On Tue, Jun 23, 2020 at 09:33 PM CEST, Martin KaFai Lau wrote:
> On Tue, Jun 23, 2020 at 12:34:58PM +0200, Jakub Sitnicki wrote:
>
> [ ... ]
>
>> @@ -93,8 +108,16 @@ static int bpf_netns_link_update_prog(struct bpf_link *link,
>> goto out_unlock;
>> }
>>
>> + run_array = rcu_dereference_protected(net->bpf.run_array[type],
>> + lockdep_is_held(&netns_bpf_mutex));
>> + if (run_array)
>> + ret = bpf_prog_array_replace_item(run_array, link->prog, new_prog);
>> + else
> When will this happen?
This will never happen, unless there is a bug. As long as there is a
link attached, run_array should never be detached (null). Because it can
be handled gracefully, we fail the bpf(LINK_UPDATE) syscall.
Your question makes me think that perhaps it should trigger a warning,
with WARN_ON_ONCE, to signal clearly to the reader that this is an
unexpected state.
WDYT?
>
>> + ret = -ENOENT;
>> + if (ret)
>> + goto out_unlock;
>> +
>> old_prog = xchg(&link->prog, new_prog);
>> - rcu_assign_pointer(net->bpf.progs[type], new_prog);
>> bpf_prog_put(old_prog);
>>
>> out_unlock:
>> @@ -142,14 +165,38 @@ static const struct bpf_link_ops bpf_netns_link_ops = {
>> .show_fdinfo = bpf_netns_link_show_fdinfo,
>> };
