Merge branch 'rtnetlink-more-rcu-conversions-for-rtnl_fill_ifinfo'

Eric Dumazet says:

====================
rtnetlink: more rcu conversions for rtnl_fill_ifinfo()

We want to no longer rely on RTNL for "ip link show" command.

This is a long road, this series takes care of some parts.
====================

Link: https://lore.kernel.org/r/20240503192059.3884225-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ppp/ppp_generic.c

@@ -1357,7 +1357,7 @@ static struct net *ppp_nl_get_link_net(const struct net_device *dev)
 {
 	struct ppp *ppp = netdev_priv(dev);
 
-	return ppp->ppp_net;
+	return READ_ONCE(ppp->ppp_net);
 }
 
 static struct rtnl_link_ops ppp_link_ops __read_mostly = {

drivers/net/vxlan/vxlan_core.c

@@ -4569,7 +4569,7 @@ static struct net *vxlan_get_link_net(const struct net_device *dev)
 {
 	struct vxlan_dev *vxlan = netdev_priv(dev);
 
-	return vxlan->net;
+	return READ_ONCE(vxlan->net);
 }
 
 static struct rtnl_link_ops vxlan_link_ops __read_mostly = {

net/core/dev.c

@@ -8544,27 +8544,29 @@ static void dev_change_rx_flags(struct net_device *dev, int flags)
 static int __dev_set_promiscuity(struct net_device *dev, int inc, bool notify)
 {
 	unsigned int old_flags = dev->flags;
+	unsigned int promiscuity, flags;
 	kuid_t uid;
 	kgid_t gid;
 
 	ASSERT_RTNL();
 
-	dev->flags |= IFF_PROMISC;
-	dev->promiscuity += inc;
-	if (dev->promiscuity == 0) {
+	promiscuity = dev->promiscuity + inc;
+	if (promiscuity == 0) {
 		/*
 		 * Avoid overflow.
 		 * If inc causes overflow, untouch promisc and return error.
 		 */
-		if (inc < 0)
-			dev->flags &= ~IFF_PROMISC;
-		else {
-			dev->promiscuity -= inc;
+		if (unlikely(inc > 0)) {
 			netdev_warn(dev, "promiscuity touches roof, set promiscuity failed. promiscuity feature of device might be broken.\n");
 			return -EOVERFLOW;
 		}
+		flags = old_flags & ~IFF_PROMISC;
+	} else {
+		flags = old_flags | IFF_PROMISC;
 	}
-	if (dev->flags != old_flags) {
+	WRITE_ONCE(dev->promiscuity, promiscuity);
+	if (flags != old_flags) {
+		WRITE_ONCE(dev->flags, flags);
 		netdev_info(dev, "%s promiscuous mode\n",
 			    dev->flags & IFF_PROMISC ? "entered" : "left");
 		if (audit_enabled) {
@@ -8615,25 +8617,27 @@ EXPORT_SYMBOL(dev_set_promiscuity);
 static int __dev_set_allmulti(struct net_device *dev, int inc, bool notify)
 {
 	unsigned int old_flags = dev->flags, old_gflags = dev->gflags;
+	unsigned int allmulti, flags;
 
 	ASSERT_RTNL();
 
-	dev->flags |= IFF_ALLMULTI;
-	dev->allmulti += inc;
-	if (dev->allmulti == 0) {
+	allmulti = dev->allmulti + inc;
+	if (allmulti == 0) {
 		/*
 		 * Avoid overflow.
 		 * If inc causes overflow, untouch allmulti and return error.
 		 */
-		if (inc < 0)
-			dev->flags &= ~IFF_ALLMULTI;
-		else {
-			dev->allmulti -= inc;
+		if (unlikely(inc > 0)) {
 			netdev_warn(dev, "allmulti touches roof, set allmulti failed. allmulti feature of device might be broken.\n");
 			return -EOVERFLOW;
 		}
+		flags = old_flags & ~IFF_ALLMULTI;
+	} else {
+		flags = old_flags | IFF_ALLMULTI;
 	}
-	if (dev->flags ^ old_flags) {
+	WRITE_ONCE(dev->allmulti, allmulti);
+	if (flags != old_flags) {
+		WRITE_ONCE(dev->flags, flags);
 		netdev_info(dev, "%s allmulticast mode\n",
 			    dev->flags & IFF_ALLMULTI ? "entered" : "left");
 		dev_change_rx_flags(dev, IFF_ALLMULTI);
@@ -8959,7 +8963,7 @@ int dev_change_tx_queue_len(struct net_device *dev, unsigned long new_len)
 		return -ERANGE;
 
 	if (new_len != orig_len) {
-		dev->tx_queue_len = new_len;
+		WRITE_ONCE(dev->tx_queue_len, new_len);
 		res = call_netdevice_notifiers(NETDEV_CHANGE_TX_QUEUE_LEN, dev);
 		res = notifier_to_errno(res);
 		if (res)
@@ -8973,7 +8977,7 @@ int dev_change_tx_queue_len(struct net_device *dev, unsigned long new_len)
 
 err_rollback:
 	netdev_err(dev, "refused to change device tx_queue_len\n");
-	dev->tx_queue_len = orig_len;
+	WRITE_ONCE(dev->tx_queue_len, orig_len);
 	return res;
 }
 
@@ -9219,7 +9223,7 @@ int dev_change_proto_down(struct net_device *dev, bool proto_down)
 		netif_carrier_off(dev);
 	else
 		netif_carrier_on(dev);
-	dev->proto_down = proto_down;
+	WRITE_ONCE(dev->proto_down, proto_down);
 	return 0;
 }
 
@@ -9233,18 +9237,21 @@ int dev_change_proto_down(struct net_device *dev, bool proto_down)
 void dev_change_proto_down_reason(struct net_device *dev, unsigned long mask,
 				  u32 value)
 {
+	u32 proto_down_reason;
 	int b;
 
 	if (!mask) {
-		dev->proto_down_reason = value;
+		proto_down_reason = value;
 	} else {
+		proto_down_reason = dev->proto_down_reason;
 		for_each_set_bit(b, &mask, 32) {
 			if (value & (1 << b))
-				dev->proto_down_reason |= BIT(b);
+				proto_down_reason |= BIT(b);
 			else
-				dev->proto_down_reason &= ~BIT(b);
+				proto_down_reason &= ~BIT(b);
 		}
 	}
+	WRITE_ONCE(dev->proto_down_reason, proto_down_reason);
 }
 
 struct bpf_xdp_link {

net/core/rtnetlink.c

@@ -1036,8 +1036,8 @@ static size_t rtnl_proto_down_size(const struct net_device *dev)
 {
 	size_t size = nla_total_size(1);
 
-	if (dev->proto_down_reason)
-		size += nla_total_size(0) + nla_total_size(4);
+	/* Assume dev->proto_down_reason is not zero. */
+	size += nla_total_size(0) + nla_total_size(4);
 
 	return size;
 }
@@ -1477,13 +1477,15 @@ static int rtnl_fill_link_ifmap(struct sk_buff *skb,
 static u32 rtnl_xdp_prog_skb(struct net_device *dev)
 {
 	const struct bpf_prog *generic_xdp_prog;
+	u32 res = 0;
 
-	ASSERT_RTNL();
+	rcu_read_lock();
+	generic_xdp_prog = rcu_dereference(dev->xdp_prog);
+	if (generic_xdp_prog)
+		res = generic_xdp_prog->aux->id;
+	rcu_read_unlock();
 
-	generic_xdp_prog = rtnl_dereference(dev->xdp_prog);
-	if (!generic_xdp_prog)
-		return 0;
-	return generic_xdp_prog->aux->id;
+	return res;
 }
 
 static u32 rtnl_xdp_prog_drv(struct net_device *dev)
@@ -1603,7 +1605,8 @@ static int put_master_ifindex(struct sk_buff *skb, struct net_device *dev)
 
 	upper_dev = netdev_master_upper_dev_get_rcu(dev);
 	if (upper_dev)
-		ret = nla_put_u32(skb, IFLA_MASTER, upper_dev->ifindex);
+		ret = nla_put_u32(skb, IFLA_MASTER,
+				  READ_ONCE(upper_dev->ifindex));
 
 	rcu_read_unlock();
 	return ret;
@@ -1736,10 +1739,10 @@ static int rtnl_fill_proto_down(struct sk_buff *skb,
 	struct nlattr *pr;
 	u32 preason;
 
-	if (nla_put_u8(skb, IFLA_PROTO_DOWN, dev->proto_down))
+	if (nla_put_u8(skb, IFLA_PROTO_DOWN, READ_ONCE(dev->proto_down)))
 		goto nla_put_failure;
 
-	preason = dev->proto_down_reason;
+	preason = READ_ONCE(dev->proto_down_reason);
 	if (!preason)
 		return 0;
 
@@ -1812,6 +1815,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 			    u32 event, int *new_nsid, int new_ifindex,
 			    int tgt_netnsid, gfp_t gfp)
 {
+	char devname[IFNAMSIZ];
 	struct ifinfomsg *ifm;
 	struct nlmsghdr *nlh;
 	struct Qdisc *qdisc;
@@ -1824,41 +1828,51 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 	ifm = nlmsg_data(nlh);
 	ifm->ifi_family = AF_UNSPEC;
 	ifm->__ifi_pad = 0;
-	ifm->ifi_type = dev->type;
-	ifm->ifi_index = dev->ifindex;
+	ifm->ifi_type = READ_ONCE(dev->type);
+	ifm->ifi_index = READ_ONCE(dev->ifindex);
 	ifm->ifi_flags = dev_get_flags(dev);
 	ifm->ifi_change = change;
 
 	if (tgt_netnsid >= 0 && nla_put_s32(skb, IFLA_TARGET_NETNSID, tgt_netnsid))
 		goto nla_put_failure;
 
-	qdisc = rtnl_dereference(dev->qdisc);
-	if (nla_put_string(skb, IFLA_IFNAME, dev->name) ||
-	    nla_put_u32(skb, IFLA_TXQLEN, dev->tx_queue_len) ||
+	netdev_copy_name(dev, devname);
+	if (nla_put_string(skb, IFLA_IFNAME, devname))
+		goto nla_put_failure;
+
+	if (nla_put_u32(skb, IFLA_TXQLEN, READ_ONCE(dev->tx_queue_len)) ||
 	    nla_put_u8(skb, IFLA_OPERSTATE,
-		       netif_running(dev) ? dev->operstate : IF_OPER_DOWN) ||
-	    nla_put_u8(skb, IFLA_LINKMODE, dev->link_mode) ||
-	    nla_put_u32(skb, IFLA_MTU, dev->mtu) ||
-	    nla_put_u32(skb, IFLA_MIN_MTU, dev->min_mtu) ||
-	    nla_put_u32(skb, IFLA_MAX_MTU, dev->max_mtu) ||
-	    nla_put_u32(skb, IFLA_GROUP, dev->group) ||
-	    nla_put_u32(skb, IFLA_PROMISCUITY, dev->promiscuity) ||
-	    nla_put_u32(skb, IFLA_ALLMULTI, dev->allmulti) ||
-	    nla_put_u32(skb, IFLA_NUM_TX_QUEUES, dev->num_tx_queues) ||
-	    nla_put_u32(skb, IFLA_GSO_MAX_SEGS, dev->gso_max_segs) ||
-	    nla_put_u32(skb, IFLA_GSO_MAX_SIZE, dev->gso_max_size) ||
-	    nla_put_u32(skb, IFLA_GRO_MAX_SIZE, dev->gro_max_size) ||
-	    nla_put_u32(skb, IFLA_GSO_IPV4_MAX_SIZE, dev->gso_ipv4_max_size) ||
-	    nla_put_u32(skb, IFLA_GRO_IPV4_MAX_SIZE, dev->gro_ipv4_max_size) ||
-	    nla_put_u32(skb, IFLA_TSO_MAX_SIZE, dev->tso_max_size) ||
-	    nla_put_u32(skb, IFLA_TSO_MAX_SEGS, dev->tso_max_segs) ||
+		       netif_running(dev) ? READ_ONCE(dev->operstate) :
+					    IF_OPER_DOWN) ||
+	    nla_put_u8(skb, IFLA_LINKMODE, READ_ONCE(dev->link_mode)) ||
+	    nla_put_u32(skb, IFLA_MTU, READ_ONCE(dev->mtu)) ||
+	    nla_put_u32(skb, IFLA_MIN_MTU, READ_ONCE(dev->min_mtu)) ||
+	    nla_put_u32(skb, IFLA_MAX_MTU, READ_ONCE(dev->max_mtu)) ||
+	    nla_put_u32(skb, IFLA_GROUP, READ_ONCE(dev->group)) ||
+	    nla_put_u32(skb, IFLA_PROMISCUITY, READ_ONCE(dev->promiscuity)) ||
+	    nla_put_u32(skb, IFLA_ALLMULTI, READ_ONCE(dev->allmulti)) ||
+	    nla_put_u32(skb, IFLA_NUM_TX_QUEUES,
+			READ_ONCE(dev->num_tx_queues)) ||
+	    nla_put_u32(skb, IFLA_GSO_MAX_SEGS,
+			READ_ONCE(dev->gso_max_segs)) ||
+	    nla_put_u32(skb, IFLA_GSO_MAX_SIZE,
+			READ_ONCE(dev->gso_max_size)) ||
+	    nla_put_u32(skb, IFLA_GRO_MAX_SIZE,
+			READ_ONCE(dev->gro_max_size)) ||
+	    nla_put_u32(skb, IFLA_GSO_IPV4_MAX_SIZE,
+			READ_ONCE(dev->gso_ipv4_max_size)) ||
+	    nla_put_u32(skb, IFLA_GRO_IPV4_MAX_SIZE,
+			READ_ONCE(dev->gro_ipv4_max_size)) ||
+	    nla_put_u32(skb, IFLA_TSO_MAX_SIZE,
+			READ_ONCE(dev->tso_max_size)) ||
+	    nla_put_u32(skb, IFLA_TSO_MAX_SEGS,
+			READ_ONCE(dev->tso_max_segs)) ||
 #ifdef CONFIG_RPS
-	    nla_put_u32(skb, IFLA_NUM_RX_QUEUES, dev->num_rx_queues) ||
+	    nla_put_u32(skb, IFLA_NUM_RX_QUEUES,
+			READ_ONCE(dev->num_rx_queues)) ||
 #endif
 	    put_master_ifindex(skb, dev) ||
 	    nla_put_u8(skb, IFLA_CARRIER, netif_carrier_ok(dev)) ||
-	    (qdisc &&
-	     nla_put_string(skb, IFLA_QDISC, qdisc->ops->id)) ||
 	    nla_put_ifalias(skb, dev) ||
 	    nla_put_u32(skb, IFLA_CARRIER_CHANGES,
 			atomic_read(&dev->carrier_up_count) +
@@ -1909,9 +1923,6 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 			goto nla_put_failure;
 	}
 
-	if (rtnl_fill_link_netnsid(skb, dev, src_net, gfp))
-		goto nla_put_failure;
-
 	if (new_nsid &&
 	    nla_put_s32(skb, IFLA_NEW_NETNSID, *new_nsid) < 0)
 		goto nla_put_failure;
@@ -1924,6 +1935,11 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 		goto nla_put_failure;
 
 	rcu_read_lock();
+	if (rtnl_fill_link_netnsid(skb, dev, src_net, GFP_ATOMIC))
+		goto nla_put_failure_rcu;
+	qdisc = rcu_dereference(dev->qdisc);
+	if (qdisc && nla_put_string(skb, IFLA_QDISC, qdisc->ops->id))
+		goto nla_put_failure_rcu;
 	if (rtnl_fill_link_af(skb, dev, ext_filter_mask))
 		goto nla_put_failure_rcu;
 	if (rtnl_fill_link_ifmap(skb, dev))

net/ipv4/ip_tunnel.c

@@ -1120,7 +1120,7 @@ struct net *ip_tunnel_get_link_net(const struct net_device *dev)
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
 
-	return tunnel->net;
+	return READ_ONCE(tunnel->net);
 }
 EXPORT_SYMBOL(ip_tunnel_get_link_net);
 

net/ipv6/ip6_tunnel.c

@@ -2146,7 +2146,7 @@ struct net *ip6_tnl_get_link_net(const struct net_device *dev)
 {
 	struct ip6_tnl *tunnel = netdev_priv(dev);
 
-	return tunnel->net;
+	return READ_ONCE(tunnel->net);
 }
 EXPORT_SYMBOL(ip6_tnl_get_link_net);
 

net/sched/sch_api.c

@@ -1334,7 +1334,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 	 * before again attaching a qdisc.
 	 */
 	if ((dev->priv_flags & IFF_NO_QUEUE) && (dev->tx_queue_len == 0)) {
-		dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
+		WRITE_ONCE(dev->tx_queue_len, DEFAULT_TX_QUEUE_LEN);
 		netdev_info(dev, "Caught tx_queue_len zero misconfig\n");
 	}
 

net/sched/sch_teql.c

@@ -78,7 +78,7 @@ teql_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 	struct net_device *dev = qdisc_dev(sch);
 	struct teql_sched_data *q = qdisc_priv(sch);
 
-	if (q->q.qlen < dev->tx_queue_len) {
+	if (q->q.qlen < READ_ONCE(dev->tx_queue_len)) {
 		__skb_queue_tail(&q->q, skb);
 		return NET_XMIT_SUCCESS;
 	}

net/xfrm/xfrm_interface_core.c

@@ -926,7 +926,7 @@ static struct net *xfrmi_get_link_net(const struct net_device *dev)
 {
 	struct xfrm_if *xi = netdev_priv(dev);
 
-	return xi->net;
+	return READ_ONCE(xi->net);
 }
 
 static const struct nla_policy xfrmi_policy[IFLA_XFRM_MAX + 1] = {