net: bridge: vlan: fix single net device option dumping

BugLink: https://bugs.launchpad.net/bugs/1959879
[ Upstream commit dcb2c5c6ca9b9177f04abaf76e5a983d177c9414 ]

When dumping vlan options for a single net device we send the same
entries infinitely because user-space expects a 0 return at the end but
we keep returning skb->len and restarting the dump on retry. Fix it by
returning the value from br_vlan_dump_dev() if it completed or there was
an error. The only case that must return skb->len is when the dump was
incomplete and needs to continue (-EMSGSIZE).

Reported-by: Benjamin Poirier <bpoirier@nvidia.com>
Fixes: 8dcea187088b ("net: bridge: vlan: add rtm definitions and dump support")
Signed-off-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 19f65ab91a0273a98766f0c325756407146b4ea5..06f5caee495aaf403e2af594cda0a51de3fb6970 100644 (file)
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -2105,7 +2105,8 @@ static int br_vlan_rtm_dump(struct sk_buff *skb, struct netlink_callback *cb)
                        goto out_err;
                }
                err = br_vlan_dump_dev(dev, skb, cb, dump_flags);
-               if (err && err != -EMSGSIZE)
+               /* if the dump completed without an error we return 0 here */
+               if (err != -EMSGSIZE)
                        goto out_err;
        } else {
                for_each_netdev_rcu(net, dev) {