ipv6: annotate data-races around cnf.forwarding

idev->cnf.forwarding and net->ipv6.devconf_all->forwarding
might be read locklessly, add appropriate READ_ONCE()
and WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Author: edumazet

drivers/net/usb/cdc_mbim.c

@@ -339,7 +339,7 @@ static void do_neigh_solicit(struct usbnet *dev, u8 *buf, u16 tci)
 	in6_dev = in6_dev_get(netdev);
 	if (!in6_dev)
 		goto out;
-	is_router = !!in6_dev->cnf.forwarding;
+	is_router = !!READ_ONCE(in6_dev->cnf.forwarding);
 	in6_dev_put(in6_dev);
 
 	/* ipv6_stub != NULL if in6_dev_get returned an inet6_dev */

include/net/ipv6.h

@@ -534,13 +534,15 @@ static inline int ipv6_hopopt_jumbo_remove(struct sk_buff *skb)
 	return 0;
 }
 
-static inline bool ipv6_accept_ra(struct inet6_dev *idev)
+static inline bool ipv6_accept_ra(const struct inet6_dev *idev)
 {
+	s32 accept_ra = READ_ONCE(idev->cnf.accept_ra);
+
 	/* If forwarding is enabled, RA are not accepted unless the special
 	 * hybrid mode (accept_ra=2) is enabled.
 	 */
-	return idev->cnf.forwarding ? idev->cnf.accept_ra == 2 :
-	    idev->cnf.accept_ra;
+	return READ_ONCE(idev->cnf.forwarding) ? accept_ra == 2 :
+		accept_ra;
 }
 
 #define IPV6_FRAG_HIGH_THRESH	(4 * 1024*1024)	/* 4194304 */

net/core/filter.c

@@ -5988,7 +5988,7 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 		return -ENODEV;
 
 	idev = __in6_dev_get_safely(dev);
-	if (unlikely(!idev || !idev->cnf.forwarding))
+	if (unlikely(!idev || !READ_ONCE(idev->cnf.forwarding)))
 		return BPF_FIB_LKUP_RET_FWD_DISABLED;
 
 	if (flags & BPF_FIB_LOOKUP_OUTPUT) {

net/ipv6/addrconf.c

@@ -551,7 +551,8 @@ static int inet6_netconf_fill_devconf(struct sk_buff *skb, int ifindex,
 		goto out;
 
 	if ((all || type == NETCONFA_FORWARDING) &&
-	    nla_put_s32(skb, NETCONFA_FORWARDING, devconf->forwarding) < 0)
+	    nla_put_s32(skb, NETCONFA_FORWARDING,
+			READ_ONCE(devconf->forwarding)) < 0)
 		goto nla_put_failure;
 #ifdef CONFIG_IPV6_MROUTE
 	if ((all || type == NETCONFA_MC_FORWARDING) &&
@@ -869,7 +870,8 @@ static void addrconf_forward_change(struct net *net, __s32 newf)
 		idev = __in6_dev_get(dev);
 		if (idev) {
 			int changed = (!idev->cnf.forwarding) ^ (!newf);
-			idev->cnf.forwarding = newf;
+
+			WRITE_ONCE(idev->cnf.forwarding, newf);
 			if (changed)
 				dev_forward_change(idev);
 		}
@@ -886,7 +888,7 @@ static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int newf)
 
 	net = (struct net *)table->extra2;
 	old = *p;
-	*p = newf;
+	WRITE_ONCE(*p, newf);
 
 	if (p == &net->ipv6.devconf_dflt->forwarding) {
 		if ((!newf) ^ (!old))
@@ -901,7 +903,7 @@ static int addrconf_fixup_forwarding(struct ctl_table *table, int *p, int newf)
 	if (p == &net->ipv6.devconf_all->forwarding) {
 		int old_dflt = net->ipv6.devconf_dflt->forwarding;
 
-		net->ipv6.devconf_dflt->forwarding = newf;
+		WRITE_ONCE(net->ipv6.devconf_dflt->forwarding, newf);
 		if ((!newf) ^ (!old_dflt))
 			inet6_netconf_notify_devconf(net, RTM_NEWNETCONF,
 						     NETCONFA_FORWARDING,

net/ipv6/ip6_output.c

@@ -501,7 +501,7 @@ int ip6_forward(struct sk_buff *skb)
 	u32 mtu;
 
 	idev = __in6_dev_get_safely(dev_get_by_index_rcu(net, IP6CB(skb)->iif));
-	if (net->ipv6.devconf_all->forwarding == 0)
+	if (READ_ONCE(net->ipv6.devconf_all->forwarding) == 0)
 		goto error;
 
 	if (skb->pkt_type != PACKET_HOST)

net/ipv6/ndisc.c

@@ -903,7 +903,7 @@ static enum skb_drop_reason ndisc_recv_ns(struct sk_buff *skb)
 		}
 
 		if (ipv6_chk_acast_addr(net, dev, &msg->target) ||
-		    (idev->cnf.forwarding &&
+		    (READ_ONCE(idev->cnf.forwarding) &&
 		     (net->ipv6.devconf_all->proxy_ndp || idev->cnf.proxy_ndp) &&
 		     (is_router = pndisc_is_router(&msg->target, dev)) >= 0)) {
 			if (!(NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED) &&
@@ -929,7 +929,7 @@ static enum skb_drop_reason ndisc_recv_ns(struct sk_buff *skb)
 	}
 
 	if (is_router < 0)
-		is_router = idev->cnf.forwarding;
+		is_router = READ_ONCE(idev->cnf.forwarding);
 
 	if (dad) {
 		ndisc_send_na(dev, &in6addr_linklocal_allnodes, &msg->target,
@@ -1080,7 +1080,7 @@ static enum skb_drop_reason ndisc_recv_na(struct sk_buff *skb)
 	 * Note that we don't do a (daddr == all-routers-mcast) check.
 	 */
 	new_state = msg->icmph.icmp6_solicited ? NUD_REACHABLE : NUD_STALE;
-	if (!neigh && lladdr && idev && idev->cnf.forwarding) {
+	if (!neigh && lladdr && idev && READ_ONCE(idev->cnf.forwarding)) {
 		if (accept_untracked_na(dev, saddr)) {
 			neigh = neigh_create(&nd_tbl, &msg->target, dev);
 			new_state = NUD_STALE;
@@ -1100,7 +1100,8 @@ static enum skb_drop_reason ndisc_recv_na(struct sk_buff *skb)
 		 * has already sent a NA to us.
 		 */
 		if (lladdr && !memcmp(lladdr, dev->dev_addr, dev->addr_len) &&
-		    net->ipv6.devconf_all->forwarding && net->ipv6.devconf_all->proxy_ndp &&
+		    READ_ONCE(net->ipv6.devconf_all->forwarding) &&
+		    net->ipv6.devconf_all->proxy_ndp &&
 		    pneigh_lookup(&nd_tbl, net, &msg->target, dev, 0)) {
 			/* XXX: idev->cnf.proxy_ndp */
 			goto out;
@@ -1148,7 +1149,7 @@ static enum skb_drop_reason ndisc_recv_rs(struct sk_buff *skb)
 	}
 
 	/* Don't accept RS if we're not in router mode */
-	if (!idev->cnf.forwarding)
+	if (!READ_ONCE(idev->cnf.forwarding))
 		goto out;
 
 	/*

net/ipv6/route.c

@@ -2220,7 +2220,7 @@ struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
 
 	strict |= flags & RT6_LOOKUP_F_IFACE;
 	strict |= flags & RT6_LOOKUP_F_IGNORE_LINKSTATE;
-	if (net->ipv6.devconf_all->forwarding == 0)
+	if (READ_ONCE(net->ipv6.devconf_all->forwarding) == 0)
 		strict |= RT6_LOOKUP_F_REACHABLE;
 
 	rcu_read_lock();
@@ -4149,7 +4149,7 @@ static void rt6_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_bu
 	in6_dev = __in6_dev_get(skb->dev);
 	if (!in6_dev)
 		return;
-	if (in6_dev->cnf.forwarding || !in6_dev->cnf.accept_redirects)
+	if (READ_ONCE(in6_dev->cnf.forwarding) || !in6_dev->cnf.accept_redirects)
 		return;
 
 	/* RFC2461 8.1: