Merge branch 'ipv6-route-rcu'

Paolo Abeni says:

====================
ipv6: route: enforce RCU protection for fib6_info->from

This series addresses a couple of RCU left-over dating back to rt6_info->from
conversion to RCU

v1 -> v2:
 - fix a possible race in patch 1
====================

Signed-off-by: David S. Miller <[email protected]>

Author: davem330

net/ipv6/route.c

@@ -1599,15 +1599,15 @@ static int rt6_remove_exception_rt(struct rt6_info *rt)
 static void rt6_update_exception_stamp_rt(struct rt6_info *rt)
 {
 	struct rt6_exception_bucket *bucket;
-	struct fib6_info *from = rt->from;
 	struct in6_addr *src_key = NULL;
 	struct rt6_exception *rt6_ex;
-
-	if (!from ||
-	    !(rt->rt6i_flags & RTF_CACHE))
-		return;
+	struct fib6_info *from;
 
 	rcu_read_lock();
+	from = rcu_dereference(rt->from);
+	if (!from || !(rt->rt6i_flags & RTF_CACHE))
+		goto unlock;
+
 	bucket = rcu_dereference(from->rt6i_exception_bucket);
 
 #ifdef CONFIG_IPV6_SUBTREES
@@ -1626,6 +1626,7 @@ static void rt6_update_exception_stamp_rt(struct rt6_info *rt)
 	if (rt6_ex)
 		rt6_ex->stamp = jiffies;
 
+unlock:
 	rcu_read_unlock();
 }
 
@@ -2742,20 +2743,24 @@ static int ip6_route_check_nh_onlink(struct net *net,
 	u32 tbid = l3mdev_fib_table(dev) ? : RT_TABLE_MAIN;
 	const struct in6_addr *gw_addr = &cfg->fc_gateway;
 	u32 flags = RTF_LOCAL | RTF_ANYCAST | RTF_REJECT;
+	struct fib6_info *from;
 	struct rt6_info *grt;
 	int err;
 
 	err = 0;
 	grt = ip6_nh_lookup_table(net, cfg, gw_addr, tbid, 0);
 	if (grt) {
+		rcu_read_lock();
+		from = rcu_dereference(grt->from);
 		if (!grt->dst.error &&
 		    /* ignore match if it is the default route */
-		    grt->from && !ipv6_addr_any(&grt->from->fib6_dst.addr) &&
+		    from && !ipv6_addr_any(&from->fib6_dst.addr) &&
 		    (grt->rt6i_flags & flags || dev != grt->dst.dev)) {
 			NL_SET_ERR_MSG(extack,
 				       "Nexthop has invalid gateway or device mismatch");
 			err = -EINVAL;
 		}
+		rcu_read_unlock();
 
 		ip6_rt_put(grt);
 	}