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, 4 insertions, 1 deletions

diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
index 47f7da58a7f0..8b5833c1ff2e 100644
--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -1093,8 +1093,11 @@ int switchdev_port_fdb_dump(struct sk_buff *skb, struct netlink_callback *cb,
                 .cb = cb,
                 .idx = idx,
         };
+        int err;
 
-        switchdev_port_obj_dump(dev, &dump.fdb.obj, switchdev_port_fdb_dump_cb);
+        err = switchdev_port_obj_dump(dev, &dump.fdb.obj,
+                                      switchdev_port_fdb_dump_cb);
+        cb->args[1] = err;
         return dump.idx;
 }
 EXPORT_SYMBOL_GPL(switchdev_port_fdb_dump);