1 files changed, 31 insertions, 25 deletions

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 390f4be7f..c484b1c0f 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -916,7 +916,8 @@ int ip_valid_fib_dump_req(struct net *net, const struct nlmsghdr *nlh,
 	struct rtmsg *rtm;
 	int err, i;
 
-	ASSERT_RTNL();
+	if (filter->rtnl_held)
+		ASSERT_RTNL();
 
 	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*rtm))) {
 		NL_SET_ERR_MSG(extack, "Invalid header for FIB dump request");
@@ -961,7 +962,10 @@ int ip_valid_fib_dump_req(struct net *net, const struct nlmsghdr *nlh,
 			break;
 		case RTA_OIF:
 			ifindex = nla_get_u32(tb[i]);
-			filter->dev = __dev_get_by_index(net, ifindex);
+			if (filter->rtnl_held)
+				filter->dev = __dev_get_by_index(net, ifindex);
+			else
+				filter->dev = dev_get_by_index_rcu(net, ifindex);
 			if (!filter->dev)
 				return -ENODEV;
 			break;
@@ -983,20 +987,24 @@ EXPORT_SYMBOL_GPL(ip_valid_fib_dump_req);
 
 static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 {
-	struct fib_dump_filter filter = { .dump_routes = true,
-					  .dump_exceptions = true };
+	struct fib_dump_filter filter = {
+		.dump_routes = true,
+		.dump_exceptions = true,
+		.rtnl_held = false,
+	};
 	const struct nlmsghdr *nlh = cb->nlh;
 	struct net *net = sock_net(skb->sk);
 	unsigned int h, s_h;
 	unsigned int e = 0, s_e;
 	struct fib_table *tb;
 	struct hlist_head *head;
-	int dumped = 0, err;
+	int dumped = 0, err = 0;
 
+	rcu_read_lock();
 	if (cb->strict_check) {
 		err = ip_valid_fib_dump_req(net, nlh, &filter, cb);
 		if (err < 0)
-			return err;
+			goto unlock;
 	} else if (nlmsg_len(nlh) >= sizeof(struct rtmsg)) {
 		struct rtmsg *rtm = nlmsg_data(nlh);
 
@@ -1005,29 +1013,26 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 
 	/* ipv4 does not use prefix flag */
 	if (filter.flags & RTM_F_PREFIX)
-		return skb->len;
+		goto unlock;
 
 	if (filter.table_id) {
 		tb = fib_get_table(net, filter.table_id);
 		if (!tb) {
 			if (rtnl_msg_family(cb->nlh) != PF_INET)
-				return skb->len;
+				goto unlock;
 
 			NL_SET_ERR_MSG(cb->extack, "ipv4: FIB table does not exist");
-			return -ENOENT;
+			err = -ENOENT;
+			goto unlock;
 		}
-
-		rcu_read_lock();
 		err = fib_table_dump(tb, skb, cb, &filter);
-		rcu_read_unlock();
-		return skb->len ? : err;
+		goto unlock;
 	}
 
 	s_h = cb->args[0];
 	s_e = cb->args[1];
 
-	rcu_read_lock();
-
+	err = 0;
 	for (h = s_h; h < FIB_TABLE_HASHSZ; h++, s_e = 0) {
 		e = 0;
 		head = &net->ipv4.fib_table_hash[h];
@@ -1038,25 +1043,25 @@ static int inet_dump_fib(struct sk_buff *skb, struct netlink_callback *cb)
 				memset(&cb->args[2], 0, sizeof(cb->args) -
 						 2 * sizeof(cb->args[0]));
 			err = fib_table_dump(tb, skb, cb, &filter);
-			if (err < 0) {
-				if (likely(skb->len))
-					goto out;
-
-				goto out_err;
-			}
+			if (err < 0)
+				goto out;
 			dumped = 1;
 next:
 			e++;
 		}
 	}
-out:
+
+	/* Don't let NLM_DONE coalesce into a message, even if it could.
+	 * Some user space expects NLM_DONE in a separate recv().
+	 */
 	err = skb->len;
-out_err:
-	rcu_read_unlock();
+out:
 
 	cb->args[1] = e;
 	cb->args[0] = h;
 
+unlock:
+	rcu_read_unlock();
 	return err;
 }
 
@@ -1659,5 +1664,6 @@ void __init ip_fib_init(void)
 
 	rtnl_register(PF_INET, RTM_NEWROUTE, inet_rtm_newroute, NULL, 0);
 	rtnl_register(PF_INET, RTM_DELROUTE, inet_rtm_delroute, NULL, 0);
-	rtnl_register(PF_INET, RTM_GETROUTE, NULL, inet_dump_fib, 0);
+	rtnl_register(PF_INET, RTM_GETROUTE, NULL, inet_dump_fib,
+		      RTNL_FLAG_DUMP_UNLOCKED);
 }