net: dst: annotate data-races around dst->obsolete

(dst_entry)->obsolete is read locklessly, add corresponding
annotations.

Signed-off-by: Eric Dumazet <[e-mail]>
Reviewed-by: Kuniyuki Iwashima <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

include/net/dst.h

···
 							   u32));
 static inline struct dst_entry *dst_check(struct dst_entry *dst, u32 cookie)
 {
-	if (dst->obsolete)
+	if (READ_ONCE(dst->obsolete))
 		dst = INDIRECT_CALL_INET(dst->ops->check, ip6_dst_check,
 					 ipv4_dst_check, dst, cookie);
 	return dst;

net/core/dst.c

···
 {
 	struct net_device *dev = dst->dev;
 
-	dst->obsolete = DST_OBSOLETE_DEAD;
+	WRITE_ONCE(dst->obsolete, DST_OBSOLETE_DEAD);
 	if (dst->ops->ifdown)
 		dst->ops->ifdown(dst, dev);
 	dst->input = dst_discard;

net/core/dst_cache.c

···
 
 	if (unlikely(!time_after(idst->refresh_ts,
 				 READ_ONCE(dst_cache->reset_ts)) ||
-		     (dst->obsolete && !dst->ops->check(dst, idst->cookie)))) {
+		     (READ_ONCE(dst->obsolete) && !dst->ops->check(dst, idst->cookie)))) {
 		dst_cache_per_cpu_dst_set(idst, NULL, 0);
 		dst_release(dst);
 		goto fail;

net/core/neighbour.c

···
 			 * we can reinject the packet there.
 			 */
 			n2 = NULL;
-			if (dst && dst->obsolete != DST_OBSOLETE_DEAD) {
+			if (dst &&
+			    READ_ONCE(dst->obsolete) != DST_OBSOLETE_DEAD) {
 				n2 = dst_neigh_lookup_skb(dst, skb);
 				if (n2)
 					n1 = n2;

net/core/sock.c

···
 {
 	struct dst_entry *dst = __sk_dst_get(sk);
 
-	if (dst && dst->obsolete &&
+	if (dst && READ_ONCE(dst->obsolete) &&
 	    INDIRECT_CALL_INET(dst->ops->check, ip6_dst_check, ipv4_dst_check,
 			       dst, cookie) == NULL) {
 		sk_tx_queue_clear(sk);
···
 {
 	struct dst_entry *dst = sk_dst_get(sk);
 
-	if (dst && dst->obsolete &&
+	if (dst && READ_ONCE(dst->obsolete) &&
 	    INDIRECT_CALL_INET(dst->ops->check, ip6_dst_check, ipv4_dst_check,
 			       dst, cookie) == NULL) {
 		sk_dst_reset(sk);

net/ipv4/datagram.c

···
 	rcu_read_lock();
 
 	dst = __sk_dst_get(sk);
-	if (!dst || !dst->obsolete || dst->ops->check(dst, 0)) {
+	if (!dst || !READ_ONCE(dst->obsolete) || dst->ops->check(dst, 0)) {
 		rcu_read_unlock();
 		return;
 	}

net/ipv4/route.c

···
 		 */
 		rt = rcu_dereference(nhc->nhc_rth_input);
 		if (rt)
-			rt->dst.obsolete = DST_OBSOLETE_KILL;
+			WRITE_ONCE(rt->dst.obsolete, DST_OBSOLETE_KILL);
 
 		for_each_possible_cpu(i) {
 			struct rtable __rcu **prt;
···
 			prt = per_cpu_ptr(nhc->nhc_pcpu_rth_output, i);
 			rt = rcu_dereference(*prt);
 			if (rt)
-				rt->dst.obsolete = DST_OBSOLETE_KILL;
+				WRITE_ONCE(rt->dst.obsolete, DST_OBSOLETE_KILL);
 		}
 	}
 
···
 						jiffies + ip_rt_gc_timeout);
 			}
 			if (kill_route)
-				rt->dst.obsolete = DST_OBSOLETE_KILL;
+				WRITE_ONCE(rt->dst.obsolete, DST_OBSOLETE_KILL);
 			call_netevent_notifiers(NETEVENT_NEIGH_UPDATE, n);
 		}
 		neigh_release(n);
···
 {
 	struct rtable *rt = dst_rtable(dst);
 
-	if ((dst->obsolete > 0) ||
+	if ((READ_ONCE(dst->obsolete) > 0) ||
 	    (rt->rt_flags & RTCF_REDIRECTED) ||
 	    rt->dst.expires)
 		sk_dst_reset(sk);
···
 	__build_flow_key(net, &fl4, sk, iph, 0, 0, 0, 0, 0);
 
 	rt = dst_rtable(odst);
-	if (odst->obsolete && !odst->ops->check(odst, 0)) {
+	if (READ_ONCE(odst->obsolete) && !odst->ops->check(odst, 0)) {
 		rt = ip_route_output_flow(sock_net(sk), &fl4, sk);
 		if (IS_ERR(rt))
 			goto out;
···
 	 * this is indicated by setting obsolete to DST_OBSOLETE_KILL or
 	 * DST_OBSOLETE_DEAD.
 	 */
-	if (dst->obsolete != DST_OBSOLETE_FORCE_CHK || rt_is_expired(rt))
+	if (READ_ONCE(dst->obsolete) != DST_OBSOLETE_FORCE_CHK ||
+	    rt_is_expired(rt))
 		return NULL;
 	return dst;
 }
···
 static bool rt_cache_valid(const struct rtable *rt)
 {
 	return	rt &&
-		rt->dst.obsolete == DST_OBSOLETE_FORCE_CHK &&
+		READ_ONCE(rt->dst.obsolete) == DST_OBSOLETE_FORCE_CHK &&
 		!rt_is_expired(rt);
 }
 

net/ipv6/datagram.c

···
 
 	rcu_read_lock();
 	dst = __sk_dst_get(sk);
-	if (!dst || !dst->obsolete ||
+	if (!dst || !READ_ONCE(dst->obsolete) ||
 	    dst->ops->check(dst, inet6_sk(sk)->dst_cookie)) {
 		rcu_read_unlock();
 		return;

net/ipv6/route.c

···
 		if (time_after(jiffies, rt->dst.expires))
 			return true;
 	} else if (from) {
-		return rt->dst.obsolete != DST_OBSOLETE_FORCE_CHK ||
+		return READ_ONCE(rt->dst.obsolete) != DST_OBSOLETE_FORCE_CHK ||
 			fib6_check_expired(from);
 	}
 	return false;
···
 					    u32 cookie)
 {
 	if (!__rt6_check_expired(rt) &&
-	    rt->dst.obsolete == DST_OBSOLETE_FORCE_CHK &&
+	    READ_ONCE(rt->dst.obsolete) == DST_OBSOLETE_FORCE_CHK &&
 	    fib6_check(from, cookie))
 		return &rt->dst;
-	else
-		return NULL;
+	return NULL;
 }
 
 INDIRECT_CALLABLE_SCOPE struct dst_entry *ip6_dst_check(struct dst_entry *dst,
···
 			sk_uid(sk));
 
 	dst = __sk_dst_get(sk);
-	if (!dst || !dst->obsolete ||
+	if (!dst || !READ_ONCE(dst->obsolete) ||
 	    dst->ops->check(dst, inet6_sk(sk)->dst_cookie))
 		return;
 

net/netfilter/ipvs/ip_vs_xmit.c

···
 	if (!dest_dst)
 		return NULL;
 	dst = dest_dst->dst_cache;
-	if (dst->obsolete &&
+	if (READ_ONCE(dst->obsolete) &&
 	    dst->ops->check(dst, dest_dst->dst_cookie) == NULL)
 		return NULL;
 	return dest_dst;

net/sctp/transport.c

···
 void sctp_transport_pmtu(struct sctp_transport *transport, struct sock *sk)
 {
 	/* If we don't have a fresh route, look one up */
-	if (!transport->dst || transport->dst->obsolete) {
+	if (!transport->dst || READ_ONCE(transport->dst->obsolete)) {
 		sctp_transport_dst_release(transport);
 		transport->af_specific->get_dst(transport, &transport->saddr,
 						&transport->fl, sk);

net/xfrm/xfrm_policy.c

···
 	 * This will force stale_bundle() to fail on any xdst bundle with
 	 * this dst linked in it.
 	 */
-	if (dst->obsolete < 0 && !stale_bundle(dst))
+	if (READ_ONCE(dst->obsolete) < 0 && !stale_bundle(dst))
 		return dst;
 
 	return NULL;
···
 
 static void xfrm_negative_advice(struct sock *sk, struct dst_entry *dst)
 {
-	if (dst->obsolete)
+	if (READ_ONCE(dst->obsolete))
 		sk_dst_reset(sk);
 }