Re: [PATCH] libbpf:fix use empty function pointers in ringbuf_poll

[Stanislav Fomichev]

On Thu, Jun 8, 2023 at 6:00 AM zhangmingyi <zhangmingyi5@xxxxxxxxxx> wrote:
>
> On 06/06,Stanislav Fomichev wrote:
>
> > On 06/05, Xin Liu wrote:
> > > From: zhangmingyi <zhangmingyi5@xxxxxxxxxx>
> >
> > > The sample_cb of the ring_buffer__new interface can transfer NULL. However,
> > > the system does not check whether sample_cb is NULL during
> > > ring_buffer__poll, null pointer is used.
>
> > What is the point of calling ring_buffer__new with sample_cb == NULL?
>
> Yes, as you said, passing sample_cb in ring_buffer__new to NULL doesn't
> make sense, and few people use it that way, but that doesn't prevent this
> from being a allowed and supported scenario. And when ring_buffer__poll is
> called, it leads to a segmentation fault (core dump), which I think needs
> to be fixed to ensure the security quality of libbpf.

I dunno. I'd argue that passing a NULL to ring_buffer__new is an API
misuse. Maybe ring_buffer__new should return -EINVAL instead when
passed NULL sample_cb? Although, we don't usually have those checks
for the majority of the arguments in libbpf...