ipv6: annotate data-races around devconf->disable_policy

idev->cnf.disable_policy and net->ipv6.devconf_all->disable_policy
can be read locklessly. Add appropriate annotations on reads
and writes.

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

net/ipv6/addrconf.c

@@ -6699,7 +6699,7 @@ int addrconf_disable_policy(struct ctl_table *ctl, int *valp, int val)
 	if (!rtnl_trylock())
 		return restart_syscall();
 
-	*valp = val;
+	WRITE_ONCE(*valp, val);
 
 	net = (struct net *)ctl->extra2;
 	if (valp == &net->ipv6.devconf_dflt->disable_policy) {

net/ipv6/ip6_output.c

@@ -513,8 +513,8 @@ int ip6_forward(struct sk_buff *skb)
 	if (skb_warn_if_lro(skb))
 		goto drop;
 
-	if (!net->ipv6.devconf_all->disable_policy &&
-	    (!idev || !idev->cnf.disable_policy) &&
+	if (!READ_ONCE(net->ipv6.devconf_all->disable_policy) &&
+	    (!idev || !READ_ONCE(idev->cnf.disable_policy)) &&
 	    !xfrm6_policy_check(NULL, XFRM_POLICY_FWD, skb)) {
 		__IP6_INC_STATS(net, idev, IPSTATS_MIB_INDISCARDS);
 		goto drop;

net/ipv6/route.c

@@ -4584,8 +4584,8 @@ struct fib6_info *addrconf_f6i_alloc(struct net *net,
 		f6i->dst_nocount = true;
 
 		if (!anycast &&
-		    (net->ipv6.devconf_all->disable_policy ||
-		     idev->cnf.disable_policy))
+		    (READ_ONCE(net->ipv6.devconf_all->disable_policy) ||
+		     READ_ONCE(idev->cnf.disable_policy)))
 			f6i->dst_nopolicy = true;
 	}