Revert "mpls: no longer hold RTNL in mpls_netconf_dump_devconf()"

This reverts commit ff7abcc which is
commit e0f89d2 upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: Id07c86501f972e0126dec0edbce4a5888187546b
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: gregkh

net/mpls/af_mpls.c

@@ -1154,7 +1154,7 @@ static int mpls_netconf_fill_devconf(struct sk_buff *skb, struct mpls_dev *mdev,
 
 	if ((all || type == NETCONFA_INPUT) &&
 	    nla_put_s32(skb, NETCONFA_INPUT,
-			READ_ONCE(mdev->input_enabled)) < 0)
+			mdev->input_enabled) < 0)
 		goto nla_put_failure;
 
 	nlmsg_end(skb, nlh);
@@ -1303,12 +1303,11 @@ static int mpls_netconf_dump_devconf(struct sk_buff *skb,
 {
 	const struct nlmsghdr *nlh = cb->nlh;
 	struct net *net = sock_net(skb->sk);
-	struct {
-		unsigned long ifindex;
-	} *ctx = (void *)cb->ctx;
+	struct hlist_head *head;
 	struct net_device *dev;
 	struct mpls_dev *mdev;
-	int err = 0;
+	int idx, s_idx;
+	int h, s_h;
 
 	if (cb->strict_check) {
 		struct netlink_ext_ack *extack = cb->extack;
@@ -1325,23 +1324,40 @@ static int mpls_netconf_dump_devconf(struct sk_buff *skb,
 		}
 	}
 
-	rcu_read_lock();
-	for_each_netdev_dump(net, dev, ctx->ifindex) {
-		mdev = mpls_dev_get(dev);
-		if (!mdev)
-			continue;
-		err = mpls_netconf_fill_devconf(skb, mdev,
-						NETLINK_CB(cb->skb).portid,
-						nlh->nlmsg_seq,
-						RTM_NEWNETCONF,
-						NLM_F_MULTI,
-						NETCONFA_ALL);
-		if (err < 0)
-			break;
+	s_h = cb->args[0];
+	s_idx = idx = cb->args[1];
+
+	for (h = s_h; h < NETDEV_HASHENTRIES; h++, s_idx = 0) {
+		idx = 0;
+		head = &net->dev_index_head[h];
+		rcu_read_lock();
+		cb->seq = net->dev_base_seq;
+		hlist_for_each_entry_rcu(dev, head, index_hlist) {
+			if (idx < s_idx)
+				goto cont;
+			mdev = mpls_dev_get(dev);
+			if (!mdev)
+				goto cont;
+			if (mpls_netconf_fill_devconf(skb, mdev,
+						      NETLINK_CB(cb->skb).portid,
+						      nlh->nlmsg_seq,
+						      RTM_NEWNETCONF,
+						      NLM_F_MULTI,
+						      NETCONFA_ALL) < 0) {
+				rcu_read_unlock();
+				goto done;
+			}
+			nl_dump_check_consistent(cb, nlmsg_hdr(skb));
+cont:
+			idx++;
+		}
+		rcu_read_unlock();
 	}
-	rcu_read_unlock();
+done:
+	cb->args[0] = h;
+	cb->args[1] = idx;
 
-	return err;
+	return skb->len;
 }
 
 #define MPLS_PERDEV_SYSCTL_OFFSET(field)	\
@@ -2755,8 +2771,7 @@ static int __init mpls_init(void)
 			     mpls_getroute, mpls_dump_routes, 0);
 	rtnl_register_module(THIS_MODULE, PF_MPLS, RTM_GETNETCONF,
 			     mpls_netconf_get_devconf,
-			     mpls_netconf_dump_devconf,
-			     RTNL_FLAG_DUMP_UNLOCKED);
+			     mpls_netconf_dump_devconf, 0);
 	err = ipgre_tunnel_encap_add_mpls_ops();
 	if (err)
 		pr_err("Can't add mpls over gre tunnel ops\n");