ipv6: annotate data-races around idev->cnf.ignore_routes_with_linkdown

idev->cnf.ignore_routes_with_linkdown can be used without any locks,
add appropriate 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

include/net/addrconf.h

@@ -417,7 +417,7 @@ static inline bool ip6_ignore_linkdown(const struct net_device *dev)
 	if (unlikely(!idev))
 		return true;
 
-	return !!idev->cnf.ignore_routes_with_linkdown;
+	return !!READ_ONCE(idev->cnf.ignore_routes_with_linkdown);
 }
 
 void inet6_ifa_finish_destroy(struct inet6_ifaddr *ifp);

net/ipv6/addrconf.c

@@ -566,7 +566,7 @@ static int inet6_netconf_fill_devconf(struct sk_buff *skb, int ifindex,
 
 	if ((all || type == NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN) &&
 	    nla_put_s32(skb, NETCONFA_IGNORE_ROUTES_WITH_LINKDOWN,
-			devconf->ignore_routes_with_linkdown) < 0)
+			READ_ONCE(devconf->ignore_routes_with_linkdown)) < 0)
 		goto nla_put_failure;
 
 out:
@@ -935,7 +935,7 @@ static void addrconf_linkdown_change(struct net *net, __s32 newf)
 		if (idev) {
 			int changed = (!idev->cnf.ignore_routes_with_linkdown) ^ (!newf);
 
-			idev->cnf.ignore_routes_with_linkdown = newf;
+			WRITE_ONCE(idev->cnf.ignore_routes_with_linkdown, newf);
 			if (changed)
 				inet6_netconf_notify_devconf(dev_net(dev),
 							     RTM_NEWNETCONF,
@@ -956,7 +956,7 @@ static int addrconf_fixup_linkdown(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->ignore_routes_with_linkdown) {
 		if ((!newf) ^ (!old))
@@ -970,7 +970,7 @@ static int addrconf_fixup_linkdown(struct ctl_table *table, int *p, int newf)
 	}
 
 	if (p == &net->ipv6.devconf_all->ignore_routes_with_linkdown) {
-		net->ipv6.devconf_dflt->ignore_routes_with_linkdown = newf;
+		WRITE_ONCE(net->ipv6.devconf_dflt->ignore_routes_with_linkdown, newf);
 		addrconf_linkdown_change(net, newf);
 		if ((!newf) ^ (!old))
 			inet6_netconf_notify_devconf(net,