net: ndo_fdb_dump should report -EMSGSIZE to rtnl_fdb_dump.

When the send skbuff reaches the end, nlmsg_put and friends returns
-EMSGSIZE but it is silently thrown away in ndo_fdb_dump. It is called
within a for_each_netdev loop and the first fdb entry of a following
netdev could fit in the remaining skbuff.  This breaks the mechanism
of cb->args[0] and idx to keep track of the entries that are already
dumped, which results missing entries in bridge fdb show command.

Signed-off-by: Minoura Makoto <minoura@valinux.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index d735e854f916..8261d95dd846 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2911,6 +2911,7 @@ int ndo_dflt_fdb_dump(struct sk_buff *skb,
 	nlmsg_populate_fdb(skb, cb, dev, &idx, &dev->mc);
 out:
 	netif_addr_unlock_bh(dev);
+	cb->args[1] = err;
 	return idx;
 }
 EXPORT_SYMBOL(ndo_dflt_fdb_dump);
@@ -2944,6 +2945,7 @@ static int rtnl_fdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
 		ops = br_dev->netdev_ops;
 	}
 
+	cb->args[1] = 0;
 	for_each_netdev(net, dev) {
 		if (brport_idx && (dev->ifindex != brport_idx))
 			continue;
@@ -2971,12 +2973,16 @@ static int rtnl_fdb_dump(struct sk_buff *skb, struct netlink_callback *cb)
 				idx = cops->ndo_fdb_dump(skb, cb, br_dev, dev,
 							 idx);
 		}
+		if (cb->args[1] == -EMSGSIZE)
+			break;
 
 		if (dev->netdev_ops->ndo_fdb_dump)
 			idx = dev->netdev_ops->ndo_fdb_dump(skb, cb, dev, NULL,
 							    idx);
 		else
 			idx = ndo_dflt_fdb_dump(skb, cb, dev, NULL, idx);
+		if (cb->args[1] == -EMSGSIZE)
+			break;
 
 		cops = NULL;
 	}