Re: [RFC PATCH bpf-next 2/2] bpf: Get fentry func addr from user when BTF info invalid

[Tao Chen <chen.dylane@linux.dev>]

在 2025/5/1 06:23, Alexei Starovoitov 写道:
> On Wed, Apr 30, 2025 at 10:57 AM Alan Maguire <alan.maguire@oracle.com> wrote:
>>> +
>>> +                     if (!addr && (prog->expected_attach_type == BPF_TRACE_FENTRY ||
>>> +                                     prog->expected_attach_type == BPF_TRACE_FEXIT)) {
>>> +                             fname = kallsyms_lookup((unsigned long)prog->aux->fentry_func,
>>> +                                                     NULL, NULL, NULL, trace_symbol);
>>> +                             if (fname)
>>> +                                     addr = (long)prog->aux->fentry_func;
>>
>>
>> We should do some validation that the fname we get back matches the BTF
>> func name prefix (fname "foo.isra.0" matches "foo") I think?
> 
> I don't think that will be enough.
> User space should not be able to pass a random kernel address
> and convince the kernel that it matches a particular btf_id.
> As discussed in the other thread matching based on name is
> breaking apart.
> pahole does all the safety check to make sure name/addr/btf_id
> are consistent.
> We shouldn't be adding workarounds like this because
> pahole/btf/kernel build is not smart enough.
> 

Got it thanks for your reply, it is hoped that pahole/btf can have a 
better way to solve such problems.

> pw-bot: cr


-- 
Best Regards
Tao Chen