ipv6: lockless IPV6_ROUTER_ALERT_ISOLATE implementation

Reads from np->rtalert_isolate are racy.

Move this flag to inet->inet_flags to fix data-races.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/ipv6.h

@@ -246,11 +246,10 @@ struct ipv6_pinfo {
 	__u16			sndflow:1,
 				pmtudisc:3,
 				padding:1,	/* 1 bit hole */
-				srcprefs:3,	/* 001: prefer temporary address
+				srcprefs:3;	/* 001: prefer temporary address
 						 * 010: prefer public address
 						 * 100: prefer care-of address
 						 */
-				rtalert_isolate:1;
 	__u8			min_hopcount;
 	__u8			tclass;
 	__be32			rcv_flowinfo;

include/net/inet_sock.h

@@ -276,6 +276,7 @@ enum {
 	INET_FLAGS_DONTFRAG	= 25,
 	INET_FLAGS_RECVERR6	= 26,
 	INET_FLAGS_REPFLOW	= 27,
+	INET_FLAGS_RTALERT_ISOLATE = 28,
 };
 
 /* cmsg flags for inet */

net/ipv6/ip6_output.c

@@ -368,9 +368,8 @@ static int ip6_call_ra_chain(struct sk_buff *skb, int sel)
 		if (sk && ra->sel == sel &&
 		    (!sk->sk_bound_dev_if ||
 		     sk->sk_bound_dev_if == skb->dev->ifindex)) {
-			struct ipv6_pinfo *np = inet6_sk(sk);
 
-			if (np && np->rtalert_isolate &&
+			if (inet6_test_bit(RTALERT_ISOLATE, sk) &&
 			    !net_eq(sock_net(sk), dev_net(skb->dev))) {
 				continue;
 			}

net/ipv6/ipv6_sockglue.c

@@ -488,6 +488,11 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 		if (!val)
 			skb_errqueue_purge(&sk->sk_error_queue);
 		return 0;
+	case IPV6_ROUTER_ALERT_ISOLATE:
+		if (optlen < sizeof(int))
+			return -EINVAL;
+		inet6_assign_bit(RTALERT_ISOLATE, sk, valbool);
+		return 0;
 	}
 	if (needs_rtnl)
 		rtnl_lock();
@@ -936,12 +941,6 @@ int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 			goto e_inval;
 		retv = ip6_ra_control(sk, val);
 		break;
-	case IPV6_ROUTER_ALERT_ISOLATE:
-		if (optlen < sizeof(int))
-			goto e_inval;
-		np->rtalert_isolate = valbool;
-		retv = 0;
-		break;
 	case IPV6_MTU_DISCOVER:
 		if (optlen < sizeof(int))
 			goto e_inval;
@@ -1452,7 +1451,7 @@ int do_ipv6_getsockopt(struct sock *sk, int level, int optname,
 		break;
 
 	case IPV6_ROUTER_ALERT_ISOLATE:
-		val = np->rtalert_isolate;
+		val = inet6_test_bit(RTALERT_ISOLATE, sk);
 		break;
 
 	case IPV6_RECVERR_RFC4884: