_add(struct hv_device *dev,
 
 	/* Get the mac address */
 	ret = rndis_filter_query_device_mac(rndis_device);
-	if (ret != 0) {
-		rndis_filter_device_remove(dev, net_device);
-		return ret;
-	}
+	if (ret != 0)
+		goto err_dev_remv;
 
 	memcpy(device_info->mac_adr, rndis_device->hw_mac_adr, ETH_ALEN);
 
 	/* Find HW offload capabilities */
 	ret = rndis_query_hwcaps(rndis_device, &hwcaps);
-	if (ret != 0) {
-		rndis_filter_device_remove(dev, net_device);
-		return ret;
-	}
+	if (ret != 0)
+		goto err_dev_remv;
 
 	/* A value of zero means "no change"; now turn on what we want. */
 	memset(&offloads, 0, sizeof(struct ndis_offload_params));
@@ -1179,7 +1172,7 @@ int rndis_filter_device_add(struct hv_device *dev,
 
 	netif_set_gso_max_size(net, gso_max_size);
 
-	ret = rndis_filter_set_offload_params(net, &offloads);
+	ret = rndis_filter_set_offload_params(net, net_device, &offloads);
 	if (ret)
 		goto err_dev_remv;
 
@@ -1190,7 +1183,7 @@ int rndis_filter_device_add(struct hv_device *dev,
 		   rndis_device->link_state ? "down" : "up");
 
 	if (net_device->nvsp_version < NVSP_PROTOCOL_VERSION_5)
-		return 0;
+		return net_device;
 
 	rndis_filter_query_link_speed(rndis_device);
 
@@ -1223,7 +1216,7 @@ int rndis_filter_device_add(struct hv_device *dev,
 
 	num_rss_qs = net_device->num_chn - 1;
 	if (num_rss_qs == 0)
-		return 0;
+		return net_device;
 
 	refcount_set(&net_device->sc_offered, num_rss_qs);
 	vmbus_set_sc_create_callback(dev->channel, netvsc_sc_open);
@@ -1260,11 +1253,11 @@ int rndis_filter_device_add(struct hv_device *dev,
 		net_device->num_chn = 1;
 	}
 
-	return 0; /* return 0 because primary channel can be used alone */
+	return net_device;
 
 err_dev_remv:
 	rndis_filter_device_remove(dev, net_device);
-	return ret;
+	return ERR_PTR(ret);
 }
 
 void rndis_filter_device_remove(struct hv_device *dev,