netvsc: use RCU to protect inner device structure

The netvsc driver has an internal structure (netvsc_device) which
is created when device is opened and released when device is closed.
And also opened/released when MTU or number of channels change.

Since this is referenced in the receive and transmit path, it is
safer to use RCU to protect/prevent use after free problems.
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/hyperv/hyperv_net.h

@@ -686,7 +686,7 @@ struct net_device_context {
 	/* point back to our device context */
 	struct hv_device *device_ctx;
 	/* netvsc_device */
-	struct netvsc_device *nvdev;
+	struct netvsc_device __rcu *nvdev;
 	/* reconfigure work */
 	struct delayed_work dwork;
 	/* last reconfig time */
@@ -780,6 +780,8 @@ struct netvsc_device {
 	atomic_t open_cnt;
 
 	struct netvsc_channel chan_table[VRSS_CHANNEL_MAX];
+
+	struct rcu_head rcu;
 };
 
 static inline struct netvsc_device *

drivers/net/hyperv/netvsc.c

@@ -80,8 +80,10 @@ static struct netvsc_device *alloc_net_device(void)
 	return net_device;
 }
 
-static void free_netvsc_device(struct netvsc_device *nvdev)
+static void free_netvsc_device(struct rcu_head *head)
 {
+	struct netvsc_device *nvdev
+		= container_of(head, struct netvsc_device, rcu);
 	int i;
 
 	for (i = 0; i < VRSS_CHANNEL_MAX; i++)
@@ -90,6 +92,10 @@ static void free_netvsc_device(struct netvsc_device *nvdev)
 	kfree(nvdev);
 }
 
+static void free_netvsc_device_rcu(struct netvsc_device *nvdev)
+{
+	call_rcu(&nvdev->rcu, free_netvsc_device);
+}
 
 static struct netvsc_device *get_outbound_net_device(struct hv_device *device)
 {
@@ -551,7 +557,7 @@ void netvsc_device_remove(struct hv_device *device)
 
 	netvsc_disconnect_vsp(device);
 
-	net_device_ctx->nvdev = NULL;
+	RCU_INIT_POINTER(net_device_ctx->nvdev, NULL);
 
 	/*
 	 * At this point, no one should be accessing net_device
@@ -566,7 +572,7 @@ void netvsc_device_remove(struct hv_device *device)
 		napi_disable(&net_device->chan_table[i].napi);
 
 	/* Release all resources */
-	free_netvsc_device(net_device);
+	free_netvsc_device_rcu(net_device);
 }
 
 #define RING_AVAIL_PERCENT_HIWATER 20
@@ -1322,7 +1328,7 @@ int netvsc_device_add(struct hv_device *device,
 	 */
 	wmb();
 
-	net_device_ctx->nvdev = net_device;
+	rcu_assign_pointer(net_device_ctx->nvdev, net_device);
 
 	/* Connect with the NetVsp */
 	ret = netvsc_connect_vsp(device);
@@ -1341,7 +1347,7 @@ int netvsc_device_add(struct hv_device *device,
 	vmbus_close(device->channel);
 
 cleanup:
-	free_netvsc_device(net_device);
+	free_netvsc_device(&net_device->rcu);
 
 	return ret;
 }

drivers/net/hyperv/netvsc_drv.c

@@ -62,7 +62,7 @@ static void do_set_multicast(struct work_struct *w)
 		container_of(w, struct net_device_context, work);
 	struct hv_device *device_obj = ndevctx->device_ctx;
 	struct net_device *ndev = hv_get_drvdata(device_obj);
-	struct netvsc_device *nvdev = ndevctx->nvdev;
+	struct netvsc_device *nvdev = rcu_dereference(ndevctx->nvdev);
 	struct rndis_device *rdev;
 
 	if (!nvdev)
@@ -116,7 +116,7 @@ static int netvsc_open(struct net_device *net)
 static int netvsc_close(struct net_device *net)
 {
 	struct net_device_context *net_device_ctx = netdev_priv(net);
-	struct netvsc_device *nvdev = net_device_ctx->nvdev;
+	struct netvsc_device *nvdev = rtnl_dereference(net_device_ctx->nvdev);
 	int ret;
 	u32 aread, awrite, i, msec = 10, retry = 0, retry_max = 20;
 	struct vmbus_channel *chn;
@@ -637,9 +637,9 @@ int netvsc_recv_callback(struct net_device *net,
 			 const struct ndis_pkt_8021q_info *vlan)
 {
 	struct net_device_context *net_device_ctx = netdev_priv(net);
-	struct netvsc_device *net_device = net_device_ctx->nvdev;
+	struct netvsc_device *net_device;
 	u16 q_idx = channel->offermsg.offer.sub_channel_index;
-	struct netvsc_channel *nvchan = &net_device->chan_table[q_idx];
+	struct netvsc_channel *nvchan;
 	struct net_device *vf_netdev;
 	struct sk_buff *skb;
 	struct netvsc_stats *rx_stats;
@@ -655,6 +655,11 @@ int netvsc_recv_callback(struct net_device *net,
 	 * interface in the guest.
 	 */
 	rcu_read_lock();
+	net_device = rcu_dereference(net_device_ctx->nvdev);
+	if (unlikely(!net_device))
+		goto drop;
+
+	nvchan = &net_device->chan_table[q_idx];
 	vf_netdev = rcu_dereference(net_device_ctx->vf_netdev);
 	if (vf_netdev && (vf_netdev->flags & IFF_UP))
 		net = vf_netdev;
@@ -663,6 +668,7 @@ int netvsc_recv_callback(struct net_device *net,
 	skb = netvsc_alloc_recv_skb(net, &nvchan->napi,
 				    csum_info, vlan, data, len);
 	if (unlikely(!skb)) {
+drop:
 		++net->stats.rx_dropped;
 		rcu_read_unlock();
 		return NVSP_STAT_FAIL;
@@ -704,7 +710,7 @@ static void netvsc_get_channels(struct net_device *net,
 				struct ethtool_channels *channel)
 {
 	struct net_device_context *net_device_ctx = netdev_priv(net);
-	struct netvsc_device *nvdev = net_device_ctx->nvdev;
+	struct netvsc_device *nvdev = rtnl_dereference(net_device_ctx->nvdev);
 
 	if (nvdev) {
 		channel->max_combined	= nvdev->max_chn;
@@ -741,7 +747,7 @@ static int netvsc_set_channels(struct net_device *net,
 {
 	struct net_device_context *net_device_ctx = netdev_priv(net);
 	struct hv_device *dev = net_device_ctx->device_ctx;
-	struct netvsc_device *nvdev = net_device_ctx->nvdev;
+	struct netvsc_device *nvdev = rtnl_dereference(net_device_ctx->nvdev);
 	unsigned int count = channels->combined_count;
 	bool was_running;
 	int ret;
@@ -848,7 +854,7 @@ static int netvsc_set_link_ksettings(struct net_device *dev,
 static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 {
 	struct net_device_context *ndevctx = netdev_priv(ndev);
-	struct netvsc_device *nvdev = ndevctx->nvdev;
+	struct netvsc_device *nvdev = rtnl_dereference(ndevctx->nvdev);
 	struct hv_device *hdev = ndevctx->device_ctx;
 	struct netvsc_device_info device_info;
 	bool was_running;
@@ -897,7 +903,7 @@ static void netvsc_get_stats64(struct net_device *net,
 			       struct rtnl_link_stats64 *t)
 {
 	struct net_device_context *ndev_ctx = netdev_priv(net);
-	struct netvsc_device *nvdev = ndev_ctx->nvdev;
+	struct netvsc_device *nvdev = rcu_dereference(ndev_ctx->nvdev);
 	int i;
 
 	if (!nvdev)
@@ -982,7 +988,10 @@ static const struct {
 static int netvsc_get_sset_count(struct net_device *dev, int string_set)
 {
 	struct net_device_context *ndc = netdev_priv(dev);
-	struct netvsc_device *nvdev = ndc->nvdev;
+	struct netvsc_device *nvdev = rcu_dereference(ndc->nvdev);
+
+	if (!nvdev)
+		return -ENODEV;
 
 	switch (string_set) {
 	case ETH_SS_STATS:
@@ -996,13 +1005,16 @@ static void netvsc_get_ethtool_stats(struct net_device *dev,
 				     struct ethtool_stats *stats, u64 *data)
 {
 	struct net_device_context *ndc = netdev_priv(dev);
-	struct netvsc_device *nvdev = ndc->nvdev;
+	struct netvsc_device *nvdev = rcu_dereference(ndc->nvdev);
 	const void *nds = &ndc->eth_stats;
 	const struct netvsc_stats *qstats;
 	unsigned int start;
 	u64 packets, bytes;
 	int i, j;
 
+	if (!nvdev)
+		return;
+
 	for (i = 0; i < NETVSC_GLOBAL_STATS_LEN; i++)
 		data[i] = *(unsigned long *)(nds + netvsc_stats[i].offset);
 
@@ -1031,10 +1043,13 @@ static void netvsc_get_ethtool_stats(struct net_device *dev,
 static void netvsc_get_strings(struct net_device *dev, u32 stringset, u8 *data)
 {
 	struct net_device_context *ndc = netdev_priv(dev);
-	struct netvsc_device *nvdev = ndc->nvdev;
+	struct netvsc_device *nvdev = rcu_dereference(ndc->nvdev);
 	u8 *p = data;
 	int i;
 
+	if (!nvdev)
+		return;
+
 	switch (stringset) {
 	case ETH_SS_STATS:
 		for (i = 0; i < ARRAY_SIZE(netvsc_stats); i++)
@@ -1086,7 +1101,10 @@ netvsc_get_rxnfc(struct net_device *dev, struct ethtool_rxnfc *info,
 		 u32 *rules)
 {
 	struct net_device_context *ndc = netdev_priv(dev);
-	struct netvsc_device *nvdev = ndc->nvdev;
+	struct netvsc_device *nvdev = rcu_dereference(ndc->nvdev);
+
+	if (!nvdev)
+		return -ENODEV;
 
 	switch (info->cmd) {
 	case ETHTOOL_GRXRINGS:
@@ -1122,10 +1140,13 @@ static int netvsc_get_rxfh(struct net_device *dev, u32 *indir, u8 *key,
 			   u8 *hfunc)
 {
 	struct net_device_context *ndc = netdev_priv(dev);
-	struct netvsc_device *ndev = ndc->nvdev;
+	struct netvsc_device *ndev = rcu_dereference(ndc->nvdev);
 	struct rndis_device *rndis_dev = ndev->extension;
 	int i;
 
+	if (!ndev)
+		return -ENODEV;
+
 	if (hfunc)
 		*hfunc = ETH_RSS_HASH_TOP;	/* Toeplitz */
 
@@ -1144,10 +1165,13 @@ static int netvsc_set_rxfh(struct net_device *dev, const u32 *indir,
 			   const u8 *key, const u8 hfunc)
 {
 	struct net_device_context *ndc = netdev_priv(dev);
-	struct netvsc_device *ndev = ndc->nvdev;
+	struct netvsc_device *ndev = rtnl_dereference(ndc->nvdev);
 	struct rndis_device *rndis_dev = ndev->extension;
 	int i;
 
+	if (!ndev)
+		return -ENODEV;
+
 	if (hfunc != ETH_RSS_HASH_NO_CHANGE && hfunc != ETH_RSS_HASH_TOP)
 		return -EOPNOTSUPP;
 
@@ -1224,7 +1248,7 @@ static void netvsc_link_change(struct work_struct *w)
 	if (ndev_ctx->start_remove)
 		goto out_unlock;
 
-	net_device = ndev_ctx->nvdev;
+	net_device = rtnl_dereference(ndev_ctx->nvdev);
 	rdev = net_device->extension;
 
 	next_reconfig = ndev_ctx->last_reconfig + LINKCHANGE_INT;
@@ -1365,7 +1389,7 @@ static int netvsc_register_vf(struct net_device *vf_netdev)
 		return NOTIFY_DONE;
 
 	net_device_ctx = netdev_priv(ndev);
-	netvsc_dev = net_device_ctx->nvdev;
+	netvsc_dev = rtnl_dereference(net_device_ctx->nvdev);
 	if (!netvsc_dev || rtnl_dereference(net_device_ctx->vf_netdev))
 		return NOTIFY_DONE;
 
@@ -1391,7 +1415,7 @@ static int netvsc_vf_up(struct net_device *vf_netdev)
 		return NOTIFY_DONE;
 
 	net_device_ctx = netdev_priv(ndev);
-	netvsc_dev = net_device_ctx->nvdev;
+	netvsc_dev = rtnl_dereference(net_device_ctx->nvdev);
 
 	netdev_info(ndev, "VF up: %s\n", vf_netdev->name);
 
@@ -1425,7 +1449,7 @@ static int netvsc_vf_down(struct net_device *vf_netdev)
 		return NOTIFY_DONE;
 
 	net_device_ctx = netdev_priv(ndev);
-	netvsc_dev = net_device_ctx->nvdev;
+	netvsc_dev = rtnl_dereference(net_device_ctx->nvdev);
 
 	netdev_info(ndev, "VF down: %s\n", vf_netdev->name);
 	netvsc_switch_datapath(ndev, false);
@@ -1519,6 +1543,7 @@ 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);