ipv6: annotate data-races in ndisc_router_discovery()

Annotate reads from in6_dev->cnf.XXX fields, as they could
change concurrently.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/ndisc.c

@@ -1319,7 +1319,7 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 	if (old_if_flags != in6_dev->if_flags)
 		send_ifinfo_notify = true;
 
-	if (!in6_dev->cnf.accept_ra_defrtr) {
+	if (!READ_ONCE(in6_dev->cnf.accept_ra_defrtr)) {
 		ND_PRINTK(2, info,
 			  "RA: %s, defrtr is false for dev: %s\n",
 			  __func__, skb->dev->name);
@@ -1327,7 +1327,8 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 	}
 
 	lifetime = ntohs(ra_msg->icmph.icmp6_rt_lifetime);
-	if (lifetime != 0 && lifetime < in6_dev->cnf.accept_ra_min_lft) {
+	if (lifetime != 0 &&
+	    lifetime < READ_ONCE(in6_dev->cnf.accept_ra_min_lft)) {
 		ND_PRINTK(2, info,
 			  "RA: router lifetime (%ds) is too short: %s\n",
 			  lifetime, skb->dev->name);
@@ -1338,7 +1339,7 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 	 * accept_ra_from_local is set to true.
 	 */
 	net = dev_net(in6_dev->dev);
-	if (!in6_dev->cnf.accept_ra_from_local &&
+	if (!READ_ONCE(in6_dev->cnf.accept_ra_from_local) &&
 	    ipv6_chk_addr(net, &ipv6_hdr(skb)->saddr, in6_dev->dev, 0)) {
 		ND_PRINTK(2, info,
 			  "RA from local address detected on dev: %s: default router ignored\n",
@@ -1350,7 +1351,7 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 	pref = ra_msg->icmph.icmp6_router_pref;
 	/* 10b is handled as if it were 00b (medium) */
 	if (pref == ICMPV6_ROUTER_PREF_INVALID ||
-	    !in6_dev->cnf.accept_ra_rtr_pref)
+	    !READ_ONCE(in6_dev->cnf.accept_ra_rtr_pref))
 		pref = ICMPV6_ROUTER_PREF_MEDIUM;
 #endif
 	/* routes added from RAs do not use nexthop objects */
@@ -1421,10 +1422,12 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 
 		spin_unlock_bh(&table->tb6_lock);
 	}
-	if (in6_dev->cnf.accept_ra_min_hop_limit < 256 &&
+	if (READ_ONCE(in6_dev->cnf.accept_ra_min_hop_limit) < 256 &&
 	    ra_msg->icmph.icmp6_hop_limit) {
-		if (in6_dev->cnf.accept_ra_min_hop_limit <= ra_msg->icmph.icmp6_hop_limit) {
-			WRITE_ONCE(in6_dev->cnf.hop_limit, ra_msg->icmph.icmp6_hop_limit);
+		if (READ_ONCE(in6_dev->cnf.accept_ra_min_hop_limit) <=
+		    ra_msg->icmph.icmp6_hop_limit) {
+			WRITE_ONCE(in6_dev->cnf.hop_limit,
+				   ra_msg->icmph.icmp6_hop_limit);
 			fib6_metric_set(rt, RTAX_HOPLIMIT,
 					ra_msg->icmph.icmp6_hop_limit);
 		} else {
@@ -1506,7 +1509,7 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 	}
 
 #ifdef CONFIG_IPV6_ROUTE_INFO
-	if (!in6_dev->cnf.accept_ra_from_local &&
+	if (!READ_ONCE(in6_dev->cnf.accept_ra_from_local) &&
 	    ipv6_chk_addr(dev_net(in6_dev->dev), &ipv6_hdr(skb)->saddr,
 			  in6_dev->dev, 0)) {
 		ND_PRINTK(2, info,
@@ -1515,7 +1518,7 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 		goto skip_routeinfo;
 	}
 
-	if (in6_dev->cnf.accept_ra_rtr_pref && ndopts.nd_opts_ri) {
+	if (READ_ONCE(in6_dev->cnf.accept_ra_rtr_pref) && ndopts.nd_opts_ri) {
 		struct nd_opt_hdr *p;
 		for (p = ndopts.nd_opts_ri;
 		     p;
@@ -1527,14 +1530,14 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 				continue;
 #endif
 			if (ri->prefix_len == 0 &&
-			    !in6_dev->cnf.accept_ra_defrtr)
+			    !READ_ONCE(in6_dev->cnf.accept_ra_defrtr))
 				continue;
 			if (ri->lifetime != 0 &&
-			    ntohl(ri->lifetime) < in6_dev->cnf.accept_ra_min_lft)
+			    ntohl(ri->lifetime) < READ_ONCE(in6_dev->cnf.accept_ra_min_lft))
 				continue;
-			if (ri->prefix_len < in6_dev->cnf.accept_ra_rt_info_min_plen)
+			if (ri->prefix_len < READ_ONCE(in6_dev->cnf.accept_ra_rt_info_min_plen))
 				continue;
-			if (ri->prefix_len > in6_dev->cnf.accept_ra_rt_info_max_plen)
+			if (ri->prefix_len > READ_ONCE(in6_dev->cnf.accept_ra_rt_info_max_plen))
 				continue;
 			rt6_route_rcv(skb->dev, (u8 *)p, (p->nd_opt_len) << 3,
 				      &ipv6_hdr(skb)->saddr);
@@ -1554,7 +1557,7 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 	}
 #endif
 
-	if (in6_dev->cnf.accept_ra_pinfo && ndopts.nd_opts_pi) {
+	if (READ_ONCE(in6_dev->cnf.accept_ra_pinfo) && ndopts.nd_opts_pi) {
 		struct nd_opt_hdr *p;
 		for (p = ndopts.nd_opts_pi;
 		     p;
@@ -1565,7 +1568,7 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 		}
 	}
 
-	if (ndopts.nd_opts_mtu && in6_dev->cnf.accept_ra_mtu) {
+	if (ndopts.nd_opts_mtu && READ_ONCE(in6_dev->cnf.accept_ra_mtu)) {
 		__be32 n;
 		u32 mtu;