Re: [PATCH bpf-next v3 1/2] bpf: Warn with bpf_unreachable() kfunc maybe due to uninitialized variable

[Yonghong Song <yonghong.song@linux.dev>]

On 5/20/25 2:46 AM, Alexei Starovoitov wrote:
> On Tue, May 20, 2025 at 11:39 AM Alexei Starovoitov
> <alexei.starovoitov@gmail.com> wrote:
>> So another idea...
>>
>> maybe we should remove special_kfunc_set instead?
>>
>> I recall we argued with Kumar years ago about it.
>> I don't remember why we kept it
>> and what purpose it serves now.
>>
>> What will break if we do:
>>
>> -               if (meta.btf == btf_vmlinux &&
>> btf_id_set_contains(&special_kfunc_set, meta.func_id)) {
>> +               if (meta.btf == btf_vmlinux) {
>>                          if (meta.func_id ==
>> special_kfunc_list[KF_bpf_obj_new_impl] ||
>>                              meta.func_id ==
>> special_kfunc_list[KF_bpf_percpu_obj_new_impl]) {
>>                                  struct btf_struct_meta *struct_meta;
>> @@ -13838,10 +13838,6 @@ static int check_kfunc_call(struct
>> bpf_verifier_env *env, struct bpf_insn *insn,
>>                                   * because packet slices are not refcounted (see
>>                                   * dynptr_type_refcounted)
>>                                   */
>> -                       } else {
>> -                               verbose(env, "kernel function %s
>> unhandled dynamic return type\n",
>> -                                       meta.func_name);
>> -                               return -EFAULT;
>>                          }
>>
>> ?
> Found old Kumar's reply:
> https://lore.kernel.org/bpf/20221120204625.ndtr7ygh7zgjxrsz@apollo/
>
> and my old reply:
> https://lore.kernel.org/bpf/20221120222922.udsuzkr5hcvjzot5@macbook-pro-5.dhcp.thefacebook.com/
>
> I think we need to remove special_kfunc_set,
> and then special_kfunc_list[] can stay as-is,
> and we can keep adding new kfuncs to it like bpf_unreachable in this case.

Okay, I will remove special_kfunc_set() then. Thanks!