Re: [PATCH bpf-next] bpf: clear user buf when bpf_d_path failed

[Alexei Starovoitov]

On Thu, Jun 12, 2025 at 2:29 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Wed, Jun 11, 2025 at 8:49 AM Tao Chen <chen.dylane@xxxxxxxxx> wrote:
> >
> > The bpf_d_path() function may fail. If it does,
> > clear the user buf, like bpf_probe_read etc.
> >
>
> But that doesn't mean we *have to* do memset(0) for bpf_d_path(),
> though. Especially given that path buffer can be pretty large (4KB).
>
> Is there an issue you are trying to address with this, or is it more
> of a consistency clean up? Note, that more or less recently we made
> this zero filling behavior an option with an extra flag
> (BPF_F_PAD_ZEROS) for newer APIs. And if anything, bpf_d_path() is
> more akin to variable-sized string probing APIs rather than
> fixed-sized bpf_probe_read* family.

All old helpers had this BPF_F_PAD_ZEROS behavior
(or rather should have had).
So it makes sense to zero in this helper too for consistency.
I don't share performance concerns. This is an error path.