Jia-Ju Bai [off-list ref] wrote:

When find_table_lock() returns NULL to t, no error return code of
do_update_counters() is assigned.

Its -ENOENT.

 	t = find_table_lock(net, name, &ret, &ebt_mutex);

                                       ^^^^^

ret is passed to find_table_lock, which passes it to
find_inlist_lock_noload() which will set *ret = -ENOENT
for NULL case.